National Institute for Materials Science

Neturen Co., Ltd.

Other

National Research Institute for Metals

Nissan Motor Company Limited

Mitsubishi Heavy Industries Limited

Japan As Represented by Director General of National Research Institute for Metals

Japan As Represented by Director General of National Research Institute

Kotobu Nagai

Shiro Torizuka

Kaneaki Tsuzaki

Kazuhiro Kawasaki

Takahiko Kanai

Munehisa Hatta

Masao Hayakawa

Fumiaki Ikuta

Osamu Umezawa

Takehiko Itagaki

Hiroshi Nakajima

Eizaburou Nakanishi

Tsuyoshi Yoshida

Masayuki Miyake

Eizaburo Nakanishi

Tadanobu Inoue

Toshihiro Hanamura

Toru Hayashi

Eijiro Muramatsu

Eijrio Muramatsu

Yuuji Kimura

Takehito Itagaki

Tohru Hayashi

Yuji Muramatsu

Shuji Wanikawa

Minoru Ootaguchi

A welding equipment for metallic materials capable of performing heat treatment such as tempering based on partial heating in spot welding is provided. The welding equipment sandwiches metallic materials with a pair of electrodes, and heats different regions of the metallic materials by energization, with the pair of electrodes maintained at the same position with respect to the metallic materials. The welding equipment includes a first heating means connected to the pair of electrodes for heating and welding the internal region of the circle defined by projecting the cross-sectional area of the axis of the electrodes on the metallic materials by applying power having a low first frequency, a second heating means for heating a ring-shaped region along the circle by applying power having a second frequency that is higher than the first frequency, and an energization control unit for independently controlling the first and the second heating means.

Welding equipment for metallic materials and method for welding metallic materials

A welding structural partis manufactured by overlapping the surfaces of steel sheets, and forming a weld zone by spot welding. The weld zoneincludes: a weld nugget; and a heat affected zonesurrounding the weld nugget, wherein the hardness in the weld zone increases along an exterior regionof the heat affected zonetoward the heat affected zone, and then decreases along the heat affected zonetoward the central region of the weld nugget. In the boundary region between the weld nuggetand the heat affected zone, the weld nuggetmay have a convex portionA bulging into the heat affected zonealong the overlapped portion. The steel sheetscontain carbon in 0.15 mass % or more.

Welding structural part and welding method of the same

A welding equipment for metallic materials capable of performing heat treatment such as tempering based on partial heating in spot welding is provided. The welding equipmentsandwiches metallic materialswith a pair of electrodes, and heats different regions of the metallic materialsby energization, with the pair of electrodesmaintained at the same position with respect to the metallic materials. The welding equipment includes a first heating meansconnected to the pair of electrodesfor heating and welding the internal region of the circle defined by projecting the cross-sectional area of the axis of the electrodes on the metallic materials by applying power having a low first frequency, a second heating meansfor heating a ring-shaped region along the circle by applying power having a second frequency that is higher than the first frequency, and an energization control unitfor independently controlling the first and the second heating means

A high-strength die-quenched partis formed by heating a high-strength steel sheetup to an austenite region, hot stamping and cooling inside a mold, and its microstructure has the martensite wherein carbide particlesare finely dispersed over an entire region including prior-austenite grain boundaries. It is desirable that the prior-austenite grain size in the microstructure of the high-strength steel sheet, which is a base material, be 10 &#x3bc;m or smaller. The high-strength die-quenched part has high-strength and high-ductility thanks to its martensite.

High-strength and high-ductility die-quenched parts and method of manufacturing the same

A wire rod or a steel wire of a bamboo nano-structure, whose mean grain diameter in a C-direction section is 200 nm or smaller, is prepared by applying a hot or warm working and additionally applying a cold working to a steel and next, by performing a forging, by a tool or a die such as cold pressure production, to a section, of a desired, limited site, other than a section parallel to an L-direction, an equiaxed nano-structure, whose mean grain diameter is 200 nm or smaller, is formed in this site. As a typical example of a formed article, there is enumerated a high strength micro screw in which a shaft outer diameter is 1.6 mm or smaller, a surface layer part of a head part recess has equiaxed nano-structure and a hardness H&#x2267;300, and a screw main body portion has bamboo nano-structure and a hardness H&#x2267;250.

