Advantages and Application of LSAW Steel Pipe

Longitudinal Submerged Arc Welded Pipe or simply LSAW steel pipe and Straight Seam Submerged Arc Welded Pipe or simply SSAW steel pipe belong to submerged-arc welding (SAW). But LSAW steel pipe adopts single steel sheet as raw material, its advantages include: the thickness of the steel plate can reach more than 100mm, and there is no crescent bends; since it is straight seam, forming is more convenient, but also it is easy to weld tracking, which is suitable for two-step pre-precision welding production; and there is the whole body of mechanical expansion process, which can basically eliminate the residual stress. All of advantages above make LSAW can be produced big diameter steel pipe (the maximum can reach 1422mm), high-grade pipe (50mm), high steel grade (X80/X100/X120), and large structure tube that used in two, three, four types of regional and marine engineering. LSAW steel pipe and high-frequency Longitudinal Welded Pipe (HFW steel pipe) all belong to Longitudinal Welded Pipe, but the high-frequency welded pipe can be made of medium and small welded pipe (400mm), and there is intermediate frequency heat treatment process. When the diameter, steel grade is the same, high-frequency welded pipe is more superior, for example, foreign pulp pipe often use high-frequency welded pipe (HFW).

API 5L Welded Steel Pipe

API early in 1926 released by the American Petroleum Institute (API) API-5L standard, initially including three steel grade A25, A, B, and later released several times. API 5L welded steel pipe is mainly used for the delivery of the onshore and offshore oil and gas, coal slurry, the slurry media and offshore platforms, power plants, chemical industry and urban construction, structural tubes.

China is currently used in the Petroleum Pipeline tube spiral welded pipe (SSAW steel pipe), LSAW steel pipe, electric resistance welded pipe (ERW steel pipe). Diameter less than 152mm selection of seamless steel tubes. Of the late 1960s to the 1970s, spiral pipe plant rapid development of crude oil pipelines almost all spiral welded steel pipe. The spiral welded steel pipe of the disadvantage is the internal stress is large, the dimensional accuracy is poor, the probability of generation of defects. According to expert analysis, should adopt the policy of "walking on two legs", and actively carry out technological transformation now spiral welded pipe plant, also in promising; vigorously develop straight seam submerged arc control tube industry in China. ERW steel pipe with a smooth appearance, high dimensional accuracy, lower prices, and has been widely used at home and abroad.

Straight seam high frequency welded steel molding process that used in the production of LSAW steel pipe by Prime Steel Pipe is with advanced, reliable quality, welding position, stable welding parameters, welding speed, high yield, and the entire production line equipment and technology are world-class level.

(1) straight seam high frequency welded steel pipe forming process spring back small residual stress.
(2) the strain hardening effect is small, precise geometric dimensions full circle, will help ensure the quality of construction and welding.
(3) straight seam high frequency welded steel bead shape is good, not prone to biting edge, inside and outside the weld misalignment defects.
(4) straight-seam pipe weld distributed in a point on the circumference and, therefore, according to the demand to weld on a favorable position.

Production Technology of SSAW Steel Pipe

SSAW steel pipe (some people call it spiral welded pipe) is also a kind of welded pipe, its strength is generally higher than the LSAW steel pipe. Spiral welded pipe with large diameter can be produced by the narrow blank, and SSAW steel pipe with different diameter can also be produced by the same width of blank. However, compared with the same length of the straight pipe, the weld length increased by 30 to 100%, and the production rate is low. Therefore, the smaller diameter of the pipe mostly use LSAW steel pipe, large diameter welded pipe mostly use spiral welded pipe.

The production process of SSAW steel pipe

SSAW steel pipe is the steel pipe with spiral seam that using the strip coil as raw material, extrusion forming under normal temperature, and using automatic double wire double-sided submerged arc welding process to weld.

