①碳含量每降低0.01%，最大锰含量则增加0.04%，允许最大锰含量到1.1%
②残余元素。

A=for anneal by heating to a temperature above the AC3 and cool in the furnace
N=for normalize by heating to a temperature above the AC3 and cool in still air
OQ=for quench into oil from a temperature above the AC3
WQ=for quench into water from a temperature above the AC3
AH=for air harden by heating to a temperature above the AC3 and cool in air at a rate fast enough to produce a hardened microstructure
T=for temper by heating to a temperature below AC1
ST=for solution treat by heating to temperature high enough to dissolve and any intermetallic phases followed by a rapid cool.

如果买方要求对这些等级进行冲击试验，则不进行弯曲试验。