Measures to prevent transverse cracking of cold drawn pipes

1. Improve the heating quality of the billet (1) Heating strictly according to the process requirements, and using the upper limit temperature heating to avoid low-temperature heating. For example, the heating temperature of carbon steel (1-45.) billets is increased by 20-30℃ compared with the original process, and the effect is better. According to statistics, the cracks dropped by nearly 40% in the following five months. (2) For inclined-bottom furnaces, materials must be moved frequently to ensure that the blanks are heated evenly and to prevent the appearance of yin and yang surfaces. At the same time, close the furnace door after finishing the feeding to reduce heat loss. (3) Strictly control the rolling rhythm to ensure that the billet is heated thoroughly and no black core occurs. Avoid the black spiral phenomenon of perforation. (4) Use high-quality heavy oil to ensure the heating quality of the billet.
2. Improve the accuracy of capillary wall thickness (1) Correctly adjust the process parameters of piercing and pipe rolling, improve the accuracy of tools and molds such as rollers, and make the blank and raw pipe deform evenly during the piercing and pipe rolling processes. (2) Accurately adjust the centering position and install a supporting roller device so that the top can be aligned with the center of the blank to avoid eccentric perforation. (3) Install and adjust the holding roller, and hold the ejector pin tightly to prevent the ejector pin from sinking. (4) Customize the equipment to keep the equipment in good condition and ensure the accuracy of capillary wall thickness. (5) Strengthen management, measure capillary wall thickness frequently, and make timely adjustments if problems are found.
3. Avoid rapid water cooling of the capillary tube and control the cold steel rolling to coordinate the production rhythm so that the waste tube stays on the table for a short time before rolling. Ensure that the final rolling temperature of the steel pipe is not lower than 850°C, ensure uniform internal structure of the steel pipe, reduce residual stress, moderate cooling water pressure, prevent water leakage, and avoid local rapid water cooling of the steel pipe, causing local cold brittleness.
4. Prevent capillary straightness and folding to improve the quality of tools and molds. Check the tools and molds frequently. If you find that the tools and molds are worn or not meeting the requirements, replace them in time. Frequently check the surface quality of the capillary tube, find problems, and solve them in time.
5. Improve the quality of capillary grinding. Surface defects such as rolled folds and outward folds of capillary tubes must be ground cleanly. The grinding width must be 8 times greater than the grinding depth. After grinding with the grinding wheel, it must be planed with a knife. To improve the quality of grinding.
6. Annealing after capillary grinding (1) Due to factors such as poor heating quality of the billet or low final rolling temperature, the steel pipe has defects such as residual stress. After capillary annealing, the residual stress of the steel pipe is eliminated, the internal structure is improved, and the plasticity is improved. , to facilitate cold drawing processing and deformation. (2) After the steel pipe is ground, work hardening occurs in the grinding area, stress is concentrated, the hardness of the grinding surface increases, the plasticity decreases, and the deformation resistance increases. After the capillary is ground and then annealed, the work hardening and stress concentration caused by the grinding can be eliminated. The grinding part can obtain the same good plasticity as other parts, which facilitates processing deformation. (3) Annealing after capillary grinding must meet the requirements of the annealing process, so that the capillary is heated evenly and through the core, so that the tissue condition of the defective part can be fully restored. Eliminate internal stress, reduce hardness and improve plasticity.

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