Studies on Grind-hardening with the Aid of Laser Conditioning of Grinding Wheel Surface

一般来说，磨削热会对工件造成各种类型的热损伤，如燃烧、裂纹、相变等。在本研究中，将磨削操作视为。一种叫做研磨硬化的热处理工艺。这种新的热处理方法使钢的表层由奥氏体相变为马氏体。在不同进给速率下进行了外圆磨削试验，当进给速率大于40μm/s时，形成了硬度为700HV的马氏体组织。硬化层深度随进给速度的增加而增加。在SCM435铬钼钢的切削磨削中，获得了约0.16 mm的硬化层。火花磨削可去除磨削面层的氧化膜，使工件表面光滑，圆度好。作为第二种方法，激光束被用作青铜结合剂金刚石砂轮的非接触式热修整工具。脉冲nd:YAG激光束在法向对准并聚焦在车轮表面，轴向进给线性工作台，该运动与车轮旋转、激光脉冲频率和脉冲持续时间相协调，使光束覆盖整个车轮表面，仅通过激光照射去除部分粘结材料，并发生熔化和汽化。为了有效地去除手料，需要在激光照射点上喷射空气射流，使熔融粘结剂在再次凝固前被吹走，从而减少金刚石颗粒的损伤，如微裂纹或石墨化。为了评价激光修整砂轮对工程陶瓷的磨削性能，进行了激光修整砂轮的切入磨削试验，其磨削力与普通修整砂轮几乎相同，且磨削力基本保持恒定，每单位切割宽度所去除的砂轮量为50 mm3/mm，这表明金刚石磨粒在结合剂中锚定牢固，没有热退化，因此，在适当的修整条件下，激光修整效果是可以预期的。为了便于实际应用，设计了激光-空气一体化头，其中激光束和空气射流在同一轴上射出。激光修整砂轮磨削时，磨削面与常规修整砂轮磨削面基本相同。少

In general, grinding heat canoes various types of thermal damage to the workpiece, such as burning, cracks, and phase transformation. In this study, the grinding operation is regarded as. a heat treatment process called Grind-hardening. This new heat treatment method enables the phase transformation from austenite to martensite in the surface layer of steels. The cylindrical grinding tests at several infeed rates are carried out A clear hardened layer is observed, where the martensitic structure is formed having the hardness of 700HV when the infeed rate is larger than 40μm/s. The depth of hardened layer increases as infeed rate increase. The hardened layer of approximately 0.16 mm is attained in plunge grinding of chrome-molybdenum steel SCM435. The oxidized film at the ground surface layer can be removed by the spark-out grinding and this process makes the surface smooth and good circularity of the workpiece.As the second approach, laser beam is used as a noncontact thermal dressing … More tool of a bronze bond diamond wheel. The pulsed-Nd:YAG laser beam is aligned in the normal direction and focused on the wheel surface The linear stage is fed in the axial direction and this motion is coordinated with the wheel rotation, laser pulse frequency and pulse duration so as to cover the overall wheel surface by laser beam The bond material is partially removed by laser irradiation only, in which melting and vaporizing take place. In order to efficiently remove the hand material, it is necessary to spray air jet on the laser irradiating spot so as to blow away the molten binder before it solidifies again less damage of diamond particles such as micro-cracks or graphitization is observed. In order to evaluate the grinding performance of a laser-dressed wheel, the plunge grinding tests of engineering ceramics are carried out The grinding forces are almost the same as the ordinary dressed wheel, and they are roughly kept constant up to 50 mm3/mm in stock removed per unit width of cut This shows that the diamond grits are anchored firmly in the bond without thermal deterioration_ Consequently, the effective laser dressing is expectable with the appropriate dressing conditions. For the purpose of practical use, the integrated laser-air head is designed in which laser beam and air jet are shot on the same axis. In grinding with the laser-dressed wheel, the grinding faces are almost the same as those for the conventionally dressed wheel. Less