M.P.1 notes

LAB MANUAL
MANUFACTURING PROCESS - I (PE - 217)
(SAND TESTING & WELDING LAB PRACTICALS)
B. TECH. -3rd SEMESTER
MECHANICAL ENGINEERING DEPARTMENT
Prepared by: Rajesh Kumar Reviewed by: Harlal Singh Mali Approved By: Harlal S. Mali
& Asst. Prof Asst. Prof.
HPS
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Manufacturing Processes Lab - I
PE - 217 Practical
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LIST OF EXPERIMENTS IN SAND TESTING LAB
Sr. No.
Name of Experiment
1
To study ingredients of molding sand and core sand.
2
To determine clay content in a moulding sand sam-ple.
3
To determine moisture content in a moulding sand sample.
4
To conduct hardness test for mould and core.
5
To test tensile, compressive, transverse strength of moulding sand in dry condition.
6
Determination of permeability number of a molding sand sample.
7
Measurement of grain finances number.
8
To study various features of cupola furnace and its charges calculations.
9
Prepare a green sand mould for any stable engi-neering component.
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EXPERIMENT-1
Objective:- To study ingredients of molding sand and core sand
Theory:-
Ingredients of molding sand: - The main constituents of molding sand are as under: -
(i) Silica Sand
(ii) Binders
(iii)Additives
(iv) Water
(i) Silica Sand: - Silica is usually the main constituent of all the sands irrespective of their colors and the source of availability. Sources of sand are river beds, sea, lakes and desert. Silica sand can maintain their shape and other characteristics even at very high temperature while they are in contact with molten metals. Besides it can be used repeatedly for making moulds. How-ever silica sand has the disadvantages of high thermal expansion or volume at 5720 C
(ii) Binders: - Silica sand does not possess clay and need addition of a suitable binder to make them usable for foundry work. The purpose of adding a binder to the moulding sand is to impart it sufficient strength and cohesiveness so as to enable it to retain its shape after the mould has been rammed and the pattern withdrawn. However, it produces a diverse effect on the per-meability of the sand mould. The common binders used in foundry can be grouped as:
• Organic Binder
• Inorganic Binders
(a) Organic Binders:- The common binders coming this category are
a. Dextrain
b. Molasses
c. Linseed oil
d. Cereal binders
e. Pitch (2% max.)
f. Resin
(b) Inorganic Binders:- The common binders are sodium silicate, Portland ce-ment and clay binders are mostly used for moulding sand. Clay binder can be classified as-
(i) Fire clay
(ii) Bentonite
(iii) Kaolonite
(iv) Limonite
(v) Fuller’s earth
(iii)Additive:- Additive are those materials which are added to the moulding sand to im-prove upon some of its existing properties or to impart certain new properties to it. The com-monly used additives are:
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Manufacturing Processes Lab - I
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a.) Coal Dust – It is mainly used in the sand used for grey iron and malleable iron. Its main purpose is to react chemically with the oxygen present in the sand pores and thus produces a reducing atmosphere at mould metal interface and prevent oxidation of the metal. It is added to 1 to 10%.
b.) Sea Coal- It is used in sands used for grey and malleable iron casting. It restricts the mould wall movement and improves surface finish. It reduces permeability and not strength of the mould. It is added 2 to 8 % in the sand.
c.) Cereals or cornflour- It promotes mould wall movement by using volatized by heat, reduces expansion defects, improper strength, toughness of the sand and decreases permeability and flow ability. It is added 0.25 to 2 %.
d.) Silica Flour- It increases hot strength, decreases metal penetration into the mould, reduces expansion defects and improve surface finish and thermal ability. It may be added up to 35%.
e.) Wood Flour- They minimize the sand expansion defects. They improve collapsi-bility and surface finish and flow ability. They may be added up to .5 to 2 % to sand.
f.) Dextrain and Molasses- They increase dry strength of the sand. They add to edge hardness of moulds and they resist the mould tendency to drying out.
g.) Fuel Oil- It appears to improve mould ability of sand. It may be added .01 to .10%.
h.) Pitch- It improves hot strength and surface finish. It is added up to 2%.
(iv) Water:- The clay content added to the foundry sand will not give the required strength until a suitable quantity of water is added to it. The amount of water is added from 2 to 8 %. The water content present in the sand mass is partly in mixed from called pore water and partly in the free state known as free water. When water is added it starts filling into the pores of the clay where it forms a sort of micro- film. This water content is held rigidly by the clay and it is mainly responsible for enabling the clay to impart the desired strength to the sand. When more water is added to the clay mixture than the amount required as pore water, it remains as a fluid and is held between the clay particle separating them. It has been found that this excess amount of free water behaves as a lubricant and thus improves the mould ability and possibility of the moulding sand. It however reduces the strength of the mixture and thus weakness the mould.
Ingredients of Core Sand:- A core may be defined as any projection into the mould and made up of core sand. The main constituents of the core sand are as-
1) Granular Refractory 2) Core Binder
3) Water 4) Special Additive
1) Granular Refractory- Silica is the most widely used core base sand. Because of their higher melting point and vibrated bulk density, zircon and olivine in certain cases are prepared over silica sand for making core carbon and chamotte are used for core sand. Coarse silica sand of high refractoriness is employed for making cores in steel foundries. Finer bank and lake sands are preferred for making cores in cast iron foundries. Coarser and finer sands may sometimes be mixed for making cores. This mixing increases size distribution and strength, but permeability gets reduced.
2) Core Binders- These are (a) Organic (b) Inorganic and (c) Others.
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(a) Organic Binders:-
(i) Core Oil- these are linseed oil whale oil and mineral oils. Core oil contents may vary from 0.5 to 3 % by weight.
(ii) Cereal Binders- These are gelatinized starch and gelatinized corn flour. Cereal bind-ers contribute to green strength. Its percentage is 0.5 to 2 % to give compression strength .07 to .16 Kg/cm2.
(iii) Water Soluble Binder- These are dextrin and molasses. These resists core staging during handling and increased moisture contents develops higher tensile strength, baked scratch and edge hardness.
(iv) Wood Product Binders- Natural resins and sulfite binders. These are used up to 1.5% in green sand and dry sand core.
(v) Pitch- It is a coal – Tar product. It may be added up to 3% or more. It increases hot strength.
(vi) Wood Flour- It is added 1 % to or less to decrease veining and to increase collapsi-bility of cores and flow ability of sand.
(vii) Protein Binders- They is casein and glue. They contain nitrogen harden by baking.
(b) Inorganic Binders:-These are
(i) Fire clay (ii) Bentonite
(iii) Silica Flour (iv) Iron Oxide
These binders develop green strength, baked strength, hot strength and impart smooth surface finishing. They greatly increase the amount of oil necessary in oil sand mixes. They are finely pulverized materials.
(c) Other Binders- They are Portland cement, cement sodium silicate. Portland cement and cement harden at room temperature.
3) Water- In a core sand mixture, water contents may vary between 2.5 and 7.0%. Binder and additives work only in the presence of moisture. Optimum quantity of water develops good green strength, edge hardness; scratch hardness and good tensile strength after baking.
4) Special Additives- Material other than the basic constituents are also added to core sand mix-ture in small quantity in order to enhance the existing properties and to develop certain other properties. Some of the additive materials are sea coal, pitch and asphalt, graphite, coke silica
flour, wood flour, perlite, dextrin and molasses boric acid & sulphur.
