Welding Processes Flashcards

In oxyfuel welding (OFW), what flame type is produced when the oxygen-to-acetylene ratio is approximately 1:1?

Answer: Neutral flame

A neutral flame is produced at approximately a 1:1 oxygen-to-acetylene ratio, burning completely without excess oxygen or carbon and suited for welding most metals.

What is 'globular transfer' in GMAW?

Answer: Irregular, large droplets that fall from the wire tip and often cause spatter, occurring at intermediate current and voltage levels

Globular transfer produces large, irregular droplets (larger than the wire diameter) that fall under gravity and commonly cause spatter, occurring between short-circuit and spray transfer conditions.

Which process uses a non-consumable carbon or graphite electrode to apply heat, typically for gouging and cutting?

Answer: Carbon arc welding / air carbon arc cutting (CAC-A)

Air carbon arc cutting (CAC-A) uses a carbon/graphite electrode with a compressed air jet to blow away molten metal, commonly used for back-gouging welds and preparing joints.

What is the primary purpose of preheating the base metal before welding high-carbon or alloy steels?

Answer: To reduce the cooling rate and minimize the risk of hydrogen cracking and hard heat-affected zones

Preheating slows the cooling rate after welding, reducing the formation of hard martensite in the HAZ and allowing hydrogen to diffuse out, both of which help prevent hydrogen-induced cracking.

In resistance spot welding (RSW), heat is generated by which principle?

Answer: Electrical resistance heating (I²R) at the interface between the workpieces when current passes through them

RSW generates heat through the I²R (Joule heating) principle: the high electrical resistance at the faying surfaces concentrates heat to form a nugget when current flows through the electrodes.

Which of the following best describes the 'keyhole' technique used in some PAW and electron beam welding applications?

Answer: A small opening maintained at the leading edge of the weld pool where the arc penetrates completely through the base metal

In the keyhole technique, the high-energy beam or plasma arc penetrates fully through the workpiece, forming a small hole at the arc's leading edge that is filled in by molten metal behind it as the torch advances.

When welding austenitic stainless steel (e.g., 304 or 316), why is low heat input preferred?

Answer: Prolonged time in the sensitization range (800–1500°F) causes chromium carbide precipitation at grain boundaries, reducing corrosion resistance

Slow cooling through the sensitization temperature range causes chromium to combine with carbon and precipitate as carbides at grain boundaries, depleting the surrounding area of corrosion-resistant chromium—a condition called sensitization.