1, The casues of straight seam steel quenching deformation is the uneven of various parts of the steel pipe, in the steel pipe to produce residual stress, resulting in deformation of steel pipe. 2, The size of raw materials is not ideal, such as wall thickness deviation is too large, or bending and oval greater, and so the deviation is too large wall thickness is the main factor affecting the quenching and deformation. 3, Steel pipe heating temperature is uneven, or quenching before the existence of deformation of the steel pipe. 4, The external cooling of the steel pipe is not uniform, such as steel pipe quenching fixed, the outside of the pipe in different directions of the cooling rate will be different. 5, In order to make the quenching within the spray evenly, should make the water in the steel pipe to achieve a certain flow rate, which is required by the water supply to ensure that, that is to have enough water within the water. 6, So in order to reduce the external cooling is not uniform, the current straight seam steel pipe manufacturers widely used steel pipe quenching method.

Technical requirements and quality inspection of straight seam steel pipe according to GB3092 "low pressure fluid delivery with welded steel pipe" standard requirements, the nominal diameter of pipe 6 ~ 150mm, nominal wall thickness of 2.0 ~ 6.0mm, the length of the pipe is usually 4 to 10 meters, According to the length or length of the factory. Steel pipe surface quality should be smooth, do not allow folding, cracks, stratification, welding and other defects exist. The surface of the pipe is allowed to have minor defects such as scratches, scratches, weld misalignment, burns and scarring that do not exceed the negative wall thickness. Allows weld thickening at the wall and the presence of internal welds. Welded steel pipe should do mechanical performance test and flattening test and flaring test, and to meet the requirements of the standard requirements. Steel pipe should be able to withstand a certain internal pressure, if necessary, 2.5Mpa pressure test, to maintain a minute without leakage. Allowing eddy current testing instead of hydrostatic testing. Eddy current testing according to GB7735 "steel pipe eddy current testing method" standard implementation. Eddy current testing method is to fix the probe on the rack, flaw and weld to maintain a distance of 3 ~ 5mm, relying on the rapid movement of the pipe to conduct a comprehensive scan of the weld, flaw detector by the eddy current detector automatic processing and automatic sorting, To achieve the purpose of testing. After the inspection of the welding pipe with the provisions of the length of the saws cut off by the flip frame off the assembly line. Steel pipe ends should be flat head chamfer, print mark, finished tube with hexagonal strapping packaging factory.

High-precision cold drawn steel pipe is a new type of high-tech energy-saving products. In recent years, the use of this technology to produce precision steel pipe has been widely used in domestic hydraulic, pneumatic cylinder, coal downhole stent (pillar), oil pump pipe, jack and other manufacturing areas. High-precision cold drawn steel pipe to promote the use of steel, improve processing efficiency, energy conservation, reduce the hydraulic cylinder, cylinder processing equipment investment is important. Cold drawn way: the production of high-precision cold-drawn tube ─ ─ hydraulic cylinder compared with the traditional cutting process, has the following characteristics: (1) High production efficiency: the traditional method of production of an inner diameter of 420 mm, 12 meters long cylinder to be 154 hours, with cold drawing method of production only 4 minutes. (2) High rate of genuine: the boring of the rolling head and play a guiding role in the cutting process, the blank tube due to self-weight deflection, resulting in rolling head and boring tool deviation, resulting in waste. Genuine rate can only reach about 60%, while the use of cold-drawn method of production, genuine rate of up to 95% or more. (3) High metal utilization: the traditional boring method of manufacturing cylinder, metal utilization rate of only 50-70%. With the drawing method of production, the metal is not only cut into iron, but can get 30% extension, metal utilization up to 95%. (4) Improve the mechanical properties of finished metal pipe: the use of drawing method, so that the blank get more than 30% of the plastic deformation, due to hardening and processing of finished pipe metal strength limit greatly improved. Generally in the finished product tube strength limit increased by 60%. High-precision cold-drawn tube is a seamless hot-rolled steel pipe, straight seam welded pipe for the blank, after chemical treatment in a special cold drawn machine, through the special deformation of the design of the mold to draw to produce high-precision tube. Its dimensional accuracy of H10 ~ H8, straightness of 0.35 ~ 0.5mm / m, surface roughness of Ra1.6-0.4.

First: advantages of longitudinal submerged arc welding It can damage the ingot casting structure, refine the grain of steel, and eliminate the defects of microstructure, so that the steel structure is compact, mechanical properties improved. This improvement is mainly reflected in the rolling direction, so that straight stitch steel pipe to a certain extent is no longer isotropic; pouring the formation of bubbles, cracks and loose, but also in the high temperature and pressure under the welding. Second: defects of straight seam submerged arc welded pipe 1, The residual stress caused by uneven cooling. Residual stress is in the absence of external force under the internal self-equilibrium stress, all kinds of cross-section of hot-rolled steel have such residual stress, the general steel cross-sectional size, the greater the residual stress although the residual stress is self - balanced, it has some effect on the performance of the steel members under external forces, such as deformation, stability, fatigue resistance and so on, which may have an adverse effect. 2, After the welding, the non-metallic inclusions inside the straight seam steel pipe are pressed into the sheet, and the stratification is caused. The performance of the straight seam steel pipe in the thickness direction is greatly deteriorated and there is a possibility that the weld, the local strain induced by the weld shrinkage often reaches several times the yield point strain, much larger than the load caused by the load.

There are many kinds of processing methods for pipe fittings. Many of them also belong to the category of mechanical processing. Most of them are stamping method, forging method, roller processing method, rolling method, bulging method, drawing method, bending method, and combination processing method . Pipe processing is the organic combination of machining and metal pressure processing. Examples are as follows: Forging method: the use of forging machine to pipe or part of the end to be extended, so that the outer diameter reduction, commonly used forging machine has a rotary, connecting rod, roller type. Stamping method: Use a tapered core on the punch to extend the pipe end to the desired size and shape. Roller method: the tube placed in the tube, the outer wheel with a roller, for the round edge processing. Rolling method: generally do not have mandrel, suitable for thick-walled tube inside the round edge. Bending method: there are three methods are more commonly used, one method is called extension method, the other method is called stamping method, the third is more familiar with the roller method, there are 3-4 rollers, two fixed roller, an adjustment Roller, adjust the fixed roller from the finished pipe is bent. This method is applied to a wider, if the production of spiral, the curvature can be increased. Bulging method: one is placed in the tube rubber, the top with a punch compression, the tube protruding shape; another method is the hydraulic bulging forming, filling the middle of the tube liquid, * liquid pressure to the drum drum into the required shape , As most of our commonly used bellows production is used in this way.