Plastic Instability Analysis Of Grooveless Rolling Deformation And Fold Formation

Non-porous rolling has the advantages of low rolling energy consumption,high rolling mill operation rate,uniform deformation of rolling stock,etc.,and is widely used in the production of rod and wire.The non-porous rolling process is often used in the rough rolling process of rod and wire rod,but the rolling process has no side wall effect,and there is rolling instability,which may lead to surface quality defects such as torsion,dislocation and wrinkles of the rolled piece.The rolling instability of the non-porous rolling process is directly related to the widening and side shape of the rolled product.According to the actual production characteristics of high-speed wire non-porous rolling,the finite element simulation method is used to analyze the variation of the width and the shape of the drum shape when several typical size blanks are deformed under different pressures.The distribution range and the reduction scheme were pressed,and the influences of different aspect ratios,different frictions,different temperatures and different steel grades on the wide spread and side shape of the rolled products were analyzed.The results show that under the same reduction ratio,the influence of the aspect ratio of the rolling stock on the widening and side shape of the rolling stock is greater than that of the rolling stock size,rolling temperature and rolling friction.The larger the aspect ratio,the smaller the width of the rolled piece is,and the greater the critical reduction ratio of the drum.The width of the square rolled piece is much larger than that of the high-shaped rolled piece,and the critical pressing rate of the drum is much smaller than that of the high-shaped rolled piece.The reasonable rolling reduction range of the square rolling parts is 20~35%,and the reasonable rolling reduction range of the high-shaped rolling parts is 25~40%.The aspect ratio of the high-profile rolled product is smaller,the reduction ratio is larger,and the aspect ratio is in the range of 1.0 to 1.7,which is advantageous for the stability of the non-porous rolling.After the non-porous rolling of the rolled piece,the sides will show different degrees of drum shape.The drum shape on the side of the rolling piece directly affects the stability of the rolling process and the surface quality of the rolled material in the subsequent elliptical hole and round hole rolling process.In this paper,the ductile fracture criterion and fatigue energy method are used to predict the tendency and position of wrinkles on the surface of rolling stock in different round drums and in different shapes of elliptical holes,and reveal the inherent causes of surface wrinkles..The results show that the larger the drum shape rate of the rolling stock is,the smaller the probability of wrinkle defects appear on the surface of the rolled piece.When the flat rolled piece enters the round hole,the probability of plastic wrinkling and wrinkling is smal er than that of the square rolled piece into the el iptical hole.