Research On Continuous Casting Of Cu-15Ni-8Sn Alloy Round Ingot

Cu-15Ni-8Sn alloy,as an amplitude modulation reinforced copper-based elastic material,is widely used in the fields of machinery,aviation,aerospace and marine engineering due to its high strength,wear resistance,corrosion resistance and excellent anti-stress-relaxation properties,etc.However,the Sn element in this type of alloy is prone to segregation during the casting process,which affects the processing performance and the comprehensive properties of the alloy and severely limits its application.Based on the analysis of the research status,Cu-15Ni-8Sn alloy prepared by continuous casting was studied.There are two main parts including mold structure optimization research by horizontal continuous casting,and process parameter optimization research by vertical continuous casting of Cu-15Ni-8Sn alloy.The influence of different mold structure and process parameters on the structure and composition of Cu-15Ni-8Sn alloy was analyzed by spectrometer and metallographic microscope.The main conclusions are as follows:(1)For the round ingot of Cu-15Ni-8Sn alloy with a diameter of 65 mm,the preparation parameters of horizontal continuous casting are: the pouring temperature of 1270 °C,the drawing speed of 169 mm/ min and the cooling water volume are all 350 L/h.Under the above process parameters,the mold structure is optimized.When the bottom of the mold is provided with a slot angle of 180 °,a slot length of 144 mm and a slot thickness of 5 mm,the relative horizontal distance between the upper and lower solid-liquid interfaces is reduced to0.6 mm,which is 7 % of the bottom un-slotted ingot.The axial angle ? tends to 90 °,the uniformity of the temperature field above and below the ingot is significantly improved,and the uniformity of the structure and composition is significantly improved.(2)For the round ingot of Cu-15Ni-8Sn alloy with a diameter of 160 mm,the best preparation parameters for vertical continuous casting are: the pouring temperature of1235 °C,the drawing speed of 60 mm/min,and the cooling water volume is 600 L/h.Under the above process parameters,the relative segregation of the Sn element is only 3.70 %,and the macro-segregation is significantly improved when pouring at a low liquid level.(3)The macrostructure of alloy prepared by vertical continuous casting is composed of thesurface chilling zone,the middle columnar crystal zone and the central equiaxed crystal zone.The microstructure of the alloy is a developed dendrite which include the matrix and segregation zone.In terms of the matrix,the secondary dendrite spacing increases gradually from the surface to the center of ingot.The perimeter of the matrix gradually increases from the surface to the center of ingot,and the fractal dimension of the matrix increases from the surface to the center of ingot.The reduction of secondary dendrites,or the increase of the perimeter of the matrix,or the increase of the fractal dimension of the matrix can help to improve the uniformity of the distribution of Sn element components and improve macro-segregation.In terms of segregation zone,The main segregation points are grade I and grade II,and the degree of segregation is mainly affected by the volume of large segregation points(grade I segregation points).At the same time,the fractal dimension of segregation structure decreases from the surface to the center of ingot.