ZL205A Simulation And Control Of Stress-strain In Low Pressure Casting Solidfication

In this paper,ZL205 A alloy is used as the research material,and a large-sized cylinder with wall thickness difference structure is poured by low-pressure casting method.The stress-strain distribution and deformation law of the solid structure during the solidification process of the cylindrical structure are studied,and the deformation of the cylinder is analyzed.Based on the mechanism,the effect of cooling rate on the stress and strain of the casting was analyzed.The stress and strain of the large casting was improved by improving the process scheme to control the solidification rate of the casting.The stress field of ZL205 A fine rod castings was simulated.The stress-strain relationship and the factors affecting the stress and strain during the solidification process of the thin rod castings were analyzed.It was found that the greater the cooling rate of the metal liquid,the shorter the solidification time and the relaxation of the alloy during the solidification process.As the time is shortened,the stress generated during the solidification of the casting increases,but the strain decreases.The relationship between the cooling rate,yield strength and response time was analyzed.The mathematical relationship between the yield strength and response time and the cooling rate was obtained by fitting.The relationship shows that the casting has a critical cooling rate in the cooling process,when the cooling rate is less than the critical cooling At a rate of 2.2 ° C/s,the linear relationship between the yield strength and the cooling rate,the cooling rate increases,and the yield strength increases linearly;when the cooling rate is greater than the critical cooling rate of2.2 ° C/s,the yield strength and the cooling rate match.In the exponential relationship,the cooling rate increases and the yield strength increases exponentially.There is a similar mathematical relationship between the yield strength and the cooling rate between the strain response time and the cooling rate.The critical cooling rate is also 2.2 ° C/s.When the strain response time is greater than the solidification time,no plastic strain occurs in the solidification zone.The stress and strain simulations were carried out on cylindrical parts with complex structure.The temperature and stress fields of the cylinder parts were analyzed from different angles in the axial and radial directions,and the deficiencies in the existing process solutions were found.Optimized.The application of internal cold iron to the casting reduces the deformation of the casting,but the effect is not very significant.The casting process scheme is optimized twice,the casting system is improved,the inner runner is added,and the inner and outer cold irons are arranged and placed at the top of the casting.The temperature distribution of the castings andcastings is more uniform,the difference in stress and strain at different locations is reduced,and the deformation of castings is reduced.Compared with before optimization,the average equivalent stress at the thin wall of the casting decreases from 150 MPa to 60 MPa,the average effective stress at the hot section decreases from 200 MPa to 70 MPa,and the average strain at the thin wall decreases from 0.014 to 0.005.The average strain at the node was reduced from 0.02 to 0.006,and the stress and strain of castings were effectively controlled.Therefore,by controlling the temperature field and the solidification rate of castings by applying cold iron and riser reasonably,the stress of the cylinder can be effectively controlled and the strain of the casting can be reduced.