钛合金磨削加工性的改善

Improvement of Titanium Alloy Grindability

本文分析了磨削钛合金的砂轮磨损机理,提出了改善钛合金磨削加工性的措施。试验研究结果表明,若采用所推荐的砂轮及磨削油,则可使砂轮粘附、磨削力和磨削温度明显降低,磨削比显著提高,极大地改善了钛合金的磨削加工性。

Titanium alloys have been more and more widely applied to many industrial sectors of aviation, navigation and others. Grinding titanium alloys is so difficult that people are trying their best to improve the grindability of titanium alloys at home and abroad [1][2][3]. However, when titanium alloys are ground with the usually employed green silicon carbide wheels, the grinding forces are too large, the temperature is too high and the grinding ratio will unavoidably finally deteriorate. All these undesirable phenomena reflect the inadequacy of the present understanding of mechanism of titanium alloy grinding. This paper studies the mechanism of grinding titanium alloys and brings forth some methods for improving the grindability of titanium alloys. In order to state logically the new findings of this paper, it is necessary first to give the reader a briefing on the two aspects of the research done by tho authors. Firstly, according to the characteristics of titanium alloys and the adhesive wear of the wheel, this paper selects two new kinds of vitrified CBN wheels to improve grinding processes. They are CBN/SiC and CBN/Al_2O_3 respectively, which consist of the basic abrasive CBN and the supplementary abrasive SiC or Al_2O_3. As compared with the green SiC wheel, the grinding forces will be reduced to 1/2 or 1/3, the temperature will be reduced to 2/3 and the grinding ratio will be increased by a factor of 80—100. The most important advantage obtainable with vitrified CBN wheel is that there are residual compressive stresses on ground surfaces. Secondly, a new type of grinding fluid, using EP—additive (extreme-pressure additive) has been developed. The new type of fluid can build a layer of adsorbed film with good lubricative properties to reduce the friction between the grain and the workpiece or between the grain and the chip. The wheel adhesion will be greatly decreased when the new type of grinding oil is used. Now the main findings of this paper can be stated as follows: 1. When grinding titanium alloys, it is necessary to pay attention to decreasing wheel adhesion. Wheel adhesion is the main reason for low grinding ratio because it causes adhesive wear and the fracture of grains. 2. In the case of vitrified CBN wheel, we have to select carefully the concentration of wheel in order to obtain good grindability of titanium alloys. In general, 100%—125% concentration can be selected. 3. The EP-additive grinding oil is a kind of nearly ideal grinding fluid applied to grinding titanium alloys. Its grinding ratio can be more than 10 times that of the inorganic grinding fluid of nitrite.