Steel pipes, use of steel pipes in sanitary engineering. The specifics of the use of steel pipes

Metal pipes mean hollow metal products with a round, square or other profile section. They are used in various industries and utilities. Steel pipes are produced in a wide range. You can choose them with different wall thicknesses. The cost of production depends on this indicator. It is already profitable to buy rolled products at the price per meter on the Maxima Metal Service website. The pipe steel is released wholesale with delivery across Ukraine. In Dnipro, you can also buy a rental product at retail.

Product classification

Metal pipes are produced using two technologies: electric-welded and seamless. The latter are obtained by rolling according to the method of hot and cold deformation. Seamless pipes are more reliable and durable. They are able to provide high level tightness, resistant to loads. Used in the oil industry, the construction of underwater pipelines, machine production. Electric welded joints differ in types according to the type of connection: straight and spiral joint. They have found application in the organization of household and industrial pipelines, are used in the creation of metal structures.

In addition, there are:

• galvanized;
• profile (with a square or rectangular section);
• water and gas types.

The first differ in the way the surface is treated. The application of zinc makes metal pipes resistant to corrosion and aggressive environments. Their service life exceeds that of conventional products by 5 times. The angular shape of profiled rolled products gives them increased strength. The walls play the role of stiffeners, withstand heavy loads. Water and gas pipes are manufactured in accordance with GOST 3262–75 and are used to organize utility networks.

Applications

Metal pipes are a universal rolled product. They are used in many industries:

• construction;
• machine, aircraft and shipbuilding;
• furniture manufacturing;
• organization of communication systems.

They are widely used in the private sector in the construction of fences, partitions, load-bearing frames for temporary structures - the scope depends on the class and type of metal pipe. When choosing, you should focus on the following parameters: the shape of the section, the length of the rolled product, the wall thickness (the larger it is, the more durable the part in relation to physical activity). Metal pipes are in active demand among industrialists and private customers. The reasons for this popularity are practicality and excellent performance: strength, long service life and endurance of products. Metal pipes have a small specific gravity, so they do not weigh down the structure. They are resistant to rather high mechanical and dynamic loads, which allows them to be used when laying pipelines.

The beginning of the production of steel pipes dates back to 1825, from the moment when butt welding was used for the manufacture of thin-walled gas and water pipes small diameter (20 - 50 mm) from mild steel (

Furnace butt welding has long been the only way production of steel pipes. In 1899, seamless pipes were produced. The new production developed at such a pace that already in 1910, seamless pipes of various sizes were produced on pilgrim, rack and automatic mills. It rendered positive influence for the development of mining, energy, construction and other industries.

Seamless pipes are superior in quality to welded pipes, since they can be made from steel with higher strength properties than low-carbon steel and with a greater wall thickness.

The problem of the quality of seamless pipes was solved by an intensive search for more advanced designs of pipe mills and production methods. During the period from 1910 to 1939, several new production methods were introduced as a result of the development of continuous mills, three-roll rolling, two-roll screw rolling mills with rotating wires and tube presses.

Significant progress in the production of pipes was noted in the thirty years after the Second World War. Many pipe mills have been built, inventions and improvements have been introduced in the production of both seamless and welded pipes.

For the production of seamless pipes, the following are used: rotary hearth furnaces for heating blanks, as well as sectional furnaces for heating pipes before reduction; a two-operational method for producing pipe sleeves, first by piercing on a press, and then by rolling on an elongator to reduce the difference in wall thickness of the sleeves; sizing or reduction mills that reduce the deviation of pipe diameters; continuous method of non-destructive quality control of pipes.

In the production of steel pipes greatest development received a method of arc welding under a layer of flux and in an atmosphere of protective gases. As a result, welded pipes are not inferior in quality to seamless ones, and their cost and investment are even much lower. This explains the intensive construction of pipe welding plants at the present time. It is possible to obtain thin-walled pipes by welding, which is economically advantageous and impracticable by hot rolling methods. AT recent times In world practice, there is a tendency to expand the production of welded and reduce the production of seamless pipes, especially for drilling, boiler and structural pipes.

1. APPLICATION OF STEEL PIPES IN THE SPHERE OF PRODUCTION AND CONSUMPTION

The pipe industry produces a wide range of products with a variety of technical and operational characteristics, which allows them to be used in various sectors of the national economy:

In the oil and gas industry for drilling, casing and operation of oil and gas wells, for the transportation of oil and gas and other technological needs, both seamless pipes and pipes with a seam are used. For their manufacture, carbon, low-alloy and alloy steels are used. If necessary, the pipes are subjected to heat treatment and special types of finishes;

For power engineering, seamless pipes are made from high-quality and high-quality steels. Pipes capable of withstanding high vapor and liquid pressures have specified properties at operating temperatures;

In mechanical engineering, welded and seamless pipes of almost all standard sizes are used from steel of all grades produced by the pipe industry;

AT agriculture and industrial construction use seamless and welded pipes for the installation of irrigation systems, various kinds of communications, pipelines made of carbon and low alloy steels;

The chemical industry uses pipes with special performance properties that ensure operation in aggressive environments in a wide range of pressures and temperatures. The pipe material has a high resistance to corrosive media.

2. CLASSIFICATION FEATURES OF STEEL PIPES

The main types of steel pipes consumed can be divided into two main groups according to the method of their manufacture: seamless and welded. Seamless pipes are produced as hot-rolled and cold-rolled, cold-formed in cold and warm states, pressed and cast. For the manufacture of welded pipes, units for continuous furnace welding (for pipes with a diameter of up to 144 mm), high-frequency current welding (D T 530 mm), arc welding (straight-seam pipes D T 1620 mm and spiral-seam pipes D T 2500 mm) are used. Pipes from alloyed and high-alloyed steel grades are made on electron beam welding mills. Work is underway to create units for plasma welding, laser beam and other methods.