1.Raw materials are coil, wire, flux. Those must finish the rigorous physical and chemical testing before putting into.
2.The head and tail of strip steel butt joint, use single or double wire submerged arc welding, and use automatic submerged arc welding to repair welding after rolled into steel pipe.
3.Before forming, the strip will go through the leveling, cutting edge, planing edge, surface cleaning and delivery to the edge of the treatment.
4.Using electrical contact pressure gauge control the pressure of the cylinder on both sides of the conveyor to ensure the smooth delivery of the strip.
5.Use external control or internal control roll forming.
6.Use weld gap control device to ensure that the weld gap to meet the welding requirements, diameter, misalignment and weld gap are strictly controlled.
7.Welding and external welding all use American Lincoln welding machine to single or double wire submerged arc weld, in order to obtain a stable welding specifications.
8.The welding line after welding must go through on-line continuous ultrasonic automatic injury inspection to ensure that 100% of the spiral weld non-destructive testing coverage. If there are defects, automatic alarm and spray marking, production workers adjust the process parameters at any time, eliminate of defects timely.
9.Use air plasma cutting machine to cut a single pipe.
10.After cutting into a single steel pipe, the first three of each batch of steel pipe must be carried out a strict first inspection system, to check the weld mechanical properties, chemical composition, melting conditions, steel pipe surface quality and after nondestructive testing to ensure that the pipe process qualified, so it can be put into formal production.
11.There are parts marked by ontinuous acoustic flaw on the seam, after manual ultrasound and X-ray review, if there are defects, after repair, again after the nondestructive test until the defect has been confirmed to eliminate.
12.The butt welds and helical welds of strip steel where the junction of the Ding-type joints, all through the X-ray TV or film inspection.
13.Each pipe must go through the hydrostatic test, the pressure using radial seal. Test pressure and time by the steel pipe hydraulic microcomputer detection device strictly controlled. Test parameters are automatically printed.
14.Pipe end machining, so that the vertical face, bevel angle and blunt edge to be accurately controlled.

Workshop Design of Large Diameter LSAW Steel Pipe

In 1940 the United States first use UOE method to produce large diameter LSAW steel pipe. In the early 1950s, the United States built a LIOE pipe workshop with a diameter of 607 to 915 mm. 1955 ~ 1967 years of Europe, the United States, Japan UOE welded pipe construction workshop, the diameter of its pipe range of 406 ~ 1067mm, the maximum length of steel pipe is 12m. From 1967 to 1976, the maximum diameter of welded steel pipe was 1626mm, the pipe wall thickness was 40mm, the length of pipe was 18m, and continuous pre-welding and automatic nondestructive testing and automatic control were used in Germany and Japan.

Design scale and product program UOE pipe workshop design scale is generally 40 to 110 million t/a, the main varieties of high-quality carbon steel pipe, steel pipe yield strength of 750MPa, product specifications for the diameter of 406 ~ 1626mm, wall thickness 6. 4 ~ 40mm, length up to 18m.

Process UOE pipe material for the thick and thick steel plate, planing edge of the front of the pre-bending, U-type press it will be pressed into a U-shaped, and then in the 0-type press it into a round tube, after pre-welding , Round tube to send a few welding lines, welding the arc plate on both inside and outside the welding, the formation of steel pipe, and then in the expansion pipe on the pipe expansion pipe diameter, and improve the dimensional accuracy, After passing the inspection, inside and outside the surface coated with anti-corrosion layer.

The selection of process equipment is mainly based on the production scale, product program, construction funds and raw materials, energy and other conditions to choose steel planing machine, pre-curved machine, U-type presses, 0-type presses, pre-welding machine, Pipe machine, non-destructive testing equipment and steel pipe coating equipment inside and outside.

The Application of Large Diameter LSAW Steel Pipe

Large diameter LSAW steel pipe, also known as welded steel pipe, is made of steel plate or steel strip after bending (electric model 0317 and check 6012755 standard) and then is made of by high-frequency welding and submerged arc welding. According to the form of seam welded steel pipe is divided into LSAW steel pipe and spiral welded pipe. According to the use it is divided into general welded pipe, galvanized steel pipe, blowing oxygen pipe, wire casing, metric pipe, roller tube, deep well pump, automotive tube, transformer tube, welded thin-walled tube, welded pipe and spiral welded pipe.

General pipe (manufactured bu Prime Steel Pipe) is used to transport low pressure fluid. Implementation of the standard is GB/T0317 No. 6012889. It is manufactured with Q195A, Q215A, Q235A steel. It can also be made of other mild steel that is easy to weld. Steel pipe must be tested by water pressure, bending, flattening and other experiments, the surface quality has certain requirements, the delivery length usually is 4-10m, and it often requires delivery by length (or double length). The specifications of the welded pipe are denoted by nominal caliber (mm or inch). Nominal caliber is different from the actual one. The welded pipe has two different kinds of steel pipe according to the specified wall thickness, including ordinary steel pipe and thickened steel pipe.