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EXPERIMENT -2
Objective: - To determine clay content in a molding sand sample.
Equipments: - Clay washer (model vcw), weight balance.
Description of equipments: - It consists of a unit having motorized stirrer timer, indicator lamp, switch, glass jar, and siphon tube.
Theory: - The clay is the principal binder used in most foundry sand. It may be present in the natural sand or may be added to it. It considerably affects the strength and other properties. Hence the determination of its quantity present in the sand is necessary. The difference between original weight and the final weight of the sand after the mud has been washed away gives the mud content of the sand. It can be easily expressed as a percentage of the original weight of the sand sample.
Procedure: - Preparation of alkaline solutions: -
(1) Weight 30 gm. of Sodium Hydroxide (NaOH).
(2) Dissolve it in 500 cc of distilled water.
(3) Make this solution 1000 cc by adding distilled water.
Experiment procedure-
1. Dry thoroughly a small quantity of prepared moulding Sand.
2. Separate 50 Gms of dry moulding sand and placed it in the glass jar.
3. Add 450 ml-distilled water in the jar up to level.
4. Now add 10cc alkaline solutions of sodium hydroxide into the solutions.
5. Turn the jar holder side and held the jar as per diagram and take the jar holder under it.
6. Keep the jar on jar holder.
7. Agitate the solutions for 8-10 minute with the help of clay washer.
8. Remove the glass jar and rinse sand and fines adhering to the stirrer into the glass jar by means of wash bottle.
9. Allow the sand to settle for 8-10 minutes.
10. Siphon out the water containing mud from the glass jar.
11. Now again add fresh water and 10 cc of NaOH to the sand.
12. Stir for 5 min and rinse sand and fines adhering to stirrer into glass jar by means of wash bottle.
13. Allow the sand to settle down for 5 min.
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14. Again siphon out the muddy water.
15. Repeat the process till the water over the settled sand is clean. This assures that the whole of the clay has been removed from the sand.
16. Dry the settled down sand.
17. Allow it to cool and weigh the dry sand.
18. Find out the percentage of the clay.
Observation/Calculation: -
Weight of sand sample to be tested ‘A’ = --------gm
Weigh of the washed and dried Sand sample ‘B’ = ------- gm
% Clay = A - B × 100 %
A
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Necessity of adding NaOH in water:
NaOH is added into water to increase the surface tension and viscosity. Due to presence of NaOH in water clay particles cannot settle down with sand in-stead they are held in suspension by NaOH particles. Thus clay is sucked out from the jar and the sand is completely made free from clay progressively.
Precautions: -
1. The sand sample should be dry before testing.
2. Handle the glass equipments carefully.
3. Stir the solution minimum 5 min.
4. Do not touch the solution with hand.
5. Siphon out the muddy water carefully.
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Manufacturing Processes Lab - I
PE - 217 Practical
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9
EXPERIMENT -3
Objective: - To determines moisture contents in a molding sand sample.
Instrument Descriptions: - The instrument operates on the principle of the gas pressure gener-ated between the moisture in the sand sample and the absorbent compound. The instrument is portable and need no power supply. It has calibrated scale ready to use.
Theory: - The moisture content in molding sand has a great bearing on its suitability for the purpose. Excess moisture reduces permeability and too low moisture contents reduce strength. Also many defects may occur on account of unbalanced proportion of moisture contents or its uneven distribution. As such the testing of moisture content is invariably a must to control the same. This test is carried out in different ways using different types of equipments.
Procedure: -
1. Keep the case on the plane platform
2. Open the case and check the equipment thoroughly
3. Set the balance bracket to its seat provided at left side.
4. See the level while tightening the wing nut
5. Place the balance lever, pan seat and pan in their proper position
6. Unclamp the cap of the tester and body of the tester from inside by brush
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Manufacturing Processes Lab - I
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7. Weigh the sample accurately by matching the red line on bracket and lever
8. Transfer the sample in the cap
9. Take two spoonful of absorbent compound and transfer it into the body of the tester
10. Hold the body horizontally and place the cap in position
11. Bring the clamp in position and tighten the cap with screw
12. Shake the instrumental vigorously. This insures immediately the mixing of sand sample and the absorbent compound.
13. Immediately the pointer of the gauge moves
14. Keep the instrument vertical position
15. Observe the reading when the pointer stops further movements
16. This will give the % age of moisture in the sample directly
17. Unscrew the handle and take out the cap
18. Throw away the used material
19. Clean the instrument after the experiment.
Observations/ Calculations: -
Weight of sand sample = ……………. gm
% Moisture = ……………..
Results: -
Moisture contents = --------- %
Precautions: -
1. Do not expose sand sample
2. Do not keep the absorbent compound exposed to atmosphere
3. Note down the reading after the stability of the pointer
4. Clean the instrument after use
5. Keep the instrument in the box after the test
________
Manufacturing Processes Lab - I
PE - 217 Practical
_________________________________________________________________________
Chandigarh- Patiala National Highway, Vill.- Jansla, Teh.- Rajpura. Distt. Patiala- 140401
Phone 01762-507084-85, 9855252599
11
EXPERIMENT- 4
Objective: - To conduct hardness test for mould and core.
Instrument used: - Hardness Tester (Model – VCH)
Instrument Descriptions: - It is handy instrument with a special gauge to read the hardness number directly. The tip of the instrument is made of tungsten carbide. It is a scratch type tester.
Theory: - Mould and core hardness test – surface hardness is measured to check the ramming density of the actual sand mould and core hardness is the property of a mould and core to which it can resists penetration plastic deformation. The hardness of a sand mould and core can be eas-ily tested by means of hardness tester, which works on the principle of dryness hardness testing m/c.
Procedure: -
1. Clean the tip and base of the instrument
2. Apply the instrument vertically placing the tip on a hard smooth and plain glass surface
3. Press on the surface until the surface of the base plate touches the surface of the glass
4. The pointer of gauge should show zero reading on dial after completion of one rotation of the pointer. This setting will show that the instrument is work-ing property.
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Manufacturing Processes Lab - I
PE - 217 Practical
_________________________________________________________________________
Chandigarh- Patiala National Highway, Vill.- Jansla, Teh.- Rajpura. Distt. Patiala- 140401
Phone 01762-507084-85, 9855252599
12
5. Hold the instrument in right hand vertically with tripped plough facing the surface of mould /dried core and dial indicator facing conveniently for obser-vation of readings
6. Press the instrument against the surface of the mould / core in such a way that the base of the instrument will just touch the surface of mould/ core
7. Slowly pull the tester longitudinally and firmly on the surface of the mould/ core (app. One inch.)
8. Observe the reading on the dial, which indicates direct hardness of the mould/ core
9. Note down hardness number
10. This hardness indicates the firmness of the skin of the mould/core, which is usually termed as mould/core hardness.
Observation / Calculation
Mould Hardness = …………..…
Core Hardness = ……………..
Precautions: -
1. Use the instrumental carefully.
2. Testing for accuracy should be done before experiment
3. Use the correct indenter for a particular test
4. During testing instrument should be vertical.
5. Keep the in instrument in box after experiment.
________
Manufacturing Processes Lab - I
PE - 217 Practical
_________________________________________________________________________
Chandigarh- Patiala National Highway, Vill.- Jansla, Teh.- Rajpura. Distt. Patiala- 140401
Phone 01762-507084-85, 9855252599
13
EXPERIMENT- 5
Objective: - To determines tensile, compressive, and transverse and shear strength of moulding sand in dry condition.
