Effect of Alloying and Heat Treatment on Ni-Cr-Mo-V Steel
In order to meet the requirements of large thickness,high hardness and weldable shield steel for ship components and large-scale protective engineering,improvement of alloying composition and process are studied on the basis of Ni-Cr-Mo-V steel.Optical microscope and scanning electron microscope are adopted to study the influence of heat treatment process and alloying element on material property,and to investigate the characteristic of the microstructure of the test steel of different heat treatment processes and alloying elements.By adjusting the content of C,Si,Cr and Ni and the heat treatment parameter,it is found that when tempering at 430～520℃,with increase of the tempering temperature,the material strength increases and then decreases.Increase of C and Cr contents are beneficial for improving yield strength and tensile strength of the material,while increase of Cr content can significantly raise the ductile-brittle transition temperature and cause drastic reduction of impact toughness,but increase of Ni content can not only improves strength and hardness property,but also guarantees the low temperature impact toughness.
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