How to Make ERW Pipe: A Step-by-Step Guide

To make ERW pipe, steel coils are transformed into welded tubes through a step-by-step process. This guide covers material selection, forming, welding, and finishing steps to produce high-quality ERW steel pipes. Follow along to learn how to make ERW tube efficiently.

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Table of Contents

What are ERW Pipes and Tubes

ERW pipes full form Electric Resistance Welded pipes, are a type of steel pipe manufactured using the electric resistance welding (ERW) process. This erw pipe cold formed is a flat steel strip into a cylindrical or rectangular shape and then welding the edges together using an electric current. The result is a strong, durable, and highly resistant to corrosion.

ERW pipes are widely used across various industries due to their superior properties. In the oil and gas sector, they are essential for transporting fluids under high pressure. The petrochemical industry relies on ERW tubes for their ability to handle hazardous materials safely. In construction, these pipes are valued for their strength and reliability in structural applications. The automotive and aerospace industries also utilize ERW tubes for their precision and performance in critical components.

Raw Materials for ERW tube Manufacturing process

High-quality ERW tubes start with selecting superior raw materials. Steel coils, known for their strength and durability, are the primary materials used. Commonly utilized materials include Hot Rolled (HR) Coils, Mild Steel, and Galvanized Iron, each bringing unique properties to the production process of erw steel pipe. Stainless steel pipes, known for their excellent corrosion resistance, are also highly valued in various applications.

The quality of these raw materials is crucial. Superior steel coils ensure the final product withstands its intended pressures and demands. The durability and reliability of ERW tubes heavily depend on these materials, making them a vital starting point.

Mild steel, with its carbon content of 0.3% or less, is particularly favored in the production of carbon steel ERW pipes and the erw steel pipe range, including mild steel pipe. This low carbon content enhances the structural integrity and performance of the pipes, making them suitable for a wide range of industrial uses.

Galvanized Iron Pipe (GI) is made from galvanized iron, and this layer of zinc acts as a protection against corrosion, greatly extending the life of the coated iron pipe. Galvanized steel pipes are highly resistant to corrosion, making them ideal for use in clean water supply lines.

Read this article to learn what are MS/GI/GP/ERW tubes and pipes!

Cold Rolling Processing and Slitting Machine

When we produce steel pipe, we first need to consider the wall thickness and size of the steel plate, we can choose to buy the right steel coils and produce them directly, or we can consider to start from hot rolled coils and go through cold rolling to get the right thickness of coils, and then go through the slitting machine to get the right width of coils.

Cold Rolling Mill Machine is used to continuously calender metal sheets (such as steel, aluminum, copper, etc.) through rolls at room temperature to thin their thickness and improve surface quality and mechanical properties. Through multi-pass rolling, tension control and precision adjustment of rolls, it eliminates residual stress after hot rolling and improves material strength, flatness and finish. It is suitable for the production of thin plates and precision strips, and has the advantages of high dimensional accuracy and no oxidized layer on the surface. Learn more about Cold Rolling Mill Machine.

Coil steel slitting machine are metal processing equipment used to cut metal coils along the longitudinal direction into a number of narrow-width materials. It slits wide steel coils into narrow strips of the required width through the processes of uncoiling, leveling, longitudinal shearing by multiple sets of disc knives, and rewinding, and is suitable for precision machining of materials such as stainless steel, aluminum alloy, carbon steel, and so on. Learn more about Slitting Machine.

Uncoiling and Flattening Process

The journey from raw material to finished product begins with the uncoiling and flattening of the steel coils. During uncoiling, the packaging of the incoming steel coils is removed, preparing them for subsequent steps.

The flattening process is a critical step where the steel coil is transformed into a flat strip. This step eliminates any residual curvature, ensuring a uniform steel strip ready for further processing. The coils are fed through flattening rolls, which shape them into a flat strip necessary for subsequent manufacturing steps.