According to the profile of the pipe section, round and shaped, oval, rectangular, square, three-, six- and octahedral, ribbed, segmental, teardrop-shaped and other profiles are distinguished. The outer diameter of the pipes is 0.3 ... 2520 mm and the wall thickness is 0.05 ... 75 mm. According to the size of the outer diameter of the pipe, they are divided into the following groups, mm:

Small sizes (capillary) 0.3 … 4.8

Small sizes 5 … 102

Medium sizes 102 … 426

Plus size >426

Depending on the ratio of the outer diameter to the wall thickness, the pipes are divided into the following groups:

Extra thick-walled 5.5 0.18

Thick-walled 5.5…9 0.18…0.12

Normal 9.1…20 0.12…0.05

Thin-walled 20.1…50 0.05…0.02

Extra thin-walled >50

According to the longitudinal section, pipes are conical, stepped with upset ends, etc. In a separate group there are bimetallic and trimetallic pipes, consisting of two and three layers of metal, firmly connected by fit, welding or fusion.

Depending on the purpose, the following main types of pipes are distinguished.

I. Pipes for the oil and gas industry: drilling, casing, tubing.

II. Pipes for pipelines: water and gas pipelines, oil pipelines are made seamless and welded.

III. Pipes for construction, used in industry and civil engineering, are made mainly welded.

IV. Pipes for mechanical engineering are used seamless, made of carbon, alloyed and high-alloyed (corrosion-resistant and heat-resistant) steels.

V. Pipes for vessels and cylinders used in shipbuilding, aviation, nuclear, medical industry and other sectors of the national economy are made of carbon and alloy steel. Stainless steel cylinders are supplied according to specifications.

Steels used for the manufacture of pipes are very diverse. They are made from more than 350 steel grades: all carbon grades, a number of alloyed and high-alloy steels (chromium-molybdenum, chromium-nickel, corrosion-resistant manganese, heat-resistant), from various alloys.

Due to the fact that the range of steel pipes is quite extensive, I chose the most widely used type of pipes according to GOST 3262-75 (01.01.1977) “Steel pipes for water and gas supply. Specifications».

This standard applies to non-galvanized and galvanized steel welded pipes with threaded or knurled cylindrical threads and without threads used for water and gas pipelines, heating systems, as well as for parts of water and gas pipeline structures. Pipes of this type are manufactured according to the dimensions and weight given in table 1.

Conditional passage, mm	Outer diameter, mm	Pipe wall thickness, mm			Weight of 1 m of pipes, kg
			ordinary	reinforced		ordinary	reinforced

At the request of the consumer, light series pipes intended for thread rolling are manufactured according to the dimensions and weight given in Table 2.

Conditional pass	Outside diameter	Wall thickness	Weight of 1 m of pipes, kg

Notes:

1. For a thread made by knurling, a reduction in its inner diameter of up to 10% along the entire length of the thread is allowed on the pipe.

2. The mass of 1 m of pipes is calculated with a steel density of 7.85 g / cm 3. Galvanized pipes are 3% heavier than non-galvanized ones.

Along the length of the pipe, steel water and gas pipelines are made from 4 to 12 m:

a) measured or multiple measured length with an allowance for each cut of 5 mm and a longitudinal deviation for the entire length plus 10 mm;

b) unmeasured length.

By agreement between the manufacturer and the consumer, up to 5% of pipes with a length of 1.5 to 4 m are allowed in a batch of off-gauge pipes.

Limit deviations in pipe dimensions should not exceed those indicated in Table 3.

Notes on Table 3:

1. The maximum deviation in the plus side along the wall thickness is limited by the maximum deviations in the mass of pipes

2. Pipes of ordinary manufacturing accuracy are used for water pipes, gas pipelines and heating systems. Pipes of increased manufacturing accuracy are used for parts of water and gas pipeline structures.

Maximum deviations in the mass of pipes should not exceed + 8%.

At the request of the consumer, the maximum deviations in mass should not exceed:

7.5% - for the party;

10% - for a single pipe.

The curvature of pipes per 1 m of length should not exceed:

2 mm - with nominal bore up to 20 mm inclusive;

1.5 mm - with nominal bore over 20 mm.

Pipe threads can be long or short. Thread requirements shall be as specified in Table 4.

Conditional passage, mm		Thread length to the run, mm		Conditional passage, mm	Number of threads with conditional passage	Thread length to the run, mm
			short				short

In the Republic of Belarus, there are two official classifiers: "Commodity Nomenclature of Foreign Economic Activity" (TN VED) and "National State Classifier of the Republic of Belarus" (OK PRB).

TN VED is a single language for all states in the field of trade. It is built on the basis of the nomenclature of the harmonized commodity description and coding system (HCS) and the combined nomenclature European Union(KN EU) and put into effect in 1993 in the Republic of Belarus. The structure of the TN VED consists of a code designation of goods, namely, nine decimal digits, of which the characters from the first to the sixth correspond to the code designation according to the NHS, the seventh and eighth correspond to the designation according to the EU CN, the ninth character is still zero (it is intended to highlight national goods ):

OKP RB is designed to create a single information language that provides comparability of data on products of the Republic of Belarus, taking into account international classifications in automatic information processing systems when coding industrial and agricultural products. It uses a hierarchical method with six classification levels and one intermediate level. The OKP RB uses a hierarchical classification method and a sequential coding method.

Using the TN VED and OKP RB, we encode this product.

Code according to TN VED.

Section IV. Base metals and products from them.

Group 73. Products from ferrous metals.

Position 73.06. Pipes and tubes, other hollow sections (for example, open-seam or welded, riveted or similarly joined) of iron or steel.

Subposition 73.06.10. Pipes for oil and gas pipelines

Subheading 73.06.10.110. Longitudinally welded pipes for oil and gas pipelines with an outer diameter of not more than 168.3 mm.

Encoding according to OKP RB.

Section D. Products of the processing industry.

Subsection DJ. Base metals and finished metal products.

Section 27 Base Metals.

Group 27.2. Pipes.

Class 27.22. Pipes and fittings for pipes of ferrous metals, except for foundry iron.

Subspecies 27.22.10.550. Welded, riveted or similarly connected pipes, tubes and hollow sections of steel, round section with an outer diameter not exceeding 406.4 mm or non-circular section.

3. CONSUMER PROPERTIES OF STEEL WATER AND GAS PIPES

Pipes are only supplied in accordance with state standards and technical conditions. Industry, republican and other types of standards for pipes are not applied. At the same time, more than 70% of pipes are produced in accordance with GOSTs, which, in turn, determine the consumer properties of the latter.

