| Budget Amount *help |
¥3,550,000 (Direct Cost: ¥3,100,000、Indirect Cost: ¥450,000)
Fiscal Year 2007: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
Fiscal Year 2006: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
Effects and mechanisms in MQL cutting are investigated by use of an intermittent turning process and by a friction test apparatus which is designed for measuring friction farce between a freshly formed surface and tool material in plastic contact condition. Cutting tests are conducted using two types of lubricant which have difference in lubricity and in speed range from 100 m/min to 400 m/min. In the case of aluminum alloy cutting, experimental results suggest that the lubrication mechanism of the minimal quantity lubrication considerably changes depending upon the lubricant types and the temperature on the tool face. If ester type lubricant is used and tool surface temperature can be suppressed below certain transition temperature of friction, large reduction in a frictional force can be obtained at an initial stage of intervals of intermittent cutting This result also supports the fact that, if water mist simultaneously supply into the cutting point in the MQL cutting with the ester
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type lubricant, large reduction in cutting force can be obtain. That is, requirements for good lubricity in aluminum alloy cutting are chilling the tool face down to the transition temperature of friction and using the lubricant with high polarity which possesses high transition temperature of friction.
On the other hand, in the case of machining difficult-to-cut material such as austenitic stainless steel, the ester type lubricant merely exhibits lubrication effect by the MQL method. This indicates that the considerable temperature rise due to low diffusivity of heat of work material disable the lubrication effect of adsorption layers of the ester type lubricant In this case, another mechanism of lubrication which acts at a high temperature condition might be needed even in the MQL cutting. Generally, metal working fluid for difficult-to-cut material contains chlorine-, sulfur-or phosphate-type additives to react with the work material at the interface. Even if using sulfurized fatty oil as additive in MQL cutting, which possesses relatively low environmental burden among them common additives, little improvement can be obtained. In the MQL, it can be considered that reaction layers from sulfurized fatty oil is insufficient to reduce the friction because total quantity of additive is very small One of the solutions to obtain the good lubrication effect is to increase the adsorption and reaction site on the surface. It was found that iron oxide enhances adsorption and reaction between iron and sulfur-type additive. accordingly enhancement of surface oxidation can be considered to be a good method to improve the lubricity Prom the viewpoint of the oxidation enhancement, to supply water mists simultaneously is adopted for the MQL cutting of the difficult-to-machine material In this situation, the water mists easily evaporate and be superheated due to cutting heat, and then, promote surface oxidation. EPMA analyses supports surface oxidation and friction test indicates good lubricity. In actual cutting test, cutting force reduction about 10% can be obtained with the water mists adding to the MQL. Less
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