| Titanium alloy bar products is the key economic areas of engineering materials with high mechanical strength and toughness,along with good cold processing properties to meet the requirements of the subsequent processing.However,due to the existence of cracks or fracture defects in the production process of titanium alloy products,the yield of the products is low.In this paper,the production of cracks is predicted by the damage analysis,which reduces the loss rate in the titanium alloy production process.In this paper,a reasonable three-roll TC4 bar process is developed.The damage value of the bar is simulated by finite element software.The crack-sensitive zone is predicted during the rolling process and the influence of different process parameters on the maximum damage value of the bar is studied.The grouting system was improved and the relevant tests were carried out on the three-roll hot rolling mill.The samples with good geometric dimensions and good surface quality were obtained,followed by microscopic observation.The specific research contents are as follows:(1)Using Deform finite element simulation technique,the damage distribution in the three-roll hot rolling process was simulated.By contrast,the area with the largest damage was determined,that is,the area of contact with the roll.The effects of roll angle,friction factor and temperature on the maximum damage value of bar are compared.The theoretical basis is provided for the optimization of the subsequent parameters.The CA model is used to linearly integrate the dislocation density model and the dynamic recrystallization model,Which further simulated the evolution of the grain in the largest damage area.(2)Based on the theory of fracture mechanics,the Ayada damage model suitable for low temperature and isothermal temperature is optimized.Considering the rolling temperature(850℃,900℃,950℃,1000℃),the strain rate(0.01s-1,0.1s-1 1s-1),the mathematical model of the cumulative damage of TC4 titanium alloy is deduced.The deviation between the simulated damage value and the calculated damage value is compared with the maximum deviation of 9%.(3)The stability of the continuous casting is the key to the successful deformation of the product.On the basis of the traditional pore type,the orthogonal analysis method and the finite element simulation are used to reduce the cross-section temperature gradient and reduce the surface crack.Multi-line Triangle Pass System to determine the first pass,the third pass raised the best geometric size of the groove,that is,the first pass long axis length 4.30 mm,short axis length 0.80 mm,the second Road long axis length 3.34 mm,short axis length 0.80 mm.(4)The TC4 bar rolling test was carried out on the three-roll hot rolling mill,and the samples with good geometric dimensions and good surface quality were obtained,and the superiority of the new type was confirmed.After the microstructure observation,Three times,the bar organization began to undergo organizational changes,that is,from the thin strip gradually transformed into equiaxed,which is consistent with the finite element simulation results.It is reasonable to describe the process parameters and equipment parameters of this paper,so as to provide reliable technical basis for rolling of similar metal materials. |
