Intercritical heat treatment process for toughness improvement of SA 508 GR.3 steel
US6264770A · kind A · utility
Assignees
Inventors
Key dates
| Filing date | Aug 10, 1998 |
| Grant date | Jul 24, 2001 |
| Priority date | — |
| Expiry date | Aug 10, 2018 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC21D1/18
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
The present invention relates to the heat treatment processes for manufacturing high toughness SA 508 Gr.3 steels including the intercritical heat treatment step in addition to the conventional heat treatment process, wherein the intercritical heat treatment(IHT) is added between the quenching step and the tempering step and is performed at 680.degree. C. to 750.degree. C., which is the ferrite/austenite two phase region, for 1 hour to 8 hours. When compared with the conventional heat treatment process the room temperature impact energy and the upper shelf energy of the steels manufactured by the invention increase significantly and the ductile-to-brittle transition temperature decreases. Also the present invention relates to the modified tempering processes for manufacturing high toughness SA 508 Gr.3 steels, wherein the tempering after the intercritical heat treatment is performed at the temperature lower than 635.degree. C. The modified tempering is performed to compensate the decrease of strength due to the intercritical heat treatment and to additionally increase the toughness of the intercritically heat treated SA 508 Gr.3 steels.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.