1.What is the yield strength of ordinary low-carbon steel and general structural steel?
Typical grades: SPCC (China), DC01 (European standard), JSC270C (Japanese standard), SAE1006/1008 (American standard)
Yield strength range: 140 MPa - 280 MPa
Influence of state:
Annealed state (soft state): Lower yield strength (e.g., 140-180 MPa), good plasticity, suitable for deep drawing and complex forming.
Semi-hard state, fully hard state: Strength is increased (up to 280 MPa or more) by controlling the cold rolling reduction rate and subsequent heat treatment, but plasticity decreases.
2.What are the yield strength ranges of high-strength low-alloy steel and advanced high-strength steel?
HSLA (e.g., S355MC): Yield strength 300 MPa - 550 MPa.
Dual-phase steel (DP steel): e.g., DP600, yield strength 300 - 400 MPa (characterized by low yield strength, high tensile strength, and high work hardening rate).
Transformation-induced plasticity steel (TRIP steel): Offers higher formability and strength.
Martensitic steel (MS steel): e.g., MS1200, yield strength can reach 800 MPa - 1400 MPa or higher.
3.What is the range of yield strength for electrical steel (silicon steel)?
Yield strength range: relatively low, generally between 200 and 400 MPa.
4.What are the key influencing factors?
Heat Treatment States (Most Critical):
Fully Hardened State: Cold-rolled without annealing, highest strength, poor plasticity.
Annealed State: Cold-rolled followed by recrystallization annealing, softening the material, increasing plasticity, but reducing strength.
Quenching and Tempering: Annealing followed by light rolling (smoothing), achieving specific strength, hardness, and straightness.
Differences in Thickness Direction: Due to the work hardening effect of cold rolling, in the same coil of steel strip, the thinner sections usually have slightly higher strength than the thicker sections.
Anisotropy: Cold rolling causes grain elongation along the rolling direction, resulting in a slightly higher yield strength in the longitudinal direction (rolling direction) than in the transverse direction.
5.What are some material selection suggestions?
Deep drawing and complex forming (such as automotive body panels): High-quality low-carbon steel (annealed soft state).
General structural components, appliance housings, and brackets: ordinary low-carbon steel (annealed or semi-hardened).
Structural components requiring weight reduction or a certain strength (automotive structures): High-strength low-alloy steel (HSLA)