Leaf spring and method of manufacture thereof having sections with different levels of through hardness
AssigneeHendrickson USA, L.L.C.
InventorsWilliam Wilson, Brian Farrell
Life of this patent
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Abstract
Leaf springs, and methods of manufacturing thereof, having first and second sections, spaced apart along the length of said leaf spring, said sections are through hardened and tempered to achieve, respectively different levels of finished through hardness, are disclosed.
Claims22
A leaf spring having at least a first section and a second section spaced apart along the length of said leaf spring, each of said first and said second sections extending across an entire cross section and along the length of said leaf spring, and said first section is through hardened and tempered to a finished through hardness and said second section is through hardened and selectively tempered to a finished through hardness that is less than the finished through hardness of said first section.
A method of selectively tempering to a finished through hardness one or more sections of a leaf spring having at least a first section and a second section spaced apart along the length of said leaf spring, each of said first and said second sections extending across an entire cross section and along the length of said leaf spring, after primary tempering of said first section has commenced, said method comprising the acts of:
- applying localized heat to a second section of said leaf spring at a temperature that is above a temperature at which the leaf spring underwent primary tempering and below austenitic transformation temperature,
- maintaining said localized heat to said section for a period of 20 seconds or longer, and
- rapidly cooling the leaf spring from a temperature of at least 50° F. above the temperature at which tempered martensite embrittlement can occur in the leaf spring to a temperature less than 150° F. by quenching the leaf spring with an aqueous solution to reduce heat migration into any section to which said localized heat was not applied, wherein a resulting finished through hardness of said second section is lower than a finished through hardness of said first section of the leaf spring.
Dependencies are inferred from the claim text.