Metal treatment – Stock – Ferrous
Reexamination Certificate
2007-08-14
2007-08-14
Wilkins, III, Harry D. (Department: 1742)
Metal treatment
Stock
Ferrous
C420S044000
Reexamination Certificate
active
10195703
ABSTRACT:
A cast stainless steel alloy and articles formed therefrom containing about 0.5 wt. % to about 10 wt. % manganese, 0.02 wt. % to 0.50 wt. % N, and less than 0.15 wt. % sulfur provides high temperature strength both in the matrix and at the grain boundaries without reducing ductility due to cracking along boundaries with continuous or nearly-continuous carbides. Alloys of the present invention also have increased nitrogen solubility thereby enhancing strength at all temperatures because nitride precipitates or nitrogen porosity during casting are not observed. The solubility of nitrogen is dramatically enhanced by the presence of manganese, which also retains or improves the solubility of carbon thereby providing additional solid solution strengthening due to the presence of manganese and nitrogen, and combined carbon. Such solution strengthening enhances the high temperature precipitation-strengthening benefits of fine dispersions of NbC. Such solid solution effects also enhance the stability of the austenite matrix from resistance to excess sigma phase or chrome carbide formation at higher service temperatures. The presence of sulfides is substantially eliminated.
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Maziasz Philip J.
McGreevy Tim
Pollard Michael James
Siebenaler Chad W.
Swindeman Robert W.
Caterpillar Inc.
Wilkins, III Harry D.
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