Effect and mechanism of process parameters on microstructure and properties of Cu-Ni-Si alloy prepared by temperature controlled mold continuous casting

Abstract

ABSTRACTC70250 copper alloy rod billets with Ø20 mm were prepared by a self-developed temperature controlled mold continuous casting (TCMCC) technique. The evolution of microstructure and mechanical properties of rod billet at different casting speeds and mold temperatures was investigated. The influence mechanism of different process parameters on microstructure and properties of rod billet was revealed. The results show that C70250 copper alloy rod billets with “/ \\” shape inclined columnar grains and equiaxed grains mixed structure are prepared when the melt temperature is 1200 °C, the cooling water temperature is 20 °C, cooling water flow rate is 400 L·h−1, the casting speed is 10∼50 mm/min and the mold temperature is 1050∼1090 °C. When the casting speed increases from 10 mm/min to 50 mm/min, the average grain size of columnar grains increases from 0.72 mm to 1.43 mm gradually, and the number of equiaxed grains decreases gradually. Besides, the tensile strength of the rod billet decreases from 305 MPa to 252 MPa, and the elongation increases from 33.5% to 42.1%. When the mold temperature increases from 1050 °C to 1090 °C, the average grain diameter of columnar grains increases from 0.72 mm to 1.43 mm gradually, and the number of equiaxed grains reduces gradually. Besides, the tensile strength of the rod billet decreases from 326 MPa to 275 MPa, and the elongation increases from 31.2% to 41.2%. With the increase of casting speed and mold temperature, the number of nucleation on the mold wall reduces, and the average grain diameter of columnar grains increases, which reduces the number of grain boundaries per unit area. Therefore, the tensile strength of C70250 copper alloy increases and the elongation decreases.