Difference between seamless pipe and seam pipe
From the technological point of view, the seamless steel pipes is formed by rolling once, heated with round steel, pierced, hot rolled, sizing, and straightened.
Seam steel pipes are also called welded pipes. They are welded by bending deformation of steel plates or steel strips. There are straight seam welded pipes and spiral welded pipes (spiral welded pipes are generally of large diameter)
What is seamless pipe?
Seamless steel pipes are made of a whole round steel perforated. Steel pipes with no welds on the surface are called seamless steel pipes. According to the production method, seamless steel pipes can be divided into hot-rolled seamless steel pipes, cold-rolled seamless steel pipes, cold-drawn seamless steel pipes, extruded seamless steel pipes, jacked pipes, etc.
According to the cross-sectional shape, seamless steel pipes are divided into two types: round and special-shaped. Special-shaped pipes have various complex shapes such as square, oval, triangle, hexagon, melon-shaped, star-shaped, and finned pipes. The maximum diameter is 900mm and the minimum diameter is 4mm. According to different uses, there are thick-walled seamless steel pipes and thin-walled seamless steel pipes. Seamless steel pipes are mainly used as petroleum geological drilling pipes, cracking pipes for petrochemical industry, boiler pipes, bearing pipes, and high-precision structural steel pipes for automobiles, tractors, and aviation.
①The main production processes of hot-rolled seamless steel pipes (main inspection processes):
Preparation and inspection of tube blank → heating of tube blank → perforation → pipe rolling → steel pipe reheating → diameter determination (reduction) → heat treatment → finished pipe straightening → finishing → inspection (non-destructive, physical and chemical, Taiwan inspection) → warehousing
②The main production processes of cold-rolled (drawn) seamless steel pipes:
Blank preparation→pickling and lubrication→cold rolling (drawing)→heat treatment→straightening→finishing→inspection
The production process of general seamless steel pipes can be divided into two types: cold drawing and hot rolling. The production process of cold-rolled seamless steel pipes is generally more complicated than hot rolling. The tube blanks must first be subjected to three-roll continuous rolling, and then extruded. After the sizing test, if there is no response crack on the surface, the round pipe will be cut by a cutting machine and cut into a blank of about one meter in length. Then enter the annealing process. Annealing requires pickling with acidic liquid. When pickling, pay attention to whether there is a large amount of bubbling on the surface. If there is a large amount of bubbling, it means that the quality of the steel pipe cannot meet the corresponding standards. In appearance, cold-rolled seamless steel pipes are shorter than hot-rolled seamless steel pipes. The wall thickness of cold-rolled seamless steel pipes is generally smaller than hot-rolled seamless steel pipes, but the surface looks brighter than thick-walled seamless steel pipes, and the surface is not too thick. It's quite rough, and there aren't many burrs in the diameter.
The delivery state of hot-rolled seamless steel pipes is generally in a hot-rolled state after heat treatment. After passing the quality inspection, the hot-rolled seamless steel pipe must undergo strict manual selection by the staff. After the quality inspection, the surface must be oiled, followed by multiple cold-drawing experiments. After the hot-rolling treatment, a perforation experiment must be performed. , if the diameter of the perforation is too large, it needs to be straightened and corrected. After straightening, it is transferred by the transmission device to the flaw detection machine for flaw detection experiments. Finally, it is labeled, arranged in specifications, and placed in the warehouse.
Round tube blank → heating → piercing → three-roll cross rolling, continuous rolling or extrusion → tube removal → sizing (or diameter reduction) → cooling → straightening → hydraulic test (or flaw detection) → marking → warehousing seamless steel pipe It is made of steel ingots or solid tube blanks through perforation and then hot-rolled, cold-rolled or cold-drawn.
The specifications of seamless steel pipes are expressed in terms of outer diameter * wall thickness in millimeters.
The outer diameter of hot-rolled seamless steel pipes is generally greater than 32mm and the wall thickness is 2.5-200mm. The outer diameter of cold-rolled seamless steel pipes can be up to 6mm and the wall thickness can be up to 0.25mm. The outer diameter of thin-walled pipes can be up to 5mm and the wall thickness is less than 0.25mm. Rolling has higher dimensional accuracy than hot rolling.
