Material developments for large engine springs
Developments in production techniques have recently resulted in high quality Silicon Chrome Vanadium becoming available in larger wire diameters. The tensile strength is approximately 10% higher than conventional silicon chrome wires, allowing for a more highly stressed springs with 10% lower mass or improved fatigue life.
The superior specification wire is also ‘shaved’, ‘super clean’ and eddy current tested to ensure the optimum performance. Shaving ensures the defects that collect on the surface are removed before drawing to maximise surface quality. The super clean raw rod ensures the harmful effects of non-metallic inclusions are kept to a minimum using the latest steel producing technologies.
Using this grade, Force Technology has produced fuel injection springs of 12mm wire diameter and with an outside diameter of 48mm, giving a incredibly tight spring index of 3.0 (mean diameter/wire diameter). This is believed to be a world first for large diameter high tensile wire with such a high fatigue life requirement. The addition of Vanadium to the Silicon Chrome alloy increases the tensile strength to over 1800 MPa, giving improved fatigue life and improved relaxation properties. Accordingly weight savings and space reduction of 10% or significantly improved fatigue life are possible.
Force Technology design manager Dave Fielding comments: “Many of the high duty components we supply require very high cycle fatigue lives of over 30,000 hours. This material is a major step forward in our ability to meet our customers’ ever more demanding emission requirements, by allowing faster valve accelerations and increasing common rail pressures.”
The team at Force Technology has been working with valve quality SiCrV alloys below wire diameter 6.50mm for a significant number of years. The availability of the new grade above this size range is a major addition to the company’s product range, meeting the needs of the large engine applications in mega ships.
Using the latest manufacturing processes, Force Technology supplies global customers with the highest quality springs for use in applications including the world’s biggest cruise liners, railway locomotives, power generation and large mining trucks. The company’s unrivalled experience and focus on optimising surface residual stress guarantees the best in fatigue life, along with consistency of performance and product capability.
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