The Use of LSAW Steel Pipe

Materials commonly used by LSAW steel pipe are: Q235A, Q235C, Q235B, 16Mn, 20 #, Q345, L245, L290, X42, X46, X60, X80, 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb and so on.

LSAW steel pipe in the country mainly used in water projects, petrochemical industry, chemical industry, power industry, agricultural irrigation, urban construction. For liquid delivery with: water supply, drainage. For gas transportation with: gas, steam, liquefied petroleum gas. For the structure with: for piling pipe, for the bridge; terminal, road, building structure and so on.

It is divided into general straight seam welded pipe, galvanized pipe, oxygen blowing pipe, wire casing, metric pipe, roller tube, deep well pump tube, automobile pipe, transformer tube, welded thin wall tube, welded pipe and spiral welded pipe.

General LSAW steel pipe: general LSAW steel pipe is usually used to transport low pressure fluid. Manufactured with Q195A, Q215A, Q235A steel. It can also be made of other mild steel that is easy to weld. Steel pipe has to be water pressure, bending, flattening and other experiments, the surface quality has certain requirements, delivery length is usually 4-10m, often requires cuttolength (or double length) delivery. The specifications of the welded pipe are denoted by nominal caliber (mm or inch). Nominal caliber is different from the actual one. The welded pipe has two kinds of ordinary steel pipe and thickened steel pipe according to the stipulated wall thickness. The pipe is divided into two types: pipe end and thread.

Galvanized steel pipe: In order to improve the corrosion resistance of steel pipe, the general steel pipe (black tube) for galvanizing. Galvanized steel pipe is divided into hot galvanized and cold galvanizing, zinc coating of hot galvanized is thickness, the cost of cold galvanizing is low.

Oxygen blowing pipe: Pipe manufacturer generally use small diameter welded steel pipe to produce steel blowing oxygen tube, specifications of it are from 3/8 inch -2 inch eight. Made with 08,10,15,20 or Q195-Q235 steel strip. For the erosion, some of those will do aluminizing treatment.

Wire casing: that is, ordinary carbon steel welded steel pipe, that is used in concrete and various structural distribution works, commonly used nominal diameter is from 13-76mm. The wire jacket wall is thinner, mostly coated or galvanized before use, and it requires a cold bending test.

Metric Welded Pipe: Specially used as a seamless pipe, it is the welded steel pipe that expressed by outer diameter * wall thickness mm, welded by the hot or cold belt of ordinary carbon steel, high quality carbon steel or general energy low alloy steel, cold zone welding. And then made by cold dial method. Metric welded pipe can be used for structural furniture, such as drive shaft, or conveying fluid, thin wall used to produce furniture, lamps, etc., to ensure that the strength of steel and bending test.

Roller tube: for belt conveyor roller welding steel pipe, generally use Q215, Q235A, B steel and 20 steel to manufacture, diameter is 63.5-219.0mm. It certain requirements on the tube bending, the end to the vertical line with the center line, the oval, and generally it must do water pressure and flattening test.

Transformer tube: used in the manufacturing transformer heat pipe and other heat exchangers, use ordinary carbon steel to manufacture, requires crushing, flaring, bending, hydraulic test. Steel pipe to the length or double the delivery, the bending degree of steel pipe have certain requirements.

Shaped LSAW steel pipe: made by ordinary carbon structural steel and 16Mn straight seam welded pipe and other square tube, rectangular tube, cap tube, air plastic steel doors and windows with steel pipe, mainly used for agricultural machinery parts, steel windows and so on.

Welded thin-walled tube: mainly used for the production of furniture, toys, lamps and so on.

Brief Introduction of Scaffolding Pipe

Scaffolding pipe is usually made up of LSAW steel pipe or ERW steel pipe, its process types include: hot rolled/hot expended, electric resistance/high frequency. It has a variety of specifications, according to the diameter it can be divided into: Φ3.0, Φ2.75, Φ3.25, Φ2.5. Its length also has a variety of specifications: half a meter in a specification from 1 to 6 meters; it can be processed in accordance with customer specifications. The thickness is generally 2.4--2.7 mm and the diameter is 48 mm. The surface is generally not handled, individually coated with anti-rust paint. The material scaffolding pipe is: Q195, Q215 or Q235. The implementation of standard of scaffolding pipe is: SY/T5768-95 and GB/T3091-2001.

