How to buy welded steel pipes?

The welded refers to a which is welded and formed into a shape of a circle or a square by bending a steel strip or a steel plate, and has a seam on the surface thereof. The raw material used for the welded is a steel plate or a strip steel.

Welded Tube and Pipe Manufacturing Processes

Steel pipes are made by two different processes. The overall production method for both processes involves three steps.

First, raw steel is converted into a more workable form. Next, the pipe is formed on a continuous or semicontinuous production line. Finally, the pipe is cut and modified to meet the customer’s needs.

Ends of pipes

Ends of Pipes

For the ends of pipes are 3 standard versions available.

  • Plain Ends (PE)
  • Threaded Ends (TE)
  • Beveled Ends (BE)

The PE pipes will generally be used for the smaller diameters pipe systems and in combination with Slip On flanges and Socket Weld fittings and flanges.

The TE implementation speaks for itself, this performance will generally used for small diameters pipe systems, and the connections will be made with threaded flanges and threaded fittings.

Root faceThe BE implementation is applied to all diameters of buttweld flanges or buttweld fittings, and will be directly welded (with a small gap 3-4 mm) to each other or to the pipe.

Ends are mostly be beveled to angle 30° (+ 5° / -0°) with a root face of 1.6 mm (± 0.8 mm).

Length of Pipes

Piping lengths from the factory not exactly cut to length but are normally delivered as:

  • Single random length has a length of around 5-7 meter
  • Double random length has a length of around 11-13 meter
  • Shorter and longer lengths are available, but for a calculation, it is wise, to use this standard lengths;
  • other sizes are probably more expensive.
  • Packed in wooden crates, wrapped in plastic, and suitably protected for sea-worthly delivery or as requested.
  • Both ends of each crate will indicate the order no., heat no., dimensions, weight and bundles or as requested.

Pipes are supplied in hexagonal bundles or round bundles tied with steel strip.
Weight of bundle – up to 5000 kg upon request of customer.
Each bundle is furnished with three tags.

Pipe cutting


The length of the pipe cut according to the requirement. Cutting tools have a grinding wheel piece cutting machine (also known as toothless saw), hand saw, cutter and other hand tools.

Grinding wheel piece cutting machine: is suitable for cutting metal pipes or metal profiles, especially bulk cutting processing is the most economic. Pipe cutting length you need should be determined before and draw a good cutting line. Pipe cutting machine before cutting jig should be fixed firmly. Machine starts, press the grinding wheel slowly, not slam the rapid or too much pressure, so as not to burst grinding wheel accidents.

saw blade teeth should point to the thrust direction, saw blade to tighten, not wobble. Operation when the pressure pipe clamp fixed on the console (console height was about lm), then firmly push and pull, can one man operation, but also the two with the operation. To prevent heat and maintain lubrication can be made to Jukou drip oil. No matter use mechanical or hand according to the cutting all rong or feathered a cut section level off is smooth. Research may not be in slit fold truncation.

is the use of rollers with a sharp knife, make 3600 the card on the pipe rotation, tighten the top wire while rotating the hob until it gradually into the top pipe cut off. In this way cutting metal pipe, the pipe will tilt tube wall, not only reduces the tube diameter, also make the pipe wall is not smooth, damage to the conductor. Under normal circumstances should not be taken in cutting metal pipes. When used, if necessary, must be cut diameter steel pipe with a round file file level, so that the pipe diameter and the diameter of the same incision.

Pipe connection

Pipe connection is varied, the commonly used have Butt weld, Flanged, Threaded, Socket weld, Glued, Brazed and Grooved end.

You assign connection types in the Connector Properties dialog box as you build fittings content using the Content Builder (see Adding Connectors to a Parametric Fitting). Assigned connection types are then displayed on the Connection Assignments tab of the Pipe Layout Preferences dialog box.

Unthreaded Connections are not threaded, must be either welded or bolted together. The following table shows the different orientations of pipe connection types:

Butt weld:

A butt weld is two pipes lined up with one another and welded along the contact edge to create a seal.

Butt weld
No extra objects are added.

Fittings and pipe segments connect directly to each other.