General seamless steel pipes are made of hot-rolled or cold-rolled high-quality carbon structural steels such as 10, 20, 30, 35, 45, 16Mn, 5MnV and other low-alloy structural steels, or 40Cr, 30CrMnSi, 45Mn2, 40MnB and other composite steels. Seamless pipes made of 10 and 20 grade low carbon steel are mainly used for fluid transportation pipelines. Seamless tubes made of medium carbon steel such as 45 and 40Cr are used to manufacture mechanical parts, such as stressed parts of automobiles and tractors. Generally, seamless steel pipes must ensure strength and flattening tests. Hot-rolled steel pipes are delivered in a hot-rolled or heat-treated state; cold-rolled steel pipes are delivered in a heat-treated state.
Hot rolling, as the name suggests, has high temperature, so the deformation resistance is small and large deformation can be achieved. Take the rolling of steel plates as an example. Generally, the thickness of continuous casting billet is about 230mm, and after rough rolling and finish rolling, the final thickness is 1~20mm. At the same time, due to the small width-to-thickness ratio of the steel plate, the dimensional accuracy requirements are relatively low, and plate shape problems are not prone to occur. The main focus is to control the crown. For those with structural requirements, it is generally achieved through controlled rolling and cooling, that is, controlling the opening rolling temperature and final rolling temperature of finishing rolling. Round tube blank → heating → perforation → heading → annealing → pickling → oiling (copper plating) → Multi-pass cold drawing (cold rolling) → billet tube → heat treatment → straightening → hydraulic test (flaw detection) → marking → storage.
What is seam pipe？
Seam pipe, also known as welded steel pipe, is made of carbon steel that is easy to weld. In terms of nominal size, its commonly used nominal sizes are DN15~100, and its largest nominal diameter is DN150. Welded steel pipes are also called water and gas pipes because they are often used to transport hot and cold water and gas. Galvanized welded steel pipes are customarily called white iron pipes at construction sites, while non-galvanized welded steel pipes are called black iron pipes. The blank used for welded steel pipes is steel plate or strip.
When the T-shaped welded steel pipe contains Ni, it has strong corrosion resistance in an acidic environment. In an environment containing sulfuric acid or hydrochloric acid, the higher the Ni content in the T-shaped welded steel pipe, the stronger the corrosion resistance. Under normal circumstances, corrosion can be prevented by simply adding Cr to the T-shaped welded steel pipe. Poor edge condition of the steel strip is another important reason for misalignment. The effects of changes in mass flow rate, heat flux density and structural parameters (ratio of spiral curvature diameter and T-shaped welded steel pipe diameter Dc/D) on the heat transfer coefficient of saturated bubble boiling in vertical spiral tubes. During the production of T-shaped welded steel pipes, misalignment of edges often occurs, and there are many influencing factors. In production practice, steel pipes are often degraded due to wrong edges and excessive tolerances. Therefore, it is necessary to analyze the causes of misalignment of spiral steel pipes and their preventive measures.
Classification of seamless steel pipes
Stainless Seamless Steel Pipe: Stainless steel seamless steel pipe is a long steel product with a hollow section and no seams around it. It is a steel pipe that is resistant to corrosion by weakly corrosive media such as air, steam, and water, and chemically corrosive media such as acids, alkali, and salts. Also known as stainless acid-resistant steel pipe.
Seamless Carbon Steel Pipe: Seamless carbon steel pipe is made by perforating steel ingots or solid tube blanks into capillary tubes, and then hot rolling, cold rolling or cold drawing. Seamless carbon steel pipes play an important role in my country's steel pipe industry.
Seamless Boiler Tube: Boiler seamless tube is a type of boiler tube and belongs to the seamless steel tube category. The manufacturing method is the same as that of seamless pipes, but there are strict requirements for the type of steel used in manufacturing steel pipes.
Seamless Galvanized Pipe: Galvanized seamless pipes are divided into cold-plated seamless pipes and hot-plated seamless pipes. The former has been banned, and the latter has been advocated by the country to be temporarily available.
Seamless Heat Exchanger Tube: Seamless Heat Exchanger Tube is one of the components of the heat exchanger. It is placed inside the cylinder and is used for heat exchange between two media. Has high thermal conductivity and good isothermal properties. It is a device that can quickly transfer heat energy from one point to another with almost no heat loss, so it is called a heat transfer superconductor, and its thermal conductivity is thousands of times that of copper.
Seamless Precision Tube: Cold drawn precision seamless steel tube is a high-precision steel tube material. The main categories are: precision seamless steel pipe, precision hydraulic seamless steel pipe, cold drawn precision seamless steel pipe, cold rolled precision seamless steel pipe, high precision seamless steel pipe, precision bright seamless steel pipe.
