電気製鋼

論説

硫化物形態制御型快削鋼の被削性に及ぼす硫化物形態の影響

原稿種別: 総説
専門分野: 特殊鋼
2002 年 73 巻 1 号 p. 5-12
発行日: 2002年
公開日: 2002/02/08

DOIhttps://doi.org/10.4262/denkiseiko.73.5

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Since lead contaminates the environment, the various types of shape-controlled-sulfide (SCS) free machining steel, in which sulfide shapes are controlled to be spherical, have been developed to replace the leaded ones. However, in these SCS free machining steels, the effect of aspect ratio, size, and composition of sulfides on the machinability has not been revealed clearly. Authors evaluated the effect of sulfide shape on the machinability and investigated the relationship between the performance of sulfide coating on the tool surface and the sulfide composition. The results are as follows. 1) The tool life, VB₁₀₀, in turning with carbide tools is almost independent of the aspect ratio and the size of sulfides, while it is remarkably improved with the existence of calcium-manganese sulfide ((Ca, Mn)S) coating which has superior lubrication. 2) The processing efficiency, VL₁₀₀₀, in boring with HSS drills is improved with the decrease in aspect ratio and the increase in size of sulfides. It suggests that the sulfides in the SCS free machining steel should contain (Ca,Mn)S with the lower aspect ratio and the larger size in order to secure the sufficient machinability both in turning and boring.

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加工硬化と析出硬化を強化機構とするCu含有鋼の特性に及ぼす合金元素の影響

原稿種別: 総説
専門分野: 特殊鋼
2002 年 73 巻 1 号 p. 13-21
発行日: 2002年
公開日: 2002/02/08

DOIhttps://doi.org/10.4262/denkiseiko.73.13

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Authors developed the low C(0.08%) Cu-bearing steel with ferrite-pearlite structure, which is strengthened by cold work and subsequent aging. Regardless of cold work, 0 to 50% reduction in height, the hardness of 1.5%Cu steel reaches the peak at the aging around 773K for 3.6ks. By this aging after 50% cold work, 1.5%Cu steel shows the largest increment in hardness, 150HV in all, and the highest hardness itself, 300HV, surpassing 2%Cu one. The 1.0% Ni is sufficient to prevent the surface hot cracking due to the grain boundary penetration of Cu-rich molten phase below the oxide scale in 1.5%Cu steel. The cold worked and aged steel with 1.5%Cu and 1.0%Ni possesses the tensile strength equivalent to the quenched and tempered medium C steel and the fatigue ratio superior to it.

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軸受鋼の転動疲労特性に及ぼすＮｉ添加の影響

原稿種別: 総説
専門分野: 特殊鋼
2002 年 73 巻 1 号 p. 23-28
発行日: 2002年
公開日: 2002/02/08

DOIhttps://doi.org/10.4262/denkiseiko.73.23

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In order to extend the rolling contact fatigue life, the effect of Ni addition was investigated on the fatigue life and the microstructural change of two bearing steels, 1.2C-1.5Cr-1Si at 423K and carburized SCr420 at RT. The addition of 0.5 to 2% Ni lengthens the lives of both steels remarkably twofold to tenfold. Under the contact surface there was observed the white band, which is ferrite structure without carbide in it. The band emerges at the depth with the shear stress amplitude, 930MPa or higher estimated by FEM, and it stretches both inward and outward 200μm in length. And the cracks originate from their edges. The Ni addition retards the evolution of the white band and so it prolongs the fatigue life.

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炭素量を変化させた焼入鋼の靭性に及ぼすボロンの影響

原稿種別: 総説
専門分野: 特殊鋼
2002 年 73 巻 1 号 p. 29-35
発行日: 2002年
公開日: 2002/02/08

DOIhttps://doi.org/10.4262/denkiseiko.73.29

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The effect of boron addition was investigated on the toughness of quenched steels whose carbon content extends from 0.2 to 0.8 percent. The results are as follows.
(1) Impact values of boron added steels are higher than boron-free steels' over the above carbon range.
(2) Boron increases effectively both crack initiation and propagation energies.
(3) Typically in the case of 0.8% carbon, the dominant fracture mode is transgranular in the boron added steel, while it is intergranular in the boron-free. It suggests that the boron excludes phosphorous segregating at the grain boundaries and consequently it strengthens the grain boundaries.