Machine used: - Universal Strength Machine
Machine Description: - The machine consists of oil reservoir, movable ram, plug in coupling, low and high pressure gauges to reed 0-1600 gm/cm2 and 0-13 kg/cm2 compression strength re-spectively, loading piston connected to threaded shaft and wheel, funnel with special connec-tions for filing the oil in the reservoir.
Theory: -
The strength of moulding sand is determined by tensile, compression, transverse and shear tests. All these types of strength tests are used for sand control purposes. Specimen for tensile, compressive, transverse and shear test can be made on different specimen box. Different shapes of test specimen are required for different tests. For tensile test a ‘8’ shaped specimen is made and for bending test a rectangular shape is made. For compression and sheer test a cylin-drical specimen is to be prepared by sand rammer. This entire test should be done on the speci-men in dry condition. There are two pressure gauges. Low pressure gauge is used for tensile and transverse test and high pressure gauge is used for compression and shear test. The direct read-ing of strength can be found from these gauges.
Procedure:-
Pre setting of the machine:
1. Place the machine on a plane surface.
2. Rotate the wheel anti clock to bring the piston assembly to the end of the res-ervoir.
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PE - 217 Practical
_________________________________________________________________________
Chandigarh- Patiala National Highway, Vill.- Jansla, Teh.- Rajpura. Distt. Patiala- 140401
Phone 01762-507084-85, 9855252599
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3. Remove the cap on the plug in coupling.
4. Press the funnel in the plug in coupling so that it is locked.
5. Fill the tunnel to half its capacity by hydraulic oil.
6. Pull the movable ram approximately 25mm. Some quantity of oil will enter into the reservoir.
7. Push the movable ram inside to remove the air inside the reservoir.
8. Make the level of the oil in the funnel and repeat the process till all the air from the reservoir is expelled out and oil is filled in the reservoir . This will be indi-cated by no appearance of air bubbles through oil in the funnel with movement of the movable ram.
9. Push the movable ram completely in.
10. Turn the knurled ring if the plug in coupling anticlockwise to release the lock and pull out the funnel.
Tensile Test: -
1. Prepare the standard sand specimen in the tensile core box.
2. Dry it in the rapid moister drier.
3. Insert the tensile attachment in the universal strength machine by keeping wheel 25mm opened.
4. Insert the pressure gauge in the plug in coupling and keep loose pointer in con-tact with main needle.
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PE - 217 Practical
_________________________________________________________________________
Chandigarh- Patiala National Highway, Vill.- Jansla, Teh.- Rajpura. Distt. Patiala- 140401
Phone 01762-507084-85, 9855252599
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5. Place the specimen in the proper place in attachment.
6. Now rotate the wheel clockwise until the load starts applying on specimen (this will be seen by the movement of the pressure gauge needle).
7. Continue the load applying till the specimen fails.
8. Read the tensile strength on the T.S. scale on the pressure gauge.
Compression Test: -
1. Prepare a standard sand specimen of dia. 50mm and 50mm height.
2. Dry it in the rapid moisture drier.
3. Rotate the wheel anti clock wise up to app. 25mm.
4. Insert the compression pads in respective position in universal strength ma-chine.
5. Place the specimen between the compression pads so that the plane surface of the specimen touches against the pads.
6. Place loose pointer in contact with main needle in the pressure gauge.
7. Rotate the wheel clockwise until the load starts applying on specimen.
8. Continue the load applying till the specimen collapses.
9. The red pointer also moves with needle as soon as the sample collapses the needle, return while the red pointer remains at the maximum reading before collapse of the specimen.
10. Note down the compression strength gives by red pointer on C.S. scale in pres-sure gauge.
Transverse Test: -
1. Prepare a standard sand specimen in transverse core box.
2. Dry it in rapid moisture driver.
3. Insert the transverse test attachment in the respective position in the universal strength machine.
4. Rotate the wheel anti clockwise upto 25mm app.
5. Insert the low pressure gauge in the plug in coupling.
6. Place the specimen on the place on attachment.
7. Keep loose pointer in contact with main needle in pressure gauge.
8. Rotate the wheel clock wise while the load applied on specimen.
9. Continue the load applying till the specimen cracked.
10. Note down the transverse strength on B.S. scale in pressure gauge.
Shear Test: -
1. Prepare a standard specimen of sand of 50mm dia. and 50mm height with the help of sand rammer.
2. Dry it in rapid moisture drier.
3. Rotate the wheel anti clockwise upto 25mm.
4. Insert the high pressure gauge in plug in coupling.
5. Keep loose pointer in contact with main needle.
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Manufacturing Processes Lab - I
PE - 217 Practical
_________________________________________________________________________
Chandigarh- Patiala National Highway, Vill.- Jansla, Teh.- Rajpura. Distt. Patiala- 140401
Phone 01762-507084-85, 9855252599
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6. Insert shear pads in the respective place.
7. Place the specimen between these pads.
8. Rotate the wheel clockwise until the load starts applying on the specimen.
9. Continue the load applying till the specimen shear longitudinally.
10. Not down the shear strength on S.S. scale in pressure gauge.
Results:-
1. Tensile Strength = -----------
2. Compression Strength = -----------
3. Transverse Strength = -----------
4. Shear Strength = ------------
Precautions: -
1. Remove air completely from oil reservoir.
2. Loose pointer should be in contact with main needle.
3. There should be no leakage of oil.
4. Insert suitable pressure gauge for a particular test.
5. Do not overload the gauge.
6. Clean the instrument after the test.
________
Manufacturing Processes Lab - I
PE - 217 Practical
_________________________________________________________________________
Chandigarh- Patiala National Highway, Vill.- Jansla, Teh.- Rajpura. Distt. Patiala- 140401
Phone 01762-507084-85, 9855252599
17
EXPERIMENT – 6
Objective: - To determine the permeability number of a molding sand sample.
Equipments Used: -
The instrument consists of a water tank, precisely calibrated, well balanced inverted air tank, freely floated inside the water tank, water manometer, permeability chart, seal-ing boss with rubber sleeve, O.P.D.valve, siphoning attachment, orifice of diameter 105 mm and .5 mm. The rubber boss carries at the centre arrangement to screw in the orifice. Arrangement also has a pressure probe which is connected to water tank of manometer.
Theory: -
It is that property of sand, which allows the gases and steam to escape through the moulding sand, when the hot metal is poured in the mould. A large volume of gases and steam is formed due to heating of moisture, coal dust, oil and similar other materials present in the sand.
If these gases are not allowed to go out they will either make the casting unsound or blast the mould. So it is very important property required in the molding sand. It depends upon the 1. Grain size 2. Grain shape 3. Binders 4. Degree of ramming 5. Water contents of moulding sand. Rounded grains of uniform size lead to a higher permeability. It is also affected by ram-ming of sand. Soft ramming will increase it. In practice it is further increased by applying went wires in the prepared mould.
V.H
Permeability Number = ----------
A .P.T V = Volume of air passed
H = Height
A = Area of the specimen
P = Pressure gauge reading
T = Time
Procedure: -
1. Clean the air tank from inside.
2. Adjust O.P.D. valve at ‘O’ position.
3. Open the air tank from inside tank by thumb and fingers.
4. Pour water into the water tank up to the water level mark on the outside of water tank.
5. Insert air tank into water tank carefully.
6. Fill the water in manometer tube through the valve provided at the left side of the manometer. The water level should coincide with the zero of the ma-nometer scale. It can be adjusted by opening zero adjust screw in front of manometer.
