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Distributor / authorized representative that deals with supply & delivery of tube and pipe plants and equipment to industrial enterprises of Russia

Engineering company ‘Intech GmbH’ LLC (ООО «Интех ГмбХ»), Russia, has been successfully working with a number of Russian industrial enterprises at the local market for more than 20 years. Since the company’s founding, it has acquired immense engineering experience, market reputation, and has realized more than a hundred large-scale projects at the industrial plants in Russia. Our company is continuously in search of new business partners, who consider Russian market investment-attractive and want to boost their sales in the region, as well as expand their field of activities and enter a new international level. 

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We are interested in cooperation with the manufacturers of pipe plants and equipment, who are looking for an official and reliable distributor that deals with supply & delivery of their equipment to the industrial plants in Russia.

The company’s top management and sales team are well acquainted with the Russian market, its mentality and laws; they also understand industrial specifics of the financial and economic activities of the Russian customers. All our sales managers have a large customer database, extensive experience of successful sales and well-established connections with the potential buyers of your pipe mills. This allows our managers to promptly set out the most promising directions for promotion and to ensure a rapid entry of the products into the promising Russian market. Our employees, who are fluent in English and German, are focused on working at the international market with the supplies of foreign equipment.

Our team of experienced engineers, who can handle the most serious technical problems, constantly keeps in touch with the Russian customers, holds meetings and delivers presentations regarding the latest achievements of our manufacturing partners. They point out the engineering challenges and actively communicate with all the departments at Russian plants. That is why the specifics of doing a business in the Russian Federation are well-known to us, and we also know the equipment of the local industrial plants and their up-to-date modernization needs.

Once we become your authorized representative in Russia, our marketing staff will carry out a market research in order to check the demand for pipe mills, will submit a market overview for tube and pipe mills that you offer and evaluate the needs for this type of equipment at local plants. Our specialists will also estimate the potential and capacity of this market at local industrial plants. Our IT-team will start developing a website for your products in Russian. Our experts will assess the conformity between your tube and pipe plants and equipment and customer needs as well as analyze the common reaction to the new goods in general. We will look into the categories of potential customers, and pick out the largest and the most promising plants.

Upon becoming your authorized agent on the territory of Russia, ‘Intech GmbH’ LLC (ООО «Интех ГмбХ»), will obtain certificates, if required, for a batch of the goods, for various types of tube and pipe plants and equipment in compliance with Russian standards. We can also arrange the inspection in order to obtain TR TS 010 and TR TS 012 Certificates. These certificates provides permission to operate your equipment at all industrial plants of the EAEU countries (Russia, Kazakhstan, Belarus, Armenia, Kyrgyzstan), including the hazardous industrial facilities. Our company is eager to assist in issuing Technical Passports for tube and pipe plants and equipment as per Russian and other EAEU countries’ requirements.

Our engineering company ‘Intech GmbH’ LLC (ООО «Интех ГмбХ»), collaborates with several Russian design institutes in various industrial segments, which allows us to conduct preliminary design as well as subsequent design works according to the standards, construction rules and regulations that are applicable in Russia and other CIS countries. It also enables us to include your tube and pipe plants and equipment into the future projects.

The Company has its own logistics department that can provide packing service, handling as well as the most efficient and cost effective mode of transportation of the goods (incl. over dimensional and overweight goods). The goods can be delivered on DAP or DDP-customer’s warehouse basis in full compliance with all the relevant regulations and requirements that are applicable on the Russian market.

Our company has its own certified specialists who will carry out installation supervision and commissioning of the delivered equipment, as well as further guarantee and post-guarantee maintenance of tube and pipe plants and equipment. They will also provide necessary training and guidance for the customer’s personnel.

Pipe making: Functions and steel pipes range

Metal pipes are made of carbon steels grades, low- and high-allow steels, non-ferrous metals, various alloys, cast irons of various types; they can be bimetallic or be made of metal combinations.

The main range of production for tubes is based on manufacturing pipes using composite metals (bimetallic ones):

  • steel plus copper;
  • stainless steel plus non-ferrous metal;
  • metal compounds being alloys.

Pipes are produced using various processing methods such as metal treatment under pressure or welding.

