Welded steel pipes, also called welded pipes, are steel pipes made of steel or strip steel after crimping and forming, and are generally 6 meters in length. Welded steel pipe has simple production process, high production efficiency, many varieties and specifications, and less equipment investment, but the general strength is lower than seamless steel pipe.
Introduction
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 been increasing, 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 welded pipes according to the form of welds. Classification by production method: Process classification-arc welded pipe, resistance welded pipe, (high frequency, low frequency) gas welded pipe, furnace welded pipe.
Smaller diameter welded pipes are welded by straight seam, and large diameter welded pipes are mostly spiral welded. According to the shape of the end of the steel pipe, it is divided into round welded pipe and special-shaped (square, rectangular, etc.) welded pipe; according to different materials and uses, it is divided into mining fluid Conveying welded steel pipes, galvanized welded steel pipes for low pressure fluid conveying, electric welded steel pipes for belt conveyor rollers, etc. According to the size table in the current national standard, the outer diameter * wall thickness is sorted from small to large.
Product Standards
The commonly used materials of welded pipe are: Q235A, Q235C
Q235B, 16Mn, 20#, Q345, L245, L290, X42, X46, X60, X80, 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb, etc.
The blanks used for welded steel pipes are steel plates or strip steels, which are divided into furnace welded pipes, electric welded (resistance welded) pipes and automatic arc welded pipes due to their different welding processes. Because of its different welding forms, it is divided into two types: straight seam welded pipe and spiral welded pipe. Because of its end shape, it is divided into round welded pipe and special-shaped (square, flat, etc.) welded pipe. Welded pipes are divided into the following varieties due to their different materials and uses:
GB/T3091-2008 (Welded steel pipe for low pressure fluid transportation). Mainly used to transport water, gas, air, oil, heating water or steam and other generally lower pressure fluids and other purposes. Its representative material is: Q235A grade steel.
GB/T14291-2006 (Welded steel pipe for mining fluid transportation). Mainly used for straight seam welded steel pipes for mine pressure, drainage and shaft gas discharge. Its representative material is Q235A, Grade B steel.
GB/T12770-2002 (Stainless steel welded steel pipe for mechanical structure). Mainly used in machinery, automobiles, bicycles, furniture, hotel and restaurant decoration and other mechanical parts and structural parts. Its representative materials are 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb, etc.
GB/T12771-1991 (Stainless steel welded steel pipe for fluid transportation). Mainly used to transport low-pressure corrosive media. Representative materials are 0Cr13, 0Cr19Ni9, 00Cr19Ni11, 00Cr17, 0Cr18Ni11Nb, 0017Cr17Ni14Mo2, etc.
In addition, welded stainless steel pipes for decoration (GB/T 18705-2002), stainless steel welded pipes for architectural decoration (JG/T 3030-1995), and welded steel pipes for heat exchangers (YB4103-2000).
Production Process
Longitudinal welded pipe has simple production process, 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 pipe diameters can be produced from narrower welded pipes, and welded pipes with different pipe diameters can also be produced from billets of the same width. 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.
Large diameter or thick welded pipes are generally made directly from steel blanks, while small welded pipes and thin-wall welded pipes only need to be directly welded through steel strips. Then after a simple polishing, drawing is fine
Supplement: The welded pipe is welded with strip steel, so it is not as high as a seamless pipe.
Welded pipe process
Raw material uncoiling-leveling-end shearing and welding-looper-forming-welding-inner and outer bead removal-pre-correction-induction heat treatment-sizing and straightening-eddy current testing- Cut off-water pressure inspection-pickling-final inspection (strict control)-packaging-shipment.
product category
Classified by purpose
It is divided into general welded pipe, galvanized welded pipe, oxygen blown 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, scaffolding pipe and spiral welded pipe .
General welded pipe: General welded pipe is used to transport low pressure fluid. Made of Q195A, Q215A, Q235A steel. It can also be made of other mild steel that is easy to weld. Steel pipes need to be subjected to water pressure, bending, flattening and other experiments, and there are certain requirements for the surface quality. Usually the delivery length is 4-10m, and the fixed-length (or double-length) delivery is often required. The specifications of welded pipes are expressed by the nominal diameter (mm or inches). The nominal diameter of welded pipes is different from the actual ones. According to the specified wall thickness, the welded pipes are divided into two types: ordinary steel pipe and thickened steel pipe.
Galvanized steel pipe: In order to improve the corrosion resistance of the steel pipe, the general steel pipe (black pipe) is galvanized. Galvanized steel pipes are divided into two types: hot-dip galvanizing and electric steel zinc. The hot-dip galvanizing layer is thick and the cost of electro-galvanizing is low.
Oxygen-blowing welded pipe: Used as a steel-making oxygen-blowing pipe, generally small-diameter welded steel pipes with eight specifications ranging from 3/8 inch to 2 inch. Made of 08, 10, 15, 20 or Q195-Q235 steel strip. To prevent corrosion, some are aluminized.
Wire casing: Ordinary carbon steel electric welded steel pipe, used in concrete and various structural power distribution projects, the commonly used nominal diameter is from 13-76mm. The wall of the wire sleeve is thin, and most of them are used after coating or galvanizing, and a cold bending test is required.
Metric welded pipe: The specification is used as a seamless pipe form, and the welded steel pipe expressed by outer diameter * wall thickness mm, using ordinary carbon steel, high-quality carbon steel or general energy low-alloy steel, hot strip, cold strip welding, or hot strip welding Then it is made by cold dialing method. Metric welded pipes are divided into ordinary energy and thin-walled, and are commonly used as structural parts, such as drive shafts or conveying fluids. Thin-walled pipes are used to produce furniture, lamps, etc., and the strength and bending test of the steel pipe must be ensured.
