Tetsu-to-Hagane

The Effect of Silicon on the Formation of CO Blowholes during Solidification of Iron

Hiroyuki NOMURA, Kazumi MORI, Toshihiro NAKASHIMA

1979 Volume 65 Issue 6 Pages 583-590
Published: May 01, 1979
Released on J-STAGE: February 22, 2010

DOIhttps://doi.org/10.2355/tetsutohagane1955.65.6_583

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In order to clarify the effect of silicon addition on the formation of CO blowholes, an experimental study has been made of uni-directional solidification of iron at a solidification rate of about 5mm/min. The composition range explored was: C 0.1%, O 0.006-0.011% and Si 0.01-0.04%. The critical concentration of silicon for the formation of macroblowholes has been determined to be 0.022 to 0.025%. The influence of oxygen on the critical concentration of silicon was small. The effect of silicon on the formation of macroblowholes could be explained by postulating chemical equilibrium in Fe-C-Si-O melt in the interdendritic region. It is presumed that macroblowholes are formed with the similar mechanism as that in the case of no addition of silicon.

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Interaction between the Formation of CO Blowholes and Manganese-silicate Oxides during Solidification of Iron

Hiroyuki NOMURA, Kazumi MORI, Katsuyuki KISAKA

1979 Volume 65 Issue 6 Pages 591-598
Published: May 01, 1979
Released on J-STAGE: February 22, 2010

DOIhttps://doi.org/10.2355/tetsutohagane1955.65.6_591

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In order to clarify the effect of manganese addition on the formation of CO blowholes, a study has been made of uni-directional solidification at a solidification rate of about 5mm/min. The composition range explored was: C 0.08-0.12%, O 0.005-0.01%, and Mn 0.2-0.6%. The critical concentration of manganese for the formation of macroblowholes has been determined to be 0.29 to 0.31%. In the present study. about 0.01% of silicon contained in the starting specimen influenced the chemical reaction in the interdendritic liquid. The effect of oxygen on the critical concentration of manganese was small. The effect of manganese on the formation of macroblowholes could be explained by postulating chemical equilibrium in the interdendritic liquid. It is presumed that macroblowholes are formed with the similar mechanism as in the Fe-C-O and Fe-C-Si-O systems.

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Blistering and Hydraulic Removability of Scale Films of Rimmed Steel at High Temperature

Fumio MATSUNO

1979 Volume 65 Issue 6 Pages 599-607
Published: May 01, 1979
Released on J-STAGE: February 22, 2010

DOIhttps://doi.org/10.2355/tetsutohagane1955.65.6_599

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Under the protection from the oxidation, rimmed steel plates are heated to temperatures between 800°C and 1250°C. Then they are oxidized in air for very short periods. Blistering and hydraulic removability of scale films of them are studied.
Blisters, which are caused by the compressive stresses such as oxide growth stress and thermally induced stress, are small round spots at first, and they grow rapidly. The periods from the start of oxidation to the appearance of blisters are measured at various conditions.
The removability of scale films is measured by the water jet of 1, 4 and 15kg/cmcm². Scale films with some blisters are removed readily by the water jets.
Based on the above results, the cohesion or adhesion of scale films at high temperature is discussed.

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Cooling Characteristics and Heat Transfer Coefficients during Fog Cooling of Hot Steel Plates

Masashi MITSUTSUKA, Keiji FUKUDA

1979 Volume 65 Issue 6 Pages 608-616
Published: May 01, 1979
Released on J-STAGE: February 22, 2010

DOIhttps://doi.org/10.2355/tetsutohagane1955.65.6_608

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In forced-cooling of hot steel products, air-stomized fog cooling is suitable for the soft cooling whose rate is between those of forced-air cooling and water spray cooling. In fog cooling both water and air considered to take part in the cooling. It is well known that when fog impinges a surface to be cooled at high speed, heat flux transferred from the surface to the fog increases with impinging speed because of unstable vapor films on the surface. It has not been clarified yet whether heat flux increases or not when fog impinges the surface at a slow speed.
The heat transfer phenomena have been studied when hot steel specimens are cooled with fog which is atomized with low speed air. The main results obtained are as follows:
(1) When fog impinges a surface at a slow speed, air makes water atomized but scarcely contributes to heat transfer.
(2) Cooling capability of fog is dependent on only the water flux to the surface.
(3) The cooling capability of air-atomized fog is nearly equal to that of pressure-atomized one, for the same water flux.
In this paper, in addition to the above results, the differences in heat transfer mechanism between the upper and the lower surface of steel plate positioned horizontally and the influences of surface condition of a steel plate on heat transfer are discussed.

