ENAMEL GLASSES AS LUBRICANTS FOR FORMING SHEET METAL

The NEED OF THE AIRCRAFT INDUSTRY for structural alloys having high strength‐to‐weight ratios above 500°F. and the availability of new titanium alloys having these properties has presented some new and difficult manufacturing problems. Examination of representative titanium alloys over a wide temperature range shows that at room temperature the yield strength is high and that the difference between yield and ultimate strengths is quite small. This presents difficult conditions for sheet metal forming operations such as drawing, hammer forming, and drawbench forming. Since a high percentage of aircraft parts are formed from sheet metal, and since good formability is of great importance, consideration has been given to forming these parts at elevated temperatures where the properties affecting forming are more suitable. Above 800°F the yield strength of the alloy is much lower and the spread between yield and ultimate is greater. Exploratory work on the forming of titanium alloys at 800°F–1,400°F has shown formability to be satisfactory. However, serious galling of the titanium alloys occurred and hitherto conventional forming lubricants were proved quite unsatisfactory due to temperature. The severe galling was not only ruinous to the parts formed, but scored the dies badly and necessitated refinishing of the dies between operations. This galling occurs whenever titanium alloys rub against themselves or other metals.