What is a spiral steel pipe?

Spiral steel pipe is made of steel coil, extruded at room temperature, and then adopts double wire and double-sided submerged arc welding technology.

　　Spiral steel pipe, also known as spiral or spiral spiral steel pipe, is a low-carbon steel or low-alloy structural steel strip rolled into a tube at a certain spiral angle (called forming angle). The tube is made of welded joints and can be produced with narrow strips and large diameter tubes.

　　During the forming process of spiral welded steel pipe, the steel plate is deformed evenly, the residual stress is light, and there are no scratches on the surface. Spiral steel pipe has more flexible thickness and diameter, especially when manufacturing high-grade thick pipes with small and medium apertures, these technologies have unparalleled advantages in meeting your needs.

　　Spiral steel pipe production process

　　1. Unwinding plate probe: After entering the unwinding plate production line, the first full-plate ultrasonic flaw detection is carried out.

　　2. Leveling milling: The flat steel anvil machine makes the original curling, and then the double-sided steel milling is carried out through the milling machine to meet the requirements of plate width, plate edge parallelism and groove shape.

　　3. Shearing: Curl the steel plate production line into a tube along the outer edge.

　　4. Butt cutting: Double-sided submerged arc welding uses advanced technology for pre-welding, internal welding and external welding. Ion feet are cut into welded spiral tubes of standard length for use, etc.

　　5. Visual inspection: Some basic parameters are checked by professional technicians.

　　6. Ultrasonic flaw detection: 100% detection of internal and external welds and parent materials on both sides of the welds.

　　7. X-ray detection: 100% X-ray industrial television inspection image processing system for internal and external welds to ensure the use of detection sensitivity.

　　8. Pressure test: Spiral steel pipe hydraulic testing machine tests each pipe to ensure that the test pressure pipe meets the required standards.

　　9. Chamfered flat head: After the spiral steel pipe is inspected, the pipe end is processed to meet the pipe end groove size

　　10. Final inspection: Ultrasonic and X-ray re-detection and magnetic particle flaw detection of the spiral steel pipe end to check whether there are problems and defects at the end of the welded pipe.

　　11. Oiling and marking: Spiral steel pipes are oiled after passing through to prevent corrosion, and marked according to user requirements.

　　Eliminate the magnetic field generated around spiral steel pipes

　　The reason for the magnetic field of spiral steel pipes During the welding process, DC welding is used. On the welding line, due to the large current at the position of the welding head, a strong magnetic field is generated. Under the action of the magnetic field, the magnetic moment of the pipe tends to obtain a magnetic field with the same direction as the external magnetic field. When the welding is completed, the magnetic field gradually decreases until it disappears. Due to the hysteresis phenomenon, the residual magnetic flux density in the pipe body is what we usually call residual magnetism.

　　The harm of the magnetic field of spiral steel pipes The residual magnetic effect, image intensifier and electron beam deflection, and the "s" type distortion generated by the industrial television image system affect the porosity, slag and other natural defects, especially the detection rate of linear natural defects such as incomplete penetration and cracks.

　　With the changes and improvements in the steel grades of pipelines of X-ray image intensifier TV systems, residual magnetism is particularly prominent.

　　The existence of residual magnetism, the ring docking in the pipeline will produce a local arc phenomenon, and the welding quality is good.

　　Residual magnetism seriously affects construction

　　Quality The AC demagnetization method of spiral pipe is the most common method:

　　1. Wrap a coil around the outside of the steel pipe, pass the coil through AC, and slowly reduce the current of the AC until it drops to zero. Demagnetization result: The physical properties of the spiral steel pipe have not changed. However, when it encounters the external magnetic field again, the spiral steel pipe is also magnetized.

　　2. Through the heat treatment process, it can be demagnetized more thoroughly. However, after demagnetization, the hardness and stiffness of the spiral pipe will change. When it encounters the external magnetic field again in the future, plus the magnetic field is removed, the steel pipe can basically have no residual magnetism.

　　3. The heat treatment process is probably: oxygen-free heating to a certain temperature, and then slowly cooling to room temperature in 72 hours.

　　Analysis of the cause of misalignment of spiral steel pipe

　　If the production process of spiral steel pipe is unreasonable during the production process, the machine parameters should be regarded as deviations, especially large-diameter spiral steel pipes, which is often called misalignment.

