Copper mould tube is a very important part that undertakes the role of steel water condensation molding. The quality directly affects the quality of the billet, and also has a great impact on its own life. During the production process of continuous casting, the inner wall coating of copper tubes and hot steel water contact, corrosion, and friction often cause thermal deformation. And the damage to the inner surface coating. Affects the operation efficiency of the continuous caster. Affects the quality of the casting billet. Therefore, we need to ensure the quality of the copper mould tubes, improve the life span, improve the working quality and efficiency of the continuous casting machine.
Many manufacturers are working to explore improving their service life. First, from the single cone of the inner wall of the copper tube to the multi-cone design, and then developed to a parabolic surface. From the copper tube raw material, from pure copper, phosphorus copper to silver copper and chromium and zirconium copper. Promote the thermal conductivity, improve the anti-deformation ability and life. However, the traditional process of hard chromium plating is used for the inner wall plating of the copper pipe. Chrome plating has high hardness and wears resistance but a thin coating with fine cracks.
In addition, the thermal expansion coefficient of chromium and copper is relatively different. More lateral cracks can occur for use at high temperatures. During continuous casting, steel water penetrates into the copper surface through cracks and enables it to produce more cracks. Therefore, in the long-term corrosion of steel water, the chrome layer will appear pulverization and fall off, and its wear resistance is greatly reduced. In the casting process, the chrome coating is quickly worn out, so the wear resistance performance of the chrome coating is very limited, and the service life is relatively short.
How to solve this problem? In order to improve the durability resistance of chromium coating, prolong the service life of copper mould tubes, add nickel-cobalt alloy coating layer and crystal copper pipe surface, as a transition layer. Therefore, it is known as a nickel-cobalt alloy-hard chromium coating because of its good corrosion, heat erosion resistance, and wear resistance. It acts as a binder between the inner surface of the transistor and the chrome plating layer, greatly improving the wear resistance of the chrome plating layer. In addition, after the chrome plating layer is worn, the nickel-cobalt alloy coating can continue to work in the chrome plating layer and prolong the life of the crystallization device copper tube.