SAW vs ERW and EFW Welded Steel Pipe

Keywords:SAW Welded Pipe, ERW Steel Pipe, Electric Fusion Welded Pipe, Welded Steel Pipe

Carbon steel welded pipes can be divided into three types: Longitudinal submerged arc welded steel pipes (LSAW), Spiral welded steel pipes (SSAW), and Electric resistance welded Steel Pipe (ERW, also called high-frequency straight seam welded steel pipes according to the forming method of the weld seam.


What is SAW steel pipe?

SAW steel pipe (Submerged Arc Welding Steel Pipe), it can be classified into longitudinal submerged arc welding steel pipe (LSAW steel pipe) and spiral submerged arc welding steel pipe (SSAW steel pipe). SAW is a manufacturing process using submerged arc welding of steel,this process produces high current density, which prevents the flux layer from losing heat quickly and concentrates in the welding region. Commonly used standard is API 5L.


Submerged arc weld of high quality, high production efficiency, arc and smoke a few characteristics of submerged arc welded pipe is widely used in pressure vessels,pipe manufacturing, beams, low pressure fluid, steel works.


ssaw steel pipe


1) LSAW steel pipe (Longitudinal submerged arc welded steel pipe)

Longitudinal submerged arc steel pipe is a steel pipe with a weld seam parallel to the longitudinal direction of the steel pipe. It is made of hot-rolled or cold-rolled steel plates or steel strips that are curled and welded. The production process of straight seam welded pipe is simple, the production efficiency is high, the cost is low, and the development is rapid. Straight seam steel pipes are widely used in water supply projects, petrochemical industry, chemical industry, electric power industry, agricultural irrigation, and urban construction.

2) SSAW steel pipe (Spiral welded steel pipe)

Spiral welded steel pipe is made of strip steel coils as raw materials, rolled into tube blanks at a certain spiral angle, and then welded together. It can use narrow strip steel to produce large diameters. steel pipe. Spiral steel pipes are mainly used in drainage and water supply projects, fluid liquid, and solid transportation pipelines. It is widely used in urban construction and municipal engineering.

The strength of spiral welded pipes is generally higher than that of straight seam welded pipes. Welded pipes with larger diameters can be produced from narrower billets, and welded pipes with different diameters can also be produced from billets of the same width. However, compared with straight seam pipes of the same length, the weld length is increased by 30~100%, and the production speed is lower.


What is ERW steel pipe?

ERW steel pipe (Electric Resistance Welded Steel Pipe) uses the skin effect and proximity effect of high-frequency current to heat and melt the edge of the pipe blank after the hot rolled coil is formed by a forming machine, and presses it under the action of a squeeze roller Welding to achieve production. ERW has the characteristics of high efficiency,low cost,material saving and easy automation,it is widely used in aviation,aerospace,energy, electronics,automotive,light industry and other industrial sectors,is an important link in the welding process.


What is EFW steel pipe?

EFW steel pipe (Electric Fusion Welding) refers to an electron beam welding, the use of high-speed movement of the electron beam directed impact kinetic energy is converted to heat the workpiece so that the workpiece leaving the melt, the formation of the weld. EFW steel pipe is formed by rolling plate and welding the seam. The weld flash can be removed from the outside or inside surfaces using a scarfing blade. The weld zone can also be heat treated to make the seam less visible. Welded pipe often has tighter dimensional tolerances than seamless, and can be cheaper if manufactured in the same quantities. It is mainly used for welding dissimilar steel welding sheet or which high power density, metal weldment can rapidly heated to high temperatures, which can melt any refractory metals and alloys. Deep penetration welding fast, heat-affected zone is extremely small, so small performance impact on the joints, the joint almost no distortion. But it has a requirement on a special welding room because welding using X-rays. 


