Method of carburizing the inner surface of a steel valve seat
AssigneeRobert Bosch GmbH
InventorsJosef Hack, Bruno Schafer
Life of this patent
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Abstract
To carburize the inner surface of hollow, narrow work pieces, such as valve seats in blind bores, and avoid the use of salt baths which have residues containing Prussic acid, a mandrel is made fitting with little clearance in the order of 0.1 mm into the blind bore, and having a carbon content in the range in which carbon is yielded which is higher than the carbon content of the work piece to be carburized, the mandrel or carburizing element having a surface which fits or matches the surface of the work piece with the clearance. The work piece and the carburizing element are heated to carburizing, incandescent temperature and the carburizing element is removed from the work piece after carburizing thereof.
Claims7
A method of carburization hardening the steel surface of a valve seat situated in a bore of a steel valve body including the steps of
- providing a carbon yielding carburizing body (5, 26, 29) in form of an elongated pin-like element having a shape at least approximately matching the shape of the valve seat to be carburized having a cross section which is slighty less than the corresponding cross section of the valve seat and bore, and which has a carbon content in the region where said valve seat is to be carburized which is higher than the carbon content of the steel to be carburized in the valve seat region of said valve body, in order to yield carbon to said valve seat region steel;
- locating said carburizing pin-like element (5, 26, 29) within the valve seat and bore closely adjacent to the valve seat region steel;
- and heating the valve body and the pin-like element (5, 26, 29) inserted within the valve seat and bore thereof to glowing or incandescence temperature.
Dependencies are inferred from the claim text.