The difference between hot-rolled and cold-rolled seamless steel pipes

The difference between hot-rolled and cold-rolled seamless steel pipes

Seamless steel pipes are divided into hot-rolled and cold-rolled seamless steel pipes because of their different manufacturing processes.  Among them, the hot-rolled seamless pipe is divided into general steel pipe, low and medium pressure boiler steel pipe, high pressure boiler steel pipe, alloy steel pipe, stainless steel pipe, petroleum cracking pipe, geological steel pipe and other steel pipes.

Cold rolled (dial) seamless steel pipe is divided into ordinary steel pipe, low and medium pressure boiler steel pipe, high pressure boiler steel pipe, alloy steel pipe, stainless steel pipe, oil cracking pipe and other steel pipes, as well as carbon thin-wall steel pipe, alloy thin-wall steel pipe, stainless steel thin-wall steel pipe, special-shaped steel pipe.

Cold-rolled seamless steel pipes are often small caliber, and hot-rolled seamless steel pipes are often large caliber.  The precision of cold-rolled seamless steel pipe is higher than that of hot-rolled seamless steel pipe, and the price is also higher than that of hot-rolled seamless steel pipe.

1.  Production process gap:
Hot-rolled seamless steel pipes are formed by heating billets to high temperatures and then rolling them.  It is to further process the hot-rolled seamless steel pipe at room temperature and produce it by cold drawing or cold rolling.  The process does not involve heating, but rather plastic deformation to achieve the final size and accuracy of the steel pipe.

2.  Different sizes:
The outer diameter of the hot-rolled seamless pipe is generally greater than 32mm, and the wall thickness is 2.5-75mm.  The outer diameter of the cold-rolled seamless pipe can reach 6mm, and the wall thickness can reach 0.25mm.  The outer diameter of the thin-walled pipe can reach 5mm, and the wall thickness is less than 0.25mm.

3.  Different surface quality:

The surface of the hot-rolled seamless steel pipe is relatively rough, usually with oxide skin and defects on the surface, and the color is dim. Subsequent surface treatment (such as pickling) is required to remove the oxide.

The cold-rolled seamless steel pipe has better surface quality, high finish and high dimensional accuracy because it is processed at low temperature.  Therefore, cold-rolled tubes usually do not need to be surface treated.

4.  Different uses:

Hot-rolled seamless steel pipes are usually used in situations where strength requirements are not high but large caliber is required, such as transportation pipelines, structural pipelines, large equipment components, etc.  It is also commonly used in piping systems that withstand low and medium pressures.

Cold-rolled seamless steel pipe: mainly used in areas with high dimensional accuracy and surface finish requirements, such as precision machinery manufacturing, automotive industry, hydraulic system, instrument and meter manufacturing.  Cold-rolled pipes are also suitable for high-pressure pipes or applications requiring high strength.

5.  Advantages and disadvantages:
Hot rolled seamless steel pipe
Advantages: Because hot rolling is carried out at high temperature, the steel is easy to form and the process is relatively simple, so the production efficiency of hot rolling is high and the cost is low, and the strength and toughness are good, and can be used to deal with large-size steel pipes.

Disadvantages: Due to the influence of high temperature, the surface quality of hot-rolled seamless pipes is poor, the mechanical properties are weak, and the dimensional accuracy is low.

Cold rolled seamless steel pipe

Advantages: Clean surface, high dimensional accuracy, superior mechanical properties, suitable for high-precision occasions.
Disadvantages: high cost, relatively complex process, high processing difficulty, low plasticity and toughness and limited size.

Summary

The advantages of hot-rolled seamless steel pipe are high production efficiency, low cost, good toughness, suitable for large sizes and applications that do not require high precision, but the surface quality and dimensional accuracy are relatively poor.

Cold-rolled seamless steel pipe has the advantages of high precision, high strength and surface finish, which is suitable for areas requiri ng high precision and high performance, but the production cost is high and the plasticity is poor.

Read more：What is hot rolling process?  or  All features of hot rolled pipes