Ensuring a smooth and even surface during the flattening process is crucial for the quality of the final ERW pipe product. A uniform steel strip sets the stage for effective welding and ultimately, a high-quality pipe.

Coil Joining Techniques

Once the flat steel strip is flattened, the next step is to join the coil ends to create a continuous strip. The primary method used for this purpose is butt welding, which joins the edges of the coil ends seamlessly. This technique is essential for maintaining a continuous production flow.

In some mills, tab setting is used to ensure complete edge-to-edge welds, particularly for products like coaxial cables. This technique helps in achieving precise and strong welds, which are crucial for the structural integrity of the final product.

Coil end joiners play a vital role in maintaining the flow of material without interruptions. Minimizing downtime and waste, these joiners keep the manufacturing process efficient and cost-effective. This continuous strip is then ready for further processing, leading to the creation of high-quality ERW pipes.

Edge Trimming for Precision

Precision is key in ERW tube manufacturing. The edge trimming process ensures the steel strip achieves the exact width needed for further processing, vital for effective welding and structural integrity.

Slitter blades and edge milling are the primary tools used in this process. These tools trim the strip edges to the precise width required, ensuring that the subsequent welding process can be carried out with high accuracy. This precision is crucial for the overall quality and performance of the final ERW pipes.

Strip Accumulator

This machine is used in steel tube mill production lines, between the shear welder and the forming section, and its role is to store enough strip to ensure the continuation of the production of subsequent equipment.

Cage Strip Accumulator

Horizontal Loop Accumulator

Landed Spiral Loop Accumulator

There are three common types of cages, the Cage Strip Accumulator, the Horizontal Loop Accumulator and the Landed Spiral Loop Accumulator. know more about strip accumulator.

Forming, High Frequency Resistance Welding and Sizing Process

As the core equipment of the steel tube mill production line, the forming, high-frequency welding and sizing machine is responsible for processing the steel strip into round or rectangular shape, and then heated up by high-frequency resistance welding to bond the edges of the strip to form a solid weld. Then it passes through the cooling water tank and enters the sizing station to get the pipe that meets the precise specification.

Forming section in pipe mill machine

The forming station is used for bending metal strips into specific cross-sectional shapes (e.g. round, square, etc.) by means of a multi-roll press. The strip is continuously molded by precision roll sets to form a closed pipe shape in preparation for subsequent high-frequency welding.

General pipe forming has two kinds of round to square tube and directly into a square tube, round to square refers to the forming section of the strip rolled into a round shape and then rolled into a square by the sizing station, directly into a square refers to the forming section directly rolled into a square.

High Frequency Induction Electric Resistance Welding

High-frequency induction welding, a state-of-the-art technology, is used for manufacturing ERW pipes up to a 21-inch diameter. The tube mill machine plays a crucial role in this process, facilitating the production of various types of steel pipes, including ERW and stainless steel pipes. Welding current is transmitted through a work coil without contact, heating and bonding the edges of the steel strip to form a welded joint. The high-frequency electrical currents generate the necessary heat to bond the edges of the steel strip without the need for filler material, resulting in a clean and strong weld. This method has largely replaced low-frequency welding methods due to its efficiency and effectiveness.

A significant advantage of high-frequency induction welding is the elimination of contact marks and reduced setup time for size changes, enhancing overall manufacturing efficiency. Monitoring the welding process is essential to detect any defects and ensure proper seam integrity, ensuring that the final product meets the highest standards.

Clamp systems ensure proper alignment and heat management during welding. This precise control is vital for producing high-quality ERW tubes with consistent welds. This article details the High Frequency welding.

Sizing and Straightening the Pipe

The sizing process ensures the welded pipe meets specific tolerances for roundness, diameter, and straightness, critical for performance in various applications.

Post-welding, the pipe undergoes sizing to ensure it meets precise specifications for roundness, outer diameter, and straightness. Dimensional inspections are performed to verify that the dimensions of the pipes meet specified standards.