Steel water and gas pipes are manufactured in accordance with the requirements of GOST 3262-75 (01/01/1977) and according to technical regulations approved in the prescribed manner, without standardization of mechanical properties and chemical composition. However, pipes must have a number of characteristic properties, namely strength, hardness, heat resistance, corrosion resistance and a number of other properties that determine the effectiveness of their intended use, social significance, practical usefulness and safety.

STRENGTH is the ability of a material to resist destruction, as well as irreversible change in shape (plastic deformation) under the action of external loads, in a narrow sense - only resistance to destruction. The strength of solids is ultimately determined by the forces of interaction between the atoms and ions that make up the body. Strength depends not only on the material itself, but also on the type of stress state (tension, compression, bending, etc.), on operating conditions (temperature, loading rate, duration and number of loading cycles, environmental effects, etc.). Depending on all these factors, various strength measures have been adopted in technology: tensile strength, yield strength, fatigue strength, etc. An increase in the strength of materials is achieved by thermal and mechanical treatment, the introduction of alloying additives into alloys, radiation exposure, the use of reinforced and composite materials.

BENDING - a type of deformation characterized by a curvature (change in the radius of curvature) of the axis or middle surface of an element (beam, slab, etc.) under the influence of an external load or temperature. There are bends: pure, transverse, longitudinal, longitudinal-transverse. Pure bending is possible if the transverse dimensions of the body are small compared to the longitudinal ones. When bending, there are no sharp changes in cross sections.

EXTENSION-COMPRESSION - deformation under the action of forces, the resultant of which is directed along the axis of the centers of gravity of the cross sections. Forces can be applied at the ends or distributed along the length.

HARDNESS - The resistance of a solid body to indentation or scratching. In indentation, the hardness is equal to the load applied to the surface of the imprint.

ELASTICITY - the property of bodies to restore their shape and volume (solids) or only volume (liquids and gases) after the termination of action external forces. Quantitative characteristic elastic properties of materials - moduli of elasticity. Elasticity is due to the interaction between atoms and molecules and their thermal motion.

IMPACT TOUGHNESS - the ability of a material to absorb mechanical energy in the process of deformation and destruction under the action of an impact load.

HEAT CAPACITY - the amount of heat that must be supplied to the body in order to increase its temperature by 1 K, more precisely, the ratio of the amount of heat received by the body (substance) with an infinitesimal change in its states in any process to the temperature increase caused by it. The heat capacity per unit mass is called the specific heat capacity.

HEAT RESISTANCE - the ability of structural materials (mainly metallic) to withstand mechanical loads at high temperatures without significant deformation. It is determined by a set of properties: creep resistance, long-term strength and heat resistance.

CORROSION RESISTANCE - the ability of materials to resist corrosion. For metals, it is determined by the corrosion rate, i.e., by the mass of material converted into corrosion products, from a surface unit per unit of time, or by the thickness of the destroyed layer in mm per year. An increase in corrosion resistance is achieved by alloying, applying protective coatings, etc.

EROSION RESISTANCE - the destruction of the surface layers of metal products as a result of the mechanical action of the flow of gas, liquid, solid particles, as well as during cavitation phenomena or under the influence of electrical discharges (electroerosion). Some types of metal erosion are used for their electroerosive processing.

100% quality control of the weld and pipe wall metal by non-destructive testing methods contributes to improving the reliability of pipelines.

The widespread use of welded pipes for the construction of water and gas pipelines is facilitated by their lower cost (by 15 ... precision welded pipes. All this ensured their large share, which is 60% in the world production of pipes.

4. TECHNOLOGY OF PRODUCTION OF STEEL WATER AND GAS PIPES AND ITS TECHNICAL AND ECONOMIC ASSESSMENT

Pipes for parts of water and gas pipeline structures are made from steel. In turn, steel is obtained from cast iron, and cast iron itself consists of various components.

For simplicity and convenience, I will describe the production technology point by point and in a strictly defined order.

4.1. Getting pig iron

Cast iron is the main raw material for steel production. About 90% of it is converted to steel.

Cast iron is a brittle material, because it contains a lot of carbon and therefore products from it are obtained only by casting.

For the production of pig iron, a mixture is used (a mixture of raw materials taken in a certain amount).

To obtain a charge, use:

Iron ores (magnetic, brown, red and spar iron ore) - are used to obtain iron;

Fuel (coke) - used to create the required temperature, must have high calorific value, porosity, strength, low ash content, minimum sulfur content, in addition, it must have low humidity and maximum carbon content;

Fluxes - serve to lower the melting point of the waste rock.

Pig iron is produced in blast furnaces.

Stages of iron production:

1. Burning coke.

2. Iron recovery:

a) indirect reduction of iron;

b) direct reduction of iron;

c) carburization of iron.

3. Recovery of silicon, manganese, phosphorus.

4. Sulfur removal.

Thus, the products of blast-furnace production are:

Domain gas.

4.2. Steel production and its characteristics

The composition of the charge for steelmaking:

1) cast iron: liquid and solid form (pig iron);

2) steel and iron scrap (scrap);

3) iron ore;

4) waste of own production;

5) fluxes (lime, calcium carbonate, dolomite);

6) fuel: gaseous, liquid (fuel oil, tar), solid (coal dust), electricity;

7) oxidizing agents.

Steel production stages:

1) transfer of oxygen from an oxidizing atmosphere to the metal;

2) carbon oxidation - the main reaction of steelmaking;

3) oxidation and reduction of impurities (silicon, manganese, phosphorus);

4) removal of sulfur;

5) steel deoxidation: deoxidizers are introduced for this.

The steel used for the production of water and gas pipes complies with GOST 380-94 (01.01.2007) “Ordinary quality carbon steel” and GOST 1050-88 (01.01.1991) “Rolled bars, calibrated, with a special surface finish from high-quality carbon structural steel . General technical conditions".

Of the total production, up to 90% is carbon steel.

Carbon steel is an alloy of iron and carbon that does not contain any specially introduced additives (alloying elements).

Permanent impurities: sulfur and phosphorus, manganese and silicon.

In various grades of carbon steel, the content of carbon itself is in the range of 0.06 - 1.35%. A change in the carbon content greatly changes all the properties of steel, and therefore, according to the quantitative content of carbon, steels are divided into:

Structural (

Instrumental (> 0.8% carbon).

