Study On Micro-Structure And Grinding Mechanism Of Steel Slag Abrasive

In the steelmaking industry,the amount of steel slag is about 10%～15%of crude steel output,and its comprehensive utilization rate is less than 30%.Therefore,using steel slag to produce high value-added products has great significance for environmental protection and the development of the iron and steel industry.Steel slag belongs to the category of silicate abrasives,which has received widespread attention and research due to their environmental protection,reliable safety,moderate hardness,and low cost.However,they need to be crushed and carefully selected,and their application is not ideal.In this subject,steel slag abrasives are prepared by gas quenching process,the microstructure and grinding performance of steel slag abrasives are studied,and the micro process of removing surface materials from workpieces by abrasives is simulated.The influence of process parameters on the surface quality of the workpiece is analyzed,which provides a research basis for the wide application of steel slag abrasives in the field of grinding processing.Firstly,steel slag abrasives were obtained by crushing molten steel slag with high-pressure and high-speed gas jet,and the properties,such as beading mechanism,microstructure,mechanical properties,thermal stability,and chemical stability,of steel slag abrasives were researched.The main results are as follows:the bead formation process is divided into five stages:disturbance wave,filiform or film formation,filiform or film fragment fracture（main stage）,secondary fracture,and particle aggregation and solidification.Steel slag abrasives present a monodisperse spherical shape,with ball milling toughness of 47.4%,microhardness of 722 HV,and 37%～45%in porosity.When the temperature is elevated to 1000℃,the weight loss rate of steel slag abrasives is about 1.2%,which reflects moderate hardness、good toughness and thermal stability.The study on chemical stability reveals a small amount of velvet and rod-like hydration products on the surface of steel slag abrasives in water.After being corroded by HCl,metal elements such as Mg,Al,Ca,and Fe are precipitated（dissolved by H⁺）due to the ion exchange mechanism,obvious gullies and holes are formed on the surface.Following the corrosion through Na OH,the[Si O₄]tetrahedral skeleton net structure experiences depolymerization due to OH^-increases,which results in the structural damage.After the corrosion using grinding fluid,the surface microstructurebasically unchanged,so the steel slag abrasive has good chemical stability in grinding fluid.Secondly,the micro-grinding mechanism of abrasives on the workpiece was simulated by finite element simulation,and the effects of grinding speed,grinding depth and friction coefficient on the wear resistance and stability of steel slag abrasives were analyzed.The results show that in the grinding process,the free steel slag abrasives can complete micro-cutting on the surface of the workpiece through free sliding and rolling.After steel slag abrasive treatment,the surface hardening degree of aluminum and copper workpieces are higher than that of Si O₂abrasive.The predicted hardness value of the workpiece surface presented the same trend as the experimental hardness value.With the increase of grinding speed,the stability and wear resistance of sliding and rolling steel slag abrasives decrease.The stability and wear resistance of sliding steel slag abrasives are influenced little due to the change in the friction coefficient and grinding depth,and a greater friction coefficient and a smaller depth contributes to the better stability and lower wear of rolling steel slag abrasives.Finally,in order to further verify the effectiveness of abrasive and workpiece grinding simulation,the effects of steel slag abrasive and traditional abrasive on workpiece surface quality were analyzed through grinding experiments.The results show that the influence of steel slag abrasives and traditional abrasive on the surface quality of copper and aluminum workpieces is sorted,in descending order,as Si C abrasives,Al₂O₃abrasives,steel slag abrasives,and Si O₂abrasives.The hardness of Si C abrasive and Al₂O₃abrasive is large,suitable for grinding the workpiece with higher hardness and finishing process,while the hardness of steel slag abrasive and Si O₂abrasive is moderate,which can effectively remove scratches and burrs on the surface of the workpiece,suitable for roughing process.The impact of steel slag abrasive on the surface quality of the aluminum and copper alloy workpieces are better than that of Si O₂abrasive,and the grinding effect on the aluminum alloy is better than that of copper alloy,which is consistent with the variation law of finite element simulation.At the same time,the surface quality of workpiece can by appropriately lengthening the grinding time of steel slag abrasives,elevating the solid content of abrasives,and reducing the abrasive particle size.Due to the friction and compression between steel slag abrasive and the workpiece,the surface material of the steel slag abrasive undergoes micro fracture and damage,resulting in a minor number of pits that remain in their original form.Therefore,the steel slag abrasive has good self-sharpness and can be recycled and used,which realizes the purpose of treating waste and transforming waste into treasure.