AWS Material Selection & Properties 2 — Questions and Answers
Question 1: Which carbon content range classifies steel as 'high-carbon steel'?
- 0.05% to 0.30%
- 0.30% to 0.60%
- 0.60% to 1.00% (Correct answer)
- Above 1.50%
Correct answer: 0.60% to 1.00%
High-carbon steel contains approximately 0.60% to 1.00% carbon, making it harder but more brittle and difficult to weld.
Question 2: What does the term 'hardenability' refer to in welding metallurgy?
- The surface hardness of a weld bead
- The ability of steel to form martensite upon rapid cooling (Correct answer)
- The resistance of a metal to scratching
- The maximum tensile strength achievable
Correct answer: The ability of steel to form martensite upon rapid cooling
Hardenability describes how readily steel forms martensite through the depth of a section when quenched, which directly impacts weld HAZ properties.
Question 3: Which austenitic stainless steel grade is most susceptible to sensitization during welding?
- 304L
- 316L
- 321
- 304 (Correct answer)
Correct answer: 304
Type 304 stainless steel is susceptible to sensitization because it lacks stabilizers or low carbon content to prevent chromium carbide precipitation.
Question 4: What is the primary purpose of adding niobium (columbium) to stainless steel?
- Increase corrosion resistance in acidic environments
- Stabilize against intergranular corrosion during welding (Correct answer)
- Improve high-temperature oxidation resistance
- Reduce the coefficient of thermal expansion
Correct answer: Stabilize against intergranular corrosion during welding
Niobium acts as a stabilizer by preferentially combining with carbon, preventing chromium carbide precipitation and sensitization at grain boundaries.
Question 5: When welding dissimilar metals with different coefficients of thermal expansion, what primary problem can occur?
- Excessive spatter during welding
- Residual stress and distortion upon cooling (Correct answer)
- Porosity from gas absorption
- Lack of fusion at the weld root
Correct answer: Residual stress and distortion upon cooling
Different thermal expansion rates cause unequal contraction upon cooling, generating residual stresses that can lead to cracking or distortion.
Question 6: Which property describes a material's ability to be drawn into wire without fracturing?
- Malleability
- Ductility (Correct answer)
- Toughness
- Elasticity
Correct answer: Ductility
Ductility is the ability of a material to deform plastically under tensile stress, which is measured by elongation and reduction in area.
Question 7: What is the effect of sulfur content above 0.05% in steel on weldability?
- Improves arc stability during SMAW
- Promotes hot cracking in the weld and HAZ (Correct answer)
- Reduces the preheat temperature required
- Increases impact toughness at low temperatures
Correct answer: Promotes hot cracking in the weld and HAZ
Excess sulfur forms low-melting iron sulfide compounds at grain boundaries, causing hot cracking (solidification cracking) during welding.
AWS Material Selection & Properties 2
Which carbon content range classifies steel as 'high-carbon steel'?