Characteristics of large-diameter straight-seam plastic-coated steel pipes: Its characteristics combine the characteristics of straight-seam steel pipes and the characteristics of epoxy resin. 1: Characteristics of straight seam steel pipes: Straight seam steel pipes have a simple production proc

Cleaning: 1. The workpieces and fixtures should be cleaned of oil, residual salt, paint, and other foreign matter before heat treatment. 2. The fixture used for the first time in the vacuum furnace should be degassed and purified in advance at a vacuum level not lower than that required by the wor

310S stainless steel thick-walled steel pipe has very good oxidation resistance and corrosion resistance. Because it contains a high percentage of chromium and nickel, it has high creep strength and can continue to operate at high temperatures. The working temperature is 1200 ℃, the continuous use t

Defects that are prone to occur in the submerged arc welding zone include pores, hot cracks, and undercuts. 1. Bubbles. Bubbles mostly occur in the center of the weld bead. The main reason is that hydrogen is still hidden in the welded metal in the form of bubbles. Therefore, the measure to elimina

Overview of the development of high-frequency straight seam welded pipe production, high-frequency straight seam welded pipe production technology and workshop layout, typical high-frequency straight seam welded pipe units and series, strip preparation equipment, continuous plowing unit, L-shaped

The quality of non-standard straight seam welded steel pipes is not only related to their service life but also to their subsequent use efficiency. So when we buy non-standard straight seam welded steel pipes, how can we buy high-quality non-standard straight seam welded steel pipes? What about stra

Thin-walled stainless steel pipes have the following outstanding advantages: excellent mechanical properties, superior wear resistance, good safety and health performance, good temperature resistance, good thermal insulation performance, smooth inner wall with low water resistance; beautiful, clean,

API standards stipulate that the internal and external surfaces of import and export oil casing shall not be folded, separated, cracked, or scarred. These defects should be completely removed, and the removal depth should not be less than 12.5% of the nominal wall thickness. Petroleum casing must un

With the wide application of stainless steel pipes, people's requirements for them are becoming higher and higher, and the processing technology has become diversified. Pickling is one of the processing techniques. Do you know why hydrogen embrittlement occurs in stainless steel pipes after pickling

Description of the main production processes of large diameter straight seam welded steel pipes: 1. Plate detection: After the steel plates used to manufacture large-diameter submerged arc welded straight seam steel pipes enter the production line, they first undergo full-plate ultrasonic inspection; 2. Edge milling: Use an edge milling machine to perform double-sided milling on both edges of the steel plate to achieve the required plate width, plate edge parallelism, and bevel shape; 3. Pre-bending edge: Use a pre-bending machine to pre-bend the edge of the board so that the edge of the board has a curvature that meets the requirements; 4. Forming: On the JCO forming machine, the first half of the pre-bent steel plate is stamped into a "J" shape through multiple steps, and then the other half of the steel plate is similarly bent and pressed into a "C" shape, and finally the opening is formed. "O" shape 5. Pre-welding: join the formed straight seam welded steel pipes and use gas-shielded welding (MAG) for continuous welding; 6. Internal welding: Use longitudinal multi-wire submerged arc welding (up to four wires) to weld the inside of the straight seam steel pipe; 7. External welding: Use longitudinal multi-wire submerged arc welding to weld on the outside of the longitudinal submerged arc welded steel pipe; 8. Ultrasonic inspection I: 100% inspection of the internal and external welds of the straight seam welded steel pipe and the base metal on both sides of the weld; 9. X-ray inspection I: 100% X-ray industrial television inspection of internal and external welds, using an image processing system to ensure the sensitivity of flaw detection; 10. Diameter expansion: The entire length of the submerged arc welded straight seam steel pipe is expanded to improve the dimensional accuracy of the steel pipe and improve the distribution of stress within the steel pipe; 11. Hydraulic pressure test: The expanded steel pipes are inspected one by one on a hydraulic pressure testing machine to ensure that the steel pipes meet the test pressure required by the standard. The machine has automatic recording and storage functions; 12. Chamfering: Process the pipe end of the qualified steel pipe to achieve the required pipe end bevel size; 13. Ultrasonic inspection II: Conduct ultrasonic inspection one by one again to check for defects that may occur after diameter expansion and hydraulic pressure of the straight seam welded steel pipes; 14. X-ray inspection II: X-ray industrial television inspection and pipe end weld photography on the steel pipe after diameter expansion and hydraulic pressure test; 15. Magnetic particle inspection of pipe ends: This inspection is performed to detect pipe end defects; 16. Anti-corrosion and coating: Qualified steel pipes will be anti-corrosion and coated according to user requirements.