Seamless Hydraulic Tube: Seamless hydraulic tubing is designed to carry fluids between hydraulic components, fittings, valves, flanges and other tools. It is made of material E355 (ST 52.4) or E235 (ST 37.4). These two grades have different chemical compositions. This helps manage work stress.
Classification of Seam pipe
ERW pipe: "ERW steel pipe" is a straight seam resistance welded pipe, abbreviated as ERW. It is used to transport vapor and liquid objects such as oil and natural gas. It can meet various requirements of high and low pressure and plays a decisive role in the field of transportation pipes in the world. .
LSAW Steel Pipe: LSAW steel pipe (Longitudinally Submerged Arc Welding, abbreviated as LSAW) is a professional term for straight seam submerged arc welded steel pipe. It uses a single medium-thick plate as raw material, and presses (rolls) the steel plate into a tube blank in a mold or forming machine. , pipes produced by double-sided submerged arc welding and diameter expansion.
SSAW Steel Pipe: SSAW spiral submerged arc welded pipe, pipe manufacturing standards comply with <> GB9711.1. SSAW Steel Pipe welding method Submerged arc welding (including submerged arc surfacing and electroslag surfacing, etc.) is an important welding method. It has the inherent advantages of stable welding quality, high welding productivity, no arc light and little smoke. Making it the main welding method in the production of important steel structures such as pressure vessels, pipe sections, and box beams and columns. In recent years, although many efficient and high-quality new welding methods have emerged, the application fields of submerged arc welding have not been affected in any way. From the perspective of the weight share of deposited metal by various fusion welding methods, submerged arc welding accounts for about 10% and has not changed much over the years.
Seam steel pipes and seamless steel pipes are classified according to the method of steel pipe production.
1. According to the cross-sectional shape, seamless steel pipes are divided into two types: round and special-shaped. Special-shaped pipes have various complex shapes such as square, oval, triangle, hexagon, melon-shaped, star-shaped, and finned pipes. The maximum diameter is 900mm and the minimum diameter is 4mm. According to different uses, there are thick-walled seamless steel pipes and thin-walled seamless steel pipes. Seamless steel pipes are mainly used as petroleum geological drilling pipes, cracking pipes for petrochemical industry, boiler pipes, bearing pipes, and high-precision structural steel pipes for automobiles, tractors, and aviation.
2. Welded steel pipes (Seam steel pipe) are divided into furnace welded pipes, electric resistance welded pipes and automatic arc welded pipes due to their different welding processes. Due to their different welding methods, they are divided into two types: straight seam welded pipes and spiral welded pipes. The end shape is divided into round welded pipe and special-shaped (square, flat, etc.) welded pipe. Welded steel pipes are welded by butt seams or spiral seams of steel plates rolled into a tube shape. In terms of manufacturing methods, they are divided into welded steel pipes for low-pressure fluid transportation, spiral seam electric welded steel pipes, direct coil welded steel pipes, and electric welded pipes. Seamless steel pipes can be used for liquid pressure pipes and gas pipes in various industries. Welded pipelines can be used for water pipelines, gas pipelines, heating pipelines, electrical pipelines, etc.
(1) seam pipe
The billet used for welded steel pipe is steel plate or strip steel, which is divided into furnace welding pipe, electric welding (resistance welding) pipe and automatic arc welding pipe due to different welding processes. Because of the different forms of welding into straight seam welded pipe and spiral welded pipe two. Because of its end shape is divided into circular welded pipe and special (square, flat, etc.) welded pipe. Welded pipes are divided into the following varieties because of their different materials and uses:
✤ GB/T3091-1993 (galvanized welded steel pipe for low pressure fluid delivery). Mainly used for conveying water, gas, air, oil and heating hot water or steam and other general lower pressure fluid and other purposes of pipe. Its representative material Q235A steel.
✤GB/T3092-1993 (galvanized welded steel pipe for low pressure fluid delivery). It is mainly used for conveying water, gas, air, oil and heating water or steam and other low pressure fluids and other purposes. Its representative material is: Q235A steel.
✤GB/T14291-1992 (Welded steel pipes for fluid transport in mines). It is mainly used for straight seam welding steel pipe for mine air pressure, drainage and shaft gas discharge. Its representative material Q235A, B - grade steel.
✤GB /T14980-1994 (large diameter welded steel pipe for low pressure fluid delivery) Mainly used for conveying water, sewage, gas, air, heating steam and other low pressure fluid and other uses. Its representative material Q235A steel.
