Metal treatment – Compositions – Heat treating
Patent
1989-10-16
1991-06-11
Yee, Deborah
Metal treatment
Compositions
Heat treating
148330, C21D 126
Patent
active
050229338
ABSTRACT:
Boron-containing steel products having boron contents of up to 200 ppm are obtained by an annealing process in the temperature range of between 850.degree. and 1050.degree. C. The characterizing feature of the invention is that the products are annealed in the state of equilibrium in a non-oxidizing gaseous atmosphere with a boron potential supplied by a pulverulent boron oxide source having a value such that the products retain or adsorb their boron content. The boron source is quantitatively about 100 g of B.sub.2 O.sub.3 per m.sup.3 of annealing space. In an annealing gas atmosphere mainly consisting of hydrogen, the steam partial pressure can be adjusted at atmospheric pressure in the presence of B.sub.2 O.sub.3 to the required boron activity within the range of between 10.sup.-3 to 10.sup.-5. The products can also be simultaneously case hardened during annealing. The case hardening agent can be mixed with pulverulent boron oxide as the boron source.
REFERENCES:
patent: 4615749 (1986-10-01), Satoh
Werner, "Steps in Annealing", Bor-und borlegierte Stahle, Boron and Boron Containing Steels, pp. 31, 32, 35.
Brandis Helmut
Huchtemann Bernd
Schuler Peter
Werner Dietrich
Thyssen Edelstahlwerke AG
Yee Deborah
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