Different types of construction use different scaffolding and formwork support. At present, the bridge support frame mostly uses bowl buckle scaffolding, but also uses door scaffolding. The main structure of the construction of scaffolding mostly uses scaffolding scaffolding, scaffolding pole vertical distance is generally 1.2 ~ 1.8m; span is generally 0.9 ~ 1.5m.

Adaptability of scaffolding pipe:

1) to build various forms of scaffolding, templates and other support frame;
2) assembly of bone frame;
3) to set up ramps, sheds, stands and other temporary structures;
4) for other kinds of scaffolding support, strengthen the bar.

Carbon Steel Pipe Application: Construction Steel Pipe

According to whether there is a weld seam on pipe wall, construction steel pipe is divided into seamless steel pipe and welded steel pipe. Seamed steel pipe is also divided into spiral welded pipe and LSAW steel pipe according to the different kinds of weld seam. Both of those are used very commonly in the construction piling, structure, steel structure, load bearing, drainage and other aspects of the application. The material of construction steel pipe mainly includes carbon steel, stainless steel, and alloy steel. Among those material, carbon steel material application is the most extensive. The length of the steel pipe can be carried out length according to the requirements of customer, and also can be scattered feet. Construction seamless steel pipe can be divided into: hot-rolled seamless pipe, cold drawn tube, precision steel pipe, thermal expansion pipe, cold spinning pipe and extrusion pipe according to the production method. Hot-rolled tubes are used more in the construction industry.

Welding Quality Control Measures of LSAW Steel Pipe

Large diameter LSAW steel pipe with its big wall thickness, good material, stable processing technology, becomes the preferred pipe by largest domestic and foreign oil and gas transportation project. In the large diameter LSAW steel pipe welded joints, weld and heat affected zone are the most prone to produce a variety of defects, and welding undercut, pores, slag, not fused, not penetration, welding cracks are the main form of welding defects, and also are the origins those often make LSAW steel pipe produce quality accident. The quality control measures will be listed below, if you you are interested in the production process of LSAW steel pipe, you can click the hyper-link.

1.The quality control before welding:

1) First of all, pipe manufacturer should take control of the quality of raw materials, after passing the inspection, raw materials can formally enter the construction site. And pipe manufacturer resolutely put an end to the use of substandard steel.
2) The next is the management of the welding material. Checking whether the welding material is a qualified product, whether storage and baking system is implemented, whether the surface of the welding material is clean and no rust, and whether the electrode coating is intact, with mildew or not.
3) The next is the welding area cleaning management. Check the cleaning quality of the welding area, there shall not be water, oil, rust and oxide film and other dirt, which plays an important role to prevent the occurrence of external defects in the weld.
4) Finally, choosing the appropriate welding method, it should be implemented before the test welding, after welding principle.

2. The quality control during welding:

1) According to the welding process to review the specifications of the wire and flux is correct or isn't, to prevent the wrong welding wire and flux caused by welding quality accidents.
2) Monitor the welding environment, when the welding environment is not good (temperature below 0 ℃, relative humidity greater than 90%) pipe manufacturer should take appropriate measures after welding.
3) Checkout the groove size, including the gap, blunt edge, angle and wrong, etc. meet the process requirements or not before pre-welding.
4) Checkout the selected welding current, welding voltage, welding speed and other process parameters are correct or aren't in the submerged arc internal and external welding process.
5) Supervise the welding personnel in the submerged arc internal and external welding full use of the length of the pipe end of the arc plate to strengthen the internal and external welding arc plate use efficiency, which helps to improve the quality of pipe end welding.
6) Supervise the welding staff in the welding is the first clean up the slag, whether it has been completely handle joints, groove whether there is oil, rust, slag, water, paint and other dirt.

The Principle of Submerged Arc Welding

Submerged arc welding (SAW) is a method that burning under flux layer to weld. SAW is one of the most occurring arc welding process. It needs a electrode which may be solid of tubular. The electrode should be used in a continuous approach. It should be fed continuously.Flux refers to a material that can thaw the formed slag and gas when welding, and has the protection and metallurgical treatment to melt metals.The wire is the material that as a filler metal or as a conductive wire for welding.

Submerged arc welding is commonly used to manufacture LSAW steel pipe and SSAW steel pipe, and those two kinds of steel pipe are widely used in various kinds of production and transportation activities. The main feature of submerged arc welding is that the weld and the arc area is protected from environmental contamination by the application of a granular flux which is fusible. The weld pool is protected by a blanket of flux. So that area is actually submerged under that flux. When temperature rises and molten the flux becomes conductive. And thus this creates a path for electron flow between electrode and workpiece. SAW or Submerged Arc welding can be done by manual procedure or automatic process. But it can be done by semi-automatic process where welding gun is hold by hand.