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Effect of Cold Working and Heat Treatment on Stress Corrosion Cracking Behavior of Duplex Stainless Steel

Kikuo TAKIZAWA, Yasuhiko SHIMIZU, Eisaku YONEDA, Hokoto SHOJI, Imao TA ...

1979 Volume 65 Issue 6 Pages 617-626
Published: May 01, 1979
Released on J-STAGE: February 22, 2010

DOIhttps://doi.org/10.2355/tetsutohagane1955.65.6_617

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The effects of cold drawing and heat treatment on the stress corrosion cracking (SCC) behavior of stainless steel having two phases of α and γ were studied in boiling 42% MgCl₂ solution. It was found that the effect of cold drawing on SCC susceptibility was remarkable, and when applied stress was 8.3, 25kg/mmmm² or 38% of Y.S., the maximum SCC susceptibility was observed in the specimens drawn at 15% and 60% after solution treatment. The critical stress on the SCC was observed in a undeformed specimen, but it was not observed in those which were subjected to cold drawing. The restraining effect of α on the propagation of cracks was not observed in all the specimens, on the contrary, the cracks were propagated in α preferentially in the 60% cold drawn specimen. On aging at 475°C, the change in hardness showed a two-stage hardening behavior. At the second stage of the hardening (aging for 100h or longer) the SCC susceptibility of the cold drawn specimen was decreased and did not fail event after 10⁴min. This phenomenon may be interpreted by assuming the two phases separation of α-phase. On aging at 700°C from 5 to 17h or more, the SCC susceptibility was excessively increased, and at the same time the transformation of α→γ+σ occurred. This transformation had a detrimental effect on the SCC susceptibility because a volume fraction of α was varied, and furthermore σ promoted local corrosion and embrittlement of the specimens.

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Inhomogeneous Textures in Hot Rolled Columnar Crystals of 18Cr-8Ni and 25Cr-2ONi Stainless Steels

Hideo ABE, Fumie TOGAWA, Yoshio KINOSHITA, Kosaku NAKAGAWA

1979 Volume 65 Issue 6 Pages 627-636
Published: May 01, 1979
Released on J-STAGE: February 22, 2010

DOIhttps://doi.org/10.2355/tetsutohagane1955.65.6_627

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Variations of texture through the thickness of hot-rolled plate have been studied in 18Cr-8Ni and 25Cr-20Ni steels. Experiments were made on columnar crystal specimens cut from the continuously cast slabs, rolled at 800°C or 1000°C with one-pass of 50% reduction and subsequently quenched into water.
The textures of the surface region were nearly (001) [110]. One of the inner texture components could be approximately related to the surface texture by a rotation about [111] or [111] axis through an angle which increased with the distance below the surface. The variations of texture through the thickness were accounted for on the basis of the slip line field in the entry region of the roll gap.

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Analysis of Fatigue Fractured Surface of Various High Tensile Strength Steels at the Range of Low Stress Intensity Factor

Masae SUMITA, Norio MARUYAMA, Iku UCHIYAMA

1979 Volume 65 Issue 6 Pages 637-645
Published: May 01, 1979
Released on J-STAGE: February 22, 2010

DOIhttps://doi.org/10.2355/tetsutohagane1955.65.6_637

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The fatigue tests were performed to obtain thresholds of stress intensity factor range, ΔK_th, by the incremental step method in air at R=0.1 using HY140, HY240, HP9-4-20, 18Ni (200) maraging, 18Ni (250) maraging, MAS-MA-164, and PH13-7 steels. The informations obtained from fracture surfaces were analyzed in the low stress intensity factor range. The results are as follows;
1) The fracture surface consists of unit region, which is a bundle of lath-like-pattern, and flat area just like a grain boundary.
2) The size of the fracture unit incrcases with ΔK.
3) The size of units is about one half of the pre-austenitic grain size at the threshold region.
4) The width of lath-like-patterns is 0.2 to 1.0μm at the theshold region. This width is almost same as the lath width. This width increases with ΔK.
5) The direction of the bundle of the lath-like-pattern is quite randum to the direction of the macroscopic growth. With ΔK increasing, however, the direction of the bundle approachs to the macroscopic direction of crack growth.
6) The maximum intergranular fracture rate generally arises at about 30kg/mm^3/2 of ΔK. The maximum values of steels containing no carbon is two or three times as large as thoes of steels containing carbon.
7) The ΔK_th of steel scontaining carbon is generally lower than that of steels containing no carbon.