The pipe products being manufactured are classified as follows:

seamless, welded, brazed and cast pipes. The latter ones are of limited use.

The seamless pipes can be rolled by hot rolling (hot-rolled pipes), cold rolling (cold-rolled pipes), drawing (cold-drawn) or extrusion.

Welded pipes are divided into electrically welded pipes produced by either arch or induction welding and furnace welded pipes. Cold- and hot-rolled pipes are made from either seamless or seamed billets.

According to the material, the pipes are divided into non-metal pipes (made of plastic, on the cement basis, etc.) and metal pipes (either ferrous or non-ferrous metals), bimetallic and coated ones.

Monometallic pipes are used as starting products for obtaining compound (bimetallic) pipes. They present the basic and surface layers.

The pipes are also distinguished by the possible jointing methods

The joints can be welded, flanged or threaded (union, streamlined or nipple type).

As regards the profile, the pipes are characterized as:

  • round;
  • oval;
  • rectangular;
  • square;
  • ribbed;
  • stepped;
  • tapered;
  • with variable wall thickness, etc.

The pipes are also classified according to the outer diameter (D) / wall thickness (S) ratio:

  • extremely thick-walled pipes (the above ratio is less than 5.5);
  • thick-walled pipes (the ratio is 5.5...9);
  • normal pipes with medium wall (the ratio is 9...20);
  • thin-walled pipes (the ratio is 20...50);
  • extremely thin-walled pipes (the ratio is more than 50);

As regards the outer diameter, the pipe products are divided into:

  • capillary pipes, with D = 0.3…4.8 mm
  • fine pipes, with D = 5…102 mm
  • medium-sized pipes, with D = 102…426 mm
  • large-sized pipes, with D of more than 426 mm.

The analysis of demands of various branches of economy has shown that 25-30% of the total pipe consumption fall to the share of the pipes with the maximum diameter of 63.5 mm and this their consumption tends towards growing.

Tubes being used in the industry are classified as follows:

  1. seamless pipes (made of non-alloy and alloy steel) for the oil and gas industry,
  2. drill pipes for drilling the exploration wells (Ø 33.5-63.5 mm, wall thickness 5-6 mm);
    drill pipes with the diameter of 60-168 mm and wall thickness of 7-11 mm are used for drilling the producing wells; The drill pipes are manufactured of steels 36Г2С, 40Х, 30ХГС and steel Д;
  3. case pipes protect the well walls against destruction, penetration of moisture into the wells and separate formations (gas- and oil-bearing). Their diameter reaches 114-508 mm and the wall thickness is 6-14 mm according to the standards. For example, steel Д shall meet these standards in respect of mechanical properties: ultimate strength σu ≤ 650 MPa, yield limit σy ≤ 380 MPa and relative elongation δ10≥16 %. The maximum sulfur and phosphorus content in steel is 0.045% per element;
  4. pumping and compression pipes (Ø48.3-114.3 mm, wall thickness 4-7 mm) are used in the oil extraction for pumping compressed air into the well and pumping out the oil). They have smooth and upset couplings and ends with very leak-tight smooth union joints and streamline joints.
  5. line pipes, in which oil, gas, gasoline, steam, air, oils, acids, sand, chippings, coal or cement flows. They are classified as follows:
    - pipes for gas and water (gas only) conveyance with the diameter of 10.2-165 mm and wall thickness of 2,25-5,5 mm are used under the pressure of up to 2.5 MPa and connected by couplings; they are made by furnace welding;
    - oil-line pumps with the diameter of 114-426 mm and wall thickness of 4,5-20 mm;
    - main pipelines with the diameter of 426-1420 mm (with straight-line or spiral weld) and wall thickness of 5-14 mm are intended for transportation of oil and gas from the place of extraction to the point of their consumption. They are primarily made by welding.
  6. Construction pipes. These round, square or rectangular pipes are primarily made by welding and used as columns of buildings, ceilings and scaffolds as well as for installation of cable networks and handrails.
  7. Pipes for machine building made to be seamless (material: low-alloy, structural, alloy- or high-alloy steels). These are the following pipe groups:
    • Boiler pipes with the diameter of 45-152 mm and wall thickness 1.5-25 mm; they are used for boilers of different design: boilers, superheat boilers, fire boilers, flue-gas boilers, etc.
      The boiler function consists in the heat exchange through the pipe walls between the combustion products and water in the steam generator.
      The boiler pipes are exposed to high temperatures and pressures. The material of the boiler pipes and assemblies are subject to corrosion when the pipe screening surfaces and welded joints contact the water steam.
      The corrosion is mainly caused by oxidation of the pipe surface leading to decreased thermal conductivity and therefore to local increase of the pipe wall temperature. The oxidation degree can depend even on the duration of storage of the pipes in warehouses.
    • Cracking tubes with the diameter of 19-219 mm and wall thickness of 1.5-25 mm are used for pumping hot oil products under the pressure of up to 10 MPa. The most essential peculiarity of operation of the cracking pipes consists in the fact that oil containing a variety of compounds from volatile to heavy substances is usually contaminated with sand, salts and water. The oil extracted is collected in tanks and then it is distilled. This first stage of the oil refining, which is the most important one, is performed at 40-350°С and low pressure. Gasoline, kerosene and oils are extracted at this stage. The second stage is performed simultaneously with the cracking at 400-700°С and 2-200 atm. As a result, gas-oil and burning oil are obtained.
    • Structural pipes are used in manufacture of various component parts of machines. They include bearing tubes, tubes for automobile and tractor industry, aircraft, nuclear and medical industries, etc.; they are made welded or seamless.
      Anti-friction bearings are manufactured of chromium steels. The requirements for ball-bearing steels specify the weakness, impurities, structure in the annealed state, case depth, surface quality and dimensional precision.
    • Vessels (gas cylinders and other) are manufactured of pipes made seamless and to be used under the pressures of 0.1-40 MPa. The pipe diameter and wall thickness shall correspond to the cylinder dimensions; the most common dimensions are: diameter 70-465 mm and wall thickness 2.3-34 mm. The pressure pipes are operated under the pressure of 200.0-400.0 MPa.
      In our country, pipes with the diameter of 0.3-2,520 mm and wall thickness of 0.01 - 150 mm are produced.

