ITI Welder Interview Questions and Answers

Which welding processes do you know?

Shielded metal arc welding (SMAW, manual arc or stick), oxy-acetylene gas welding and gas cutting, MIG/MAG (GMAW) and TIG (GTAW). Say which ones you have actually done, and on what material.

How to say it: Lead with the process you are best at, not the full list.

What does E6013 mean?

E = electrode for arc welding; 60 = minimum tensile strength of the weld metal, 60,000 psi; 1 = usable in all positions; 3 = the coating type and current: E6013 runs on AC or DC of either polarity. E7018 is 70,000 psi, all positions, low-hydrogen coating, run on AC or DC electrode positive.

How to say it: Break the number into its parts one by one. That is exactly what they want.

Why are low-hydrogen electrodes like E7018 kept in an oven?

Their coating absorbs moisture from the air, and moisture brings hydrogen into the weld, which can cause porosity and cracking. They are stored and re-dried at the temperature the manufacturer specifies.

What is DCEN and DCEP?

DCEN (electrode negative, also called straight polarity) and DCEP (electrode positive, reverse polarity) are the two ways of connecting a DC welding machine. The electrode packet states which current and polarity to use. In TIG welding of steel, DCEN is used; aluminium is TIG-welded on AC.

How do you set the current?

From the range printed on the electrode packet for that diameter, adjusted for plate thickness and position: less current for vertical and overhead. Run a trial bead on scrap and adjust.

What arc length do you keep?

About equal to the diameter of the electrode's core wire. A long arc gives spatter, porosity and poor penetration; a too-short arc makes the electrode stick.

What are the three oxy-acetylene flames?

Neutral (equal oxygen and acetylene) for most steel welding; carburising (excess acetylene, with a feather) for jobs such as hard-facing; oxidising (excess oxygen) for brazing brass and bronze.

What colour are oxygen and acetylene cylinders in India?

Oxygen black, acetylene maroon. Keep acetylene cylinders upright, chain cylinders so they cannot fall, and use flashback arrestors.

How does gas cutting work?

The preheat flame heats mild steel to red heat, then a jet of pure oxygen oxidises the hot metal and blows it out of the cut. It does not work on stainless steel or aluminium, whose oxides melt at a higher temperature than the metal. Those are cut by plasma.

What are 1G, 2G, 3G, 4G, 5G and 6G?

Groove-weld test positions. For plate: 1G flat, 2G horizontal, 3G vertical, 4G overhead. For pipe: 5G is the pipe horizontal and fixed, welded all round; 6G is the pipe fixed at 45°, which covers all positions. F instead of G means a fillet weld (1F, 2F and so on).

What are the common weld defects and their causes?

Porosity: moisture, dirty metal, a long arc or poor gas shielding. Undercut: too much current, a long arc or the wrong angle. Slag inclusion: slag not cleaned between passes. Lack of fusion or penetration: too little current or travelling too fast. Excess spatter: too much current or a long arc. Cracks: hydrogen, fast cooling or a wrong electrode.

How to say it: Give each defect with one cause and one cure. It shows you can correct your own weld.

Why is a V-groove prepared on thick plate?

So the weld can penetrate the full thickness. The edges are bevelled, with a root face and a root gap as the welding procedure specifies, and the joint is filled in several passes: root, fill and cap.

How do you control distortion?

Tack weld at intervals, clamp or fix the job, weld in a balanced sequence on both sides, use back-step welding, keep heat input down, and pre-set the parts so they pull into line.

How is a weld inspected?

Visually first: size, profile, undercut, cracks. Dye penetrant shows surface cracks, magnetic particle shows surface and near-surface cracks in steel, and radiography or ultrasonic testing shows internal defects. A bend test is used to qualify a welder.

What safety precautions do you take while welding?

Helmet with the correct shade filter for the current, leather gloves, apron, safety shoes and full-sleeve cotton clothing. Fume extraction or ventilation, a fire extinguisher and a fire watch nearby, no flammables around, screens to protect others from the arc, a hot-work permit where required, and hoses checked for leaks with soap solution.

How to say it: Mention protecting other people from arc flash (screens) not only yourself.

Can you weld a drum or tank that held fuel?

Not until it has been cleaned, made gas-free and cleared by the authorised person. Vapour left inside can explode.

What is the usual test weld?

A butt or fillet joint on plate in the position the job needs (often flat or vertical), and for pipe welders a pipe joint. It is checked visually and often by a bend test. Clean the joint, tack it, set the current on scrap, and clean slag between every pass.

How to say it: Ask which position and electrode they want before you start.