7. Screw orifice of 1.5mm diameter (small orifice for permeability below 50) with fingers on its proper place with washer on the rubber-sealing boss.
8. Tight the orifice by fingers only.
9. Prepare a specimen of green molding sand in the specimen tube.
10. Take the specimen tube with specimen and place it inverted over the rub-ber-sealing boss.
11. Read the height of the water column in the manometer tube.
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Manufacturing Processes Lab - I
PE - 217 Practical
_________________________________________________________________________
Chandigarh- Patiala National Highway, Vill.- Jansla, Teh.- Rajpura. Distt. Patiala- 140401
Phone 01762-507084-85, 9855252599
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12. Find out the corresponding permeability number from the chart fixed on the instrument.
13. Put the valve on ‘O’ position.
14. Whenever the air tank is flush with water tank, keep the value on ‘D’ posi-tion. Lift the air tank slowly up keeping the value ‘D’ position to avoid any water entering the air tube.
15. Clean the apparatus after the use.
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Manufacturing Processes Lab - I
PE - 217 Practical
_________________________________________________________________________
Chandigarh- Patiala National Highway, Vill.- Jansla, Teh.- Rajpura. Distt. Patiala- 140401
Phone 01762-507084-85, 9855252599
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Results: -
Permeability number for sand specimen =
Precautions:-
1. Instrument should be away from vibration.
2. Do not use metallic piece to clean the orifice
3. Always use blow air to clean orifice
4. Ensure positive sealing of the specimen tube on rubber sealing boss.
5. Put the air tank slowly to bring it to its original position, keeping valve in ‘D’ position to avoid any water entering the air tube.
6. For removal of the water from manometer use zero adjustment value.
7. Drain all the water from the instrument after experiment.
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Manufacturing Processes Lab - I
PE - 217 Practical
_________________________________________________________________________
Chandigarh- Patiala National Highway, Vill.- Jansla, Teh.- Rajpura. Distt. Patiala- 140401
Phone 01762-507084-85, 9855252599
20
EXPERIMENT – 7
Objective: - To measure grain fineness number of dried sand sample.
Equipments Used: - Sieve shaker (model VGH)
Equipments Descriptions: -
The instrument consists of 10 sieves, lid and pan. Timer and switch is provided on the panel. The shaker vibrates the sieves and the sand placed on the top sieves get screened and collects on different sieves depending upon the various sizes of grains present in the sand. The top sieve is the coarse most and the bottom most sieve is the finest of all the sieves.
Theory: -
The shape and size of the sand grains has a remarkable effect on the physical proper-ties of the foundry sand. The sand grains may have smooth, rough surfaces.
The smooth surface is preferred for moulding for the reason that such a surface renders high permeability, sinter point and plasticity to the sand mass, sand grains may have dif-ferent shapes. These shapes are rounded, sub angular, angular and compound. The rounded
________
Manufacturing Processes Lab - I
PE - 217 Practical
_________________________________________________________________________
Chandigarh- Patiala National Highway, Vill.- Jansla, Teh.- Rajpura. Distt. Patiala- 140401
Phone 01762-507084-85, 9855252599
21
grains do not bind together too well when rammed. Sub angular gives a relatively stronger bond but the permeability reduced. An angular or sharp grain produces a much stronger bond and a low permeability when rammed. Sand grains, which are connected together such that they don’t separate when screened, are called compound. They are not much preferred. The size of sand grains also affects the mould structure and its characteristics. Larger, regular and uniform grains increase smoothness on mould surfaces.
Procedure: -
1. Remove the clamping device by pulling the knobs of side flexible bar.
2. Take out the set of sieves.
3. Clean the sieves and pan with soft brush.
4. Arrange set of sieves having pan at bottom and coarsest sieves at top.
5. Check the timer and switch for off position.
6. Take 100 Gms. of dried and washed sand sample on the top sieve.
7. Keep entire sieve set on shaking mechanism.
8. Slide the clamping devices on two sides of flexible bars and clamp the set of sieves with the help of knurled screw provided.
9. Set the timer for desired sieving time (10 min.).
10. Put ‘ON’ the switch.
11. After completing preset timing the sieving will be stop automatically.
12. Disconnect the supply.
13. Remove the clamping device.
14. Take out all the sieves.
15. Weigh the grains remaining on the individual sieves.
16. Find out the percentage of the retained grains.
Observations/ Calculations: -
Weight of sand sample Wt = gms
Sieve opening
Size in micron
Wt. of grains in gms.
% Retained
Multiplication
Factor
Products
μm
Wg
Wg
(A) = ----- x 100
Wt
(B)
A×B
1700
5
850
10
600
20
425
30
300
40
212
50
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Manufacturing Processes Lab - I
PE - 217 Practical
_________________________________________________________________________
Chandigarh- Patiala National Highway, Vill.- Jansla, Teh.- Rajpura. Distt. Patiala- 140401
Phone 01762-507084-85, 9855252599
22
μm
Wg
Wg
(A) = ----- x 100
Wt
(B)
A×B
150
70
106
100
75
140
53
200
Sieve pan
300
ΣA=
Σ A×B
Σ A×B Sum of products
Fineness number = -------- = -----------------------------------------------------------
ΣA Sum of the % retained on each sieve and pan
Precautions: -
1. Before test clean all the sieves with soft brush.
2. Weigh the each sieve before test.
3. Remove sand grains from each sieve using soft brush.
4. Before tightening the knob ensure that sieves fit exactly into each other.
5. Do not rotate timer knob in anti clock wise direction.
6. Clean the instrument after experiment.
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EXPERIMENT – 8
Objective: - To study various features of cupola furnace and its charges calculations.
Theory: -
For melting of cast iron in foundry the cupola furnace is used. It has construction in the form of a hollow vertical cylinder made of strong mild steel plates. The stress in the whole structure is distributed uniformly. A prop supports bottom door, so that it may be not collapse due to large weight of charge and coke. When in operations a wind chamber encircles the cupola shell at a place little above the bottom of the shell. This chamber is connected to the furnace’s blower by means of a blast pipe, The air forced into the chamber by the blower and openings are called tuyers. Charging door is located at a suitable height above the charging platform. This platform is of robust mild steel construction, supported on four strong steel legs and is provided with a ladder weighted quantities of metal, coke, scrap and flux etc. are collected on this plat-form. The top of cupola is provided with a mesh screen and a spark arrester. This attachment facilitates a free escape of the waste gases and at he same time deflects the spark and the dust back into the furnace. In some cupola the upper portion is made tapered with top diameter as about half of the inside diameter of the cupola at the melting zone.
Advantages of Cupola: -
1. The initial cast is lower than other furnaces of same capacity.
2. Operation is easy.
3. It can be operated for a number of hours at a stretch.
4. It has a simple design.
Cupola Zones The various zones of cupola are as under: -
Well:- It is the space between the bottom of the tuyeres and the sand bad. The metal after melt-ing trickles down and collects in their space before it is tapped out.
Combustion Zone:- It is locked between the top of tuyeres and a theoretical level above it. The actual combustion takes place in it. A temperature of about 1540° C to 1870° C is produced in this zone.
Reducing Zone:- It is located between the top of the combustion zone and the top of the coke bed. CO2 is reduced to CO in this zone. The temperature falls from combustion zone temp. to about 1200°C at the top of this zone.