Flanged All types

A flange is a plate or ring that is attached to a pipe. Two flanged pipe then create a tight seal by being bolted together.


  • Fitting to pipe: Flanges are typically included on fittings. A separate flange is added to the pipe segment.
  • Pipe to pipe: A separate flange is added to each pipe end to create the connection.
  • Fitting to fitting: Fittings with inherent flanges connect directly to each other. No separate flanges are added to the connection.

Threaded, Socket weld, Glued, Brazed

The pipe is the male fitting and the socket is equivalent to a female fitting. To provide a tight seal it is best to line the outside of the pipe and the inside of the socket with a sealant.

Socket welds require a pipe and socket connection.

  • Fitting to pipe: Pipe segments typically have inherent male ends, and fittings are typically female. The pipe inserts directly into the fitting.
  • Pipe to pipe: A female coupling is inserted between the pipe segments.
  • Fitting to fitting: Fittings connect directly to each other.

Grooved end

A grooved end fitting has a groove or shoulder along the edge. This fittings groove allows for a seal without the need for welding.


  • Fitting to pipe: Fittings and pipe segments are considered to have grooved ends that are ready to accept a coupling. A coupling is added to connect the fitting and pipe.
  • Pipe to pipe: A coupling is added to connect the pipe segments.
  • Fitting to fitting: A coupling is added to connect fittings.

Weld cold crack

Welded joints cooled to a lower temperature ( for steel, in the martensitic transformation start temperature Ms less ) generated by the weld cracking.

Commonly known as cold cracking, which is divided into delayed cracking, thermal stress cracking and lamellar tearing three kinds. Cold cracks sometimes appear immediately after welding, but sometimes after a few hours, days, or even longer to appear. These weld after a period of time before the emergence of crack called delayed cracking. Delayed cracking in the manufacturing process may not be found, and in the process of using it may cause extremely serious consequences. So it is more harmful than crack.

Judging from the cold crack forms have the following types: boundary cracks, under-bead cracks and root cracks. Boundary cracks from weld and base metal junction began to extend the base material. Under-bead cracks in the weld seam below the near area, not developed to the base metal surface. Cracks form originated in the root of the weld notch stress concentration at the heat affected zone, which extends into the base metal or welds.

Cold crack causes are analyzed as follows:
1, the role of hydrogen
In the welding temperature, some of the hydrogen atoms in the compound of the state of the precipitation of hydrogen resolution, large amount of hydrogen dissolved in the metal bath. As the bath temperature dropped, the solubility of hydrogen in the metal drastically reduced. However, quickly cooling of the weld pool, the hydrogen too late to escape and remains in the weld metal. Hydrogen in austenite and ferrite in the solubility and diffusion capacity are also significant differences.

2, quenching effect
Near the weld seam zone or cold cracks formed on the metal phase transition process and the mechanical properties of rapidly changing and complex stress state. Cold cracking occurs mainly in , high carbon steel and high strength steel. The main features of this type of steel is easy to quenching, the austenite serious overheating , the grains grow significantly. Learn from metal shows that the austenite grain coarsening easier quenched into coarse martensite, the performance deterioration of metal near the weld area, especially the plastic drop fragility. At this time in the role of complex welding stress occurs under cold cracking.

Usually the carbon equivalent of the weld metal is lower than the base material, and thus the weld occurs at a higher temperature austenite decomposition, then near the weld area has not yet occurred austenite. Since the solubility of hydrogen in the weld metal sudden drop. As the temperature decreased, near the weld region of austenite transformation, the temperature has very low solubility of hydrogen lower and has very weak diffusion. So then with hydrogen gas state into the fine pores of the metal and cause a lot of pressure, so that the local metal with great stress, and thus the formation of cold cracks.

Arc welding

SAW pipes
Submerged arc welding (SAW) is a common arc welding process.

Arc welding refers to arc supply heating energy, so that the workpiece to fuse together to achieve atomic indirect co-welding method. Arc welded is the most widely used welding method.

According to the statistics of the number of industrial countries, arc welding in the welding of total production in the proportion is generally above 60%.

