Friday, May 31, 2013

The quality of Tube billet has a influence on seamless steel pipe

The quality of the tube is an important factor in the decision quality seamless steel pipe. In order to ensure the normal perforation process and access to high-quality seamless steel pipe, tube geometry must be low magnification and the surface state and put forward strict requirements.

Tube diameter is too large, or through the large oval, make the piercing bite when conditions deteriorate, but also because of excessive compression tube diameter and to promote the production within the fold.

Mainly refers to the internal organization of shrinkage and center porosity, the accumulation of non-metallic inclusions and gas content, etc. Such stringent requirements, with the use of seamless steel tubes and carbon steel pipe varies.

The most important is the quality of the surface of the tube, because of any defect in the tube to the finished product will be seamless, but also defective parts often leads to stress concentration, defects by plastic deformation will deepen, lengthen.

To sum up in order to produce high-quality seamless steel pipe products, the good quality tube is a crucial step.

Thursday, May 30, 2013

Spiral welded pipe flaw detection testing

Spiral welded pipe steel is heated to quenching above the critical temperature, holding time, then quickly into the quenching agent, so that the temperature suddenly decreased, the critical cooling rate greater than the speed of rapid cooling, to obtain the martensite imbalance based organization heat treatment method. Quench can increase the strength and hardness of steel, but to reduce its plasticity. In China, good performance is still not suitable for large-diameter steel pipe produced magnetic flux leakage testing equipment, use of which is imported. Imports of magnetic flux leakage testing equipment is expensive for the majority of domestic enterprises difficult to accept.

The end of April this year, U.S. exports to China its most important oil pipeline starts "dual" survey, involving more than $ 2.6 billion, more than the tires safeguard the two billion U.S. dollars. Spiral welded pipe strength is generally higher than the Longitudinal, can produce a narrower diameter than the blank large pipe, you can also use the same width of billet production of different pipe diameters. API-5L (American Petroleum Institute, also known as line pipe; but with the same length of straight seam tubes, weld length of 30 to 100%, and the production rate is low. Generally spiral low-pressure fluid transport submerged arc welded pipe, double-sided or single-sided submerged arc automatic welding method as for water, gas, air and steam.
       
Past two years, including spiral pipe specifications, including a Sino-US trade friction and the weight of industry the hardest hit, the U.S. has several GB of steel products to China spiral pipe size weight "double reverse", the value of the case the case of seamless steel tube about four billion U.S. dollars, the U.S. International Trade Kunshan Teflon tube to the same italian decision is very high.
     
Quenching pipe commonly used quenching agents are: water, oil, alkali and salt solution, and so on. Oil pipe imported from Japan for more than half of total imports. Spiral welded pipe(SAWL pipe) for testing at home and abroad, the general magnetic or pressure leakage test. Spiral welded pipe strength is generally higher than the Longitudinal, can narrow billet production with a larger diameter pipe, you can also use the same width of the billet production of different pipe diameters. But with the same length of straight seam pipe compared to the weld length of 30 to 100, and a lower production rate. Therefore, the smaller diameter pipe actually use straight seam welding, large diameter spiral welded pipe is mostly used.

How to save energy for transporting fluid spiral steel pipe

Transmission fluid temperature is reduced to seize the autumn seasonal changes, to take reasonable open to stop running the cooling tower fan and pump room axial fans used to cool the work of measures to effectively reduce the power consumption. According to the professional management department's forecast, alone, can reduce the monthly cost of nearly 10 million. In the daily production run in 15 units (sets) cooling tower fan while running at full capacity, the total power per hour 1600kW, is a veritable big power. As steelmaking systems, continuous casting systems for water supply medium have special requirements, especially fine steel smelting, the water medium temperature control for stable product quality and develop new kinds of steel plays a vital role.