Structural steel is called steel, suitable for the manufacture of various parts of machines and structures.

It should have a complex of high mechanical properties, i.e. must be sufficiently strong and ductile, must have high technological properties, i.e. it is good to be processed by pressure, it is good to cast, it is good to be welded, because products of complex shape are made from it.

Structural steel is used in very large quantities, therefore, it is desirable that it be cheap both in composition and in the method of production.

Depending on the amount of carbon, structural steel is divided into 2 types:

1) steel of ordinary quality;

2) quality steel.

Carbon structural steel of ordinary quality is produced hot and cold rolled in the form of blanks from continuous casting plants (in the form of pipes, strips, wires). It is produced by oxygen-converter and open-hearth methods.

High-quality structural carbon steel differs from ordinary quality steel in a narrower limit of carbon content and a lower content of harmful impurities. It is made by the open-hearth method and smelted in electric furnaces.

Let's give a description of each method of carbon steel production.

Oxygen-converter method of production.

The essence lies in the fact that air is passed through the liquid metal, the oxygen of which combines with impurities and takes them into the slag and into the exhaust gases, thereby purifying the metal.

Advantages of the method:

Simplicity;

Cheapness;

No fuel consumption;

High strength.

Flaws:

The use of liquid iron;

Cast iron composition limitations;

The amount of steel and iron scrap used is small;

The yield of suitable metal is approximately 90%;

Low quality steel, because when air is passed through, the molten metal is enriched with nitrogen, which makes the steel brittle, the temperature is insufficient to oxidize all impurities, and the steel contains a large amount of oxygen in the form of iron oxide.

Open-hearth method of production.

Depending on the composition of the charge, a distinction is made between the scrap-process and the scrap-ore smelting process.

In the scrap process, scrap and pig iron are loaded into the furnace. In the scrap-ore process, liquid iron is poured into the furnace, ore and scrap are added.

Smelting processes in open-hearth furnaces are divided into acidic and basic.

Characteristic features of the acid process: the furnace is lined with acid refractory bricks, a charge with a low content of sulfur and phosphorus is used, the removal of which in acid furnaces is difficult.

In the main smelting process, the furnace lining is made of magnesia or blast-furnace bricks; limestone is introduced into the charge to remove sulfur or phosphorus.

During the loading and melting of the charge, impurities are oxidized due to the oxygen contained in the furnace gases and ore, and after the formation of slag, it is contained in iron oxide dissolved in the slag. The oxidation of impurities proceeds according to the same reactions as in the converter process. Limestone converts sulfur and phosphorus into slag.

An important point in melting is the period of "boiling" - the release of the formed carbon monoxide in the form of bubbles. At the same time, the metal is mixed, its temperature (approximately 1800 C 0) and chemical composition are maintained, gases are removed, non-metallic inclusions float. Upon reaching the required carbon content in the boiling metal, which is determined by a quick analysis of the samples taken, proceed to last stage melting - finishing and deoxidation of metal.

Advantages:

Average power consumption.

Flaws:

Great environmental pollution;

Medium quality;

Average performance.

Smelting in electric furnaces.

At this method production uses higher temperatures (> 2000 C 0), which makes it possible to better remove harmful impurities, the waste of iron and easily oxidizing special additives is significantly reduced, because the process is carried out with the least air access. Also, with this method of production, a very dense metal is obtained, because. in a more liquid metal, gases are easily released to the outside.

Advantages of the method:

Simplicity and accuracy of temperature control during the melting process and at the time of its pouring, which is important for primary crystallization processes;

Obtaining high-quality steel, regardless of the quality of the initial charge materials, because the composition is adjusted during melting with special additives.

Comparative characteristics of steel production methods are given in table 4.1.

Index
	oxygen-converter	open-hearth	electric steel-smelting
Feedstock	liquid iron with t ◦ 1300-14520 С ◦ up to 25% scrap	55 - 75% liquid iron + 45 - 25% scrap + ore	up to 100% scrap
Furnace capacity, t
Melting cycle duration, h
Annual output, thousand tons of ingots

Index
	oxygen-converter	open-hearth	electric steel-smelting
Cost, relative percentages (for shops with the same annual capacity, equipped with 500-ton open-hearth furnaces and 100-ton oxygen-converter furnaces)
Yield, %
Specific capital costs, relative percentages
Steel quality	Steel of ordinary quality	Quality steel	High quality

Tab. 4.1 (continued).

The described methods for obtaining carbon steel are basic.

4.3. Raw material for pipe production and its heating

Depending on the method of production and purpose of pipes, the source material can be in the form of ingots, rolled or forged billets (to obtain seamless pipes), sheets and strips in rolls (to obtain welded pipes).

Due to the fact that steel water and gas pipes according to GOST 3262-75 are made welded, in this work I will consider the production of only welded pipes from sheets and strips in rolls.

Steel for hot-rolled sheets and coiled strip is divided into two groups according to mechanical properties. One of them is carbon steels with normal and high manganese content, and the second is calm steels with microadditives. These steels contain, %: carbon from 0.03 to 0.20, niobium 0.05, vanadium 0.02 and titanium 0.03. A common alloying element is molybdenum (~ 0.30%).

The required mechanical properties of steel sheets with micro-additives can be obtained by conventional rolling and normalization, controlled rolling followed by normalization. The minimum value of the yield strength as a result of these operations is 37 - 56 kgf/mm 2 . This is the result of the precipitation of niobium, vanadium and titanium carbide nitrides in the ferrite.

Rolled strip is used for the production of welded pipes with a longitudinal and spiral seam, and sheets - for the production of pipes with only a longitudinal weld. Moreover, the sheets must first be subjected to non-destructive testing to eliminate external and internal defects.

4.4. Plants for the production of welded pipes

Mills for the production of welded pipes are classified:

1) according to the type of materials used for welding (for welding steel pipes, non-ferrous metals and their alloys);

2) according to the method of welding (furnace, electric welding, longitudinal, spiral, soldering);

3) according to the size of pipes (small diameter 5 - 168 mm, medium 168 - 273 mm and large 273 - 2520 mm).

Furnace butt welding is carried out from strips of various widths. In addition, pipes of various diameters are obtained from strips of one or more widths by reducing them.