High strength formed article comprising hyperfine grain structure steel and manufacturing method of the same

The invention presents a new warm control rolling method, in consideration of processing heat generation, as a method of stably manufacturing ultrafine crystal steel of 3 microns to 1 micron or less, without any limitation in pass interval or strain speed, being a rolling method of manufacturing steel mainly composed of fine ferrite particle texture with average ferrite grain size of 3 &#x3bc;m or less, in which, in the rolling process of one pass or more wherein the rolling temperature range is a temperature region of 350&#xb0; C. to 800&#xb0; C., the material temperature upon start of rolling of each rolling process does not exceed the maximum temperature of 800&#xb0; C., and the material temperature during rolling and right after final rolling (within 1 second) is not lower than 350&#xb0; C., temperature Tright after rolling in each rolling process (within 1 second) is not higher than the temperature that is higher than rolling entry temperature Tby 100&#xb0; C. and the material temperature right after rolling (within 1 second) is not lower than the temperature that is lower than the temperature right before rolling by 100&#xb0; C.

Controlled warm-rolling method

A method of rolling a material in two more continuous passes is disclosed. The method includes rolling the material with a flattened-shaped caliber in a first pass, and subsequently rolling with a square-shaped caliber in a second pass. The rolling is performed with a first pass caliber having a flattened shape, wherein the ratio of the length (2A) of minor axis of the first pass caliber to an initial width (2A) is (A/A)&#x2266;0.75; and a second pass caliber, wherein the ratio of a diagonal dimension (2A) of the second pass caliber to the length (2B) of the major axis of the material after the first pass is (A/B)&#x2266;0.75 to introduce the large strain into the material.

Large strain-introducing working method and caliber rolling device

A fine ferrite-based steel is disclosed, wherein at least 60% of the ferrite grain boundary is a large angle grain boundary of at least 15&deg;, and the mean ferrite grain size is not more than 2.5 &mgr;m. The fine ferrite-based steel of the invention has a high strength and a long fatigue life.

Fine ferrite-based structure steel production method

A method of producing a ultra fine grain steel made of ferrite having a mean grain size of not larger that 3 &mgr;m as the base phase, after ingoting raw materials, by austenitizing the ingot by heating it to a temperature of at least an Ac 3 point, then, applying compression working of a reduction ratio of at least 50% at a temperature of from an Ae 3 point or lower to an Ar 3 point &minus;150&deg; C., or at a temperature of at least 550&deg; C., and thereafter, cooling, wherein the strain rate as compression working is in the range of from 0.001 to 10/second.

Production method of ultra fine grain steel

The invention according to the present application provides a high strength solidification body by solidifying a starting metallic powder of iron and the like by means of plastic working using hydrostatic pressing, which is, for instance, a high strength high toughness steel material and the like having a superfine texture comprising a crystalline texture consisting of grains 5 &mgr;m or less in average diameter, or preferably, 3 &mgr;m or less in average diameter. Furthermore, the present invention provides a steel material included in the high strength solidification body, which contains oxide grain 0.2 &mgr;m or less in diameter at a volume ratio of from 0.5 to 60%.

High-strength metal solidified material and acid steel and manufacturing methods thereof

A high strength phosphorus-containing steel having fine texture free from the problem of embrittlement by positively using the presence of P, which is a carbon steel having an average ferritic grain diameter of 3 &mgr;m or less and containing from 0.04 to 0.1% by mass of P, wherein the volume fraction of P segregated in the grain boundary accounts for 0.3 or less in case the grain boundary is covered by a P layer 1 nm in thickness.

High strength phosphorus-containing steel and method for producing the same

The invention provides an ultra-fine grain steel comprising fine ferrite grains as oriented at random and surrounded by large angle grain boundaries. The steel comprises fine ferrite grains having a mean grain size of not larger and 3.0 &mgr;m and surrounded by large angle grain boundaries having an misorientation not smaller than 15&deg;.

Ultra-fine grain steel and method for producing it

In carbon steel, oxides with grain diameter of 1 .mu.m or less and with grain spacing of 6 .mu.m or less are dispersed to suppress growth of .gamma. grains by heating at .gamma. region temperature.

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Ibaraki, Japan

Kotobu Nagai