456A SMAW (Shielded Metal Arc Welding) 3

Question 1

What is the purpose of preheating before SMAW welding on high-carbon steel?

Accepted Answer

To reduce the cooling rate and prevent hydrogen-induced cracking

Answer

Preheating slows the cooling rate of the weld and heat-affected zone (HAZ), which reduces the risk of martensite formation and hydrogen-induced cracking. It also allows hydrogen time to diffuse out of the weld area before cracking can occur.

Question 2

In SMAW, what is 'undercut' and what typically causes it?

Accepted Answer

A groove melted into the base metal along the weld toe, caused by excessive amperage or incorrect electrode angle

Answer

Undercut is a groove or channel melted into the base metal at the weld toe that is not filled by weld metal. It is caused by excessive current, incorrect electrode angle, or too fast a travel speed. Undercut reduces the cross-sectional thickness and acts as a stress riser.

Question 3

What is the significance of the 'H4' or 'H8' suffix on a low-hydrogen electrode designation such as E7018-H4?

Accepted Answer

The maximum diffusible hydrogen content in mL per 100g of deposited weld metal

Answer

The H-designator indicates the maximum diffusible hydrogen content: H4 means ≤4 mL/100g, H8 means ≤8 mL/100g, and H16 means ≤16 mL/100g. Lower hydrogen content reduces the risk of hydrogen-induced cracking.

Question 4

When making multiple passes in a groove weld, what is the purpose of the stringer bead technique compared to weaving?

Accepted Answer

Stringer beads minimize heat input and HAZ size, providing better mechanical properties in high-restraint joints

Answer

Stringer beads involve minimal side-to-side motion and result in lower heat input per pass. This reduces HAZ size, minimizes distortion, and is preferred for high-strength or hardenable steels. Many WPS documents specify stringer beads to control heat input.

Question 5

What does the term 'deposition rate' refer to in SMAW welding?

Accepted Answer

The weight of weld metal deposited per unit of time (kg/hr)

Answer

Deposition rate is the weight of weld metal deposited per unit of time, expressed in kg/hr or lb/hr. It is affected by amperage, electrode diameter, electrode type, and welding position. Higher deposition rates increase productivity.

Red Seal Welder 456A Practice Test

Red Seal Welder 456A Practice Test

456A SMAW (Shielded Metal Arc Welding) 3