LSAW Steel Pipe Manufacturing Process

LSAW steel pipe manufacturing process is simple, its production efficiency is high and at low cost, the development of straight seam welded pipe is rapid. Therefore, the straight welding is mostly used in smaller diameter of steel pipe. Today, as an excellent steel pipe manufacturer, Prime Steel Pipe will share the LSAW steel pipe manufacturing process in details for all of you.

LSAW steel pipe Manufacturing process:

1.Plate Analyzing：After the steel plate used to manufacture large diameter LSAW steel pipe entering into the production line, steel pipe manufacturer should carry out ultrasonic testing to the whole plate;

2.Edge Milling: Through the milling machine to carry out double-sided milling on both sides of the steel plate, to make it achieve the required plate width, board parallelism and groove shape;

3.Edge Crimping: Using the pre-bending machine to preliminary rolling, so that the board has the required curvature;

4.Molding: In the JCO forming machine At the first, steel pipe manufacturer should do stamping repeatedly for half of the pre-bent steel plate in the JCO forming machine, so that the steel plate is formed "J" shape, and then bending the other half of steel plate to form "C" shape, and finally formed the opening of the "O" shape;

5.Tack Welding: Making the LSAW steel pipe after forming joint colse and using the gas shielded welding (MAG) for continuous welding;

6.Automatic Internal Welding: Using vertical multi-wire submerged arc welding (up to four silk) to weld in the inside of the LSAW steel pipe;

7.Automatic External Welding: Using vertical multi-wire submerged arc welding to weld in the outside of LSAW steel pipe;

8.Automatic UT I: Using Automatic UT to 100% test the inside and outside wleded seam of LSAW steel pipe and the base material on both sides of weld seam;

9.X-Ray Testing I: Carrying out 100% X-ray industrial television inspection on the inside and outside the weld seam, and using image processing system to ensure the sensitivity of testing;

10.Mechanical Expanding: Expanding the full length of LSAW steel pipe to improve the dimensional accuracy of steel pipe and improve the distribution of stress in steel pipe;

11.Hydrostatic Testing: Testing the steel pipe after expanding one bu one in the hydraulic test machine to ensure that the steel pipe to meet the standard requirements of the test pressure, the machine has automatic recording and storage functions;

12.Chamfering: the pipe passed the inspection will be carried out pipe end processing qualified, to achieve the required pipe end groove size;

13.Automatic UTⅡ: Testing pipe one by one again by using root ultrasonic inspection to examine if there is defect on LSAW steel pipe after expanding and hydrostatic testing;

14.X-Ray TestingⅡ: Carrying out X-ray industrial television inspection on the pipe after expanding and hydrostatic testing, and take photos of the weld seam in the end;

15.Pipe End Magnetic Particle Testing(MPT): Carry out this inspection to find pipe end defects;

16.Corrosion protection and coating: Qualified steel pipe will carry out corrosion and coating according to user requirements.

Pipe Application: Piling Steel Pipe

Piling steel pipe is the steel pipe that made of steel or strip after crimping, specifications includes φ219-φ2232 different wall thickness, the implementation of SY/T5037-2000, GB/T9711.1-1997 standards and APISpec5L standards. It is widely used in natural gas, oil, chemical, power, heat, water supply and drainage, steam heating, hydropower station pressure pipe, thermal power, water and other long-distance pipeline and piling, bridges, steel and other engineering fields. The anti-corrosion method of punching steel pipe is also started by controlling one of the process. For example, add anticorrosion coating to outer surface of the pipe, which will increase the circuit resistance and decrease the corrosion current; coupled with DC power, so that the steel pipe causes negative potential to the soil and form the cathodic protection, which can eliminate the anode and cathode.

Piling steel pipe commonly adopts spiral welded pipe and LSAW steel pipe with large diameter. The surface of steel pipe weld seam shall not have cracks, arc breaking, crater, porosity and other defects. If there are above-mentioned defects existing, repairing welding is allowed, repairing welding is allowed. It is allowed to that there are steel strip butt weld on the steel pipe, and the steel pipe is allowed to be docked by two pipe sections. The welding can be carried out by submerged arc welding or manual welding. The main production process of piling steel pipe is mainly double-sided submerged arc welding technology. More detailes about submerged arc welding process and its pros and cons, please click the hyper-link to know.

