High-frequency welded pipe production process

High-frequency welded pipe production process
High-frequency welded pipe production process



Figure 5-1 is a schematic diagram of the production process of a small high-frequency straight seam continuous electric welded pipe (without tension reducer). High-frequency electric welded pipe units generally use cold and hot rolled coils as raw materials. Before the raw material is formed, it is subjected to flash butt welding by unwinding, straightening, leveling, cutting, and end, and then molding and welding into the molding machine. When necessary, trimming is performed to make the strips have the same width along the length direction, so that the weld gap is uniform after forming, and the weld quality is improved. In order to continuously carry out the forming and welding process, in addition to the head device such as the butt welding of the coil end, a looper device is also required. The types of strip looper used in the electric welded pipe unit are pit type, overhead type, cage type, tunnel type and spiral type. The most widely used modern electric welded pipe continuous unit is the spiral looper.

The formed and welded steel pipe removes internal and external burrs. External burr removal is generally performed by first scraping, then smoothing with a roller, and the internal burr requires a special device. The weld is then cooled with water. The role of weld cooling is to ensure the structural properties of the weld and to prevent the weld from being upset during sizing. Since the steel pipe is deformed by heat during welding,



Figure 5-1 φ0. 3~168. 3mm small high frequency straight seam continuous electric welded pipe production process



1-belt coil; 2-leveling; 3-cut head butt welding; 4 one looper; 5 forming machine; 6-welding; 7 one to remove internal and external burrs; 8-cooling; 9-sizing; 11-straightening; 12 eddy current testing; 13-flat end; 14-hydraulic test; 15-check; 16-printing; 17-oiling; 18-packaging

The outer diameter dimension accuracy and roundness of the finished pipe improve the weld quality and straighten the steel pipe. The welded steel pipe must be cold sizing. After the sizing, the steel pipe is sawed to be close to the length of the finished product, and then straightened on the straightening machine, and the pipe end is processed on the flat end machine to ensure the length of the steel pipe. The finished steel pipe is subjected to a finishing process such as hydrostatic test, inspection, wire and coating (or galvanizing), and finally packaged into the warehouse.

In the small and medium-diameter electric welding unit, in order to improve the unit productivity, reduce roll change, increase the operating rate, expand the range of product specifications and improve product quality, the tension reducer can be configured. After the sizing and cutting process of the welded pipe unit, a reheating furnace, a tension reducing machine and a flying saw are added. The steel pipe after the diameter reduction is further subjected to the above-described finishing process.

The straight seam electric welded steel pipe unit includes a blank preparation section, a formed welding sizing section and a finishing section. The blank preparation section includes an unwinder, a leveler, a shear butt welder, a looper, an edge processing device, and a full-width ultrasonic flaw detection. Forming and welding sizing sections include forming machines, welding equipment, burr removing devices, weld heat treatment devices, sizing machines, straightening heads, and the like. The finishing section is mainly to carry out necessary machining, repair and inspection of semi-finished steel products. The main process equipment selection is mainly based on design scale, product plan, technical conditions, construction funds, raw materials and energy conditions.

(1) The preparation section of the blank preparation section is basically the same as that of the cold-formed steel preparation section. For details, see the composition and main equipment of the 3.3 strip preparation section.

1 Unwinder: The models of the unwinder are various. Most of them are double-cone type. In order to make the steel plate go, the uncoiler should have a steel coil centering slide; in order to meet the requirements of welding for one cutting and slitting, the uncoiler should also be able to unwind in two directions.

2 Steel plate leveling: The raw material for the production of ERW welded pipe is steel coil. The curvature of the strip steel is small, the bending direction is the same, the curvature is from J, to the smooth and progressive, and the thickness is not very thin, so the steel leveling machine of the ERW unit is generally Reduce the leveling roller to five

Root, and increase the roller distance, thicken the roller diameter, remove the support roller, so that the structure of the whole machine is simplified, and the function is more professional. At present, the more popular models put the pre-leveling delivery roller and the leveling roller on one integral frame, the delivery roller hydraulic cylinder is opened and closed, and the machine is synchronized; the five-roll leveling is three or two or two and three times. The lower amount adjusts the screw and the nut electric or manual, but it should have the function of the integral rapid synchronizing mechanical synchronization of the pressing roller to meet the requirement that the leveling machine is opened and the strip is in a slack state when the head is aligned.

3 Shear butt welding: The butt welding process will weld the steel tail and the head butt joints, and cooperate with the loop to keep the welded pipe section continuous. In the more advanced ERW units, the slanted seam pattern is applied to the head so that the butt weld is inclined at an angle to the vertical line of the strip centerline. ERW unit head welding methods include CO2 gas shielded welding, submerged arc welding, flash welding, and manual arc welding. The ERW unit has a hydraulic shearing machine for the strip head and tail shear of the head welding. The cutting method includes upper cutting or lower cutting, upper and lower shearing.

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4 Strip edge processing: In order to make the width of the strip along the full length direction and make the edge of the strip meet the requirements of the welded steel tube, it is necessary to trim or mill the edge of the strip. If it is a slitting material, it must be prevented from mechanical damage on the edge of the steel strip when it is transported to the welded pipe production line. If the online disc shearing process is used, it is rough due to shearing, and generally it is necessary to plan the edge or slightly mill the edge of the steel strip. Otherwise, the weld seam will be mixed due to the uneven edge of the steel strip after trimming.

If the in-line milling process is used, small burrs may be generated at the corners of the edge of the steel strip after milling, and small burrs may cause sparking during welding. Therefore, the small burrs on the edge of the steel strip are cleaned after milling.









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