LSAW Steel Pipe

　　The diameter of steel pipe can be divided into outer diameter, inner diameter and nominal diameter. 　　The outer diameter of the pipe with the antiseptic spiral steel pipe is denoted by letter D, followed by the size and wall thickness of the outer diameter. 　　For example, the anticorrosive spiral steel pipe with an outer diameter of 108 has a wall thickness of 5mm, which is expressed by D108*5. The plastic pipe is also expressed by the outer diameter, such as De63. Others such as reinforced concrete pipes, cast iron pipes, and galvanized pipes are indicated by DN. Design drawings are generally expressed in terms of nominal diameters. The nominal diameter is a standard that is conveniently and artificially specified for design, manufacture and maintenance. It is also a nominal diameter and is the specification name of a pipe (or pipe fitting). 　　The nominal diameter of the pipe is not equal to its inner diameter and outer diameter. 　　For example: a nominal diameter of 100MM sp...

　　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...

　　Surface microcracks of lsaw steel pipe impact on product quality greatly, ranging from commuted, while in retirement, especially niobium, vanadium, titanium Longitudinal most prominent, has seriously affected the improvement of product quality and finished product rate. This not only gives the enterprise has brought huge economic losses, but also restricts the development of varieties of plate production line. Longitudinal surface microcracks mainly has edge crack, longitudinal, star cracks, its causes both improper rolling process parameter control, there are abnormal production of continuous casting process, the slab cracks genetic, residual element enrichment. 　　Longitudinal surface microcracks severely affect product quality. Longitudinal surface micro cracks main reason is the continuous casting mold copper coating off. This aspect will lead to copper penetration into the solidified shell austenite grain boundaries, grain boundary cracks; on the other hand will be uneven due ...

　　Transverse crack after lsaw steel pipe measures rework appear, specifically: 　　1. Confirm defect 　　All welds 100% UT inspection, crack marked location, length, depth and direction. If the entire weld has defects, the proposed dig out the entire re-submerged arc weld, partial repair is recommended SMAW. 　 　2, Planing preheat 　　Preheating temperature is 110-170 ℃, preheating temperature weld both sides of the detection position is not less than 150mm, the heating is within the range of from defects around 500mm. 　　 3, Gouging 　　Gouging out both ends of the range of cracks, weld integrity is not less than 50mm Outbound middle gouging, gouging ends gently to smooth the transition, the transition surface and a vertical line at least greater than 45 °. Gouging carbon rod angle should be at 60 ° or less, particularly in the crack to arrive at an angle as small as possible. 　　4, Polished 　　Polished to no black, polished surface after the transition should be smooth, there sh...

　　Lamination defect control measures of spiral steel pipe is following below: 　　 1, to improve the toughness of plastic tube 　　Improve the cleanliness of molten steel, to reduce the harmful inclusions; increase the proportion of the slab crystal axis, to reduce the center segregation and center porosity; the use of reasonable cooling system to avoid cracks occur within the slab; billet or rolling slab to be taken offline slow cooling process, reduce internal stress, thus ensuring the microstructure and mechanical properties of the finished tube and pipe meet the technical standards. 　　 2, the reasonable control of the heating temperature 　　By measuring the thermoplastic curve, choose the best heating temperature. Note also that there is enough heating tube holding time, in order to reduce and improve plastic deformation resistance and toughness. 　　 3, lower roll speed 　　Roll speed is a key parameter piercing process, the roll speed from low to high variations in the process...

　　Generally speaking, the welded steel pipes are divided into general welded pipe, galvanized welded pipe, oxygen welding tube, metric system welded tube, transformer tube, welding thin wall pipe and spiral welded pipe etc. 　　General welded pipe: General welded pipe adopts Q195A, Q215A and Q235A or mild steel as raw materials. It is used to transfer the low pressure fluid. In addition, the pipes need water pressure, bending and flattening test etc. Usually, it has some certain requirements on the surface quality. The length of delivery is often from 4 to 10mm. The specifications of welded pipe in nominal diameter are different from actual size. Depending on the wall thickness, welded pipe are also divided into common steel pipe and thicken steel pipe. 　　Galvanized welded pipe: In order to enhance the corrosion resistance, the general welded pipe is galvanized zinc as protective layer. Galvanized steel pipe has two types: hot dip galvanized pipe with thicken zinc layer and electrica...

　　The influence of ssaw steel pipe production process factors on the quality of single-side welding double-sided forming welds mainly includes welding current, welding speed, number of welding layers, electrode type and electrode diameter. 　　1. Welding current. The proper choice of the welding current size directly affects the final welding quality. Excessive welding current can increase the productivity and increase the penetration depth, but it is prone to defects such as biting and welding, and increases the tendency of stomata. In particular, when the vertical welding operation is difficult to control the molten pool, the occurrence of welding defects, arc length increases, the welding current is too small, the penetration depth is reduced, prone to defects such as incomplete penetration, poor fusion, slag inclusion, and disconnection. During the training, for those students who have just come into contact with welding, this is a difficult problem to grasp. During the single-side...