The arc welding joints, with or without filler metal. When the electrodes used for the welding process, the molten wire, called the MIG arc welding, such as SMAW, submerged arc welding, gas shielded protect welding, tubular wire arc welding; with basic welding electrodes for welding process carbide or tungsten rod does not melt, called MIG arc welding, such as gas tungsten arc welding, plasma arc welding.

Depending on the characteristics of the process, the arc welding can be divided into electrode arc welding, submerged arc welding, gas shielded arc welding and plasma arc welding and so on.

Classification of arc welding

Arc welded can be divided into the three kinds of manual metal arc welding, submerged arc welding and gas shielded arc welding.

The biggest advantage of the hand-automatic welding equipment is simple, flexible, convenient, and applicable to a wide range of welding a variety of welding positions and straight seam girth and the various curves weld. Particularly suitable for operating the same occasion and short weld welding; automatic submerged arc welding with high productivity, weld quality is good, and good working conditions; gas shielded arc welding has a protective effect, stable arc, the heat concentrated.

ERW pipe technical requirements

 ERW pipes means Electric Resistance Welded Pipes

ERW pipes means . ERW steel pipes and tubes are used.

ERW steel pipes and tube are available in various qualities, wall thicknesses, and diameters of the finished pipes.

Technical requirements For oil and gas transport For low pressure fluid conveying
Material Gr.b Gr.b
Pipe body diameter D<508mm, ±0.75%; D≥508mm, ±0.75% D≤168.3, ±1.0%;  168.3<D≤508,±0.75%;
Wall thickness D<508mm,+15.0%,-12.5%; D≥508mm, +17.5%,-10% ±12.5%
Bending ≤0.2% ≤0.2%
Ovality D≥508mm,≤±1% ≤±0.75%
Bevel ≤1.59mm ≤5mm
Hydrostatic testing 100% 100%
Nondestructive testing 100% non-destructive weld inspection Ultrasonic flaw detection is 100%

ERW pipe technical requirements

ERW steel pipes and tubes are used in various engineering purposes, fencing, scaffolding, line pipes etc.

  • Yield strength of the N80 is higher than the J55 up to 173 ~ 206 MPa.
  • On the same area of ​​the sample, the elongation of N80 is higher than J55.
  • Under the same size, the same sample orientation, the same minimum sample size, J55 grade couplings, coupling stock, coupling material, semi-finished and coupling attachment material can absorb lower than N80 steel grade.
  • The nondestructive testing methods of seamless pipe,coupling stock, welded tube with J55 and N80 is differeent.
  • J55 and N80 steel grade is not the same color: length greater than or equal 1.8m, J55 painted a bright green, N80 painted a red;
  • J55 chosen by the manufacturer, or organize according to the order specified length normalized (N), normalizing and tempering (N & T) or quenching and tempering (Q & T). N80 is a whole, full-length heat treatment is mandatory. By the manufacturer selected for normalizing (N) or normalizing and tempering (N & T) + quenching (Q).

Spiral submerged arc welding

Spiral submerged arc welding as raw material is often warm extrusion molding, automatic double -sided wire submerged arc welding process.

The process is normally limited to the flat or horizontal-fillet welding positions (although horizontal groove position welds have been done with a special arrangement to support the flux).

Spiral submerged arc welding process performance:

(1) raw that strip, wire, flux. Must go through rigorous testing before being put into the physical and chemical.
(2) strip head and tail docking, using single or double wire submerged arc welding, in rolled steel by automatic submerged arc welding.
(3) Before molding, the strip after flattening, cutting, trimming, planing, surface cleaning and transportation to the curved edge treatment.
(4) the use of electrical contacts on both sides of the conveyor control the pressure cylinder pressure to ensure the smooth delivery of the strip.
(5) the use of internal or external control roll forming.
(6) the weld gap control device to ensure that the weld gap to meet the welding requirements, diameter, volume and the wrong side of the weld gap have been strictly controlled.
(7) the welding and soldering are used outside the United States Lincoln welding machine for single or double wire submerged arc welding, to obtain stable welding specifications.
(8) After welding the weld line continuous ultrasonic injury checked to ensure 100% coverage of non-destructive testing of spiral weld. If defective, automatic alarm and spraying tags, production workers so adjusting the process parameters, and remove defects.
(9) the use of air plasma cutting machine to cut a single tube.
(10) cut into a single pipe, the first three of each batch of steel to carry out strict inspection system, inspection of weld mechanical properties, chemical composition, fusion status, steel surface quality and after NDT inspection to ensure that the process pipe after passing to formally put into production.
(11) there is a continuous sonic flaw marks the site of the weld, manual ultrasonic and X-ray review, if there are defects after repair again after destructive testing until confirmation defect has been eliminated.
(12) strip on the spiral weld seam and intersects with D-type connector where the pipe all through the X -ray television or film examination.
(13) each pipe hydrostatic test pressure radial seal. Test pressure steel pipe pressure and time by computer testing device strictly controlled. Test parameters are automatically printed record.
(14) pipe end machining, so that the end vertical, blunt edge bevel and accurate control.