It also can be used to open the outdoor temperature and reasonable to stop the fan, to reduce power consumption, energy conservation purposes. Active users with points for each production line to get in touch, in-depth understanding of the specific requirements of the water temperature to determine the most reasonable range to meet production needs, while achieving cost reduction and efficiency purposes. Taking advantage of seasonal changes and outdoor temperature at night reduce the characteristics of staff on duty at the production site to track real-time detection of medium temperature water delivery method of data, timely adjustment of operating the fan, the fan running to minimize the number of units. Week has halved the number of running fans, power consumption is also reduced by half.

Like the steel pipe for transporting fluid, normally it is spiral pipe. besides, the spiral steel pipe also can be as piling pipe.

Friday, May 24, 2013

The technical requirment and quality inspection of ERW steel pipe

According to GB3092 "welded steel pipe low pressure liquid delivery" standard provisions, the nominal pipe diameter 6 ~ 150mm, nominal wall thickness of 2.0 ~ 6.0mm, the length of pipe is usually 4 to 10 meters, can be cut to length or times foot length of the factory. Steel surface quality should be smooth, does not allow folding, cracks, delamination, lap welding defects exist. Pipe wall thickness of the surface to allow no more than the negative deviation Scratch, scratch, weld dislocation, burns and scarring and other minor defects. Thickening and wall thickness to allow the weld seam welding bars in existence.

Welded steel pipe and mechanical tests should be done flattening test, and flaring test, and to meet the standard requirements. Pipe should be able to withstand a certain pressure, when necessary, 2.5Mpa pressure test, for a minute without leakage. Allows the use of eddy current testing in lieu of hydrostatic testing. Eddy current testing according to GB7735 "pipe eddy current test method" standard. Eddy current method is to probe the rack, testing and maintaining 3 ~ 5mm from the weld, by the rapid movement of the weld pipe comprehensive scanning, eddy current testing signal by the automatic processing and automatic sorting, achieve the purpose of testing.

After testing the pipe with the required length flying saw cutting, frame by turning off the assembly line. Pipe ends should be flat chamfer, marking, hexagonal tubes tied product packaging factory.

Seamless steel pipe line controlled cooling technology development and reduction of production

Control cooling technology is the production of rolling a very important technology, which after rolling of steel by controlling the cooling temperature and speed to improve the organization and performance of steel and, ultimately, good mechanical properties. With the control of cooling technology, it has been used in more mature sheet, strip, wire and other fields.

In order to control the cooling after rolling and applied technology to better promote the seamless pipe production, there have been a number of steel companies and steel research institutes have carried out the experiment. Initial results show that: the low C Low Mn, seamless steel tube rolling surface obtained after rapid cooling of high-strength, high toughness of acicular ferrite and tempered sorbite, grain refinement significantly, the overall integrated steel mechanical properties has increased significantly; for carbon steel pipe and alloy steel pipe, rolling fast cooling after the adoption of appropriate technology, in the rapid cooling and tempering steel dual role of their own under the heat, get the surface with high strength, high toughness of the back Fire sorbite, acicular ferrite, lower bainite and other organizations at the same time, internal ferrite network of reduced grain refinement, the overall strength and toughness of steel mechanical properties while improving, and not in the elongation diminished greatly improved toughness, improved the impact toughness of low rolling-state status. Rapid cooling process after rolling thick-walled seamless steel pipe thickness direction of the organization will make composite, the overall benefit of improved overall performance. In order to apply the results of the initial study production practices, jointly developed a controlled cooling after hot rolling seamless system to improve the overall performance improvement of the product.

