Introduction to welded pipe

The blank of welded steel pipe is steel plate or strip steel. The welded pipe is divided into GB / t3091-2008, GB / t14291-2006, GB / t12770-2002 and GB / t12771-1991 due to its different materials and uses. The welded pipe is divided into general welded pipe, galvanized welded pipe, oxygen blowing welded pipe, wire sleeve, metric welded pipe, idler pipe, deep well pump pipe, automobile pipe, transformer pipe, electric welding thin-walled pipe, electric welding special-shaped pipe Scaffold pipe and spiral welded pipe.. Welded pipe has the advantages of simple production process, high production efficiency, low cost and rapid development. Welded steel pipe is often used to transport fluid and powdery solids and exchange heat energy. It is also an economic steel. Using steel pipes to make building structure grid, pillars and mechanical supports can reduce weight, save metal by 20-40% and improve construction speed.

Welded pipe product standard

Common materials of welded pipes are: Q235A, Q235C, Q235B, 16Mn, 20#, Q345, L245, L290, X42, X46, X60, X80, 0Cr13, 1Cr17, 00cr19ni11, 1Cr18Ni9, 0cr18ni11nb, etc.

Welded pipes are classified according to their materials and uses:

• GB / t3091-2008 (welded steel pipe for low pressure fluid transmission): it is mainly used to transport water, gas, air, oil, heating hot water or steam and other general low pressure fluids and pipes for other purposes. Its representative material is Q235 grade a steel.

• GB / t14291-2006 (welded steel pipe for mining fluid transportation): it is mainly used for straight seam welded steel pipe for mine air pressure, drainage and shaft gas drainage. Its representative material is grade Q235A and B steel.

• GB / t12770-2002 (stainless steel welded steel pipe for mechanical structure): mainly used for machinery, automobile, bicycle, furniture, hotel and restaurant decoration and other mechanical parts and structural parts. Its representative materials are 0Cr13, 1Cr17, 00cr19ni11, 1Cr18Ni9, 0cr18ni11nb, etc.

• GB / t12771-1991 (stainless steel welded steel pipe for fluid transportation): it is mainly used to transport low-pressure corrosive media. The representative materials are 0Cr13, 0Cr19Ni9, 00cr19ni11, 00Cr17, 0cr18ni11nb, 0017cr17ni14mo2, etc.

In addition, welded stainless steel pipes for decoration (GB / T 18705-2002), welded stainless steel pipes for architectural decoration (JG / T 3030-1995), and welded steel pipes for heat exchangers (yb4103-2000).

Welded pipes are classified by purpose

It is also divided into general welded pipe, galvanized welded pipe, oxygen blowing welded pipe, wire sleeve, metric welded pipe, idler pipe, deep well pump pipe, automobile pipe, transformer pipe, electric welding thin-wall pipe, electric welding special-shaped pipe, scaffold pipe and spiral welded pipe.

• General welded pipe: General welded pipe is used to transport low-pressure fluid. It is made of q195a, q215a and Q235A steel. It can also be made of other mild steel that is easy to weld. Water pressure, bending, flattening and other tests shall be carried out for steel pipes, and there are certain requirements for surface quality. Generally, the delivery length is 4-10m, and fixed length (or double length) delivery is often required. The specification of welded pipe is expressed in nominal diameter (mm or inch). The nominal diameter is different from the actual. Welded pipe can be divided into ordinary steel pipe and thickened steel pipe according to the specified wall thickness, and steel pipe can be divided into threaded and non threaded according to the form of pipe end.

• Galvanized steel pipe: in order to improve the corrosion resistance of steel pipe, general steel pipe (black pipe) is galvanized. Galvanized steel pipes are divided into hot-dip galvanizing and electro galvanizing. The hot-dip galvanizing layer is thick and the cost of electro galvanizing is low.

• Oxygen blowing welded pipe: it is used as the pipe for oxygen blowing in steelmaking. Generally, small-diameter welded steel pipe is used, with eight specifications ranging from 3 / 8 inch to 2 inch. Made of 08, 10, 15, 20 or q195-q235 steel strip. In order to prevent corrosion, some are aluminized.

• Wire sleeve: that is, ordinary carbon steel welded steel pipe, which is used in concrete and various structural power distribution projects. The commonly used nominal diameter is from 13-76mm. The wall of wire sleeve is thin, and it is mostly used after coating or galvanizing. Cold bending test is required.

• Metric welded pipe: the specification is used as the form of seamless pipe. The welded steel pipe expressed by outer diameter * wall thickness mm is welded with the tropical and cold strip of ordinary carbon steel, high-quality carbon steel or Puneng low alloy steel, or it is made by the cold drawing method after tropical welding. Metric welded pipe is generally used as structural parts, such as transmission shaft or conveying fluid. The thin wall is used to produce furniture and lamps. The strength and bending test of steel pipe shall be ensured.

• Idler pipe: it is used for electric welding steel pipe of belt conveyor idler. It is generally made of Q215, Q235A, B steel and 20 steel, with a diameter of 63.5-219.0mm. There are certain requirements for the bending degree, end face perpendicular to the centerline and ovality of the pipe. Generally, hydraulic pressure and flattening test are carried out.

• Transformer tube: it is used to manufacture transformer heat dissipation tube and other heat exchangers. It is made of ordinary carbon steel and requires flattening, flaring, bending and hydraulic test. Steel pipes are delivered in fixed length or multiple length, and there are certain requirements for the bending of steel pipes.

• Special shaped pipe: square pipe, rectangular pipe, cap pipe and steel pipe for hollow rubber steel doors and windows welded by ordinary carbon structure steel and 16Mn steel strip. It is mainly used as agricultural machinery components, steel windows and doors, etc.

• Welded thin-walled tube: mainly used for making furniture, toys, lamps, etc. In recent years, thin-walled tubes made of stainless steel strip are widely used, such as high-grade furniture, decoration, fence and so on.

• Spiral welded pipe: it is made by rolling low-carbon structural steel or low-alloy structural steel strip into pipe blank according to a certain angle of spiral line (called forming angle), and then welding the pipe seam. It can produce large-diameter steel pipe with narrow strip steel. Spiral welded pipe is mainly used for oil and natural gas transmission pipeline, and its specification is expressed by outer diameter * wall thickness. Spiral welded pipe can be welded on one side and on both sides. The welded pipe shall ensure that the hydrostatic test, tensile strength and cold bending performance of the weld meet the requirements.

Welded pipes are classified according to section shape

(1) Simple section steel pipe -- circular steel pipe, square steel pipe, oval steel pipe, triangular steel pipe, hexagonal steel pipe, rhombic steel pipe, octagonal steel pipe, semicircular steel pipe, others.

(2) Steel pipes with complex section -- unequal hexagonal steel pipes, five petal quincunx steel pipes, double convex steel pipes, double concave steel pipes, melon seed steel pipes, conical steel pipes, corrugated steel pipes, watch case steel pipes and others

Process flow of welded pipe

Uncoiling of raw materials - leveling - end shearing and welding - looper - forming - Welding - internal and external weld bead removal - pre correction - induction heat treatment - sizing and straightening - eddy current testing - cutting - hydraulic inspection - Pickling - final inspection (strict control) - Packaging - shipment.