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81 巻, 8 号
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長崎 千裕, 木原 諄二1995 年 81 巻 8 号 p. 773-779
発行日: 1995/08/01
公開日: 2010/01/18
ジャーナル フリーγ温度域の変形抵抗におよぼす炭素量の影響について,従来の研究報告を総括した。その結果,γの耐力あるいは低ひずみの変形抵抗は,温度が低く,ひずみ速度が高いほど炭素による固溶硬化を顕著に示し,一方,高ひずみにおける変形抵抗は温度が高く,ひずみ速度が低いほど炭素による固溶軟化が顕著に現れることが明らかとなった。つまり,炭素は変形初期に変形抵抗を増大させるが,硬化率を著しく低下させている。
炭素のこのような作用を,γの積層欠陥エネルギーが炭素量の増加とともに減少することと関連づけて考察した。この点については基本原理に基づくシミュレーションが行われて検討が深められることを期待する。
また,低炭素鋼のγ温度域の変形抵抗におよぼす合金元素の影響については,鉄との原子半径の差が大きい元素ほど,変形抵抗を上昇させている。抄録全体を表示PDF形式でダウンロード (1483K) -
雀部 実, 高橋 典男, 高岡 利夫, 菊地 良輝, 河井 良彦, 三橋 賢司, 長塚 敏男, 古田 周良1995 年 81 巻 8 号 p. 780-785
発行日: 1995/08/01
公開日: 2009/06/19
ジャーナル フリーA sensor to determine calcium contents in molten metal is examined. The sensor is constituted of an oxygen sensor with an auxiliary electrode which is surrounded with a cap made of silica. 0.02 to 0.1 mass% of calcium contents in molten nickel can be detected by the sensor. Relation between calcium contents in the molten nickel and electromotive forces of the sensor can be expressed as following equation :
EMF/mV= -173log [%Ca] -423 ± 18
According to discussion on the basis of thermochemistry, it is revealed that the sensor acts as a chemical sensor of which output is determined by the thermochemical relation between calcium and oxygen.抄録全体を表示PDF形式でダウンロード (1426K) -
石井 不二夫, 日野 光兀, 伊東 裕恭1995 年 81 巻 8 号 p. 786-791
発行日: 1995/08/01
公開日: 2009/06/19
ジャーナル フリーThe deoxidation equilibrium of magnesium in liquid nickel and nickel-niobium alloys has been measured at the temperature ranges from 1873 to 1973 K and 1873 K respectively, by the use of magnesia crucible with a view to understanding the equilibrium between magnesium and oxygen, and the effect of niobium on the activity coefficients of oxygen and magnesium in liquid nickel.
For the deoxidation reaction in pure liquid nickel, i.e. :
MgO(s)=Mg+O
the effect of the temperature on the equilibrium constant, KMg(Ni) ( =aMg·ao/aMgO), was found to be :
log KMg(Ni)=-25500/T + 7.78
while the effect of magnesium on the activity coefficient of oxygen in liquid nickel was expressed to be :
logfMgO(Ni) = (-126300/T + 39.0)[%Mg] 0.003<[%Mg]<0.07
The deoxidation equilibrium of magnesium in liquid nickel-niobium alloys with 0.005-0.042 mass% magnesium has been measured up to 8 mass% niobium. The activity coefficients of magnesium and oxygen in liquid nickel-niobium alloys were given by the expression :
logfNbO(Ni) + logfNbMg(Ni) = -0.12[%Nb] [%Nb]<8抄録全体を表示PDF形式でダウンロード (1168K) -
水上 秀昭, 村上 勝彦, 北川 融1995 年 81 巻 8 号 p. 792-797
発行日: 1995/08/01
公開日: 2009/06/19
ジャーナル フリーTensile strength, ductility and sensitivity of internal crack formation of specimens sampled from continuously cast slabs and experimentaly cast small scale ingots were measured up to their solidification temperature by tensile tests. In the case of experimentaly cast ingots, manganese and sulphur contents were changed widely.
The results obtained are summarized as follows.
(1) In the brittle region, the tensile strength is below 1kg/mm2 and the apparent elastic modulus is about 100-200kg/ mm2.
(2) The brittle-ductile transition mainly depends on the existence of residual (Mn, Fe) S liquid film along the dendritic interface.