　　Analysis of the causes of misalignment of spiral steel pipes is very necessary. The following are common causes of misalignment.

　　1. The camber of the strip is the most important factor causing the misalignment. When forming the spiral welded pipe, the camber of the steel strip will constantly change its shape, causing the weld gap to change, resulting in seam opening, misalignment, and even biased edge.

　　2. The head and tail of the strip have a large degree of reinforcement to the weld. If it is not handled properly during overmolding, it is easy to cause a larger reverse side.

　　3. Due to the poor shape and dimensional accuracy of the untrimmed strip head and tail, it is easy to cause the wrong side caused by the hard bending of the butt strip.

　　4. The poor edge condition of the strip is another important reason for the edge error.

　　Therefore, observing the situation after the camber of the plate and strip roll, by controlling the vertical roller, the disc can cut and remove part of the camber to form a continuous control and correction of the camber of the strip, which is an effective way to reduce the generation of wrong sides in the production process.

　　For the spiral steel pipe processing plan for production, the wrong side that has been completed is as follows:

　　1. Polish the position of the wrong side, and then weld

　　2. If the wrong side often occurs, the equipment can be replaced.

　　A connection method for large-diameter spiral steel pipes

　　The most common method for connecting large-diameter spiral steel pipes is welding, but in some projects, it is usually used in the form of screw connection, flange connection, socket connection and groove connection.

　　The most common method for connecting large-diameter spiral steel pipes is welding, but in some projects, it is usually used in the form of screw connection, flange connection, socket connection and groove connection.

　　Welding and flange connection - What is spiral steel pipe?

　　Welding and flange connection

　　Connection characteristics

　　Welding and flange connection belong to the traditional pipeline connection of l spiral steel pipe, which is far from meeting the market demand in terms of safety, sealing performance, space cost, repair efficiency, etc.

　　Groove pipe connection - What is spiral steel pipe?

　　Groove pipe connection

　　Groove pipe connection technology, also known as clamp connection technology, has become the first technology for connecting liquid and gas pipelines. Although the technology was developed later in China than abroad, it was quickly accepted by the domestic market due to its advanced technology. The application of grooved pipe connection technology makes the complex pipeline connection process simple, fast and convenient. Pipeline connection technology has made great strides forward.

　　Groove connection pipe fittings include two types of products: (1) the connection sealing effect of pipe fittings with rigid joints, flexible joints, mechanical tees and flange grooves; (2) the transition effect of connecting pipe elbows, tees, crosses, reducers, blind plates, spiral welded pipes, etc. The connection sealing effect of groove connection pipe fittings mainly consists of three parts: sealing rubber rings and clamps and locking bolts. The inner lining rubber sealing ring is located on the outer edge of the connecting pipe, and follows the roller D groove of the front row, and is buckled on the outside of the rubber ring clamp, and then connected with two bolts. Because the rubber sealing ring and the clamp adopt a special sealing structure design, the groove fittings have good sealing performance, and the sealing performance increases accordingly with the increase of internal fluid pressure.

　　Groove connection makes pipeline connection operation simple, which is conducive to construction safety, good system stability, convenient maintenance, and saves working time, so it has good economic benefits. Clamp connection, although the price of the clamp single accessory is higher, the comprehensive benefit of the entire pipeline installation is higher than that of flange connection.

　　Suitable for liquid and gas pipeline connection Pipe clamp connection

　　Pipe clamp connection - What is spiral steel pipe?

　　Connection characteristics

　　Coupling connection is an advanced pipe connection method, which can be set or buried, with good joint rigidity and flexible joints. Therefore, it has a wide range of applications.

　　Applicable

　　Scope: According to system c, it can be used for fire water systems, air conditioning hot and cold water systems, water supply systems, petrochemical pipeline systems, thermal power and military pipeline systems and sewage pipeline systems, etc.

　　According to piping materials: it can be used to connect steel pipes, steel pipes, stainless steel pipes, plastic pipes, ductile iron pipes, plastic pipes and steel pipes with thick-walled joints and flange joints.

　　Classification of spiral steel pipes 1. Low-pressure fluid pipes are welded steel pipes

　　Generally called clarinet pipes. Welded steel pipes are used for conveying general low-pressure steam heating fluids such as water, gas, gas, and oil. The pipe wall thickness is divided into ordinary steel and thicker steel; the pipe edge is formed into a form without steel pipes and pipe steel. The pipe specification uses the nominal diameter (mm), which is an approximate value of the diameter. Traditionally used in inches. In addition to being used to transport fluids, low-pressure fluid welded steel pipes also use a large number of galvanized welded low-pressure fluid original steel pipes.