Markings of piling steel pipe

Each of the accepted piling steel pipe should be marked with fadeless paint, and we should along the perimeter of the piling steel pipe brush 50mm wide white paint at about 200mm from the inside of the pipe end. The steel pipe used for the red pipe should mark red paint to show the difference:

1. Color should be eye-catching, and should ensure that the piling steel pipe exposed to the air at least 4 months does not fade;
2. Marking color should be from the end of 200mm, and brush the entire circumference, the letter height should be at least 25mm;
3. Using metric units;
4. The number of piling steel pipe should be compiled in sequence;
5. Piling steel pipe should have number;
6. doing die marking on the end of the pipe directly facing longitudinal weld seam.

What is Welded Steel Pipe?

Welded steel pipe, also known as welded pipe, is the steel pipe that made of steel plate or steel strip after crimped and welded. The production process of welded steel pipe is simple, production efficiency is high, variety specifications are many, the investment of equipment is little, but its general strength is lower than the seamless steel pipe. Since the 1930s, with the rapid development of high-quality strip continuous rolling line and the improvement of welding and inspection technology, the quality of welding line has been increasing continuously, and the specifications of welded steel pipes have been increasing. And welded pipe have replaced the seamless steel pipe in more and more field. Sewing steel pipe. The welded steel pipe is divided into straight seam welded pipe(also called LSAW steel pipe) and spiral welded pipe(also called SSAW steel pipe) according to the form of welding line.

Production process of LSAW steel pipe is simple, production efficiency is high, cost is low, and it develops rapidly. The strength of the SSAW steel pipe is generally higher than that of the LSAW steel pipe, and the SSAW steel pipe with larger diameter can be produced with the narrow billet. And it also can use the billet with the same width to produce t SSAW steel pipe with different diameter. However, compared with the straight seam welded pipe in identical length, the length of welding line increased by 30 to 100%, and the production rate was low.

Therefore, pipe manufacturers usually use straight seam welding to produce the smaller diameter of the pipe, use spiral welding to produce large diameter welded pipe.

Types of Welded Steel Pipe

1. Welded steel pipe (GB/T3092-1993) used in Low-pressure fluid delivery, also known as the general welded pipe, commonly known as black tube. It is the welded steel pipe that used to transport of water, gas, air, oil and heating steam, and other generally fluids with lower pressure. Steel pipe is divided into ordinary steel pipe and thickened pipe according wall thickness; is divided into non-threaded steel pipe (light pipe) and threaded steel pipe according to the form of pipe end. The specifications of the steel pipe are denoted by nominal caliber (mm), and the nominal caliber is the approximate value of the inner diameter. It traditionally uses inches to express, such as 11/2 and so on. Welded steel pipe used in Low-pressure fluid delivery in addition to directly use for the transport of fluid, but also is used as the original tube of galvanized welded steel pipe used in Low-pressure fluid delivery.

2. Galvanized welded steel pipe (GB/T3091-1993) used in Low-pressure fluid transmission, also known as galvanized welded steel pipe, commonly known as white tube. It is the hot dipping galvanized welded (butt weld or electrowelding) steel pipe used to transport water, gas, air oil and heating steam, warm water and other generally fluids in lower pressure. Steel pipe is divided into ordinary galvanized steel pipe and thick galvanized steel pipe according to wall thickness; is divided into non-threaded galvanized steel pipe and threaded galvanized steel pipe according to the form of pipe end. It traditionally uses inches to express, such as 11/2 and so on.

3. Ordinary carbon steel electric wire conduit (GB3640-88) is used in electrical installation ( such as the industrial and civil construction and installation of electrical equipment and other works) to protect the wire of the steel pipe.

4. LSAW steel pipe (YB242-63) is the pipe that the weld longitudinally parallel to steel pipe. It is usually divided into metric welded steel pipe, welded thin-walled pipe, transformer cooling tubing and so on.

5. SSAW steel pipe (SY5036-83) for pressurized fluid delivery is made of hot-rolled steel coil as tube blanks, spirally forming in normal temperature and welded by double-sided submerged arc welding, used for pressurized fluid delivery. The loading capacity of steel pipe is strong, welding performance is good, after a variety of strict scientific inspection and testing, it can be used safely and reliably. The diameter of steel pipe is big, transport efficiency is high, and it can save the laying of pipeline investment. So it is mainly used for conveying oil and gas pipelines.

