The Influence Of Heat-treatment Temperature On Secondary Hardening Of ER5Die Steel

ER5die steel is a new cold working die steel that developed by Shanghai materialsinstitute. The steel largely overcome the deficiency of strength-toughness and wearresistance and other shortcomings which traditional high-carbon and high-chromiumdie steel has, various process performance of the steel is good,and moderate cost.In this paper, the ER5die steel is quenching and tempering in differenttemperatures, Adopt MEF-3microscope, universal testing machine and scanningelectron microscope etc, after a series of test,analysed the microstructure andmechanical properties of ER5steel.After the test, some basic conclusions obtained in this paper as follows:1ER5steel has obvious secondary sclerosis phenomenon. Along with thequenching temperature of ascension that ER5steel secondary sclerosis of peaktemperature rise is also corresponding tempering. After quenching in1090℃, the peakof secondary hardening appeared when tempering between500~530℃, Afterquenching in1120℃, the peak of secondary hardening appeared when temperingbetween530~560℃, and the tempering temperature makes the the peak of secondaryhardening appeared is560℃above.2The secondary hardening effect caused by different heat treatment process isdifferent, of which1150℃quenching,560℃tempering steel has the strongestsecondary-hardening effect.3Improve quenching temperature can obviously increase the ER5steel secondsclerosis ability, but can lead to toughness becomes poor. Relative to ER5steelproduction in common use in the actual "high quenching high tempering " technology,using quenching at1090℃and tempering at500℃~530℃such a "low quenching lowtempering" technology, also can obtain good comprehensive mechanical properties.4When ER5steel tempering in high temperature, many tiny alloy carbideexudates, which cause secondary harding effect. The diffraction patterns of the carbideshows it’s VC.5The impact of the ER5steel fracture types shall prevail cleaves fracture, a largenumber of carbides in the organization become the accurate cleaves fracture of thecrack source, reduce the steel toughness.6A large number of the primary carbide exists in ER5steel will dissolve intothe base with the rising temperature of austenitizing, When facing tempering, much more and diffused alloy carbide VC will be precipitated. The more VC there is, thestronger of the effect of the secondary hardening will be. But rising the temperature ofaustenitizing will coarsen the grain, low down the mechanical properties.