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高温焼戻し型ボルト用鋼の耐遅れ破壊性に関する研究(2)

原稿種別: 総説
専門分野: 特殊鋼
2002 年 73 巻 1 号 p. 37-43
発行日: 2002年
公開日: 2002/02/08

DOIhttps://doi.org/10.4262/denkiseiko.73.37

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For fasteners the author had designed the steel NiCrMoV(0.4C-0.1Si-0.3Mn-1Ni-1Cr-1Mo-0.3V) tempered at 873K, which showed the delayed fracture life at a higher stress level in a static bending test substantially longer than SCM440(0.4C-0.3Si-0.7Mn-1Cr-0.2Mo) tempered at 703K to the equivalent tensile strength 1500MPa. The cathodic charge introduced a larger amount of diffusible hydrogen into NiCrMoV. The finely dispersed M₂C or MC precipitates in NiCrMoV trapped tightly some portion of the hydrogen, which didn't diffuse at all at RT. The obtained results suggest that the hydrogen trapping effect of the carbides retards the initiation of hydrogen-induced cracking and so extends the delayed fracture life of NiCrMoV tempered at higher temperatures.

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溶製法で製造したVC分散型高剛性鋼の諸特性

原稿種別: 総説
専門分野: 特殊鋼
2002 年 73 巻 1 号 p. 45-52
発行日: 2002年
公開日: 2002/02/08

DOIhttps://doi.org/10.4262/denkiseiko.73.45

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The higher elastic modulus is so beneficial to slim automotive components that a large amount of rigid carbide has been dispersed in some steels through the powder metallurgy. Authors applied the ingot metallurgy less expensive to prepare VC dispersed steels, 2%C-8%V and 3% C -12%V. The hot workability of the billets is comparable to ones in a high speed steel, SKH51. Their Young's modulus as normalized is 233 to 243GPa which is significantly higher than 208GPa for conventional steels. The modulus doesn't vary when they are quenched and tempered to 255 to 461HV. Their 0.2% PS is essentially equal, while the elongation and the reduction in area are smaller compared with carbon or high strength steels heat-treated to the equivalent hardness.

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解説

自動車材料－環境の世紀に向かって－

原稿種別: 技術報告
専門分野: 特殊鋼
2002 年 73 巻 1 号 p. 53-60
発行日: 2002年
公開日: 2002/02/08

DOIhttps://doi.org/10.4262/denkiseiko.73.53

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The 21st century is called the Environmental Century, and therefore automobiles shall be improved to be continuously accepted by the environment-conscious society. In this review, the requests to automobiles from the society are outlined and some material technologies are discussed as countermeasures against CO₂and scrap problems.

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技術資料

超清浄軸受鋼製造プロセスの開発

原稿種別: 研究論文
専門分野: 特殊鋼
2002 年 73 巻 1 号 p. 61-66
発行日: 2002年
公開日: 2002/02/08

DOIhttps://doi.org/10.4262/denkiseiko.73.61

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For the miniature races and balls in spindle motors of hard disc drives, there have been required the clean bearing steel with infinitesimal oxides, Ti inclusions and sulfides which originate acoustic noises. Chita Plant, Daido Steel, has established the new process, MRAC-SSS (Multi-function Refining and Advanced Casting - Special Solution and Soaking), to manufacture the ultra clean bearing steel. Its features are as follows.
(1) The tailored multi-functional refining process employing both LF and RH realizes the extremely low [O] and [Ti] levels in the molten steel.
(2) The tight sealing of the tundish prevents completely the secondary oxidation of the molten steel during continuous casting.
(3) The optimized reheating schedule for the cast bloom contributes to the siginificant reduction of Ti inclusions in number and size in the rolled wire or rod.
The ultra clean bearing steel manufactured through the new process proves to possess the remarkably prolonged contact rolling fatigue life.

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高周波輪郭焼入れ歯車用鋼の開発

原稿種別: 研究論文
専門分野: 特殊鋼
2002 年 73 巻 1 号 p. 67-72
発行日: 2002年
公開日: 2002/02/08

DOIhttps://doi.org/10.4262/denkiseiko.73.67

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The induction contour hardening is an effective process to strengthen automotive transmission gears with the minimal distortion. Its heating time, however, is too short, 0.15 to 0.3sec, to fully austenitize the ferrite-pearlite structure in normalized conventional steels, such as S45C, which are now quenched and tempered before the hardening. Authors extracted the effect of alloying elements on the austenitizing behavior and then designed a new steel, 0.55C-0.1Si-1.2Mn-0.1Cr-0.001B(in wt%). It bears almost the single phase of pearlite as normalized and is transformed into the homogeneous martensite by the contour hardening. The gears in the new steel contour hardened without the pre-heat-treatment possess the fatigue strength equivalent to the carburized ones in SCr420 and the impact strength three times as large as them, still the less distortion than them.

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大同の歯車用肌焼鋼

原稿種別: 研究論文
専門分野: 特殊鋼
2002 年 73 巻 1 号 p. 73-77
発行日: 2002年
公開日: 2002/02/08

DOIhttps://doi.org/10.4262/denkiseiko.73.73

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