6. ERW steel pipe used for pressurized fluid transmission (SY5038-83) is made of hot-rolled steel coil as tube blanks, spirally forming in normal temperature, welded by high-frequency lap welding, used for pressurized fluid transportation. The loading capacity of steel pipe is strong, plasticity is good, and it is easy to weld and machine shaping. After a variety of rigorous and scientific inspection and testing, the pipe is safe and reliable to use, the diameter of steel pipe is large, transport efficiency is high, and it can save the laying of pipeline investment.

7. Spiral welded steel pipe (SY5037-83) used in general low-pressure fluid transmission is made of hot-rolled steel coil as tube blanks, spirally forming in normal temperature, use double-sided automatic submerged arc welding or single-sided welding method to weld. It is used for water, gas, air and steam and other general low-pressure fluid transmission.

8. ERW steel pipe (SY5039-83) used in general low-pressure fluid transmission is made of hot-rolled steel coil as tube blanks, spirally forming in normal temperature, use high-frequency lap welding to weld,. It is used for general low-pressure fluid delivery.

9. Spiral welded steel pipe (SY5040-83) used as pile is made of hot-rolled steel coil as tube blanks, spirally forming in normal temperature, use double-sided submerged arc welding or high-frequency welding to make. It is used for civil construction, wharf, bridge and other foundation pile steel pipe.

Differences between LSAW Steel Pipe and Spiral Welded Pipe

Welded carbon steel pipe includes LSAW (longitudinal submerged arc welded) steel pipe and spiral welded pipe. Some people those do not very understand this industry may not know differences between the former and the latter very clearly. Don’t worry, today we will talk about this topic.

Spiral welded pipe is made by using low carbon construction steel strip or low alloy structural steel strip to roll into a tube according to a certain helix angle (called the forming angle), and then welding the seam together. It can use the narrow band steel to produce steel pipe with large diameter. Spiral welded pipe is mainly used for oil and natural gas pipeline, its specifications are expressed by outer diameter * wall thickness. Spiral welded pipe with also includes single-sided welding and double-sided welding.

LSAW steel pipe is made by using strip steel as raw materials and doing longitudinal welded in the high-frequency welding equipment(hence the name due to the weld forms a straight line). In accordance with the use of different, there are different following production process (can be divided into scaffolding tube, fluid tube, wire casing, bracket tube, fence tube, etc.).

From the production process, the production process of straight seam welded pipe is simple, the production efficiency is high, the cost is low, and it develops rapidly. But the strength of the spiral welded pipe is generally higher than that of the LSAW steel pipe. Spiral welded pipe with larger diameter can be produced with the narrow billet, and the pipe with different diameter can also be produced with the same width. However, compared with the same length of the LSAW steel pipe, the weld length of spiral welded pipe increased by 30 to 100%, and the production rate of it is low.

From the welding process, the welding method of spiral welded pipe and straight seam welded pipe is consistent. But the straight seam welded pipe will inevitably have a lot of T-shaped welds, so the probability of appearing welding defects are greatly improved. And the welding residual stress at TIG welding is large, the weld metal is often in three-dimensional stress condition, which increases the possibility of producing crack. Moreover, according to the submerged arc welding process, each weld should have starting arc place and arc blowout place, but each LSAW steel pipe can not achieve the conditions in the welding ring, which may cause there are more welding defects in the arc blowout place.

Welded Pipe vs. Seamless Pipe

Advantages Of Welded

Welded pipes are typically more cost effective than their seamless equivalents.

Welded pipes are usually more readily available than seamless. The longer lead time required for seamless pipes can not only make timing problematic, but it also allows more time for the price of the materials to fluctuate.

The wall thickness of welded pipes is generally more consistent than that of seamless pipes.

The internal surface of welded tubes can be checked before manufacturing, which isn’t possible with seamless.

Advantages Of Seamless

The main perceived advantage of seamless pipes is that they don’t have a weld seam. Traditionally, the seam of welded pipes has been viewed as a weak spot, vulnerable to failure and corrosion. For many years, this fear was probably justified. However, in recent years improvements in the manufacturing process for welded steel pipes and other welded pipes have boosted the strength and performance of the weld seam to levels indistinguishable from that of the rest of the pipe.

Seamless pipes provide peace of mind. Although there should be no issues with the seams of welded pipes supplied by reputable manufacturers, seamless pipes prevent any possibility of a weak seam.

