1.What are the product standards and grades?
National Standards (GB/T): Such as GB/T 5213-2019 Cold-rolled Low-carbon Steel Plate and Strip, GB/T 3280-2015 Stainless Steel Cold-rolled Plate and Strip, etc.
Industry Standards or Enterprise Standards: Usually more stringent.
International Standards: Such as European Standards (EN), American Standards (ASTM), Japanese Standards (JIS), etc.
User Technical Agreements: These are the highest priority standards, where customers specify requirements for particular grades.
2.What are the elongation rates of ordinary and low-carbon steel series?
Grades such as: DC01, DC03, DC04, DC05, DC06 (GB/T 5213)
Applications: DC01 is used for general forming; DC04/05/06 are used for deep drawing and ultra-deep drawing (such as automotive body panels and fuel tanks).
Elongation range: Taking GB/T 5213 as an example, for sheet metal with a thickness ≥ 0.7mm:
DC01: Tensile strength 270~410 MPa, elongation after fracture A80mm ≥ 28%.
DC04: Tensile strength 270~350 MPa, elongation after fracture A80mm ≥ 34%.
DC06: Tensile strength 270~330 MPa, elongation after fracture A80mm ≥ 38%.
3.What is the elongation rate of high-strength steel series?
Grades such as HC340/590DP (duplex steel), HC420/780TR (transformation-induced plasticity steel), etc.
Applications: Automotive structural parts, safety components, requiring a certain degree of formability while maintaining high strength.
Elongation range: Significantly lower than low-carbon steel. For example, a 590MPa grade duplex steel may have an elongation of around 20%~30%; while a 780MPa grade advanced high-strength steel may only have an elongation of 14%~20%.
4.What are the methods to obtain the correct target value?
Direct Search: Based on the "Implementation Standard" and "Grade" specified on your quality certificate or purchase contract, consult the mechanical property table in the corresponding standard document.
Typical Range Reference (for preliminary judgment only, not as final basis):
General Purpose (Structural Components, Chassis Housings): Elongation is typically above 20% - 30%.
Deep Drawing/Drawing Applications (Automotive Panels, Complex Parts): Elongation requirements are very high, typically above 35% - 45%.
High-Strength Structural Components: Elongation will be lower, 15% - 25% is likely a common range.
Ultra-High Strength Steel: May be below 10%.
5.What are the key factors affecting elongation rate?
Chemical composition: High levels of elements such as carbon and manganese can reduce plasticity.
Rolling process: Improper control of final rolling temperature and reduction rate.
Annealing process: This is the most critical step. Annealing temperature, holding time, and cooling rate directly affect the recrystallization structure and plasticity of the material.
Testing issues: Sampling direction (longitudinal or transverse, usually transverse elongation is slightly lower), sample preparation accuracy, and whether the testing machine is operated correctly.