Multichannel Test Device For Hot Tearing Tendency Of Nonferrous Alloy Casting And Its Application

Hot tearing is an irreversible casting defect,which is common in aluminum alloy and other non-ferrous alloy castings,and seriously affects the quality and service life of castings.At present,there is no effective method for direct detection,and its characteristics can not be well characterized.Therefore,if an experimental device can be provided to further enrich the experimental means and methods used in the alloy hot tearing research institute,and applied to the practical production guidance,it will have certain engineering application value.On the basis of a large number of research and experimental exploration,this subject independently designed and developed a multi-channel testing device suitable for the hot tearing behavior of non-ferrous alloy.According to different types of alloy,choose the corresponding pouring mode,can use top or bottom pouring type;Multiple test rods with different diameters can be prepared at the same time,and it is easy to study the effects of different sizes and cooling rates on the hot tearing tendency of the alloy.The critical shrinkage force and temperature in the solidification process can be collected at the same time to study the influence of this important information on the hot tearing tendency of the alloy.The experimental equipment has clear ideas,convenient data collection and processing,reasonable design and environmental protection,which provides important experimental means and methods for the subsequent research on the formation mechanism of hot tearing of nonferrous alloy.Combined with casting experiment and numerical simulation,the filling property and stress distribution of Al-Cu alloy at different casting temperatures and different mold temperatures were studied.The hot crack indicator(HTI)in Pro CAST software was used to predict the hot tear tendency of the alloy.The results show that the casting temperature has a significant effect only when the mold temperature is low(25?),and the effect of the mold temperature on the hot tearing and filling properties of the alloy is significantly greater than that of the casting temperature.Then,within the research temperature range,the casting temperature of 670?and the mold temperature of 225?are optimized as the best casting process parameters of Al-Cu alloy.The Al-Si aluminum alloy with small hot tearing tendency and Al-Cu-Mg aluminum alloy with large hot tearing tendency were selected as the contrast alloy.Based on the CSC algorithm proposed by Clyne-Davies theoretical model,the thermal analysis of Al-Cu alloy,Al-Si aluminum alloy and Al-Cu-Mg aluminum alloy and the hot tearing index in simulation were obtained as CSC_Al-Cu-Mg>CSC_Al-Cu>CSC_Al-Si.The casting experiments of Al-Cu alloy,Al-Si aluminum alloy and Al-Cu-Mg aluminum alloy were carried out by using the designed hot tearing mold and test system under the casting temperature of 670?and mold temperature of 25?.Analysis of alloy solidification shrinkage force-time curve and using scanning electron microscope(SEM)to observe the tearing test bar fracture morphology,show that the alloy hot tear formation mechanism is intergranular bypass,the metal liquid feeding to dendrite pores and a combination of liquid membrane,thus further validated the feasibility of the multi-channel test method and device,the reliability and practicability.