单项选择题
A.淬火+高温回火B.淬火+中温回火C.淬火+低温回火D.正火
A.0.1%-0.25%B.0.25%-0.5%C.0.5%-0.9%D.0.9%-1.5%
A.40CrB.Cr12MoVC.60Si2MnD.20CrMnTi