Requirements and standards

The standards include technical requirements for the pipes, their qualitative indicators, regulations for acceptance and testing methods.

The schedule standards determine geometrical dimensions and profiles of the pipes, specify maximum deviations of the pipe dimensions (diameter, wall thickness and length), curvature and weight.

The technical requirements of the standards determine main requirements for the pipes: steel grade, mechanical properties, surface condition, testing, regulations for acceptance, marking, packaging, transportation and storage of the pipes.

The standards for testing methods determine generally acceptable testing methods for: hardness, impact strength, macro- and microstructure, corrosion resistance, etc.

The standards covering regulations for marking, packaging, transportation and storage specify requirements for all (cast-iron and steel) pipes.

Most of pipes are made of low-carbon steels. The alloy material consists of pearlite steels. Stainless pipes are produced of austenitic steels.

In addition, ferritic, austeno-ferritic, martensite-ferritis, martensitic and martensite-austenitic as well as nickel, titanium, zirconium, niobium, molybdenum and tantalum alloys are used in the pipe manufacture.

The hot rolling does not allow making the pipes with high surface roughness (class 7-11) and precise dimensions. To obtain such qualitative characteristics and to make small-sized pipes, either cold or warm working is used. It is achieved in two ways:

  • drawing;
  • rolling.

The pipes with the diameter of 4.0-200 mm and wall thickness of 0.1-12 mm are made by cold rolling and cold drawing.

These methods are also used to make shaped pipes. They can have oval, square, octahedral, star-like, ribbed or other sections.

Dimensional limits for cold-rolled and cold-drawn pipes.

The starting products for welded pipes are steel products with low carbon content and low alloying such as:

  • hot-rolled strips;
  • rolled bands from cold-rolling mills;
  • wide semi-finished rolled stock from cold-rolling mills;
  • sheet material of specified length;
  • rolled strips.

The billets for these pipes are obtained by modern continuous-rolling methods.

These pipes have thinner walls and less wall thickness variation than seamless pipes.

Electrically welded stainless-steel pipes are widely used today.

