The Effect Of Surface Texture Of Squeeze Casting Parts

Shot blasting treatment is one of the standard procedure of the subsequent surf-ace cleaning of die casting sample,originally it is mainly used as a way of surface cleaning of metal with density much higher compared to aluminum such as steel,for which reason this treatment is also known as shot blasting cleaning.As the demand for aluminum alloy grows,shot blasting treatment has rapidly become an important procedure in aluminum alloy component production.Shot blasting treatment on aluminum alloy do function as a way of surface cleaning,but more importantly,it strengthens the performance of the surface,for example,it changes the shape and roughness of the surface of aluminum alloy components,hardens its surfa-ce,increases its surface residual compressive stress,improves fatigue strength.Few have done systematic research on the effect of shot blasting treatment on surface performance of aluminum alloy die casting sample.The test subject of this paper is ADC12 aluminum squeeze casting part,and here we did systematic research on the effect of shot blasting treatment on the surface ADC12 aluminum squeeze casting part,such as effect on surface morphology,on surface hardness,on surface roughness,on thickness of strengthened layer,and condition of surface residual stress.The result showed that,surface hardness of ADC12 aluminum squeeze casting part has improved from 100 HV to 112.7-163 HV,with roughness range Ra2.850-6.515.Roughness of the sample only improved a little bit when treated with longer duration,but improved significantly when blasted with higher speed,also the insignificance of difference between test results of treatment with steel balls of 0.45 mm and 0.25 mm means that diameter of steel balls does not matter much compared to other parameters taken into consideration here,as least in this case.With treatment duration fixed as 400 s,sample with blasting speed 900r/min showed the lowest roughness with Ra2.480,while sample with blasting speed 1500r/min showed the highest roughness with Ra6.515.Results showed that,with other configurations fixed,hardness of the test sample improves significantly with higher blasting speed,improves moderately with longer treatment duration,and only improves slightly with steel balls of higher diameter.The surface hardness of ACD12 aluminum squeeze casting part after the treatment is generally proportional to surface roughness of it.Main indicators of surface hardness of sample after shot blasting treatment are thickness of strengthened layer,status of tearing ridge,and the structure of surface microcrystals.The depth of steel pit,also the crest and trough of steel pits,indirectly reflect the thickness of strengthened layer that formed during shot blasting surface,and place with deeper steel pits always have higher surface hardness.With deeper surface steel pit,thicker strengthened layer and larger the surface defects,the variance of the surface is greater resulting in bigger Ra,which in turn means rougher surface.Hardness density gradient test result reflects the thickness of strengthened layer.The procedure of crafting processes that ends up with the thinnest hardened layer which is A and J crafting process,made a strengthened layer with lowest thickness 0.22 mm,highest thickness 1.12 mm,the harder the surface the thicker the strengthened layer,the effect of shot blasting treatment on thickness of hardened layer is just like the effect of it on surface hardness.Shot blasting treatment significantly improved surface residual compressive stress 4.3MPa,to 7.64 MPa.Surface residual compressive stress of test sample improves with higher blasting speed,larger steel ball diameter,and longer treatment,among which blasting speed is the most important factor.Shot blasting treatment did improve surface residual stress performance of the sample,but will not alter its inner structures and flaws.