Yuji Yamasaki

Metal Injection Molding Process of Mo2FeB2 Boride Base Cermets

Mo2FeB2 boride base cermets produced by a novel sintering technique, called reaction boronizing sintering through a liquid phase, have excellent mechanical properties and wear and corrosion-resistances. Hence, the cermets are applied to the injection molding die-casting machine parts and so on. Metal injection molding (MIM) is a suitable processing route for the mass production of complex shaped and high performance components. In general, it is difficult for the liquid phase sintered materials to be applied to the injection molding process because significant shrinkage and deformation occur during sintering. In this study, the MIM process was applied in the production of Mo2FeB2 boride base cermets parts. We investigated that the effect of deoxidization and sintering temperature on mechanical properties and deformation of the cermets. As a result, deoxidization temperature of 1323K and sintering temperature of 1518K were suitable. The MIM products of the cermets showed allowable dimensional accuracy and the same mechanical properties as the press-sintered.

Development of High Strength Mo2NiB2 Ternary Boride Base Cermets Produced by Reaction Boronizing Sintering

The effects of V substitution for Cr to the sintering behavior of Cr containing Mo2NiB2 ternary boride base cermets and Mn addition to the mechanical properties and microstructure of the Cr and V containing cermets were investigated by using Ni-5.0B-51.0Mo-(17.5-x)Cr-xV (mass%) and Ni-5.0B-51.0Mo-12.5Cr-5.0V-(0-1.5)Mn (mass%) model cermets. 10mass%V substitution for Cr in the Cr containing cermets markedly improved transverse rupture strength and hardness from 2.27 to 2.94GPa and from 85.3 to 87.2RA respectively and refined the microstructure by retarding the progress of sintering especially at liquid phase sintering stage. Small amount of Mn addition to the Cr and V containing Mo2NiB2 base cermets significantly improved the sinterability and increased the mechanical properties of the cermets.

State-of-Art High Strength Steel Sheets for the Automotive Application

New type of IF cold-rolled high strength steels (HSSs) with the strength level of 390 and 440MPa have been developed under the chemistry of the extra-low carbon steel containing around 60ppm C with an intentional addition of niobium by hybridizing the precipitation hardening with niobium carbides and the supplemental solid-solution hardening. In this steel, Precipitation Free Zone (PFZ) nearby recrystallized grain boundaries forms during continuous annealing. This structure leads to unique mechanical properties such as lower yielding and superior anti-secondary-work embrittlement under fine grain structure strictly required for the exposed panels in Body-in-White. Principles of the unique mechanical properties of the steel are introduced related with the formation of PFZ during annealing, and the results of further approach to improve them as the state-of-the-art product, which is widely used for the exposed panels in Body in White, are introduced in the paper.

Development of High Corrosion Resistant Mo2NiB2 Boride Base Cermets for Plastic Injection Molding Machine Parts

Injection molding of corrosive super engineering plastics and engineering plastics with various fillers is conducted under severe conditions and causes corrosion and wear problems. Hence, in orde to apply Mo2NiB2 boride base cermets into plastic molding machine parts, the effects of V substitution for Cr on the mechanical properties, corrosion resistance and microstructure of Ni- 5.0B-51.0Mo-(17.5-X)Cr-XV (mass%) model cermets were investigatied. Both transverse rupture strength (TRS) and hardness increased monotonically with increasing V content and reached 2.94GPa and 87.2RA at 10.0%V, respectively. The improvements of TRS and hardness were attributed to microstructural refinement. The excellent corrosion resistance for a molten fluorocarbon resin was obtained up to 5.0%V.

Frictional Behavior of Steel Sheets in Press Forming and Optimization of Friction Testing Conditions

The typical sliding conditions at the fracture-risk positions in press forming of automotive parts were identified by FE analysis and laboratory-scale sliding tests. The investigated sliding conditions fall into three categories: the inflow sections of a steel sheet (group A), the punch shoulders in drawing (group B), and the stretch sections (group C). The frictional properties of group A and group B could be evaluated by measurement of the dynamic coefficient of friction in the flat sliding tests under a high contact pressure and at low sliding speed in each group area. The frictional properties of group C could be evaluated by the static coefficient of friction, which is measured as the primary peak in a coefficient of friction – stroke curve under the specific sliding test conditions (contact pressure: 7MPa, sliding speed: 10mm/min, tool length: 10mm).

DEVELOPMENT OF IF HIGH STRENGTH STEEL WITH FINE GRAIN STRUCTURE FOR EXPOSURE PANEL

New type of IF high strength steel (HSS) has been developed by hybridizing the grain refinement and the supplemental solid-solution hardening. Grain refinement was achieved by the fine distribution of carbide under the appropriate combination of the higher carbon content near 60ppm and niobium. Although the grain refinement is an effective method to improve the toughness of steel, this method has formability. While this steel has the fine grain structure, yield ratio is decreased due to the unique carbide distribution, and r-value is improved by the favourable texture formation. As the result, it has been clarified that a new type of 440MPa grade grain-refined IF-HSS improved the press-formability and exhibited a superior secondary work-embrittlement to the conventional IF-HSS. (A) For the covering abstract see ITRD E121867.

Characteristics of rapidly solidified mullite–zirconia ceramics prepared by plasma centrifugal atomization

Mullite ceramics containing ZrO2 were rapidly solidified to obtain amorphous ceramic powders using a plasma centrifugal atomization (PCA) method. By changing the experimental conditions of this process such as plasma gas flow rate and rotating speed of the specimen, the optimum condition to form amorphous powders was determined by XRD. Obtained amorphous powders were hot-pressed to study the characteristics of the sintered compacts.