Annealing of carbon steels in a pre-heated mixed ambients of nitrogen, oxygen, moisture and reducing gas
US5254180A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 22, 1992 |
| Grant date | Oct 19, 1993 |
| Priority date | — |
| Expiry date | Dec 22, 2012 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC21D1/76
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
An improved process for producing high-moisture containing nitrogen-based atmospheres suitable for oxide and decarburize annealing of carbon steels from non-cryogenically generated nitrogen is presented. These nitrogen-based atmospheres are produced by 1) mixing non-cryogenically generated nitrogen containing less than 5.0 vol. % residual oxygen with a specified amount of hydrogen, 2) humidifying the gaseous feed mixture, 3) feeding the gaseous mixture into the heating zone of a furnace through a diffuser, and 4) converting in-situ the residual oxygen present in it to moisture. According to the present invention, the total amount of hydrogen required for producing suitable atmospheres can be minimized by simultaneously humidifying the feed gas and controlling the residual oxygen level in it. The key features of the present invention include a) humidifying the feed gas prior to introducing it into the heating zone of a furnace operated above about 600.degree. C., b) selecting the level of residual oxygen in the feed gas in such a way that it minimizes hydrogen consumption, and c) using enough amount of hydrogen to convert completely the residual oxygen present in the feed gas to moi…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.