(3) The critical strain for internal crack formation varies from zero at ZST (Zero Strength Temperature) to about 1% at ZDT (Zero Ductility Temperature) in the brittle region and is found to be independent of strain rate or carbon contents. It was thought that these results come from the lack of molten metal in front of the crack in this tensile tests. On the contrary, it was suggested that the healing behavior of molten metal at the solidification front concerns to the crack formation in real steel strand.抄録全体を表示PDF形式でダウンロード (3176K) -
井上 紀明1995 年 81 巻 8 号 p. 798-802
発行日: 1995/08/01
公開日: 2009/06/19
ジャーナル フリーRecently, higher quality of the surface of cold rolling strip has been demanded. As a result, the quality level which was satisfactory before is not now. In particular, we need higher quality flat plate in order to produce a better gloss and mirror pattern for the outside plate of the car and wall plate.
Therefore, we investigated a relation between the vibration of machine and that of steel sheet in order to explain the source of chatter marks, which can be found only by skilled inspector. As a result it is confirmed that chatter marks which are generated by skin pass mill and tension leveler are resonance phenomena which arises due to the natural frequencies of the roll and the roll drive system as well as that of the transverse oscillation of steel sheet. To surpress the chatter marks, it is necesarry to control the vibration of the roll and the side walls.抄録全体を表示PDF形式でダウンロード (933K) -
脇田 淳一, 土師 純治, 河野 治, 中本 武広, 上尾 英孝, 高橋 学, 江坂 一彬1995 年 81 巻 8 号 p. 803-808
発行日: 1995/08/01
公開日: 2009/06/19
ジャーナル フリーThe conditions which prevent the occurrence of duplex grain structure of hot rolled steel sheets have been studied by using a model which can predict the strain induced transformation of ferrite from hot worked austenite. The obtained results are the following.
The occurrence of duplex grain structure depends upon the temperature schedule during finish rolling and it occurs in case that the sum of the consumption of fractional incubation time becomes 1.0 before the last reduction of finish rolling. The critical temperature for preventing the duplex grain structure reduces with increasing C and Mn, reducing the strip thickness and decreasing the rolling speed. The close agreement between these tendencies and the values calculated by a newly developed model to prevent the duplex grain structure has been obtained. On the basis of these results, a control technique of edge heating machine for preventing the duplex grain structure has been developed.抄録全体を表示PDF形式でダウンロード (2916K) -
剣持 一仁, 鑓田 征雄, 河澄 英輔, 小堀 克浩, 清野 芳一1995 年 81 巻 8 号 p. 809-814
発行日: 1995/08/01
公開日: 2009/06/19
ジャーナル フリーTo produce cold rolled stainless steel sheets efficiently in high speed rolling, surface brightness must be improved. The surface brightness of the sheets is strongly affected by oil-pits which occur on the surface of the sheets in cold rolling. As the number of oil-pits decreases, the surface brightness of the sheets is improved.
In this study, the morphology of oil-pits in actual cold rolling is observed by a microscope and SEM (Scanning Electron Microscopy). The effect of the surface roughness of the mother sheet on the occurrence of oil-pits in cold rolled sheet is examined with a laboratory-scale rolling mill.
The results obtained are as follows :
(1) Oil-pits occur at the bottom of micro-pits on the surface of the mother sheet, at the bottom of scratches which are marks due to the surface roughness of rolls and in the flat surface around the micro-pits and the scratches.
(2) It can be explained that oil pits in the flat surfaces around micro-pits are formed by the squeezing of rolling oil from the micro-pits.
(3) It can be explained that oil-pits at the bottom of the micro-pits and the scratches are caused by enclosure of rolling oil in the micro-pits and the scratches.抄録全体を表示PDF形式でダウンロード (12037K) -
高村 日出夫, 加藤 千昭, 望月 一雄, 森戸 延行1995 年 81 巻 8 号 p. 815-820
発行日: 1995/08/01
公開日: 2009/06/19
ジャーナル フリーA study was conducted on the formation of Zn-Fe and Fe-Al crystals in a molten Zn bath. Baths similar in composition to that of a CGL, were prepared in the laboratory and attention was paid on the cooling rate in Zn bath sampling.
When samples were cooled at lower cooling rates than 100°C/s, crystallization and crystal growth were observed in the Zn bath sample ingots. Higher cooling rates than 105°C/s inhibited the crystallization and crystal growth during cooling. In order to evaluate the presence of crystals in the Zn bath, it is necessary to employ a rapid cooling.