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Effects of Test Temperature on Fatigue Damage Process of Austenitic Steel

Yuichi SEKI, Kenichi NISHIWAKI, Toshio FUJITA

1979 Volume 65 Issue 6 Pages 646-654
Published: May 01, 1979
Released on J-STAGE: February 22, 2010

DOIhttps://doi.org/10.2355/tetsutohagane1955.65.6_646

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The temperature dependence of fatigue damage process was investigated using three austenitic steels, namely Fe-30Ni alloy which is metastable austenite, Fe-38Ni alloy which is stable austenite at room temperature and Fe-25Ni-16Cr alloy which has a low stacking faults energy of austenite. The variatiou of plastic strain amplitude was measured at the temperatures of 100°C and 200°C, and surface morphology and substructures were observed by optical and transmission electron microscopes. The main results obtained are as follows;
1) The hardening tendency in metastable austenitic region results from the work hardening of austenite and formation of martensite, and the decrease of hardness is considered to be due to the tempering effect of martensite.
2) The higher the stacking faults energy of austenite is, the more the hardening tendency is found, that is, this is attributed to the formation of the dislocation cells.
3) Initial cracks are apt to occur mainly at grain boundaries in the case of high stress levels and at slip bands in the case of low stress levels. The rate of occurrence of cracks at slip bands is increased with the formation of surface striation.

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Unstable Plastic Flow and Mechanical Properties of Substitutional Iron Alloys with Polygonized Ultrafine Grain Microstructure

Masato ENOMOTO, Ei-ichi FURUBAYASHI

1979 Volume 65 Issue 6 Pages 655-664
Published: May 01, 1979
Released on J-STAGE: February 22, 2010

DOIhttps://doi.org/10.2355/tetsutohagane1955.65.6_655

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A study was made of the strength-ductility relation-ship at ambient and low temperatures in substitutional iron alloys with about 2 at% Al, Si, Ti, Cr, Mn, Ni or Mo which were cold rolled and subsequently annealed to attain recovered and/or partially recrystallized structure composed largely of polygonized subgrains of 1μm or less. The deformation behavior in tension of these ultrafine-grained iron alloys was shown to be characterized by very small elongation owing to plastic instability, which caused necking immediately after the yielding or during the propergation of the Lüders bands. It was found, however, that some of solute elements manifested a remarkable effect of improving the ductility and that the effect was fully maintained in the presence of the third element, such as Nb, which was added to retain high strength pertaining to recovered state as a result of a well-known retarding effect on recrystallization.
The occurrence of plastic instability was considered to be intimately related to the change in the Lüders strain with the deformation temperature and grain size of material. Accordingly, various factors which may affect the Lüders strain, i. e. the mode of slip, dislocation structure and distribution of interstitial atoms, were investigated in terms of the influence of substitutional solutes. A high dislocation multiplication rate was found to be the most distinctive feature of the alloys which exhibited large elongation at low temperature.

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Effects of Aging Conditions and Strain Rate on Rupture Elongation of 13Ni-15Co-10Mo-0.2Ti (280kg/mm²-Grade) Maraging Steels

