All about steel pipes: an overview of technical specifications and mounting nuances

In industry and household, steel pipe is used very widely. It is used when laying closed and open communications supplying gases and liquids to distribution stations. With the help of steel products, they protect power and signal cables in the aircraft and automotive industries.

Steel pipes in a number of areas serve as structural and decorative elements. In everyday life, water and heating systems are assembled from them. The products have high physical characteristics, withstand significant operational loads and reliably serve for many years.

Steel grades for production

In the manufacture of steel pipes in industrial production, such types of raw materials are used as:

• carbon steel st 3, st 10-20, st17g1s-u - for general-purpose electric-welded universal pipes;
• steel 20-10 - for the manufacture of hot-rolled pipes without a seam;
• steel 20 - for pipe material of cold deformation;
• Corrosion-resistant steel 12X18H12T, 12X18H10T, 08X18H10T - for pipes in demand in the energy and chemical industries.

Low alloy steel has good mechanical properties and an affordable price. Alloying additives positively affect the physical characteristics of steel, improve toughness and ductility, make the material more durable and resistant to high temperatures and atmospheric corrosion.

However, the cost of alloy steel is slightly higher and pipes made from it are always valued slightly more expensive. According to the level of alloying, steel is divided into three classes.

Seamless alloy steel pipes ensure perfect integrity of the pipeline, do not require painstaking maintenance work and minimize potential leakage

The low alloyed material in the composition contains no more than 2.5% of various additives. In medium-alloyed species, this indicator ranges from 2.5-10%. In highly alloyed grades, the amount of components that improve the basic properties of the metal is from 10 to 50%.

In total, there are 14 types of high alloy steel alloys with different characteristics. The most popular materials are those that exhibit good resistance to various corrosion phenomena and are able to work efficiently without destroying the structure at extremely high temperatures.

Steel pipe manufacturing: basic methods

Steel pipes are made in several ways.

The most common manufacturing options are:

• electric welded with a straight seam;
• electrowelded with a spiral seam;
• hot deformed without a seam;
• cold rolled seamlessly.

The selection of a suitable metal processing method depends on the quality of the raw materials and equipment available from the manufacturer.

A separate standard regulates water and gas pipes. However, this does not happen because there is a special manufacturing method for this material, but only based on the field of application.

In fact, this type of pipe is a universal electric welded product with a straight seam. Usually this type is used in communication systems with moderate pressure.

How do electric-welded longitudinal seams?

Rolled up in a tight roll, a steel sheet (strip) is unwound and cut into longitudinal strips of the desired length and width. The resulting fragments are welded into an endless strip, thus ensuring continuity in production.

Then the tape is deformed in the rollers and the blank is turned into a product of circular cross section with open edges. The connecting seam is boiled by an arc method, induction currents, plasma, laser or electron beams.

The seam on a steel pipe, made in an inert gas environment with a tungsten electrode (an active element of electric arc welding), is quite strong and durable. However, processing takes a long time. Welding pipes with high-frequency induction currents is almost 20 times faster, therefore the price of such products is always much less

After all the manipulations, the round steel pipe is calibrated in the rollers and delicate non-destructive testing of the strength and integrity of the weld is carried out with ultrasound or eddy currents. If during testing no errors were found, the workpiece is cut into fragments of the planned length and sent to the warehouse.

Production of electric-welded spiral-seam types

The production of steel spiral pipes takes place on the same principle as straight-seam pipes, only simpler mechanisms are used for the manufacture of products. The main difference is that the cut steel strip with the help of rollers is rolled up not with a tube, but with a spiral. This ensures high precision joints at all stages.

On pipes with a spiral seam, in case of an emergency, a longitudinal longitudinal crack does not form, recognized by specialists as the most dangerous deformation of any communication system

The spiral seam is considered more reliable and gives the pipe increased tensile strength. The disadvantages include the increased length of the seam, requiring additional costs for welding materials and more time for joining.

Production of hot-deformed seamless products

As a preform for creating a seamless (seamless) steel pipe by hot deformation, a monolithic preform of a cylindrical shape is used.

It is heated at high temperature in an industrial furnace and driven through a piercing press. The unit turns the product into a sleeve (hollow cylinder), and subsequent processing with several rollers gives the element the desired wall thickness and a suitable diameter.

The wall thickness of the pipe material from steel made by hot deformation reaches 75 mm. Pipes of this quality are used in difficult operating conditions and in communication systems, where durability and reliability are the main priority.

At the last stage, the hot steel pipe is cooled, cut according to the specified parameters and transferred to the finished goods warehouse.

Features of the production of cold-deformed pipes

The initial stage of the process of manufacturing seamless steel pipes by cold deformation is identical to the “hot” version. However, after sweeping through the piercing mill, the sleeve is immediately cooled and all other operations are carried out in a cold environment.

When the pipe is fully formed, it is necessarily annealed, first warming up to the temperature of recrystallization of steel, and then cooling again. After such measures, the viscosity of the structure increases, and the internal stresses that inevitably arise during cold deformation leave the metal itself.