After hot-rolled steel, mainly through radiation, conduction and convection heat in three ways. Among them, the steel surface and the convection heat transfer between the cooling medium is the main form of heat. Using a mixture of water and air as a cooling medium, "the aerosol cooling." Air-cooled, the steel surface heat faster than steel itself much slower thermal conductivity, temperature more even thickness direction of steel; aerosol cooling, heat pipe surface greatly improved the speed, direction of the thickness of the pipe near the surface there is a certain temperature gradient. About 950 ℃ hot-rolled seamless pipe from the finishing temperature to room temperature in the process, according to the cooling conditions, the austenite will be broken down into different tissue types of the product. Therefore, the thickness direction of the aerosol cooling pipe surface temperature near the difference in the thickness direction of the organization will inevitably lead to the diversification of steel; as steel internal rely on thermal conduction heat transfer, it is continuous throughout the temperature changes, so even if the formation of different organizations, organizations also exist between the transition zone, that is: different microstructure of a coexistence between the mixing zone, like steel from the composite layers of different types of organizations formed. Organizational diversity of the mechanical properties of steel change, showing the strength and toughness of the new combination of mechanical properties; organizational continuity of the pipe between the different types of organizations through the "transition area" closely, that no "layering" phenomenon; organization to make steel in the compound at different thickness, showing a different mechanical properties, composite materials play features and benefits.

As we all know, steel composite material has many unique advantages, such as: grain refinement of the surface can make the overall fatigue performance of steel in the construction sector, the steel surface fine-grained uniform refinement with full-face steel compared to have almost the same ability to suppress fatigue crack growth; surface high-intensity round or spherical structure, with a higher resistance to external pressure capability is commonly referred to as "eggshell theory." Seamless surface of high strength, high toughness will bring more benefits to its performance.

For high-quality carbon steel 20ф, 45ф structure pipe, test the use of air-cooled after rolling process to produce a more uniform equiaxed ferrite + pearlite; when using aerosol cooling process after rolling, although subsequent air cooling the steel in the slight temperature rise, due to the cooling pipe surface by aerosol and the subsequent role of alternating air-cooled, the surface temperature rise after the first drop, while the middle and inner wall temperature is relatively slow diffuse. This is bound to pipe wall thickness direction of the organization's diversity. 20 # steel pipe, ф140mm × 13mm size aerosol cooling after rolling microstructure, for example. In the steel surface to generate a 0.9mm thickness of bainite, and 0.9mm to 35mm thickness of the transition zone composite tissue. As is usually acicular ferrite dislocation density is higher than the equiaxed ferrite dislocation density, therefore, from the point of view of dislocation strengthening, acicular ferrite yield strength corresponding to equiaxed ferrite is greater than the corresponding yield strength. In addition, the aerosol cooling after rolling tube 20ф structure point of view, the equiaxed ferrite grain size is smaller than obtained by air-cooled equiaxed ferrite grain, fine grain strengthening from the point of view, the mechanical properties significantly improved.

Technical conditions of seamless steel tubes for different purposes

General seamless steel tube for conveying water, gas, oil pipeline and manufacture of fluid structural components, the response to its mechanical properties such as tensile strength, yield strength and elongation for the sample test. Duct generally work under conditions of pressure, also called pressure test done and flaring, squash, curling and other process performance tests. For large-scale long-distance crude oil, refined oil, natural gas pipelines with a pipe is to increase the carbon equivalent, welding performance, low-temperature toughness, stress corrosion under harsh conditions, corrosion, corrosion fatigue strength and corrosion environment and other requirements.

Ordinary boiler tubes used in the manufacture of structural pipe and superheated steam boilers boiling water pipes. High-pressure boiler tubes for high pressure or high pressure superheated steam boilers, heat exchangers and pipes for high pressure equipment. The steel thermal equipment in different conditions of high temperature and pressure of work, should ensure good surface condition, mechanical and technological properties. Generally to test its mechanical properties, flattening, and hydrostatic testing to do, high-pressure boiler tubes also asked to do the test and the grain size of more stringent non-destructive testing. Mechanical seamless steel pipe according to the application requirements to be a higher dimensional accuracy, good mechanical properties and surface condition. Regulatory requirements such as bearing high wear resistance, homogeneous, and strictly within the diameter tolerance. In addition to doing general mechanical performance test items, we need to do low-magnification, fracture, annealing (ball of the organization, mesh light, strip), non-metallic inclusions (oxides, sulfides, dot, etc.), de- indicators of carbon layer and its hardness test. Fertilizer industry often use high pressure seamless steel pressure of 2200 ~ 3200Mpa, working temperature -40 ℃ ~ 400 ℃ and the corrosive environment, transport chemical medium (such as ammonia, methanol, urea, etc.). Fertilizer industry with high-pressure seamless steel pipe should have a strong corrosion resistance, good mechanical properties and surface condition. In addition to doing mechanical properties, flattening, and hydrostatic testing, it should be based on different kinds of steel corrosion test streamlined accordingly, managers and more rigorous degree of non-destructive testing. Petroleum, geological drilling pipe at high pressure, alternating stress, corrosive, harsh environments, it should be a high intensity level, and to wear, torsion and corrosion-resistant properties. According to the different grades of steel should be done tensile strength, yield strength, elongation, impact toughness and hardness tests. Used for oil well casing, tubing and drill pipe, is a detailed breakdown of the grade, category, and for different environmental, geological conditions selected by the user's own additional requirements for high technical requirements, to meet different specific needs. Chemical, petroleum cracking, aviation and other machinery industry with a variety of acid-resistant stainless steel pipe and mechanical properties than do the pressure test, but also specifically for the intergranular corrosion test, flattening, flaring and non-destructive testing and other tests.