Strength indexes for main-schedule pipes

The strength indexes are considered the main characteristic for the main-schedule pipes. It is determined by testing the mechanical properties of the finished pipes. The following mechanical indexes are checked:

  • ultimate strengths;
  • yield;
  • relative elongation;
  • contraction in area;
  • impact strength;
  • hardness.

For pipes installed for operation in the higher-temperature environments, the conditional yield limit (at 300-350°С) is sometimes considered.

The pipes to be used under pressure are subject to hydraulic pressure tests.

The pipes are hydraulically tested to detect areas with unexamined seams. The threaded pipes for the oil industry are also checked by hydraulic pressure testing for leak-proofness of the threaded joint.

The resistance of the pipes to various loads and deformation is checked during engineering tests.

For bending test, the pipe is smoothly bent to the angle α (usually α = 90°) and inspected to determine whether the metal integrity is broken or not.

The pipe surface quality is determined by its strength. The requirements for the pipe surface are strict; to meet them, the seamless pipes are subject to machining, complete boring, turning, grinding or electric polishing.

The pipe is inspected visually from outside and inside. The special-purpose pipes are to be checked from inside by means of a periscope. The nondestructive testing methods, for example, ultrasonic or magnetic-particle inspection, are widely used.

The ultrasonic inspection helps in detection of defects both on the pipe and in its wall.

The screening test is performed according to the level of the echo signal from the specified artificial defect made on the test sample.

Structure of the seamless pipe making process

Generally, there are three stages in seamless pipe making: obtaining the ingot (continuously cast billet), manufacturing the billet (intermediate product) and making the pipe.

To implement this stages, various combinations of equipment can be used. The presence of liquid metal production, teeming or casting into CCM is typical for all the variants. It is the first process stage.

The second process stage, i.e. billets (intermediate product) production, is implemented in the rolling or forge shops, on the longitudinal (screw-) rolling mills and forging presses (hammers), respectively. At this stage, strict requirements for the pipe billet quality as regards its internal structure and level of contamination with sulfur, phosphorus and dissolved gases are met. The ingots for pipes and billet of ferrous metal may be transferred to pipe rolling plants.

The third process stage is yet more complex. It is implemented in pipe rolling plants. It consists of 3 stages: piercing, rolling-off and hot finishing. Application of various piercing methods based on the screw rolling (roll-type mills) and extrusion itself or in combination with the longitudinal rolling allows using both billets and ingots as starting products and making high-quality blooms.

For less ductile and difficult-to-form steels, the extrusion and press-rolling are usually used at this stage.

The piercing is performed on roll mills with drum-type work stands; vertical hydraulic direct-action presses; press-rolling plants with hydraulic or rack-and-pinion drive and two-roll longitudinal-rolling stand.

For the rolling-off, the longitudinal and screw-rolling, extrusion of metal through a slit and reciprocating plug rolling (on a plug and mandrel) are also used. The said methods are implemented on automatic or continuous mills, push benches, screw-rolling lines, pipe section presses and pilger mills.

At this stage, the required thickness of the pipe (its wall) is obtained. In case of automatic mills and push benches, the equipment includes the screw-rolling reeling mills to obtain a regular round profile and eliminate wall thickening (at the pass exit area). One should note a variety of reeler designs, use of the work stands with the open-type (automatic mills, 3-hi reeler, etc.) and closed-type (continuous-rolling mill, push bench, pilger mill) beds, etc.

The stage of hot calibration is very critical. It is performed by the longitudinal rolling and screw-rolling without mandrel. At this stage, the regular round profile and diameter of the pipe within the specified tolerances are formed. For calibrating and reducing, mainly continuous groups of 2-hi and 3-hi stand (of closed type) are used.

The stretch and reducing operation mode of the group of stands on the continuous unit is widely used. This set of equipment is characterized by various main drives: individual, group, variable group drive or hydraulic drive that allows the precise speed control as the rolls rotate.

With all the diversity of sizes and steel grades required for manufacturing the seamless pipes and hollow billets (more than 30 thousand profile-size combinations and more than 200 steel grades), homogeneous operations, which determine the equipment components and shop layout, can be marked out.

Production of the seamless pipes and hollow billets includes a set of operations involving billet deformation. They are performed until the finished pipe with the specified characteristics is obtained. The process progress, sequence of operations and types of processing depend on the configuration, dimensions and quality of the incoming billet and finished product requirements determined by the pipe service conditions.