The pipe welding workshop has the following sections:

1) storage of materials (sheets in cards or sheets and strips in rolls);

2) cutting devices. Gouging or milling longitudinal edges of sheets and strips;

3) complex production equipment(rolling mills, presses for forming sheets and strips in pipe billet, welding mills or welding machines, rolling mills or pipe sizing presses, roller tables, conveyors and saws);

4) finishing section (straightening machines, trimming machines, machines for milling the ends of pipes, devices for hydraulic testing of pipes for tightness, devices and equipment for non-destructive testing, devices for stamping pipes);

5) warehouse of finished pipes;

6) auxiliary and repair tables;

7) sections of anti-corrosion support for pipes - galvanizing, asphalting, etc.

4.5. Technology of production of welded pipes

Currently, welded pipes are produced by continuous butt welding, electric resistance welding, induction welding, arc welding in a protective atmosphere or submerged arc welding. In addition, brazed pipes are produced.

In this paper, I will describe the production of tubes by furnace butt welding. this type of welding is one of the oldest methods for the production of steel water and gas pipes. This method, which has survived only in some countries, produces pipes with a diameter of 16 to 89 mm with walls 2.5 to 4 mm thick.

The starting material for the manufacture of these pipes is a hot-rolled strip 5 - 7 m long and a width depending on the diameter of the pipes produced.

One end of each strip is cut at an angle of 15 - 25° and then bent at a 45° angle for better grip by the pliers when it is pulled out of the oven.

The strips are laid on the hearth of the furnace with a protective atmosphere in such a way that the distance between the side edges is 20 mm. The strips are heated to a temperature of 1300 - 1350 ° C for 30 - 85 s. The heated strip is pulled out of the furnace with tongs, which are passed through the welding funnel (drawing wire) and connected to the drawing mill chain. During the drawing of the strip, to its edges (before the die) through the nozzles compressed air. As a result, the temperature of the strip edges rises by 40 - 60 ° C and the scale is blown off from them.

Pipes are formed and welded in a die. At the same time, depending on the size of the pipes, their diameter decreases by 4 - 10%. The pipes are welded at a speed of 100 - 200 m/min, and then they are transferred by a roller table to a two- or three-stand sizing mill, where their diameter is reduced by 2 - 3 mm, i.e. up to the size of the finished pipes.

Block diagram of the production of steel welded water and gas pipes.

5. NORMATIVE AND TECHNICAL DOCUMENTS FOR STEEL WATER AND GAS PIPES, RATED QUALITY INDICATORS IN ACCORDANCE WITH THE REQUIREMENTS OF NORMATIVE AND TECHNICAL DOCUMENTATION

At the request of the consumer, at the ends of pipes to be welded, with a wall thickness of 5 mm or more, chamfers must be removed at an angle of 35 - 40 ◦ to the end of the pipe. In this case, an end ring with a width of 1 - 3 mm should be left.

At the request of the consumer, on ordinary and reinforced pipes with a nominal bore of more than 10 mm, the thread is applied to both ends of the pipe.

At the request of the consumer, the pipes are equipped with couplings made in accordance with GOST 8944-75 (01.01.1977) “Connecting parts made of ductile iron with cylindrical threads for pipelines. Technical requirements”, GOST 8954-75 (01.01.1977) “Ductile iron fittings with parallel thread for pipelines. Couplings are straight and short. Main dimensions”, GOST 8965-75 (01/01/1977) “Connecting steel parts with cylindrical thread for pipelines p=1.6 MPa. Specifications” and GOST 8966-75 (01.01.1977) “Steel connecting parts with cylindrical thread for pipelines r-1.6 MPa. Couplings are straight. Basic dimensions”, based on one coupling for each pipe.

Cracks, captivity, swelling and sunsets are not allowed on the surface of the pipes.

At the ends of the pipes, delamination is not allowed.

Separate dents, ripples, risks, traces of stripping and other defects due to the production method are allowed, if they do not take the wall thickness beyond the minimum dimensions, as well as a scale layer that does not interfere with inspection.

On pipes made by furnace welding, it is allowed to reduce the outer diameter to 0.5 mm at the weld site if there is a gentle thickening of the inner diameter of not more than 1.0 mm in this place.

At the request of the consumer, on pipes with a nominal bore of 20 mm or more, on the inner surface of the pipe seam, the burr must be cut or flattened, while the height of the burr or its traces should not exceed 0.5 mm.

At the request of the consumer, on pipes with a nominal bore of more than 15 mm, made by the method of furnace welding and the method of hot reduction, a gentle thickening of a height of not more than 0.5 mm is allowed on the inner surface of the pipes in the weld zone.

Pipe ends must be cut square. A bevel value of no more than 2 ◦ is allowed. Burr residues should not exceed 0.5 mm. When removing burrs, the formation of blunting (rounding) of the ends is allowed. It is allowed to cut pipes in the mill line. By agreement between the manufacturer and the consumer, burrs up to 1 mm are allowed on pipes with a nominal bore of 6–25 mm, made by furnace welding.

Galvanized pipes must have a continuous zinc coating over the entire surface with a thickness of at least 30 microns. The absence of zinc coating on the ends and threads of pipes is allowed.

On the surface of galvanized pipes, blistering and foreign inclusions (hardzinc, oxides, sintered charge), peeling of the coating from the base metal are not allowed.

Separate flux spots and traces of pipes being caught by lifting devices, roughness and slight local zinc deposits are allowed.

It is allowed to correct individual non-galvanized sections by 0.5% of the outer surface of the pipe in accordance with GOST 9.307-89 (01/01/1990) " one system protection against corrosion and aging. Hot zinc coatings. General requirements".

Pipes must withstand hydraulic pressure:

2.4 MPa (25 kgf / cm 2) - ordinary and light pipes;

3.1 MPa (32 kgf / cm 2) - reinforced pipes.

At the request of the consumer, the pipes must withstand a hydraulic pressure of 4.9 MPa (50 kgf / cm 2).

Pipes with a nominal bore up to 40 mm inclusive must withstand a bend test around a mandrel with a radius equal to 2.5 of the outer diameter, and with a nominal bore of 50 mm - on a mandrel with a radius equal to 3.5 of the outer diameter.

At the request of the consumer, the pipes must withstand the expansion test:

for pipes with nominal bore from 15 to 50 mm - not less than 7%;

for pipes with a nominal bore of 65 mm or more - at least 4%.

