ULTRA HIGH-SPEED CUTTING OF CAST IRONS WITH CONTROLLED NONMETALLIC INCLUSIONS BY cBN CUTTING TOOLS

本研究旨在探讨CBN刀具超高速加工铸铁的可能性。采用不同结合剂的CBN刀具对几种铸铁进行了超高速端面铣削试验(最高可达4500m/min)。对CBN刀具磨损部位的刀具磨损、切削力、切削温度以及磨损部位粘着铸铁中的非金属夹杂物进行了研究，结果表明：1.在加工高Al203含量的铸铁时，CBN刀具的前刀面和后刀面上形成了由Al、Si、Mn组成的氧化物保护层，粘着保护层后，刀具磨损变小。在刀具上观察到保护层的切割速度取决于铸铁中A1203的含量，A1203含量越高，切割速度越快。最大切割速度为4500 m/min，此时在试验中观察到了保护层。保护层的形成依赖于CBN刀具的粘结剂，含TiC陶瓷粘结剂的刀具，由于TiC易被氧化，且易与其他氧化物结合，因此保护层容易附着在刀具上。在阐明CBN刀具与保护层结合机理的过程中，明确了氮化硼BN具有由被加工材料中的Al生成AlN的作用，而附着在刀具上的AIN起到了非常稳定的保护层的作用。研究结果在一次国际会议上公布。

The aim of this study is to clarify the possibility of ultra-high-speed machining of the cast irons with cBN cutting tool. Ultra-high-speed face milling test tests (up to 4500 m/min) were carried out on several kinds of cast irons using cBN tools with different binders. Tool wear, cutting forces, cutting temperatures and non-metallic inclusions in cast irons adhered on the wear part of the cBN tools were examined.Results obtained were as follows ;1. Oxide protective layer consisted from Al, Si, and Mn was observed on the rake face and flank face of cBN tool when machining cast irons with high content of Al203, and the wear of the tool became small when the layer was adhered.2. The cutting speed at which the protective layer was observed on the tool depended on the content of A1203 in the cast iron, the higher content of A1203 the higher cutting speed. The maximum cutting speed was 4500 m/min at which the protective layer was observed in the tests.3. Formation of the protective layer depended on the binder of the cBN tool, the layer easily tended to adhered on the tool with ceramic binder including TiC, because TiC was oxidized easily and to combine with other oxides.4. In the process of clarifying the bonding mechanisms of cBN tools and the protective layer, it was clarified that boron nitride BN had the effect of making AlN from Al in work material, and the AIN adhered on the tool acted as a very stable protective layer. The results were presented at an International Conference.