ERW steel pipe


SAW Welded Steel Pipe vs ERW Welded Steel Pipe


In manufacturing processes,we can see SAW welded pipes (LSAW, SSAW) and ERW welded pipes have completely different forming and welding methods

1) SAW welded steel pipe manufacturing process:
In the single-seam SAW welded steel pipe,submerged arc welding process is used for welding.In this method,a welding arc is submerged in welding flux. A continuous solid filler wire is input from the outside. The pipe is double-welded, first is inside and then welding from the outside.
In the case of double seam SAW welded steel pipe, the first two halves are connected by tack welding, which is called fit-up. Double seam saw steel pipe has two opposite weld seam. Both seams are welded from inside and outside of the pipe.
In a spiral SAW welded pipe, steel plate from the de-coiler is formed in a spiral loop.This spiral loop is then welded from inside and outside of the pipe.Because of the method of manufacture, a wide variety of diameters can be produced. SSAW welded pipes are used for low-pressure services.
Whereas LSAW welded pipes are used for medium to high-pressure services. SSAW welded pipes are less costly compared to LSAW welded pipe.

2) ERW welded steel pipe manufacturing method:
When ERW welded steel pipe welding process, two electrodes, usually made from copper, are used to apply pressure and current. The electrodes are disc shaped and rotate as the material passes between them. This allows the electrodes to stay in constant contact with the material to make long continuous welds.

As ERW welded steel pipe and SAW welded steel pipe in the pipe during forming,welding and process is different,so that two kinds of steel pipe in the performance there are some differences:
1. The surface quality.
Though both SAW pipes and ERW welded pipes all have weld seam.The welding seam of ERW pipe is flat,smooth and better than SAW (LSAW,SSAW) pipes.In most of the SAW pipes, it is mainly about the weld reinforcement internally and externally.

2. ERW welded steel pipe weld defect types is less than the SAW welded steel pipe.
Because of the solvent deposited in SAW, in addition to volume defects it results in more defects.The defects found in ERW welded steel pipes are only straight welds and wire-line and are easy to inspect. The defects can be noticed easily and the ultrasonic reflection on the surface makes it easier to detect.

3. The residual stress ratio in ERW is lower than SAW welded pipes.
ERW welded steel pipe related to SAW welded steel pipe in residual stress ratio is low. Since ERW welded pipe deformation in the deformation process more fully, coupled subsequent sizing flat oval,elliptical vertical changes and necking, making ERW welded pipe residual stress becomes smaller. Physical testing showed that the same specifications, the same material ERW welded pipe after incision along the axis, the axial and transverse incisions smaller displacement than the SAW welded pipe.

4. The overall performance.
Although the overall performance of both ERW welded pipe and SAW welded pipe are the same,when the pipe becomes defective,the steel scrap and welding can be done on ERW welded pipe,while it is not the same in case of SAW, which would result in cracking or corrosion.So ERW welded pipe are more durable than SAW welded pipe.


SAW Welded Steel Pipe vs EFW Welded Steel Pipe


EFW Pipe full meaning is Electric Fusion Welding Pipe. EFW Pipe are manufactured by using high electric voltage through the material to melt and weld it. EFW Pipe manufacturing does not require any extra welding wire. It is an autogenous pipe welding process (you can join same material to itself without adding any additional welding filler). This make is highly suitable to make pipe from 6 inches size to 100 inches size diameter.


One of submerged arc welding (SAW)-electric welding (EFW) is a process in which metal is heated by one or several consumable electrodes and a workpiece to heat the metal, and the arc is used to make the metal and fill. The material is fully melted and does not require pressurization. The part of the filling metal is all from the electrode. Melt Gas Shielded Welding (GMAW)–A type of electrofusion welding (EFW) that is similar to submerged arc welding, but its protection comes from inert gases and works better.


Spiral welding (SSAW steel pipe)–this is also a type of submerged arc welding with a spiral weld.


Manufacturing machine for efw steel pipe:

A combination of specially designed equipments like 1600MT press brake machine, multiple rolls bending machine, welding installations for outside, inside and circumferential welding, size calibrating press, solution annealing furnace and a host of other related machinery, is employed to manufacture pipes used in critical applications like refineries, fertilizers, LNG terminals, cross country pipe lines etc.

                                          

Standard of efw steel pipe: ASTM A672        


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