Study Of The Low Temperature Salt-bath Vanadium-nitrocarburizing Technology

The surface strengthening technologies of the die and mould is to improve the rigidity, wear resistance, heat resistance, corrosion resistance, non-fusibility, seizure resistance remarkably and implement the high-point life of the die and mould by altering the surface component, the structure of the surface layer and deposit cladding on the surface. Presently, the technologies in common use, such as the surface hardening, the chemical heat treatment of surface diffusion, the vapour deposition process, the surface washing and plating are maturely developed. And along with the technologies of laser, lanthanon and nanometer are more and more widespread used, some of new surface project technologies are applied to the field of the surface strengthening technologies of the die and mould gradually, which promote the development of the surface strengthening technologies of the die and mould.In this thesis, according to the practical processing and working condition of steel H13, the manufacturing procedure extrusion moulds was modified, which reduced the ineffectual problems effectively. Furthermore, after the modification, 2 main ineffectual forms was found, which were dehiscence and attrition wear. Dehiscence was mainly caused by the inconsequent design of moulds, and attrition wear was mainly caused by the material itself, the steel H13 which had just minimum content of elements such as Cr,V according to the state standard.Bacing on investigating the surface strengthening technologies of the die and mould around the world, the thesis advanced the low temperature salt-bath vanadium-nitrocarburizing technology. The experiments in different processes of 45, T10 and Cr12MoV were carried out, in which the salt-bath was composed by the nitrocarburizing salt-bath , V2O5 and reducing matter, and the result showed as follow: ideal depth of seep layer can be attained by controlling the CNO- concentration around 32 %～36 % ; during the process of vanadium-nitrocarburizing, low concentration of CN- have maintained, and it hardly influences the depth of seep layer; as the V % increasing, the hardness of carbon steel have grown after vanadium-nitrocarburizing, 1.0 %～1.2 % of V content is appropriate; as the temperature of vanadium-nitrocarburizing increasing, the depth of seep layer increases, when exceeding 590℃, the depth decreases, the optimized temperature of vanadium-nitrocarburizing is 570℃; as the time of vanadium-nitrocarburizing increasing, the depth of seep layer increases, but surface rarefaction grows after 4 hours, the vanadium-nitrocarburizing should be controlled in 2~4 hours; as the carbon...