Seamless prepainted steel pipes come using a very interesting technology. To do this, a steel billet is taken, in which a through hole is made, after which it rolls on special equipment, making it thinner and longer. The principle is not very complicated, but it is only apparent simplicity.
By the way, there is another technology that differs from the first only in that the workpiece is cast in a special form. In this form, a rod installs, with which a through hole is formed. Furthermore, such pipes are often referred to as cast pipes.
Classification of seamless prepainted steel
There are two main differences between seamless prepainted steel pipes that determine the types of products, and these differences are the main GOSTs.
- Production technology: There are three types of seamless pipes: hot-rolled, cold-rolled and heat-rolled. The last two are united by one GOST, so it makes sense to consider them as one species.
- Wall thickness: In this category, the ratio of the diameter of the (outer) pipe to the thickness of its wall is taken as the basis. Moreover, there are four groups: thick-walled, extra thick-walled, thin-walled and extra thin-walled.
Hot formed seamless prepainted steel pipes
Before starting to consider all categories of seamless pipes according to their production method, it is necessary to pay a little attention to such a concept as temperature or recrystallization limit.
This is the temperature at which the metal has not yet become soft and molten, but already takes on a certain state of plasticity.
This is a very important value in seamless prepainted steel pipe production technology, because when it is reached, the structure of the metal changes. That is, stresses are relieved inside the workpiece, reducing the properties of the metal. Similarly, for steel, the recrystallization limit is +450C, for copper +270C.
- For the production of pipes, a steel billet is common, in which a through hole is made. Similarly, we call this process press flashing.
- Pre-steel billet is very hot.
But then both processes differ from each other. In the first case, the billet (cylindrical sleeve) rolls with continuous heating. In the second, the sleeve cools with water, and after that it rolls through the rollers of the rolling mill.
Production Process of prepainted steel Pipe
In both cases, the production of a seamless round prepainted steel pipe is a complex and costly process, so such pipes are not cheap. But the technical and operational characteristics are very high. Moreover, it determines the place of their application.
Therefore, pipes of these two types are common in those systems where the highest structural strength is required (where the slightest leakage of the material transported through the pipes can lead to irreparable consequences).
Water and gas pipes
Pipes for gas pipelines and water pipelines are allocated by a separate GOST, and they belong to the category of electric-welded pipes. This category consists of two groups, which include straight-seam and with a seam in the form of a spiral. They are mainly common for pipelines in which the material transports under a pressure of no more than 25 MPa.
The technology of their production is molding from sheet iron by welding two ends by electric welding. After manufacturing, such pipes must be tested with water for the strength of the weld, and an ultrasonic test of the connection zone is also carried out. Steel prepainted steel pipes of this category come without thread or with thread by knurling or cutting.
Groups of prepainted steel Pipes
Gas prepainted steel pipes is divided into four groups, which are based on a method for checking technical characteristics.
- Group A is the control of the properties of a product of a general mechanical plan.
- B is a check of the chemical composition of the metal.
- B is the control of both mechanical properties and chemical composition at the same time.
- D - Hydraulic pressure tests.
As for the large diameter pipes common in the oil and gas industry, longitudinally welded steel pipes are mainly common in this field.
Precision steel pipes
Very strict requirements are imposed on products in this category, so their dimensional values \u200b\u200bare very accurate. This applies to the outer and inner diameters, to the evenness of the end, wall thickness. Pay special attention to the cleanliness of all surfaces. In addition, such pipes come of very pure steel without a large amount of impurities.
Precision prepainted steel pipes are categorized as seamless. The range of wall thickness is quite large, which makes it possible to manufacture various parts common in machine and machine tool building from them.
For example, pistons for pumps, liners for cars, shock absorbers and other parts come from them. Such pipes have increased isotropic strength. Even the thinnest-walled products (0.5 mm) can withstand decent loads in hydraulic systems of various types and in other precise and complex structures.
Currently, precision steel pipes are available in galvanized, oil-coated and phosphated.
The Structure of prepainted steel Pipes
There is one category of steel pipes that has appeared on the market relatively recently, and it is highlighted by a separate standard, which indicates the importance of the production of these products - these are steel pipes in polyurethane foam insulation.
In fact, this is a multilayer structure, in other words - a pipe in a pipe. The first layer is the steel prepainted steel pipe itself. By the way, it can be any type and type. The second layer is PPU insulation. The third is a protective film that protects the insulation from mechanical stress.
The Diameter of Pipes
As for the polyurethane foam layer, this is a fairly thick coating that is applied to a metal surface either by pouring a liquid material or by putting a finished shell on the pipe. PPU cylinder can be one-piece or collapsible into two, three or four parts.
It all depends on the diameter of the pipeline. Thermal insulation can be ordinary or reinforced, depending on the weather conditions where the pipe will be common.
As for the protective sheath, there are two options here too: from low-pressure polyethylene or from galvanized metal sheet. The second option is more reliable, but it gives the pipe more weight, and, accordingly, the price.
Conclusion prepainted steel
Probably, steel prepainted steel pipes are the most demanded rolled profile common today in various fields. Here and industry, and agriculture, and construction, and life. Modern technologies of their production today guarantee the high quality of steel products.
And it does not matter how the pipe is made, from what steel grade, and under what requirements. In any case, it will be high strength and reliability, reasonable price and a guarantee of a long service life.
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