BOILER

BOILER

BME-Properties of Steam

SPOT WELDING

Write the definition of welding

Spot welding is a pressure resistance welding in which overlapping sheets are joined by local fusion at one or more spots. Heat is produced by electrodes placed above and below the workpiece.

Write the principle of resistance welding.i.e. heat is generated because of resistance to the flow of elect current through the workpiece.

PROCEDURE:
1. Job should be cleaned from grease, dirt, paint, scale, rust, oxides etc.
2. The tip of electrodes must be cleaned by emery paper regularly.
3. To avoid the electrodes getting overheated, water is kept running for cooling.
4. Proper welding current is to be set on current selector switch.
5. Proper time has to be set on timer.
6. Electrodes are brought against the overlapping surfaces of workpiece and small pressure is applied for just physical contact.
7. Welding current is switched on for proper time.
8. As current passes, a small spot area is heated and weld takes place. TEMP is about 815 to 930 degree centigrade.
9. Now current is cut off and extra force/ pressure is applied to electrodes' tips. Hold until the metal cools down and gains strength.
10. After that electrode pressure is released to remove the spot welded piece.

Draw figure and write advantages & disadvantages.
Write application/ uses of spot welding.

Instructions

Dear students,
I have put almost everything on this blog for yr preparation for examination.Moreover I would like to mention that:
-Gas welding is on other blog " mp coursematerial".
-There may be some spelling mistakes, because I could not do it till date.

FORMING

This is a primary shaping operation i.e. attaining the required form of a job by pressing, forging, rollong, spinning, extrusion, piercing, blanking, punching, drawing, squeezing, bending, coining, sizing etc,
Kindling refer sheet metal processes in MP COURSE MATERIAL on blog or site.
MECHANICAL WORKING OF METALS:
It is shaping of metals(plastic deformation) by means of external force.
Mechanical working may be either hot or cold working.
Hot Working: The working of metals above the recrystalline temperature but below the burning point.Some metals such as lead and tin have low recrystalline range so can be worked at room temp, but most of the metals have high recrystalline temp.
Write advantages and disadvantages.
Various hot workinh processes are: Hot rolling, hot forging, hot spinning, hot extrusion, hot drawing or cupping hot piercing etc.
Kindly go through these hot working processes-explained on site.
Cold Working: The working of metal below the recrystalline temp and deformation is achieved by slip of planes.Force required is more as compared to hot working.
NB: During cold working strength and hardness of metal increases, but stresses are set, which is annealed,if to be further worked to remove the hardness and residual stresses.
Write some advantages and disadvantages.
Cold working processes are- Sheet metal work, shearing, drawing squeezing, bending cold heading, rotary swaging, coining, sizing, spinning, extrusion, cold drawing, bending, streach forming, hobbing, embossing, staking, ironing, peening,etc.

Dictated material

Dear students,
Kindly go through the material, which I have dicdated in my lectures as follows:
-Types of production systems.
-Classification of Manufacturing Processes.
-MP coursematerial on blog and site too,e.g.industrial safety, first aid and sheet metal etc.
-Chart from input of BF to output as Pig Iron and then CI, WI and STEEL in furnaces
(Cupola, Puddling and Bessemer converter, EAF & open hearth).
-Carbon % in PI, CI, WI and Steels (MS, MCS, HCS, HSS and 18:4:1)
-Moulding Sand(classification and preparation of moulding sand)
-CORE and preparation of core sand.
-Riser, Runner and Gating system
-Differance between Welding, Braze welding, Brazing and Soldering.