✤GB/T12770-1991 (Stainless steel welded steel pipes for mechanical structures). Mainly used in machinery, automobile, bicycle, furniture, hotel and restaurant decoration and other mechanical parts and structural parts. Its representative material 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb, etc.
✤GB/T12771-1991 (Welded stainless steel pipes for fluid transport). Mainly used for conveying low pressure corrosive media. The representative materials are 0Cr13, 0Cr19Ni9, 00Cr19Ni11, 00Cr17, 0Cr18Ni11Nb, 0017Cr17Ni14Mo2, etc.
(2) seamless steel pipe
Because of its different manufacturing technology, it is divided into hot rolled (extruded) seamless steel pipe and cold drawn (rolled) seamless steel pipe. Cold drawn (rolled) pipe is divided into two types: round pipe and special-shaped pipe.
a. Hot rolling (extruded seamless steel pipe) : round tube billet → heating → perforation → three-roll diagonal rolling, continuous rolling or extrusion → pipe stripping → sizing (or reducing) → cooling → billet → straightening → hydrostatic test (or flaw detection) → marking → storage.
Cold drawing (rolled) seamless steel tube: round tube blank → heating → perforation → heading → annealing → pickling → oiling (copper plating) → multi-pass cold drawing (cold rolling) → blank tube → heat treatment → straightening → hydrostatic test (flaw detection) → marking → storage.
b. Seamless steel tubes are divided into the following varieties because of their different uses:
✤GB/T8162-1999 (seamless steel tubes for structure). Mainly used in general structure and mechanical structure. Its representative material (brand number) : carbon steel 20, 45 steel; Alloy steel Q345, 20Cr, 40Cr, 20CrMo, 30-35CrMo, 42CrMo, etc.
✤GB/T8163-1999 (seamless steel pipe for conveying fluid). It is mainly used for conveying fluid pipelines on engineering and large equipment. The representative material (grade) is 20, Q345, etc.
✤Gb3087-1999 (seamless steel tube for low and medium pressure boiler). It is mainly used for conveying low and medium pressure flow in industrial boilers and domestic boilers. The representative material is 10, 20 steel.
✤Gb5310-1995 (seamless steel tubes for high pressure boilers). It is mainly used for high temperature and high pressure conveying fluid collection box and pipeline in power plant and nuclear power plant boiler. The representative material is 20G, 12Cr1MoVG, 15CrMoG, etc.
✤Gb5312-1999 (seamless steel tubes of carbon steel and carbon manganese steel for Marine use). Mainly used for ship boiler and superheater I, II class pressure tube. Representative material for 360, 410, 460 steel class.
✤Gb1479-2000 (seamless steel pipe for high pressure fertilizer equipment). It is mainly used for conveying high temperature and high pressure fluid pipe on chemical fertilizer equipment. The representative material is 20, 16Mn, 12CrMo, 12Cr2Mo, etc.
✤Gb9948-1988 (seamless steel pipe for petroleum cracking). It is mainly used in boilers, heat exchangers and fluid pipelines of petroleum smelters. Its representative material is 20, 12CrMo, 1Cr5Mo, 1Cr19Ni11Nb and so on.
✤Gb18248-2000 (seamless steel pipe for gas cylinders). Mainly used for making various gas and hydraulic cylinders. Its representative material is 37Mn, 34Mn2V, 35CrMo, etc.
✤GB/T17396-1998 (Hot rolled seamless steel tubes for hydraulic supports). Mainly used for making coal mine hydraulic support and cylinder, column, and other hydraulic cylinder, column. Its representative material is 20, 45, 27SiMn and so on.
✤Gb3093-1986 (high pressure seamless steel pipe for diesel engine). Mainly used for diesel injection system high pressure tubing. Its steel pipe is generally cold drawn, and its representative material is 20A. GB/T3639-1983 (cold drawn or cold rolled precision seamless steel pipe) Mainly used for mechanical structure, carbon pressing equipment, to obtain high dimensional accuracy, good surface finish steel pipe. Its representative material 20, 45 steel, etc.
✤GB/T3094-1986 (cold-drawn seamless steel tube, special-shaped steel tube). It is mainly used to make various structural parts and parts, and its material is high quality carbon structural steel and low alloy structural steel.
✤GB/T8713-1988 (Precision inner diameter seamless steel tubes for hydraulic and pneumatic tubes) Cold drawn or cold rolled seamless steel tubes with precise inner diameter for hydraulic and pneumatic cylinders. Its representative material is 20, 45 steel, etc.
