Investigation On The Manufacturing Process Of Steel Shot By Water Jet

Steel shots were produced by water jetting technique and relevant process parameters were as follows:molten steel weights percentage elements was 0.85-1.20 %C,0.50-1.20%Si,0.60-1.20%,Mn≤0.035%S and≤0.035%P;the pouring temperature of molten steel was 1550-1570℃;the upward tilt angle of flowing device was 10-15 degrees;water flow velocity was 7m/s;the speed of molten metal off liquid holes was 2.8m/s.Utilizing Produced steel shots,the paper researched the microstructure of steel shots,statistically analyzed the particle size of steel shots and the distribution rule of cavity defect,theoretically analyzed the formation mechanism of steel shots defect,and optimized the production process of steel shots.SEM results revealed that the inner void of steel shots was classified as porosity and shrinkage.By analyzing the statistic results,it could be found that the diameter of steel shots was mainly less than 2.5mm and the cavity ratio tended to increase with the increasing in shots size.In addition,the cavity ratio also increased with the casting time,which indicated that the voids mainly appeared at the end of casting process.In the course of pouring,metal droplet was impact by flow,rapidly cooled from surface to inner,when molten steel is not sufficient supplement the liquid shrinkage and solidified shrinkage,it would result a large or small holes.Droplets would give rise to rotation due to the impacts of water flow,resulted in droplets surface fully contact with flow,made the surface temperature equilibrium,so the droplet solidification rate was balanced from surface to inner,so that liquid contraction and solidification shrinkage would cause the emergence of one or a few relatively large holes in the midsection of steel shots,it was shrinkage cavity.Because not every metal droplet and water droplets could fully contact,the metal droplets contacting not fully would form temperature gradient,the solidification rate of metal droplets various parts was different from surface to inner,so it would be easier to form more small holes,or scattered distribution,or linked up,It was shrinkage porosity.According to the formation mechanism of steel shots defects,the orientation relation of flow and metal liquid、the section shape of metal nozzle、water outlet installations had been optimized to obtain better production effects.Practice had proved that these optimized terms could effectively reduce the defects of steel shots, furthermore improve the production efficiency.