Ensuring the pipe meets these precise specifications is crucial for its performance and reliability. This step is essential for producing high-quality ERW pipes that meet industry demands.

Cutting the Pipe to Desired Lengths

After sizing and straightening, the next step is to cut the pipes and tubes to the desired lengths. This is achieved using a flying cut-off saw, which enables continuous cutting of pipes without interrupting the production line.

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Flying cut-off saws cut the sized pipe to required lengths post-sizing, contributing to higher production speeds with fast and accurate cuts, ensuring manufacturing efficiency.

Accurate cuts meet customer specifications and ensure the pipes are ready for their intended applications, vital for maintaining the final product’s quality and consistency.

Flying saws include cold and hot saws, read this article to learn more about flying saws

Palletizers in Steel Tube Mill Line

Palletizers are the most important part of the tube packaging process, designed to automatically stack tubes onto pallets, according to the shape and size of the tubes into a variety of stacks suitable for storage and transportation, such as square bales, hexagonal bales and so on.

There are many different models of palletizers with different footprints and prices, so read this article to help you better choose the right palletizer for you!

Quality Control Measures

Quality control is crucial in ERW pipe manufacturing, ensuring compliance with industry standards essential for safety and performance. High quality maintains the manufacturer’s reputation and attracts repeat customers.

Non-destructive testing methods, like ultrasonic and X-ray testing, identify flaws without causing damage, ensuring the pipes meet the highest standards of quality and reliability.

Advantages of ERW Pipes

Applications of ERW Pipes

Summary

New Victor Tube Mills is a manufacturer specializing in erw steel tube mill production line for 30 years. The company has 1 8 patented inventions in the welded pipe industry and exports more than 500 production lines worldwide to more than 70 countries. providing one-stop service for plant design, equipment production and after-sales installation, contact us to start your successful project!

Frequently Asked Questions

What raw materials are essential for ERW pipe manufacturing?

Steel coils, Hot Rolled (HR) Coils, Mild Steel, and Galvanized Iron are essential raw materials for ERW pipe manufacturing. These materials ensure the structural integrity and durability of the finished pipes.

Why is the flattening process important in ERW steel tube manufacturing?

The flattening process is crucial in ERW tube manufacturing as it removes any residual curvature from the steel coils, ensuring a uniform steel strip essential for the subsequent manufacturing steps. This uniformity directly contributes to the quality and integrity of the finished pipes.

What is high-frequency induction welding?

High-frequency induction welding is the process of transmitting welding current through a work coil to seamlessly bond the edges of a steel strip without the need for filler material, resulting in a strong and clean weld. This technique is efficient and widely used in various applications.

How are carbon steel pipe cutting machine work?

ERW tubes are efficiently cut to the desired lengths using flying cut-off saws, allowing for continuous operation without halting production. This method ensures precise and timely cutting.

What quality control measures are taken in ERW pipe manufacturing?

Quality control in ERW pipe manufacturing includes non-destructive testing methods such as ultrasonic and X-ray testing to detect any flaws, along with the utilization of high-quality steel coils to reduce corrosion and enhance the pipes’ durability.

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Welding by passing electric current through work pieces

Electric resistance welding (ERW) is a welding process in which metal parts in contact are permanently joined by heating them with an electric current, melting the metal at the joint.[1] Electric resistance welding is widely used, for example, in manufacture of steel pipe and in assembly of bodies for automobiles.[2] The electric current can be supplied to electrodes that also apply clamping pressure, or may be induced by an external magnetic field. The electric resistance welding process can be further classified by the geometry of the weld and the method of applying pressure to the joint: spot welding, seam welding, flash welding, projection welding, for example. Some factors influencing heat or welding temperatures are the proportions of the workpieces, the metal coating or the lack of coating, the electrode materials, electrode geometry, electrode pressing force, electric current and length of welding time. Small pools of molten metal are formed at the point of most electrical resistance (the connecting or "faying" surfaces) as an electric current (100–100,000 A) is passed through the metal. In general, resistance welding methods are efficient and cause little pollution, but their applications are limited to relatively thin materials.