✤Gb13296-1991 (stainless steel seamless steel tubes for boilers and heat exchangers). It is mainly used in boilers, superheaters, heat exchangers, condensers and catalytic tubes of chemical enterprises. High temperature, high pressure and corrosion resistant steel pipe. Its representative material is 0Cr18Ni9, 1Cr18Ni9Ti, 0Cr18Ni12Mo2Ti and so on.
✤GB/T14975-1994 (stainless steel seamless steel pipe for structure). Mainly USED FOR general structure (hotel, restaurant decoration) and chemical enterprise mechanical structure with air resistance, acid corrosion and a certain strength of steel pipe. Its representative material for 0-3CR13, 0Cr18Ni9, 1Cr18Ni9Ti, 0Cr18Ni12Mo2Ti.
✤GB/T14976-1994 (seamless stainless steel pipe for fluid transport). Mainly used for conveying corrosive media pipelines. Generation table material for 0Cr13, 0Cr18Ni9, 1Cr18Ni9Ti, 0Cr17Ni12Mo2, 0Cr18Ni12Mo2Ti. YB/T5035-1993 (seamless steel pipe for automobile half bushing). It is mainly used for the production of high quality carbon structural steel and alloy structural steel hot rolled seamless steel tubes for automobile half bushing and drive axle housing shaft pipe. Its representative materials are 45, 45Mn2, 40Cr, 20CrNi3A and so on.
✤API SPEC5CT-1999 (Casing and Tubing Specification), is produced and published by the American Petroleum Institute ("API") for use worldwide. Among them: casing: from the ground surface into the drilling hole, as the lining of the pipe, the pipe through the collar connection. The main materials are J55, N80, P110 and other steel classes, and hydrogen sulfide corrosion resistant C90, T95 and other steel classes. Its low steel grade (J55, N80) can be welded steel pipe.
✤Tubing: a pipe inserted from the ground surface into the casing until the oil layer, and the pipes are connected by a collar or integral connection. The role of the oil pumping unit will be the oil layer through the pipeline to the surface. The main material for J55, N80, P110, and hydrogen sulfide corrosion resistant C90, T95 steel grade. Its low steel grade (J55, N80) can be welded steel pipe.
✤API SPEC 5L-2000 (Pipeline Specification), prepared and published by the American Petroleum Institute, is used worldwide.
✤Pipeline pipe: is the shaft out of the ground oil, gas or water, through the pipeline delivery to the oil and gas industry enterprises. The pipeline pipe includes two kinds of seamless and welded pipe, the pipe end has a flat end, a threaded end and a socket end; The connection mode is end welding, collar connection, socket connection and so on. The main material of the pipe is B, X42, X56, X65, X70 and other steel grades.
The difference between seamless steel pipe and seam steel pipe:
1. Different materials
① Welded steel pipe: Welded steel pipe refers to steel pipes with seams on the surface after bending and deforming steel strips or steel plates into round or square shapes. The blanks used for welded steel pipes are steel plates or strip steels.
②Seamless steel pipe: a steel pipe made from a single piece of metal with no seams on the surface.
2. Different categories
① Welded steel pipe: According to different welding methods, it can be divided into arc welded pipe, high frequency or low frequency resistance welded pipe, gas welded pipe, furnace welded pipe, Bondi pipe, etc. According to the purpose, it is divided into general welded pipe, galvanized welded pipe, oxygen-blowing welded pipe, wire casing, metric welded pipe, roller pipe, deep well pump pipe, automobile pipe, transformer pipe, electric welded thin-walled pipe, electric welded special-shaped pipe and spiral welded pipe.
②Seamless steel pipes: seamless pipes are divided into hot-rolled pipes, cold-rolled pipes, cold-drawn pipes, extruded pipes, and top pipes. According to the cross-sectional shape, seamless steel pipes are divided into two types: round and special-shaped. Special-shaped pipes have square, elliptical, triangular, hexagonal, melon-shaped, star-shaped, and finned pipes. The maximum diameter is 650mm, and the minimum diameter is 0.3mm. According to different purposes, there are thick-walled pipes and thin-walled pipes.
3. Different uses
① Welded steel pipes: can be used as water gas pipes, etc., large diameter longitudinally welded pipes are used for high pressure oil and gas transportation, etc.; spiral welded pipes are used for oil and gas transportation, pipe piles, bridge piers, etc.
②Seamless steel pipes: used as petroleum geological drilling pipes, cracking pipes for petrochemical industry, boiler pipes, bearing pipes, and high-precision structural steel pipes for automobiles, tractors, and aviation.