Of steel pipes produced by cold deformation, a communication system of high reliability can be laid in which the risk of leaks will be minimized

Now on the market there are seamless cold-rolled pipes having a wall thickness of 0.3 to 24 mm and a diameter of 5 to 250 mm. Their advantages include a high level of tightness and the ability to withstand high pressure.

Section and Coating Types

According to the type of cross section, steel pipe elements are divided into round and profile. Round ones belong to the universal look, have the widest gradation in diameter of the hole and wall thickness.They are made only in industrial conditions from steel alloys and various additives that enhance the physical characteristics of the material.

A practical and beautiful canopy can be made from a polished steel pipe with a round cross-section, which will preserve an attractive appearance for a long time and protect the entrance from precipitation

The range of applications covers almost all industrial and domestic areas. Round steel pipes of different diameters are used for transporting oil and gas, for the equipment of reliable insulation of communication systems of any complexity and size, for creating light structures and various elements of the external and internal decor.

Profile pipes are a progressive type of construction metal rolling with an oval, square or rectangular section. It is produced from low alloy and carbon steel, less often from stainless steel, by cold or hot deformation of a straight-seam round-gauge electrically welded billet.

Forming is carried out by passing the part through the rolls, which provide the necessary section.

Metal pipes of various types and purposes are constructed from pipes with a profile cross-section, carcasses of buildings, supports, complex interfloor and span ceilings are mounted. The structures withstand significant physical, vibrational and mechanical loads, reliably serve for many years and are suitable for intensive use in any atmospheric conditions.

Finished steel pipes are checked for the integrity of the weld and subjected to additional heat treatment, which allows you to remove internal mechanical stress. Then cut in accordance with the required dimensions. To improve the physical properties of steel pipes, a protective coating is applied to them.

The most popular types include:

• zinc (cold or hot);
• polyethylene multilayer or extruded;
• epoxy bitumen;
• cement and sand.

Zinc protects the pipes from corrosion, polyethylene creates a dense, impermeable layer on the surface and prevents the destruction of the metal structure, bitumen-epoxy reduces the influence of stray currents, and cement-sand protects the inner surface from biological fouling.

Steel pipe standards and sizes

For pipes made of steel, there are special standards and state standards. These parameters describe the method of manufacturing the product, its basic dimensions, cross-section and wall thickness. Focusing on this information, the area of ​​use of a particular part is determined.

Parameters for straight weld products

The production of electric welded pipes with a straight seam is regulated by GOST 10704-91. According to his information, the outer diameter of the product is 10-1420 millimeters, and the wall thickness varies from 1 to 32 millimeters.

The fittings, not exceeding 426 millimeters in diameter, have a measured and unmeasured length.In special cases, pipes with a stronger, reinforced seam are made, but for them there is a separate special standard - GOST 10706.

Steel welded pipes with a straight seam - a versatile material with a wide range of applications. Decent quality and low price make their use relevant both on large-scale facilities and in everyday life

Pipes of this type are most often used for laying technological communication systems with moderate pressure and creating practical, convenient and lightweight metal structures for various purposes.

Regulation for electric-welded spiral seam pipes

The production of electric-welded pipes with a spiral seam is carried out in accordance with GOST 8696-74. The outer diameter of such products is 159-2520 millimeters, the wall thickness ranges from 3.5 to 25 millimeters, and the length is 10-12 meters.

Electric welded pipes with a spiral seam are more expensive than their longitudinal joints. However, the costs are justified, especially if the system requires a perfectly accurate, perfect connection

Pipes made in this way are more durable and have the ability to withstand high pressure. The standard allows them to be used both for domestic and industrial purposes, to create reliable, airtight and operationally stable communication systems.

Hot Deformation Seamless Product Requirements

Standards for seamless hot-deformed pipes are described in GOST 8732-78. The thickness of their walls is 2.5-75 millimeters, and the diameter varies from 20 to 550 millimeters. In length, both measured and unmeasured, the size ranges from 4 to 12.5 meters.

Seamless pipes made by hot deformation are practically not used in everyday life. Most often they are used for industrial systems with increased requirements for reliability and tightness.

Pipes of this type are used to transport highly toxic substances for chemical production. The absence of a seam guarantees the impossibility of leakage and the ingress of harmful substances into the earth or atmosphere.

The ability to easily withstand constant high pressure makes seamless pipes relevant for the oil and gas industry.

Standards for cold formed seamless pipes

Cold-rolled steel pipes are manufactured in accordance with GOST 8734-75. The outer diameter of the reinforcement varies from 5 to 250 millimeters, and the wall thickness is 0.3-24 millimeters. Products are produced in unmeasured lengths from 1.5 to 11.5 meters and measured lengths from 4.5 to 9 meters.

Thick-walled seamless cold-rolled steel pipes are used in the same way as hot-rolled ones. And thin-walled are most often used where a combination of impeccable strength and low weight is necessary (aircraft industry, shipbuilding, etc.)