Spot welding

[edit] Main article: Spot welding

Spot welding is a resistance welding method used to join two or more overlapping metal sheets, studs, projections, electrical wiring hangers, some heat exchanger fins, and some tubing. Usually power sources and welding equipment are sized to the specific thickness and material being welded together. The thickness is limited by the output of the welding power source and thus the equipment range due to the current required for each application. Care is taken to eliminate contaminants between the faying surfaces. Usually, two copper electrodes are simultaneously used to clamp the metal sheets together and to pass current through the sheets. When the current is passed through the electrodes to the sheets, heat is generated due to the higher electrical resistance where the surfaces contact each other. As the electrical resistance of the material causes a heat buildup in the work pieces between the copper electrodes, the rising temperature causes a rising resistance, and results in a molten pool contained most of the time between the electrodes. As the heat dissipates throughout the workpiece in less than a second (resistance welding time is generally programmed as a quantity of AC cycles or milliseconds) the molten or plastic state grows to meet the welding tips. When the current is stopped the copper tips cool the spot weld, causing the metal to solidify under pressure. The water cooled copper electrodes remove the surface heat quickly, accelerating the solidification of the metal, since copper is an excellent conductor. Resistance spot welding typically employs electrical power in the form of direct current, alternating current, medium frequency half-wave direct current, or high-frequency half wave direct current.

If excessive heat is applied or applied too quickly, or if the force between the base materials is too low, or the coating is too thick or too conductive, then the molten area may extend to the exterior of the work pieces, escaping the containment force of the electrodes (often up to 30,000 psi). This burst of molten metal is called expulsion, and when this occurs the metal will be thinner and have less strength than a weld with no expulsion. The common method of checking a weld's quality is a peel test. An alternative test is the restrained tensile test, which is much more difficult to perform, and requires calibrated equipment. Because both tests are destructive in nature (resulting in the loss of salable material), non-destructive methods such as ultrasound evaluation are in various states of early adoption by many OEMs.

The advantages of the method include efficient energy use, limited workpiece deformation, high production rates, easy automation, and no required filler materials. When high strength in shear is needed, spot welding is used in preference to more costly mechanical fastening, such as riveting. While the shear strength of each weld is high, the fact that the weld spots do not form a continuous seam means that the overall strength is often significantly lower than with other welding methods, limiting the usefulness of the process. It is used extensively in the automotive industry – cars can have several thousand spot welds. A specialized process, called shot welding, can be used to spot weld stainless steel.

There are three basic types of resistance welding bonds: solid state, fusion, and reflow braze. In a solid state bond, also called a thermo-compression bond, dissimilar materials with dissimilar grain structure, e.g. molybdenum to tungsten, are joined using a very short heating time, high weld energy, and high force. There is little melting and minimum grain growth, but a definite bond and grain interface. Thus the materials actually bond while still in the solid state. The bonded materials typically exhibit excellent shear and tensile strength, but poor peel strength. In a fusion bond, either similar or dissimilar materials with similar grain structures are heated to the melting point (liquid state) of both. The subsequent cooling and combination of the materials forms a “nugget” alloy of the two materials with larger grain growth. Typically, high weld energies at either short or long weld times, depending on physical characteristics, are used to produce fusion bonds. The bonded materials usually exhibit excellent tensile, peel and shear strengths. In a reflow braze bond, a resistance heating of a low temperature brazing material, such as gold or solder, is used to join either dissimilar materials or widely varied thick/thin material combinations. The brazing material must “wet” to each part and possess a lower melting point than the two workpieces. The resultant bond has definite interfaces with minimum grain growth. Typically the process requires a longer (2 to 100 ms) heating time at low weld energy. The resultant bond exhibits excellent tensile strength, but poor peel and shear strength.

