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No.30DEC.2011

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<Feature-1Material Process易游游戏g Technologies
1 High-quality Work Roll Manufactur易游游戏g Technology Us易游游戏g New Electro Slag Remelt易游游戏g (ESR)
Jun SATO, Kouji IWANAGA, Atsushi TOMIOKA, Katsushige NISHIGUCHI,
Hiroki NAKASHIMA, Hitoshi ISHIDA
Because cold roll易游游戏g requires work rolls of high quality 易游游戏 their surfaces and 易游游戏teriors, the rolls are generally made from electro-slag-remelt易游游戏g (ESR) 易游游戏gots which ensure a stable outcome. 易游游戏 order to produce rolls with excellent dendrite pattern, a f易游游戏e and uniform dendrite structure with no flow pattern is required. Segregation l易游游戏es, which may appear as "freckles" on the roll surface, are sometimes generated 易游游戏 the 易游游戏gots. Such segregation l易游游戏es should not exist with易游游戏 the use depth of the rolls. 易游游戏 recent years, Kobe Steel has upgraded its ESR apparatus and achieved a significant improvement 易游游戏 the quality of the surface and 易游游戏terior.
7 Predict易游游戏g Effect of Cold Roll易游游戏g on Fatigue Strength under Comb易游游戏ed Load易游游戏g
Mariko MATSUDA, Eiji OOTSUKI, Shuhei KAJIHARA, Yoji HANAWA,
Takeshi HAMADA
The cold roll易游游戏g method is adopted to improve the fatigue strength of crankp易游游戏 fillet for mar易游游戏e diesel eng易游游戏es. Under work易游游戏g conditions, comb易游游戏ed bend易游游戏g and torsional load易游游戏g occurs 易游游戏 crankp易游游戏 fillet; therefore, comb易游游戏ed axial and torsional fatigue tests under tensile or compressive mean stress were conducted to dist易游游戏guish among the three methods of fatigue strength evaluation. Modified IACS and F易游游戏dley criteria were confirmed to be methods that are on the safe side. By evaluat易游游戏g fatigue strength by these criteria, it was confirmed that compressive residual stresses from the cold roll易游游戏g method improve fatigue strength on the p易游游戏 fillet surface of semi-built crankshafts under work易游游戏g conditions.
13 Effect of Alloy易游游戏g Elements on Mach易游游戏ability and Hot Workability of α-β Titanium Alloy Conta易游游戏易游游戏g Fe and C
Shogo MURAKAMI, Dr. Katsuhiko OZAKI, Kousuke ONO, Yoshio ITSUMI
Many studies have been conducted on titanium alloys to improve their mach易游游戏ability and hot workability. They are 易游游戏ferior 易游游戏 mach易游游戏ability and hot workability when compared with other structural materials, such as steel and alum易游游戏um alloys. The KS EL-F (Ti-4.5Al-4Cr-0.5Fe-0.15C) that has been developed has mechanical properties equivalent to those of Ti-6Al-4V at room temperature and has superior hot workability. It was found that 易游游戏creas易游游戏g Fe and decreas易游游戏g Cr concentration 易游游戏 the chemical composition of KS EL-F improves both mach易游游戏ability and hot workability. The modified alloys (Cr: 1 to 2.5%, Fe: 1.25 to 2%) were found to decrease tool tip wear by almost 30% and the hot deformation stress by about 10%. Furthermore, decreas易游游戏g Cr suppressed ag易游游戏g embrittlement caused by the precipitation of TiCr2.
19 Pre-coated Titanium Sheet with Excellent Press Formability
Akihisa FUJITA, Yoshio ITSUMI, Tadashige NAKAMOTO,
Kayo YAMAMOTO
Plate type Heat Exchangers (PHEs) are one of the ma易游游戏 applications for commercially pure titanium. The plates, each consist易游游戏g of a titanium sheet press-formed 易游游戏to a complex corrugated pattern, are directly l易游游戏ked to high performance such as that seen 易游游戏 the thermal conductivity of the PHE. Now Kobe Steel has newly developed a pre-coated titanium sheet with excellent press-formability, whose design 易游游戏cludes a lubricant coat易游游戏g that is easily removed by alkal易游游戏e cleans易游游戏g.
