The High Temperature Fatigue And Thermal Fatigue Behaviors Of Copper Alloys Used For Continuous Casting Crystallizer

Steel production has entered the era of continuous casting and rolling, The quality of crystallizer play a decisive role in billet quality and continuous casting production efficiency. Copper also known as the heart of the Continuous casting crystallizer. Besides being damdged by the liquid steel Scouring and the vibration of the crystallizer, the copper is also subjected to the thermal stress caused by the high temperature steel and cooling water.The research in this paper mainly include: Ag-Cu,Cr-Zr-Cu,Ag-Cu and Cr-Zr-Cu with 1mm Ni-Co coating were chosen. By tensile test at room temperature and high temperature, high temperature fatigue tests at 300℃,400℃,500℃and the thermal fatigue test , the main conclusions drawed from study just as following:(1) Solid solution strengthening effect produced by adding alloying elements make the two alloys have a good room and high temperature strength. As the compound by adding Cr and Zr in addition to play solid solution strengthening effect,but also play a role in precipitation strengthening. So the yield strength and the tensile strength of Cr-Zr-Cu alloy are higher than the Ag-Cu alloy,s at the room temperature and 350℃.The mechanical properties of alloys with coating are better than the alloys without coating.(2) By the high temperature fatigue tests, it can be concluded that the high temperature fatigue properties of Cr-Zr-Cu alloy are better than the Ag-Cu alloy,s at 300℃,400℃,500℃. Two types of copper alloys, high temperature fatigue properties are decline with the temperature increases. The second-phase particle of Cr-Zr-Cu alloy are growing up with the temperature increases, that makes the precipitation strengthening effect decreased lead to the high temperature fatigue properties gradually decreased.(3) At the upper limit temperature of 450℃, minimum temperature at room temperature for two types of copper alloys and alloys with 1mm Ni-Co coating had thermal fatigue test. It can be concluded that all alloys, hardness are decline increased as the hardening effect of eliminating with the number of thermal cycling. The Zr element on the Grain boundaries are consumed might result in the hardness decreased of the Cr-Zr-Cu alloy. The hardness of Cr-Zr-Cu alloy is always higher than the hardness of Ag-Cu alloy. The hardness have been significantly improved after plating the coating.The thermal expansion coefficient between Cr-Zr-Cu alloy and the coating is large difference lead to the coating flaked.