Why is cold drawn steel tube is usually more expensive than the hot rolled? Have you ever thought of their difference?

The outer diameter and wall thickness of the hot-rolled seamless steel tube is changing. The outer diameter is larger on one end and smaller on the other hand. The outer diameter and wall thickness alongside the whole steel tube is changing. This is much determined by the hot rolling production process. The process starts from round steel after the big furnace, burning to over 1080 in the round steel punch, the whole round steel is turned into a hollow tube billet. As the whole process takes some time, due to the high temperature, the OD of the pipe’s front end is larger, and wall thickness is thin. When temperature gets lower, wall thickness alongside the pipe becomes slightly thicker. And residual heat will help to calibrate the hot rolling of the tube billet, and the tube billet is rolled into the specified outer diameter. In all, the tolerance of hot-rolled seamless steel tube is relatively larger for cold-drawn and cold-rolled seamless tubes, and the difference between the two ends is about 0.5mm based on the diameter.

Compared with hot-rolled seamless steel tube, cold-drawn or rolled seamless steel tubes have a more complex process,it is made through multiple times of rolling process. The brightness, straightforwardness is much better than the hot rolled pipe, and the tolerance is much smaller. The tolerance of cold-drawn and cold-rolled seamless steel tube is about plus or minus 0.01mm, it is almost the same.This may fundamentally save the processing cost, especially when it is made into mechanical parts.

The main difference between the two is whether it is made by one-time forming of the tube billet through the cold drawing mold. Cold rolling is the slow forming of the tube billet through the cold rolling mandrel.It is difficult to distinguish cold-drawn seamless steel tube from of cold-rolled from appearance after annealing. But when it comes to mechanical strength, cold-drawn seamless steel tube is slightly softer than cold-rolled seamless steel tube, therefore, it has better mechanical strength. As one time sizing through the hot rolling mill into finished pipe, the process is much simpler. Speaks to price, hot rolled seamless steel pipe is $30-$75 per ton lower.