The type of crystal changed with the Al content of the bath. In a bath containing above 0.13mass% Al, Fe2Al5 formed. Below 0.13mass%, FeZn7, formed. From the results obtained with the rapid cooling technique, an equilibrium solubility curve for Fe and Al was estimated in the region where Fe2Al5 was crystallized. The curve was expressed as Log [Fe]2[Al]5=5.37-9354/T for Fe+5/2Al=1/2Fe2Al5. With this equation, the available Zn-Al-Fe ternary phase diagram in the literature was corrected at the Zn corner.抄録全体を表示PDF形式でダウンロード (3898K) -
小野寺 秀博, 阿部 太一, 大沼 正人, 木村 一弘, 藤田 充苗, 田中 千秋1995 年 81 巻 8 号 p. 821-826
発行日: 1995/08/01
公開日: 2009/06/19
ジャーナル フリーOne of the present authors has proposed a new concept about the Inherent creep strength determining the long term creep strength of ferritic steels. In the present study, effect of solute elements in the ferrite matrix on the Inherent creep strength of 0.2 and 0.3 mass% carbon steels was studied from a view point of atomic configurations such as atomic pairs. The equilibrium concentrations of solute elements and atomic pairs in the ferrite matrix were estimated by thermodynamic calculations with the sublattice model (Thermo-calc.) and the central atoms model, respectively. The following results are obtained; (1) The Inherent creep strength of carbon steels at 773K and 88MPa is proportional to concentrations of Mn and Mo in the ferrite and inversely proportional to those of C and Si. (2) A good correlation is observed between the Inherent creep strength and the concentrations of Mn-C and Mo-C atomic pairs. These atomic pairs seem to reduce the climb velocity of dislocations due to their large interaction energies with dislocations. Thus, it is concluded that the Inherent creep strength of carbon steels is controlled by Mn-C and Mo-C atomic pairs in the ferrite matrix.抄録全体を表示PDF形式でダウンロード (1157K) -
佐藤 俊司, 片田 康行, 永田 徳雄1995 年 81 巻 8 号 p. 827-832
発行日: 1995/08/01
公開日: 2009/06/19
ジャーナル フリーThe effect of crevice on low cycle fatigue behavior of a low alloy steel JIS SQV2A (equivalent to ASTM A533B cl. 1) for reactor pressure vessel was investigated in high temperature pressurized water at 561K and 7.8Mpa. Crevice were made on the specimen surface by attaching a pair of split collars of the same material. The dissolved oxygen (DO) concentration was varied from 10 ppb to 4000 ppb.
The fatigue life was found longer for creviced specimens than that for no creviced ones, especially for low strain range. The same trend was observed at low DO concentration levels. In case of no creviced specimen, fatigue life was notably reduced for DO concentrations higher than 1000ppb.
It can be concluded that the extention of fatigue life of the creviced specimens is due to the reduction of DO concentraion in the crevice.抄録全体を表示PDF形式でダウンロード (4408K) -
古君 修, 宇波 繁, 上ノ薗 聡, 小倉 邦明1995 年 81 巻 8 号 p. 833-838
発行日: 1995/08/01
公開日: 2009/06/19
ジャーナル フリーA prealloy steel powder which was Mn-less, contained 1Cr-0.3Mo and low oxygen was developed to improve compressibility of steel powder, tensile strength and toughness of sintered compact.
This newly developed steel powder showed high compressibility of green density of 7.15Mg/m3 at 690MPa of compacting pressure. This is derived from the decrease in solution hardening effect and Mn oxide on powder surface with decrease in Mn content.
The sintered compacts made from the new powder with 0.9% graphite addition gave a tensile strength of 900MPa and a Charpy absorbed energy of 17J, when compacted at 690MPa and sintered at 1150°C. These values were higher by 200MPa and 3J, respectively, than those of compacts made from a conventional 1Cr-0.3 Mo-0.7 Mn steel powder.
