Longitudinal Pipe

Longitudinal Pipe is a Steel Pipe, weld steel pipe means parallel to the longitudinal pipe. Classified by the wall thickness of thin-walled and thick-walled straight seam pipe straight seam pipe; according to shape classification round pipe, square shaped tube or pipe; there are generally classified by use pipe, galvanized pipe, oxygen blowing pipe, wire casing, metric pipe, roller tube, deep well pump tube, automotive tube, transformer tube, welding thin-walled tube, welding shaped tube and spiral welded pipe.Straight tube refers to weld and pipe longitudinal parallel. Generally known as welded pipe or pipe. The Straight Pipe is through the high frequency welding strip steel coiling unit will be of certain specifications and with longitudinal welded. Straight pipe specifications with nominal diameter, the wall thickness can be divided into thin-walled straight tube and a thick wall straight seam pipe two. According to the shape can be divided into round, square or shaped tube, etc..

Classification of welded pipe materials and uses

GB/T3091-1993 (galvanized Welded Steel Pipe for low pressure fluid delivery). Mainly used for conveying water, gas, air, oil and heating hot water or steam and other generally low pressure fluid and other use pipe. Its representative material Q235 grade a steel.

GB/T3092-1993 (galvanized welded steel pipe for low pressure fluid delivery). Mainly used for conveying water, gas, air, oil and heating hot water or steam and other generally low pressure fluid and other use pipe. Its representative material is: Q235 grade a steel.

GB/T14291-1992 (mineral fluid transport welded steel pipe). Mainly used in mine air pressure, drainage, gas drainage shaft with a straight seam welded steel pipe. Its representative material B, Q235A grade steel. GB/T14980-1994 (large diameter welded steel pipe for low pressure fluid delivery). Mainly used for conveying water, sewage, gas, air, heating steam and other low pressure fluid and other purposes. Its representative material Q235 grade a steel.

GB/T12770-1991 (stainless steel welded pipe for mechanical structure). Mainly used in machinery, automobiles, bicycles, furniture, hotels and hotel decoration and other mechanical components and structural parts. Its representative material 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb, etc..

GB/T12771-1991 (fluid transport with stainless steel welded pipe). Mainly used for conveying low pressure corrosive medium. Representative material for 0Cr13, 0Cr19Ni9, 00Cr19Ni11, 00Cr17, 0Cr18Ni11Nb, 0017Cr17Ni14Mo2, etc..

Photo of our Longitudinal Pipe:

The straight tube is mainly used in tap water engineering, petrochemical industry, chemical industry, electric power industry, agriculture and city construction. For liquid conveying: water supply, drainage. Gas, steam and liquefied petroleum gas for gas transmission. Used as a pile driver, as a bridge; pier, road, building structure, etc..  

welding

Straight seam pipe generally high-frequency welding, high frequency welding is a kind of induction welding (or pressure contact welding), it does not need to weld filler, weld spatter, welding heat affected zone is narrow, beautiful welding molding, welding, the advantages of good mechanical performance, so in the production of steel by wide application. According to the principle of electromagnetic induction and the exchange charge in the conductor tends to skin effect and proximity effect and eddy current heat effect, the edge weld steel local heating to a molten state, through the roller extrusion, the butt weld the intergranular bonding, so as to achieve the purpose of seam welding, cooling after the formation of a strong straight seam welding.

Weld gap

Will strip into the welded pipe unit, by the multi-channel roller rolling, strip gradually rolled up, forming the opening gap circular tube billet, adjusting the extrusion roller pressure, weld gap control in 1 ~ 3mm, and the weld ends flush. If the gap is too large, resulting in a reduction in the proximity effect, the eddy heat is insufficient, the welding seam between the poor bonding and produce no fusion or cracking. Such as the gap is caused by proximity effect increases, large welding heat, resulting in weld burning, or weld by extrusion, rolling form the pit affecting weld surface quality.

welding temperature

Low carbon steel material, welding temperature control in 1250~1460 C, can meet the pipe wall thickness 3~5mm welding penetration requirements. Welding temperature is mainly controlled by adjusting the high frequency eddy current heat power and welding speed. When insufficient heat input by heating the weld edge is not up to the welding temperature, metal structure remains solid, the formation of fusion or incomplete penetration; when the heat input is too large, heating the weld edge over welding temperature, burn off or droplet, molten hole can be formed in the weld.

standard

Straight pipe generally use the GB/T3091-2001 and GB/T9711.1-1997 standard.

Texture of material

Straight seam pipe commonly used material Q235A and Q235B and 16Mn, 20#, Q345, L245 and L290, X42, X46, X70, X80, 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb.

Quality testing

According to the standard of GB/T3091-2001 "welding steel pipe for low pressure fluid delivery", the surface quality of the steel pipe should be smooth, and there are no defects such as folding, cracking, delamination and lap welding. Steel tube surface allow a slightly less than wall thick negative deviation from scratch, scratch, joint dislocation, burns and scar defects. Allow the weld thickness and welding reinforcement.

Straight pipe should be made mechanical performance test and flattening test, flaring test, and to meet the requirements. Steel pipe should be able to withstand a certain internal pressure, if necessary, 2.5Mpa pressure test, to maintain a minute without leakage. Eddy current testing is allowed to replace hydrostatic test.

Eddy current testing according to GB/T7735-2004 "eddy current testing method of steel tubes" standard implementation. Eddy current testing method is the probe is fixed on the machine frame, inspection and weld maintain 3 ~ 5mm distance, rely on the rapid movement of the steel tube on the weld of comprehensive scanning, detection signal by eddy current flaw detector, automatic processing and automatic sorting, to inspection. After the inspection, the welded pipe is cut off by the specified length, and is off the assembly line. The pipe ends shall be chamfering, marking, finished tube hexagon binding package factory.