Whether the burr removal process of the cold roll forming machine is appropriate directly affects the quality of the welded pipe. Sometimes grooves are left due to the scraping of the scraper, which is rejected by the user as a welding defect, which brings serious economic losses to the steel pipe manufacturer.

In this case, the inspection agency found a black negative image with a width of about 3mm and perpendicular to the annular seam near some of the girth welds during the ray inspection of the pipeline butt joints during the installation process (Figure 1). Unfusion defects of grooves produced during pipe making. The staff found that there was indeed a groove with the same width as the negative image near the welding seam of the welded pipe (Figure 2), but the groove was not located on the welding seam, so they doubted the inspection party's statement, and combined with the production of the batch of welded pipes. It is proposed that the groove is caused by the deviation of the scraper when removing the burr. This claim was verified by comparing the width of the image with the size of the squeegee.

Formation of internal burrs in welding

Under the action of the proximity effect and the skin effect of the high-frequency current, the edges of the formed tube blank are rapidly heated to a molten and semi-molten state, and the partially molten metal is extruded when entering the extrusion roll. Burrs are formed on the inner and outer surfaces. The molten metal entering the inner wall of the welded pipe forms the inner burr of the welded pipe weld; the burr extruded from the outer surface of the welded seam becomes the outer burr. Since the internal burr and removal equipment are in the tube, it is difficult to remove it, which has become one of the major technical problems in the production of cold roll forming machine.

Common Problems During Internal Burr Removal

Common problems in the process of internal burr removal mainly include scraping deviation, excessive or small scraping amount, and unclean cleaning. No matter what kind of problem occurs, it will affect the quality of the weld. Under normal circumstances, scraping deviation is the most common phenomenon in cold roll forming machine. Scraping deviation will lead to unclean removal of internal burrs or local thinning of the pipe wall, stress concentration at the edge of the scraper, and in severe cases, it will affect the pressure bearing capacity of the welded pipe.

Solution

The internal burr scraping deviation is mainly manifested as intermittent deviation to one side or both sides. The deviation of the inner burr to one side is mainly caused by the deviation of the center position of the tool holder from the weld. The main reason for this problem of the cold roll forming machine is generally that the position of the connecting plate of the tool bar is not suitable. The position of the tool bar can be adjusted through the adjusting bolt of the connecting plate until the scraping phenomenon disappears. In addition, another kind of scraping phenomenon is the intermittent deviation on both sides. In this case, the height of the cutter head is generally too much higher than the support wheel, which can be solved by adjusting the relative height of the cutter head and the support wheel;the cutter bar connecting plate The loosening of the lock nut can also cause intermittent deviation on both sides when the internal burr is scraped, and the nut needs to be re-locked.

It can be seen from this case that the scraping phenomenon when removing internal burrs will not only lead to local thinning of the welded pipe wall, but also affect the pressure bearing capacity of the welded pipe in severe cases. The groove left after the scraper passes through locally produces stress concentration and bears hoop stress, which causes fatigue in the process of pipeline decompression and boosting. Even a small operating pressure can cause the pipeline to fail in an instant, resulting in an accident. . At the same time, once the scraper deviates seriously, resulting in the failure of the whole batch, it will increase the production cost of the welded pipe manufacturer.

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