Fine-grained high-quality hot alloy steel,4Cr5MoSiV,high hardenability, high toughness, and fine-grained. Fine-grained high-quality hot alloy steel,4Cr5MoSiV,high hardenability, high toughness, and fine ... , and in air-quenching , the tendency of the appearing of iron oxide skin is small. In 500 tempering, it will appear ...