WELDING

WELDING Welding is a materials joining process which produces

coalescence of materials by heating them to suitable temperatures with or without the application of pressure or by the application of pressure alone, and with or without the use of filler material.

Welding is used for making permanent joints. It is used in the manufacture of automobile bodies, aircraft

frames, railway wagons, machine frames, structural works, tanks, furniture, boilers, general repair work and ship building.

TYPES Plastic Welding or Pressure Welding

The piece of metal to be joined are heated to a plastic state and forced together by external pressure

(Ex) Resistance welding Fusion Welding or Non-Pressure

WeldingThe material at the joint is heated to a molten

state and allowed to solidify(Ex) Gas welding, Arc welding

Classification of welding processes:

(i). Arc welding Carbon arc Metal arc Metal inert gas Tungsten inert gas Plasma arc Submerged arc Electro-slag(ii). Gas Welding Oxy-acetylene Air-acetylene Oxy-hydrogen(iii). Resistance

Welding Butt Spot Seam Projection Percussion

(iv)Thermit Welding(v)Solid State Welding

FrictionUltrasonicDiffusionExplosive

(vi)Newer WeldingElectron-beamLaser

(vii)Related ProcessOxy-acetylene cuttingArc cuttingHard facingBrazingSoldering

Fusion Welding:

What is fusion welding..?

A process in which parts are melted and fused or joint together is called fusion welding.

or Fusion welding is a group of processes that bond

metal together by heating a portion of each piece above the melting point and causing them to join together.

Types of fusion Welding:

Types of fusion welding include: Arc welding. Oxy-fuel welding. Metal Inert Gas (MIG). Tungsten Inert Gas (TIG).

Fusion Welding Principles: Heat is supplied by various meanso Oxyacetylene gaso Electric Arco Plasma Arco Laser

Filler metal may be added

Arc Welding: What is Arc Welding…? Arc welding is a type of welding that uses a welding power

supply to create an electric arc between an electrode and the base material to melt the metals at the welding point. They can use either direct (DC) or alternating (AC) current, and consumable or non-consumable electrodes.

Arc weldingEquipments: A welding generator (D.C.) or Transformer (A.C.) Two cables- one for work and one for electrode Electrode holder Electrode Protective shield Gloves Wire brush Chipping hammer Goggles

Equipments used in arc welding:

Transformer:A welding transformer is an electrical transformer used in welding power supply. It pulls relatively low current drawn from the mains power typically limited to 15 A and converts it to the typical 50 A to 500 A used in arc welding and higher currents used in spot welding.

Electrode holder:The insulated handle that clamps onto the electrode. The welder holds this during welding to control the arc

Electrode:Filler metal coated with flux in the form of a rod or heavy wire

Electric cables:

Cables are used in welding to connect work piece with electric supply.

Welding shield (hood):This is the mask which is worn to protect the person welding from the bright flash of the arc.Welding gloves:These are special, insulated leather gloves that reach about 6 inches above the wrists, and protect the hands and lower arms of the welder (the person welding). Welding leathers:This is an apron like leather jacket that covers the shoulders and chest of the welder, used for overhead work where sparks might ignite the welder's clothing, or cause burns.

Step By Step Procedure of shielded Metal Arc Welding: Gather the tools and materials you will need to begin welding. Set up a safe work area, preferably with a table constructed of steel or other non-flammable material. Prepare the metal to be welded. Attach clamps to hold your metal pieces together. Attach the ground clamp to the larger piece of stock that is being welded. Select the correct rod and ampare range for the work you are attempting.

Turn on your welding machine. Hold the stinger in your dominant hand by the insulated handle. Select the point where you wish to begin your weld. Strike the electrode against the surface of the metal, pulling it back slightly when you see an electric arc occur. Practice traveling across the path of your weld with the electrode until you can keep a consistent arc, moving at a consistent speed. Complete Your weld. Clean your finished weld. Paint your weld with a suitable rust-preventative primer to protect it from corrosion.

Arc welding

Advantages Most efficient way to

join metals Lowest-cost joining

method Affords lighter weight

through better utilization of materials

Joins all commercial metals

Provides design flexibility

Limitations Manually applied,

therefore high labor cost. Need high energy

causing danger Not convenient for

disassembly. Defects are hard to

detect at joints.

Types Of Flames:1. Neutral Flame.(5600 to 5900 F)In neutral flame both gases are in equal proportions.

2. Oxidizing Flame (Excess of oxygen)(6000 to 6300F) An oxidizing flame is caused by increasing the oxygen from a neutral flame.

3. Reducing Flame (Excess of acetylene)(5400 to 5500F) If the oxygen is reduced, a carbonizing flame is created from a neutral flame.

Three basic types of oxyacetylene flames used in oxyfuel-gas welding and cutting operations: (a) neutral flame; (b) oxidizing

flame; (c) carburizing, or reducing flame.

Three basic types of oxyacetylene flames used in oxyfuel-gas welding and cutting operations: (a) neutral flame; (b) oxidizing flame; (c) carburizing, or reducing flame.