Process for annealing boron-containing steels and product thereof

US5022933A · kind A · utility

Assignee

• Thyssen Edelstahlwarke AG · DE

Inventors

• Helmut Brandis · Krefeld, DE
• Bernd Huchtemann · Krefeld, DE
• Peter Schuler · Karlsruhe, DE
• Dietrich Werner · Messel, DE

Key dates

• Filing date: Oct 16, 1989
• Grant date: Jun 11, 1991
• Expiry date: Oct 16, 2009

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C21D1/76
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

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.