Kô SOENO, Kazuo TAGUCHI, Masatoshi TUCHIYA

1979 Volume 65 Issue 6 Pages 665-673
Published: May 01, 1979
Released on J-STAGE: February 22, 2010

DOIhttps://doi.org/10.2355/tetsutohagane1955.65.6_665

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Tensile strength and elongation have been measured in aged 13Ni-15Co-10Mo-0.2Ti, 14Ni-10Co-10Mo and 14Ni-15Co-7Mo maraging steels. The temperature range in aging has been varied from 450°C to 575°C for the 13Ni-15Co-10Mo-0.2Ti steel, and from 425°C to 475°C for the 14Ni-10Co-10Mo and 14Ni-15Co-7Mo steels. A cross head speed in a tensile test has been ranged from 1mm/min to 0.005mm/min. The effect of strain rate on tensile elongation has been investigated in relation to aging temperature and time.
In tensile tests of the maraging steels in which fine coherent precipitates are considered to be formed, it is observed that tensile elongation is decreased with decreasing a strain rate. The elongation decrease in a low strain rate is also observed in tensile tests of the 13Ni-15Co-10Mo-0.2Ti steel in which coarse precipitates are contained by over-aging. It is considered that the elongation decrease in a low strain rate is attributed to both stress concentrations resulting from plastic deformation characteristics of the aged maraging steels and hydrogen diffused to regions having intense stress concentrations.

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Fog Spread and Water Distribution Discharged from a Crossflow Air-water Fog Nozzle

Masashi MITSUTSUKA, Keiji FUKUDA

1979 Volume 65 Issue 6 Pages 674-680
Published: May 01, 1979
Released on J-STAGE: February 22, 2010

DOIhttps://doi.org/10.2355/tetsutohagane1955.65.6_674

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As a forced-cooling method for hot steel products, air-atomized fog cooling is suitable for an intermediate cooling level between forced-air-cooling and water spray cooling. If conventional fog nozzles are used in steel processing lines, these nozzles will not be able to form proper fog for a long time, because small holes in these nozzles very often suffer clogging. Furthermore, there are serious problems of air economy and high level noise from high pressure atomizing.
A newly improved fog nozzle enables water to be atomized with air under a pressure as low as 300 to 1000mmH₂O. The feature of this nozzle is its simple design, a water pipe being attached to the end of a air pipe at right angles. One of the advantages of this nozzle is its capability of feeding water in a wide range of 0.1 to 10l/min through a comparatively large water hole of inner diameter 3 to 6mm.
This report describes the design of this nozzle. The characteristics of a single fog stream from this nozzle are also shown, including atomization behavior and condition, fog spread, water distribtion in fog streams, influences of water and air pressures on atomization.

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Toughness of High Manganese-Chromium Austenitic Steels at Liquid Helium Temperature

Hirofumi YOSHIMURA, Takaharu SHIMIZU, Hiroshi YADA, Kazunori KITAJIMA

1979 Volume 65 Issue 6 Pages 681-686
Published: May 01, 1979
Released on J-STAGE: February 22, 2010

DOIhttps://doi.org/10.2355/tetsutohagane1955.65.6_681

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In order to examine the applicability of high manganese-chromium austenitic steels to cryogenic use, Charpy impact test was made at liquid helium temperature. A steel with 25Mn-5Cr-1Ni as base composition exhibited good toughness in impact testing without any sign of martensite transformation induced by impact deformation.
Niobium bearing steel, which was grain-refined, showed slightly lower impact energy. The cause for this was considered to be the local strain hardening in fine-grained steel, in which the mode of crack propagation was changed. Increment of nickel content to the material with base composition increased toughness. 15Mn-5Cr-5Ni steel exhibited good toughness even though the trace of martensite transformation caused by low stability of austenite was found. As the results above, it was shown that 25Mn-5Cr-1Ni austenitic steels have an applicability to cryogenic use.

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High Strength Sheet Steel and Its Formability in Automotive Applications

Itaru AOKI

1979 Volume 65 Issue 6 Pages 687-697
Published: May 01, 1979
Released on J-STAGE: February 22, 2010

DOIhttps://doi.org/10.2355/tetsutohagane1955.65.6_687

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[title in Japanese]

Tanekazu SOMA, Kazuhiro S. GOTO

1979 Volume 65 Issue 6 Pages 698-703
Published: May 01, 1979
Released on J-STAGE: February 22, 2010

DOIhttps://doi.org/10.2355/tetsutohagane1955.65.6_698

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[title in Japanese]

[in Japanese], [in Japanese]

1979 Volume 65 Issue 6 Pages 704-709
Published: May 01, 1979
Released on J-STAGE: February 22, 2010

DOIhttps://doi.org/10.2355/tetsutohagane1955.65.6_704

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[title in Japanese]

[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...

1979 Volume 65 Issue 6 Pages 710-712
Published: May 01, 1979
Released on J-STAGE: February 22, 2010

DOIhttps://doi.org/10.2355/tetsutohagane1955.65.6_710

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