Melting Zone: - The first layer of metal charge above the coke bed constitutes this zone. The solid metal changes to molten state in this zone and trickles down through the coke to the well.
Preheating Zone: - It extends from above the melting zone to the bottom level of the charging door and contains a number of layers of coke and metal charges. The function of this zone is to preheat the charges from atmospheric temperature to 1093°C before they settle downwards to enter the melting zone.
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Stack- The empty portion of cupola above the preheating zone which provides the passage to hot gases to go to atmosphere, is known as stack.
Efficiency of Cupola: -
The thermal efficiency of the cupola is given by the ratio of heat ac-tually utilized in melting and preheating the metal to the heat evolved in it through various means.
Heat utilized in melting and supers heating of metal
ηcupola = 100 X ------------------------------------------------------------------------------------
Calculated value of coke +heat evolved due to oxidation of
iron, Si, Mn + heat supplied by air blast
Efficiency range between 30 to 50%.
Calculation of Cupola charge:-
In order that a casting may have the desired composition it is necessary to control the proportions of its various constituents at raw material stage. It is essen-tial because a number of loses and gains of different constituents takes place inside the cupola during melting and they have to be suitably compensated. It is possible only when these losses and gains are known in advance and also the composition of raw material is known in respect of these constituents. The losses and gains of different constituents during melting are a follows: -
1. Carbon- a gain of .1 to .15 percent.
2. Silicon- a loss of 10% in general.
3. Sulphur- a gain of about .03 to.05 percent
4. Manganese – a loss of about 15 to 20 percent
5. Phosphorus- practically no change
6. Iron- a loss of 4 percent.
The gain of carbon is due to its pick up from coke, loss in silicon is due to its oxidation, gains in sulphur is due to its pick up from coke, scrap and flux etc., loss of manganese is due to oxidation and the loss of iron is due to oxidation.
The method of calculating the charge will clear from the following example.
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The data are given as-
Constituents
Analysis of material in hand
Analysis of require cast metal %
Pig iron No-1
Pig iron No-2
Foundry returns
Purchased scrap
Ferro- silicon
Carbon %
3.5
3.25
3.2
3.5
-
3.0 to 3.5
Silicon %
3.0
1.6
1.2
1.5
50
2.25 to 2.5
Manganese %
.4
.8
.6
.5
-
.4 to .65
Phosphorus
.6
.4
.5
.5
-
.5 to .6
sulphur
.02
.02
.08
.1
-
.08 Max
Assuming a carbon pick up of .15% loss of silicon 10% loss of manganese 15% and increase of sulphur .05% during melting.
Calculation: -
Let us assume the proportion of different constitutes per 1000 Kg of charge. Let us try the composition of the mixture.
Pig iron No 1 – 30% Foundry returns - 40%
Pig iron No 2 – 20% Purchased scrap - 10%
Constitu-ents of charge
As-sumed % of differ-ent con-stitu-ents
Total Wt. of con-stituents per 1000Kg of charge
Analysis of various elements present in the constituents of metal change
C
Si
Mn
S
P
%
Total
Wt. Kg
%
Wt.
Kg
%
Wt
Kg
%
Wt.
Kg
%
Wt
Kg
Pig Iron-1
30
300
3.5
10.5
3.6
9
.4
1.2
.02
.06
.6
1.8
Pig Iron-2
20
200
3.25
6.5
1.6
3.2
.8
1.6
.02
.04
.4
.8
Foundry returns
30
300
3.2
9.6
1.2
3.6
.6
1.8
.08
.24
.5
1.5
Purchase scrap
20
200
3.5
7.0
1.5
3.0
.5
1.0
.1
.20
.5
1.6
Total
100
1000
33.6
18.8
5.6
.54
5.1
Analysis of aggregate charge %
3.36
1.88
.56
.054
.51
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Estimated loss or gain in melting %
+15%
-10.θ
15.0
.05%
-----
Estimated analysis of cast metal %
= + .005
3.365
= - .188
1.692
= - .084
.476
= - 0027
.0543
.51
Desired analysis of cast metal %
3.0 to 3.5
2.25 to 2.5
.4 to .65
.08 Max
.5 to .6
It is found that all the estimated proportion falls with in the desired limits except the sili-con contents, which is too low. Let is select a definite percentage say 2.4% of silicon with in the specified desired limits and amend the change ratio according to make good the efficiency of silicon.
Now desired proportion of silicon in cast metal = 2.4%
Estimated proportion of silicon in cast metal = 1.69%
Difference = 2.4-1.69= .71%
i.e. .71% silicon is to be added
i.e. .71×10 = 7.1 Kg silicon should be added to the final charge of 1000 Kg. Adding a suitable amount of Ferro silicon to the charge and balancing the total weight of charge by subtracting an adequate amount of some other raw material say foundry return can add this quantity of silicon to the charge.
Now Ferro silicon contains 50% silicon and foundry returns 1.5% silicon only. It means by adding 1 Kg Ferro silicon there is as addition of .5 Kg silicon in the charge and by re-ducing 1 Kg foundry return there is a loss of .012 Kg silicon.
Therefore this substitution enable a net gains of silicon .5 -.012 = .488 kg
For gaining .488 Kg silicon 1 Kg Ferro silicon addition is required.
Therefore gaining 7.1 Kg silicon the Ferro silicon addition 7.1 / .488 = 14.5 Kg.
Amount of foundry returns deducted from charge = 14.5 Kg.
Therefore net Wt. of foundry returns in the charge 300 - 14.5 = 285.5 Kg.
Now final compositions of charge are as
1. Pig Iron No. 1 = 300 Kg.
2. Pig Iron No. 2 = 200 Kg.
3. Foundry Returns = 288.5 Kg.
4. Purchased Scrap = 200 Kg.
5. Ferro Silicon = 14.5 Kg.
----------------------------------------------------------------
Total = 1000 Kg.
-----------------------------------------------------------------
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EXPERIMENTS –9
Objective: - To prepare a green sand mould for a stable engineering component.
Tools and Equipments used: - Shawl, Trowel, Moulding box, sand rammer, gaggers, runner and riser pin, slick, went wire, lifter, strike off bar, draw spike mallet, swab, bellow etc.
Pattern used: -------------------------------------
Theory: -
A mould can be described as a void created in compact sand mass which, when filled with molten metal will produce a casting. Obviously it is the impression left behind by a pattern after the withdrawal of the latter. It is very natural, therefore, that the said void or cavity will exactly resemble with the shape and sie of the pattern. The process of producing this cavity or mould is known as moulding.
Procedure:-
1. Clean the pattern i.e. any sand particles from the pattern.
2. Prepare a green sand mixture consisting at silica sand, 10 to 15% clay, 4 to 6 % moisture contents.
3. Mix and riddle this mixture by proper tempering.
4. Select the suitable moulding box, large enough to accommodate the pattern and also allow some space around it for ramming of sand.
5. The drag part is placed upside down on the moulding board.
6. The pattern is placed on the board inside the box in such a position that space is left for gate cutting.
7. If the pattern is in two pieces, place the lower part of the pattern in the drag.
8. Fill the drag with ordinary moulding sand, which are freely prepared.
9. Use gaggers if necessary and ram the sand properly.
10. Cut off the excess sand to bring it in level with the edges of the box.
11. Turned upside down of drag along with bottom board placed over it after venting.
12. Place the cope over the drag.
13. Assemble the other part of pattern in position.
14. Sprinkle a small amount of parting sand over the entire surface of cope.
15. Put runner and riser pin in position and support them vertically by tucking a small amount of moulding sand around them.