1. The two main methods commonly used for anti-corrosion of steel pipelines are outer coating and cathodic protection. 2. Although most of the surface of the steel pipeline is covered by the coating, a slight leak will cause incredible corrosion rates, or even holes or cracks. Therefore, in the anti-corrosion of steel pipelines, the coating system and cathodic protection are generally used in combination to achieve 99.99% coverage to avoid unimaginable consequences in the future. 3. The cathodic protection selected for anti-corrosion of steel pipelines is divided into dedicated cathodic protection and impressed current cathodic protection. 4. The purpose of the anti-corrosion coating for 3PE anti-corrosion steel pipes is to form a continuous covering layer of insulating material to directly insulate the metal from the electrolyte in direct contact, so that no correct electrolytic reaction can occur. 5. Disconnected points during the coating laying process are called leakage points. The main reason for occurrence is during coating, transportation or installation. It may also occur due to coating aging, soil stress or movement of steel pipes in the soil. , failure to discover damage caused by a third party in a timely manner.

Welding and cutting of spiral steel pipe structures are inevitable in spiral steel pipe applications. Due to the characteristics of the spiral steel pipe itself, the welding and cutting of the spiral steel pipe has its particularities compared with ordinary carbon steel. It is more likely to produce various defects in its welded joints and heat-affected zone (HAZ). The welding performance of the spiral steel pipe is mainly reflected in the following aspects, high-temperature cracks. The high-temperature cracks mentioned here refer to cracks related to welding. High-temperature cracks can be roughly divided into solidification cracks, microcracks, HAZ (heat-affected zone) cracks, and reheating cracks. Low-temperature cracks Low-temperature cracks sometimes occur in spiral steel pipes. Because the main causes are hydrogen diffusion, the degree of constraint of the welded joint, and the hardened structure therein, the solution is mainly to reduce the diffusion of hydrogen during the welding process, appropriately perform preheating and post-weld heat treatment, and reduce the degree of constraint. The toughness of welded joints in spiral steel pipes is usually designed to contain 5% to 10% ferrite to reduce the susceptibility to high-temperature cracks. However, the presence of these ferrites leads to a decrease in low-temperature toughness. When spiral steel pipes are welded, the amount of austenite in the welded joint area is reduced, which affects the toughness. In addition, as the ferrite increases, its toughness value has a significant downward trend. It has been proven that the toughness of welded joints of high-purity ferritic stainless steel decreases significantly because of the mixing of carbon, nitrogen, and oxygen. The increase in oxygen content in the welded joints of some steels generates oxide-type inclusions. These inclusions become the source of cracks or the path for crack propagation, causing the toughness to decrease. Some steels are mixed with air in the protective gas, and the nitrogen content increases, producing lath-like Cr2N on the cleavage plane {100} of the matrix. The matrix becomes hard and the toughness decreases. σ phase embrittlement: Austenitic stainless steel, ferritic stainless steel, and duplex steel are prone to σ phase embrittlement. Because a few percent of the α phase is precipitated in the structure, the toughness is significantly reduced. The "phase" generally precipitates in the range of 600 to 900°C, especially around 75°C. As a preventive measure to prevent the occurrence of the " phase, the ferrite content in austenitic stainless steel should be reduced as much as possible. Embrittlement at 475°C, and when kept at 475°C (370-540°C) for a long time, the Fe-Cr alloy decomposes into an α solid solution with a low chromium concentration and an α’ solid solution with a high chromium concentration. When the chromium concentration in the α’ solid solution is greater than 75%, the deformation changes from slip deformation to twin deformation, resulting in 475°C embrittlement.

