LSAW Steel Pipe

 Nowadays, the surface of the welded tubes we use are required to be coated for corrosion protection. The common anticorrosion coatings for welded tubes are petroleum asphalt, epoxy coal tar asphalt, PE sheath and PE foam sheath, epoxy powder, coal tar enamel and three-layer composite structure. The more used pipe anti-corrosion methods are 3PE composite structure and single-layer powder epoxy resin. So do you know how the welded tube is anti-corrosion? 1)Coating anti-corrosion Coating anti-corrosion refers to the uniform, dense coating on the surface of the rusted metal tube to isolate it from various corrosive media. This method of corrosion protection is usually used for steel tubes. Coating anti-corrosion materials are brushed coatings, which are paints, but with special properties that act as isolators. These materials and structures have better dielectric properties, physical properties, chemical properties and temperature range. 2) Cold-wrap tape Cold-wrap tape has the advan...

　　High frequency straight seam welded steel pipe welding quality defects are cracks, welding, water leakage, scratches and so on. 　 　First, cracks 　　Fracture is the main defect of welded pipe , its manifestation can be by the usual cracks, local periodic cracks, irregular intermittent cracks. Some of the steel pipe after welding surface without cracks, but by the flattening, straightening or hydrostatic test cracks. Severe leakage will leak. There are many causes of cracks. Elimination of cracks is one of the most difficult problems in welding adjustment operations. 　 　Second, take the welding 　　Lap welding is the edge of the tube in the welding when the dislocation, although the curette can still see the traces of dislocation. 　　1) Molding quality is not good. Forming the edge of the tube is not usually appear on both sides of the usual lap welding, forming the edge of the wave and the drum package, the local small lap. 　　2) The production of thin-walled tube, the squeeze ...

　　API mild steel pipe is widely used in lots of industries. However, a lot of customers still don't know kinds of API steel pipe and their usage. Here we are instroduce you the detail of API steel pipe. 　　 API line steel pipe 　　API line steel pipe is the line pipe that meets the American Petroleum standard. Line pipe is used for transportation of oil, gas and water to the oil and gas industry enterprises. Ends of pipe include plain end, threaded end and socket end; their connections concludes end welding, coupling, socket connections. With the development of technology, API line steel pipe's range of applications is expanding gradually, especially in the large-diameter disaster. Coupled with the factor of cost, welded pipe have a dominant position in the field of line pipe, limiting development of stainless steel seamless line pipe. During 2004, production of seamless line pipe is about 400,000 t, ranging from X42 to X70. 　　API line steel pipe is divided into onshore line...

　　When steel yield to a certain extent, due to the internal grain rearrange and its ability to resist deformation increased, although deformation developed rapidly, but it can only be increased as the stress increased, until the stress reaches the maximum value. Thereafter, the ability of steel to resist deformation is significantly reduced, and the large plastic deformation occurs at the weakest point, here specimens sectional rapidly narrow, the phenomenon of necking until fracture. The maximum stress in the steel by pull before breakage. 　　Value (b point corresponding value) referred to as the ultimate strength or tensile strength. Strength limit yield limit is determined by experiment. During the tensile test, the stress reaches a certain value, although no longer increase even slightly, the strain of the test piece continues to grow, and produce significant plastic deformation, as if the material temporarily loses the ability to resist deformation, such the phenomenon known as m...

　　In the process of producing high frequency welded pipe, the manufacturer of welded pipe will encounter pipe surface damage, which is the main reason of guide roller and extrusion roll. 　　1, the scratch produced by the guide roller usually occurs on both sides of the high frequency welded pipe, and the scratch characteristics are large and continuous. The reasons include: 　　(1) the height of the guide sleeve is not correct, such as the damage of the guide roller bearing, the guide roller can not control the high frequency welding pipe well, so that the guide sleeve and friction lead to scratch. 　　(2) when the central roll of the guide roller deviates from the high frequency tube production line is too large, the difference between the guide sleeve and the guide roller axis is too large, resulting in scratches on both sides of the high-frequency welded pipe. 　　2. the scratches produced by the high frequency welding extrusion roller mainly occur at the bottom of the high-frequen...

　　 Transverse crack in the weld of thick-walled lsaw steel pipe 　　D36, D36-Z35 and S355 structural steel plates with thickness of 20~50mm are used respectively to produce marine experience exchanges through the JCOE forming method. The lsaw steel pipe of the 54.HAN GUAN welded pipe platform are 508~1372mm in diameter. The weld seam adopts X-shaped groove, the inner weld is three-wire submerged arc welding, and the outer welding is multi-layer multi-channel three-wire submerged arc welding. Ultrasonic testing of the weld was carried out after 24h or 48h of welding. Lateral scanning revealed that there were forest-like echoes in the middle of the weld wall thickness. Further testing found that sometimes the entire weld was intermittently with similar signals, and the depth was in the weld. centre position. In order to find out the nature of the defect, X-ray filming was performed on some of the places where the reflected signal was the highest, and no defects were found. Magnetic parti...

　　The quality inspection process of ERW steel pipe includes on-line nondestructive testing, metallographic examination, flattening, combustion destructive test and hydrostatic test. Evaluation process: 　　1, online nondestructive testing 　　The detection arm of the testing station rotates and is placed on the longitudinal welded pipe production line. Observe the position of the weld through a camera. The position of the probe is adjusted by the lever so that the weld overlaps with the laser and saves the parameters. Input the coil number through DATASERVR and DACQ computer. The waveform of the observation defect detection interface is displayed. When the waveform exceeds the alarm line, the thickness measurement information is compared to determine whether it is a defective or interfering wave signal, and the naked eye is checked to see if the waveform is beyond the alarm line. If the alarm line exceeds the alarm line, the alarm will be issued. Close and adjust the welding parameters...

　　Defects in the J55 oil casing fusion zone: 　　After the ERW oil casing, the weld pipe in the heat affected zone of the fusion line was found to be unqualified. The metallographic analysis, scanning electron microscopy, and process investigation were performed. The results showed that the J55 welded pipe was in the fusion line. There is a certain depth of crack defect in the edge of the original plate in the heat-affected zone. The user has a significant expansion of the crack defect due to the small pipe diameter and the insufficient amount of trimming in the pipe making process. The cracks in the edge of the hot-rolled original plate originate from cast slab corners and side subcutaneous bubbles.

　　Welded pipe is generally divided into straight seam welded pipe and spiral welded pipe two types. 　　 Hydrostatic burst strength 　　By the relevant comparison test to verify the spiral welded pipe and Longitudinal yield pressure and burst pressure measured and theoretical values ??match, the deviation closer. But whether it is the yield stress or burst pressure, were lower than the Longitudinal spiral welded. Burst test also shows that the rate of deformation ring spiral welded pipe bursting Longitudinal significantly greater than the mouth. Thus confirmed that the spiral welded plastic deformation capability than Longitudinal, blasting mouth generally confined to a pitch, which is the extension of the spiral weld to rip from a strong binding effect due. 　 　Strength characteristics 　　When the pressure in the pipe withstand, usually two main stress on the wall, that the radial and axial stress stress δ. Synthetic weld stress δ, where α is the helix angle of the spiral weld pipe....