CWI Welding Process Fundamentals 5

Question 1

Which of the following welding processes uses a non-consumable electrode?

Accepted Answer

GTAW

Answer

GTAW (TIG welding) uses a non-consumable tungsten electrode to maintain the arc, with filler metal added separately if needed.

Question 2

What is the function of 'preheat' when welding high-carbon or alloy steels?

Accepted Answer

To slow the cooling rate, reducing the risk of hydrogen cracking and hard brittle microstructures in the HAZ

Answer

Preheat reduces the thermal gradient and slows cooling, allowing hydrogen to escape and preventing the formation of brittle martensite in the heat-affected zone.

Question 3

In friction stir welding (FSW), the joint is made by:

Accepted Answer

A rotating non-consumable tool that generates frictional heat and mechanically stirs the plasticized material

Answer

FSW is a solid-state process where a rotating probe tool generates heat through friction and mechanically intermixes the plasticized (but not melted) material to form a weld.

Question 4

What does DCEN (Direct Current Electrode Negative) polarity mean for GTAW?

Accepted Answer

The electrode is connected to the negative terminal; electrons flow from electrode to workpiece, concentrating heat in the base metal

Answer

In DCEN (straight polarity), electrons leave the negative tungsten and strike the positive workpiece, directing about two-thirds of the heat into the base metal for deep penetration and minimal tungsten heating.

Question 5

A CWI finds incomplete fusion (lack of fusion) in a groove weld. Which root cause is MOST likely?

Accepted Answer

Improper electrode angle or insufficient heat causing the weld pool to fail to fuse to the sidewall or previous pass

Answer

Lack of fusion results when the weld pool fails to fuse to the base metal or preceding weld pass, typically due to insufficient heat input, improper technique, or wrong electrode angle.

CWI Practice Test

CWI Practice Test

CWI Welding Process Fundamentals 5