Causes Of Folding Defects In Cold Rolling Of Seamless Steel Pipe

Causes of Folding Defects in Cold Rolling of Seamless Steel Pipe

Seamless steel pipe in the cold drawing production in the folding defects mainly exist in the outer or inner surface of the steel pipe, linear or spiral, continuous or discontinuous. The main reason for the folding is the quality of the pipe is not good, there is a folding, or the surface is mixed, serious scratches and cracks in the grinding at the edges and corners, after drawing extension and the emergence of folding. In order to avoid the generation of folding, it should improve the quality of pipe material and pay attention to inspection and grinding.

Seamless steel pipe straight to produce what factors

1. Effect of rolling temperature of seamless steel pipe. The rolling temperature is high, the rolling pressure is small and the head wear is small, so that the inner straight line defect is also reduced. But the rolling temperature is too high, the head surface easy to burn and stick metal and metal, to promote the increase in internal straight defects. General seamless steel pipe rolling temperature of about 1050 degrees Celsius as well.

2. The effect of deformation. The general deformation of large, within the straight road defects increased. When the total extension coefficient is constant, increase the first pass extension coefficient, reduce the second extension coefficient, can reduce the internal straight defects. Thus, the second deformation can eliminate the inner straightness generated during the first deformation; however, the straightening at the roll gap can not be eliminated because the head is not in contact with the metal.

3. Effect of lubricant. In order to reduce the friction coefficient between the seamless steel pipe and the head, it is possible to reduce the straightening defects in the seamless steel pipe before passing into the capillary into the capillary pipe before feeding the rolling mill. When no lubricant is used, the number and depth of defects will increase.

4. The shape of the head. The use of spherical head can reduce the internal straight defects, this is because the ball head processing surface, narrow wall area, rolling force is small, the head is not easy to stick metal and metal.

5. Rolled seamless steel pipe steel. Deformation resistance of high steel, due to rolling pressure, easy to cause internal straight defects.

6. Head surface state. Mainly depends on the heat treatment, the head surface should have a certain hardness and no cracks.