Thursday, May 23, 2013

Large diameter hot rolled carbon steel pipe

Thermal expansion of large-diameter carbon steel pipe products, as smelting, rolling main line extension, he used the "medium frequency heating, hydraulic push system" Expanding process, our factory has three advanced thermal expansion of pipe production line can be a variety of to 820mm diameter steel pipe expansion following a variety of specifications. In recent years, large-diameter seamless steel pipe factory has formed a variety of full scale structural systems in the oil pipeline and gas pipeline, building structures, petrochemical and other industries, to specifications, superior quality, quick delivery, reasonable price and other advantages by industry praise. Products are widely used in aerospace, chemical, construction, food, industrial control, medical, nuclear power plant, oil and gas development and production, transportation and seabed exploration and other fields.
       
The performance indicators to meet the user requirements, product quality has been recognized by the user, to fill our large diameter thick-walled tube of such gaps. Seen above, the heat expansion technology is well established, quality has been very stable, the user of the product design to meet the variability and overall product cost reduction rate.

The development and main manufacturing method of spiral steel pipe

Spiral steel pipe in the proportion in recent years stabilized at 42% to 45%, the pipe on the rise. Spiral steel pipe and welded steel pipe is more variety of materials, reliability and adaptability, especially adapted to thick and steel production. The main problem is high investment, high cost, complex manufacturing process, wall thickness and ovality tolerances. The welded pipe is actually a plate of deep-processed products, the price of similar conditions, spiral steel pipe market competitiveness and improve its reliability, with the continuous improvement of the quality of steel plate and pipe technology and equipment level, part of the spiral steel occupy the market, there is the possibility of welded pipe replaced, but only very limited areas.

Spiral steel hot rolling process is the main manufacturing methods, accounting for 80% of heat production Seamless Pipe Mill production of varieties and quality levels in addition to mill their own skills, but to a large extent constrained by the smelting and casting Therefore advanced smelting process should refer to the complete process management process. International companies are mostly well-known spiral steel pipe factory, or a complete professional steel company, by outsourcing manufacturing spiral pipe billet is difficult for enterprises in the fierce competition in the market share steady position. Using an electric arc furnace smelting or refining a VD of LF handle a full vacuum casting casting tube round protection of a hot strip mill (NPN, PQF) a process, is the current international advanced sawl pipe production process, using the above process can produce such as OCTG, high-pressure boiler tubes, low-alloy tubes. Tianjin Pipe Corporation, Baosteel Trading (steel) company, Anshan Iron and Steel seamless factory, Baotou seamless factory are to achieve the above process, climbed into steel seamless and Hengyang Steel Tube Company is also supporting projects to build did not pay close attention to the recent realization of the above process can be process. For the smelting equipment, electric arc furnace or converter capacity of not less than 70 a lOOt, create conditions for the ladle refining, full attention should be rolling mill line inspection tools and automatic control system, equipped with advanced detection systems for positioning and high-pressure oil pipe boiler tube production line, should be equipped with a high level of heat treatment and processing systems, the progressive realization of billet hot charging of heat delivery and on-line often, controlled rolling and air cooling and other processes.

