Abstract: The properties of ultrahigh carbon steels (UHCS) are strongly influenced by aluminum
additions. Hardness studies of quenched UHCS-Al alloys reveal that the temperature for the start of
transformation increases with increases in aluminum content. It is shown that this change is a
function of the atomic percent of solute and of the valence state when comparisons are made with
UHCSs containing silicon and tin as solutes. The thermal expansion of UHCSs with dilute
aluminum additions shows no discontinuity in the vicinity of the ferrite-austenite transformation
temperature. This is the result of a three phase region of ferrite, carbides and austenite. The slope of
the expansion curve is higher in the austenite range than in the ferrite range as a result of the
dissolution of carbon in austenite with temperature. Processing to achieve a fine grain size in
UHCS-Al alloys was principally by hot and warm working (HWW) followed by isothermal warm
working (IWW). The high temperature mechanical properties of a UHCS-10Al-1.5C material show
nearly Newtonian-viscous behavior at 900 to 10000C. Tensile elongations of 1200% without failure
were achieved in the 1.5%C material. The high oxidation corrosion resistance of the UHCS-10Al
materials is described.
Abstract: The present requirements for the connecting rod are indicated and the fracture splitting (FS)
technologies for constructing the big end boss are reviewed. Two possibilities of FS for a high
strength Cr-Mo steel and Ti alloys were discussed. The carburized quench-temper FS connecting rod
has a superior fatigue strength with a high dimensional accuracy at the big end boss. The possibility of
using a titanium FS connecting rod was examined and proposed.
Abstract: There is a glaring need for omitting intermediate heat treatments in the manufacturing
processes of carburized parts and increasing the carburizing temperature aimed at cost reduction. It
is necessary to develop techniques to inhibit grain-coarsening since some austenite grains tend to
grow abnormally during carburizing and coarse grains have negative effects on the properties of
parts. Therefore, we developed new techniques to inhibit grain-coarsening by refining precipitates’
size and increasing their volume fraction based on the abnormal grain growth theory by Gladman.
In this study, AlN and Nb(CN) were chosen as the precipitate particles for the pinning of austenite
grain growth. And we investigated grain-coarsening behavior in several manufacturing processes of
parts. As a result, we developed anti-coarsening steels for various manufacturing processes of
Abstract: In this research, the effect of the aluminum addition to cast iron on damping property was
investigated by central vibration method, dynamic mechanical analysis, ultrasonic attenuation
measurement and impact sound method. All measurement results indicated that the addition of
aluminum improve the damping property of cast iron.
Abstract: Microstructures in a bearing steel, JIS SUJ2, have been observed and analyzed in
detail by means of transmission electron microscope and synchrotron radiation diffraction in
SPring-8. Spherodized carbides in the steel are generally recognized as spherical cementite
particles, but some of them have been clearly shown to be M23C6 type of carbide in this study.
The shapes and sizes of these two types of carbides are similar to each other. On the martensitic
matrix of the steel, it is believed to be stable at relatively low temperature, but it is also shown to
be decomposed to form cementite by prolonged aging at 383 K, which provides a reason for
decrease in hardness in standard hardness blocks, previously reported by the authors.
Abstract: The effects of chemical composition, cold rolling and subsequent annealing parameters
on the reversion of strain-induced martensite to austenite were investigated in three experimental
Mn and Si-free Cr-Ni austenitic stainless steels and two commercial Type 301 and Type 301LN
grades by optical and electron microscopy, X-ray diffraction and magnetic measurements.
Hardness and tensile tests were performed to determine the mechanical properties achieved. In
cold rolling, completely martensitic structure could be obtained in the experimental heats, but only
partially in 301 and 301LN grades at reasonable reductions. Upon annealing, in 301LN the
reversion took place by the nucleation and growth mechanism, and submicron austenite grains
were formed within a few seconds at temperatures above 700°C. In the other steels, reversion took
place by the shear mechanism, and ultra-fine grains were formed by the recrystallization of
austenite at temperatures of 900°C or above. Partial reversion resulted in an excellent combination
of yield strength and elongation in 301LN, and also in 301 such ones were attained in the reverted
structure even before any profound formation of submicron grains.
Abstract: The effect of the degree of supersaturation in a coarse-grained h-ferrite matrix on the
consequent isothermal transformation of h-ferrite to austenite at 1150‖ in a 2205 duplex stainless
steel has been investigated. The results indicate that rapid cooling (at the cooling rate 100‖/s) to
the ambient temperature after 135P‖ solution treatment of h-ferrite matrix leads to a very high
supersaturated solid solution state, which significantly enhances the formation of the intragranularly
nucleated austenite in the subsequent isothermal transformation at 1150‖. The feature of the
intragranularly nucleated austenite has been revealed; it appears that after the initial nucleation
events for intragranularly nucleated austenite, subsequent small particles of austenite can form
sympathetically on the ferrite/austenite interface.
Abstract: A new method to improve oxidation resistance of ferritic stainless steel was studied.
Increase in oxidation resistance of ferritic stainless steel with laves phase precipitation was
succeeded in addition to the conventional method such as addition of rare-earth element.
Ultra low carbon 20%Cr steels with various niobium content continuously oxidized at
1073-1173K in air. A mass gain with exposure at 1073K decreased with increasing niobium content
and saturated more than 0.1% in niobium content. In steels contained niobium less than 0.1%, mass
gain were also decreased with increase in initial ferritic grain diameter. In steels contained niobium
more than 0.1%, laves phase was observed at the ferritic grain boundary by using transmission
electron microscope. But then a mass gain with exposure at 1173K did not decreased with niobium
content and laves phase was not observed.
On the assumption that oxidation behaviors of steels contained niobium more than 0.1% obey the
parabolic law, the parabolic rate constant obtained at 1173K is similar to that controlled by grain
boundary diffusion, and parabolic rate constant obtained at 1073K is similar to that controlled by
These results suggest that precipitation of laves phase retard growth of oxide film effectively with
suppressing grain boundary diffusion of cation forming oxide film.
Abstract: Transformation of austenite to martensite during cold rolling operations is widely used to
strengthen metastable austenitic stainless steel grades. Static strain aging (SSA) phenomena at low
temperature, typically between 200°C and 400°C, can be used for additional increase in yield
strength due to the presence of α’-martensite in the cold rolled metastable austenitic stainless steels.
Indeed, SSA in austenitic stainless steel affects mainly in α’-martensite. The SSA response of three
industrial stainless steel grades was investigated in order to understand the aspects of the aging
phenomena at low temperature in metastable austenitic stainless steels. In this study, the
optimization of, both, deformation and time-temperature parameters of the static aging treatment
permitted an increase in yield strength up to 300 MPa while maintaining an acceptable total
elongation in a commercial 301LN steel grade. Deformed metastable austenitic steels containing the
“body-centered” α’-martensite are strengthened by the diffusion of interstitial solute atoms during
aging at low temperature. Therefore, the carbon redistribution during aging at low temperature is
explained in terms of the microstructural changes in austenite and martensite.