The incoming metal is stored in or transported to the warehouse. In the warehouse, the metal is weighed, duly stowed and inspected (totally or randomly) prior to sending to production. If necessary, it is refined to eliminate defects and inspected again.

As a rule, the billets are inspected and refined to eliminate defects at the manufacturing plant. However, for special critical duty pipes, this operation is performed again in the pipe rolling plant. In some cases, elimination of defects is followed by additional thermal and chemical treatments. For example, the billets for the pipes to be used in high-pressure boilers undergo all additional treatments and then they are subject to the quality control again. For rolling with heating at the previous stage of manufacture (hot charge, transit rolling), the billet is heated in the heating devices or on rolling units. In this case, the billets are transferred to the rolling mill without entering into the warehouse and preparation area.

The prepared billet is transported to the production area. Here, a set of operations is performed to obtain a rough product: heating (if necessary); various deformation operations performed with heating the material to be deformed; cooling and straightening.

The products are inspected, marked, refined and sent to the manufacture of finished products. Here, the rough product is processed to become a finished product with the specified properties. After the re-inspection, the finished products are marked and refined, if necessary; they are sent again for finishing and control. Then, the pipes are coated with anticorrosive compounds and sent to the finished-products storage area.

The modern equipment allows implementing a certain technology at the production area. This complex of equipment includes such areas as warehouses, area for inspection and preparation of starting material, hot (or cold) deformation line, roughing department, partial monitoring, refinement and finishing of the finished products.

All of them are interconnected by transport operations.

The interrupted pipe-making mode ensures:

  • manufacture of products with specified properties;
  • required production volumes while minimizing the rejection of the processed material;
  • minimum costs for a process stage;
  • high labor productivity;
  • satisfactory working environment for servicing personnel;
  • absence of hazardous emissions into the shop and environment (water or air basins).

The pipe-making processes are determined by the number and type of operations, processing mode and process equipment components, number of equipment units, complexity of relationship between them, requirements for the transportation and control systems as well as requirements for power-supply and auxiliary services.

When converting the mother pipe into the finished one, various pipe treatment methods are used.

The heat treatment is widely used; it contributes to:

  • improvement of ductile properties;
  • improvement of mechanical characteristics of the pipe material;
  • relief of stresses having appeared due to billet cold deformation.

The heat treatment is performed in the air, in the gaseous mix of the combustion products in the furnace or in protective media (nitrogen, hydrogen, gas mixes). Depending on the metal properties and treatment method, the heat treatment temperature can be 500-1150°C. For the heat treatment of the pipes, the throughfeed-type furnaces are mainly used such as roller-hearth, sectional, muffle or conveyor-type furnaces.

The electrochemical treatment of the pipes contributes to:

  • improvement of the corrosion resistance;
  • improvement of the pipe surface condition (electric polishing);
  • washing of the pipes with small diameter and large length from inside;
  • degreasing with creation of oxide film;
  • ensuring high quality due to cleaning the pipe surface from lubricants (electrolytic degreasing).

The chemical treatment in the pipe making contributes to:

  • cleaning of pipes from scale and rust film;
  • revealing of defects and removal defective layer (etching);
  • removal of sludge (clarification);
  • removal of a thin layer of surface oxides prior to coating or arrangement of bimetallic pipe (activation);
  • preparation of pipes for intermediate operations (degreasing, washing, application of process lubricants and layers);
  • corrosion protection (preservation).

Etching, including clarification and activation processes, is one of the widespread methods of chemical treatment. The material and geometrical dimensions of the pipes determine the etching methods: acidic, alkaline and alkali-acidic.

The process lubricants are applied to the pipes on the mills or when dipping the pipe bundle into the bath with lubricating solution. The methods of application of lubricating powder onto preheated pipe are also used.

The mechanical treatment is used to improve the quality of the pipe surface (turning, boring, grinding, polishing and sand-blasting). The mechanical treatment of individual areas of the pipe is used for the purpose of repair, cutting and facing of pipes as well as turning the pipes and cutting of thread on pipes. These operations are performed by lathes, grinding machines and special CNC machines, shot- and sand-blasting plants equipped with the system for feeding the product for treatment. The treatment of mother pipes by plastic deformation allows to decrease their curvature and ovality, to improve the diameter precision and to form the end of the required shape.

