Metal-Treating Process and Apparatus

Author:  Eugene F. Finkin
Source:  US Patent 3,599,460
Doc ID:  1968045
Year of Publication:  1968
Abstract:  
A system is disclosed for processing metallic members, to accomplish residual compressive stresses in surfaces thereof. It has been discovered that the provision of a defined fluid film over a metal member, while the member undergoes surface cold working (as by peening) accomplishes more effective peening without substantial attendant surface damage. This unexpected improvement stems from the use of a critical level and as somewhat related to the modulus of elasticity of the metal undergoing surface treatment. Specifically, for example, in peening steel, a fluid is required having a pressure coefficient of viscosity which is substantially at least 7X10 to the 15 psi. As a specific example of such a fluid, mineral oil may be employed along with oxidation inhibitors and other additives.