Tool Wear And Its Effect On Surface Integrity In Hard Milling H13Steel

The development of super-hard cutting tool materials and high performance machine tools bring the application of HSM (high speed machining). As a branch of HSM technology, hard milling is attracting considerable worldwide interest from die and mold industries. Compared with the traditional grinding method, directly milling dies and molds at their hardened state could greatly reduce grinding time, shorten the mould manufacturing process, decrease heat treatment deformation and machining cost. AISI H13steel belongs to hot work mold steels, which is widely used at home and abroad. High temperature, high pressure and chock make the service conditions of die and mold components very harsh. The surface integrity of workpiece including surface roughness, microstructure, residual stress, work hardening and phase change must meet certain demands. Tool wear not only makes cutting tools loss the cutting ability, but also changes cutting edge geometry, increases cutting forces and cutting temperature, which deteriorates the cutting environment and affects the surface integrity. However, comprehensive understanding of the influence of tool wear on surface integrity in hard milling is insufficiency. Only a sufficient understanding of the influence of tool wear on surface integrity could we make full use of the performance of the cutting tool, and reduces cutting tool cost, and better control the surface integrity, and obtain reliable and stable mould performance. In this paper, the effect of cooling/lubrication, tool wear and its effect on surface integrity of workpiece in hard milling AISI H13steel are studied systematically.The effects of dry cutting, minimum quantity lubrication (MQL), and chilled oil-gas cutting on cutting force, the surface roughness and the residual stress are analyzed. The application of MQL and chilled oil-gas medium could decrease the cutting forces and surface roughness, increase the residual stress. Improving function of the cooling and lubrication media can be affected by cutting parameters. The friction and wear performance of AISI H13/cemented carbide are studied. The worn surface morphology of cemented carbide is inerratic, and the attrition wear, adhesion wear and oxidative wear are found in the cemented carbide surface. The tool wear morphology and mechanism in hard milling AISI H13is analyzed. Coating damage and adhesion wear is the main mechanism. The cutting tool life with the chilled oil-air medium is more than twice as much as with dry cutting. The flank wear is the main failure mode when dry cut, and the large flaking on rake surface of tool when cut with the chilled oil-air medium.The influence of tool wear on surface integrity is analyzed. With the progress of tool wear, the geometric texture of processing surface gradually deepens. When dry milling, there are large fluctuations of the surface roughness in the initial stage of the tool wear, and the surface roughness and microhardness remain stable in the stable wear stage of the tool wear and rapidly increase in the sharp wear stage. Surface plastic deformation always occurs during the whole tool wear process. The drastic wear of the flank surface on cutting tool produces white layer in workpiece surface. But there is no phase change by X-ray analysis.In this paper, the effect of cooling/lubrication tool wear and its effect on surface integrity of workpiece in hard milling AISI H13steel are studied, which supply technical support for improving.workpiece surface quality, hard milling technology promotion and application.The work is sponsored by the Shandong Provincial Natural Sciences Foundation (Y2008F41), the Project Sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars (State Education Ministry2010-609) and the Independent Innovation Foundation of Shandong University (2009TS028).