①seamless steel pipe are mainly used as pipelines or structural parts for fluid transportation, mainly in the machinery industry, while seam steel pipes are mainly used in the construction industry, such as water, gas, compressed air and other low-pressure fluids. However, seamless steel pipes are used for all pressure pipelines. The price of seamless steel pipes is higher than that of seam steel pipes.②Seam pipes generally can withstand the maximum operating pressure of less than 20 kg, which is a safe range of use. It is generally used for low-pressure fluids such as water, gas, and compressed air.
Seamless steel pipe can withstand ultra-high pressure, of course, its wall thickness will increase accordingly, which needs to be designed according to pressure requirements. It is generally used for high-temperature and high-pressure equipment such as high-pressure oil pipes and boiler tubes. There are also seamless steel pipes for structural use, depending on the design requirements.At present, there are also some seamless pipes with seam steel pipes, which are annealed to the weld seam, and the residual stress of the weld seam is made to make the weld seam equivalent to the base metal, and its pressure-bearing range is basically equivalent to that of seamless steel tube. Can also be considered for use.
Of course, there are also some seamless steel pipes on the market that use seam steel pipes to be heated as a whole and then drawn or rolled with a core head. They are mainly small in size. This type of pipe is seamless steel pipe only in terms of appearance, and its quality is not very good.
Advantages Of Seam Steel Pipes Compared To Seamless Steel Pipes :
(1) The seam steel pipe mainly refers to the welded steel pipe, and because of its low cost and high production efficiency, the seamless steel pipe is replaced in many fields. Although welded steel pipes replace seamless steel pipes, they still have essential differences.
(2) The seamless steel pipe is formed by perforating a steel ingot or a solid tube blank, and then hot rolled, cold rolled or cold drawn. The welded steel pipe is a steel pipe which is welded and formed by a steel strip or a steel plate to be deformed into a circular shape or a square shape, and has a joint on the surface. The blank used for welded steel pipes is steel plate or strip steel. From the above definition, the biggest difference between the seamless steel pipe and the welded steel pipe is that the welded steel pipe has seams.
(3) The production process of seamless steel tubes can be divided into cold drawing and hot rolling. The production process of cold rolled seamless steel tubes is generally more complicated than hot rolling. The tube blanks must first be rolled in three rolls, and the sizing should be carried out after extrusion. Test, if the surface does not respond to the crack, the tube is cut by a cutter and cut into a blank of about one meter in length. Then enter the annealing process, the acidification should be acid-washed with acid liquid. When pickling, pay attention to whether there is a large amount of foaming on the surface. If there is a large amount of foaming, the quality of the steel pipe will not reach the corresponding standard.
(4) The appearance of cold-rolled seamless steel pipe is shorter than that of hot-rolled seamless steel pipe. The wall thickness of cold-rolled seamless steel pipe is generally smaller than that of hot-rolled seamless steel pipe, but the surface looks brighter than thick-walled seamless steel pipe, and the surface is not too More rough, not too many burrs in the caliber.
The following are the advantages of welded tubes compared to seamless steel tubes or other seam steel tubes:
(1) The electric welded steel pipe has a large size range, and can produce welded pipes with an outer diameter of 45 to 4000 mm and a wall thickness of 0.1 to 40 mm and a pipe length of up to several hundred meters. The wall thickness is smaller than that of the seamless steel pipe and smaller than the furnace pipe. The pipe diameter to the pipe wall thickness ratio can reach 100, and the seamless steel pipe also has a large-diameter seamless steel pipe and a small-diameter seamless steel pipe, and the furnace welded pipe is also small. The pipe diameter and wall thickness are 4~50 and 5~28 respectively. Therefore, the electric welded pipe can save metal.
(2) It can produce steel pipes of various chemical compositions.
(3) The emergence of new electric welding units, equipment and control systems continue to improve, so that the weld has a higher strength than the metal matrix. The use of heat treatment eliminates the welding stress of the weld and allows the welded pipe to obtain a uniform structure in cross section. Therefore, the quality of the welded pipe is not lower than that of the seamless steel pipe, and sometimes it can replace the seamless steel pipe.
(4)Since the steel tube is formed in a cold state, the obtained steel pipe has high dimensional accuracy and surface roughness, and the general metal consumption is only 1.03% to 1.05%.
(5)The electric welding steel pipe unit can stop the power supply and reduce the energy consumption.
(6)The production process is easy to automate and continuous, with high productivity and good working conditions.