Study On Hot Deformation Behavior And Microstructure-Mechanical Properties Of Cr12MoV Steel

Cr12MoV is a cold working die steel which is widely used in die industry.It changes a little in size and is of good hardenability.It can abtain good hardness and abradability at 300℃-400℃.It is a ledeburite cold working die steel,rich in C and Cr.In the background of baosteel special steel corporation Project,that is about the technology research for plate and strip production of special metals and alloys,this article will research into the microstructure change in hot deformation process and the effect imposed by heat treatment parameters on the microstructure and mechanical properties.The processing maps of Cr12MoV steel are drawn from the experiment datas.The microscope deformation mechanisms at different deformation parameters are also researched in this article.All this can provide some help for the production of Cr12MoV steel.The main contents and results are as follows:(1) When single press test is taken, the influence of the deformation temperature, deformation degree and deformation rate to the stress of the steel are researched, and the mathematical model of resistance of deformation is established.(2) The softening behavior of Cr12MoV steel is researched in this article and the mathematical model between peak stressσp and Z parameters is obtained as follows: lnσp=-0.47989+0.116511nZ,the mathematical model between peak strain ep and Z parameters is obtained as follows:lnεp=3.10906 lnZ-13.62152.The activation energy of dynamic recrystallization is 538.712 kJ/mol.(3)When double press test is taken, the behavior of static recrystallization during isothermal process after the hot deformation of the steel in austenitic area is researched.The softening rate curve of the steel to be tested is drawn.(4) Based on the prasad instability criteria, the processing maps of Cr12MoV steel are drawn in this article with the cubic spline used in obtaining the relation beteen logσand logε.The power dissipation coefficience peak value transfer from medium temperature zone to high temperature zone with the increase of strain.The power dissipation coefficience peak value reaches 0.56.It is not advisable the Crl2MoV steel be defoemed below 950℃.The best deformation temperatures range from 1050℃to 1125℃at true strain 0.6 and the deformation rate should not excel ls-1.(5) With the experiment methods such as X rays and energy spectrum,the effect on Cr12MoV steel imposed by quench temperatures and temper temperatures and cooling medium is researched.The quantity of granular carbide decrease with the increase of quench temperature.when Cr12MoV steel is quenched at 900℃. The content of Cr in block carbide increase rapidly with the increase of temper temperature.When Cr12MoV steel is quenched above 900℃, the content of Cr in block carbide almost keep steady with the increase of temper temperature. Comparing with the effect on microstructure by water cooling,we obtain that secondary carbide is smaller in size and more disperse by oil cooling.Spheroidization effect on primary carbide is obvious and the carbide sharp corners become circular,as a result,this can relieve the split effect on matrix imposed by primary carbide.