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45 巻, 11 号
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研究論文
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片島 三朗, 重松 清, 里吉 昭宣1973 年 45 巻 11 号 p. 945-953
発行日: 1973/11/25
公開日: 2012/09/21
ジャーナル フリーThe objective of the present investigation is to elucidate the mechanism and causes of the movement of sand mold wall to find out methods for its prevention. Heating and pouring tests were performed to study the influences of various factors which caused mold wall movement in different molding sands. The influences of the following factors were studied : mold density and hardness, additives, molding methods such as green, dry and self-hardening sand mold and different molding materials. Results obtained are as follows;
(1) The amount of mold wall movement reduced with high mold hardness and high density.
(2) The amount of mold wall movement in self-hardening sand and dry sand was considerably less than in green sand.
(3) Mold wall movement in zircon sand mold, cromite sand mold and olivine sand mold was smaller than in silica sand mold.
(4) The addition of additives such as seacoal, pitch, wood-flour, ferrous oxide and cornstarch in green sand mold resulted in the reduction in mold wall movement which was proportional to the amount of the additives except for wood-flour. Especially, there was a considerable decrease in mold wall movement by the addition of 7% seacoal.
(5) The mechanism of the movement of mold wall is supposed to occur in three stages. The first stage is the inner movement of mold wall due to the thermal expansion of sand grains by shock heating. The second stage is the outer movement of mold wall which is attributed to mold strength, formation of moisture-condensed layer and so on. The third stage is the more outer movement, which results from the formation of eutectic graphite of cast iron.抄録全体を表示PDF形式でダウンロード (758K) -
中野 耕作, 鈴木 健司, 雄谷 重夫1973 年 45 巻 11 号 p. 954-961
発行日: 1973/11/25
公開日: 2012/09/21
ジャーナル フリーThe present work concerns particularly with inverse-segregation in Cu-Sn alloys examined from the effects of solidification variables. The allloys were unidirectionally solidified so that both contraction pressure of solid skin and gas pressure in the hot spot are negligible.
Inverse-segregation initiates in the early stage of unidirectional solidification. A faster growth rate accerelates inverse-segregation. Similar extent of inverse-segregation is found both in the columnar and equiaxed structures. Growth twinning structure often found in the aluminum-base alloys results in freedom from inverse-segregation. Inverse-segregation is attributed to the interdendritic flow of solute-rich liquid caused by solid contraction.抄録全体を表示PDF形式でダウンロード (1106K) -
近藤 靖彦, 磯谷 三男, 上田 俶完1973 年 45 巻 11 号 p. 962-971
発行日: 1973/11/25
公開日: 2012/09/21
ジャーナル フリーThe process of fracture in type-D graphite iron cast in metal mold is discussed by means of micro-observation of fractured surface on tensile stress and bending stress. The three dimentional array of dendrite and the relation between dendrites and eutectic cells are described. The summary of the results is shown below ;
(1) The fractured surface Parallel to the growth direction of primary dendrite is along the surface of dendrite and is flat. On the other hand, at the transversely fractured surface, primary dendrite breakes at either the graphite or ferrite boundary and the fractured surface is rough.
(2) Dendrite surface is smooth after breaking with just a little pattern because the crack proceeds along the dendrite surface due to the presence of graphite. Breaking through the dendrite cell occurs rarely, but ductile rupture is observed.
(3) Primary dendrite array having a three dimentional skeletal structure contributes to strength as a reinforcing phase.
(4) Eutectic cells are formed within the dendrite array, and therefore this structure may prevent transmitting the stress from one eutectic cell to another.抄録全体を表示PDF形式でダウンロード (1371K) -
塩田 俊雄, 小松 真一郎1973 年 45 巻 11 号 p. 972-978
発行日: 1973/11/25
公開日: 2012/09/21
ジャーナル フリーAs the cooling rate of the metal mold casting of spheroidal graphite cast iron is fast, it has a great merit in that spheroidization of graphite is easy. But it has not been widely employed commercially in industry, because the fast cooling rate restricts the operational conditions of casting and results in various metallurgical difficulties.
The authors employed a statistical method in this experiment. The factors examined are carbon equivalent, silicon content, spheroidizing elements, pouring temperature, pre-heating temperature of mold and stripping time from the metal mold. The author's purpose was to find the main effects and interactions of these factors on many properties such as tensile strength, brinell hardness, elongation, impact value, chilling characteristics and degree of spheroidization of graphite. By estimating the effects of the significant factors within this experiment, the appropriate levels of these factors to produce desirable properties and also their expected values have been elucidated.
The authors have clarified that the main effects and interactions of these factors have a complex influence on the properties of matal mold castings of spheroidal graphite cast iron.抄録全体を表示PDF形式でダウンロード (751K) -
小幡 錬1973 年 45 巻 11 号 p. 979-985
発行日: 1973/11/25
公開日: 2012/09/21
ジャーナル フリーA equation computing exact dimentions of cylindrical risers with consideration of the contact area of riser to casting is derived as follows :
Fct=(π/4)+πK ⁄ ((πK/4)2/3)⋅(Vr/Vc)2/3 ⁄ ((1−β)(Vr/Vc)−β) + (π/(4))1/3(1/(K) Vr/(Vc))2/3⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅(1)
where; Fct=Act/Vc2/3, a shape factor of casting
Act=Total surface area of casting including riser-casting contact area.
Vr, Vc=Volume of riser and casting, respectively
K=height of riser/diameter of riser
β=fraction of solidification shrinkage (0.05 for steel).
The value of K corresponding to the minimum value of Vr/Vc, which gives the most efficient riser, varies as a function of Fct, but the K can be practically regarded as a constant 0.75 for any values of Fct. It is found that Bishop-Pellini's diagram showing the relation between the simplified shape factor (L+W) / T (L, W, and T : length, width and thickness of casting) and the minimum effective riser volume as a fraction of casting volume Vr/Vc can be derived from equation (1). From the results of experiments on cube and T-shaped test castings, it wsa found that the risers determined from equation (1) behaved as the optimam riser.
Nomograms for rapid determination of heights and diameters of the minimum adepuate risers having K=0.75, 1.0 and 1.5 from volume and modulus (Vc/Act) of any given castings are presented, which are derived from an approximate formula against equation (1). These nomograms have sufficiently high accuracy for practical use. In applying the nomograms for a casting consisting of a principal part (the most massive section) and appendages (the thiner sections), the modulus of the casting must be calculated from the volume and surface of the principal part alone, but the casting volume can be calculated from the sum of the volumes of the principal part and the appendage.抄録全体を表示PDF形式でダウンロード (820K) -
生井 亨1973 年 45 巻 11 号 p. 986-994
発行日: 1973/11/25
公開日: 2012/09/21
ジャーナル フリーThe author has studied crazing (craze-crack) formed on the inner mold surface in terms of thermal stress fatigue. The present study was undertaken to investigate the effect of graphite on the crazing phenomenon in flake graphite cast iron. For this purpose, a ductile cast iron was rolled to prepare a cast iron sample with flake graphite arrayed parallel to a certain direction artificially. The relations between the direction of flake graphite and the crazing characteristics were investigated. The results are summarized as follows :
(1) The cast iron with flake grahite made parallel to a certain direction wsa obtained by rolling a ductile cast iron.
(2) The crazing characteristics were dependent on the direction of flake graphite in the sample, that is, the resistance to crazing was better when the derection of the flake graphite was vertical rather than parallel to direction of the thermal stress.
(3) When the resistance to crazing fell remarkably with the change of matrix from ferrite to pearlite.抄録全体を表示PDF形式でダウンロード (943K)
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