Cold-formed pipe: description, GOST and features

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

Cold-formed pipe has found its wide application in construction and in many areas of human activity. With the help of it, parts for furniture production are made, water, gas, oil pipelines are laid, as well as engineering networks, among them those designed for pumping aggressive environments. The mentioned products are highly durable, they do not have a seam, so the scope also extends to the aviation industry, as well as the automotive industry.

Pipe description

Familiarizing yourself with the state standards, you can understand that the cold-formed pipe is a hollow rod, on which there are no welds and joints. Manufacturing technology can be different, and it can be classified into several types, among them:

• pressing;
• forging;
• rolling;
• drawing.

The most common way is rolling. A pipe is used as a workpiece,which is produced by hot rolling. Steel is rolled using special equipment. The cold-formed pipe is based on carbon or alloy steel. Due to the fact that the described products do not have seams, this allows them to be used in negative conditions and under mechanical stress.

In terms of size, these pipes are much smaller than hot-rolled or welded pipes. However, one important advantage can be identified, which is dimensional accuracy. Products have a surface, the quality of which is much higher in comparison with pipes made using other technologies. Cold forming produces thin wall tubes.

Main features: classification by parameters

Cold-formed pipe can be classified by wall thickness and can be thin-walled or thick-walled. On this depends resistance to negative influences and strength. Thin-walled seamless pipe is lightweight. This property is in demand in the construction of non-standard structures. As for the thickness, it can be from 4 to 6 mm. However, if it is necessary to use a pipe with a wall thickness that differs from the mentioned parameters, products with walls up to 12 mm in thickness can be produced in production. They are particularly durable.

Diameter acts as one of the main parameters, it can be equal to a value ranging from 5 to 45 cm. Cold-formed steel pipe canalso have a different cross section, namely:

• oval;
• round;
• rectangular;
• square.

An additional characteristic is also the length. Pipes can be measured or non-dimensional. The measured length is 4, 5 or 5 m. If you need pipes of random length, then you can choose segments from 1.5 to 11.5 m.

State Standards

Cold-formed pipe (GOST 8734-75) can also be classified according to the method of use. Such products may have a special or general purpose. The latter option can have an outer diameter ranging from 5 to 250 mm, while the wall thickness is usually 0.3 to 24 mm.

Pipes can have different wall thicknesses and are:

• especially thick-walled;
• thin-walled;
• thick-walled;
• especially thin-walled.

For these products, there are technical specifications that are spelled out in state standards 8733-74. The documentation mentions that products can be divided into separate groups, among them are those that are denoted by letters from B to E. The first group is the regulation of the chemical composition, group C is the regulation of mechanical properties. Group G determines the rationing of mechanical properties and chemical composition.

If the pipe belongs to group D, then this indicates the normalization of hydraulic pressure. Mechanical properties are normalized after heat treatment of pipes, which are related togroup E. Seamless steel cold-formed pipes undergo control after manufacture. Inspection includes sizing, hydraulic pressure testing and mechanical properties control. Additional products are tested for bending and flattening, using GOST 3728-78 and 8695-77.

Additional properties

Cold formed pipe is made without welding. Production does not provide for preheating, because the products are obtained from the workpiece. Deviations are normalized by GOST 8734-75. There is a permissible deviation from the standard, which is 10 mm. According to the specifications, the difference in wall thickness and ovality should not exceed the limit values.

The curvature of the section is 3 mm, which is true for a segment 1 m long. In this case, we are talking about diameters ranging from 4 to 8 mm. Allowable curvature is reduced to 2 mm when the diameter is between 8 and 10 mm.

Properties of capillary products

Capillary pipes are manufactured in accordance with GOST 14162-79. Steel grade 12X18H10T is used for production. Such pipes are compared with steel. Their difference is:

• corrosion resistance;
• mechanical strength;
• durability.

Such seamless cold-formed steel pipes, the GOST of which was mentioned above, can be used in an aggressive environment. Manufacturing technology allows you to getpipes with high technical performance. The production is based on sulfuric acid treatment, which relieves internal stress. This improves operational safety in the gas, chemical and oil industries.

Such cold-formed steel pipe, GOST, which must be observed, has one important disadvantage, expressed in the complexity of the technological process. The result is an increase in the cost and final price, as well as an extension of production time.

Special purpose pipe features

Among cold-formed seamless products, one should single out those made of corrosion-resistant steel, as well as a material that can be subjected to high pressure. Another variety is a steel capillary pipe with a small diameter. If you are interested in pipes with corrosion-resistant properties, then you should know that they are manufactured in accordance with GOST 9941-81. The documentation contains specifications and assortment.

The wall thickness of such a pipe can be equal to a value from 0.3 to 24 mm. As for the outer diameter, its maximum limit is 250 mm. The smallest value is 5 mm. It is based on high-alloy corrosion-resistant steel. Products are subjected to the same tests as general purpose pipes. With their help, the laying of pipelines used for the transportation of substances with a high level of aggressiveness is carried out. The fluid being pumped may be at high temperatures. Anotherthe direction of operation is turbojet and jet engines, which are used to supply oxidizer, fuel and oil.

GOST pressure resistant pipes

Seamless cold-formed pipes (GOST 11017-80) can be used at high pressure. Their diameter is equal to a figure from 6 to 10 mm. The basis is carbon structural steel. The products are subjected to tests different from those mentioned above. Pipes are tested for hydraulic pressure and stretching, holding time reaches 10 seconds. The area of use is gasoline and diesel engines, which are also called fuel lines.

In closing

The surface of cold-formed pipes should be free of cracks and damage, as well as sundowns and other defects. Allowed scale, small nicks and other irregularities that do not interfere with inspection. If necessary, the surface is cleaned of scale.

The pipe is cut at a right angle. Burrs are removed from the ends. At the request of the customer, the ends of the pipes can be completed with chamfers. This rule is provided for a pipe whose wall thickness exceeds 5 mm. An important condition is expressed in the presence of an end ring with a width ranging from 1 to 3 mm.