A New Heat-treatment Process Overcomes Temperature Relaxation Problems For Spring Users

Author:  Slingsby, R.G.
Source:  Heat Treatment '79 (Conf.),May
Doc ID:  1979030
Year of Publication:  1979
Abstract:  
High-performance springs are demanding increasingly greater use of the potential available from the correct heat treatment of modern spring materials and application of current manufacturing technology. This is particularly true in the design of modern internal combustion engines where load loss of the valve springs when operating at running temperature will cause serious problems. Spring relaxation can be reduced to acceptable levels by a process known as 'hot prestressing' or 'hot scragging'. This paper discusses the mechanical and thermal processes involved in the production of high-performance springs and shows how it has been necessary to study the interaction of the variables in order to obtain an optimum compromise between fatigue life and stress--temperature relaxation. A new concept of resonant frequency fatigue testing was developed and a brief description of the design of the rig and control gear is included. The development of special-purpose machines to carry out hot prestressing on a large production scale is the logical conclusion to the work. Descriptors: Springs (elastic)-- Heat treatment; Stress relaxation; Prestressing; Shot peening; Carbon steels-- Heat treatment; Chromium vanadium steels-- Heat treatment; Stress relieving