| Abrasive resistant steel ball and grinding rod are used for milling medium in a ball mill,which is widely applied in mining,electricity,building materials and other industries.As a commonly used structural steel,high carbon low alloy steel has a homogeneous structure,essential impact toughness,high hardness and wear resistance after heat treatment.Meanwhile,as a material of rolling steel ball,high carbon low alloy steel has the characteristics of high hardness,good wear resistance.But it is easy to crack and has a lower service life.Grinding ball was replaced by grinding rod in many conditions,mainly by the lower carbon content was made of high carbon low alloy steel after heat treatment,but it has a lower service life.As an extension of the traditional heat treatment,cold treatment can improve the strength,toughness and abrasive resistance,promote the structures of materials homogeneous,and improve the dimensional stability and prolong the service life of the parts.Study the effect of cood treatment on microstructure and properties of high carbon and low alloy steels,and seeking ways to solve these problems,which has important technical and economic sense.In this paper,the content of alloying element Cr was 0%,0.5%,1.0% of the high carbon low alloy round steel and Cr1.0 wt% high carbon low alloy steel ball as the research object.After cold treatment,the influence of cold treatment on the microstructure,hardness,toughness,wear resistance and retained austenite of three kinds of round steel and steel ball specimens were studied.The main contents are as follows:(1)Changes of microstructure and properties three kinds of round steel after conventional heat treatment were analyzed by experiments.The effect of different cold treatment process on the mechanical properties and microstructure of three kinds of round steel was studied.Based on comparative analysis of the test specimens with and without cold treatment,the results showed that with the decrease of the cold temperature in the range of 25? to-80?,the residual austenite in the matrix transformed into martensite and the microstructure was refined;the hardness of three kinds of round steel specimens increased;the impact absorbing energy decreased.With the extension of cold treatment time in the range of 0 h to 24 h,some of the retained austenite were further transformed into martensite,the ultrafine carbides were precipitated.The hardness of specimens increased firstly,and then decreased,the overall trend was increased.The impact toughness was gradually increased.(2)In this paper,the effect of different cold treatment process on the mechanical properties and microstructure of Cr1.0 wt% steel ball was investigated.Through comparative analysis of the test specimens with and without cold treatment,the result showed that with the decrease of the cold temperature in the range of 25? to-80?,the contents of martensite in the matrix increased,the contents of residual austenite reduced;carbide precipitation distributed evenly in the matrix;the microstructure of specimens was refined;the hardness of the specimens increased;the impact absorbing energy decreased.With the extension of cold treatment time in the range of 0 h to 24 h,some of the retained austenite was further transformed into martensite and the ultrafine carbides were precipitated.The hardness of specimens increased firstly and then decreased,the overall trend was increased,the impact toughness was gradually increased.Compared with the specimens without cold treatment,the abrasive resistance of the specimen of Cr1.0 wt%steel after cold treatment increased significantly.Compared with Cr1.0 wt% round steel,steel ball had large deformation.The effect of deformation on the results was not obvious after cold treatment(3)Based on the observations of impact fracture morphologies of the Cr1.0 wt%round steel and Cr1.0 wt% steel ball specimens at various temperature,we can conclude,with the decrease of the cold temperature in the range of 25? to-80?,the percentage of fiber area in the fracture surface of the specimen decreased gradually,the fracture appearance was brittle;the ductile-brittle transition temperature of Cr1.0 wt% round steel and Cr1.0 wt% steel ball specimens was-50?.According to research results,after the suitable cold treatment process,Cr0 wt%,Cr0.5 wt% and Cr1.0 wt% round steel and Cr1.0 wt% steel ball have higher hardness and wear resistance,meanwhile,have a good impact toughness. |
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