MMET 207 Exam 3 with Verified
Solutions
To be considered a stainless steel, the chromium content must be at least ___% Correct Ans-
11.5%
Ferritic SS:
1. crystal structure
2. Carbon and chromium content
3. heat-treatable?
4. weldability?
5. Magnetic?
6. applications? Correct Ans-1. BCC
2. "low carbon", <.2% C, 16-20% Cr
3. non-HT
4. Poor
5. yes
6. decorative, good for high temp.
Martensitic SS:
1. crystal structure
2. Carbon and chromium content
3. heat-treatable?
,4. weldability?
5. Magnetic?
6. applications? Correct Ans-1. BCT
2. "high carbon", 1.2% C, 12-18% Cr
3. HT
4. Poor
5. yes
6. structural, non-rusting tools
Austenitic SS: (ternary phase diagram)
1. crystal structure
2. Carbon and chromium content
3. heat-treatable?
4. weldability?
5. Magnetic?
6. applications?
a. Nickel increases ___, is expensive, decreases its ___
b. Austnitic SS had best combo. of ___ & ___ Correct Ans-1. FCC
2. "very low carbon", .03% C, 16-26% Cr, 8-24% Ni (harder machinability)
3. non-HT
4. weldable
5. non-magnetic
, 6. chemical resistant, tanks, piping
a. corrosion resistance, machinability
b. corrosion resistance & fabricability
Sigma phase:
1. what is it?
2. when does it occur?
3. desirable? why? Correct Ans-1. hard, brittle compound of 50/50 iron/chromium
2. occurs when Cr content is above 20%
3. undesirable bc it reduces corrosion resistance & fabricability
Properties of Stainless Steels:
1. Great or poor conductor?
2. Electrical resistivity ___x that of carbon-steel
3. Thermal expansion problems, 300 series 50%
4. Modulus of elasticity is ___
5. corrosion resistance is ___ Correct Ans-1. poor
2. 6x
3.
4. 28-29x10^6
5. great
Solutions
To be considered a stainless steel, the chromium content must be at least ___% Correct Ans-
11.5%
Ferritic SS:
1. crystal structure
2. Carbon and chromium content
3. heat-treatable?
4. weldability?
5. Magnetic?
6. applications? Correct Ans-1. BCC
2. "low carbon", <.2% C, 16-20% Cr
3. non-HT
4. Poor
5. yes
6. decorative, good for high temp.
Martensitic SS:
1. crystal structure
2. Carbon and chromium content
3. heat-treatable?
,4. weldability?
5. Magnetic?
6. applications? Correct Ans-1. BCT
2. "high carbon", 1.2% C, 12-18% Cr
3. HT
4. Poor
5. yes
6. structural, non-rusting tools
Austenitic SS: (ternary phase diagram)
1. crystal structure
2. Carbon and chromium content
3. heat-treatable?
4. weldability?
5. Magnetic?
6. applications?
a. Nickel increases ___, is expensive, decreases its ___
b. Austnitic SS had best combo. of ___ & ___ Correct Ans-1. FCC
2. "very low carbon", .03% C, 16-26% Cr, 8-24% Ni (harder machinability)
3. non-HT
4. weldable
5. non-magnetic
, 6. chemical resistant, tanks, piping
a. corrosion resistance, machinability
b. corrosion resistance & fabricability
Sigma phase:
1. what is it?
2. when does it occur?
3. desirable? why? Correct Ans-1. hard, brittle compound of 50/50 iron/chromium
2. occurs when Cr content is above 20%
3. undesirable bc it reduces corrosion resistance & fabricability
Properties of Stainless Steels:
1. Great or poor conductor?
2. Electrical resistivity ___x that of carbon-steel
3. Thermal expansion problems, 300 series 50%
4. Modulus of elasticity is ___
5. corrosion resistance is ___ Correct Ans-1. poor
2. 6x
3.
4. 28-29x10^6
5. great