The main purpose of anticorrosive spiral pipe

Different industries and areas of corrosion in a pipe, spiral steel corrosion in concrete can be used to show the industry an important role and performance. Different industries have an important supply. SAWL pipe corrosion classification and use: according to different production methods it appropriate classification. According to different production methods can be divided into hot-rolled pipes, cold-rolled, cold drawn tubes, squeeze tubes. Tube extrusion method is about to heat a good squeeze on the closed cylinder, spiral steel pipe corrosion there are many different production methods. Perforated stick together with the extruded rod movement, the extrusion die from the small hole in the extrusion. This method can produce smaller diameter carbon steel pipe. Spiral steel pipe corrosion can be divided into different categories and types, different types can be used in actual play an important role and nature of Eng, according to the normal use of methods and principles for use, to ensure that the use of the contribution. Required the use of cold-rolled, cold drawn or the combination of the two methods.

In roller cold rolling mill is usually carried out on Ruoyu get smaller and better quality of spiral steel pipe corrosion. Steel tank in the tapered hole and fixed head consisting of a conical hole in the ring rolling. Cold-drawing is usually 0.5 100T single chain or double chain drawing machine on. Cut into desired length, usually in the hot-rolled steel corrosion spiral pipe mill on automatic rolling production. Solid tube and remove surface defects upon inspection. End to end surface of the perforated tube-centering, and then sent to the furnace heating, punch on the punch. Perforation while continuing to rotate and move, roll, and the role of the head, the tube gradually formed within the cavity, said capillary. Spiral steel pipe corrosion and then sent automatically to continue rolling machine. Finally after all the whole entire wall thickness were, after sizing mill sizing, specification. The use of continuous rolling pipe mill producing hot-rolled thick wall steel pipe is more advanced methods.

The use of spiral steel pipe corrosion: as to withstand the liquid pressure, corrosion is extensive use of spiral pipe. There are special-purpose seamless pipe spiral steel pipe boiler corrosion, geology and oil with anti-corrosion steel pipe with a spiral steel and other corrosion. Supply three types according to different uses: a chemical composition and mechanical properties according to the supply; b supply by mechanical properties; c according to pressure test supply. By ab class supply pipe. Pressure test must be conducted. Spiral steel pipe for general use by the general corrosion of carbon steel, low alloy steel or alloy steel rolling, yield up, mainly for the transmission fluid pipe or structural components.

Wednesday, May 22, 2013

Features and uses of welded pipe


Welded steel pipe is welded to the strip or plate blank bent into a different way tube, and subjected to different welding methods, to obtain a certain strength of the weld to form a closed pipe section four weeks. Pipe production materials are widely applicable, including carbon steel, alloy steel, high alloy steel, non-ferrous metals and their alloys. Various sectors in the national economy: pipes are widely used in water engineering, petrochemical industry, chemical industry, power industry, agricultural irrigation, urban construction, is the development of 20 key products. For the transport of liquids: water supply and drainage. For gas transportation: gas, steam, liquefied petroleum gas. For structural purposes: as piling pipe for bridges; docks, roads, buildings and other structures tube.

The main advantages of pipeline:
1 low capital costs, and rail transport infrastructure charges can save more than 1/3, while the railway transportation capacity is twice;
2 simple construction, construction speed, usually laying on the ground, safe, reliable and adaptable to a variety of terrain;
3 transport operation, low cost, high degree of automation can be achieved with other methods of transportation than pipeline transport is the cheapest, and its rail freight is only 1/10, water, 1/2 or so.

