The yield strength of SECC (electrolytically zinc-chromate-coated steel) depends primarily on the type of steel used as the base material. The galvanizing and chromating treatments have little effect on yield strength. The following are common examples:
1. Ordinary SECC (based on SPCC/SECC base material)
Yield Strength (σs): Typically 140-280 MPa
For example, the yield strength of SPCC (ordinary cold-rolled steel) specified in the JIS standard is approximately 140-220 MPa, and the base material for SECC is similar.
2. High-Strength SECC (e.g., based on high-tensile steel base material)
Yield Strength: Can reach 280-590 MPa or higher.
If the base material is made of high-strength steel (such as SAPH440, DP600, etc.), the yield strength will be significantly increased.
High-strength galvanized steel sheets for automotive applications (such as GA590DP) can achieve yield strengths exceeding 590 MPa.
3. Influencing Factors
Substrate type (SPCC, SAPH, DP steel, etc.) is the primary determining factor.
Work hardening (e.g., stamping, bending) may slightly increase yield strength but reduce ductility.
Coating Effects: Galvanizing and chromating primarily improve corrosion resistance and have little effect on mechanical properties.
4. Testing Standards
Yield strength testing typically complies with JIS G 3313 (SECC), ASTM A653 (galvanized steel), or customer-specified standards.
The 0.2% offset method (Proof Strength, Rp0.2) is typically used for determination.