To study about welding process and tools.

Experiment No. : 05

Aim of the Experiment: –

To study about welding process and tools.

Theory: –

Welding is a material joining process that produces coalescence of material by heating them to a suitable temperature with or without the application of pressure and with or without the use of filler material.

Application: –

  • Automobile body
  • Aircraft frames
  • Railway wagons
  • Machine frames
  • Structural work
  • Shipbuilding

Types of Welding: –

Fusion Welding

Fusion welding is a process that uses heat to join or fuse two or more materials by heating them to the melting point. The process may or may not require the use of filler material.


Examples: Arc welding and gas welding.

Fusion Welding
Plastic Welding

In this welding, the pieces of metal to be joined are heated to a plastic state and forced together by external pressure.


Examples: Resistance and forge welding.

Plastic Welding
Electric Arc Welding

Arc welding is a type of welding process using an electric arc to create heat to melt and join metals. A power supply creates an electric arc between a consumable or non-consumable electrode and the base material using either direct (DC) or alternating (AC) currents.

Electric Arc Welding

Tools and Equipment Used in Welding

Welding Cables

Welding cables are made of aluminum or copper cables insulated with either red, black, or blue color. It is used for connecting or transferring current from the power source to the electrode holder and produces an arc to the workpiece, back to the power source.

Welding Cables

Electrode Holder

The electrode holder is designed to have the capacity of clipping the electrode manually in order to receive current and create the arcs.

Chipping Hammer

This arc welding equipment is used to reduce slag that occurs during welding. It is made of a wooden or rubber handle and a flat head and punch head made of metal. it is used by striking off the slags on the flat head of the hammer.

Wire Brush

It is used to clean dirt and to wipe away rust from the metal before welding.

Wire brush

Hand Screen

Hand screens are used for supervising the weld bead and for the protection of the eye.

Hand Screen

Protective Clothing

These types of arc welding equipment are used to protect the body of the operator.

Protective clothing includes an apron, boots, goggles, etc.

Apron (Protective Clothing)
Apron
Protective boots
Protective googles
Gas Welding

Gas welding is one of the oldest forms of heat-based welding.

It joins metals by heating the ends of the materials so they can melt and fuse.

There are many gases that burn at extremely high temperatures, making this process possible.

Gas Welding Equipment
  • Gas oxygen cylinder
  • Acetylene cylinder
  • Regulator
  • Gas hose
  • Non-return valve
  • Check valve
  • Torches
  • Goggles
  • Apron
Resistance Welding

It is a group of welding processes in which coalescence is produced by the heat obtained from resistance of the work to the flow of electric current in a circuit and by application of pressure.

Types of Joints in Welding

The term “weld joints” refers to the way pieces of metal are put together or aligned with each other.

Five Types of Joints in Welding

Butt Joint

  • It is a joint where pieces of metal are placed together in the same plane and the side of each metal is joined by welding.

T-Joint

  • It is formed when two pieces intersect at a 90° angle.
  • This results in the edge coming together in the center of a part or component in a “T” shape.

Corner Joint

  • It is placed in the middle, whereas a corner joint meets in the corner, in either an open or closed corner-forming forming an “L” shape.

Lap Joint

  • It is formed when two pieces of metal are placed in an overlapping pattern on top of each other.

Edge Joint

  • Metal surfaces are placed together to that edges are even one or both parts may be formed by bending them at an angle.
Welding Defects

Defects in welding are irregularities in the weld due to incorrect parameters or improper technique.

Following are the defects: –

Porosity

  • Tiny voids on or just below the weld surface.
  • Causes: Long arc, fast solidification rats, anodizing coating in Al.
  • Prevention: Use short arc length, clean surfaces, preheat.

Undercut

  • A groove at the weld toe that weakens the joint.
  • Causes: Large arc length, too large diameter of electrode, incorrect electrode angle.
  • Prevention: Adjust travel speed, arc length, and adjust electrode angle to fill.

Overlap

  • Excess weld metal extends beyond the joint or it tends to produce mechanical notch.
  • Causes: Low current, larger arc, slow arc travel speed.
  • Prevention: Use proper technique, correct electrode size.

Spatter

  • Small globules of metal thrown out during welding and sticking to the surface along its length.
  • Causes: Damp electrodes, improper shielding gas, excessive arc length.
  • Prevention: Use correct welding current, electrode type and size used .

Inclusion

  • Entrapment of solid metallic or non-metallic material in the weld.
  • Causes: Improper current, large electrodes, long arc.
  • Prevention: Maintain proper heat input and current, proper clean the weld.

Lack of Fusion

  • Lack to complete melting/fusion of same portion of the weld metal in a joint.
  • Causes: Low welding current, excess welding speed, poor heat input.
  • Prevention: Maintain correct current and speed.

Lack of Penetration

  • Improper penetration of weld metal through the thickness of joint or weld metal not extending its, the required depth into the joint root.
  • Causes: Low heat input, too large an electrode, small root gap.
  • Prevention: Proper joint preparation and correct electrode size.

Misalignment

  • Workpieces shift from their position during welding.
  • Prevention: Properly align and secure workpieces before welding.

Conclusion: –

To be written by student.

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