The elimination of defects related to distortion of shape of all the pipes (either round or shaped) is achieved through straightening. This is a set of operations aimed at:

  • correction of ovality of the pipe cross section;
  • correction of curvature of the pipes;
  • liquidation of twisting-off of shaped pipes.

The straightening is achieved through bending (either single or multiple), stretching, twisting, reeling and upsetting process.

The precision of the inner diameter of the pipe is improved by calibration. The calibration of the pipe ends allows to enhance the thread cutting conditions and to improve the quality and reliability of the threaded joints.

The finished pipes are tested and inspected to check conformity of their quality and geometry to the technical requirements specified in the documentation. Hydraulic and pneumatic pressure tests are used to reveals irregularities of the homogeneous metal layer and to check the strength of the welded joints and tightness of the threaded joints. It also allows performing the inspection as well as measuring the geometrical dimensions of the pipes.

To prevent the damage of metal due to corrosion when using the pipes in the oil and gas extraction, development of chemicals and materials, civil engineering and other spheres, the pipes are coated with various protective layers. The metallic layer is applied to the pipes with the diameter of up to 530 mm and the non-metallic ones are applied to the pipes with the diameter of up to 2,520 mm.

Specific operations for production of special pipes and new types of pipes belong to certain types of treatment. They include the welding of locks, coiling and welding of ribs, deburring after welding, etc. They include also operations for manufacture and screwing-on of fittings of threaded pipes.

There are special equipment and units to perform these operations.

The pipes of steels and alloys as well as laminated pipes are made by hot-rolling and extrusion. The metal properties, pipe geometry and requirements determine the hot rolling methods. These are methods have their preferential characteristics and disadvantages. However, hot rolling methods unite a number of manufacturing processes:

  • bloom piercing;
  • bloom preheating (if necessary);
  • rolling-off of the blooms into the intermediate-sized pipes;
  • heating of pipes (if necessary);
  • final formation of the pipe diameter and wall thickness.

When making the hot-rolled seamless pipes, the three stages are known:

1) bloom piercing: piercing in the roll-type screw-rolling mill or on the press. There is press-roll piercing consisting of combination of the piercing on the press with the rolling-off in the roll-type screw-rolling mill;

2) the rolling-off of the bloom into the pipe can be performed as longitudinal rolling of the stationary short mandrel or long floating mandrel (continuous multi-stand rolling mills); rolling on 2-hi or 3-hi screw-rolling mill; extrusion of the material into annular slit formed by the stationary mandrel (press for shaped pipes); on the planetary mills, push benches, etc.

3) the final formation of the diameter of the finished product and wall thickness takes place on longitudinal-rolling mills or on longitudinal-rolling mills in combination with rolling on the screw-rolled mill or other alternatives are used.

The method of rolling-off of the pipe billet or bloom is crucial for obtaining the seamless pipe products by hot-rolling. The pipe rolling lines are named according to this method.

Automatic pipe rolling mills

The bloom is longitudinally rolled on the mill in the automatic rolling mode. This is one of the most widespread methods for obtaining the pipe products (with the specified wall thickness). This is an ordinary non-reversing rolling mill with a 2-hi stand. When rolling the bloom, the round pass is usedж; the rolling is performed in two passages with a stationary shot mandrel. The mandrel is placed between the rolls.

Certain rolling lines are intended for manufacture of the pipes with various diameter. Small lines are intended for rolling the products with the diameter of less than 150 mm. Medium lines are intended for rolling the products with the diameter of 250 mm. Large lines are intended for rolling the products with the diameter of 426 mm or more. These lines are used to produce the rolled pipe products of carbon and alloy steels.

Continuous tube-rolling mills for obtaining the rolled pipe products with the diameter of 16-426 mm and the wall thickness of 2-25 mm mainly of carbon and low alloy (more rarely high allow) steels. This method is widely spread as the most advanced technique for pipe manufacture ensuring high productivity. The rolling is performed with the long mandrel and allows making long pipes.