Seamless pipes have better ovality, or roundness, than welded pipes.

Get Welded Or Seamless For Your Next Project

Need more help deciding between welded and seamless? Contact us so we can help you determine the needs of your project. We have a large inventory of welded carbon pipes, steel pipes and more, as well as an equally robust selection of their seamless counterparts.

Why Use Welded Pipe

Structural welded pipe (tubing) can be used for a wide variety of mechanical applications. It may be used either statically or dynamically. Its close tolerances, good finish, and dense structure make it ideal for parts such as structural support and parts, frames, racks, trailer beds and trailer components, structural components and supports for buildings, bridges, and highways, conveyors, machine parts, ornamental usages and a wide range of applications in industrial, construction, automotive, appliance and agricultural industries. 

Welded pipes are generally more cost effective than the equivalent seamless alternative. They are significantly more available both from distributor and mill stocks and from a mill production lead time perspective. With longer lead times seamless tubes can be exposed to unknown alloying price extras that can fluctuate substantially, hence it can be difficult to plan and predict the true costs for the material. Therefore in addition to faster delivery times for Erw tubes, there is the added advantage of lower economical risk. Erw welded steel tubes generally have better surface quality as compared with manufacturing seamless tubes. Seamless tubes are generally made in multiple steps starting with hot extrusion to form the tube hollows from billets.

Do you need welded pipe? Check out our welded offers, then contact us for a quote. We’d love to discuss the needs of your next project.

Welded Pipe Manufacturing

Three types of welding processes:

Electric Resistance Welding: During ERW, a high frequency electrical current is transmitted to

the material by means of copper sliding contacts so that the abutting edges initiate fusion as they come into contact.

Longitudinal Submerged Arc Welding: In LSAW, the butt joint of the pipe is welded in at least two phases, one of which is on the inside of the pipe. The welds are made by heating with an electrode arc between the bare metal electrodes. Pressure is not used. Filler metal for the welds is obtained from the electrodes.

Spiral Submerged Arc Welding: Spiral SAW allows large diameter pipes to be produced from narrower plates or skelps. During this process, the weld pool is protected against oxidation by a flux produced from the electrode fed separately onto the weld.

The Best Welding Way to Weld Steel Pipe

The best way to welding steel pipe:

First of all, cleaning the oil, paint, water, rust ect. on welded steel pipe,  then opening groove

according to the wall thickness , larger open on thick wall, smaller open on thin wall (grinder), then the gap on pipe, usually the diameter of the rod or wire is 1-1.5 times, if you do a mistake and largered the groove , then smaller the gap. Tack welding at least three points, four points better in general work.

When welding should be finish in half and half, the best start point should one centimeter higher than the lowest point which is good for connection.  If the pipe wall thickness, it should be layered, at least two layers, the first layer full circle after welding can weld the second layer.

Heat Treatment of LSAW Steel Pipe After Welding

LSAW steel pipe after heat treatment is a new technology to eliminate residual stress. After the material is preheated before welding to heat treatment temperature and the butt welding process to maintain the temperature of the continuously heated member, after the welding is completed using its thermal insulation cotton allowed to cool slowly. This method can effectively reduce the welding residual stress and improve resistance to stress corrosion of metals.

Internal weld NDT since the large steel pipes in water supply project belongs, especially the

thickness t = 30mm steel is used as a pipe bridge, both to withstand water pressure inside, but also the burden of its own weight and the water formed by a steel pipe moment, so the welding quality requirements are particularly high. For pipe bridge with a thickness t = 30mm large-diameter pipe, the longitudinal seam and girth weld belong to a class, require 100% of X-ray film examination and 100% ultrasonic flaw detection; and thickness t = 24mm buried pipe, longitudinal seam welding belongs to a class for 20% of the X-ray film examination and 50% of the ultrasonic flaw inspection.

Post weld heat treatment can effectively reduce the welding residual stress, and heat treatment temperature is higher, residual stress better. Large-diameter pipe post weld heat treatment can effectively improve the stress corrosion resistance of large diameter pipe, the higher the heat treatment temperature, resistance to stress corrosion increased more significant. Diffusion method metal carbide coating technology is the workpiece placed in special medium, formed by diffusion of metal carbide layer of a few microns to tens of microns on the workpiece surface. Anti-corrosion anti-corrosion of buried large diameter steel pipe and clear tubes are used to hang galvanized wire, spraying compressive strength of not less than 30N / mm2 of cement mortar lining.