Research On Rapid Casting Process Of Valve Body Based On Selective Laser Sintering

Stainless steel valve bodies possess excellent properties such as high strength,heat resistance,and corrosion resistance,and play an important role in the petrochemical industry.However,complex valve bodies face the challenge of long mold preparation cycles and difficulty in removing defects in the current investment casting production.Selective Laser Sintering(SLS)technology can achieve direct molding of molds,effectively reducing the preparation cycle.However,the current molding accuracy of complex molds is low due to thermal deformation.Balanced solidification technology can target hot joints repair,but current research focuses on simple and regular parts,and cannot accurately reflect the casting situation of complex parts.Therefore,it is urgent to combine the advantages of SLS and balanced solidification technology to carry out rapid casting process improvement research for valve bodies.This paper takes defective castings as the research object,and adopts a combination of simulation and experiment for the problems of low molding accuracy of valve body molds and difficulties in filling and shrinking of casting defects.Firstly,the characteristic structure of the valve body is analyzed to explore the deformation law of SLS molding of transverse cylinder and flange base plate,and to find the means of dimensional error compensation.After that,with the goal of eliminating isolated hot joints,the multi-pocket combined pouring system is designed,and the relationship between the two is obtained when complementing and shrinking different hot joints by changing a single variable in the deviation factor and modulus ratio to achieve the purpose of overall sequential solidification composed of local dynamic solidification.On this basis,orthogonal tests are designed around pouring temperature,shell preheating temperature and pouring time to obtain the optimal process parameters and conduct experimental verification.The results show that: 1)the whole transverse cylinder is oval deformation tendency,when the inner diameter is fixed,the maximum deviation value first decreases and then increases with the increase of wall thickness,and the addition of stiffeners can reduce the deviation by up to about 50%;The deviation value of the outside of the flange floor decreases with the decrease of the internal filling rate,and the dimensional deviation is reduced by about 22% by changing the filling method.2)Single riser complement single thermal joint,when the minimum modulus ratio is 0.8,effective compensation can be achieved within the deviation factor of 2.2;when the maximum deviation factor is 2.4,the riser with the minimum modulus ratio of 1.21 can be used to achieve effective contraction.Under both working conditions,with the increase of the modulus ratio,the maximum deviation factor increased downward.3)Optimal process parameters 1 640°C pouring temperature,1 100°C preheating temperature,10 s pouring time.This process parameter guides the casting of the valve body,and after penetration testing,the casting defect disappears.