Koh-ichi Sugimoto

Shinshu University | Shindai · Department of Mechanical Systems Engineering

The damage properties in the shear-punched surface layer, such as the strain-hardening increment, strain-induced martensite fraction, and initiated micro-crack/void characteristics at the shear and break sections, were experimentally evaluated to relate to the stretch-flangeability in three types of low-carbon high-strength TRIP-aided steel with di...

To analyze various types of cold formability in TRIP-aided polygonal ferrite (TPF), annealed martensite (TAM), and bainitic ferrite (TBF) steels, the effects of the mean normal stress on the strain-hardening, strain-induced martensite transformation, and void-formation behaviors were investigated. The strain-hardening behavior was influenced by pos...

The effects of partial replacement of Si by Al on the microstructure, tensile properties, and Charpy impact toughness were investigated using 0.2%C-Si/Al-Mn-Cr-B TRIP-aided martensitic steels to promote the application of galvanized third-generation ultrahigh- and high-strength steels. The impact toughness was related to the microstructural and mec...

The effects of partial replacement of Si by Al on the microstructure, tensile properties, and Charpy impact toughness were investigated using 0.2%C-Si/Al-Mn-Cr-B TRIP-aided martensitic steels. The impact toughness was related to the microstructural and mechanical properties. The partial re-placement decreased the volume fraction of retained austeni...

Partial replacement of Si by Al improves the coatability (or galvanizing property) of Si-Mn advanced high-strength steel (AHSS) sheets. In this paper, the effects of the partial replacement on the microstructure, tensile property, and cold formability are reported for the low-carbon third-generation AHSS sheets, which are classified into two groups...

The effects of thermomechanical processing on the microstructure and hydrogen embrittlement properties of ultrahigh-strength, low-alloy, transformation-induced plasticity (TRIP)-aided bainitic ferrite (TBF) steels were investigated to apply to automobile forging parts such as engine and drivetrain parts. The hydrogen embrittlement properties were e...

Cold stretch-formability and stretch-flangeability of 0.2%C-1.5%Si-5.0%Mn (in mass%) martensite-type medium Mn steel were investigated for automotive applications. High stretch-formability and stretch-flangeability were obtained in the steel subjected to an isothermal transformation process at temperatures between Ms and Mf − 100 °C. Both formabili...

To develop ultrahigh-strength steels for automotive impact safety parts, the effects of the microstructure and nitrogen content on the fatigue properties of ultrahigh-strength low alloy transformation-induced plasticity (TRIP)-aided steels with martensite (TM), bainitic ferrite-martensite (TBM), and bainitic ferrite (TBF) matrices were investigated...

To apply the duplex type low-carbon medium-manganese steel to the hot/warm-forging and -stamping products, the influence of cooling process routes immediately after intercritical annealing such as air-cooling (AC) and isothermal transformation (IT) processes on the impact toughness of 0.2%C-1.5%Si-5%Mn (in mass %) duplex type medium-Mn (D-MMn) stee...

This article introduces the microstructural and mechanical properties of low and medium-carbon advanced martensitic steels (AMSs) subjected to heat-treatment, hot- and warm- working, and/or case-hardening processes. The AMSs developed for sheet and wire rod products have a tensile strength higher than 1.5 GPa, good cold-formability, superior toughn...

To develop ultrahigh-strength steels for automotive impact safety parts, the effects of the microstructure and nitrogen content on the fatigue properties of ultrahigh-strength low alloy transformation-induced plasticity (TRIP)-aided steels with martensite (TM), bainitic ferrite-martensite (TBM), and bainitic ferrite (TBF) matrices were investigated...

Ultrahigh-strength ferrous steels, related to the strain-induced martensite transformation (or transformation-induced plasticity: TRIP) of metastable retained austenite, such as TRIP-aided bainite/martensite steels, quenching and partitioning steels, nanostructured bainitic steels (or carbide free bainitic steels) and medium manganese steels, are c...

To develop ultra high-strength cold stamping steels for automobile frame parts, the effects of alloying elements on hydrogen embrittlement properties of ultra high-strength low alloy transformation induced plasticity (TRIP)-aided steels with a martensite matrix (TM steels) were investigated using the four-point bending test and conventional strain...

This paper presents the microstructural and mechanical properties of low and medium carbon advanced high-strength forging steels developed based on the third generation advanced high-strength sheet steels, in conjunction with those of conventional high-strength forging steels. Hot-forging followed by an isothermal transformation process considerabl...

