A2-70, A2-50, A4-70, and A4-50 are common types of stainless steel bolts. What do they represent?
A2-70 means: Austenitic steel 304, soft, minimum tensile strength 700 MPa.
A4-70 means: Austenitic steel 316, cold worked, minimum tensile strength 700 MPa.
C4-70 means: Martensitic steel, quenched and tempered, minimum tensile strength 700 MPa.
Code Breakdown:
"A" represents the steel group:
The "A" represents austenitic steel. Other similar types are C and F:
"C" is martensitic steel.
"F" isferritic steel.
"2" represents 304 stainless steel, and 4 represents 316 stainless steel.
The numbers after the dash (e.g., -50, -70) represent the performance grade, which can also be understood as the minimum tensile strength. Specifically, these numbers represent theminimum tensile strength value:
"50" means the minimum tensile strength is no less than 500 MPa.
"70" means the minimum tensile strength is no less than 700 MPa.
"80" means the minimum tensile strength is no less than 800 MPa.
In the A group, grade 50 indicates soft steel, grade 70 indicates cold-worked steel, and grade 80 indicates high-strength steel.
In the C group, grade 50 indicates soft steel, grade 70 indicates quenched and tempered steel, andgrade 110 indicates quenched and tempered steel.
In the F group, grade 45 indicates soft steel, and grade 60 indicates cold-worked steel.