1. The uses of large-diameter stainless steel can be divided into oil well pipes (casing, oil pipes, drill pipes, etc.), pipeline pipes, boiler pipes, mechanical structural pipes, hydraulic support pipes, gas cylinder pipes, geological pipes, and chemical pipes (high-pressure fertilizers). pipes, petroleum cracking pipes) and ship pipes, etc. 2. The thicker the wall thickness of the solution, the more cost-effective and sensible it is; the thinner the wall thickness, its processing cost will appreciate significantly; 3. The product process determines its limitations, from the low precision of general seamless steel pipes: uneven wall thickness, low brightness tube appearance, high cost of fixed length, and the appearance of pitting corrosion, black spots are difficult to remove Walk; 4. Detection and plastic must be processed offline. So it's the higher pressure, high strength, mechanical structural wood that reflects its superiority. 5. The corrosion resistance of large-diameter stainless steel welded pipes depends on the alloy components contained in the steel. Chromium is the basic component of corrosion-resistant stainless steel. About 12% of the chromium is in steel. Chromium interacts with oxygen in the corrosive medium to form a thin oxide film (passivation film) matrix on the surface of the steel, which can prevent further corrosion of the steel. Remove chromium, stainless steel seamless steel pipe common alloy components you will find nickel, molybdenum, titanium, niobium, copper, nitrogen, etc., to meet the specifications of different stainless steel structures and properties. Reducer tubes, and steel pipe fittings, are widely utilized in various industries to provide flexibility in connecting sections of pipe in several installations. A reducer can connect two pipes of different diameters with one fitting. Pipe reducers are readily supplied in a range of dependent end-use commodity fittings produced in both imperial and metric sizes. Advantages of large diameter stainless steel pipes: 1. Welded steel pipes are produced continuously online. The thicker the wall thickness, the greater the investment in the unit and welding equipment, and the less economical and practical it is. The thinner the wall thickness, the lower its input-output ratio will be. 2. The technology of this product ensures that generally welded steel pipes have high precision, uniform wall thickness, and high internal and external brightness (the surface brightness of the steel pipe is determined by the surface grade of the steel plate), and can be arbitrarily cut to length. Therefore, it reflects its economy and aesthetics in high-precision, medium, and low-pressure fluid applications. 3. The production process of welded steel pipes is simple, with high production efficiency, low cost, and rapid development. The strength of spiral welded pipes is generally higher than that of straight seam welded pipes. Welded pipes with larger diameters can be produced from narrower billets, and welded pipes with different diameters can also be produced from billets of the same width. However, compared with straight seam pipes of the same length, the weld length is increased by 30 to 100%, and the production speed is lower. Therefore, smaller diameter welded pipes mostly use straight seam welding, while large diameter welded pipes mostly use spiral welding.

The steel bending pipe is a pipe fitting that changes the direction of the pipe. Steel bending pipe can be seen where pipes intersect, turn, go around beams, etc. Simmered steel bending pipe has the advantages of good elasticity, high-pressure resistance, and low resistance. Therefore, it is often used in construction. The main forms of steel bending pipe are elbows at various angles, U-shaped pipes, back-and-forth bends (or B-bends) arc-shaped steel bending pipes, etc. An elbow is a pipe fitting with an arbitrary bending angle, which is used at the turn of the pipe. The bending radius of the elbow is represented by R. When R is larger, the bending part of the pipe is larger, and the steel bending pipe is smoother; when R is smaller, the bending part of the pipe is smaller, and the bending is faster. Back-and-forth bends are pipe fittings with two bend angles (usually 135°). The distance between the center lines of the bent ends of the steel bending pipe is called the height of the back-and-forth bend, represented by the letter h. Indoor heating vertical branch pipes are connected to main pipes and radiators. When the pipes are connected to joints that are not on the same plane, they generally need to be bent back and forth. The U-shaped pipe is a semicircular pipe fitting. The distance d between the center lines of the two ends of the tube is equal to twice the bending radius R. U-shaped tubes can replace two 90° elbows and are often used to connect two circular wing-shaped radiators arranged one above the other. A curved steel bending pipe is a pipe fitting with three bending corners. The middle angle is generally 90° and the side angle is 135°. Curved steel bending pipes are used to bypass other pipes. Curved steel bending pipes are often used when piping sanitary equipment with hot and cold water supplies. The size of a steel bending pipe is determined by the pipe diameter, bending angle, and bending radius. The bending angle is determined based on the drawings and the actual conditions at the construction site. Then a template is made, simmered according to the template, and the bending angle of the simmered pipe fittings is checked according to the template to see if it meets the requirements. The sample can be made by simmering round steel. The diameter of the round steel is selected according to the diameter of the pipe to be simmered, 10-14mm is enough. The bending radius of steel bending pipe should be determined according to the pipe diameter, design requirements, and relevant regulations. It can neither be too big nor too small. Because the bending radius is too large, not only a lot of material is used, but the bent part of the pipe also occupies a large space, which will cause difficulties in pipe assembly; if the bending radius is too small, the pipe wall at the back of the elbow will be thinned due to excessive elongation. , reducing its strength, and the pipe wall on the inside of the elbow is compressed, forming a wrinkled state. Therefore, it is generally stipulated that the bending radius of hot-simmering steel bending pipe should not be less than 3.5 times the outer diameter of the pipe; the bending radius of cold-simmering steel bending pipe should not be less than 4 times the outer diameter of the pipe; the bending radius of welding elbow should Not less than 1.5 times the outer diameter of the pipe; the bending radius of the stamping elbow should not be less than the outer diameter of the pipe. When steel bends a pipe, the metal on the inside of the elbow is compressed and the pipe wall becomes thicker; the metal on the back of the elbow is stretched and the pipe wall becomes thinner. The smaller the bending radius, the more serious the thinning of the pipe wall on the back of the elbow, and the greater the impact on the strength of the back. To prevent the original working performance of the pipe from being greatly changed after bending, it is generally stipulated that the pipe wall thinning rate after bending shall not exceed 15%. When bending the pipe, due to the change in the thickness of the inner and outer walls of the bent section of the pipe, the cross-section of the bent section changes from the original circular shape to an elliptical shape. Changes in the cross-sectional shape of steel bending pipes will reduce the flow cross-sectional area of the pipe, thereby increasing fluid resistance and reducing the pipe's ability to withstand internal pressure. Therefore, the ellipticity of steel bending pipes is generally specified as follows: When the pipe diameter is less than or equal to 150mm, the ellipticity shall not be greater than 10%; when the pipe diameter is less than or equal to 200mm, the ellipticity shall not be greater than 8%. When water, gas steel pipes, and straight seam welded steel pipes are used to make cold simmering steel bending pipes or hot simmering steel bending pipes, the welding seam of the pipe should be located at 45° from the center line of the side. To prevent the pipe weld from cracking when bending. Wrinkles are generally not allowed in simmered steel bending pipes. If there are individual undulations, the height shall not be greater than the following regulations: when the pipe diameter is less than or equal to 125mm, it shall not exceed 4mm; when the pipe diameter is less than or equal to 200mm, it shall not exceed 5mm.