This paper presents the microstructural and mechanical properties of low and medium carbon advanced high-strength forging steels developed based on the third generation advanced high-strength sheet steels, in conjunction with those of conventional high-strength forging steels. Hot-forging followed by an isothermal transformation process considerabl...

In this study, the effects of Cr and Mo additions on mechanical properties of hot-forged medium carbon TRIP-aided bainitic ferrite (TBF) steel were investigated. If 0.5%Cr was added to the base steel with a chemical composition of 0.4%C, 1.5%Si, 1.5%Mn, 0.5%Al, and 0.05%Nb in mass%, the developed steel achieved the best combination of strength and...

In this study, high carbon bearing steel of GCr15 (100Cr6) is applied to explore the double quenching effects on both rotated bending fatigue strength (RBF-strength) and rolling contact fatigue life (RCF-life). The RBF-strength and RCF-life is about 1000 MPa and 1.1 × 10⁷ cycles under a maximum Hertzian stress of 4.5 GPa for the single quenched and...

Surface-hardened layer characteristics and fatigue strength properties of transformation-induced plasticity-aided martensitic steels subjected to heat-treatment or vacuum carburization followed by fine-particle peening are revealed for automotive applications specially for powertrain parts. The as-heat-treated steels without the case-hardening proc...

The effects of fine-particle peening conditions on the surface-hardened layer properties of newly developed case-hardening steel, i.e., transformation-induced plasticity-aided steel with a chemical composition of 0.2% C, 1.5% Si, 1.5% Mn, 1.0% Cr, 0.2% Mo, and 0.05% Nb (mass%) were investigated for the fabrication of automotive drivetrain component...

The effects of fine particle peening conditions on the rotational bending fatigue strength of a vacuum-carburized transformation-induced plasticity-aided martensitic steel with a chemical composition of 0.20 pct C, 1.49 pct Si, 1.50 pct Mn, 0.99 pct Cr, 0.02 pct Mo, and 0.05 pct Nb were investigated for the fabrication of automotive drivetrain part...

Fatigue properties of a transformation-induced plasticity-aided martensitic steel subjected to vacuum carburisation under carbon potentials ranging from 0.70 to 0.80 mass% and subsequent fine-particle peening were investigated for the fabrication of precision transmission gears. The fatigue limits of smooth specimens increased by 34–41% with increa...

The torsional fatigue strength of newly developed case hardening steel, i.e., transformation-induced plasticity-aided martensitic steel subjected to vacuum carburizing followed by fine particle peening, was investigated for the fabrication of downsized precision gears with high torque capacity and wear resistance. The surface-hardened layer propert...

The effects of carbon potential in vacuum-carburization on the surface-hardened layer properties of the 0.2%C-1.5%Si-1.5%Mn-1.0%Cr-0.05%Nb transformation-induced plasticity-aided martensitic steel were investigated for the fabrication of precision gears. The volume fraction of retained austenite and hardness in the surface hardened layer of the ste...

Transformation-induced plasticity (TRIP)-aided bainitic ferrite steels developed for automotive applications have attractive mechanical properties such as ductility, formability, toughness, fatigue strength and delayed fracture strength. These mechanical properties are principally associated with a ductile lath-structure matrix and the strain-induc...

The warm stretch formability and flangeability of 0.2 pct C-1.5 pct Si-5 pct Mn transformation-induced plasticity-aided sheet steel with annealed martensite matrix were investigated for automotive applications. Both formabilities were enhanced by warm forming at peak temperatures of 423 K to 573 K and 423 K to 523 K (150 °C to 300 °C and 150 °C to...

The effects of fine particle peening on the fatigue properties of a transformation-induced plasticity-aided martensitic steel with a chemical composition of 0.2% C, 1.5% Si, 1.5% Mn, 1.0% Cr, and 0.05% Nb (mass%) were investigated for applications in precision gears. When this steel was subjected to fine particle peening after heat treatment, highe...

Warm tensile properties of 0.2% C–1.5% Si–5.0% Mn transformation-induced plasticity (TRIP)-aided steel sheets with annealed martensite matrix and retained austenite of 39.4 vol.% were investigated for automotive applications. The product of tensile strength and total elongation (TS × TEl) of the TRIP-aided steel was enhanced to 50 GPa% by warm defo...