　　2. Low-pressure fluid galvanized welded steel pipes, also known as galvanized welded steel pipes, commonly known as white pipes. Hot-dip galvanized welded steel pipes are used to transport general low-pressure fluids such as water, gas, air, oil and steam heating, warm water, or other purposes. The pipe wall thickness is divided into ordinary galvanized steel pipes and thick galvanized steel pipes; the pipe ends are divided into unthreaded galvanized steel pipes and threaded galvanized steel

　　The form of the pipe. Pipe specifications and nominal diameters, the nominal diameter is an approximate value of the diameter. Traditionally, it is usually expressed in inches, such as 11/2, etc.

　　3. Ordinary carbon steel wire casing is the top steel wire used to protect electrical installation projects in industrial and civil buildings and installation machinery and equipment.

　　4. Straight seam welded steel pipes are parallel to straight seam welded pipes. Usually divided into metric welded steel pipes, welded pipes, transformer cooling pipes, etc.

　　5. The spiral submerged arc welded pipe for pressurized liquid transportation is made of hot-rolled steel strip coils, which are often in a warm spiral shape. Double-sided submerged arc welding is used for spiral seam steel pressure fluid transportation. Strong pressure steel, good welding performance, through various strict scientific inspections and tests, safe and reliable to use. Large pipe diameter, high transportation efficiency, can save investment in laying pipelines. Mainly used for oil pipelines and natural gas.

　　6. High-frequency spiral welded steel pipe for pressure transmission fluid is a hot-rolled steel strip coil pipe, which is often in a warm spiral shape and lap welding method. High-frequency spiral seam is a welded steel pipe for pressure fluid transportation. Strong pressure steel, plastic, easy to weld and machine processing; through various strict scientific inspections and tests, safe and reliable

　　, large pipe diameter, high transportation efficiency, saving investment in laying pipelines. Mainly used for laying pipelines for transporting oil, natural gas, etc.

　　7. Generally, low-pressure liquid infusion spiral submerged arc welded pipes are made of hot-rolled steel strip coils, often in a warm spiral shape, and are made of water, gas, air and steam low-pressure liquid conveying surface acoustic wave tubes using double-sided or single-sided automatic submerged arc welding.

　　8. Generally, low-pressure liquid conveying spiral seam high-frequency welded steel pipes are made of hot-rolled steel strip coils, often in a warm spiral shape, and are made of general low-pressure liquid conveying spiral seam high-frequency welded steel pipes using high-frequency lap welding.

　　9. Spiral welded steel pipe piles are made of hot-rolled steel strip coils, often in a warm spiral shape, and are made of steel pipes for infrastructure piles such as civil engineering structures, piers, and bridges using double-sided submerged arc welding or high-frequency welding.

　　Characteristics of spiral steel pipes: The longitudinal production process is simple, efficient, low cost, and rapid development. Spiral welding is generally higher than that in the longitudinal direction, and the billet can be reduced to produce large-diameter pipes, and the same width of steel billets can also be used to produce pipes of different diameters. However, compared with the same length of straight seam pipes, the weld length is 30% to 100%, and the productivity is lower. Therefore, small-diameter pipes are mostly straight-seam welded, and large-diameter spiral welded pipes are mostly straight-seam welded.

　　Production control measures for thick-walled spiral steel pipes The production control of thick-walled spiral steel pipes is to increase the plastic toughness of the steel pipe, improve the cleanliness of the molten steel, reduce harmful inclusions, and improve the overall quality of the steel pipe. During the production process, a reasonable cooling system is adopted to avoid internal cracks and improve the quality of the steel pipe from multiple aspects.

　　SSAW steel pipes reasonably control the heating temperature during the production process, and select the optimal heating temperature by determining the thermoplastic curve. The heating of the steel billet should also pay attention to sufficient insulation time to reduce the deformation resistance and increase the toughness of the thick-walled spiral pipe plastic.

