Process of treating a stainless steel matrix
AssigneeNOVA Chemicals (International) S.A.
InventorsLeslie Wilfred Benum, Michael C. Oballa
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Abstract
Heat resistant stainless steel may be treated in a low oxidizing atmosphere in a heat/soak-heat/soak sequence to deplete its surface of Ni and Cr which tend to catalyze coking of hydrocarbons in contact with the surface of the stainless steel, and enrich it with elements which are inert to coke formation. Parts made of stainless steel, such as furnace tubes or coils, treated in accordance with the present invention when used have a significantly reduced rate of catalytic coking.
Claims13
A process for treating stainless steel comprising from 13 to 50 weight % of Cr, from 20 to 50 weight % of Ni and at least 0.2 weight % Mn, in the presence of a low oxidizing atmosphere comprising:
- i) increasing the temperature of the stainless steel from ambient temperature at a rate of 20° C. to 100° C. per hour until the stainless steel is at a temperature from 550° C. to 750° C.;
- ii) holding the stainless steel at a temperature from 550° C. to 750° C. for from 2 to 40 hours;
- iii) increasing the temperature of the stainless steel at a rate of 20° C. to 100° C. per hour until the stainless steel is at a temperature from 100° C. to 1100° C.;
- and
- iv) holding the stainless steel at a temperature from 800° C. to 1100° C. for from 5 to 50 hours.
Dependencies are inferred from the claim text.