Subscale reaction strengthening of low carbon ferrous metal stock
AssigneeUnited States Steel Corporation
InventorsLee J. Cuddy, Harry H. Podgurski
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Abstract
Low carbon, low alloy, ferrous metal stock containing from 0.05 to 0.5 wt. percent uncombined group IVB or VB metal, is strengthened by a procedure comprising; gas phase nitrogenation at temperatures below 590.degree. C to form extremely fine dispersions of such group IVB or VB metal nitrides, followed by an additional treatment for removing excess nitrogen in solid solution.
Claims14
A process for the diffusion-reaction strengthening of ferrous metal stock consisting essentially of, in wt. %, 0.001 to 0.02% carbon, 0.02 max. % nitrogen, 0.02 max. % oxygen, 0.05 to 0.5% available strong nitride forming metal, selected from the group IVB and VB elements and mixtures thereof, with the balance iron and residual steelmaking elements, which comprises,
- at a temperture within the range of 450.degree. to 590.degree. C, nitrogenating said stock for a time at least sufficient to diffuse a nitride subscale front to a distance from a stock surface, which is at least 25% of the thickness of said stock, said nitrogenation being conducted in an atmosphere having a nitrogen activity (i) sufficient to diffuse nitrogen into said stock and form said subscale front, but (ii) below that which will lead to the formation of iron nitride during said nitrogenation.
Dependencies are inferred from the claim text.