Currently, the world piped oil, increasing the proportion of steam, and gradually expand the scope of delivery varieties, not only oil and gas, all kinds of chemical raw materials and products, but also in research piped solid material, the so-called slurry shipping. Oil pipeline transport development direction is toward large-diameter, high-pressure direction. Traffic and power is proportional to the pipe diameter 2.66. Increased pressure can be extended away from the station, reducing the number of stations, thus saving investment and management costs, while providing for the selection of sites for the larger mobility, changes in transmission capacity on adaptability. With oil and natural gas industry, pipeline construction has developed rapidly. World fifties pipeline length of approximately one million kilometers, the sixties up to 1.5 million kilometers, while in 1970 only U.S. pipeline length is reached 1,428,800 km, for the same period, more than three times the length of railways. According to incomplete statistics, in 1970 the total world's total pipeline length of 4.5 million km.

Tuesday, May 21, 2013

What is the condition of GB5310 seamless steel tube electric arc welding?


For GB5310 seamless steel tube in the arc welding conditions, the fusion zone width of about O. 133 ~ 050mm; of austenitic stainless steel is about 0.06 ~ 0.12mm. Distribution of melt composition of the ancient area of steel for most purposes, the same alloying elements greater than the solubility in the liquid phase solubility in the solid phase. Fusion zone is the junction of solid-liquid two-phase, solute atoms will be opposite from the solid liquid diffusion. Theoretical analysis and experiments proved that the solid - liquid interface on the distribution of solute concentration hut. Elements in the fusion zone (solute) concentration determined by the distribution of elements in the solid - liquid phase partition coefficient and diffusion coefficient. Carbon, sulfur, phosphorus and other elements in the fusion zone of segregation are quite serious. Completely solidified in the fusion zone cooling process, the elements of the diffusion of the opposite will occur, that is, elements from the weld to the base metal migration. The same kinds of welded steel, due to the diffusion of carbon in iron strong, it is time to high temperature homogenization.

The carbon and phosphorus in the combined area changes little baked, so the degree of uneven serious. Solid-liquid surface of the solute concentration distribution of solid - solid - liquid phase coexist, the dotted line - after condensation as the existence of chemical fusion zone heterogeneity, and it leads to physical heterogeneity, therefore, in the organization and performance of the fusion zone are on the uneven, as the weak parts of the welded joint. The formation of polycrystalline heat fusion zone is characterized by melting in a temperature range, this temperature range is the liquidus and solidus vertical distance between. Welding, the base metal on the solid - liquid interface is in between the two isothermal surfaces. Between the two so disheartened at the grain surface, due to anisotropy, the thermal conductivity of the grain direction are different, the results of some melting fast, some slow melting, so the solid - liquid interface to form undulating ellipsoid Therefore, the junction of the base metal and weld is not a line but a zone, called the fusion zone. Grains in the weld fusion zone is in a partially melted when heated state, when cooled to become columnar crystal substrate. The formation of the fusion zone (shadow line that was partially molten fusion zone grain) fusion zone width depends on the material of the solid hut - the temperature range between liquidus, the welded material thermophysical properties and organization of the state.

Carbon's role in stainless steel



Carbon is the main element of the steel industry, steel and organizational performance is largely determined by the carbon content in steel and its distribution in the form of carbon in the stainless steel is particularly significant. Carbon in the stainless steel in impact on the organization mainly in two aspects, one of the elements carbon stable austenite, and the extent of the role of large (approximately 30 times the nickel), and partly because the affinity of carbon and chromium is large, and the formation of chromium - series of complex carbides. Therefore, strength and corrosion-resistant candle performance both in terms of the role of carbon in stainless steel is contradictory.

Know the impact of the law, we can proceed from different application requirements, choose a different carbon content of stainless steel.

For example, the most widely used in industry, is the most basic steel - 0Crl3 ~ 4Cr13 five steel standard chromium content is 12 to 14%, that is, the carbon to form chromium carbide and chromium factors taken into account later decision, the purpose is to make the carbon that is combined into chromium carbide and chromium after the solid solution of chromium content not less than 11.7% of the minimum amount of chromium. In this five carbon steel pipe is as different strength and corrosion resistance is also different, 0Cr13 ~ 2Crl3 better corrosion resistance of steel but the intensity is lower than 3Crl3.