Roller tube: Electric welded steel pipe used for the roller of belt conveyor, generally made of Q215, Q235A, B steel and 20 steel, with a diameter of 63.5-219.0mm. There are certain requirements for tube bending, end face to be perpendicular to the center line, and ovality. Generally, water pressure and flattening tests are carried out.
Transformer tube: It is used to manufacture transformer radiator tubes and other heat exchangers. It is made of ordinary carbon steel and requires flattening, flaring, bending, and hydraulic tests. Steel pipes are delivered in fixed-length or double-length, and there are certain requirements for the bending of the steel pipe.
Special-shaped pipes: square pipes, rectangular pipes, hat-shaped pipes, hollow rubber steel doors and windows welded by ordinary carbon structural steel and 16Mn steel strips, mainly used for agricultural machinery parts, steel windows and doors, etc.
Welded thin-walled pipe: mainly used to make furniture, toys, lamps, etc. In recent years, thin-walled pipes made of stainless steel belts are widely used, such as high-end furniture, decoration, and fences.
Spiral welded pipe: the low carbon carbon structural steel or low alloy structural steel strip is rolled into a tube blank at a certain helix angle (called forming angle), and then the tube seam is welded together. It can be made with a narrower Strip steel produces large diameter steel pipes. Spiral welded pipes are mainly used for oil and natural gas pipelines, and their specifications are expressed by outer diameter * wall thickness. Spiral welded pipes can be welded on one side and on both sides. Welded pipes should be guaranteed to meet the requirements for hydraulic test, tensile strength and cold bending performance of the weld.
Classified by production method
(1) According to the process-arc welded pipe, resistance welded pipe (high frequency, low frequency), gas welded pipe, furnace welded pipe
(2) According to the weld seam-straight seam welded pipe, spiral welded pipe
Classified by section shape
(1) Simple section steel pipe-round steel pipe, square steel pipe, oval steel pipe, triangle steel pipe, hexagonal steel pipe, diamond steel pipe, octagonal steel pipe, semi-circular steel round, others
(2) Complicated section steel pipes-unequal hexagonal steel pipes, five-petal plum-shaped steel pipes, double convex steel pipes, double concave steel pipes, melon seeds steel pipes, conical steel pipes, corrugated steel pipes, case steel pipes, etc.
Classification by wall thickness
Thin-walled steel pipe, thick-walled steel pipe
Classified by end shape
Divided into round welded pipe and special-shaped (square, flat, etc.) welded pipe.
Category supplement
1. Ordinary carbon steel wire casing (GB/T3640-88) is a steel pipe used to protect wires in electrical installation projects such as industrial and civil construction and installation of machinery and equipment.
2. Straight seam electric welded steel pipe (YB242-63) is a steel pipe whose weld seam is parallel to the longitudinal direction of the steel pipe. Usually divided into metric electric welded steel pipe, electric welded thin-walled pipe, transformer cooling oil pipe and so on.
3. Spiral seam submerged arc welded steel pipe (SY5036-83) for pressure-bearing fluid transportation is made of hot-rolled steel strip coils, which are spirally formed at regular temperatures and welded by double-sided submerged arc welding for pressure-bearing fluid transportation. Spiral seam steel pipe. The steel pipe has strong pressure-bearing capacity and good welding performance. After various strict scientific inspections and tests, it is safe and reliable to use. The steel pipe has a large diameter, high transmission efficiency, and can save investment in laying pipelines. Mainly used in pipelines for transporting oil and natural gas.
4. Spiral seam high-frequency welded steel pipes for pressure-bearing fluid transportation (SY5038-83) are made of hot-rolled steel strip coils, which are spirally formed at regular temperatures and welded by high-frequency lap welding, for pressure-bearing fluid transportation The spiral seam high frequency welded steel pipe. The steel pipe has strong pressure-bearing capacity and good plasticity, which is convenient for welding and processing. After various strict and scientific inspections and tests, it is safe and reliable to use. The steel pipe has a large diameter and high transmission efficiency. It can save investment in laying pipelines. Mainly used to lay pipelines for transporting oil and natural gas.
5. Spiral seam submerged arc welded steel pipe (SY/T5037-2000) for general low-pressure fluid transportation is made of hot-rolled steel strip coils as tube blanks, which are spirally formed at regular temperatures and made by double-sided automatic submerged arc welding or single-sided welding. It is used for submerged arc welded steel pipes for general low pressure fluid transportation such as water, gas, air and steam.
6. Spiral seam high-frequency welded steel pipe for general low-pressure fluid transportation (SY5039-83) is a hot-rolled steel strip as a tube blank, which is often spirally formed at temperature, and is welded by high-frequency lap welding for general low-pressure fluid transportation. Seam high-frequency welded steel pipe.
7. Spiral welded steel pipe for piles (SY5040-83) is made of hot-rolled steel strip coils as tube blanks, which are often spirally formed by double-sided submerged arc welding or high-frequency welding. They are used in civil construction structures, wharfs, and bridges. Wait for foundation piles.
Features
Longitudinal welded pipe has simple production process, high production efficiency, low cost and rapid development. The strength of spiral 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 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.
Scope of application
Products are widely used in water supply engineering, petrochemical industry, chemical industry, power industry, agricultural irrigation, and urban construction. It is one of the 20 key products developed in my country. For liquid transportation: water supply and drainage. For gas transportation: coal gas, steam, liquefied petroleum gas. For structural purposes: as piling pipes and bridges; pipes for docks, roads, and building structures.