16. Place the gaggers if necessary and fill the cope with moulding sand.
17. Ramm the molding sand properly.
18. Cut off excess sand to bring to bring it in level with the edges of cope.
19. Remove runner and riser pins.
20. Apply went wire to provide the vents.
21. Make pouring basin.
22. Place bottom board over the cope and roll over the cope.
23. Remove pattern parts from both the drag and cope carefully with the help of draw spike and mallet.
24. Repair the mould if necessary.
25. Cut gate with the help of gate cutter.
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26. Remove loose sand particles with the help of bellow and lifter etc.
27. Reassemble the cope and drag after dressing the mould surface.
28. Clean the tools and instruments.
Precautions:-
1. Select suitable molding box as per pattern.
2. Proper mixing of moulding sand should be there.
3. Ramming should be proper.
4. Use gaggers to increase strength of moulding sand.
5. Use gaggers to increase strength of moulding sand.
6. Use parting sand between cope and drag surfaces.
7. Remove pattern parts carefully.
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LIST OF WELDING PRACTICALS
S. No.
Title
1
Specimen preparation and making of lap joint, Butt, T- joints with oxy- acetylene gas welding.
2
Making of lap, Butt, T- joints etc. with electric arc welding.
3
Study of MIG welding equipment and making a weld joint in this proc-ess.
4
Study of TIG welding equipment and making a weld joint in this process
5
Study of different process parameters in Friction welding and preparing a weld joint by this process.
6
To study various welding equipments namely generators welding torch etc.
7
To study the resistance welding processes and prepare welded joint.
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INTRODUCTION
Welding is a process of joining two materials with the help of heat or pressure or by some other means. The cost of welding is very less as compared to other processes and forms of strong joint. For this reason, it is largely used in the following fields of engineering.
i) Manufacturing of machine tools, auto parts, cycle parts etc.
ii) Fabrication of farm machinery and equipments.
iii) Fabrication of buildings, bridges and ships.
iv) Construction of boilers, furnaces, railways, cars aero planes, rockets missiles etc.
Types of Welded Joints
Lap Joint: - Lap joint is obtained by over lap pin the plates and then welding its edges. It may be single transverse, double transverse and parallel lap joints.
Butt Joint: - The butt joint is obtained by placing the plates edges to edge as in figure. In this type, if the plate thickness is less than 5 mm, beveling is not unpaired, when thickness of plate ranges from 5 mm to 12.5 mm, edge is required to beveled to V or U groove, while plates having thickness above 12.5 mm U or V groove is made on both sides.
Corner Joint: - A corner joint is obtained by joining the edges of two plates whose surface are of on angle of 90o to each other. It is used for light and heavy gauge sheet metal.
Edge Joint: - It is obtained by joining two parallel plates. It is economical for plates having thickness less than 6 mm.
T-Joint :- It is obtained by placing 2 plates whose surfaces are at right angle to each other as in figure. These are suitable for plates having thickness upto 3 mm.
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LAP JOINT
EDGE JOINT
CORNER JOINT
T- JOINT
BUTT JOINT
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PRACTICAL No. 1-A
Name of the Job : Fusion runs without fitter rod by Gas Welding.
Material Used : M.S. sheet 100 × 50 × 1 mm
Electrode Used : High pressure gas welding set with all accessories.
Pressure : 2 lbs/sq. inch
Note : All dimensions in millimeters. RF scale = 1/1
Tools and Equipments : Gas welding cylinders (Oxygen and Acetylene Cylinders), oxygen regulator and acetylene regulator, hose pipe, acetylene hose pipe, gas welding blow pipe, weld-ing goggles, wire brush, gas welding trolley, try square, marking punch, ball peen hammer chisel & lever shearing machine.
Procedure :
i) Mark and cut MS-sheet of size 100 × 50 mm with chisel and hammer.
ii) Clean the job with wire brush.
iii) Start the O2 from the cylinder & acetylene from its cylinder. Ignite the welding torch with help of spark lighter. Make neutral flame by opening the acetylene needle valve and O2 needle valve in equal ratio.
iv) Place the job on welding table, preheat the job for making puddle by putting the tip of blow pipe at an angle of 60o to 70o to the job which is in flat position. Rotate the blow pipe in semicircle direction to move the puddle from right to left position and complete the bead. This is called left ward or fore hand gas welding.
SAFETY PRECAUTIONS
1. Welding goggles are necessary for safety of eyes.
2. For hand protection, asbestos gloves are necessary.
3. Asbestos apron is necessary for the protection of your body.
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PRACTICAL No. 1-B
Name of the Job : Making Butt Joint by Gas Welding with filler rod.
Material Used : M.S. sheet (100 × 50 × 1 mm) each 2 , M.S. rod 1 mm
Electrode Used : High pressure gas welding set with all accessories.
Pressure : 2 lbs/sq. inch
Note : All dimensions in millimeters.
Tools and Equipments : Gas welding cylinders (Oxygen and Acetylene Cylinders), oxygen regulator and acetylene regulator, hose pipe, acetylene hose pipe, gas welding blow pipe, weld-ing goggles, wire brush, gas welding trolley, try square, marking punch, ball peen hammer chisel & lever shearing machine.
Procedure :
i) Mark and cut the MS-sheet with chisel and hammer or shearing machine.
ii) Clean the job with wire brush to remove dirt.
iii) Start the O2 & acetylene gas welding cylinders. Ignite the welding torch with the help of spark lighter. Make neutral flame by opening the acetylene needle valve and O2 needle valve in equal ratio.
iv) Place the job on welding table, preheat the job for making puddle by putting the tip of blow pipe at one angle of 60o to 70o to the job on flat position. Rotate the blow pipe at any in semicircle direction to move the puddle from right position and simul-taneously dipping the fitter rod into the puddle at an angle of 30o-40o and moving it obliquely upward and downward direction till the beds gets completed.
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v) Lift the job with help of tongs and place it on an anvil. Clean it with help of a wire brush and check the beading layer properly to see if there are any welding defects .
SAFETY PRECAUTIONS
1. Welding goggles are necessary for safety of eyes.
2. For hand protection, asbestos gloves are necessary.
3. Asbestos apron is necessary for the protection of your body.
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PRACTICAL No. 2-A
Objectives : To make a Lap Joint by arc welding.
Material Used : M.S. flat of size 100 × 52 × 6 mm (2 pieces)
Electrode Used : MS electrode 3.15 mm dia and SWG 10 of Length 350 mm.
Note : All dimensions in millimeters.
Tools and Equipments : Are welding machine with all accessories, electrode holder, try square, earth clamp, steel rule, chisel, hammer, wire brush, a pair of tongs, face shield, chip-ping hammer.
Procedure :
i) Mark and cut the MS flat to size.
ii) Switch on welding set, setting the current to 100 amperes approximately.
iii) Place one of the MS pieces on the other as shown in figure and do tacking at both ends.
iv) Complete layer carefully ensuring uniform welding all along the length.
v) Clean the weld joint with a chipping hammer and a wire brush.
vi) Inspect the welding layer for proper quality of weld.
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PRACTICAL No. 2-B
Objectives : To make a T-Joint by arc welding.
Material Used : M.S. flat of size 100 × 64 × 6 mm (2 pieces)
Electrode Used : MS electrode 3.15 mm dia and SWG 10 of Length 350 mm.
