SSAW steel pipe, also known as spiral submerged arc welded steel pipe, is a spiral type welded steel pipe produced by the double-sided submerged arc welding method.
SSAW steel pipe is made using low carbon structural steel or low alloy structural steel strip. It is rolled into a pipe billet at a certain spiral angle and then the pipe seam is welded together. It can produce large-diameter steel pipe with narrower strip steel.
Its specification is indicated by the outer diameter * wall thickness. And the welded pipe should ensure that the hydraulic test. The tensile strength of the weld seam and cold bending performance meets the requirements.
Due to the increasing pressure of the pipe and the harsh conditions of use. The service life of the pipe should be extended as much as possible. Therefore, the main development direction of SSAW steel pipe is:
(1) the production of large diameter thick-walled pipe to improve the pressure resistance.
(2) design and production of new structures of steel pipe, such as double SSAW steel pipe, i.e. Double-layer pipe are made of strip steel welded in half the thickness of the wall. Not only that the same thickness of the single-layer tube strength, and does not cause brittle damage.
(3) the development of new steel, improve the level of smelting technology. The extensive use of controlled rolling and post-rolling heat-treatment process. Continuously improve the strength and toughness of the tube body and welding performance.
(4) vigorously develop coated pipes, such as the inner wall of the pipe coated with an anti-corrosion layer. Not only to extend the service life but also to improve the smoothness of the inner wall. Reduce fluid friction resistance, reduce waxing and fouling, reduce the number of pigs and reduce maintenance costs.
It is widely used in civil engineering construction, such as houses, bridges, and roads. Spiral pipe manufacturers are mainly located in North China and Northeast China. North China such as Shougang, Tangsteel, Xuansteel, Chengsteel, etc. And Northeast China such as Xilin, Beitai, Fugang, etc. These two regions account for about 50% or more of the total rebar production. SSAW steel pipe is widely used in natural gas, petroleum, chemical, electric power, heat, water supply, and drainage, steam heating. Hydroelectric penstock, thermal power generation, water sources, and other engineering fields. It is also used in long-distance transmission pipeline and piling, dredging, bridge, steel structure, and other engineering fields. Good quality SSAW steel pipes with thin and low transverse ribs are often unsatisfactory. The reason is that to achieve large negative tolerance. The reduction in the first few passes of the finished product is too large. The iron-type is too small and the hole type is not full.
SSAW steel pipe is also a welded pipe equipment. Its strength is generally higher than that of LSAW pipe. It can produce welded pipe of larger diameter with narrower billets, and can also produce welded pipe of different diameter with the same width billets. However, compared with the same length of straight seam pipe, the weld length increases by 30-100% and the production speed is lower. Therefore, most small-diameter welded pipes are welded using straight seam, and most large-diameter welded pipes are spiral welded.
The production process of spiral steel pipe. It is a spiral steel pipe made of strip steel coil, welded by automatic double-wire double-sided submerged arc welding, often extruded at the temperature of
1. The raw materials are strip steel coil, welding wire and welding flux. Strict physical and chemical inspection is required before investment.
2. The head and tail of the strip are connected by single or double wire submerged arc welding, and the coiled steel pipe is patched by automatic submerged arc welding.
3. Before forming, the strip is leveled, trimmed, planed, surface cleaned and conveyed, and pre-bent.
4. Electric contact pressure gauge is used to control the pressure of oil cylinder on both sides of the conveyor to ensure the smooth conveying of the strip.
5. Adopt external control or internal control for rolling forming.
6. Weld gap control device is adopted to ensure that the weld gap meets the welding requirements, and the pipe diameter, misalignment amount and weld gap are strictly controlled.
7. Both internal welding and external welding are performed by single or double wire submerged arc welding with American Lincoln electric welding machine, thus obtaining stable welding specifications.
8. The weld seam after welding is tested by online continuous ultrasonic automatic flaw detector, which ensures 100% nondestructive coverage of the spiral weld seam. If there is any defect, it will automatically alarm and spray out the mark, according to which the production workers can adjust the process parameters at any time to eliminate the defect in time.
9. Using air plasma cutting machine, the steel pipe is cut into small independent pieces.
10. After cutting into single steel pipes, the first three pipes of each batch should go through a strict first inspection system. Check the mechanical properties of the steel pipe, chemical composition, the fusion state of the weld seam, and the surface quality of the steel pipe. And through non-destructive testing to ensure that the steel manufacturing process qualified. After cutting into a single steel pipe, the first three steel pipes of each batch should undergo a strict first inspection system. Check the mechanical properties of the steel pipe, chemical composition, fusion state of the weld, surface quality. And through non-destructive testing to ensure that the steel manufacturing process qualified. After that, it can be officially put into production.
