1, The chemical composition In order to improve the uniformity of chemical composition in steel and the purity of steel, to reduce the non-metallic inclusions in the tube and to improve the distribution state, it is often used to improve the chemical composition of the steel. 2, Dimensional accuracy and shape The geometry of the seamless steel pipe mainly includes the outer diameter, wall thickness, ellipticity, length, curvature, pipe end face inclination, groove angle and the blunt edge, cross-sectional size of the steel pipe. 3, The surface quality The standard specifies the requirements for the "smooth surface" of seamless steel tubes. Common defects include: cracks, hair lines, within the fold, outside the fold, rolling, straight, outside the straight, separated layer, scarring, pits, convex package, scratching, the spiral road, outside the spiral road, green line, correction concave, such as roller. Crack, slight internal and external straight, minor internal and external spiral, straightening, and so on. In addition to the internal and external cracks, cracks, broken, rolling, Concave, roll as a general defect. 4, Physical and chemical properties Including mechanical properties at room temperature and mechanical properties at certain temperatures (heat and low temperature properties) and corrosion resistance (such as anti-oxidation, water erosion, acid and alkali resistance and other properties) under normal circumstances depends on the chemical composition of steel, performance and steel purity and steel heat treatment methods. In some cases, the rolling temperature and the degree of deformation of the steel pipe will also affect the performance of the steel pipe. 5, Process performance, including the expansion of the pipe, flattening, curling, bending, ring pull and welding performance. 6, Microstructure, including the low-power steel pipe and high-power organization. 7, Special requirements, the user use steel pipe outside the standard request.

The inner coating will fall off the corrosion resistance of steel pipe, steel production need to strictly control the quality problems. Inner coating is mainly small diameter steel pipe water, oil, embroidery, graphite, etc. are not clean, the anchor pattern of the density can not meet the requirements, the coating is not enough adhesion caused. The main forms are: 1, Drum package Drum package is not completely dry because the inner coating case, the tube in the sunlight exposure was wrapped in the coating under the heat of the water after the rapid expansion of the volume, so that the formation of inner coating muster. 2, Vertical loss The emergence of the longitudinal along the tube body is mainly uncoated fluorescent tube in the open when the rain poured into the accumulation of accumulated in the bottom of the tube rust is more serious, rust 4 steel pipe at the same time, more serious corrosion of the site Rust is not complete, it formed along the vertical tube body delamination. 3, Ring drum package Inner drum bag mainly in the tube sand blowing sand blowing compressed air in the water, soot blowing straight nozzle forward, steel pipe in the rotation, forming a ring of water marks, so that the inner coating also formed a muster ring. 4, Start the end of shedding The inner coating falls off basically at the beginning of the inner coating, because there is a fan at the end of the coating to the tube blowing, dry the end of the tube of water, but also prevent moisture in the air into the end of the pipe. The bulging occurs only at the beginning of the coating, not on the end of the pipe. The prevention of fall off measures are: 1, The environmental control within the coating, when the ambient humidity ≥ 90%, or tube temperature below 3 ℃ below the dew point, should not be produced. 2, Outside the coating must be poured into the tube after the cooling water to clean, to ensure that the inner surface of the pipe before drying. 3, Inside the tube before drying with a dehumidifier device, to prevent the impact of moisture to the inner coating quality. 4, Shot blasting to clear the nozzle to clear the time to prevent the nozzle clogging, while ensuring the depth of the anchor pattern, but also have a certain density in order to increase the adhesion of the coating. 5, The speed of anti-corrosion can not be too fast, the pipe between the process must have a certain time interval, so that the tube has a natural air-drying process.

Stainless steel seamless tube of metal and oxygen in the atmosphere to react, in the appearance will form an oxide film. However, the oxidation of the iron oxide formed on the ordinary carbon steel pipe continuously causes the corrosion to be enlarged, and as a result, the pores are formed. This good stainless steel seamless tube is damaged, we can use paint or oxidation-resistant metal such as zinc, nickel and chromium plating to cover the appearance of carbon steel, but, as we expected, this maintenance only is a layer of maintenance film, if the maintenance layer is damaged, the steel will begin to be corrosion. The corrosion resistance of stainless steel depends on the chromium, chromium is a part of steel composition, chrome on steel combined treatment, will change the appearance of the oxide type similar to pure chromium metal surface oxide. This tightly adhered chromium-rich oxide maintains the appearance and avoids further oxidation. Heat treatment process includes heating, insulation, cooling, etc. This is done in order to reduce the deformation of the metal forming process hardening and other deficiencies, so that the deformation of the pipe after processing to restore the performance, to improve its performance. Now the most common heat treatment tools include electric furnace and reverberatory furnace; common control mode is automatic temperature control mode. Different stainless steel seamless pipe fittings on the heat treatment requirements are different, and not all deformation of the tools must be heat-treated, usually the final temperature of low-carbon steel pipe fittings is not less than 723 ℃, then you can not heat treatment, if lower than this temperature or the temperature above 1000 degrees celsius should be heat treatment.

There are two configurations for the piercer's frame. One is the roller and bearing housings installed in two drums, turn the drum to adjust the feed angle, in the horizontal configuration of the roller piercing machine, drums arranged in the rolling line on both sides of the arch; the other is In the vertical arrangement of the roller punch, the drum is arranged in the rack between the four columns, above and below the rolling line. The former form of punching machine when the roll, open the rack cover, with the crane one by one out of the roll. After a punch for roll, the first roll is located in the next roll, the rack cover on behalf of the open after the crane out with a crane. The other is our Φ76mm punching machine, the frame structure is simple, the roller bearing seat is arranged in the window of the arch, by two different sizes of the arch on the window to set the feed angle. Feed angle adjustment with the gasket, the actual operation, do not adjust the feed angle. In order to meet the wall thickness accuracy requirements of perforated capillary, in the rack design must pay special attention to the minimum rebound and maximum bending strength problems. Vertical arrangement of the roll and listed on both sides of the bearings are installed in the drum, cone roller piercing machine to adopt this arrangement. The roll is replaced with the top cover of the frame. To shorten the replacement time, the top cover is designed to be hydraulic or removable, which reduces the height of the plant.

Welded steel pipe production process is to steel, steel and other methods of rolling with a variety of methods or in accordance with the direction of spiral bending into the required cross-sectional shape, and then by means of heating, pressurized, with different welding methods of welding To obtain a steel pipe. Therefore, the defects of welded steel pipe is divided into two parts: steel base metal defects and weld defects. 1.Steel base metal defects Defects in the sheet metal after rolling and other processes, most of the plane-like, parallel with the surface; the main defects are layered, inclusions, cracks, folding, which is the most common layer of internal defects. Delamination will produce a variety of cracks, when the plate is subject to the tensile stress perpendicular to the surface, the stratification will seriously affect the strength of steel, it is not allowed to exist defects. 2.Weld defects Weld defect is the weld during welding or welding defects in the weld, divided into cracks, pores, slag, not penetration, not fusion, undercut and other weld defects. Welds in the dense pores, slag, etc. are dense three-dimensional defects, cracks, non-fusion is a planar defect, a great harm. Strip-like slag, not penetration and so is a strip defect, harmful. Stomata, small slag and other point-like defects. The defects in the weld more easily lead to the strength of steel, plastic and other issues, seriously affecting the quality of steel pipe, welded pipe quality directly affects the safe operation of oil and gas pipelines and service life, and therefore the main weld detection for welding Cracks in cracks, stomata, slag, not penetration, not melting and other dangerous defects detection.