　　The SSAW steel pipe production process requires more procedures. The last step is to reduce the roller speed. The roller speed is the key parameter of the perforation process. The roller speed changes from low to high during the process, and there is a critical start roller speed. When the roller speed is low, the tube billet is prone to form cavities; when the roller speed is high, the tube billet and the structural spiral steel pipe are prone to stratification defects. In order to eliminate the delamination defects of tube blanks and structural spiral steel pipes, the speed of the rollers should be reduced to below the critical roller speed at which delamination begins.

　　Application:

　　Spiral welded pipes are mainly used in tap water projects, petrochemicals, chemicals, electricity, agricultural irrigation and urban construction. It is one of the twenty key products developed in China. Liquid transportation purposes: water supply, drainage, sewage treatment projects, mud transportation, marine water transportation. For gas transportation: gas, steam, liquefied petroleum gas. Structural use: as piling pipes, as bridges; piers, roads, building structures, marine piling pipes. Spiral welded pipes undergo rigorous physical and chemical tests before being put into use. Spiral seam submerged arc welded pipes for pressure fluid transportation are mainly used for pipelines for transporting oil and natural gas. The steel pipe has strong pressure bearing capacity, good plasticity, and is easy to weld and process. In general, spiral submerged arc welded steel pipes for low-pressure fluid transportation use double-sided automatic submerged arc welding or single-sided welding methods for submerged arc welded steel pipes for transporting low-pressure fluids such as water, gas, air, and steam.

　　For gas transportation: gas, steam, and liquefied petroleum gas. Structural use: as a pile pipe, as a bridge; piers, roads, building structures, marine pile pipes. Spiral pipes have strong pressure bearing capacity, good plasticity, and are easy to weld and process; general low-pressure fluid conveying spiral steel pipes use double-sided automatic submerged arc welding or single-sided welding methods, general low-pressure water, gas, air and steam submerged arc welding steel pipes, and straight seam steel pipes are used for fluid transportation. Nowadays, the commonly used large-diameter spiral steel pipe standards are generally divided into (partial standards, ordinary fluid conveying pipelines are also called spiral pipes), national standards, also called oil and gas industry conveying steel pipes. Technical conditions: Grade A steel pipe (steel pipe required so far) (American Petroleum Institute, also known as pipeline steel pipe; divided into two levels) Large-diameter coated steel pipe is made of plastic coated on the basis of large-diameter spiral welded pipe and high-frequency welded pipe. If the diameter of the steel pipe reaches 1200mm, it can be coated with PVC (polyvinyl chloride), polyethylene (PE), epoxy resin and other plastic coatings with various properties according to different needs. It has good adhesion, corrosion resistance, chemical corrosion resistance such as strong acid and alkali, non-toxic, non-corrosive, wear-resistant, impact-resistant, strong permeability resistance, smooth pipe surface, no material adhesion, can reduce resistance during transportation, improve flow and transmission efficiency, and reduce transmission pressure loss. There is no solvent in the coating, no material leakage, so it will not pollute the conveying medium, thereby ensuring the purity and hygiene of the fluid. It can be used alternately in the range of -40°C to +80°C, will not age, because it will not crack, and can be used in harsh environments such as cold areas. Large-diameter coated steel pipes are widely used in engineering fields such as tap water, natural gas, petroleum, chemical industry, pharmaceuticals, telecommunications, power, and ocean.

　　SSAW pipe spiral submerged arc welding (SSAW) means its forward direction and forming pipe

　　Centerline hose reel forming angle (adjustable), side mold edge welding and weld them into a spiral shape.

　　(Spiral Submerged Arc Welded Pipe) SSAW Pipe: SSAW pipe is produced by spiral (helical) welding of steel coils and has a cost advantage over LSAW pipe because the process uses coils instead of steel plates. Therefore, SSAW pipe may be superior to LSAW pipe in applications where spiral welding is acceptable. Both LSAW and SSAW pipes can compete with ERW pipes and seamless pipes in the diameter range of 16"-24". SSAW pipe is mainly used in the oil and gas industry to transport flammable and non-flammable liquids and steel structures.

　　SSAW pipe, It is made by winding low-carbon structural steel or low-alloy structural steel strip into a blank at a certain spiral angle (called forming angle), and then welding it together. It can be used in a narrower way. Strip steel produces large-diameter steel pipes. Its specifications are expressed in terms of outer diameter and wall thickness. Welded pipes should ensure that the water pressure test, tensile strength of the weld and cold bending performance meet the regulations.