Welded steel pipe

Welded steel pipes are seam steel pipes made of steel plates or steel strips that are crimped and welded. They have the advantages of small size deviation, uniform wall thickness, ordinary production process, high production efficiency, many varieties and specifications, and low equipment investment.

Welded steel pipes are divided into spiral welded pipes and straight-seam welded pipes according to the weld shape. Spiral welded pipes generally use submerged arc welding, and longitudinally welded pipes generally use submerged arc welding or high-frequency resistance welding.

Welded steel pipe specification

StandardGB, ASTM, bs, JIS, GB/T 3091-2001, GB 9948-2006, A53 ,BS1387-1985
Thickness 0.5-40 mm
OD 12-2620 mm
LengthCommon length: 5.8m,6m,11.8m,12m
Surface treatmentBared, black painted (varnish coating), Oiled, Galvanized, corrosion resistant coating, anti corrosion coating
ApplicationConstruction, drill, fluid transport, transmission of gas, water, petroleum.

Welded steel pipe standard

Welded steel pipe
ModelNominal diameterOutside diameter (mm)Wall thickness (mm)Theoretical weight (kg/m)

Welded steel pipe Production Process

Welded steel pipes are seam steel pipes, and their production is to bend the tube billet (steel plate and steel strip) into a tube of the required cross-sectional shape and size by various forming methods, and then use different welding methods to weld the welds together.

The process of obtaining steel pipes: Raw material uncoiling → leveling → end shearing and welding → looping → shaping → welding → removal of inner and outer bead → precorrection → induction heat treatment → sizing and straightening → eddy current testing → cutting → water pressure inspection → pickling → final inspection (strict control)→ packaging → shipment.

Types of welded steel pipe 

Welded pipe

  1. According to process: arc welded pipe, resistance welded pipe (high frequency, low frequency), gas welded pipe, furnace welded pipe
  2. According to weld: straight seam welded pipe, spiral welded pipe

Seamless steel pipe vs welded steel pipe

Seamless steel pipes are made of steel ingots or solid tube billets through the perforation into capillary tubes and then made by cold drawing, cold rolling, or hot rolling. The seamless steel pipe is long steel with a hollow section and no joints on the periphery.

Welded steel pipes can be divided into spiral welded pipes and straight-seam welded pipes according to the mode of welds. They are steel pipes made by welding steel plates or steel strips after crimping. LSAW has a simple production process, high output efficiency, rapid development, and low cost. The strength of the SSAW pipe is usually higher than the LSAW pipe.

To distinguish a welded steel pipe from a seamless steel pipe, the existence of weld can be tested by the corrosion method and metallographic method. Submerged arc welded steel pipe needs welding material, so its welding seam is wide and can be inspected by the corrosion method. High frequency welded steel tube does not need weld filler, and the welding heat affected zone is narrow. When the welding seam cannot be accurately identified by a simple corrosion method, the microstructure can be observed by the metallographic method for resolution.

Carbon steel pipe vs welded steel pipe

Carbon steel tubes are divided into hot rolled and cold rolled (drawn) steel pipes. The hot-rolled seamless pipe’s outer diameter is usually greater than 32mm, the thickness of the wall is 2.5-75mm, the cold-rolled seamless pipe’s outer diameter can reach 6mm, the thickness of the wall can be 0.25mm, the outer diameter of the thin-walled pipe can reach 5mm, the thickness of the wall is less than 0.25mm, and the dimension precision of cold rolling is higher than that of hot rolling.

According to the welding process, welded steel pipes are divided into three types: continuous furnace welded steel pipe, electric resistance welded steel pipe and electric arc welded steel pipe. Continuous furnace welded steel pipes are welded together by mechanically pressurizing steel strips after heating and forming in a heating furnace to form welded steel pipes with straight seams. Electric resistance welded steel pipes are seamed steel pipes produced by electric resistance welding or electric induction welding. Arc welded steel pipes are steel pipes produced by arc welding methods.

Black steel pipe vs welded steel pipe

The black steel pipe contains a dark iron oxide coating on its entire surface for use without electroplating maintenance. Because of its high heat resistance, it is generally used in fire sprinkler systems.

Black steel pipes are also very popular in other water transportation applications, including domestic water and natural gas pipelines from wells.

The black steel pipe is one of the most common steel tubes. In order to increase the corrosion resistance of steel, the steel surface is blackened with agents. Its surface has not been polished so it is black.

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