Why is cold drawn steel tube usually more expensive than a 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 the wall thickness is thin. When the 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. The tolerance of hot-rolled seamless steel tubes 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 tubes, cold-drawn or rolled seamless steel tubes have a more complex process, it is made multiple times during the rolling process. The brightness and straightforwardness are much better than the hot rolled pipe, and the tolerance is much smaller. The tolerance of cold-drawn and cold-rolled seamless steel tubes 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 cold-rolled 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 the finished pipe, the process is much simpler. Speaks to price, hot rolled seamless steel pipe is $30-$75 per ton lower.

The main difference between cold rolled seamless tube and hot rolled seamless tube

From the processing technology: hot rolling is hot processing, cold drawing is cold processing. Hot rolling is rolled above the recrystallization temperature while cold rolling is rolled below the recrystallization temperature.

From the appearance to distinguish: cold rolled seamless steel tube surface bright, diameter size is smaller than hot rolled seamless steel tube. The diameter of hot-rolled seamless steel tube is larger than that of cold-rolled seamless steel tube, and the surface of hot-rolled seamless steel tube has obvious oxide scale or red rust.

In terms of accuracy, the precision of cold-rolled seamless steel tube is higher than that of hot-rolled seamless steel tube, and the price is also higher than that of hot-rolled seamless steel tube.

From the purpose to distinguish: hot rolling steel pipe in fluid transport, mechanical structure, such as the size requirements are not high occasions, cold rolling steel pipe used in precision instruments, hydraulic system, pneumatic, and other high requirements. The wall thickness of cold-drawn seamless tubes is more uniform than that of hot-rolled seamless tubes.

Advantages and disadvantages of hot rolling seamless tube: the advantage is that hot rolling can destroy the casting structure of steel ingot, refine the grain of the steel, and eliminate the defects of microstructure, so as to make the steel structure dense, mechanical properties are improved. The disadvantages are that 1, steel tensile properties along the thickness direction greatly deteriorate, and there may be interlaminar tearing when the weld is contracted. The local strain induced by weld shrinkage is often several times of yield point strain, which is much larger than that caused by the load. 2. Residual stress caused by uneven cooling. It may have adverse effects on deformation, stability, and fatigue resistance.

Cangzhou shenlong pipe manufacture is a premier worldwide source for carbon steel pipe, stainless steel tubes, seamless pipes, welded pipes, galvanized tubes, casing pipes, and steel fittings.