The strength and toughness improved, respectively, because of the production of fine pearlite structure and the decrease in Mn oxide with decrease in Mn content.抄録全体を表示PDF形式でダウンロード (4834K) -
石 建中, 戴 国政, 遠藤 孝雄1995 年 81 巻 8 号 p. 839-844
発行日: 1995/08/01
公開日: 2009/06/19
ジャーナル フリーFor the remaining creep life assessment, it is essential to evaluate the degree of structural degradation. In the present study, accelerated creep tests have been employed to assess the degree of structural deterioration of a 2.25 Cr-1Mo steel which was service-exposed for 11 years as a power plant component. The experimental results showed that strain rate over a wide rage of strain is expressed by the equation; lnε =lnε0+Sε, where ε0 is the imaginary initial creep rate and S is the strain rate acceleration factor. The magnitudes of ε0 and S are given by the following equations; ε0=A0σ0nexp(-Q0/RT). and S=Asσ0-nsexp(Qs/RT), where A0 is the mechanically defined structure factor, σ0 is the initial stress, n is the stress exponent (9.5), Q0 is the activation energy (429 kJ/mol), Qs is 24kJ/mol, As is a constant, and ns is 0.98. Comparing these results with those of prestrained materials, it was found that the magnitudes of A0, As and ns are dependent upon the structural deterioration while those of n, Q0 and Qs are independent of thermo-mechanical history. This means that the rate controlling mechanism is independent of structural deterioration. These historydependent parameters allow us the quantitative assessment of the structural deterioration of service-exposed materials.抄録全体を表示PDF形式でダウンロード (1129K) -
馬場 栄次, 金丸 修, 阿部 冨士雄, 八木 晃一1995 年 81 巻 8 号 p. 845-850
発行日: 1995/08/01
公開日: 2009/06/19
ジャーナル フリーThe effect of cold-rolling on creep deformation has been investigated for 10Cr-30Mn austenitic steels containing 0.003, 0.11 and 0.55 mass% carbon. After 20% cold-rolling at room temperature, the specimens were subjected to creep test at 873K for up to about 10000h. The test results were compared with those of solution-annealed specimens. The cold -rolling caused a decrease in minimum creep rate εmin and an increase in time to rupture tr at high stresses and short times. At low stresses and long times, however, the effect of cold-rolling on the εmin and tr depended on carbon concentration and test duration. The tr of the specimens was described by tr=1.45/(εmin·Ωp), where, Ωp is the creep damage parameter given by Ωp=dlnε/dε. Both the εmin and Ωp are correlated with the microstructural evolution during creep, such as the precipitation of σ phase, M23C6 and the recrystallization of deformed grains produced by cold-rolling.抄録全体を表示PDF形式でダウンロード (7712K) -
田中 浩司, 斎藤 卓1995 年 81 巻 8 号 p. 851-856
発行日: 1995/08/01
公開日: 2009/06/19
ジャーナル フリーHigh-temperature oxidation behavior of γ-Al2O3 slurry coated Fe-20Cr-5Al based thin foil (50μm in thickness) for a catalytic converter has been investigated. An anomalous foil expansion during high-temperature oxidation was observed in a case that the γ-Al2O3 slurry contains Ce3+ or La3+ or Y3+. The expansion was accelerated by minor additives to the stainless steel foil such as Nb, Ti, Ta, or Mo. On the other hand, the expansion was effectively suppressed by a small addition of rare-earth elements or yttrium to the stainless steel foil. It has been concluded that the foil expansion was resulted from a creep deformation by a compressive stress which is accumulated in the course of lateral growth of α-Al2O3 scale formed between the foil and the coated layer.抄録全体を表示PDF形式でダウンロード (14727K) -
金子 道郎, 阿部 征三郎1995 年 81 巻 8 号 p. 857-861
発行日: 1995/08/01
公開日: 2009/06/19
ジャーナル フリーAustenitic stainless steels with low carbon content have good corrosion resistance in nitric acid solutions. However, these steels are susceptible to corrosion in nitric acid solutions which contain highly oxidizing ions such as Cr2O72-, Run+ etc. One of these is called "End Grain Corrosion" or "Tunnelling Corrosion".
In this type of corrosion, a part of the cross-section of plate is preferentially attacked severely. In this study, it was clarified that the end grain corrosion was caused by intergranular corrosion (IGC) at phosphorus segregated areas which were induced during casting. And it was also found that the decrease of P content less than 0.015%, and heat treatments to reduce segregation of P were very effective to prevent the end grain corrosion.抄録全体を表示PDF形式でダウンロード (14469K) -
遠藤 孝雄, 石 建中, 増山 不二光1995 年 81 巻 8 号 p. 862-867
発行日: 1995/08/01
公開日: 2009/06/19
ジャーナル フリー2.25Cr-1Mo鋼の定加重クリープ試験において,歪速度の対数と真歪の間に線型の関係が存在し,この関係は式(1)で表現される。ここでは,簡単な思考実験と転位モデルで構成方程式に表れるパラメーターの物理的意味を考察し以下の結論を得た。
1)定応力クリープ試験の定常クリープ速度と仮想的初期歪速度は,原理的には一致する。一致しない場合は,歪速度が速い場合,歪速度が低く,クリープ変形中に生じる析出物の大きさや分布,組成などの変化が顕著な場合,変形中の酸化減肉による応力増加が著しい場合などである。
2)クリープ変形中の加工硬化率が一定である場合と,加工硬化が放物線則に従う場合のS値を定式化してその大きさを調べた。その結果,前者においては,S値が応力の逆数に比例し,後者においては応力の2乗に逆比例することが分かった。モデルに基づくS値の大きさは実測値とほぼ一致する。
3)仮想的初期歪速度と歪速度加速因子を用いて材料の組織劣化度を判定するには,長時間クリープ試験よりも短時間クリープ試験の方が望ましい。抄録全体を表示PDF形式でダウンロード (1281K)
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