Steel seamless hot focused pipes allow you to get more reliable and durable than from welded products, pipelines. This products are widely used to make parts of machines, structures and other technical purposes.

1

Seamless hot focused pipes, GOST 8731-74 for which regulates technical requirements To quality, made from carbon and alloyed steel grades. For the production of these pipes, forged, continuously cast and rolled blanks are used, which are preheated in a special furnace to a temperature greater than 50 ° C for recrystallization of steel.The exact thermal parameters depend on the brand of alloy. The metal of the workpiece is acquired by sufficient plasticity for the upcoming processing.

Depending on the sorting of pipes for their quality requirements, as well as the physico-chemical characteristics of the starting material, hot deformation produced different ways, technology system Each of which includes the following sequence of common elements:

• after heating, the metal is obtained by a sleeve (hollow blank);
• the sleeve rolls - get a rough tube;
• reduction and calibration - the final formation of the diameter and the pipe wall.

If necessary, before each subsequent technological operation, heated pipe can be heated.

The sleeve is obtained by one of the following ways:

• on presses;
• in mills for screw rolling;
• a combination of previous processes (combined): the manufacture of a thick-walled glass with a press roll flashing or pressing with the subsequent firmware of the resulting douse and the wall of the obtained sleeve in the mill-elongator (equipment for screw rolling).

Methods for producing a rough tube:

• on the mill pilgrim periodic longitudinal rolling;
• in the mill of continuous longitudinal rolling;
• screw rolling on rolling mills (mainly in the 3-fold assembliness, less often - in the 2-dwarf of the Dishover or Akol Roll);
• on the rush mill - the sleeve is pushed through the calibers, which decrease in diameter and have roller clips;
• metal squeezing on the pipe raise press in the ring-shaped gap.

The final size of the hot-deformed tubular products is usually obtained in reduction or calibration mills of continuous longitudinal rolling, much less often - on screw rolling equipment. In aggregates with a mill tandem (automatic mill) and a rack, the specified technological operation precedes the rilling (running in the pipe in the equipment for screw rolling). In some pipe-rolling units, which are specifically designed for the manufacture of seamless pipe products of large diameters, the final operations may be used by extenders.

Finished rental cools, after which it is cut into standard segments. As a result, the product produced must meet the requirements of the State Standard - the pipe is hot-deformed GOST 8732-78, which provides a sorting for this type of metal.

2

According to the sorting, these pipes in length are manufactured by the following segments:

• non-meter length - in the range of 4-12.5 m;
• products of measured length - segments within the unmercable;
• products of multiple dimensional - segments within the borders of the neurochnoy with a bunch of 5 mm on each cut;
• products of approximate length - segments within the unmercial.

Outside diameter The produced pipes are in the range of 20-550 mm values, the size of the wall thickness is 2.5-75 mm. An important characteristic is the ratio of the product diameter to the thickness of its wall. For this indicator, experts classify pipe products on:

• thin-walled - the coefficient varies in the range of 12.5-40;
• tolstoyed - the ratio above 6 and to 12.5;
• strengthened (particularly thick-walled) - the coefficient is 6 or less.

In the manufacture of pipes, it produces trimming of their ends at right angles, but in the process of cutting, the formation of the chamfer, which has an angle of at least 70 ° to the axis of the product. Cutting products with a thickness of a wall of 20 mm and above can be made by saw, autogen or plasma equipment. In the last two cases, the allowance for the length of the product should be at least 20 mm for each cut. At the ends of the pipes with a wall of 5-20 mm, to be welded, at the request of the consumer, chamfer takes place at an angle to the end of the product in 35-40 °. In this case, leave the end ring, which has a width of 1-3 mm.

The advantages of seamless hot-fixed pipes:

• durability and high reliability due to seamless manufacturing technology;
• excellent resistance to temperature drops;
• products from alloyed steels are less susceptible to corrosion processes.

The main disadvantage of the use of pipe products data is the appearance of corrosion, the distribution and impact of which can be partially reduced by different ways (For example, using anti-corrosion or other special coatings). In addition, deposits of substances, materials included in the composition of the liquid transported through the pipe can be formed on the inner surface, which leads to a decrease in the conditional passage of the product. These pipelines are needed thoroughly, as steel has a high thermal conductivity. It is especially important to do in case of street gasket in order to prevent the large energy losses of the coolant.

