Cangzhou Steel Pipe Group (CSPG) Co., Ltd.

Seamless steel pipes are divided into two types: hot-rolled and cold-rolled seamless steel pipes. Hot rolled seamless steel pipes are divided into general steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, geological steel pipes and other steel pipes. Cold rolled seamless steel pipes are divided into general steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, and other steel pipes, as well as carbon thin-walled steel pipes, alloy thin-walled steel pipes, Stainless thin-walled steel pipes, special-shaped steel pipes. The outer diameter of hot-rolled seamless pipe is generally greater than 32mm and the wall thickness is 2.5-75mm. The outer diameter of cold-rolled seamless steel pipe can reach 6mm and the wall thickness can reach 0.25mm. The outer diameter of thin-walled pipe can reach 5mm and the wall thickness is less than 0.25mm. Rolling has higher dimensional accuracy than hot rolling.

Generally, seamless steel pipes are made of 10#, 20#, 30#, 35#, 45# and other high-quality carbon steels such as 16Mn, 5MnV and other low-alloy structural steels or 40Cr, 30CrMnSi, 45Mn2, 40MnB and other composite steels, hot-rolled or cold Rolled. 10#, 20# and other low-carbon steel seamless pipes are mainly used for fluid transportation pipelines. Seamless pipes made of medium carbon steel such as 45 and 40Cr are used to manufacture mechanical parts, such as stressed parts of automobiles and tractors. Generally, seamless steel pipes must be used for strength and flattening tests. Hot-rolled steel pipes are delivered in hot-rolled state or heat-treated state; cold-rolled steel pipes are delivered in heat-treated state.

Hot-rolled seamless steel pipe, as the name implies, the temperature of the rolled piece is high, so the deformation resistance is small, and a large amount of deformation can be achieved. Take the rolling of steel plate as an example. Generally, the thickness of continuous casting billet is about 230mm, and after rough rolling and finishing rolling, the final thickness is 1-20mm. At the same time, due to the small width-to-thickness ratio of the steel plate, the dimensional accuracy requirements are relatively low, and the shape problem is not prone to occur, and the crown is mainly controlled. The requirements for the structure are generally achieved through controlled rolling and controlled cooling, that is, controlling the opening temperature, final rolling temperature and coiling temperature of finishing rolling to control the microstructure and mechanical properties of the strip.

• Classification of seamless steel pipe: 

1. There are round pipes and the special pipes according to the cross section shape.

With the same circumference, the round seamless steel pipes can carry more fluid than the special ones. And the round ones can afford strength evenly. So nowadays the round steel pipe is more commonly used. But in some difficult transportation conditions with twists and turns, special pipe is necessary.

2. There are cold drawn seamless pipe and hot rolled seamless pipe due to the producing process.

Normally, in the construction field, when the pipe diameter is within 57mm, we usually use cold drawn pipes, while up to that 57mm, we use hot rolled ones. The cold drawn seamless pipes are more precise then the hot rolled pipes.

3. We can also classify the seamless steel pipes according to the applications. There are fluid transportation pipe, structural steel pipe, low and medium pressure boiler tube, water seamless pipes, petroleum seamless steel tube, natural gas seamless steel pipes, coal gas seamless steel tube, to name a few.

4. Due to attributes of the pipe, we can also call them seamless line pipe, hydraulic tube, expanding seamless pipe and so on.

• Carbon Steel and Stainless Steel Welded and Seamless Pipe

Stainless steel pipe and carbon steel pipe are the most common type of standard pipe used today. They are part of tubular goods, which are manufactured to different specifications and standards. Pipes are sold by "nominal pipe size" in sizes from 1/8" to 72". The two most common types of pipes are welded pipe and seamless pipe. Both are available in carbon steel and stainless steel. Welded pipe is also called ERW (Electric Resistance Welded) pipe. Most common specification for welded carbon steel pipe is A53. Seamless pipe is made by a process that requires no welding. Most common specification for seamless carbon steel pipe is A106B. Stainless Steel pipe is made to spec A312. Stainless steel pipe is also available in both seamless and welded configuration. Most common stainless material is 316 and 304.