Pilger pipe rolling mills for making the thick-walled pipes of various profile of application and pipes for oil extracting and processing industry.

The pilger-rolling method is a periodical method for obtaining the necessary wall thickness of the rolled pipe products. Unlike the adopted method of rolling (longitudinal), to which the rolling on the mill in the automatic mode is related, the pilger rolling ensures the versatility of the roll groove radius.

Small lines are intended for rolling products with the diameter of below 114 mm, maximum length of 60 m and minimum wall thickness of 2.5 mm. Medium lines are intended for rolling pipes with the diameter of 114-325 mm, maximum length of 40 m and minimum wall thickness of 5 mm. Large lines are intended for rolling the pipes with the maximum diameter of 700 mm, maximum length of 35 m and minimum wall thickness of 6 mm.

The Assel mills are intended for rolling precision thick-walled pipes of carbon steel. These pipes have the diameter of 40-200 mm and wall thickness of 0.09-0.25 of the diameter. On these lines, the main rolled pipe products are made of steels ШХ15, which are used for manufacturing race rings for frictionless bearings and to satisfy the machine-building needs.

The pipe push bench is intended for rolling thin-walled pipes of carbon and alloy steel. Their maximum length reaches 16 m, diameter is 21-219 mm and wall thickness is 2.5-10 mm.

The pipe section press is intended for obtaining the rolled pipe products with the diameter of 12.7-220 mm of alloy steels and alloys.

Automatic pipe rolling lines, pilger pipe-rolling mills, continuous rolling mills and Assel mills are the most commonly used in the world.

The widest range of the pipes is produced using the automatic pipe-rolling and pilger mills. The continuous pipe-rolling lines and Assel lines serve for obtaining the rolled pipe products with small and medium diameters. The first ones are intended for obtaining relatively thin-walled rolled pipe products, while the second ones are used for obtaining thick-walled rolled pipe products.

The Assel lines provide for production of rolled pipe products of precise geometrical dimensions, with their precision 1.5-2 times exceeding precision offered by other mills.

The costs of production when using all the above pipe-rolling plants is within 15-40 % of the primary cost of the product, while the metal price amounts to 60-80% of the costs. The coefficient of materials consumption is an important index of production efficiency. With the continuous Assel mills, its values are minimum.

Modern technologies and equipment for making seamless pipes

The rolling process technology is based on the material (metal) treatment under pressure. Over 80% of all the products are obtained by rolling. In the rolling process, the billets are passed through the gap between the rolls of the rolling lines, where they are squeezed by the rolls to get the necessary dimensions and shape. Three main kinds of the rolling: the longitudinal, cross and screw ones.

The longitudinal rolling is featured by squeezing of the billet getting into the gap between the rolls. The rolls rotate in the opposite directions. The roll axes lie in the same plane.

Under the action of the friction forces, the metal is drawn into the roll gap and moves perpendicularly to the plane passing through the axes of the rolls. The billet is squeezed to reduce the height, it is elongated and its section shape gets the gap shape. What is obtained from the starting material or billet after rolling, depends on the roll body structure. The slots on the both rolls are arranged symmetrically to the axis perpendicular to the roll axis; they form a pass. The starting material or billet being rolled just acquires the shape of this pass.

The cross rolling is featured by rotation of the rolls in the same direction. The axes of the rolls and the axis of the billet or material are parallel. The rolls as if roll around the billet. The distance between the rolls decreases. As it decreases, the billet diameter decreases too; it means that the billet elongates. The cross rolling method is used to roll the gears or bolt threads.

The screw rolling is also featured by rotation of the rolls in the same direction.

The axes of the rolls cross relatively to the billet axis at an angle. Due to it, the billet being deformed moves translationally while rotating, i.e. moves along its axis over the screw line. The screw rolling is used to obtain rolled seamless pipe products, periodic profiles, balls and rollers.

These kinds of rolling are mutually similar while having much in common. Both kinds could be implemented on the same universal mill, on which it would be necessary to change the position of the rolls in the space relatively to the billet without changing of the direction of their rotation.

Longitudinal rolling in a round pass

All the pipe rolling processes in round passes between two or three rolls could be divided technologically into two groups: rolling of the passes with or without a mandrel.

