Research On High-speed Deep Green Milling Of Hardened Steel

Hardened steel is widely used in the mold manufacturing industry because of its high hardness and wear resistance.The machining efficiency of hardened steel molds can be improved significantly through high-speed deep milling.However,both the temperature and milling force increase greatly and the tools are subject to rapid wear.A key question is how to lengthen the cutters’ life by effectively cooling and lubricating the cutting area.Flood cooling method is difficult to enter the tool-workpiece contact area because of the low flow rate of liquid.Thus,the cooling and lubrication effects are poor.In addition,it will also pollute the environment and affect the workers’ health during use.Minimum quantity lubrication(MQL)and oil-on-water(OoW)cooling methods are proposed in recent years,among them,the OoW method has great potential,but related research is not common at present.In this paper,both MQL and OoW cooling methods are investigated in deep milling and compared with dry cutting and compressed air cooling.The evolution process and mechanism of tool wear are analyzed.1.Dry cutting and compressed air cooling methods are discussed.Under the same amount of per tooth material removal,two deep milling experiments with different cutting speed were designed.Dry cutting and compressed air cooling will be compared from tool life,tool micro-morphology and milling force.Combining the experimental results,the cooling effect of compressed air will be analyzed.2.The high speed deep milling with MQL method is discussed.Firstly,the nozzle injection angle,gas flow rate and oil flow rate were optimized.Then,two deep milling experiments with different cutting speed were designed.The MQL method will be compared with dry cutting and compressed air cooling from tool life,tool micromorphology and milling force.Finally,the cooling and lubrication performance and mechanism of MQL are discussed from the atomization principle,effect mode of oil mist,lubrication and bearing pressure ability of oil film,and the formation and failure mechanism of oil film.3.The high speed deep milling with OoW method is discussed.Firstly,the nozzle injection angle and oil-water ratio were optimized.Then,under the two cutting parameters,OoW method will be compared with dry cutting,compressed air cooling and MQL respectively.The cooling and lubrication principles of OoW and compressed air cooling are further explained.The double-layer film structure formed by OoW droplets impinging on the tool surface is proposed and compared with the single-layer film formed by oil mist and water mist.Finally,the evolution process and mechanism of tool wear and breakage in OoW method are analyzed.