Effects of Mn content on warm stretch-flangeability are investigated using 0.2%C–1.5%Si–(1.5–5.0)% Mn transformation-induced plasticity (TRIP)-aided sheet steels with annealed martensite matrix. Warm hole-expansion at 150–250 °C after hole-punching at 25 °C enhances the stretch-flangeability of 3 and 5% Mn steels. The warm stretch-flangeability inc...

This paper introduces the microstructure, retained austenite characteristics, strain-induced transformation-deformation mechanism and mechanical properties of transformation-induced plasticity (TRIP)-aided martensitic (TM) steels for the automotive applications. Because the microstructure consists of a wide lath-martensite structured matrix and a m...

This paper introduces the microstructure, retained austenite characteristics, strain-induced transformation-deformation mechanism and mechanical properties of transformation-induced plasticity (TRIP)-aided martensitic (TM) steels for the automotive applications. Because the microstructure consists of a wide lath-martensite structured matrix and a m...

The effects of warm working on microstructural, retained austenite characteristics and shear deformation properties of 0.2C–1.5Si–1.5Mn–1.0Cr–0.2Mo TRIP-aided martensitic (TM) steel for applications to automotive frame and forging parts were investigated. When warm working at 550 °C and post cooling at 1 °C/s was conducted to the TM steel, volume f...

Low cycle fatigue hardening/softening behavior of a 0.2 pct C–1.5 pct Si–1.5 pct Mn–1.0 pct Cr–0.2 pct Mo–0.05 pct Nb transformation-induced plasticity (TRIP)-aided steel consisting of a wide lath martensite structure matrix and a narrow lath martensite–metastable retained austenite mixture was investigated. The steel exhibited notable fatigue hard...

Purpose: Warm stretch-formability of 0.2%C-1.5%Si-(1.5-5.0)%Mn transformation-induced plasticity (TRIP)-aided sheet steels with annealed martensite matrix was investigated for automotive applications. Additionally, the warm stretch-formability was related with the retained austenite characteristics. Design/methodology/approach: This study was aimed...

The impact properties of 0.2 pct C-1.5 pct Si-(1.5 to 5) pct Mn transformation-induced plasticity (TRIP)-aided steels with an annealed martensite matrix which had been subjected to isothermal transformation after inter-critical annealing were investigated for potential automotive applications. The impact properties are related to the retained auste...

To improve the toughness of ultra high-strength steels, the effects of alloying elements on impact properties of ultra high-strength low alloy TRIP-aided steels with bainitic ferrite matrix (TBF steels) were investigated. In this study, C-Si-Mn and C-Si-Mn-Al-Nb-Mo TBF steels were used. Upper shelf Charpy impact absorbed value of TBF steels were ch...

The effects of matrix types on Charpy impact properties were investigated in Fe-0.2% C-1.5% Si-1.5% Mn (mass%) transformation-induced plasticity steels. The steels with annealed martensite and bainitic ferrite matrix possessed higher upper shelf Charpy impact absorbed energy than the steel with polygonal ferrite and martensitic matrix. In addition,...

The substitution of Si with Al in 0.2%C-1.5%Si-1.25%Mn-0.2%Cr ultrahigh strength transformation-induced plasticity (TRIP)-aided martensitic (TM) sheet steel improves galvanization. The effect of Al content on the microstructure and formabilities of the TM steel was therefore investigated. Replacement of Si with Al maintained the high volume fractio...

The effects of fine particle peening (FPP) on the torsional fatigue properties were investigated in the case of a transformation-induced plasticity (TRIP)-aided bainitic ferrite (TBF) steel that has potential for use in precision gears. FPP resulted in a significant increase in the torsional fatigue limit of the TBF steel, compared with that of a q...

Stretch-formability and -flangebility of 0.2%C-1.5%Si-(1.5-5.0)%Mn transformation-induced plasticity (TRIP)-aided annealed martensitic sheet steels were investigated for automotive applications. When subjected to isothermal transformation process at temperatures below martensite-start temperature after intercritical annealing, 5%Mn steel possessed...

The effects of the working temperature, working reduction ratio, and post cooling rate on the microstructural change, retained austenite characteristics, and shear properties of 22SiMnCrMoB transformation-induced plasticity (TRIP)-aided martensitic (TM) steel were investigated. The slow cooling rate at 1 °C/s after warm working at 650 °C with a red...