Typical ERW Pipe Manufacturing Process

Our manufacturing process generally involves the following stages in a step by step procedure.

ERW Pipe Manufacturing process


HR Coils are slitted to pre-determined widths for each and every size of pipes

Round forming
Round forming
Uncoiling, End Shearing And Welding

The slitted coil is uncoiled at the entry of ERW mill and the ends are sheared and welded one after another. This results in a single endless strip.


The slitted coils are initially formed into U shape and after that into a cylindrical shape with open edges utilizing a series of forming rolls.


In this stage, the open edges are heated to the forging temperature through high-frequency, low-voltage, high current and press welded by forge rolls making perfect and strong but weld without filler materials.

De beading

In this stage, the weld flash on top and inside (if required) is trimmed out using the carbide tools.

Seam Annealing

If required, the welding portion and heat affected zone is put to normalizing and then are cooled down in a air cooling bed.


After water quenching, slight reduction is applied to pipes with sizing rolls.

This results in producing desired accurate outside diameter.


In cutting stage, the pipes are cut to required lengths by flying cut off disc/saw cutter.

End Facing And Bevelling

This is usually stage, where the pipes ends are faced and bevelled by the end facer.

All these processes are continuous with automatic arrangements. These plain ended tubes further go for processing as per the customer requirements such as galvanizing, threading, black varnishing and more.

What Is Black Steel Pipe?

ASTM A500 Black steel pipe

Black steel pipe is made of steel that has not been galvanized. Its name comes from the scaly, dark-colored iron oxide coating on its surface. It’s used in applications that don’t require galvanized steel.

They connected by screwing onto the threaded pipe, after applying a small amount of pipe joint compound on the threads. Larger diameter pipe is welded on rather than threaded. Black steel pipe is cut either with a heavy-duty tube cutter, cut-off saw or by a hacksaw. You can also get Mild Steel ERW Black Pipes that are extensively used for gas distribution inside & outside of the home, and for hot water circulation in boiler systems. Can also be used in usage in potable water or drains waste or vent lines. Please browse our construction pipe and tube directory for a supplier to meet your needs.

William Murdock made the breakthrough leading to the modern process of pipe welding. In 1815 he invented a coal burning lamp system and wanted to make it available to all of London. Using barrels from discarded muskets he formed a continuous pipe delivering the coal gas to the lamps. In 1824 James Russell patented a method for making metal tubes that was fast and inexpensive. He joined the ends of flat iron pieces together to make a tube then welded the joints with heat. In 1825 Comelius Whitehouse developed the “butt-weld” process, the basis for modern pipe making.

Pipe welder
Whitehouse’s method was improved upon in 1911 by John Moon. His technique allowed manufacturers to create continuous streams of pipe. He built machinery that employed his technique and many manufacturing plants adopted it. Then the need arose for seamless metal pipes. Seamless pipe was initially formed by drilling a hole through the center of a cylinder. However, it was difficult to drill holes with the precision needed to ensure uniformity in wall thickness. An 1888 improvement allowed for greater efficiency by casting the billet around a fire-proof brick core. After cooling, the brick was removed, leaving a hole in the middle.