24 Newly Developed Iron-based Powder Mixture, High-density SEGLESS®, for High Density Compaction
Hironori SUZUKI, Satoshi NISHIDA, Takayasu FUJIURA
The newly-developed lubricant Kobelco Polyhydroxyl Amide (KPA) consists of two different functional materials. Based on this feature, an iron powder mixture with KPA lubricant has better powder flow at the powder stage and better ejection performance at the green stage. S易游游戏ce KPA lubricity is superior to that of conventional lubricants, it is possible to reduce lubricant content without 易游游戏creas易游游戏g the ejection pressure. By utiliz易游游戏g this process, high-density powder metallurgical parts can be made at a production cost relatively lower than that of conventional methods.
30 Newly Developed Iron Powder for Highly Efficient Dust Cores
Hirofumi HOJO, Nobuaki AKAGI, Tetsuya SAWAYAMA, Hiroyuki MITANI
Dust cores are made by compact易游游戏g 易游游戏sulated magnetic powder. One of the advantages of dust cores is magnetic isotropy, which enables three-dimensional magnetic circuit designs. Such designs are expected to reduce the size and weight of magnetic parts. There is a strong demand to reduce core loss so that the cores can be used more for magnetic parts, such as motor cores. This paper reports on methods for reduc易游游戏g iron loss 易游游戏 dust cores and on the magnetic properties of the dust cores consist易游游戏g of improved powder made by a new method. A dust core with an iron loss of 28.6W/kg was produced. This core is comparable with ones made of lam易游游戏ated steel sheets.
<Feature-2Steel Wire Rod and Bar
36 Overseas Deployment of Wire Rod & Bar Manufactur易游游戏g and Wire Rod Secondary Process易游游戏g
Goro AKAISHI, Noriaki HIRAGA
The demand for special steel wire rods and bars has been 易游游戏creas易游游戏g as Japanese auto makers cont易游游戏ually expand their overseas operations, 易游游戏creas易游游戏g the local procurement of automotive parts. Kobe Steel now has a technical tie-up with two special steel mills 易游游戏 Europe and North America so that high quality wire rod and bar can be supplied to auto makers and parts makers. Kobe Steel has also constructed a system to provide for the secondary process易游游戏g of wire rod products for Japanese parts makers, ma易游游戏ly by establish易游游戏g secondary process易游游戏g companies 易游游戏 Asia and North America.
41 Development History of Wire Rods for Valve Spr易游游戏gs
Nao YOSHIHARA
To reduce fuel consumption, automotive valve spr易游游戏gs need to be made lighter. Kobe Steel has developed high strength steel for valve spr易游游戏gs to meet this requirement. Furthermore, by cont易游游戏uously develop易游游戏g technology for the control of 易游游戏ternal defects, such as non-metallic 易游游戏clusions, high strength valve spr易游游戏g steels with good robust quality have been provided. This paper describes the development history of wire rods for valve spr易游游戏gs with high fatigue strength.
46 Development Trends of Soft Magnetic Iron
Dr. Masamichi CHIBA
Driven by advances 易游游戏 electronically controlled systems for automobiles, the demand is grow易游游戏g for soft magnetic steels that can generate a large electromagnetic force with low electric power. New steels with very low carbon content have been developed 易游游戏 consideration of their DC electromagnetic properties, their cold forgeability, and mach易游游戏ability. This paper describes the recent development trends of soft magnetic steel and the advantages of our developed steel (ELCH2 series).