At the request of the consumer, the pipes must withstand the flattening test up to a distance between flattened surfaces equal to 2/3 of the outer diameter of the pipes.

At the request of the consumer, the mechanical properties of pipes for parts of water and gas pipeline structures must comply with GOST 1050-88 (01.01.1991) “Rolled bars, calibrated, with a special surface finish from high-quality carbon structural steel. General technical conditions".

The pipe thread must be clean, without flaws and burrs, and comply with GOST 6357-81 (01.01.1983) “Basic standards of interchangeability. Cylindrical pipe thread, accuracy class B.

Pipes with cylindrical threads are used when assembling with seals.

In the place of the seam, blackness is allowed on the threads of the thread, if the decrease in the normal height of the profile does not exceed 15%, and at the request of the consumer does not exceed 10%.

Threads with broken (for cut) or incomplete (for knurled) threads are allowed on threads, provided that their total length does not exceed 10% of the required thread length, and at the request of the consumer does not exceed 5%.

It is allowed on the thread to reduce the useful length of the thread (without run-off) up to 15% compared to that indicated in Table 2.4, and at the request of the consumer - up to 10%.

Threading on galvanized pipes is carried out after galvanizing.

At the request of the consumer, welded seams of pipes are subjected to control by non-destructive methods.

6. QUALITY CONTROL OF GOODS. REQUIREMENTS OF REGULATORY AND TECHNICAL DOCUMENTS FOR THE RULES OF ACCEPTANCE, STORAGE, TESTING AND OPERATION OF STEEL WATER AND GAS PIPES

Quality control of steel water and gas pipes is carried out by testing them for distribution according to GOST 8694-75, for tension according to GOST 10006-80, for flattening according to GOST 8695-75, for bending according to GOST 3728-78, hydraulic pressure according to GOST 3845-75, etc. .methods that determine the quality of a given product.

In this work, I use GOST 10006-80 (07/01/1980) “Metal pipes. Tensile test method. This standard establishes a method for static tensile testing of metal seamless, welded, bimetallic pipes to determine at a temperature of 20 -10 +15 C the following characteristics: yield strength (physical), yield strength (conditional), tensile strength, elongation after rupture, relative contraction after the break.

For tensile testing of pipes, longitudinal (in the form of strips without heads and heads) and transverse samples (in the form of a pipe segment of a full section without limiting the outer diameter) are used. As testing machines, tensile and universal testing machines of all systems are used that meet the requirements of this standard and GOST 28840-90.

Quantitative and qualitative indicators of pipe testing by the tensile method are given in GOST 10006-80 (07/01/1980) “Metal pipes. Tensile test method”, which is attached to this work.

Pipes are accepted in batches. The batch must consist of pipes of the same size, the same steel grade and be accompanied by one quality document in accordance with GOST 10692 with an addition for pipes intended for the manufacture of parts for water and gas pipeline structures, from steel in accordance with GOST 1050; chemical composition and mechanical properties of steel - in accordance with the document on the quality of the blank manufacturer.

Party weight - no more than 60 tons.

The surface, dimensions and curvature are checked for each pipe of the batch.

It is allowed to apply statistical control methods in accordance with GOST 18242 with a standard level. Control plans are established by agreement between the manufacturer and the consumer.

The control of the outer diameter of the pipes is carried out at a distance of at least 15 mm from the end of the pipe.

To control the parameters of the thread, to test for expansion, flattening, bending, the height of the internal burr, burr residues, right angle and chamfer angle (for pipes with beveled edges), mechanical properties, no more than 1%, but not less than two pipes from the lot are selected, and for pipes manufactured by continuous furnace welding, two pipes per lot.

All pipes are subjected to weight control.

Each pipe is subjected to a hydraulic pressure test. With 100% quality control of the weld by non-destructive methods, hydraulic pressure testing may not be carried out. At the same time, the ability of the pipes to withstand the test hydraulic pressure is guaranteed.

To check the thickness of the zinc coating on the outer surface and in hard-to-reach places on the inner surface, two pipes are taken from the batch.

Upon receipt of unsatisfactory test results for at least one of the indicators, it is repeated tests on a double sample.

The retest results apply to the entire lot.

Marking, packaging, transportation and storage are carried out in accordance with GOST 10692 with an addition.

Pipe threads must be protected from mechanical damage and corrosion with grease in accordance with regulatory and technical documentation.

CONCLUSION

The widespread use of tubular products in all industries - for the production and processing of oil and gas, in energy and mechanical engineering, rocket and space technology and construction due to their diverse assortment in terms of diameter and wall thickness, cross-sectional profile, material, manufacturability and cost-effectiveness of production and consumption . This explains the outpacing growth in the production of steel pipes in comparison with the growth in the production of steel and finished rolled products.

The modern pipe market provides a large selection of water and gas pipes made of new materials (plastic, mineral raw materials), but, oddly enough, metal pipes are often preferred.

The modern science of pipe production is developing and will continue to develop at a high pace. The strengthening of its influence on the technical progress of the pipe industry is associated with an increase in the efficiency scientific research and improving the quality of training of engineering personnel in the field of pipe production.

LIST OF USED LITERATURE

1. Steel and cast iron pipes. Handbook./V. I. Strizhak, V. V. Shchepansky, V. P. Sokurenko and others - Moscow: Metallurgy, 1982. - 360 p.

2. Steel pipes. Production technology and application. / Ed. N. T. Bogdanova. Moscow: Metallurgy. 1979.

3. Rozov N.V. Production of pipes. Handbook for workers. - Moscow: Metallurgy, 1974. - 600 p.

4. Rymov V. A. et al. Technology for the production of welded pipes. Moscow: Metallurgy. 1983.

5. Gulyaev Yu. G. et al. Steel pipes. Production, application, assortment: a Handbook. - Dnepropetrovsk, RIA "Dnepr-VAL", 2002. - 350 p.

6. Improving the production of steel pipes. Zimovets V. G., Kuznetsov V. Yu. / Ed. prof. doc. tech. Sciences A.P. Kolikova - Moscow: MISIS, 1996. 480 p.

