This article describes the reasons that affect the life of the mold copper tube and the corresponding measures to be taken.
Key words: crystallizer; service life of copper tube; countermeasures
Main reasons restricting the service life of copper tubes
Crystallizer vibration table
The billet continuous casting machine adopts the semi-plate spring imitation positive rotation vibration system, but due to the occurrence of steel leakage accidents in actual production, the vibration frame exposed to the lower mouth of the crystallizer is most likely to be adhered by molten steel or residual steel residues enter the vibration mechanical parts , affect the accuracy of the vibration parameters, and even produce polarization phenomenon, which will cause the leaf spring to break in severe cases, which will bring great hidden dangers to the quality of the billet and the normal use of the copper tube.
When the vibrating leaf spring has a long service life, the leaf spring produces linear plastic extension, and the arc of the copper tube in the crystallizer does not coincide with the basic arc of the casting machine, resulting in excessive resistance during casting, resulting in transverse cracks, and the service life of the copper tube shorten.
Assembly of tension leveler
Billet continuous casting machine drawing and leveling machine system is mainly composed of a set of drawing and leveling upper and lower rolls, a set of free rolls, a set of stripping upper rolls and lower rolls and frame, base, transmission system, hydraulic cylinder, etc., for Five-roller two-point straightening structure, but due to the relatively weak maintenance force of our factory and limited technical level, it often happens that the dummy bar deviates from the lower mouth of the crystallizer when feeding the dummy, which cannot ensure the accuracy of arc alignment and artificially increases the billet The resistance increases the wear of the chrome-plated layer of the copper tube.
The key parameter of mold assembly is the adjustment of the water gap. Whether the water gap is even on both sides directly affects the quality of the billet and the service life of the mould. Quality accidents such as deformation and corner cracks, and single-strand production accidents such as breakouts, severely restrict production and affect the quality of billets and the service life of mold copper tubes.
Crystallizer reverse taper
The size of the taper of the mold must be appropriate. Excessive taper will cause the mold to squeeze the billet shell, resulting in concave corners, increased friction between the billet shell and the copper tube of the mold, and aggravated the wear of the copper tube. For copper, hot spots can form in the corner area due to air gaps, causing shell thinning and cracking. If the taper is small, the air gap will increase, the heat flow will decrease, the billet shell will become thinner, and steel breakout will easily occur. In addition, if the taper is too small, the rotation of the corner will be aggravated, and subcutaneous cracks and longitudinal depressions will appear.
Corresponding measures taken
(1) Strengthen spot checks on the crystallizer vibration device. Every time the crystallizer is replaced or overhauled, a special person will check the gap between the leaf spring and the stand to prevent mold slag, cold steel, etc. from entering and causing crystallizer polarization. In addition, after the crystallizer is replaced, the anchor bolts of the crystallizer are fastened in place.
(2) The workshop and the factory strengthen the training of maintenance-related knowledge and operational ability to ensure that the basic data such as the longitudinal centerline and outer arc reference line of the continuous casting machine are identified during the continuous casting repair and overhaul.
(3) Crystallizer assembly.
a. For the off-line crystallizer, do a good job of confirming the inner wall of the copper tube, dismantling it, checking the aging of the sealing rubber ring, whether there is any abnormal change in the water joint between the copper tube and the water jacket, and whether there are foreign objects in the crystallizer, etc., and analyze the specific Make a record of the reason for the offline.
b. The inspection of new copper pipes and water jackets is strictly in accordance with the requirements of the drawings, and all spare parts of the crystallizer are measured, and they can only be put on the line if they meet the requirements. To ensure the accuracy of spare parts when the crystallizer is repaired.
c. During the process of dismantling and assembling copper pipes, two key points must be ensured: stability and accuracy. Prevent pits from appearing due to local stress on the copper pipe, and deformation of the water joint adjustment device, which will ultimately affect the assembly accuracy of the copper pipe. It is strictly forbidden to use sharp objects in the installation of the sealing rubber ring to prevent the damage of the rubber ring that is not easy to observe.
d. The adjustment of the water joint is the core content of the repair of the crystallizer. The upper water joint of the copper pipe should be positioned with the matching copper pipe and water jacket before assembly. The deviation of the upper water joint is not allowed to exceed 0.5mm, and the lower water joint of the copper pipe The seam deviation does not exceed 0.2mm to ensure the water seam accuracy during assembly. Avoid billet defects caused by uneven cooling in copper pipes due to uneven water seams.
e. After the assembled crystallizer is tested for water and pressure for 30 minutes, it can be put into use without leakage or loss of pressure, and records should be made.
Other measures to increase the steel passing capacity of copper pipes
(1) In the process of dismantling and inspecting the crystallizer, foreign objects occasionally appear in the water chamber, and protective measures should be implemented in time according to the different foreign objects. Such as the water flushing method of the crystallizer, the water quality management method of the crystallizer, and the installation of pipeline filters, etc.
(2) During the maintenance process, focus on the arc calibration accuracy of the casting machine, adjust the guide edge spacing of the secondary cooling guide roller, and take measures such as water bar alignment, which effectively reduces the impact on the life of the copper tube due to eccentric wear.
(3) Adjust the production organization mode, reduce the number of stop flow, stabilize the casting speed, and effectively reduce the impact of start stop flow on the life of the copper tube.