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59 巻, 3 号
選択された号の論文の7件中1～7を表示しています
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技術報告
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坂元 哲夫, 奥田 洋一郎, 今崎 正典1987 年 59 巻 3 号 p. 133-135
発行日: 1987/03/25
公開日: 2015/01/27
ジャーナル フリーPDF形式でダウンロード (1399K)
研究論文
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毛利 勝一, 柳本 智明, 森 和胤1987 年 59 巻 3 号 p. 136-140
発行日: 1987/03/25
公開日: 2011/09/23
ジャーナル フリー9%Ni steel castings with step-like sections of 60, 90 and 120mm were cast to examine the applicability of electromagnetic stirring to preventing the intergranular cracking. The macro- and microstructural observations were carried out and mechanical properties were checked in as-cast specimens. Though coarse columnar dendrites grew without stirring, arround 40% of each section thickness was occupied by equiaxed grains and secondary dendrite arms were refined with stirring. No-stirring test pieces had no ductility and their tensile strength decreased with the increase of casting thickness. However, the tensile strength of test pieces with stirring was stable independently of the thickness and had pretty good ductility, so it was suggested that the electromagnetic stirring was effective for preventing intergranular cracking of 9%Ni steel castings.抄録全体を表示PDF形式でダウンロード (787K) -
宮沢 信夫, 花崎 紘一, 石野 亨1987 年 59 巻 3 号 p. 141-146
発行日: 1987/03/25
公開日: 2011/09/23
ジャーナル フリーAs the effectiveness and advantage of repreated use of starch mold have been clarified, in the present work the properties of starch-added core, which are made from rebonded sand from green sand mold, bentonite and shell core sand, were examined. And also, recycling of rebonded sand from green sand mold which amount has increased by use of shell core sand, and its effective use for starch core sand were examined. The rebonded sand included residual bentonite and carbon, then its green sand strength was above 0.1kgf/cm2. Further, it had higher hot strength than the mold consisted of fresh silica sand and starch phosphate. This results from the reaction of the residual bentonite and starch phosphate at high temperature to from heat resistant substance of aluminum phosphate. Surface stability of the mold was excellent, the thermal contraction ratio was below 0.4%, and the addition of a small amount of zircon flour improved the thermal contraction ratio and thermal expansion ratio. These results confirmed that the rebonded sand from green sand mold can be satisfactorily used as the raw material for the starch core.抄録全体を表示PDF形式でダウンロード (731K) -
小林 俊郎, 山本 浩喜, 高林 幸央1987 年 59 巻 3 号 p. 147-152
発行日: 1987/03/25
公開日: 2011/09/23
ジャーナル フリーBehavior of retained austenite in austempered low alloy ductile iron developed by authors was examined by static tensile test at various temperatures. This iron was alloyed with Mn and Ni, and conducted with special austempering treatment. The ductility of this newly developed austempered ductile iron was found to be greater than those of conventional austempered ductile iron. TRIP was observed in the newly developed austempered ductile iron at about −75°C. This TRIP was somewhat different from a common TRIP caused by the deformation induced martensite. This different type of TRIP was found to be caused by the deformation twin. This was defined as “TRIP in a wide sence”. The elongation caused by such TRIP decreased with the increase of strain rate. This phenomenon was estimated to depend on the time period of twin formation in the fracture process and the stability of the retained austenite against deformation, and did not depend on the temperature rise in the specimen.抄録全体を表示PDF形式でダウンロード (785K) -
岩渕 義孝, 成田 英記, 一宮 義昭1987 年 59 巻 3 号 p. 153-158
発行日: 1987/03/25
公開日: 2011/09/23
ジャーナル フリーThick-walled spheroidal graphite irons can make it difficult to produce uniform castings on account of magnesium fading, graphite coalescence and segregation. In order to obtain superior ductilities through heavy-walled thickness, investigations were made of chemical composition and casting condition in spheroidal graphite iron castings, and then a rectangular test casting with 480mm wall thickness was evaluated.
Tensile elongation of thick-walled spheroidal graphite irons is found to depend primarily on degree of spheroidizing and secondarily on area ratio of ferrite. A thick-walled test casting is sound in internal qualities in view of porosity, segregation and magnesium fading. This casting has a decreasing tendency in degree of spheroidizing and number of graphite at inner positions, while the former is above 80%, the latter above 40/mm2. This casting shows an uniformity of tensile properties in which tensile strength is almost 38kgf/mm2 and elongation is more than 20%. Superior fracture toughness of more than 400kgf/mm3/2 is obtained through the wall thickness of this casting.抄録全体を表示PDF形式でダウンロード (714K) -
小松 真一郎, 塩田 俊雄, 中村 幸吉1987 年 59 巻 3 号 p. 159-163
発行日: 1987/03/25
公開日: 2011/09/23
ジャーナル フリーInfluence of graphite shape on fracture toughness and its transition behavior of ferritic cast iron was studied by testing four kinds of specimens whose graphite shapes were spheroidal, compacted vermicular and flake. Fracture toughness testing was carried out by means of an electrical potential method using 15mm thick CT test pieces at temperatures between 20°C and −150°C. At 20°C, when the matrix is ductile, elastic plastic fracture toughness JIC increases as graphite nodularity increases. However, at −150°C, when the matrix is very brittle, JIC becomes the highest in CV graphite. In case of spheroidal or CV graphite, a remarkable transition behavior in JIC takes place in a very low temperature range due to change of fracture mode to brittle from dectile. The higher the nodularity is, the higher the temperature at which transition behavior begins is. The tendencies mentioned above are considered to result mainly from the differences in effective sectional area, multiplicity in stress conditions and in cushioning effect by graphite.抄録全体を表示PDF形式でダウンロード (753K) -
杉本 繁利, 水野 慎也1987 年 59 巻 3 号 p. 164-168
発行日: 1987/03/25
公開日: 2011/09/23
ジャーナル フリーInfluence of austempering on the fatigue limit of spheroidal graphite cast iron was examind by changing isothermal transformation treatment conditions which affect strength, toughness and matrix structure. The fatigue limit was measured by Ono-type fatigue testing machine and flat-shaped test pieces. The fatigue limit of austempered spheroidal graphite cast iron is higher than that of pearlitic spheroidal graphite cast iron with the same hardness. In upper bainite transformation region, the fatigue limit becomes high as the retained austenite increases. The result is attributable to interference by work hardening and strain-induced martensitic transformation in the retained austenite against fatigue crack generation and propagation. In upper bainite transformation region, fatigue limit can be evaluated by the hardness and quantity of retained austenite and is given the following equation. Fatigue limit in flat-shaped test piece (kgf/mm2)
=9.31×10-2×hardness(HV (20))+2.21×10-1×Retained austenite(%)+8.25抄録全体を表示PDF形式でダウンロード (645K)
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