The 21st century is the age of pipelines. A lot of pipes are required for oil and gas transport arteries, and seamless products alone are not enough. Seamless pipes, with all their many advantages, have one more very significant disadvantage from the consumer's point of view - they are expensive to manufacture. Meanwhile, the main advantage of seamless pipes - the ability to withstand huge pressures - is not always in demand. In many pipeline networks, the pressure in the pipes never reaches the hundreds of atmospheres that make the use of seamless pipes necessary. Again, metal processing technologies do not stand still and the strength of welds in our time allows welded pipes to hold pressure many times greater than thirty to forty years ago.

Therefore, there is nothing surprising in the fact that welded pipes retain their positions and in some places even win in competition with seamless ones. In any case, now up to half of large diameter pipes are welded. This is already enough to further understand what welded pipes are, what technologies are used in their production, and in what sectors of the economy they can be used most successfully.

Straight or spiral?

Oddly enough, but welded pipes are a rather “young” type of metal products. The first samples of welded (more precisely, even forged) pipes appeared less than 200 years ago - in 1824. And only at the beginning of the 20th century, the so-called "pipe" began to be used for the manufacture of pipes. “furnace” welding, in which the fastening of the hot edges of the pipe occurs due to their compression with rolls.

And only with the advent of electric welding, seam pipes are divided into straight-seam and spiral-seam.

The name "straight-seam" speaks for itself: this method of manufacturing pipes is due to the fact that the steel strip - the strip - is heated to give the metal plasticity and passed through two rows of rolls that roll the metal "into a tube" - so all that remains is to connect its edges electric welding.

This is a fairly simple and cheap technology, but some problems arise when using it, namely:

For the manufacture of pipes of different diameters, blanks-strips of different widths will be needed.

The transition to the production of pipes of a different diameter will require re-equipment with new parts (primarily -
rolls) of the entire production line.

When the workpiece cools, stresses will arise in the weld, which will significantly reduce its strength.

If such a pipe still cannot withstand the pressure supplied through it, then its rupture will occur precisely along the seam and along the entire length of the pipe segment, which will create additional problems in the event of an accident.

Another option for the production of welded pipes is the connection of steel strips using a spiral seam. With this technological option, the seam itself is much longer than with a straight-seam connection, but it appears whole line advantages:

- in the manufacture of a spiral-seam pipe, there is no need to use blanks-strips clearly certain sizes; the pipe can be welded from a metal strip of any width

Changes in the diameter of the produced pipes can be made with a simple changeover of the production line; it will be enough just to change the angle of feed of the tape.

When welding a pipe from a metal strip, it is not necessary to heat up the entire metal strip strongly; this reduces the possibility of changing the properties of the metal during heating-cooling and reduces the possibility of internal stresses in it.

With spiral welding, the resulting seam itself becomes an element that gives additional strength to the structure.

If such a seam still does not withstand and diverges, then it diverges not “along”, but “obliquely”, which reduces the size of the pipe section that will have to be replaced.

Pros and cons of welded or electric-welded pipes

Of course, all the technological problems and energy costs in the production of straight and spiral pipes cannot be compared with the efforts that the manufacturer must spend on production. Hence the main advantage of this type of rolled steel is its relative cheapness.

Another undoubted advantage of welded pipes is their large diameter, which can exceed the wall thickness by 100 or more times. This makes the pipes lighter and therefore easier to transport. In addition, it is the large diameter of welded pipes that makes them indispensable in the construction of main oil and gas pipelines.

The manufacturing technology of longitudinally welded pipes makes it possible to form not only round ones, but also (primarily square and rectangular ones).

These advantages in a market economy outweigh all the disadvantages, but these disadvantages still exist. What do they consist of?

Firstly- withstand pressure by an order of magnitude less than seamless ones. This can be judged even by the norms of GOSTs. If seamless pipes with a minimum wall thickness are required by GOST to withstand a pressure of 20 megapascals (that is, about 200 atmospheres), then GOST-10705 has a maximum allowable pressure of 16 megapascals (160 atmospheres) for welded pipes. That is, seam pipes are 25% less resistant to such loads.

Secondly- Welded pipes, unlike seamless pipes, cannot be bent. If it is necessary to change the direction of a gas or water pipeline assembled from welded pipes, you will definitely have to use fittings.

Thirdly- the very technology for the production of welded pipes requires the use of steel grades that lend themselves well to welding - that is, they must be made from low-alloy carbon steels that are relatively less resistant to corrosion. Such as steel grades 17G1s and 09G2S.

This circumstance forces welded pipe manufacturers to use various ways corrosion prevention, which include:

Galvanizing of internal and external surfaces (for steels st3 and st20)

Covering external surfaces with waterproofing

Coating of external surfaces with thermal and hydro-insulation

Applications and GOSTs

Since the main advantage (apart from low cost) of welded pipes is their large diameter with thin walls, they are used in domestic water pipes, various metal structures - but most of all they are used primarily in large construction projects.

The ability of welded pipes to withstand high pressure liquids makes it possible to use them for laying both main and local communications, distribution branches, local technical water conduits and in the housing and communal services sector.

Accordingly, the standards that define their parameters are configured accordingly:

GOST, name
GOST 10705-80	GOST 10706-76	GOST 20295-80
Pipes steel electrowelded	Longitudinal electric-welded steel pipes	Electric-welded steel pipes for main oil and gas pipelines
Steel grades
Carbon steel St1-3sp/ps Quality 08, 10, 20	Carbon St3sp/ps	Quality 10, 20 Low-alloyed 09G2, 09G2S, 17GS, 17G1S The choice of steel grade is due to the strength class K34-K60
Dimensions (outer diameter)
from 10 mm. up to 530 mm.	from 478 mm. up to 1420 mm.	from 159 mm. up to 820 mm.
Fields of application of electric-welded pipes
Construction of general-purpose pipelines for cold and hot water, domestic gas	Construction of water supply pipelines and heating mains	Construction of main pipelines - oil pipelines and high pressure gas pipelines

Accordingly, the rules for the implementation of welded pipes will also depend not only on the wishes of the client, but also on the parameters of the products themselves. The outer diameter of the pipes varies up to 1620 mm, and the wall thickness in accordance with the diameter - up to 20 mm.

