Properties Of White Layer On High Speed Cutting Surface Of Alloy Steel

In the process of high speed cutting,the sharp friction of the tool and workpiece will have a great influence on the surface of the workpiece,which will make the surface roughness larger and make the microstructure of the machined surface different from that of the matrix.Therefore,the study of machined surfaces has the significance of guiding practice.This paper adopts single factor method to change cutting parameters,and high speed turning test of 45 steel,GCr15 bearing steel and 40 CrNiMoA structural steel bar is carried out to measure cutting temperature.The roughness of the machined surface is measured.Make metallographic sample and observe the microstructure of surface layer.The main conclusions of this paper are as follows:(1)The cutting temperature analysis of 45 steel,GCr15 bearing steel and40 CrNiMoA bearing steel: the cutting speed is the most affected to the cutting temperature,followed by the feed rate and finally the back feed.(2)Under the influence of single variable cutting parameters,the surface roughness of 45 steel,40 CrNiMoA structural steel and GCr15 bearing steel increases first and then decreases.The surface roughness of 45 steel is the largest among the three materials,which is because the hardness of 45 steel is smaller than that of the other two materials,and the force change is obvious than that of the other two materials.For cutting parameters,the feed has the greatest effect on surface roughness.(3)The analysis of 45 steel,40 CrNiMoA and GCr15 shows that the cutting speed is the biggest in the cutting parameters,and the feed rate is the back feed.In addition,for the white layer,the influence of cutting parameters on it is approximately the same,which increases significantly first,then slows down,so different cutting parameters can be selected to control the thickness of the white layer.The purpose of improving the surface quality of machined workpiece.(4)When the cutting surface temperature is too high,the carbon element will be biased,and the carbon will precipitate with carbides in the process of particle conversion on the cutting surface,so the carbon content has the greatest effect on the formation of the white layer.When the carbon content of the two materials is close,the alloying elements will play a great role.In general,the more kinds of alloying elements,the greater the content,especially the alloy with high hardness,the better the comprehensive properties of the material.(5)Taking 40 CrNiMoA as an example,the white layer calculation model is established,which has the greatest influence on the thickness of the white layer,and the inherent properties of the material(such as yield strength,specific heat,thermal conductivity,etc.)also have a certain effect on the thickness of the white layer.