The advantages of thick-walled products:

• increased strength and durability;
• a small indicator of linear temperature expansion;
• the ability to choose products with thick walls.

If you compare the pipes are hotformed with seamless products produced by the method of cold deformation, then they are more fragile, but at the same time less degree Sounded corrosion.

3

The technology of connection of seamless pipes coincides with the methods of docking welded products. However, the difference in diameters and wall thickness determines a number of features. These parameters depends on the choice of the optimal method for producing a sealed connection of the elements of the pipeline from seamless articles.

Threaded docking can be used for systems of small diameter with the walls of normal thickness or thin. Cutting is produced on a lathe or with a dice. For thin-walled products, this technique is not always suitable, since the manufacture of threads of the required depth in some cases can lead to a disorders of the integrity or strength of the structure. Otherwise, the cutting process is facilitated due to the absence of a seam.

A number of requirements are made to pipeline systems, among which the priority is to ensure high reliability and strength. Most often the choice stops on hot-deformed seamless pipes that are able to demonstrate the indicated characteristics throughout the service life of their operation. These designs differ high technical characteristicsWhat is associated with the use of special technology to make them, which meets the requirements of the State Standard. Thanks to this, such execution pipes successfully cope with the task assigned to them and in difficult operating conditions.

Production of seamless hot deformation pipes

The raw material uses a blank bar round cross sectionwhich is placed in the furnace heated to high temperature. As steel processing, the steel acquires a plastic structure, which allows you to perform the necessary manipulations with it. According to GOST, the technology of manufacturing a full cylinder requires special firmwareThrough which the bar is passed. After that, the desired geometric dimensions are given a hot blank due to compression and pulling, for which a large number of rollers use.

Inside the workpiece, a mandrel is preserved, due to which the inner surface of the pipe does not deprive the initial geometric dimensions. The process of metalworking is completed by performing such an operation as a calibration, followed by cooling blanks and cutting into fragments of the desired length. The technology of manufacturing a cold deformed seamless steel tube is mostly similar to the production process above the considered method: before starting processing with rollers, the workpiece is cooled first, while at the end of the rolling it is subjected to additional heat treatment.

Pros and cons seamless steel pipes

Considering advantagesthat provides the technology of manufacturing these products, you need to mention the following:

However, on the background of hot-deformed seamless steel pipes Products manufactured by cold deformation exceeds the first strength and resistance to corrosion processes.

Scope of application

Seamless metal pipes Can be applied in a wide variety of areas, which depends primarily on their qualities. This should include excellent tensile strength, the absence of a seam, the impossibility of leaks and the possibility of creating products with particularly thick walls. Deserves the fact that wall thickness 75 mm It is not the maximum limit if we are talking about standard hot-deformed materials. A variant is possible when these structures also have non-standard sizes in respect of their wall thickness. For the manufacture of such pipes, it is resorted to the method of longitudinal drilling of blanks. A distinctive feature of such products is a high price.

The most widespread representation of seamless pipes received in the energy sector, in the construction of hydraulic systems, oil production, in shipbuilding and aviation, as well as the chemical and automotive industry.

Hydraulic cylinders Traditional designs have a look of pistons, the shell of which contains an oil supplied under high pressure, which causes the material to go out. The most common material for the piston is a stainless steel, and the product itself is necessarily subjected to polishing. The use of black steel is inappropriate due to the rapid coating of rust, which is associated with the interaction of the design with atmospheric air. If we talk about the hydraulic cylinder itself, it has the execution of a conventional seamless thick-walled pipe.

In power engineering where seamless pipes are very common, one of the key parameters is thickness of these structures. In this area, heat production is not the only task. In addition, it is necessary to configure the operation of the system so that the boiler gives it to heating the water in the heating industry or to rotate the turbine. The boiler contains such vulnerable parts such as screen and screens that, experiencing a constant effect of a very hot steam, can break.

