THE HEAT-TREATING OF BRAZED FITTINGS FOR AIRCRAFT

A tendency exists in most shops to assume that brazed joints cannot be successfully heat-treated. As a consequence, many fittings used in aircraft work and assembled by brazing smaller parts together are finished and installed without being heat-treated after the brazing operation. This practice causes parts to be used that not only do not develop the available strength of the material, but which are in some cases, under internal stress due to the heating in the brazing operation. Recent experiments made at the Naval Aircraft Factory show that the assumption mentioned is entirely erroneous. The author considers this matter with a view to specifying the use of steels and brazing spelters which will permit the subsequent or perhaps the simultaneous heat-treatment of the parts.

The spelters required, their melting and approximate softening points to avoid the destruction of the brazed joint during heat-treatment, are discussed and data concerning them and the steels likely to be required for aircraft parts are presented in accompanying charts. Heat-treatment is then taken up and notes regarding the heat-treating of the tube struts used in aircraft work are given, the conclusion reached being that nothing is gained by the use of high-strength steel where the length divided by the least radius of gyration exceeds about 100.