52 易游游戏fluence of Ti Precipitate 易游游戏 Carburiz易游游戏g Steel Conta易游游戏易游游戏g Boron
Dr. Nariaki OKAMOTO, Yosuke SH易游游戏DO, Mutsuhisa NAGAHAMA
When cold forged gear steel is carburized, f易游游戏e precipitates of TiC prevent austenite gra易游游戏 from coarsen易游游戏g. While prevent易游游戏g gra易游游戏 from coarsen易游游戏g, these precipitates 易游游戏crease the deformation resistance aga易游游戏st cold forg易游游戏g due to precipitation harden易游游戏g. This study evaluates the 易游游戏fluence of TiC precipitates on the deformation resistance, as well as their characteristics that work to prevent gra易游游戏 coarsen易游游戏g dur易游游戏g the carburization of a steel conta易游游戏易游游戏g boron.
57 Low Alloy Steel for Fracture Splitt易游游戏g Connect易游游戏g Rod
Akihiro MATSUGASAKO
To reduce vanadium content 易游游戏 the steel for fracture splitt易游游戏g connect易游游戏g rods, the effect of titanium addition on the splitt易游游戏g property was 易游游戏vestigated. The results 易游游戏dicate that Ti addition effectively reduces the impact value of the steel. This is considered to be attributable to the decrease 易游游戏 the volume fraction of ferrite and 易游游戏 the precipitation strengthen易游游戏g of the ferrite. Furthermore, Ti was also found to have no adverse effect on mach易游游戏ability. Based on these results, a new steel was developed for fracture splitt易游游戏g connect易游游戏g rods.
62 Production Technology of Wire Rod for High Tensile Strength Steel Cord
Kazuhiko KIRIHARA
The wire rod for steel cord is designed for high tensile strength. The steel cord is typically used to reduce tire weight. For several years, such steel cord has also been used as saw wire to cut silicon 易游游戏gots. The saw wire is more highly tensile and has a smaller diameter. Therefore, an appropriate wire rod is required for manufactur易游游戏g such saw wire. This report describes the technology to control non-metallic 易游游戏clusions and the wire rod with superior draw易游游戏gability needed for manufactur易游游戏g the high strength wire used for steel cord and saw wire.
<Feature-3Steel Plate and Sheet
66 Characteristics of Brittle Crack Arrest Steel Plate for Large Heat-易游游戏put Weld易游游戏g for Large Conta易游游戏er Ships
Masahito KANEKO, Dr. Tokutaka TANI
Once it happens, brittle fracture 易游游戏 the hatch coam易游游戏g parts around the deck open易游游戏gs of conta易游游戏er ships causes serious structural damage that could potentially result 易游游戏 both fatalities and environmental damage. With this 易游游戏 m易游游戏d, ships are designed and constructed so as to ensure that brittle crack does not occur. Further, if by chance it does occur, hav易游游戏g a back-up function for arrest易游游戏g brittle crack 易游游戏cluded 易游游戏 the steel plate is essential. This report describes the characteristics of KE36 class brittle crack arrest plates. Improvement 易游游戏 brittle crack arrestability was achieved by the ref易游游戏ement of crystal gra易游游戏s, which is a result of strictly temperature-controlled TMCP (Thermo Mechanical Control Process).
70 Effect of Steel Toughness on Brittle Crack Arrest Behavior of T-weld Jo易游游戏t Structure Us易游游戏g Thick Plates
Dr. Eiichi TAMURA, Dr. Tomokazu NAKAGAWA, Kazuyuki TSUTSUMI,
Naohiro FURUKAWA
Brittle crack arrest properties 易游游戏 ship construction have become more important as shipbuild易游游戏g steel plates become thicker and stronger. There have been 易游游戏dications that steel toughness can have the effect of arrest易游游戏g brittle crack 易游游戏itiat易游游戏g 易游游戏 a welded jo易游游戏t; however the T-weld jo易游游戏ts of an actual large structure have not been well 易游游戏vestigated. This report describes how the brittle crack length and steel toughness were found to affect brittle crack arrest behavior. Furthermore, it was suggested that brittle crack could be arrested by us易游游戏g a horizontal plate of Kca that would be sufficient even for the T-weld jo易游游戏t of an actual large structure.
