低温CO_(2)辅助PCD刀具硬车削轴承套圈的装置及试验研究

Low Temperature CO_(2)Assisted PCD Tool Hard Turning Bearing Ring Device and Experimental Research

目的降低PCD刀具硬车削轴承套圈时的刀具磨损。方法采用低温二氧化碳内冷辅助PCD刀具切削来抑制刀具磨损。搭建低温二氧化碳冷却装置,开展液态二氧化碳的冷却试验,分析二氧化碳的冷却规律;开展低温切削试验,通过人工热电偶测温法对参考切削温度进行测量,并且研究不同入口压强参数下轴承套圈的表面粗糙度和刀具磨损变化情况,验证低温二氧化碳冷却辅助PCD切削轴承套圈的有效性。结果二氧化碳在恒定压力(1.2 MPa)下的冷却规律可以分成起始、稳定、失效3个阶段,稳定阶段的流量大小为1000g/min,冷却温度可以保持在-59℃不变。二氧化碳在不同入口压力(0.8~1.4MPa)下冷却时,入口压力越小,冷却温度越低。在不同入口压力(0.8~1.4 MPa)下进行低温切削,0.8、1、1.2、1.4 MPa时的最大参考切削温度分别为-41、-28、-30、-28℃,加工表面的粗糙度值分别为0.071、0.074、0.109、0.129μm,后刀面最大磨损量分别为176.58、171.67、270.26、261.17μm。结论入口压力为0.8 MPa和1 MPa时,二氧化碳冷却效果较好,无论是参考切削温度,还是加工表面的粗糙度值和刀具磨损都处于较低水平,低温冷却辅助PCD刀具硬车削轴承套圈时可有效降低刀具磨损。

The machining quality of bearing casing plays a decisive role in the service life and performance of the bearing.The hard cutting process method using polycrystalline diamond(PCD)tool cutting bearing casing has the advantages of high processing efficiency,high processing accuracy,green and no pollution.But the tool wear of PCD tool is very violent processing ferrous metal.To reduce the tool wear of PCD tool in hard turning of bearing rings,in this paper,a low-temperature carbon dioxide internal cooling assisted PCD tool cutting was used to suppress tool wear.A low temperature carbon dioxide cooling device was built to provide a stable low-temperature carbon dioxide jet for cutting tests.This cooling device includes a temperature sensor,quality sensor,pressure reduction valve and needle valve for temperature detection and flow regulation during testing.Then the cooling test of liquid carbon dioxide was carried out to analyze the cooling law of carbon dioxide.Carbon dioxide low-cooling test is divided into two parts:continuous cooling test and segmented cooling test.The cooling law of carbon dioxide under constant pressure(1.2 MPa)during the continuous cooling test can be divided into three stages:initiation,stability and failure.The initiation stage of carbon dioxide amount is relatively sufficient,and the cooling temperature is minimally reduced to-63℃.The cooling temperature then rises slowly for a period and remains stable,and the cooling phase begins to enter a stable phase,during which the cooling temperature almost no longer changes.Finally,the supply of carbon dioxide is insufficient,leading to the carbon dioxide inlet pressure can not remain stable,and the cooling effect is very poor.This stage is the failure stage.The flow rate in the stable stage is 1000 g/min,and the cooling temperature remains unchanged at-59℃.The segmented cooling test cooled carbon dioxide at different inlet pressures(0.8-1.6 MPa)and found that the lower the inlet pressure within the measured range,the lower the cooling temperature.Therefore,in the cryo-temperature cooling process,maintaining a small liquid carbon dioxide flow rate can get an ideal cooling effect.However,during the actual cooling experiment,when the inlet pressure of the internal cold vehicle blade is less than 0.8 MPa(the flow rate is less than 500 g/min),a large number of solid-state carbon dioxide particles will appear at the exit,which is easy to cause the pipeline blockage and the flow instability.Therefore,in the process of cryogenic cooling,keeping the inlet effect within 1-1.2 MPa can both obtain a stable cooling effect and avoid the waste of cryogenic coolant.Low-temperature cutting was carried out under different inlet pressures(0.8-1.4 MPa).The maximum reference cutting temperatures at 0.8 MPa,1 MPa,1.2 MPa and 1.4 MPa were-41℃,-28℃,-30℃and-28℃,respectively.The roughness values of the machined surface were 0.071μm,0.074μm,0.109μm and 0.129μm,respectively.The maximum flank wear was 176.58μm,171.67μm,270.26μm and 261.17μm,respectively.When the inlet pressure was 0.8 MPa and 1 MPa,both the reference cutting temperature and the roughness value of the machined surface and the tool wear were at a low level.The low temperature cooling assisted PCD tool can effectively reduce the tool wear when hard turning bearing rings.