When performing the process of the first group, the thin-walled pipes are obtained when rolling-off the thick-walled hollow blooms. In so doing, the pipe wall is squeezed bly and its diameter decreases. The main objective of the processes of the second group consists in reducing the diameter of pipes, wherein the thickness of their wall can decrease, increase or remain invariable.

The first group of the rolling process, see three methods of rolling of pipes, all of these are on the mandrel:

a) stationary short mandrel;
b) long mandrel moving together with the pipe sleeve through the passes of the rolls;
c) long mandrel, in the passes with variable profile (periodical pilger rolling).

The most widespread technology of pipe rolling on a long cylindrical mandrel is implemented according one of the two existing variants of interaction with the bloom:

  • floating bloom (the mandrel moves together with the bloom);
  • moving under control (the mandrel moves over the specified curve).

Screw rolling

The screw rolling is used to obtain seamless pipes. It is also used to roll special products (balls, rings, bushes, bars with increased precision). To roll off the solid stock into the bloom on the screw-rolling units, the work rolls of various shape (barrel, tapered, cup-shaped and disk-shaped). The most widespread are the roll mills, on which the roll feed angle is adjustable and the rolling is performed at an angle. The translational or axial movement of the billet depends on the feed angle; the roll radius and peripheral speed depend on the rolling-off angle. The feed angle is the main process factor.

The first stage was characterized by conducting the piercing process with high degrees of total squeezing of the billet (up to 25%) and small feed angle (3-5°) with formation of the metal destruction zone at the mandrel end. The mandrel served for rolling off and further expansion of the billet cavity. The tool calibration was featured by large angles of taper of the rolls and short mandrel. The quality of the inner surface of the rolled off blooms and pipes (especially those of alloy steels) was unsatisfactory.

Some scientists proposed to perform the rolling-off without formation of the axial cavity in the billet. It was achieved by reduction of the squeezing at the mandrel end. Due to reduction of the total squeezing, the mandrel nose got beyond the gorge of rolls. In such rolling-off method, supposedly small forces were required to deform the “loose” (prepared for internal fracture) metal and the quality of inner surfaces of the blooms and pipes became better. However, blisters and scratches were often observed on the inner surface of the pipes even at this stage.

The third stage in the development of the pipe rolling process is related to the development of rolling process conditions based on increased values of the feed angle.

The new conditions are featured by the fact that the internal fracture is excluded in case of the feed angle of 18-20° with the possible squeezing degree (up to 25%). This idea was developed when performing the complex developments of the screw rolling process. The majority of these developments were based on the facts determining the destruction mechanism in the screw rolling process. They are:

  • strain disparity, relationship between the transverse strain and the longitudinal one; the strain disparity decreases with the increase of particular squeezing actions, number of squeezing rolls and dimensions of the squeezed area;
  • number of particular squeezing actions, temperature and speed effect; the increase of the number of particular squeezing actions increases the predisposition of metal to destruction;
  • dependence of the natural metal ductility determined by the chemical composition and metal melting.

It has not yet succeeded to develop a unified concept relatively to destruction of the axial zone of the billet. However, in the opinion of many scientists, the reduction of the predisposition to the cavity formation can be achieved in case of strain disparity and cyclicality as a result of increase of particular squeezing actions.

To assess the ductile characteristics of the metal in the screw rolling process, the samples can be tested for pierceability. The pierceability is understood as an ability of the body (billet, sample) to change irreversibly its shape without breaking the product integrity as the product is deformed on the screw-rolling line.

To investigate the process ductility of the metal in the newly developed deformation modes, the method of rolling of cylindrical billets with breaking them in the mill should be recognized as preferential. It allows assessing the deformability without destruction.

There are different opinions as regards the mandrel role in the predisposition of metal to the central destruction. In one on them, it is noted that the presence of the mandrel creates the resting forces on the side of its nose, reduces the axial strains in the center of the billet or even makes them compressive. This makes the internal fracture difficult.

Today, the development works on this matter are continued. The predisposition of metal to destruction is presented in the new developments from the point of the three main factors: feed roll angle, kind of the guide tool and ovality factor. Also, the investigation into the influence of the rolling-off angle and mandrel on the metal ability to destruction have been made.


Equipment for metallurgy

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