Hot-rolled and cold-formed steel thick-walled pipe

07-01-2018
Pipes

New technologies are gradually replacing the long-customary steel pipes, replacing them with plastic. However, there are situations where the characteristics of the latter are inferior. In this case, traditional steel will give "one hundred points ahead" of PVC and PP. And to find out in more detail, the article will give an overview of various types of thick-walled pipes.

The photo - thick-walled steel pipe for working with high pressure working environment

Kinds

The range of steel products is quite significant, however there are two main types - electrowelded, having a spiral (more preferable) or straight seam, and seamless, to which the article will be mainly devoted.

Consider them in more detail:

Type of production They are:
  • cold rolled;
  • hot-rolled, for example, from steel 40x;
  • heatdeformed.

Seamless is considered to be more reliable material, although the method of their manufacture does not affect the quality.
Wall thickness This takes into account its relationship with the diameter of the product.
  1. There are:
    • especially thin-walled;
    • thin-walled;
    • thick-walled;
    • especially thick-walled.

    In this case, the method of production does not matter, you can buy cold-rolled thick-walled tubular or electric products.

    1. Remember that the classification is strongly influenced by the diameter. For example, products that have a wall thickness of less than 1.5 mm and a diameter of less than 20 mm are considered thin-walled, with a wall thickness of up to 0.5 mm - the product is considered to be particularly thin-walled.
    Protective covering There are several methods to increase the resistance of products to corrosion and the effect of negative temperatures. For example, longitudinal electric-welded and for the gas pipeline should be covered with a layer of zinc, although the instruction does not prohibit the use of other product options.
    Copper pipe

    Tip: it is recommended when determining the class of pipe refer to specialized literature.

    Production

    The technology of making seamless and electrically welded pipe products is different. In the first case, use a flat billet, which is bent to form a body. In the second, a rod is used - a monolithic piece of cylindrical shape.

    Stainless pipe with thick walls

    Such production is much more difficult from the technical side, so the price of seamless products is higher.

    In work apply:

    1. Hot deformation, when the workpiece is heated to a temperature of about 50-60? C, above the threshold of crystallization of the metal. In this case, the steel, for example, 30hgsa marks becomes plastic, but does not melt. Then, on a piercing press, a hollow cylinder (sleeve) is obtained from a heated billet. The required shape is given by rolling, thanks to which the product acquires the required dimensions. The wall thickness is leveled, the geometric shape becomes correct and the specified diameter is ensured. After that, the product is immersed in water for rapid cooling, and then passes through a series of rollers for final calibration. Then it is cut, if necessary, into segments of standard length. Release of unmeasured materials is also allowed.
    Bronze tube with different wall thickness
    1. The cold method has two differences:
      • the product is cooled after the piercing mill;
      • pre-calibration is carried out in a cold state.

      Tip: before the last stage, the liner is annealed, heating to the temperature of steel recrystallization. Due to this, it is possible to remove internal stresses, and the metal becomes more plastic and viscous.

      Weight and dimensions of cold-formed thick-walled steel pipes

      Rules and regulations

      For hot-rolled ones, there are requirements and sizes of thick-walled pipes according to GOST 8732 78. Cold rolled ones correspond to GOST 8734-75.

      Consider the main points of these standards:

      GOST 8732-78
      1. The diameter of 20-550 mm.
      2. The maximum wall thickness is 75, the minimum is 2.5 mm.
      3. Length measured or unmeasured from 4 to 12,5 m.
      4. The amount of bending depends on the wall thickness (dimensions in mm):
        • up to 20 - 1.5;
        • 20-30 - 2;
        • over 30 - 4.
        GOST 8734-75
        1. Diameter - 5-250 mm.
        2. The range of wall thickness is 0.3-24 mm.
        3. Pipe classification by wall thickness:
          • especially thick-walled - the ratio of diameter to thickness is less than 6;
          • thick-walled - 12.5-6;
          • thin-walled - 12.5-40;
          • if the parameter is more - especially thin-walled.
          1. Additional conditions of the standard - the production of products, the indicators of which do not correspond to the gradation presented above, is carried out after preliminary approval of the technical specifications.
          2. The curvature of the cold-deformed pipe for each meter is (in mm):
            • up to 3, when the wall thickness is 4-8;
            • up to 2 - at 8-10;
            • up to 1.5 - if the thickness is more than 10.
            Plastic pipe with thick walls

            Where use

            Such products are used in the most critical areas, where the main role is played by reliability, for example, in:

            1. Hydraulic systems, in which seamless steel pipes are able to withstand heavy loads.
            2. In the production of different types of energy - boiler heat exchangers should operate reliably regardless of excessive internal pressure and high ambient temperatures. Thick-walled seamless pipes provide an opportunity to effectively address issues in the process of operation of devices exposed to extreme combined loads. Their repair can be done by hand.
            3. Gas and oil production, when a large depth of drilling requires the use of the most reliable materials for the casing. Such products can withstand the pressure of rocks, ensuring reliable operation during ground movement.
            4. Chemical industry - use thin-walled and thick-walled pipes. If the former are needed to ensure clean production, the latter are needed to withstand considerable pressure.
            Reinforced rubber tube

            Conclusion

            The list of possibilities of a thick-walled steel pipe can be large, as we saw in the article. Were considered seamless and electric products that are used in various industries. Although the first and more expensive, but they are able to better show themselves in processes where nothing else can be installed apart from them. The video in this article will help you find additional information on this topic.

            Categories