The factors affecting the dimensional accuracy of tensile parts are the same as the requirements of working materials

[1]Factors affecting the dimensional accuracy of stamping and stretching parts

The dimensional accuracy of stamping and stretching parts refers to the difference between the actual size of stamping and stretching parts and the design size.The smaller the difference is,the higher the accuracy is.Ideally,the size of the blanking part is the same as that of the die edge,while the size of the punching part is the same as that of the punch edge.In fact,due to the definite elastic deformation caused by the force on the workpiece during blanking,the elastic recovery of the workpiece will occur after blanking,resulting in the inconsistency between the size of the blanking part and the edge size of the female die,the size of the punching part and the edge size of the male die,which affects the dimensional accuracy of the stamping and stretching part.

There are many factors affecting the dimensional accuracy of stamping and stretching parts,such as blanking clearance,die manufacturing accuracy,material properties and thickness,shape and size of stamping and stretching parts,among which the main factor is blanking clearance.When the gap between punch and die is too large,the material is subjected to large drawing effect in the blanking process,so the drawing deformation is large.

After the blanking of carbon steel tensile parts,the size of blanking parts is reduced and the size of punching parts is increased due to the elastic recovery of materials.When the gap is too small,the material will be compressed and deformed due to the extrusion of male and female dies.After blanking,due to the elastic recovery of the material,the size of the blanking part increases and the size of the punching part decreases.The dimensional accuracy of stamping and stretching parts is also related to the properties and thickness of materials.Because the nature of the material directly determines the elastic deformation of the sheet in the blanking process,the elastic deformation of the softer material is small,and the elastic recovery after blanking is also small,which makes the workpiece precision higher.The elastic deformation of the harder material is large,and the elastic recovery after blanking is also large,which makes the workpiece precision lower.When blanking thin material,the elastic arch bending is large,and the elastic recovery is also large,which makes the workpiece precision lower.

In addition,the dimensional accuracy is also related to the shape and size of the part.The larger the part size is,the more complex the shape is,the more difficult the mold manufacturing adjustment is,and the mold gap is not easy to protect evenly,so the larger the size deviation is.The influence of the above factors on the dimensional accuracy of stamping and stretching parts is discussed on the premise of determining the die manufacturing accuracy.If the manufacturing accuracy of the die edge is low,the accuracy of the punched parts cannot be protected.Therefore,the manufacturing tolerance of the cutting edge dimension of punch and die should be determined according to the dimensional accuracy requirements of the workpiece.

[2]Requirements for working materials of stainless steel stretching parts

When working,stainless steel tensile parts should bear the loads of impact,vibration,friction,high pressure,tension,bending and torsion,and even work at high temperature(such as cold extrusion).The working conditions are complex and prone to wear,fatigue,fracture,deformation and other phenomena.Therefore,the requirements for the materials of die working parts are higher than those of ordinary parts.Due to the different working conditions of all kinds of hardware stretching parts,the requirements for the materials of die working parts are also different.

1.Requirements for blanking die materials:for the working parts of thin plate blanking die,high performance and hardness are required.For thick plate blanking die,in addition to high performance and compressive yield point,in order to prevent die fracture or edge collapse,it should also have high fracture resistance,high bending strength and toughness.

2.The requirements of drawing die materials require that the working part materials of the die have good adhesion resistance(anti bite),high performance and hardness,determined strength and toughness and good cutting performance,and the deformation during heat treatment should be small.

3.The requirements of cold extrusion die materials require the working parts of the die to have high strength,hardness and high performance.In order to avoid impact fracture,it is also required to have certain toughness.Due to the large temperature rise during extrusion,it should also have certain heat fatigue resistance and thermal hardness.