LSAW Welded Steel Pipe: Features and Manufacturing Processes

What is LSAW pipe means
LSAW (Longitudinal double submerge arc welding) carbon steel pipe is a type of SAW pipe made of steel plates that were hot rolled by JCOE or UOE forming technology. JCOE technology represents the shaping and forming processes involved during manufacturing as well as the inner and outer welding and cold expansion carried out after welding.


When compared to UOE LSAW steel pipes, LSAW pipe manufacturers in China can produce more sizes as thus: OD 406 mm – mm, thickness 6.35 mm – 60 mm, pipe length 2 m – 18 m with the LSAW pipe having superiority.


Octal offers LSAW steel pipe with high quality and competitive prices.


LSAW steel pipe features
Features:


-Large diameter steel pipes
-Thick walls
-High-Pressure resistance
-Low-temperature resistance


Tests:


-Chemical Component Analysis
-Mechanical Properties – Elongation, Yield Strength, Ultimate Tensile Strength
-Technical Properties – DWT Test, Impact Test, Blow Test, Flattening Test
-X-ray Test
-Exterior Size Inspection
-Hydrostatic Test
-UT Test


How to use LSAW welded steel pipe for pipelines
The basic metal and welding metal have been tested according to the specification of the pipe API SPEC 5L, DIN, EN, ASTM, GOST standard and other standards.


Also, LSAW pipe can be welded with flanges, lifting eyes and other parts depending on clients’ requirements.


LSAW pipe are used for conveying fluids like oil, gas and water transportation as well as used for seashore projects and ground constructions. These products are manufactured in China and are exported to other countries like United States of America, Canada, India, Pakistan, Africa, etc.


LSAW steel pipe manufacturing process
The LSAW large diameter steel pipe manufacturing process is explained in the steps below:


1. Plate Probe: This is used for manufacturing the large diameter LSAW joints right after it enters the production line which is the initial full-board ultrasonic testing.
2. Milling: The machine used for milling does this operation through two-edged milling plate to meet the requirements of the plate width and the sides parallel to the shape and degree.
3. Pre-curved side: This side is achieved by using a pre-bending machine on the pre-bending plate edge. The plate edge needs to meet curvature requirement.
4. Forming: After the pre-bending step, in the first half of the JCO molding machine, after stamped steel, it is pressed into a “J” shape while the on the other half of the same steel plate it is bent and pressed into a “C” shape, then the final opening forms an “O” shape.
5. Pre-welding: This is to make a welded pipe steel a straight seam after it has been formed and then use gas welding seam (MAG) for continuous welding.
6. Inside weld: This is done with a tandem multi-wire submerged arc welding (about four wire) on the inner part of the straight seam welded steel pipe.
7. Outside Weld: Outside weld is the tandem multi-wire submerged arc welding on the outer part of the LSAW steel pipe welding.
8. Ultrasonic Testing: Outside and inside of the straight seam welded steel pipe and both sides of the base material are welded with 100% inspection.
9. X-ray inspection: X-ray industrial TV inspection is carried out on the inside and outside using image processing system to make sure there is detection sensitivity.
10. Expansion: This is for accomplishing submerged arc welding and straight seam steel pipe length hole diameter so as to improve the steel tube’s size precision and improve the distribution of stress in the steel tube.
11. Hydraulic test: This is carried out on the hydraulic test machine for steel after expanding by-root test for ensuring the steel pipe meets the standard requirements with the machine having an automatic recording and storage capabilities.
12. Chamfering: This involves the inspection carried out on the steel pipe at the end of the whole process.

Welded steel pipe, also known as welded pipe, is a steel pipe made of steel plate or strip steel after crimping and welding. 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 that of seamless steel pipes. Welded steel pipes are divided into straight seam welded pipes and spiral welded pipes according to the form of the weld.

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The blanks used for welded steel pipes are steel plates or strips, which are divided into furnace welded pipes, electric welded (resistance welded) pipes and automatic arc welded pipes due to their different welding processes. Due to the 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 circular 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/T- (galvanized welded steel pipe for low pressure fluid transportation). Mainly used for conveying general lower pressure fluids such as water, gas, air, oil and heating hot water or steam and other purpose pipes. Its representative material is: Q235A grade steel.

GB/T- (Welded steel pipe for mining fluid transportation). It is mainly used for straight seam welded steel pipes for mine air pressure, drainage and shaft discharge gas. It represents the material Q235A, B grade steel. GB/T- (large diameter electric welded steel pipe for low pressure fluid transportation). Mainly used for conveying low pressure fluids such as water, sewage, gas, air, heating steam and other purposes. It represents the material Q235A grade steel.

GB/T- (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/T- (stainless steel welded steel pipe for fluid transportation). Mainly used for conveying low pressure corrosive medium. The representative materials are 0Cr13, 0Cr19Ni9, 00Cr19Ni11, 00Cr17, 0Cr18Ni11Nb, Cr17Ni14Mo2, etc.

In addition, welded stainless steel pipes for decoration (GB/T -), stainless steel welded pipes for architectural decoration (JG/T -), large-diameter electric-welded steel pipes for low-pressure fluid transportation (GB/T -), and Welded steel pipes for heat exchangers (YB-).

The production process of the straight seam welded pipe is simple, the production efficiency is high, the cost is low, and the development is fast. The strength of the spiral welded pipe is generally higher than that of the straight seam welded pipe. However, compared with the same length of straight seam pipe, the length of the weld is increased by 30~100%, and the production speed is lower.

Therefore, most of the welded pipes with smaller diameters use straight seam welding, and most of the welded pipes with large diameters use spiral welding.