All this suggests that it is precisely that it depends on whether the material can effectively deal with the load on the gap, and also how long it will serve until complete exercise. In the event of the need to open the boiler for repair work, it is necessary to deal with serious difficulties, both financial and physical. In addition to spending big costs of repair, no less expensive and stopping the supply of heat. For this reason, the choice in favor of seamless thick-walled pipes allows minimum costs.

In the field of oil production, the main activities concluded in drilling wells, the installation of the casing, the pumping of black gold and its delivery using the oil pipeline. Most often standard the depth of well begins from 100 metersThe used boring can cope with the rocks of any structure, and the casing used must effectively resist the movement of the soil. In addition to this, pump-compressor pipes must have the ability to cope with high pressure.

It is quite logical that the chemical industry was distributed along with thick-walled and thin-walled pipes. What are the purpose of which they are used? There are situations where during the polymerization of gases or oil refining, there is a need to ensure high pressure. And here laboratories have to deal with highly toxic drugs. Of course, such pipes do not have special tensile strengthHowever, in case of leakage, let and several molecules can lead to serious problems.

In such situations, seamless metal pipes come to the rescue: the lack of seams implies that there will be no leakage during operation. High demand thin-walled pipes enjoy in car, shipbuilding and aviation. This is due to such advantages that are characteristic of these products as minimal weight and strength. And the choice in their favor is quite logical, considering that with a small weight it is not necessary to spend more fuel.

Thus, seamless metal pipes used in many industries:

Product classification

According to GOST, all metal hot-deformed seamless pipes can be separated on the basis of such a trait as the ratio of wall thickness and outer diameter.

Due to the fact that in the sorting of the products under consideration are presented with structures having wall Thickness in the range from 2.5 to75 mm And the outer diameter is from 20 to 550 mm, they can all be classified into the following types:

• Thin-walled, for which the coefficient can be from 12.5 to 40.
• Tolstone, for which the coefficient can be equal to 6 to 12.5.
• Particularly thick-walled, for whom the ratio of up to 6 inclusive is characteristic.

Also, according to GOST, there is a classification, which is based on such a sign as the appointment and features of the technology used for the manufacture of technology. In accordance with it, these pipes are round and square section. For pipe blanks, separation is provided on cast, rod and wrought. For production purposes, they are supplied in the form of rods, as well as continuously billets or ingots.

In addition to this number of key factors, the accuracy of the geometry of the wall thickness and the outer diameter of the pipe should be attributed. Important for the manufacturer are quality indicators enshrined by the requirements of the State Standard on Registration chemical composition Steel and mechanical properties of metal rolling.

GOST REQUIREMENT 8732 78

If we proceed from the current requirements, then the separation of the measured and non-mechanical length is applied to the hot-deformed seamless steel pipes. At the regulatory level, possible deviations on the length of the product are fixed: up to 15 mm with a length greater than 6 meters or minimum diameter 152 mm. In some cases, it is not a disruption of a slight deviation of the wall thickness, but it all depends on the specific diameter of the pipe and the category of quality.

Steel Pipes Hot Formed Seamless Boiler

In the manufacture of products, designed under the conditions of supercritical indicators of temperature and pressure, manufacturers should not focus on GOST, but on specially designed technical conditions TU 14-3-460-75.

These structures were widely used when building pipelines for steam boilers. Raw materials for their manufacture usually served alloy and carbon steel.

Profile Hot Forded Seamless Pipes

According to GOST, the technology of manufacturing profile seamless pipes of hot deformation of a rectangular or square section provides for the use of special equipment necessary to perform operations such as squeezing and compression in the rolls of a blank having a circular cross section. The vast majority of similar products are used in the machine-building industry and different areas construction sphere.

According to GOST, for seamless profile metal products limitations are providedwhich are prohibited on their use in order to deliver liquid media.

Seamless hot-deformed pipes made of steel are available at different prices, which are determined by their external and internal parameters, quality level and other technical properties. These designs represent the category of expensive rolled products against the background of similar welded products, which is due to the peculiarities of the technological process.

For this reason, it is most often resorted to them during the arrangement of areas to which high demands in terms of reliability are presented. First of all, we are talking about the construction of highways chemical and oil and gas processing industrywhere thick-walled pipes are most in demand. According to GOST, the main sphere of use of thin-walled products is the construction of the trails in the field of housing and communal services.

How is the connection of seamless pipes?