Pipes are classified according to external geometric indicators as follows:

1-pipes with a diameter of less than 70 mm with a wall thickness of at least 3 mm;

2-pipes with a diameter of 70 to 219 mm with a wall thickness of at least 4 mm;

3-pipes with a diameter of more than 219 mm with a wall thickness of at least 5 mm.

Now almost all welded pipes are manufactured in standard lengths:

6 m to 76 diameter

11.7 and 12 meters for all diameters over 76.

The most popular are steel electric-welded pipes for the production of water pipes, as well as electric-welded pipe GOST 10704 91, used for the construction of metal structures.

Welded pipes are quite versatile and affordable, but when choosing them, you need to be especially careful in calculating the hydraulic load.

Steel pipes have high strength, which is due to their wide application in sewer works, when laying heating networks, in the construction of industrial or civil facilities, shipbuilding, mechanical engineering.

Depending on the type, steel pipes differ in the characteristics of the material and the method of their manufacture.

One of the advantages of steel pipes is their relative lightness combined with reliability.

Classification of steel pipes

Considering the way in which steel pipes are manufactured, they are divided into:

Profile - in their manufacture, the material is mainly carbon or structural steel, pipes are made by electric welding. They can have a variety of sections. It is convenient to use these pipes in the construction of structures of industrial or economic facilities, due to which they have become very widespread. For example, the Metallobaza company has proven itself well, from which you can buy a profile on the ros-met.com website. All products of this type must meet the conditions specified in the regulatory documentation (regulated by GOST 8638-57, 8644-68, 8639-82, 8642-68 and 8646-68).

Galvanized - pipes that are impregnated on both sides with zinc as a protective material.

Seamless - the production includes a special heat treatment of hot-formed pipes, due to which the product has neither longitudinal nor spiral welds.

Electrowelded - low gelled and carbon steels are used in the manufacture, electric welding and forming are used, in accordance with established state quality standards (GOST 10704-91, GOST 20295-85, GOST 10705-80, GOST 380-94, GOST 1050-87, GOST 9045- 87, GOST 10706-80, GOST 8696-74, GOST 3262-75).

Seamless pipes are:

1. Hot-formed (according to GOST 8732-75 and GOST 8731-74) - steel pipes that are deformed at a temperature that is higher than the recrystallization temperature.

2. Cold-formed (GOST 8734-75 and GOST 8733-74) - steel pipes obtained by cold deformation.

Steel pipes can have different lengths and cross-sectional diameters.

Depending on the section, pipes are produced in various measured and random lengths:

With a section diameter of up to 70 mm, pipes with a length of 5 to 9 m are produced;

From 70 to 219 mm in diameter, length - 6-9 m;

Pipes with a diameter of 219-426 mm are most often produced in lengths of 10-12 meters.

Such pipes can be processed or not at the ends, depending on this, their final price is added up.

According to the type of cross section, steel pipes are divided into:

With a circular cross section (GOST 10704-91);

profile pipes.

Profile pipes can have a square (according to GOST 8639-82), oval (according to GOST 8642-68) or rectangular (according to GOST 8645-68) or other section.

The main advantages of steel pipes

Steel pipes have their advantages in comparison with analogues from other materials, namely:

Their mass is relatively small;

They are characterized by high strength, which leads to excellent performance;

They have fairly good flexibility, which is very convenient when the pipe needs, for example, to set the desired angle;

Installation of such pipes is very simple;

Steel pipes have a high rate of tightness.

Applications of steel pipes

Steel pipes are one of the most popular metal products. They have found their application in industry, construction, agriculture and in everyday life.

Electrowelded steel pipes are most often used in the laying of main heating networks, various metal structures and pipelines.

Water pipes are different a high degree resistance to temperature regime, pressure, adverse environmental conditions. They are used for laying water and gas pipelines. Such pipes have a very long service life.

The use of steel pipes depending on the class

The class of pipes determines the areas of their application:

1. The first class of pipes is used in the construction of local pipelines and cable systems. There are no special requirements for them.

Steel products are used in many areas of production. It is steel that is the material for the production of steel pipes. Both the manufacture of steel itself and the production of steel pipes from it is a rather complicated and lengthy process.

Stainless steel is a versatile, widely used material from which many products are made. Steel pipes are perhaps the most popular products that are made from stainless steel.

Allocate steel seamless, electrowelded, profile, boiler and other pipes. Additional processing is carried out on those products that are subject to increased requirements. Anti-corrosion treatment improves physical properties metal and quality of steel pipes. Among the diverse range of products you can find steel pipes coated with plastic, cement, anti-corrosion paints, varnishes and other compounds, special materials.

Steel Pipe Manufacturing Basics

At the core of production- the process of rolling and compression, with the help of which it is possible to produce pipes of various sections and shapes.

Welded steel pipes. The steel sheet is rolled up, the seam runs along the pipe, or as a steel strip in a spiral.

Seamless steel pipes. They are obtained by rolling on special equipment. In addition, there is a method in which these pipes are made by casting, by pouring metal into a special mold with a central rod.

Each belongs to a specific class. Allocate 6 grades of steel pipes. They are characterized by the following features: material of manufacture, purpose, uniformity of material in cross section, cross section shape and pipe production method.

first class pipes, otherwise called standard or gas, they are used for the installation of pipelines, transportation of non-aggressive gases and liquids, bulk materials, as well as scaffolding, fences and supports, for laying cables and various kinds of irrigation systems.

Second class pipes used in main pipelines high and low pressure for the supply of gas, oil and water, petrochemicals and fuels.

Steel pipes of the third class are used in systems operating under pressure and at high temperatures - in the chemical and food industries, nuclear engineering, in oil cracking pipelines, in furnaces and so on.

Used for exploration and exploitation of oil fields pipes of the fourth class. They are used as drilling, casing and auxiliary pipes.

Structural pipes or pipes of the fifth class are used in the manufacture of transport equipment, in various steel structures, such as overhead cranes, drilling rigs, masts and supports, as furniture elements.

Finally, sixth grade pipes used in mechanical engineering for the manufacture of cylinders and pistons of pumps, bearing rings, shafts and other machine parts, as well as tanks operating under pressure.

They have a number of advantages. Strength, lightness, ductility, easy installation - these are the properties that distinguish steel pipes. Among the minuses, it is worth highlighting the instability to corrosion. This disadvantage will not matter if you use corrosion resistant steel pipes or stainless steel pipes.