Stainless steel pipe is a kind of hollow long steel, which is used as a pipeline for transporting fluids, such as oil, natural gas, water, gas, steam, etc. Stainless steel tubes are lighter when they have the same bending and torsion strength. They are widely used in the manufacture of mechanical parts and engineering structures. They are also commonly used to produce various conventional weapons, barrels, and shells. For steel pipes subjected to fluid pressure that requires thicker pipe walls, hydraulic tests must be carried out to verify their pressure resistance and that they will not leak, soak, or expand under the specified pressure. Stainless steel pipes are divided into seamless and seam. Seamless stainless steel pipes are also called stainless steel seamless pipes. They are made of steel ingots or solid pipe billets through the perforation and then made by hot rolling, cold rolling, or cold drawing. The specifications of seamless steel pipes are expressed in millimeters of outer diameter × wall thickness. Commonly used 1Cr18Ni9Ti stainless steel pipes, the following takes 1Cr18Ni9Ti stainless steel pipe with a diameter of Ф159mm×12mm as an example to introduce its horizontal fixed welding method. 1. Welding analysis: 1. Cr18Ni9Ti stainless steel Ф159mm×12mm large pipe horizontal fixed butt joint is mainly used in nuclear power equipment and certain chemical equipment that require heat and acid resistance. The welding is difficult and requires high welding joints. The surface is required to be shaped, with moderate protrusions and not concave. PT and RT inspections are required after welding. In the past, TIG welding or manual arc welding was used. The former has low efficiency and high cost, while the latter is difficult to guarantee and has low efficiency. To ensure and increase the rate, the bottom layer is welded by TIG inner and outer wire filling method, and the MAG welding is used to fill and cover the surface layer so that the efficiency is guaranteed. 2. The thermal expansion rate and electrical conductivity of 1Cr18Ni9Ti stainless steel are quite different from those of carbon steel and low-alloy steel, and the molten pool has poor fluidity and poor forming, especially in all-position welding. In the past, MAG (Ar+1%～2%O2) welding stainless steel was generally only used for flat welding and flat fillet welding. In the MAG welding process, the length of the welding wire is less than 10mm, the swing amplitude, frequency, speed, and edge stay time of the welding gun are properly coordinated, and the action is coordinated. Adjust the angle of the welding gun at any time to make the weld surface edge fusion neatly and beautifully to ensure filling And cover layer. 2. Welding method: The material is 1Cr18Ni9Ti, the pipe fitting size is Ф159mm×12mm, using manual tungsten arc welding for bottoming, mixed gas (CO2+Ar) shielded welding and cover welding, vertical and horizontal fixed all-position welding. Preparation before welding: 1. Clean the oil and dirt, and grind the groove surface and the surrounding 10mm to give a metallic luster. 2. Check whether the water, electricity, and gas circuits are unblocked, and the equipment and accessories are in good condition. 3. Assemble according to the size. Tack welding is fixed by ribs (2 points, 7 points, and 11 points are fixed by ribs), or in groove positioning welding, but pay attention to tack welding.