11. parts of the weld with continuous acoustic flaw detection traces, with artificial ultrasound and X-ray for re-inspection. If there are defects, the repair is then subjected to NDT until the defects are confirmed to be eliminated.
12. Strip butt welds and pipes with D-shaped joints intersecting with spiral welds are inspected by X-ray television or filming.
13. Each steel pipe is subjected to a hydrostatic test with radial seal pressure. The test pressure and time are strictly controlled by the steel pipe hydraulic microcomputer testing device. Test parameters are automatically printed and recorded.
14. The pipe end is mechanically processed to accurately control the verticality of the end face, bevel angle and blunt edge.
(1) The same width of strip can be used to produce tubes of various outside diameters.
(2) Tubes have good straightness and precise dimensions. The internal and external spiral welds increase the rigidity of the pipe body. Therefore, sizing and straightening are not required after welding. process.
(3) Easy to realize mechanization, automation and continuous production.
(4) Compared with other equipment of the same scale, it has the characteristics of small volume, small area, less investment .And fast construction.
(5) Compared with the same scale of straight seam welded pipe, the weld seam per unit length is longer. The production rate is lower.
Due to the large individual mass of SSAW steel pipes, they must be stacked outdoors. But inevitably, they have to be exposed to sun and rain. So the problem of rusting has been troubling the storage time and condition of SSAW steel pipe. Therefore, it is necessary for us to give a comprehensive answer to the knowledge of rust prevention of SSAW steel pipe.
Tools such as steel wire brushes are mainly used to polish the steel surface. cleaning and preheating of SSAW steel pipes can remove loose or buckled oxidation, rust, weld slag, etc. The rust removal by hand tools can reach Sa2 grade, and the rust removal by power tools can reach Sa3 grade. If the steel surface is firmly attached to the iron oxide, the effect of rust removal by tools is not satisfactory. And it cannot reach the depth of anchor pattern required for anti-corrosion construction.
Pickling is the use of solvents and emulsions to clean the surface of welded steel pipes (welded tubes) for low-pressure fluid transport. To remove oil, grease, dust, lubricants, and similar organic substances. However, it cannot remove rust, oxide layer, flux, etc. from the steel surface. Therefore, it is only used as an auxiliary means in the production of anti-corrosion.
In general, both chemical and electrolytic methods are used for pickling. Chemical pickling only is used for pipeline corrosion protection to remove oxidation, rust and old coatings. Sometimes it can be used as reprocessing after sandblasting rust removal. Chemical cleaning can make the surface reach a certain degree of cleanliness and roughness though. However, its anchor pattern is shallow and easy to cause pollution to the stacking environment of SSAW steel pipe.
The reasonable use of cleaning rusty pipe fittings can ensure that the pipe fittings will serve the production for a long time and create more production benefits.
In the production process of SSAW steel pipe, we need to pay attention to a series of matters. In addition to the following test items, according to API standards and other relevant standards as well as the special requirements of some users, destructive tests on steel, steel pipes, etc. are also required. Including the physical and chemical properties of incoming raw materials for a random inspection and 100% visual inspection of steel.
A. Oiling and marking: After the steel is qualified, it is oiled separately to prevent corrosion and marked according to the user’s requirements.
B. Leveling and milling. Use a flat steel anvil machine to make the original curl, and then mill the steel on both sides by edge milling machine, so as to meet the requirements of plate width, plate edge parallelism, and groove shape.
C. Shear Forming: Spiral curling along the outer edge to form a cylinder on the steel plate production line.
D. Butt cutting: Advanced double-sided submerged arc welding technology is used for pre-welding, internal welding, and external welding. The welded steel pipe is cut to specification length by plasma ruler.
Steel pipe making technology, which can be classified as (SML), is mainly used as internal oilfield transportation pipeline and small-diameter high-pressure natural gas pipeline for a few long-distance natural gas pipelines. The vast majority of long-distance pipelines use straight seam high frequency (ERW), spiral submerged arc (SSAW), and straight seam submerged arc (LSAW).
The following is a comparison of the technical characteristics and performance of these pipelines.
