Welded pipe, also known as welded steel pipe, is basically made of steel plate or strip welded after decoiling and forming. Welded steel pipe has the advantages of simple production process, high production efficiency, more varieties and specifications, and less equipment investment, but its general strength is lower than that of seamless steel pipe. Since the 1930s, with the rapid development of high-quality strip rolling production and the progress of welding technology and inspection technology, the quality of welded seam has been continuously improved, the variety and specification of welded steel pipe has been increasing, and seamless steel pipe has been replaced in more and more fields. Welded steel pipes are divided into straight seam welded pipe and spiral welded pipe according to the form of weld.

一.Classification of Welded Pipes Welded tubes

Welded pipes are classified according to their usages: they are also classified into general welded pipes, galvanizing welded pipes, oxygen blowing welded pipes, wire sleeves, metric welded pipes, idler pipes, deep well pump pipes, automobile pipes, transformer pipes, welded thin-walled pipes, welded abnormal pipes and spiral welded pipes.

二.Application Range of Welded Pipe

Welded pipe products are widely used in boiler, automobile, ship building, building light-weight structural doors and windows steel, furniture, a variety of agricultural machinery, scaffolding, wire threading pipe, high-rise shelves, containers and so on by which these can meet customer’s requirements, special abnormal welded pipe can be manufactured according to user’s requirements.

三.THEORETICAL CALCULATION METHOD OF WELDED PIPE WEIGHT   

There are formulas for calculating the weight of welded pipe.

Theoretical weight per meter of steel pipe (density of steel is 7.85 kg/dm3)

Formula: W = 0.02466 (D-S)S

In the calculation formula, the theoretical weight of W-steel pipe per meter, kg/m;

D – Nominal outer diameter of steel pipe, mm;

S – nominal wall thickness of steel pipe, mm.

四.Official Definition and Industrial Use of Welded Pipe

The raw materials used on welded tube mill is steel plate or the steel strip. It can be divided into furnace welded pipe, electric welded pipe and automatic arc welded pipe because of different welding technology. According to the different welding forms, it can be divided into straight seam welded pipe and spiral welded pipe.per the end shape, it can be divided into round welded pipe and special-shaped welded pipe (square pipe flat pipe etc.) . Welded pipes can be divided into the following categories per the their different materials and uses:

1. GB/T3091-1993 (Galvanized Welded Steel Pipe for Low Pressure Fluid Conveyance)

Mainly used for conveying water, gas, air, oil, heating hot water or steam and other general low pressure fluids and other purpose pipes. Its representative material is grade Q235A steel.

2. GB/T3092-1993 (Galvanized Welded Steel Pipe for Low Pressure Fluid Conveyance)

Mainly used for conveying water, gas, air, oil, heating hot water or steam and other general low pressure fluids and other purpose pipes. Its representative material is Q235A grade steel.

3. GB/T 14291-1992 (Welded Pipe for Mine Fluid Transport)

Mainly used for mine air pressure, drainage, shaft gas drainage with straight seam welded steel pipe. Its representative material is grade Q235A and B steel. GB/T 14980-1994 (Large Diameter Welded Steel Pipe for Low Pressure Fluid Conveyance). It is mainly used for conveying low pressure fluids such as water, sewage, gas, air, heating steam and other purposes. Its representative material is grade Q235A steel.

4. GB/T12770-1991 (Welded stainless steel pipe for mechanical structure)

Mainly used for machinery, automobiles, bicycles, furniture, Hotel and hotel decoration and other mechanical parts and structural parts. Its representative materials are 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb, etc.

GB/T12771-1991 (Welded Stainless Steel Pipe for Fluid Transport)

Mainly used for conveying low-pressure corrosive media.

The representative materials are 0Cr13, 0Cr19Ni9, 00Cr19Ni11, 00Cr17, 0Cr18Ni11Nb, 0017Cr17Ni14Mo2, etc.