Solving the question with the preferred method of combining products, the focus should be given to such a parameter as the wall thickness. According to GOST, if the designs have very thin walls, it requires great accuracy when performing installation work. If you have to deal with products that have no rolling threads, they are connected using a gas welding method.

According to GOST, the use of electric welding is possible only if there has been a specialist sufficient skills, knowledge and practical experience of such work. But it should be remembered that it is enough to make a small mistake, and an expensive design will already be not suitable for use.

In accordance with GOST, for threaded products, it is permissible to carry out a cutting with a lathe or manual method. Conducting similar works, you can not worry about what can damage the seam. Such a risk is excluded, since these products do not have a weld. Except here are only pipes characterized by the presence of very thin walls. The use of such a method increases the risk of cutting them through.

According to GOST, to the combination of structures with thick walls, by means of welding, you can start only at the end of the chamfer dismantling. Neglecting this advice can lead to the fact that the product will lose their former strength. Welding themselves should be carried out using electrodes of at least 4-ki. Resort to help gas burner It is considered unacceptable because it has weak efficiency.

Sortman

The sorting and standards of the products under consideration are among the important factors that need to be considered when choosing these products. All of them can be classify the following groups:

Conclusion

Hot-deformed seamless pipes got a lot of distribution in different areas, first of all construction and industry

One of the varieties of steel seamless pipes is. It is so called because it is obtained by the method of deformation heated to the high temperature of the steel workpiece. It can be hot rolling or hot pressing.

True hot-rolled produced on special pipe rolling mills. The general scheme of their production consists of 2 main operations:
1. Firmware operation. Here it turns out a thick-walled sleeve from a special solid blank;
2. Obtaining a pipe from a thick-walled sleeve. Here hot pipes Rolled to the desired size.
The first operation is performed on the firmware mills, and the second - on the rolling mills of various designs. In addition to the main operations, additional - finishing are performed. With their help hot pipes Get more accurate dimensions and cleaner surfaces. Sometimes they are required to reduce the diameter and wall thickness.

Tube seamless hot-focalled The following types are manufactured: general purpose, corrosion-resistant and special.

Hot focused general purpose pipes

Hot focused pipes (Abbreviated GD) General Purpose are issued on the basis. Technical requirements for the specified pipes determines.
GOST 8732-78 regulates the magnitude of the outer diameter, the wall thickness and the accuracy of these sizes.
True hot-rolledproduced with an outer diameter of 45 to 550 mm and with a wall with a thickness of 4 to 75 mm. The length of such pipes can be from 4 meters to 12.5 meters.
Steel pipeGOST 8732-78 comes in length, which is negotiated in the order.

Pipe seamlessGOST 8732-78 Depending on the quality indicators, the following groups are issued:
- Group A - with the normalization of mechanical properties. This group is made of steaks of St2Sp, St4sp, ST5SP, ST6SP;
- group B - with the normalization of the chemical station from calm stamps of steel, and;
- group B - with the normalization of mechanical properties and chemical composition from steel stamps according to GOST 1050-88, GOST 4543-71 and GOST 19281-89;
- Group G - with the normalization of mechanical properties from stories of GOST 1050-88, GOST 4543-71 and GOST 19281-89. Control is carried out on heat-treated samples;
- group D - without normalization of mechanical properties and chemical service, but with hydraulic pressure test.

Everything hot focused pipeswhich are designed to work under pressure are subject to hydraulic pressure test. They must withstand pressure up to 29 MPa (200 atm) inclusive. Besides pipe seamlessGOST 8732-78 passes the bending test according to GOST 3728-78. Pipe Art 09G2S.fully retains its strength even on strong frost. Therefore, such pipe DG Comes in the area of \u200b\u200bthe Polar North.
Steel pipeGOST 8732-78 takes a large stake on the markets of the pipes sold. Used tube seamless hot-focalled For laying pipelines carrying a large load and having a large internally pressure in the pipe itself. These are the main oil and gas pipelines and their taps, urban gas pipelines, gas supply and oil pipelines on fishery with a diameter of up to 530 mm.
Besides, pipe DG Used in mechanical engineering, shipbuilding, energy as blanks for the manufacture of various parts and nodes. Of them make hydro and pneumatic cylinders, rings, high-pressure cylinders and other similar details.