The effects of fine particle peening on the torsional strength of a transformation-inducedplasticity (TRIP)-aided martensitic (TM) steel were investigated for applications to precision gears. Fine particle peening increased the fatigue limits and lowered the notch-sensitivities of steel, compared with quenched and subsequently tempered SNCM420 stee...

The effects of fine particle peening on the fatigue properties of transformation-induced plasticity (TRIP)-aided bainitic ferrite steel were investigated for applications to precision gears. Fine particle peening increased the fatigue limit and lowered the notch-sensitivity in the TRIP-aided bainitic ferrite (TBF) steel, compared with SNCM420 steel...

A high-strength cold-rolled steel sheet excellent in uniform elongation, including in percent by mass: 0.10-0.28% of C: 1.0-2.0% of Si; and 1.0-3.0% of Mn, and the structures of the same having the space factors below to the entire structure: 30-65% of bainitic ferrite: 30-50% of polygonal ferrite; and 5-20% of residual austenite.

This paper deals with the microstructural and mechanical properties of a transformation-induced plasticity-aided martensitic (TM) steel that is expected to serve as an advanced structural steel for automotive applications. The microstructure consisted of a wide lath-martensite-structured matrix and a mixture of narrow lath-martensite and metastable...

The impact toughness of 0.2% C–1.5% Si–(1.5–5.0)% Mn (mass%) transformation-induced plasticity (TRIP)-aided steels with bainitic ferrite and/or martensite structure matrices produced by isothermal transformation process is investigated for automotive body applications. The highest impact toughness, highest Charpy impact absorbed value (CIAV) at 298...

This study investigates whether the transformation-induced plasticity (TRIP) of metastable retained austenite, and a finely dispersed MA-like phase (narrow-lath martensite-retained austenite complex phase), produced by the addition 1.5%Si or 1.5% Si-1.0%Cr (mass%) can improve the cold formability of 22MnB martensitic sheet steel. The best combinati...

Effect of manganese content on burring and tapping in 0.2C-1.5Si-(1.0-2.0)Mn (mass%) high strength TRIP-aided sheet steels with polygonal ferrite matrix (TDP steels) was investigated for automotive applications. Burring test was performed on a machining center with rotational speed of 3500 rpm and cutting feed rate of 10 mm/min, using disc specimen...

The stretch-flangeability of 0.2%C−1.5%Si−(1.5−5.0)%Mn transformation-induced plasticity (TRIP)-aided martensitic sheet steels was investigated to develop third-generation advanced high-strength steel for automotive body applications. When these steels were subjected to isothermal transformation process at temperatures below the martensite finish t...

To apply a transformation-induced plasticity (TRIP)-aided steel consisting of bainitic ferrite structure matrix and metastable retained austenite of 10 vol% (TBF steel) to some precision gears, the effects of fine particle peening on the Vickers hardness and residual stress in a surface layer of the TBF steel were investigated. The peened surface l...

The effects of Cr, Mo, and Ni addition on the microstructure and stretch-flangeability of a 0.2%C– 1.5%Si–1.5%Mn–0.05%Nb (mass%) transformation-induced plasticity (TRIP)-aided martensitic steel sheet produced by an isothermal transformation process at a temperature below martensite transformation-finish temperatures were investigated in order to de...

Transformation-induced plasticity (TRIP)-aided martensitic (TM) steel consisting of wide lath-martensite structure matrix and a mixture of narrow lath-martensite and metastable retained austenite (MA-like phase) can be expected as the next generation ultrahigh-strength structural steel because of a good combination of tensile strength and total elo...

The fracture toughness of an advanced ultrahigh-strength 0.2%C-1.5%Si-1.5%Mn-1.0%Cr-0.05%Nb (in mass%) transformation-induced plasticity (TRIP)-aided steel with a bainitic ferrite and/or martensite structure matrix was investigated for applications in automobiles, construction machines, and pressure vessels. After the steel was austenitized and iso...

With the aim of increasing the volume fraction and stability of the retained austenite characteristics in a transformation-induced plasticity (TRIP)-aided steel with wider lath-martensite structure matrix, the effects of varying the post-hot-working cooling rate of a 0.2%C-1.5%Si-1.5%Mn-1.0%Cr-0.05%Nb (mass%) steel on the retained austenite charact...

The effects of variations in the rate of post-austenitization cooling of a 0.2%C-1.5%Si-1.5%Mn-1.0%Cr-0.2%Mo-1.5%Ni-0.05%Nb (mass%) transformation-induced plasticity (TRIP)-aided steel with a lath martensite structure matrix on the Charpy impact toughness were investigated, with the aim of improving the material properties for automotive body appli...

