A4 group is austenitic stainless steel which is for boiling sulfuric acid, hence the name called acid resistant steel, it is sub-stable acid-resistant steel, a typical representative is SUS316. 70 behind A4-70 represents 1/10 of the minimum tensile strength of fasteners, because it is austenitic stainless steel, the tensile strength will be enhanced by heat treatment, and it could improve tensile strength after deformation by the dislocation barrier (commonly known as work hardening). The A4-70 bolts market sharing is more than 316L.
C ≤ 0.030%, Si ≤ 1.00%, Mn ≤ 2.00%,
12% ≤ Ni ≤ 15%, 16% ≤ Cr ≤ 18%, 2.00% ≤ Mo ≤ 3.00%
Good corrosion resistance, suitable for a variety of media;
Added Mo, increased corrosion resistance of reducibility salt;
Resistance to marine and industrial air erosion, can be used in sea water equipment;
Because of its low carbon content, therefore it has excellent crystal boundaries corrosion resistance.
Applied in pulp and paper machines;
Good processing properties and weld ability.
”L” means low carbon 316, higher Ni proportion, it is better than 316.