3PE anti-corrosion steel pipes to refer to the insulation of the steel pipe to ensure that the internal temperature of the working steel pipe and the surface temperature together in a different working environment slows down or prevent corrosion and deterioration under the chemical and electrochemical action of the external medium, perhaps due to the metabolic activities of microorganisms. Anti-corrosion method. The anti-corrosion method is generally to apply a fine coating into the surface of the metal pipe that has passed the rust removal of blocking it from various corrosive media. This is also one of the most recent methods of steel pipe anti-corrosion. The outer wall anti-corrosion coating, the outer wall of the pipeline Types of coating materials and application conditions. To prevent corrosion in the pipe and reduce frictional resistance, the inner wall anti-corrosion coating is applied to the film on the inner wall of the pipe. The anti-corrosion and thermal insulation coating are used on the official roads to medium and small diameter hot crude oil or fuel. To reduce the heat dissipation of the pipeline to the soil, a composite layer of thermal insulation and anti-corrosion is added to the outside of the pipeline. If the outer protective pipe is a polyethylene pipe, there is no need to lose corrosion protection. Because polyethylene has excellent low-temperature resistance, good chemical stability, and most acid and alkali corrosion, it is insoluble in common solvents at room temperature and has low water absorption. Three-layer polyethylene anti-corrosion is one of the primary technology systems for external anti-corrosion of buried pipelines at home and abroad. It has good anti-corrosion function, low water absorption rate, and advanced mechanical strength. In recent years, it has been more and more widely used in domestic buried water, gas, and oil pipelines.

1. The premise must be polished The galvanized layer of the weld must be polished away, otherwise air bubbles, trachoma, false welding, etc. will occur. It will also make the weld brittle and reduce the rigidity. 2. The welding characteristics of galvanized steel Galvanized steel is generally coated into a layer of zinc on the outside of low-carbon steel, and the galvanized layer is generally 20um thick. At the same time, zinc and iron can form brittle compounds between metals. These brittle phases reduce the plasticity of the weld metal and cause cracks under tensile stress. If the fillet welds are welded, especially the fillet welds of the T-shaped joints, penetration cracks are most likely to occur. When welding galvanized steel, the zinc layer on the groove surface and the edge will oxidize, melt, evaporate and even volatilize white smoke and steam under the action of the arc heat, which can easily cause weld pores. Secondly, due to the evaporation of zinc, a large amount of white smoke is emitted, which is irritating and harmful to the human body. Therefore, the galvanized layer of the weld must be polished. 3. Welding process control The pre-welding preparation of galvanized steel is the same as that of general low-carbon steel. It should be noted that the groove size and the nearby galvanized layer must be carefully handled.

Welded steel pipes, also called welded pipes, are steel pipes made by welding steel plates or steel strips after crimping. Welded steel pipe has a simple production process, high production efficiency, many varieties and specifications, and less equipment, but its general strength is lower than the seamless steel pipe. Since the 1930s, with the rapid development of high-quality strip, continuous rolling production and the advancement of welding and inspection technology, the quality of welds has been continuously improved, and the variety and specifications of welded steel pipes have increased, and they have replaced non-metallic steel in more and more fields. Seam the steel pipe. Welded steel pipes are divided into straight seam welded pipes and spiral seam welded pipes according to the form of welds. The longitudinal welded pipe has a simple production process, high production efficiency, low cost, and rapid development. The strength of spiral seam welded pipes is generally higher than that of straight seam welded pipes. A narrower blank can be used to produce welded pipes with larger pipe diameters, and a billet with the same width can also be used to produce welded pipes with different pipe diameters. However, compared with the straight seam pipe of the same length, the weld length is increased by 30-100%, and the production speed is lower. Therefore, most of the smaller diameter welded pipes adopt straight seam welding, and the large diameter welded pipes mostly adopt spiral welding.