Carbon steel seamless steel pipe  is a long strip of steel. Steel pipe has a hollow cross-section, and a large number of used for conveying fluid pipelines, such as conveying oil, natural gas, gas, water, and some solid materials pipelines. Compared with solid steel such as round steel, steel pipe has the same bending and torsional strength and is light in weight. It is an economic cross-section steel, widely used in the manufacture of structural parts and mechanical parts, such as oil drill pipes, automobile drive shafts, bicycle frames, steel scaffolding used in construction, etc.

In the design of a pressure pipeline, pipe diameter after the calculation is necessary to choose the material of the pipe. The use of common pipe materials for pressure piping is determined according to the operating conditions of the conveying medium (such as pressure and temperature) and the characteristics of the medium under such conditions.

Improper choice of materials will cause waste or bury the hidden danger of an accident. If pipes of ordinary materials can be used, pipes of more expensive materials are chosen, which will increase unnecessary capital investment. The occasion of acid-resistant stainless steel with carbon steel will directly affect the normal operation of the pressure pipeline and even leave a curse. So in the selection of pipe material, the designer is required to first understand the type, specification, performance, and range of use of the pipe, it is best to investigate the pipe in other similar pressure pipe applications, and then determine the pipe material according to the following principles.

(1) The preferred pipe

In the selection of pipe material, generally consider the use of metal material first, metal material is not suitable, and then consider non-metallic material. Steel pipe is preferred for metal materials, and non-ferrous metal materials are considered after that. In steel pipe, carbon steel should be used first, and stainless steel should be used when it is not suitable. When considering carbon steel material, the welded steel pipe should be considered first, and the seamless steel pipe should be selected when not suitable.

(2) The influence of medium pressure

The higher the pressure of the conveying medium, the thicker the wall of the pipe is, and the higher the requirements of the pipe material are generally.

When the medium pressure is above 1.6MPa, seamless steel pipe or non-ferrous metal pipe can be selected. When the pressure is very high, such as in the production of synthetic ammonia, urea, and methanol, some pipe medium pressure as high as 32MPa, generally chooses material for 20# or 15CrMo high-pressure seamless steel pipe. Copper and brass tubes are generally used in vacuum equipment pipes and oxygen pipes with pressure greater than 10MPa.

When the medium pressure is below 1.6MPa, welding steel pipe, cast iron pipe or non-metallic pipe can be considered. However, the pressure of the cast iron pipe to bear the medium shall not be greater than 1.0MPa. The medium pressure that the non-metallic pipe can bear is related to the non-metallic material variety, such as the hard PVC pipe, the use pressure is less than or equal to 1.6MPa; Reinforced polypropylene pipe, working pressure less than or equal to 1.0MPa; ABS pipe, the working pressure is less than or equal to 0.6MPa.

For water pipes, when the water pressure is below 1.0MPa, welding steel pipes made of Q235A are usually used; When the water pressure is greater than 2.5MPa, generally adopt a 20# seamless steel pipe.

(3) The influence of medium temperature

Tubes of different materials are suitable for different temperature ranges. When the temperature of hydrogen gas is less than 350℃, a 20# seamless steel pipe is generally used. When the temperature of hydrogen gas is in the range of 351~400℃, 15CrMo or 12CrMo seamless steel pipe is generally used.

(4) the influence of chemical properties of the medium

Conveying different media, using different pipes. Some medium is neutral, general material requirements are not high, can choose ordinary carbon steel pipe; Some medium is acidic or alkaline, be about to choose acid or alkali-resistant pipe. Strong acid strong base and weak acid weak base of pipe use requirements are not the same, the same acid or alkali, different concentrations of pipe material requirements are also different. For conveying water and steam, carbon steel pipes will do. Such as in urea plants, carbon dioxide pipes, generally use stainless steel pipe, because carbon dioxide water formation of carbonic acid, and carbonic acid on the general steel pipe corrosion. Such as smoke sulfuric acid can choose carbon steel pipes, but dilute sulfuric acid can not be used in carbon steel pipes, because dilute sulfuric acid and carbon steel can react, and corrosion of carbon steel can use the hard aluminum pipe.

(5) The influence of the function of the tube itself

Some tubes in addition to the need to have the function of the transmission medium, and the function of shock absorption, coefficient of heat bilges cold shrink function, under the working condition, can often move function, such as civil liquefied petroleum gas, oxygen, acetylene in bottling parts, pipe often adopt high-pressure wire braided hose, and cannot use mobile hard steel pipe is not convenient.

Cangzhou Shenlong Pipe Manufacturing Co., Ltd. cooperates with Baosteel and Baogang to produce large-caliber seamless steel pipe, straight-seam welded pipe, spiral steel pipe, and pipe fittings. The products comply with API, ASTM, DIN, BS, and JIS standards, and can accept SGS, BV, and other inspections. The products are used in oil, natural gas, bridge, water conservancy, and other large-scale projects, which are worthy of trust.