Seamless steel pipes created by cold deformation demonstrate high strength, operational stability and reliability throughout the entire period of use.

Features and characteristics of water and gas products

Gas and water pipes are produced according to the regulations of GOST 3262-75. In a separate standard, this type of metal is isolated only because of a narrower scope.

The outer diameter of the product is 10.2-165 millimeters, and the wall thickness ranges from 1.8-5.5 millimeters. The size range for unmeasured and measured length is the same - from 4 to 12 meters.

Water and gas pipes are mainly used for their intended purpose: for the organization of water and gas communication systems. Sometimes they are used to create lightweight structures or used in the furniture industry for the manufacture of stylish items of interior decor

The standard provides for the production of not only ordinary, but also galvanized water and gas pipes.

Installation of steel pipelines: basic methods

The process of assembling a reliable, durable and well-functioning communication system from steel pipes requires significant labor costs, a lot of time and the presence of specific professional tools.

The division of the material into segments of the required length is carried out using pipe cutters. The connection is usually made in three ways: by welding, threaded and flange methods.

Welding connection

The installation of pipes with the subsequent connection of all parts using gas or any other welding is considered the most simple, practical and affordable installation method.

A system equipped in this way is characterized by a high level of tightness, withstands significant operational and vibration loads, does not require serious maintenance measures and is easily repairable in case of a problem.

A communication system formed from steel pipes connected by welding will last at least 40 years and ensure perfect structural integrity that prevents liquids and unpleasant odors from seeping through the seams.

If the laying of communications is carried out in difficult conditions or inaccessible places and welding is physically impossible, a threaded (fitting) or flange method of connecting the necessary parts is used.

Thread fit

In this embodiment, the pipes are screwed onto the thread using fittings of different types and destination. This allows in the future to carry out local repair work and eliminate the breakdown in a particular place without resorting to dismantling the entire communication system.

Connection fittings are available in a wide variety of shapes and configurations. This makes it possible to mount with their help a system of any complexity with a large number of turns and branches

The main advantage of the threaded method installation of heating system or water supply is simplicity and accessibility. To create the desired structure from steel pipes and fittings, specific equipment, professional knowledge or extensive experience in repair work is not required.

All work is intuitive and easy to do even by people who do not have the appropriate qualifications. Steel pipe thread You can cut it yourself. The technology recommended by us will familiarize you with the technology.

System construction using flanges

Another way to connect steel pipes into a common communication complex involves the use of flanges of various shapes and configurations (crosses, corners, couplings, etc.). These parts are welded to the edges of the pipes, bolts of a suitable caliber are inserted into the holes, and nuts are screwed on them, making a clear fastening.

A seal is always required between the nut and the bolt. For the system responsible for supplying hot and cold water (maximum temperature up to 100 degrees), gaskets made of thick (about 3 mm) cardboard are used.

When flanging steel pipes, it is very important to tighten the nuts tightly, without causing the skew of the entire structure. To avoid this problem, it is necessary to carry out the final screwing not in the order of placing the bolts around the circumference, but to fix in turn the nuts opposite to each other

First, the part is moistened with water and dried dry. Then impregnated with heated drying oil for 25-30 minutes. After this procedure, the gasket acquires the desired structure and serves for a long time even in conditions of heavy use.

For communications serving coolant increased temperature (up to 450 degrees) and a base pressure of up to 5 MPa, gasket material from paronite is used. For systems transporting steam with a pressure of up to 0.15 MPa, thick (about 3-6 mm) asbestos board with a dense structure and good flexibility is used for compaction.

In order for the asbestos gasket to last longer, it is preliminarily coated with a graphite compound made on the basis of natural drying oil.

So that the asbestos gasket does not “eat up” the useful area inside the pipe and does not abut against the outer bolts, its outer and inner diameters should be 2-3 millimeters smaller than the outer and inner diameters of the flange used

For the correctness of the flange connection, the heads of all working bolts are placed on one side, being careful that the ends of the bolts protrude from the nuts by no more than half the diameter of the bolt.

Screwing of bolts and nuts is carried out with the most ordinary wrench or adjustable wrench. Disassemble the structure using the same tools, alternately unscrewing the nuts and bolts. If any of the parts is rusty and cannot be removed, they hammer it out with a hammer.

When hammering rusty connecting elements under the bolt, it is necessary to substitute a strong wooden lining, so as not to violate the integrity of the thread

Damaged during operation, the gasket is cut with a chisel and a new part is put in its place. During dismantling, they act very carefully and carefully so that the part left without fasteners does not fall on the worker and cause harm to him.

Conclusions and useful video on the topic

Basic instructions for working with steel pipes for beginners. Useful tips and tricks of installation.

The video shows in detail how to weld steel pipes in different positions. Secrets and principles of work are shared by professional welders.

Different ways to connect steel pipes: interesting nuances and recommendations for home craftsmen.

Knowing exactly the assortment of steel pipes on the market, one can easily select product options that are ideally suited to form the necessary communication system.

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