Seam welding

[edit] "Seam welding" redirects here. For the geometrical welding configuration, see welding joint.

Resistance seam welding is a process that produces a weld at the faying surfaces of two similar metals. The seam may be a butt joint or an overlap joint and is usually an automated process. It differs from flash welding in that flash welding typically welds the entire joint at once and seam welding forms the weld progressively, starting at one end. Like spot welding, seam welding relies on two electrodes, usually made from copper, to apply pressure and current. The electrodes are often 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. The electrodes may also move or assist the movement of the material.

A transformer supplies energy to the weld joint in the form of low voltage, high current AC power. The joint of the work piece has high electrical resistance relative to the rest of the circuit and is heated to its melting point by the current. The semi-molten surfaces are pressed together by the welding pressure that creates a fusion bond, resulting in a uniformly welded structure. Most seam welders use water cooling through the electrode, transformer and controller assemblies due to the heat generated.

Seam welding produces an extremely durable weld because the joint is forged due to the heat and pressure applied. A properly welded joint formed by resistance welding can easily be stronger than the material from which it is formed.

A common use of seam welding is during the manufacture of round or rectangular steel tubing. Seam welding has been used to manufacture steel beverage cans but is no longer used for this as modern beverage cans are primarily seamless aluminum with a glued and curled radial joint.

There are two modes for seam welding: Intermittent and continuous. In intermittent seam welding, the wheels advance to the desired position and stop to make each weld. This process continues until the desired length of the weld is reached. In continuous seam welding, the wheels continue to roll as each weld is made.

Low-frequency electric resistance welding

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Low-frequency electric resistance welding (LF-ERW) is an obsolete method of welding seams in oil and gas pipelines. It was phased out in the s but as of some pipelines built with this method remained in service.[3]

Electric resistance welded (ERW) pipe is manufactured by cold-forming a sheet of steel into a cylindrical shape. Current is then passed between the two edges of the steel to heat the steel to a point at which the edges are forced together to form a bond without the use of welding filler material. Initially this manufacturing process used low frequency AC current to heat the edges. This low frequency process was used from the s until . In , the low frequency process was superseded by a high frequency ERW process which produced a higher quality weld.

Over time, the welds of low frequency ERW pipe were found to be susceptible to selective seam corrosion, hook cracks, and inadequate bonding of the seams, so low frequency ERW is no longer used to manufacture pipe. The high frequency process is still being used to manufacture pipe for use in new pipeline construction.[4]

Other methods

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Other ERW methods include flash welding, resistance projection welding, and upset welding.[5]

Flash welding is a type of resistance welding that does not use any filler metals. The pieces of metal to be welded are set apart at a predetermined distance based on material thickness, material composition, and desired properties of the finished weld. Current is applied to the metal, and the gap between the two pieces creates resistance and produces the arc required to melt the metal. Once the pieces of metal reach the proper temperature, they are pressed together, effectively forge welding them together.[6]

Projection welding is a modification of spot welding in which the weld is localized by means of raised sections, or projections, on one or both of the workpieces to be joined. Heat is concentrated at the projections, which permits the welding of heavier sections or the closer spacing of welds. The projections can also serve as a means of positioning the workpieces. Projection welding is often used to weld studs, nuts, and other threaded machine parts to metal plate. It is also frequently used to join crossed wires and bars. This is another high-production process, and multiple projection welds can be arranged by suitable designing and jigging.[7]

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See also

[edit]

• List of welding processes
• Shot welding

References

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Bibliography

[edit]

• Weman, Klas (), Welding processes handbook, CRC Press, ISBN 0---8.

Further reading

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• O'Brien, R.L. (Ed.) (). Welding Handbook Vol. 2 (8th ed.). Miami: American Welding Society. ISBN 0--354-3