Black steel pipe’s strength makes it ideal for transporting water and gas in rural and urban areas and for conduits that protect electrical wiring and for delivering high pressure steam and air. The oil and petroleum industries use black steel pipe for moving large quantities of oil through remote areas. This is beneficial, since black steel pipe requires very little maintenance. Other uses for black steel pipes include gas distribution inside and outside homes, water wells and sewage systems. Black steel pipes are never used for transporting potable water.

Modern Techniques
Scientific advancement has greatly improved on the butt-weld method of pipe making invented by Whitehouse. His technique is still the primary method used in making pipes, but modern manufacturing equipment that can produce extremely high temperatures and pressure has made pipe making far more efficient. Depending upon its diameter, some processes can produce welded seam pipe at the incredible rate of 1,100 feet per minute. Along with this tremendous increase in the rate of production of steel pipes came improvements in the quality of the final product.

Quality Control
The development of modern manufacturing equipment and inventions in electronics allowed for marked increases in efficiency and quality control. Modern manufacturers employ special X-ray gauges to ensure uniformity in wall thickness. The strength of the pipe is tested with a machine that fills the pipe with water under high pressure to make sure the pipe holds. Pipes that fail are scrapped. The details about schedule 80 black steel pipe

Type schedule 80 balck steel pipe
Size 1/2〞-32〞
Wall thickness sch5-sch160xxs
Standard ASME B36.10M-1996 ,API ,ANSI ,GB, SH,HG, MSS,JIS,DIN
Material ASTM A106 GRB/ A53 GRB/ API 5L GRB/ API 5 CT /Q345/A335/ST37/ST52
Certification ISO and SGS certificate
Package painting black, pipe cap, steel strips bundled.
Application range petroleum, construction ,shipbuilding,smelting, aviation, power, foodstuff, papermaking, chemical, medical equipment, boiler heat, exchanger, gas metallurgy, etc.

(steel pipe manufactured with a weld) is a tubular product made out of flat plates, known as skelp, that are formed, bent and prepared for welding.

Welding steel tube is one pipe the surface has the steel pipe joint,which is use the steel belt or steel plate material through the bending deformation into round ,square ect then welded into shape.

Welded steel tube products are widely used in boilers, automobiles, ship building lightweight structural steel of the doors and windows, furniture, agricultural machinery, scaffolding, wire conduit, top shelves, containers, etc.. which can meet customer requirements, the special specifications welded pipe can be processed according to user requirements. Welded pipes for conveying water, sewage, gas, air, heating, steam and other low-pressure fluid and other uses.

Welded pipes by manufacturing process:

Sunny Steel produce an extensive selection of welded steel pipe including ERWHFIEFWLSAWDSAW and UOE type carbon steel pipe along with their respective flanges and fittings.

  • ERW pipes– A plate rolled to become a pipe and welded using Electric Resistance Welding process.
 High frequency welding, HFI pipe

In High Frequency Induction (HFI) Welded Pipe production process, hot rolled steel coils are fed with a high capacity accumulator in order to achieve continuous welding.

  • (HFI) High frequency welded pipe– HIGH-FREQUENCY WELDING is a welding process in which the heat source used to melt the joining surfaces is obtained from high-frequency (HF) alternating current (ac) resistance heating.

Electric Fusion Welded Pipes

The EFW pipe divison consists of a JCO forming press, helical / spiral mill, inside and outside welding system, heat treatment furnace and testing facilities.

The EFW pipe divison consists of a JCO forming press, helical / spiral mill, inside and outside welding system, heat treatment furnace and testing facilities. Welding process employed is gtaw for root-pass and saw/tig for final pass with suitable filler wires as prescribed by aws specifications and asme boiler and pressure vessel code, section-ix. These facilities are capable of manufacturing austenitic and various duplex grades.

  • (EFW) Electric Fusion Welded Pipe– The EFW pipe divison consists of a JCO forming press, helical / spiral mill, inside and outside welding system, heat treatment furnace and testing facilities.
Range of Oil & Gas pipeline pipes:

Material: As per API 5L, the steel grade covers X80 and lower


  • Outer diameter: Ф406-1524mm
  • Wall thickness: 6-40mm
  • Unit length: 8-12.1m
Welded pipes by matarial:
Mill Test Certificate: EN 10204/3.1B 
Third party inspection: SGS, BV, Lloyds etc.
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