Welded pipe unit welding process using an open book, pinch delivery, straightening, cutting, orientation, butt welding, looper, on the medium, the process can be complicated and changeable, three steps of welding pipe welding process:   Specific butt welding process is:   1, After the coil is well positioned, the left and right conical heads of the uncoiler can be inserted into the coil and rotate at the same time, the lead is sent to the nip roller, the roller of the nip roller is pressed down, the coil car and the magnet roller can be returned in situ.   2, In order to spring steel can accurately run in center, uncoiler before the operation of the overall axial movement + 150mm. After the uncoiler is started, the strip passes the pinch roller to the leveler equipped with the dedusting unit.   3, The straightening of the spring steel strip with a sliding hydraulic shears of the head and tail of the strip cut (strip head can be immediately slipped into the waste inside, the strip tail can be cut off with the output device to collect online outside of the special container).

The bearing capacity of the welded pipe is related to two points, one is the mechanical properties of steel, which is often said yield point, tensile strength, elongation and impact toughness, and the other is related to the geometric characteristics of its cross-section. Ordinary circular longitudinal welded pipe resistance to local buckling the strongest, so it is to withstand radial internal pressure and radial external pressure of the best components. In the same steel, the same area and the same support conditions, the rectangular bearing capacity of straight pipe under eccentric compression, circular and square steel pipe bearing capacity of the strongest axis, but the square and rectangular straight seam pipe in the subject nodular resistance to local buckling than circular pipe. Seamless steel pipe and straight seam welded pipe compared to the former production process is complex, high quality and expensive, less used in engineering, the latter more applications. Straight seam steel pipe currently made of steel can be structurally combined with the advantages of the two, can make the straight seam steel pipe in the lateral compression state, its compressive strength can be doubled, at the same time due to the existence of straight seam pipe, improve the rigidity of steel pipe, the two play a role together, thus greatly improving the carrying capacity.

In order to ensure that the wall thickness of steel pipe is uniform, the center axis of the tube must be punched. Therefore, the pressure before the hole extrusion, ingot or billet to be shaped; cross-piercing, round billet to be centering. The purpose of centering is to facilitate the perforation of the nose nose aligned tube axis to prevent the bud when the perforation biased to reduce the uneven thickness of the front end of the capillary while improving the oblique rolling fL bite bite conditions so wear fL process Smooth progress. The centering method is cold and hot. Heat centering is in the tube heating, with compressed air or hydraulic punching in the hot state, the device is set at the piercing machine at the front desk. This method is highly efficient, has no metal consumption, is simple in equipment and has a wide range of applications. At the same time, a good centering hole size can be obtained because the shape of the punch matches the shape of the tip nose. However, over the past decade or so, with the improvement of technology and equipment, fewer and fewer units are equipped with heat-set centers. Some foreign manufacturers believe that perforation of the rotating bite on the tube has a certain self-aligning effect.

Resistance Welding (ERW) is a low-cost, high-efficiency pipe manufacturing technology whereby various technically produced steel pipelines are called ERW pipe. ERW pipe is made of steel plate or strip after the high-frequency resistance after welding and resistance welded steel pipe, which has a longitudinal weld pipe has been widely used in oil and gas pipelines, casing, coiled tubing and soil Cheng parts (such as scaffolding). In recent years, ERW technology has also been used to produce economical oil access tubes, on the one hand from the low cost of ERW technology; on the other hand, this oil access tube has been made from inexpensive carbon steel to reduce pipeline costs. Due to the ERW process is a local heating and pressure forming method, under pressure after welding forming, the rapid loss of heat along the metal pipe and curly forming steel, the cooling rate can often reach the critical cooling rate of steel in the ERW pipe. The formation of martensite welding zone, thus affecting the performance of the welding zone and the entire pipe performance is not uniform. Therefore, it is necessary to use post-weld heat treatment to improve the microstructure of the weld zone so that the weld zone has the same microstructure and performance as the pipe body, ensuring the uniform microstructure and properties of the ERW pipe, thus alleviating the corrosion of the ERW pipe in the corrosive environment selective erosion.

First, the two sides of straight seam steel pipe billet heated to the welding temperature, the extrusion roller squeeze, forming a separate metal grains mutual penetration, crystallization, the ultimate form a solid weld. If the extrusion pressure is too small, the number of individual crystals is small, the strength of the weld metal will drop, and cracking will occur after being forced. If the extrusion force is too large, the molten metal will be extruded out of the weld, high weld strength, and will attack a small amount of internal and external burr, as well as the formation of welding joints and other defects. Second, straight seam high-frequency induction coil should be as close as possible squeeze roller position. If the induction ring is far away from the squeeze roller, the invalid heating time is longer, the heat affected zone is wider and the weld strength is decreased; on the contrary, the edge of the weld is lack of heating and the molding is poor after extrusion. Third, the strip into the welded pipe unit, the multi-roll rolling, the strip gradually rolled up to form a circular tube with a tooth gap, adjust the reduction of the squeeze roll, the weld gap to master in the 1 ~ 3mm, and make both ends of the weld flush. Fourthly, the welding temperature of straight seam steel pipe is mainly affected by the high-frequency eddy current thermal power. According to the formula, the secondary frequency of the high-frequency eddy current is influenced by the frequency of the current. The eddy current heating power is proportional to the square of the current excitation frequency. Also by the encouragement of voltage, current and capacitance, inductance.