Note : All dimensions in millimeters.
Tools and Equipments : Arc welding machine with all accessories, electrode holder, try square, earth clamp, steel rule, chisel, hammer, wire brush, a pair of tongs, face shield, chip-ping hammer.
Procedure :
(i) Mark and cut the MS flat pieces to size.
(ii) Switch on welding set, setting the current to 100 amperes approximately.
(iii) Place one of the MS pieces on the other to make a T as shown in figure and do tacking at both ends on either side.
(iv) Complete layer carefully ensuring uniform welding all along the length on one side.
(v) Complete the layer carefully ensuring uniform welding all along the length on the other side.
(vi) Clean the weld joint with a chipping hammer and a wire brush.
(vii) Inspect the welding layer for proper quality of weld.
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PRACTICAL No. 2-C
Objectives : To make a Butt-Joint by arc welding.
Material Used : M.S. flat of size 100 × 64 × 6 mm (2 pieces)
Electrode Used : MS electrode 3.15 mm dia and SWG 10 of Length 350 mm.
Note : All dimensions in millimeters.
Tools and Equipments : Arc welding machine with all accessories, electrode holder, try square, earth clamp, steel rule, chisel, hammer, wire brush, a pair of tongs, face shield, chip-ping hammer.
Procedure :
(i) Mark and cut the MS flat pieces to size.
(ii) Switch on welding set, setting the current to 100 amperes approximately.
(iii) Place the MS pieces abutting each other to make a Butt joint as shown in figure and do tacking at both ends.
(iv) Complete layer carefully ensuring uniform welding all along the length .
(v) Clean the weld joint with a chipping hammer and a wire brush.
(vi) Inspect the welding layer for proper quality of weld.
SAFETY PRECAUTIONS
Some of safety precautions necessary for the use of arc welding equipment are as follows :–
1. Protection of eyes and face :–
(i) Never look at welding arc without shield as the UV rays and infra-red
rays emitted from the arc can harm eyes as well as skin of face.
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(ii) Always replace the clear cover glasses when they become spattered.
2. Protection of rest of body from radiation & weld :–
(i) Always wear flexible Gimlet, Gloves and a leather apron while welding in or-der to save the body from weld spatter and spark & UV rays and infra red rays emitted by arc.
(ii) Shoes worn by welder should be high topped. Street shoes will not prevent globules of molten metal from dropping into shoes.
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PRACTICAL No. 3
Objective: Study of MIG welding equipment and making a weld joint in this process.
THE MIG-WELDING PROCESS
MIG (Metal Inert Gas) or as it even is called GMAW (Gas Metal Arc Welding) uses an alumin-ium alloy wire as a combined electrode and filler material. The filler metal is added continuously and welding without filler-material is therefore not possible. Since all welding parameters are controlled by the welding machine, the process is also called semi-automatic welding.
The MIG-process uses a direct current power source, with the electrode positive (DC, EP). By using a positive electrode, the oxide layer is efficiently removed from the aluminium surface, which is essential for avoiding lack of fusion and oxide inclusions. The metal is transferred from the filler wire to the weld bead by magnetic forces as small droplets, spray transfer. This gives a deep penetration capability of the process and makes it possible to weld in all positions. It is important for the quality of the weld that the spray transfer is obtained.
There are two different MIG-welding processes, conventional MIG and pulsed MIG:
Conventional MIG uses a constant voltage DC power source. Since the spray transfer is limited to a certain range of arc current, the conventional MIG process has a lower limit of arc current (or heat input). This also limits the application of conventional MIG to weld material thicknesses above 4 mm. Below 6 mm it is recommended that backing is used to control the weld bead.
Pulsed MIG uses a DC power source with superimposed periodic pulses of high current. During the low current level the arc is maintained without metal transfer. During the high current pulses the metal is transferred in the spray mode. In this way pulsed MIG is possible to operate with lower average current and heat input compared to conventional MIG. This makes it possible to weld thinner sections and weld much easily in difficult welding positions.
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Recommended material thicknesses for MIG-welding
Conventional MIG-welding: with or without backing: > 3 mm
Pulsed MIG-welding: > 1 mm. Smaller thicknesses are possible, however with thinner diame-ter on welding wire.
For welding of thick plates preheating of 50-100 oC may be required to avoid lack of fusion.
Recommended welding positions for MIG-welding
All welding positions are possible. Pulsed MIG-welding is, however better in vertical and under-up positions.
Recommended shielding gases for MIG-welding
For thicknesses: < 12,5 mm: Argon
12.5-25 mm Argon or Argon/Helium mixtures
> 25 mm Argon/Helium mixtures or Helium
Joint geometry for MIG-welding
1. One sided I-joint for MIG-welding
2. Two sided I-joint for MIG-welding
3. One or two sided Y-joint for MIG-welding
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4. One sided U-joint for MIG-welding
5. Two sided double V-joint (X-joint) for MIG-welding
Applications of MIG-welding
MIG-welding is a general purpose welding process for welding of aluminium and applicable in most cases in all welding positions from about 1 mm sheet thickness to thick walled sections. MIG-welding also offers high quality welds with a high productivity. There are two main variants conventional MIG-welding and pulsed MIG-welding.
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PRACTICAL No. 4
Objective: Study of TIG welding equipment and making a weld joint in this process
TIG (GTAW) WELDING
Gas Tungsten Arc Welding (GTAW) is frequently referred to as TIG welding. TIG welding is a commonly used high quality welding process. TIG welding has become a popular choice of welding processes when high quality, precision welding is required.
In TIG welding an arc is formed between a nonconsumable tungsten electrode and the metal being welded. Gas is fed through the torch to shield the electrode and molten weld pool. If filler wire is used, it is added to the weld pool separately.
TIG Welding Benefits
• Superior quality welds
• Welds can be made with or without filler metal
• Precise control of welding variables (heat)
• Free of spatter
• Low distortion
Shielding Gases
• Argon
• Argon + Hydrogen
• Argon/Helium
Helium is generally added to increase heat input (increase welding speed or weld penetration). Hydrogen will result in cleaner looking welds and also increase heat input, however, Hydrogen may promote porosity or hydrogen cracking.
GTAW Welding Limitations
• Requires greater welder dexterity than MIG or stick welding
• Lower deposition rates
• More costly for welding thick sections
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Manufacturing Processes Lab - I
PE - 217 Practical
_________________________________________________________________________
Chandigarh- Patiala National Highway, Vill.- Jansla, Teh.- Rajpura. Distt. Patiala- 140401
Phone 01762-507084-85, 9855252599
43
Common GTAW Welding Concerns
We can help optimize your welding process variables. Evaluate your current welding parame-ters and techniques. Help eliminate common welding problems and discontinuities such as those listed below:
1. Weld Discontinuities
• Undercutting
• Tungsten inclusions
• Porosity
• Weld metal cracks
• Heat affected zone cracks
2. TIG Welding Problems
• Erratic arc
• Excessive electrode consumption
• Oxidized weld deposit
• Arc wandering
• Porosity
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Manufacturing Processes Lab - I
PE - 217 Practical
_________________________________________________________________________
Chandigarh- Patiala National Highway, Vill.- Jansla, Teh.- Rajpura. Distt. Patiala- 140401
Phone 01762-507084-85, 9855252599
44
PRACTICAL No. 5
Objective: Study of different process parameters in Friction welding and preparing a weld joint by this process.
