Method For Treating Metal

Author:  Price, Robert J.
Source:  US Patent 4,214,923
Doc ID:  1980009
Year of Publication:  1980
Abstract:  
An element having a chamber such as, for example, a boom of an excavator or a draft tube of a scraper is subject to torsional loading during use of the element. Torsional loading creates tensile stresses (T) on the welds of the excavator boom, which can lead to weld failure. A method for controllably treating the metal of the element includes heating the element and pressurizing the chamber, maintaining the element and chamber at a preselected temperature and pressure, respectively, and cooling the element and depressurizing the chamber. The method produces residual compressive stresses in the metal, such as in the root area of the welds of the excavator boom, for increasing fatigue life under torsional loading of the boom.