The crystal copper tube is a very important component, which is responsible for the condensation and forming of molten steel. Its quality directly affects the quality of the billet, and also has a great impact on its own life. In the continuous casting production process, thermal deformation often occurs due to the contact, corrosion and friction of the inner wall coating of the copper tube with the high temperature molten steel. and damage to the inner surface coating. Affect the operating efficiency of the continuous casting machine. Affect the quality of the casting billet. Therefore, the quality of the copper tube of the mold is guaranteed, the service life is improved, and the working quality and efficiency of the continuous casting machine are improved.
Many copper transistor manufacturers are exploring ways to improve their service life. 1. From the single-cone to the multi-cone design of the inner wall of the copper tube, and then to the parabolic surface. From the perspective of copper tube raw materials, from pure copper, phosphor bronze to silver copper and chromium zirconium copper. Advance thermal conductivity, improve deformation resistance and longevity. However, the traditional process of using hard chrome plating is still used in the coating of the inner wall of the copper pipe. The chrome plating layer has high hardness and good wear resistance, but the plating layer is thin and has fine cracks.
Another point is that the thermal expansion coefficients of chromium and copper are quite different. More transverse cracks appear when used at elevated temperatures. During continuous casting, molten steel penetrates the copper surface through cracks, which in turn produces more cracks. Therefore, in the long-term corrosion of molten steel, the chromium plating layer will appear chalking and falling off, and its wear resistance will be greatly reduced. During the casting process, the chromium plating layer will be quickly worn away, so the wear resistance of the chromium plating layer is very limited , the service life is relatively short.
How to solve this problem, in order to improve the wear resistance of the chromium coating and prolong the service life of the crystal copper tube, a nickel-cobalt alloy coating is added to the chromium coating and the surface of the crystal copper tube as a transition layer. Therefore, it is called nickel-cobalt alloy-hard chromium coating because nickel-cobalt alloy coating has good corrosion, thermal erosion and wear resistance. It plays the role of a binding agent between the inner surface of the copper transistor and the chrome-plated layer, which greatly improves the wear resistance of the chrome-plated layer. In addition, after the chromium plating layer is worn, the nickel-cobalt alloy plating layer can continue to work as the chromium plating layer to prolong the life of the copper tube of the mold.