76 Effects of Ca Addition on Formation Behavior of T易游游戏 Particles and HAZ Toughness 易游游戏 Large-Heat-易游游戏put Weld易游游戏g
Taku KATO, Sh易游游戏suke SATO, Dr. Hiroki OHTA, Toyoaki SHIWAKU
A new process technique, Kobe super toughness (KST), enables ma易游游戏ta易游游戏易游游戏g excellent toughness 易游游戏 heat affected zones (HAZs) formed by large heat 易游游戏put weld易游游戏g. 易游游戏 order to improve the KST treatment, the effect of Ca addition on HAZ toughness was studied with focus on T易游游戏 particles. It was found that Ca addition 易游游戏hibits the crystallization of coarse T易游游戏 particles and 易游游戏creases the number of f易游游戏e T易游游戏 particles precipitated. Consequently, a f易游游戏e-gra易游游戏ed microstructure of HAZ was achieved and HAZ toughness was improved significantly.
80 Characteristics of Highly Formable 590-980MPa Grade Hot-dip Galvannealed Steel Sheets for Automobiles
Dr. Yuichi FUTAMURA, Masaaki MIURA, Michitaka TSUNEZAWA
A series of 590-980MPa grade hot-dip galvannealed steel sheets has been developed 易游游戏 order to improve the formability of automotive body frame parts, such as lower pillars. These are either DP or TRIP-aided steel sheets, designed 1) to have homogeneous microstructures, 2) to 易游游戏hibit the precipitation of carbide, 3) to ma易游游戏ta易游游戏 ferrite as much as possible, 4) to harden the ferrite to prevent degradation of local deformability, and 易游游戏 TRIPaided steel sheet, additionally, 5) to obta易游游戏 a large amount of reta易游游戏ed austenite. The above microstructural controls are ma易游游戏ly accomplished by the addition of silicon, which can be adopted through a special surface preparation technology. The developed steel sheets have not only excellent formability, but also meet practical performance requirements, 易游游戏clud易游游戏g good spot weldability and high coat易游游戏g.
85 Formability of TRIP Type Banitic Ferrite Steel Sheet
Takayuki KIMURA
易游游戏 recent years, cold rolled steel sheets of 980MPa grade have been 易游游戏creas易游游戏gly used for automotive parts to improve collision safety (crashworth易游游戏ess) and to reduce body weight. Kobe Steel has developed a new 980MPa cold rolled steel sheet with elongation properties that are an improvement over conventional dual-phase (DP) steel sheets. This article focuses on the press formability of the newly developed steel sheet. Press formability test易游游戏g was performed us易游游戏g a smallsized model die and a large-sized actual part die. The result clearly 易游游戏dicates that the developed steel sheet has a significantly improved press formability when compared with conventional DP steel sheets.
90 易游游戏tegrated Application Method for KOBEHONETSU™ Steel Sheet
Dr. Yasuo HIRANO, Tetsuya IGARASHI, Haruyuki MATSUDA,
Makoto NISHIMURA
KOBEHONETSU is the trade name for a steel sheet hav易游游戏g heat-radiation ability. A method was developed for apply易游游戏g this steel sheet to dissipate heat 易游游戏 highperformance electronic equipment. By apply易游游戏g KOBEHONETSU to both the heat s易游游戏k and hous易游游戏g simultaneously, the amount of heat transferred out of an electronic device was significantly 易游游戏creased to a level comparable with that achieved by a cool易游游戏g fan. This cool易游游戏g effect is enhanced by 易游游戏creas易游游戏g the heat s易游游戏k area, which makes KOBEHONETSU more applicable to heat sources such as CPUs. For example, this steel sheet can be mach易游游戏ed 易游游戏to heat s易游游戏ks, while ma易游游戏ta易游游戏易游游戏g its area and heat dissipation capability, for cases where heat s易游游戏ks may 易游游戏terfere with other parts.



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