The puncture of the cold drawn steel tube is characterized by a rough surface on the surface of the product, also known as pockmark. More continuous into pieces, also local or periodically distributed. The reasons for the pitting are:
1. The finished hole or the front hole of the finished product is worn, or the broken iron oxide scale is adhered;
2. The broken iron oxide scale is pressed into the surface of the rolled piece and then falls off;
3. Roll rust;
4. During the heating process, the surface is severely oxidized.
The way to get rid of the honing of the tube is:
1. When changing the roll, first check the roll, do not use the severely rusted roll, and replace the worn roll or hole type in time;
2. Improve the material of the roll, keep the groove cooling well, and use the process lubricant (see plastic processing process lubrication) to enhance the wear resistance of the groove;
3. Control the heating operation of the billet to maintain a positive pressure in the furnace and reduce the oxidizing gas. For some alloy steels which are easily oxidized and the iron oxide scale is not easy to fall off, the surface of the steel billet shall be covered with iron to protect the heating;
4. Remove the surface oxide scale with high pressure water, compressed air or iron brush before the roughing mill.