Studies On Metal Powder Injection Molding Processes Of Part Open-Close Rocker

In this paper,using 17-4PH metal powder as raw material and taking open-close Rocker Parts as the object of the MIM process characteristics.MIM technology combines the characteristics of powder metallurgy,injection molding and investment casting technology.It can produce complex metal parts.Due to the technical characteristics of MIM,the process is particularly suitable for hard alloy,expensive materials or complex shape and small parts.It was found that adding the appropriate proportion of gas-aerosolized powder to the water-aerosolized powder can improve the particle size distribution and the median diameter of the powder.When the mixing ratio is 10: 2,the particle size distribution of the powder is widened and the median diameter is about 5?m.The powder particles are appropriate in each diameter range,the best median diameter of the metal particles accounted for 43%.Adding a certain degree of activator SA can optimize the flow stability of the feedstock,developed a new MIM binder of suitable for producing open-close Rocker Parts,that is when the PW,PE,SA content for 62%,33.5%,4.5% can meet the actual requirements of all aspects of production better.The uniformity of the feedstock is affected by the mixing time and temperature.When the mixing time is less than 50 min,the metal particles is agglomerate easy.When the temperature is higher than 170 ?,the low melting point component in the binder is destroyed,so the feedstock flow intermittently.Mixing at 160 ? for 50 min can ensure the uniformity of the mixture.Software Moldflow CAE was used to simulate the three injection ports of the parts.It was found that different injection ports had influence on the filling time,density,and porosity of the parts.The experiments optimized the original simple injection process,replacing the original one area control with three area control,which can control the temperature and pressure of the feedstock more accurately.The optimized injection parameters were that the temperature in the first was 160?,in the second area and third area 155?,the pressure in the first,second and third areas was 10 MPa,11MPa and 9MPa respectively.Although the rate of the two is different in the early stage,the debinding effect is same after 7h mainly,both achieved a better debinding rate.Thermal debinding requires not only the removal residual binder,but also receives the purpose of pre-sintering,thermal debinding temperature in 820 ? can achieve pre-sinteringeffect.According the thermal analysis TG-DSC curve to optimize the thermal intermediate temperature process,at 450 ?,because of the temperature not high enough,PE can not be removed in a short time,while the temperature increased to500?,the phenomenon has been significantly improved.Sintering is an important step in the MIM processes.The sintering parameters determine the shape and quantity of porosity in the finished product.When sintering at 1300 ?,the sample still retains some pores and the pores shape are thin and long,which will affect tensile strength of the sample.At 1360 ?,because the sintering temperature is higher,grain is more conducive to grow,resulting in the sample strength is not as good as 1340?.