Supplement: The welded pipe is welded with strip steel, so its status is not as high as that of the seamless pipe.

Additional types of welded pipes:

1. Ordinary carbon steel wire casing (GB-88) is a steel pipe used to protect wires in electrical installation projects such as industrial and civil buildings, installation of machinery and equipment.

2. Straight seam electric welded steel pipe (YB242-63) is a steel pipe with the weld seam 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 for pressurized fluid transportation (SY-83) is made of hot-rolled steel coil as a tube blank, spirally formed at constant temperature, and welded by double-sided submerged arc welding. It is used for pressurized 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 diameter of the steel pipe is large, the transportation efficiency is high, and the investment in laying pipelines can be saved. Mainly used for pipelines for transporting oil and natural gas.

4. Spiral seam high-frequency welded steel pipe for pressurized fluid transportation (SY-83) is made of hot-rolled steel coil as a tube blank, which is spirally formed at constant temperature and welded by high-frequency lap welding method for pressurized fluid transportation. 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 transportation efficiency, and can save investment in laying pipelines. Mainly used for laying pipelines for transporting oil, natural gas, etc.

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5. Spiral seam submerged arc welded steel pipe (SY-83) for general low-pressure fluid transportation is made of hot-rolled steel coil as the tube blank, which is often spirally formed at high temperature, and is made by double-sided automatic submerged arc welding or single-sided welding. 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 (SY-83) for general low-pressure fluid conveying is made of hot-rolled steel coil as a tube blank, which is spirally formed at constant temperature, and is welded by high-frequency lap welding for general low-pressure fluid conveying. Seam high frequency welded steel pipe.

7. Spiral-welded steel pipe for piles (SY-83) is made of hot-rolled steel coils as tube blanks, which are often spirally formed at high temperature, and are made by double-sided submerged arc welding or high-frequency welding. They are used for civil construction structures, docks, bridges Equal foundation pile

By use

It is further divided into general welded pipe, galvanized welded pipe, oxygen blown welded pipe, wire casing, metric welded pipe, idler pipe, deep well pump pipe, automobile pipe, transformer pipe, electric welding thin-walled pipe, electric welding special-shaped pipe and spiral welded pipe.

General welded pipe: General welded pipe is used to transport low pressure fluid. Made of Q195A, Q215A, Q235A steel. Also available in other mild steels that are easy to weld. The steel pipe needs to be tested for water pressure, bending, flattening, etc., and has certain requirements on the surface quality. Usually, the delivery length is 4-10m, and it is often required to deliver to a fixed length (or multiple feet). The specification of the welded pipe is expressed by the nominal diameter (mm or inch). The nominal diameter is different from the actual one. The welded pipe can be divided into two types: ordinary steel pipe and thickened steel pipe according to the specified wall thickness.

Galvanized steel pipes: In order to improve the corrosion resistance of steel pipes, general steel pipes (black pipes) are galvanized. Galvanized steel pipe is divided into two types: hot-dip galvanized and electric steel zinc. The hot-dip galvanized galvanized layer is thick and the cost of electro-galvanized is low.

Oxygen blowing welded pipe: It is used as oxygen blowing pipe for steel making, generally small-diameter welded steel pipe, with eight specifications ranging from 3/8 inch to 2 inch. Made with 08, 10, 15, 20 or Q195-Q235 steel strip. In order to prevent corrosion, some are aluminized.

Wire casing: It is also an ordinary carbon steel electric welded steel pipe, which is used in concrete and various structural power distribution projects. The commonly used nominal diameter is 13-76mm. The wall of the wire sleeve is relatively thin, and most of them are used after coating or galvanizing, and a cold bending test is required.

Metric welded pipe: The specification is in the form of a seamless pipe, and the welded pipe is expressed in millimeters of outer diameter * wall thickness. It is welded with the hot and cold strips of ordinary carbon steel, high-quality carbon steel or general low-alloy steel, or after welding with hot strips. And then made by cold-dial method. Metric welded pipes are divided into general and thin-walled pipes. They are generally used as structural parts, such as drive shafts, or to transport fluids. Thin-walled pipes are used to produce furniture, lamps, etc., to ensure the strength and bending test of the steel pipe.

Roller tube: It is used for electric welded steel pipe of belt conveyor idler, generally made of Q215, Q235A, B steel and 20 steel, with a diameter of 63.5-219.0mm. There are certain requirements for the curvature of the tube, the end face should be perpendicular to the center line, and the 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. The steel pipe is delivered in fixed length or double length, and there are certain requirements for the bending degree of the steel pipe.

Special-shaped pipes: square pipes, rectangular pipes, hat-shaped pipes, and hollow rubber steel doors and windows welded by ordinary carbon structural steel and 16Mn steel strips, mainly used for agricultural machinery components, steel windows and doors, etc.

Electric welding thin-walled tube: mainly used to make furniture, toys, lamps, etc. In recent years, thin-walled tubes made of stainless steel strips have been widely used in high-end furniture, decoration, and fences.

Spiral welded pipe: It is made by rolling low carbon carbon structural steel or low alloy structural steel strip at a certain helix angle (called forming angle) into a tube blank, and then welding the pipe seams. Strip steel produces large diameter pipes. Spiral welded pipes are mainly used for oil and natural gas transmission pipelines, and their specifications are expressed by outer diameter * wall thickness. Spiral welded pipes are single-sided welded and double-sided welded. The welded pipe should ensure that the hydraulic test, the tensile strength of the welded seam and the cold bending performance must meet the regulations.