Study And Application On Quenching Dimensional Effect For Alloy Steel Parts

Quenching and tempering are regularly taken for alloy steel mechanical parts inorder to attain predefined mechanical properties and meet requirements in specificconditions. However, some premature failure of mechanical parts usually happenduring work because of quenching dimensional effect, improper material and heattreatment. So to select an alloy steel whose hardenability can well match requiredproperties of specific parts is an effective measure for the problem. But presentmain methods being widely used by international researchers to describehardenability of alloy steel are only suitable for cylindrical samples or parts, such asJC, critical quenching dimension, and equivalent depth of end quenching ,etc,which are limited in engineering greatly.In order to describe quenching dimensional effect for complex or heavy alloysteel parts in section, the concrete method was put forward combining temperaturefield calculation model with Continuous Cooling Transformation calculation modelin paper, and some application about selection and design for alloy steel parts werecarried out in accordance with the method and made successes. Following items aremajor content for the paper.(1) The best candidate alloy steel can guarantee 100mm hardening depth , 52～57HRC quality and correlated heat treatment for 8 rail straightening roller inPANZHIHUA IRON&STEEL CO. were determined based on temperature field andCCT diagrams.(2) 0.75C-2.9Cr-0.27Mo-1.8Mn-1.25Si-0.55Ni alloy steel was designed by usingThermo-Calc software for equilibrium phase calculation and CCT diagram calculation result based on temperature field calculations of 12 cold roller in orderto reduce stress and against early spallation&crack of roller body. The resultsindicated that air quenching critical diameter for cold roller is 140mm.In addition,optical microscope, TEM and X-Ray equipments also were used to analyzemicrostructure of the steel, the analyses can play strong theoretical role indevelopment and application for cold roller against spallation&crack.The economical air quenching cold-working die steel was designed followingprinciple above and applied to cold roller solved problems of inadequate hardeningdepth of 9Cr2MoV and spallation&crack of Cr12MoV, which indicated thatcombination of temperature field calculation, CCT diagram calculation andequilibrium phase calculation can be used to asses quenching dimensional effect forcomplex and heavy parts in section, the assesed results also are meaningful toselection and design for alloy steel.