FRICTION WELDING TECHNIQUES
The process
Friction welding refers to a range of techniques that rely on a relative motion between the ther-moplastic parts to be joined, while a force is applied between them, to cause the material at the interface to heat and melt. The vibration is then stopped and the parts are aligned, and held to-gether under pressure until a solid bond is formed. Such bonds are permanent, and have a strength approaching that of the parent material.
The main welding parameters associated with friction welding are speed or frequency friction pressure, forge pressure, displacement and duration. These parameters are generally interde-pendent and for any application a set of weld property optimisation trials would be undertaken prior to mass production of the welded thermoplastic component.
Almost any thermoplastic material can be friction welded, including filled, structural foamed, crystalline, and amorphous materials. There is the possibility of welding dissimilar thermoplas-tics and alloys, and successful joints can be made with, for instance, PS and ABS, PMMA and PC, and PPO/PA and PA.
Linear Vibration Welding
The principle behind linear vibration weld-ing is that the parts to be joined are brought into contact, under pressure, be-fore being moved so that the joint areas rub together with a linear reciprocating mo-tion.
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Manufacturing Processes Lab - I
PE - 217 Practical
_________________________________________________________________________
Chandigarh- Patiala National Highway, Vill.- Jansla, Teh.- Rajpura. Distt. Patiala- 140401
Phone 01762-507084-85, 9855252599
45
The parts are vibrated through a relatively small displacement, commonly referred to as the amplitude, of typically between 1.0 and 1.8 mm, for a frequency of vibration of 200Hz (high fre-quency), or 2-4 mm at 100Hz (low frequency), in the plane of the joint.
Industrial applications tend to be based around joints that are too long to be ultrasonically welded (i.e. greater than around 200 mm) and hot plate welding would typically take many min-utes to perform.
Automotive
Two-part bumper, fuel tanks, fuel pumps, expansion vessels, instrument panels, air channels, parcel shelves, inner door panels, hermetic sealing of a length of air ducting to the internal surface of a dash-board
Consumer
Spectacle frames, typewriter cover
Industrial
Filter housings, motor saw housings, heating valves, air induction ducting
Orbital Friction Welding
In orbital welding each point on the surface of one part orbits a different point on the face of the other part. The orbit is of constant rotational speed and is identical for all points on the joint sur-face. This motion is stopped after sufficient material is melted and the thermoplastic then solidi-fies to form a weld.
Orbital welding is a relatively new technique, and tends to fill the size gap between benchtop ultrasonic units and linear vibration welders, and most applications tend to be for automotive components.
Spin Welding
Spin welding requires a relative rotational motion between the parts to be joined, which always have a circular joint area.
Possible configurations for spin welding thermoplastics
The technique can involve relatively simple pieces of equipment such as lathes or drilling ma-chines. A lathe would produce a constant speed during the frictional heating stage (continuous drive friction welding) and a drilling machine would produce a reducing
speed characteristic during the frictional heating stage (inertia friction welding). In practice, pur-pose built machines are generally employed for spin welding to provide greater control and they may be of either the continuous drive or inertia type.
Spin welding has been exploited for applications as diverse as the manufacture of polyethylene floats, aerosol bottles, transmission shafts and PVC pipes and fittings. Apart from being a fast
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Manufacturing Processes Lab - I
PE - 217 Practical
_________________________________________________________________________
Chandigarh- Patiala National Highway, Vill.- Jansla, Teh.- Rajpura. Distt. Patiala- 140401
Phone 01762-507084-85, 9855252599
46
technique, another particular advantage is that welds can be formed beneath the surface of a liquid.
Angular Friction Welding
The principle behind angular friction welding is similar to linear vibration except that the motion is angular. The components to be welded are pre-assembled and vibrated in an angular motion through a few degrees. When the weld cycle is complete the component parts are returned to the pre-welded position ensuring good alignment.
The angular friction welding process is used for circular components where upper and lower component alignment is critical, and equipment tends to be bespoke.
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________
Manufacturing Processes Lab - I
PE - 217 Practical
_________________________________________________________________________
Chandigarh- Patiala National Highway, Vill.- Jansla, Teh.- Rajpura. Distt. Patiala- 140401
Phone 01762-507084-85, 9855252599
47
PRACTICAL No. 7-A
Name of the Job : To make a Tee Joint using a (resistance) spot-welding machine.
Material Used : G.I. Sheet, (S.W.G. 20)
Size : 100 mm × 30 - two pieces.
Note : All dimensions in millimeters.
Procedure :
First of all wash both the work pieces with the solution of hydrochloric acid. Place them be-tween two electrodes of machine making a Tee Joint. Pass electric current by pressing both the pieces with the help of puddle switches. You will see a slightly red hot or plastic stage on the job joint. Then complete the joint by pressing the puddle switch. This pressure should be ap-plied within five to ten seconds.
SAFETY PRECAUTIONS
1. Clean both the pieces of G.I. Sheet with hydrochloric acid to avoid it from rust and dust.
2. Press the puddle slightly. When you see a red hot or plastic stage, then press it with more pressure.
3. Set the current according to the thickness of G.I. Sheet.
________
Manufacturing Processes Lab - I
PE - 217 Practical
_________________________________________________________________________
Chandigarh- Patiala National Highway, Vill.- Jansla, Teh.- Rajpura. Distt. Patiala- 140401
Phone 01762-507084-85, 9855252599
48
PRACTICAL No. 7-B
Name of the Job : To make a Medical Cross Shape Joint using a resistance spot-welding machine.
Material Used : G.I. Sheet, (S.W.G. 20)
Size : 100 mm × 30 with two pieces.
Machine Used : Spot Welding Machine.
Note : All dimensions in millimeters.
JOB WORK
Procedure :
First of all wash both the work pieces with the solution of hydrochloric acid. Then place them between two electrodes of machine making Medical Cross Joint. Pass electric current by press-ing both the pieces with the help of puddle switches. You will see a slightly red hot or plastic stage on the job joint. Then complete the joint by pressing the puddle switch. This pressure should be within five to ten seconds.
SAFETY PRECAUTIONS
1. Clean both the pieces of G.I. Sheet with hydrochloric acid to avoid it from rust and dust.
2. Press the puddle slightly. When you see a red hot or plastic stage, then press it with more pressure.
3. Set the current according to the thickness of G.I. Sheet.
________
Manufacturing Processes Lab - I
PE - 217 Practical
_________________________________________________________________________
Chandigarh- Patiala National Highway, Vill.- Jansla, Teh.- Rajpura. Distt. Patiala- 140401
Phone 01762-507084-85, 9855252599
49
PRACTICAL No. 7-C
Name of the Job : To make a “L” Shaped Joint using a resistance spot-welding machine.
Material Used : G.I. Sheet, (S.W.G. 20)
Size : 100 mm × 30 with two pieces.
Machine Used: Spot Welding Machine.
Note : All dimensions in millimeters.
Procedure :
Wash both the work pieces with the solution of hydrochloric acid. Then place them between two electrodes of machine making “L” Shaped Joint. Pass electric current by pressing both the pieces with the help of puddle switches. You will see a slightly red hot or plastic stage on the job joint. Then complete the joint by pressing the puddle switch. This pressure should be within five to ten seconds.
SAFETY PRECAUTIONS
1. Clean both the pieces of G.I. Sheet with hydrochloric acid to avoid it from rust and dust.
2. Press the puddle slightly. When you see a red hot or plastic stage, then press it with more pressure.
3. Set the current according to the thickness of G.I. Sheet.