The method is divided into two forms: induction welding and contact welding, with hot-rolled wide coils as raw materials, pre-bending, continuous forming, welding, heat treatment, sizing, straightening, cutting, and other processes. Compared with spiral welding has the advantages of the short weld seam, high dimensional accuracy, uniform thickness, good surface quality, pressure resistance, etc. However, the disadvantage is that it can only produce thin-walled pipes of small and medium caliber, the weld seam is easy to produce gray leaf spots, and cannot fuse groove corrosion defects. In the city of gas, crude oil transportation in a wide range of applications.
Spiral submerged arc welded pipe (SSAW pipe) is welded in the forward direction with the forming angle (adjustable) of the hose reel in the center line of the forming pipe, and the side forming edge. The advantage is that it can produce a variety of diameter sizes of steel pipe, a wider range of adaptability to the raw material, the weld can better avoid the effect of the main stress. The disadvantage is that the geometric length of the weld is poorer than the long straight seam pipe, prone to cracks, porosity, slagging, welding local stresses and other welding defects, is a tensile stress state. General oil and gas pipeline design specifications for the spiral submerged arc can only be used for Class 3 and Class 4 areas. Raw materials, foreign countries to improve this process for steel plate forming and welding separate pre-welding and finishing welding, cold expansion after welding nearly UOE pipe welding quality. At present, the plant does not have the direction of improvement of this process.” West Gas East” is still a traditional process production, only expanding the diameter of the pipe end. The US, Japan and Germany reject SSAW across the board and consider trunk lines unsuitable for SSAW. small amounts of SSAW are used in Canada and parts of Italy Russia, with very strict supplementary conditions in place. Due to historical reasons, most domestic trunk lines still use SSAW.
LSAW is produced by pressing (coiling) steel plates on a mold or forming machine from thin plates, using double-sided submerged arc welding and flaring. The finished product has a wide range of specifications, good weld toughness, good ductility, uniform and dense. It has the characteristics of large diameter, large wall thickness, high pressure resistance, low temperature corrosion resistance, etc. In the construction of high-strength, high toughness, high-quality long-distance oil and gas pipeline required for the steel pipe, mostly large diameter thick-walled longitudinal welded pipe.
API standards specify that in large oil and gas pipelines, when 1, 2 areas through the alpine zone, submarine, urban densely populated areas, only when the special application of longitudinal submerged arc welding.
UOE: Small leafy steel plate after edge pre-hair, U-shaped forming, O-shaped internal welding, external welding, mechanical cold expansion, and other processes.
JCOE: Pre-welding, forming, and post-welding cold expansion according to “JCOE”.
Thermatool designs and manufactures spiral seam annealing systems for SAW (submerged arc welded) API pipe manufacturers.
Thermatool spiral seam annealing systems have all the basic features and benefits designed for longitudinally welded API pipe, but require the installation of specially “shaped” inductors.
These inductors are custom designed on a CAD system to precisely follow the helix angle for specific pipe diameter.
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After the production of SSAW steel pipe, it should be stored.If we don’t do some measures to keep its stability, it will rust and be corroded. So we will talk about how to increase the stability of the spiral welded pipe today. Generally speaking, we have followed methods:
High production efficiency. On the one hand, the wire length is shortened and the current and current density are increased. As a result, the penetration depth of the arc and the melting efficiency of the welding wire are greatly improved. Generally speaking, the melting depth on one side can reach 20 mm without grooving. on the other hand, due to the thermal insulation of the flux and slag, there is basically no heat radiation loss from the arc and very little welding spatter. Although the heat loss of melting flux is increased, the overall thermal efficiency is still greatly improved.
High weld quality. The slag provides good protection against air and the welding parameters can be stabilized by automatic adjustment. The technical level of the welder is not high, the weld composition is stable and the mechanical properties are good.
Good working conditions. In addition to reducing the labor intensity of manual welding operations, it has no arc radiation, which is a unique advantage of submerged arc welding.
Submerged arc welding is not as flexible as manual welding and is generally only suitable for horizontal positions or small slope welds. Workpiece edge preparation and assembly quality is required, which takes more working time. Since with submerged arc welding, we cannot see the formation of the molten pool and weld seam, so the welding specification must be strictly controlled.
