2002 Fiscal Year Final Research Report Summary
Production of High Toughness Martensitic Stainless Steel using Partial Solution Treatment
| Project/Area Number |
13650801
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Metal making engineering
|
|---|
| Research Institution | Kyushu University |
|---|
Principal Investigator |
TAKAKI Setsuo Kyushu University, Faculty of Engineering, Professor, 大学院・工学研究院, 教授 (90150490)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
TOMIMURA Kouki Nisshin Steel Co.Ltd., ステンレス高合金研究部, 主任研究員
|
|---|
| Project Period (FY) |
2001 – 2002
|
| Keywords | partial solution treatment / martensitic stainless steel / carbide / grain size / toughness |
|---|
| Research Abstract |
For the purpose of developing a process for toughening of martensitic stainless steels using Partial Solution treatment, techniques for the carbide dispersion treatment and the nucleation-site control of ferrite by dispersed carbide particles were proposed. Concretely, the Partial Solution treatment (re-solution treatment in dual-phase region of austenite and M23C6 after quench-and-tempering) enabled to disperse the carbide of O.3μm in diameter homogeneously within austenite matrix and to increase the frequency of nucleation markedly in γ-α transformation on cooling. By this effect, equiaxed fine ferritic structure with random crystallographic orientation distribution was obtained and the ductility and formability of conventional steel that "high strength but low ductility" was remarkably improved. The strength-ductility balance was investigated by means of tensile testing at Kyushu University, and then it was clarified that each of uniform elongation, work hardening and necking strain was enlarged significantly. The formability of the developed steel was evaluated in terms of deep drawability at Nisshin Steel co., ltd. And it was found that the developed steel could be easily formed without the problem of cracking during the deep drawing. In addition, it is possible to perform the microstructural control only by the heat treatment without deformation process so that large-sized materials were confirmed to be produced on the practical manufacturing line without any problem. On the other hand, the mechanism of the microstructure development was revealed by using transmission electron microscopy or X ray analysis, and then the heat treatment condition was also optimized with kinetics derived from diffusion theory.
|
