Effect of Quenching Temperature on Carbide Evolution of D2 Steel after Solution Treatment
After solution treatment and fractional quenching,the carbide evolution of D2 under different quenching temperatures was studied,the dissolution order of carbide was obtained,and the thermodynamic mechanism of carbide dissolution was analyzed.The experiment showed that the carbide content in D2 steel decreased with the increase of quenching temperature.At the quenching temperature of 920℃,the micro-structure contains a large number of spheroidal carbides,the distribution is dense,the size is not uniform,and the cryptocrystalline martensite and residual austenite are few.When the temperature rises to 1 000 ℃,the particle size of the spherical carbide becomes smaller and becomes dispersed.When the quenching temperature reaches 1 080℃,the spherical carbides disappear and acicular martensite appears.At the same time,with the increase of quenching temperature,the dissolution rate of alloying elements in carbides increases,the smaller eutectic carbides dissolve most,the larger eutectic carbides then dissolve,the dissolution of carbides,the content of carbon and alloying elements in austenite increases,the temperature increases,the diffusion rate of alloying elements also increases,and the alloying elements are evenly distributed in austenite.The stability of the austenitic phase is improved and the martensitic transition temperature is reduced.In summary,the carbide is uniform and fine when quenched at 1 150 ℃+1 080℃,which can effectively control the quenching crack and improve the strength and toughness of D2 steel.
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