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The main results in Ultra-Steels research
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Research Project |
Target |
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Task force for 800MPa high-strength steels |
800MPa class thick steel plates with no alloy element & no heat preservation for welding | 1. Creation of martensitic steel with 0.77μm grain
size by multi-axial hot rolling process 2. Proposal of oxygen rich steel ( 0.2μm Grain size, several 10nm size oxide by mechanical milling & hot swaging ) 3. Development of ultra-narrow gap & high efficient arc welding ( gap width 10mm -> 5mm ) 4. Introduction of Compressive residual stress by low MS-point welling filler & post thermal treatment -> increasing life by 3 times before fatigue rupture. |
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Task force for 1500MPa high-strength steels |
Strengthening of martensitic steels for automobile parts and construction components/ Improvements in properties of delayed fracture and fatigue. | 1. The delayed fracture resistance is remarkably improved
by the microstructural control of grain boundary carbides through
thermomechanical processing. 2. New concept of controlling the mechanical properties (Young's modulus, hardness) of inclusions can drastically improve the high-cycle fatigue properties. 3. Pioneering apparatus and technique are developed for observation of microstructures and evaluation of mechanical properties of grain boundaries on a nanoscopic scale. |
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Task force for Heat Resistant Steels |
Steel pipe for ultra-super critical (USC) power plant | 1. Innovative alloying elements stabilizing microstructure
for up to long time were discovered. (Ir:suppress microstructural
recovery, Pd:precipitation of intermetallic phase) 2. Steel compositions for both sufficient creep and high oxidation resistance were designed. (low Si + Ti, Y) 3. New accelerated method to assess long-term creep strength was established on the basis of creep rate analysis. (application of creep data sheets/in traditional fitting of rupture data) |
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Task force for Corrosion-Resistant Steels |
Low-alloy weathering steels used without painting and stainless steels for seawater use | 1.Creation of ultra-high purity stainless steels (Production
of ultra-low P stainless steels containing 20 ppm P or less by reductive
dephosphorization in cold-crucible levitation melting furnace) 2. Establishment of the creation process of high-nitrogen stainless steels 3.Construction of sophisticated exposure-test facility with the capability of environmental data collection and corrosion monitoring - for the establishment of the corrosion resistance evaluation |