Study on microstructures and properties of several kinds of hot working die steel

Abstract

This paper deals with the microstructures and properties of AISI H13(4Cr5MoSiV1), UHB QRO 90M and 4Cr3Mo2V steels, and then discusses the means of improving the service life of hot working die. The results show that increase of quenching temperature improves the resistance to thermal fatigue and tempering stability. Fine heat treatment process can produce fine dispersed carbides. Shot-peening and cryogenic treatments can raise the compressive stresses at surface as well as the resistance of tempering greatly. Under the condition that a compound layer is not engendered, ionnitriding process can restrain the initiation and propagation of fatigue crack and enhance the resistance to thermal fatigue. Vapor surface treatment provides the ways to protect and lubricate the die by the porous films oI Fe30~, which are formed on the die surface. Electrical spark surface strengthening process forms compounds with high melting point and high stability on the die surface and thus enhances the properties of die's resistance to oxidation efficaciously. Besides, QRO 90M and 4Cr3Mo2V steels, because of the superiority in designing of composition, have better tempering stability and softening resistance than 4CrSMoSiV1 steel.