The stretch-flangeability of 0.2%C-1.5%Si-(1.5-5.0)%Mn transformation-induced plasticity (TRIP)-aided martensitic sheet steels was investigated to develop third-generation advanced high-strength steel for automotive body applications. When these steels were subjected to isothermal transformation process at temperatures below the martensite finish t...

A high-strength steel machined product giving excellent hardenability has a metal microstructure with excellent balance of strength and toughness and high stability of retained austenite. The product is composed of an ultra-high low-alloy TRIP steel having a metal microstructure which contains an appropriate quantity of two or more of Cr, Mo, and N...

The effects of the addition of Cr, Mo, and/or Ni on the Charpy impact toughness of a 0.2 pct C-1.5 pct Si-1.5 pct Mn-0.05 pct Nb transformation-induced plasticity (TRIP)-aided steel with a lath-martensite structure matrix (i.e., a TRIP-aided martensitic steel or TM steel) were investigated with the aim of using the steel in automotive applications....

The effects of Cr, Mo, and Ni addition on the microstructure and stretch-flangeability of a 0.2%C-1.5%Si-1.5%Mn-0.05%Nb (mass%) transformation-induced plasticity (TRIP)-aided martensitic steel sheet produced by an isothermal transformation process at a temperature below martensite transformation-finish temperatures were investigated in order to dev...

The notch-fatigue limit and notch sensitivity of 0.1–0.6%C-1.5%Si-1.5%Mn transformation-induced plasticity (TRIP)-aided martensitic steels (TM steels) were investigated for use as common rails in next-generation automotive diesel engines. Also, these properties were related to the microstructural and retained austenite characteristics. When TM stee...

The effects of microalloying on the fracture toughness of 0.2%C1.5%Si1.5%Mn 0.05%Nb (mass%) transformation-induced plasticity-aided steel with a lath-martensite structure matrix were investigated. When 0.002% B or 1.0% Cr was added to the base steel, the steel achieved a fracture toughness that was as high as that of 18%Ni maraging steel. Based on...

The effects of shot-peening on surface residual stress in two kinds of 0.2%C-1.5%Si-1.5%Mn-1.0%Cr-0.2%Mo-0.05%Nb transformation-induced plasticity (TRIP)-aided steels with bainitic ferrite or martensite matrix structure were investigated to enhance the notch-fatigue strength of a precision gear. Shot-peening enhanced the compressive residual stress...

The effects of shot-peening on surface residual stress in two kinds of 0.2%C-1.5%Si-1.5%Mn-1.0%Cr-0.2%Mo-0.05%Nb transformation-induced plasticity (TRIP)-aided steels with bainitic ferrite or martensite matrix structure were investigated to enhance the notch-fatigue strength of a precision gear. Shot-peening enhanced the compressive residual stress...

The optimum isothermal transformation temperature for the formability of an advanced ultra-high-strength cold-rolled transformation-induced plasticity (TRIP)-aided martensitic steel, with a composition of 0.2%C-1.5%Si-1.5%Mn-1.0%Cr-0.05%Nb, was investigated for some automotive applications. After austenitization and isothermal transformation at 200...

To develop ultra high-strength steels for automotive impact safety parts and forging parts, the fatigue properties of ultra high-strength low alloy TRIP-aided steels with martensite (TM), bainitic ferrite (TBF) and martensite-bainite (TBM) matrix were investigated. TM steels achieved both high tensile strength of 1370 MPa grade and excellent fatigu...

The effects of shot-peening on surface residual stress in two kinds of 0.2%C-1.5%Si-1.5%Mn-1.0%Cr-0.2%Mo-0.05%Nb transformation-induced plasticity (TRIP)-aided steels with bainitic ferrite or martensite matrix structure were investigated to enhance the notch-fatigue strength of a precision gear. Shot-peening enhanced the compressive residual stress...

To develop a transformation-induced plasticity (TRIP)-aided bainitic ferrite steel (TBF steel) with high hardenability for a common rail of the next generation diesel engine, 0.2 pct C-1.5 pct Si-1.5 pct Mn-0.05 pct Nb TBF steels with different contents of Cr, Mo, and Ni were produced. The notch-fatigue strength of the TBF steels was investigated a...