Inferior SSAW steel pipes are prone to burrs because some inferior manufacturers have iron pan equipment. Prime Steel Pipe is positioned as an excellent carbon steel pipe manufacturer and exporter, and we have over 20 years of experience in producing SSAW steel pipe. Therefore, all SSAW steel pipes produced by Prime Steel Pipe have the best quality, and you can choose our spiral welded pipes with confidence. Generally speaking, burrs will scratch the appearance of SSAW steel pipe, and it is easy to break, the tendons are thin and low. And often appear full unsatisfactory phenomenon. The reason is that manufacturers in order to achieve large negative tolerances, waste a few passes before reducing the amount of iron type is small, it is full unsatisfactory. Easy to produce cracks. The reason is that the blank is adobe, adobe porosity, adobe in the cooling process due to thermal stress, cracks, and cracks after rolling.
SSAW steel pipe often has quality problems in production and use. So we need to identify the quality of SSAW steel pipe and test it according to certain ways and performance. Only then can it play an important role in the actual use. So how to identify the counterfeit spiral steel pipe method: in the appearance of the lumpy phenomenon is often present. Generally speaking, the overall effect of weighing will be better, mainly taking into account the cumulative error and probability theory of this issue. The lumpy surface is caused by severe wear and tear, irregular irregular defects in the appearance of spiral steel pipe. As a result of shoddy SSAW steel pipe manufacturers in pursuit of profits, often rolling the most standard. The appearance is prone to scarring.
Smooth and neat at the end of the top crop, high-quality SSAW steel pipe with uniform composition. And shoddy material due to poor quality, the cut end often has the naked eye, that is, uneven, and no metallic luster. And because the counterfeit manufacturers cut off the small head, the head and tail will appear large ears. The size of the inner diameter fluctuates greatly. The reason is that the l steel temperature is not stable Yin and Yang surface. The composition of the steel is not uniform. Folding refers to the appearance of spiral steel pipe to form a variety of folding lines, this defect is often throughout the longitudinal direction of the product. Folding is due to the pursuit of high efficiency manufacturers, the amount of depression is too large, the occurrence of ear, folding occurs in the next rolling, folding after the product bending will crack, thick-walled spiral steel pipe strength decline.
The temperature of the pseudo-material rolling is not standard, there is no metallic luster. There is a light red or similar to the color of pig iron. The cross-section is oval. The reason for this is that the manufacturers in order to save information, scrap rolling before the first two pressures are too high, the strength of this rebar is greatly reduced, and does not meet the specifications of the size of the rebar. Reason 2: Fake spiral steel pipe material is not uniform and has many impurities. Manufacturers of shoddy materials guide the equipment is simple and easy to stick to the steel, these impurities bite into the rolls and easily produce scars.
The large diameter double sawn steel pipe factory needs to test the product after the production is completed, especially its pressure resistance. Because we usually use it on the ground, it is required to have good resistance to pressure, so how to test it.
First, the two ends of the tested steel pipe are sealed with an end seal device, and then injected with low-pressure water. In the process of water injection, the air in the pipe is discharged through the exhaust valve. After the low-pressure water is filled, high-pressure water is injected into the pipe through the pressurization device to pressurize the gas. The specified test pressure is reached. After reaching the specified test pressure, the pressure is maintained for a predetermined period of time. If there is no leakage or deformation, the pressure is released.
Products that have been pressure tested can be used to ensure the effectiveness of the spiral pipe. Of course, it is necessary to carry out relevant anti-corrosion measures according to its use environment to ensure its effectiveness and longevity.
The use of SSAW steel pipe is relatively high and widely used, how should we choose the best, and pay attention to the quality when choosing.
The first method is a more professional testing method, that is, by testing the strength of the pressure vessel. It is common to use atmospheric pressure and water pressure to detect, through this way you can detect the working condition of SSAW steel pipe under pressure working environment, you can also detect the tightness of spiral steel pipe. Generally take the atmospheric pressure detection, because this is relatively high security, and if the water vapor pressure detection through the words, you need to remove the water on the spiral pipe, too much trouble.
The second method is also relatively simple, is through surface observation. With the naked eye to find spiral steel pipe in the welding and size of the problem, if necessary, you can also use standard samples and products for comparison to find the problem. Generally speaking, the regular steel pipe company is more perfect in production, on the other hand, hit the metal pipe, if the sound is crisp and the echo is not very dirty. Then it is called the latest selection of steel pipe, rather than scrap recycling.
These two methods are commonly used, you can choose a way to test. The more secure way is the best for the regular manufacturers to reduce the abuse in the process of use.