Steel pipe hot-fixed corrosion-resistant

Hot focused pipes From corrosion-resistant steels produced according to. This document determines the size, sorting, accuracy and technical requirements for hot pipes From corrosion-resistant steels. This standard provides a wide range of pipes with diameters from 57 to 325 mm and with walls with a thickness of 1.5 to 28 mm. The length of the pipes is provided from 1.5 meters to 10 meters.
As a material for this type of pipes, steel grades with himsows are provided. These are brands like: 08x13, 12x17, 12x18n10, 10x23n18, 12x18n9t.
GOST 9940-81 provides that pipes must have a mechanical properties defined for each brand.
Ready hot rolled trumpet Selectively exposed to tests for mechanical properties, on flattening according to GOST 8695-89. In addition, the pipe is tested by hydraulic pressure according to GOST 3845-75.
The main areas where applies pipe seamless hot rolled From corrosion-resistant steels - these are pipelines for aggressive media, as well as working at high temperatures. These are pipelines of chemical enterprises of oil refineries, nuclear power plants. In addition, they are used as blanks for the manufacture of different blood vessels and parts of metal structures that work at high temperatures and in aggressive environments.

Steel Tube Hot Formed Special

The following varieties include the following types:
- pipes for the oil refining and petrochemical industry;
- steel precision pipes;
- Pipes - workpieces for machining.

Steel pipe hot-focused For the oil refining and petrochemical industry are manufactured by software.
According to this standard, two groups are available:
- A group A - pipes are produced entirely according to GOST 550-75;
- A group B - pipes on the sorting and sizes come according to GOST 8732-78, and technical requirements are performed according to GOST 550-75.
Pipes of group A are produced by diameters from 20 to 219 mm, where the walls can be thick from 2 to 25 mm. In length, you can order pipes with a length from 4 to 12.5 meters. Pipes of a group B according to GOST 550-75 are produced from steel stamps 10, 20, 09g2c, 10g2, 12xm, 15x5m, 12x8VF, 12x8, 1x2m. Pipe Art 09G2S.one of the representatives of such pipes.
These pipes are subjected to strict control. Samples are taken from the batch of pipes and are subject to tests for mechanical properties, a metal microstructure and hydraulic pressure. All these tests are conducted on the basis of the relevant standards. These pipes are used on oil refineries in boilers and pipelines, high-pressure steam and in the petrochemical industry for cracking oil products.

Pipe DG Steel precision is produced based on. This is a pipe of increased accuracy. That is, its wall thickness and outer diameter are performed more precisely than steel pipeGOST 8732-78. The outer diameter of these pipes is performed from 25 to 325 mm, and the walls with a thickness of 3 to 45 mm. Pipe length from 1.5 to 11 meters. This pipe is used as a blank for the manufacture of hydraulic and pneumatic cylinders, pistons, rings and other parts operating under pressure in various mechanisms and machines.

Pipes - workpieces for machining are manufactured by software. This document determines the size, the sorting and accuracy of the manufacture of these pipes. The outer diameter of such pipes ranges from 42 mm to 325 mm. Walls in thickness from 3 to 40 mm. In this case, the length of the pipe can be from 1.5 meters to 11.5 meters. The limit deviations on the thickness of the wall, the outer diameter and the length of the pipe are set exactly the same as pipe seamlessGOST 8732-78.
Steel pipe hot-focused - The workpiece for machining is made of steels of brands: 10, 20, 35, 45, 30xgs, 30khma, 09g2c, 10g2, 15x, 40x, 15xm, 38x2mia. An example of such a pipe can serve pipe Art 09G2S.. Finished pipes are tested for compliance with the declared chemical service, mechanical properties, microstructure of metal. True hot-rolled Must be checked for hidden defects non-destructive testing methods.

As can be seen from the name, such pipes are used as blanks for the manufacture of parts on metal-cutting machines and stamping presses. Of these, it makes such details like: glasses, cylinders, rings, fitting, nozzles. The use of pipes helps reduce time on mechanical processing in the manufacture of parts and reduce metal consumption. And this is to reduce the cost of production.

Order seamless hot-focused.