抄録 The effects of Cr and Mo on microstructure, retained austenite characteristics and tensile properties of a 0.2%C, 1.5%Si, 1.5%Mn, 0.05%Nb TRIP-aided steel with annealed martensite matrix, “TRIP-aided annealed martensitic steel; TAM steel”, were investigated to enhance the hardenability. Volume fraction and carbon concentration of retained austen...

Cr, Mo and/or Ni were added to TRIP-aided bainitic ferrite (TBF) steel (0.2% C, 1.5% Si, 1.5% Mn and 0.05% Nb ultrahigh-strength TBF steel) in order to increase its hardenability. In addition, the effects of the alloying elements on the Vickers hardness, microstructure and retained austenite characteristics of the TBF steels were investigated. When...

Fracture toughness of an ultrahigh-strength TRIP-aided steel with lath-martensite structure matrix or “a TRIP-aided martensitic steel” was investigated for some applications to automobiles, construction machines, ships and so on. When the steel with a chemistry of 0.2%C, 1.5%Si, 1.5%Mn, 1.0%Cr and 0.05%Nb (in mass%) was subjected to partitioning at...

To develop ultra high strength steels for automotive impact safety parts, effects of alloying elements on hydrogen embrittlement resistance of ultrahigh strength low alloy TRIP-aided steels with martensitic matrix (TM steel) were investigated. Hydrogen embrittlement susceptibilities of TRIP-aided steels were decreased by addition of alloying eleme...

The effects of partitioning after an isothermal transformation (IT) process on the formability of a transformation-induced-plasticity (TRIP)-aided steel with 0.2% C, 1.5% Si, 1.5% Mn, and 0.05% Nb (mass%) and with two kinds of lath martensite structure matrices (also called TRIP-aided martensitic or TM steel) were investigated. When partitioning wa...

A new type of 0.2%C-1.5%Si-1.5%Mn ultra high-strength low alloy TRIP-aided steel consisting of lath martensite structure matrix and metastable retained austenite films, "TRIP-aided martensitic steel; TM steel", was developed by means of quenching and partitioning process. In addition, effects of partitioning temperature and time on the microstructu...

Fracture toughness of an ultrahigh-strength TRIP-aided steel with lath-martensite structure matrix or "a TRIP-aided martensitic steel" was investigated for some applications to automobiles, construction machines, ships and so on. When the steel with a chemistry of 0.2%C, 1.5%Si, 1.5%Mn, 1.0%Cr and 0.05%Nb (in mass%) was subjected to partitioning at...

Recently developed ultra high-strength low alloy transformation-induced plasticity (TRIP)-aided steel with martensitic lath structure matrix or "TRIP-aided Martensitic steel; TM steel" possesses a high impact toughness. In this study, to apply the TM steel to some hot-forging parts, the effects of hot-forging on microstructure, retained austenite c...

Glass-like carbon (GC) is expected as a die material for press molding of glass micro optical devices. However, the mechanical and thermal properties are not enough to use as precision mold die. So, GC composites reinforced by vapor grown carbon fiber (GC/VGCF composites) were developed to improve the properties. The GC/VGCF composites achieved hig...

A new type of advanced high-strength TRIP-aided bainitic ferrite steel with a good hardenability was developed for ultra high pressure DI-diesel engine common rail application. Addition of 1.0%Cr or 1.0%Cr-0.2%Mo to 0.2%C-1.5%Si-1.5%Mn- 0.05%Nb base steel achieved high notch fatigue limit and low notch sensitivity which realize to serve under maxim...

Effect of thermal drilling condition on burring of 0.2C-(1.0-2.5)Si-(1.0-2.0)Mn (mass%) ultrahigh strength TRIP-aided sheet steels with polygonal ferrite matrix (TDP steels) was investigated for automotive applications. The combined rotational and downward force of the thermal drilling tool bit created friction heat. The height of the bushing was r...

The reactivity between nanoimprint mold materials and optical glass has been investigated by measuring the contact angle between these materials in a nitrogen atmosphere at high temperatures up to 1000 °C. Since low-softening-temperature optical glass was chosen in this study, the thermal upper limit of the contact angle measurement was set as 800...

TRIP-aided cold rolled sheet steel with martenslte lath structure matrix (TRIP-aided martensitic steel; TM steel) possesses a good combination of tensile strength and total elongation due to the transformation-Induced plasticity (TRIP) of metastable retained austenlte. In this study, stretch-flangeability of the TM steels subjected to different pro...

Retained austenite characteristics and carbide formation behavior in newly developed 0.2C-1.5Si-1.5Mn-Cr-Mo-Ni-Nb-B (wt. pct.) transformation induced plasticity (TRIP)-aided steel bars with a martensitic matrix microstructure (TM steel) were investigated. If the 0.2C-1.5Si-1.5Mn (wt. pct.) base steel was processed by austenitizing at 900oC and then...

Fatigue properties of TRIP-aided annealed martensitic steels with chemical composition of 0.2%C, 1.5%Si, 1.5%Mn, 0-1.0%Cr, 0-0.2%Mo, 0-0.05%Nb, 0-18ppmB was examined for application of automotive diesel engine common rail. The steels achieved extremely higher notch fatigue limits and lower notch-sensitivity than the conventional structural steels,...

Effects of alloying elements on impact toughness of advanced ultra high-strength 0.2%C-1.5%Si-1.5%Mn TRIP-aided steels with bainitic ferrite/martensite matrix structure, “TRIP-aided bainitic ferrite steel; TBF steel,” were investigated for some applications of automotive structural parts. Additions of Cr, Mo and B, especially B addition, for enhanc...

An ultra high-strength TRIP-aided steel consisting of bainitic ferrite lath structure matrix and interlath retained austenite films possesses high toughness and fatigue strength, as well as high resistance against hydrogen embrittlement. In this study, to develop the ultra high-strength TRIP-aided steel for hot-forging parts, the effects of hot-for...

Glass-like carbon is expected as a die material for mold-press of optical glass devices. In this study, optimum machining conditions on electrical discharge machinability of glass-like carbon die were examined in working fluid such as oil or ion-exchanged water. Short machining time was achieved by electrical discharging in ion-exchanged water, as...

Fatigue strength of newly developed TRIP-aided annealed martensitic steels (TAM steels) with chemical composition of 0.4%C, 1.5%Si, 1.5%Mn, 0-1.0%Cr, 0-0.2%Mo, 0.05%Nb, 0-18ppmB was examined for application of automotive diesel engine common rail. The TAM steels achieved higher fatigue limits than the conventional structural steels. Also, the TAM s...

Glass-like carbon (GC) is expected as a die material for mold-press of optical glass devices. However, the mechanical and thermal properties are not enough to use as mold die. Recently, glass-like carbon/carbon nanotube composite (GC-V) reinforced by vapor grown carbon fiber (VGCF) was developed to improve the properties. In this study, optimum mac...

Microstructure, tensile properties and stretch-flangeability of 980-1 470 MPa grade Al or Al-Nb bearing TRIP-aided cold-rolled sheet steels with bainitic ferrite and/or martensite matrix microstructure (TBF steels) were investigated for automotive applications such as impact member reinforcements, sheet flames and so on. In addition, these properti...

Synopsis : The microstructure, retained austenite characteristics, tensile properties and stretch-flangeability of ultra high-strength 0.2%C-1.5%Si1.5%Mn (mass%) TRIP-aided bainitic ferrite cold-rolled sheet steel, "TBF steel", were investigated for automotive applications. When isothermally held at temperatures less than martensite-start temperatu...

Ultra high-strength TRIP-aided steel consisting of bainitic ferrite matrix and interlath retained austenite films (TBF steel) possesses high toughness and fatigue strength, as well as high resistance against hydrogen embrittlement. In this study, to improve further these mechanical properties, the effects of hot forging and subsequent isothermal tr...

The effects of cold-rolling strain on microstructure and formability of 0.2%C-0.5-1.5%Si-1.5%Mn-0.04-1.0%Al, in mass%, TRIP-aided cold-rolled sheet steels with annealed bainitic lath structure matrix (TAB steels) were investigated. Cold rolling straining changed the matrix structure after intercritical annealing from annealed bainitic lath structur...

The performance of hydrogen embrittlement, fatigue properties and impact toughness of ultra high strength transformation induced plasticity aided steels with bainitic ferrite matrix (TBF steels) has been discussed. Some characteristics and deformation transformation mechanism of the retained austenite has also been discussed. It has been observed t...

Glassy carbon (GC) is expected as a die material for mold-pressing of glass micro optical devices. However, the mechanical and thennal properties are not enough to use as precision mold die. So, GC composites reinforced by vapor grovai carbon fiber (GC/VGCF composites) were developed to improve the properties. The GC/VGCF composites achieved high t...