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46 巻, 9 号
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研究論文
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野口 徹, 長岡 金吾1974 年 46 巻 9 号 p. 806-812
発行日: 1974/09/25
公開日: 2012/09/20
ジャーナル フリーSome experiments were carried out on the rupture strength of cast iron plate with both deep and sharp notches. The variations in the strength due to differences in root radius, depth of notch and width of plate were examined. The results of the experiment were analyzed by the calculation of the elastic stress distribution at the notch section.
The rupture strength of cast iron decreased with a decrease in the notch radius ρ, until it became almost constant in the region of a sharp notch, ρ<0.5mm. As for the sharp notch (ρ=0.06mm), the relation between the ratio of the notch depth to the half width of the plate and the rupture strength exhibited a concave with a minimum strength of approximately 70% of the tensile strength of an unnotched specimen. There was a slight decrease in strength with an increase in plate width. These results were well explained by the elastic stress concentration factor at the distance of 1.0∼1.5mm from the notch root. Although this does not directly mean that the notch strength of cast iron is determined by the stress value at 1.0∼1.5mm distance points from the root, it does suggest that the stress distribution around the notch root is an important factor affecting the notch strength.
In discussing the macroscopic strength of cast iron, the minimum dimension could not be smaller than the size of a graphite eutectic cell. The value of 1.0∼1.5mm was equivalent to the size of one or a couple of eutectic cells. In a smaller region, the microscopic fracture mechanism must be considered.
The concept of a constant Kc value was not valid in the entire region of notch depth and plate width. The rupture of notched cast iron was not caused by the direct and brittle propagation of the notch itself. The rupture occured after the formation of a plastic region around the notch and was preceded by microscopic failure in a small region below the notch root.抄録全体を表示PDF形式でダウンロード (815K) -
堀江 皓, 川原 業三, 多田 尚1974 年 46 巻 9 号 p. 813-819
発行日: 1974/09/25
公開日: 2012/09/20
ジャーナル フリーIt is very difficult to produce ductile cast iron by magnesium-treatment because magnesium has a low boiling point, high vapour pressure and little solubility in iron and, moreover, the ductile cast iron made by the magnesium addition may revert to flaky graphite cast iron when re-melted. On the other hand, cerium has a higher boiling point, lower vapour pressure and larger solubility in iron. Thus using these characteristics of cerium, it can be expected that high strength cast iron can be produced without resort to graphite-spheroidizing additives but by simply re-melting pig iron treated with cerium.
The raw material, pig iron, was melted in a high frequency induction furnace and treated with mish metal (45%Ce) and was poured into an iron mold. Then this pig iron containing cerium was re-melted in the same furnace and poured into various silica sand molds. The degree of spheroidization, the graphite nodule number and the mechanical properties were determined for these specimens.
A high strength ductile cast iron can be made without resort to graphite-spheroidizing additives but by simple re-melting cerium-treated pig iron. The amount of cerium addition to the pig iron for the production of high strength ductile cast iron depends on the cooling rate of castings and the melting temperature and holding time at re-melting. An excess addition of cerium to pig iron has an adverse effect on the graphite structure and crystallizes eutectic carbide in structure, so that the mechanical properties of cast iron such as tensile strength and elongation deteriorate.抄録全体を表示PDF形式でダウンロード (1049K) -
椙山 正孝, 梅田 高照, 竹内 宏昌, 加藤 寛1974 年 46 巻 9 号 p. 820-826
発行日: 1974/09/25
公開日: 2012/09/20
ジャーナル フリーWith the advances in metal mold casting, it has become very important to evalute the heat flow between the metal and the mold. If the heat flow between the metal and the mold is elucidated, automatic casting with a metal mold may become possible. In the present work, pure copper and AlBC1, BC6 and YBsC3 copper alloys were poured and solidified on the metal plate coated either by alumina (as an insulator) or graphite (as a conductor), and the heat transfer coefficient which is one of the factors that control the heat flow from metal to mold through the dressing was calculated.
The heat transfer coefficient for unsteady solidification is a function of temperature and time. The heat transfer coefficients for the dressingless metal plate vary with the kind of alloy. The heat transfer coefficient is nearly constant for these kind of alloys and dressings when the dressing is thick.抄録全体を表示PDF形式でダウンロード (774K) -
土井 基邦, 西 成基, 上田 俶完1974 年 46 巻 9 号 p. 827-833
発行日: 1974/09/25
公開日: 2012/09/20
ジャーナル フリーUsing a statistical analysis, the solidification of high purity cast iron melted in vacuum was studied mainly for the purpose of explaining how the various factors of melting and cooling influence the freezing manner. The carbon content of the alloys used was varied from 2.24% to 4.48% and the silicon content from 0% to 3.6%. The cooling rates employed were in the range of 10 to 143°C/min at a temperature range of 1,200°C to 1,170°C. The holding temperature and holding time at melting were varied from 1,200°C to 1,500°C and from 0min to 30min, respectively. The quantitative data obtained were analysed using a statistical method by a computer.
All characteristic temperatures during solidification, that is, liquidus (Tp), graphite-austenite eutectic (TGE), cementite-austenite eutectic (TCE) and eutectoid (T0) temperature, are influenced remarkably by either one or more than two of the following factors : the carbon content (%C), the silicon content (%Si) or the cooling rate (VE). These relationships are given by the following formulas :
TP=1,648.2−118.6(%C+0.205%Si) for hypoeutectic
TP=949.34+5.162W−3.489%Si for hypereutectic
where W is weight of specimen.
TGE=1,142.8+5.309%Si−0.1351VE
TCE=1,098.4−9.121%Si+7.129%C
T0=662.26+31.20%Si
The effects of carbon and silicon are a little different from those obtained from the equilibrium diagram, owing to non-equilibrium solidification.抄録全体を表示PDF形式でダウンロード (673K) -
大和田野 利郎, 宮田 秀夫, 久保 義美1974 年 46 巻 9 号 p. 834-839
発行日: 1974/09/25
公開日: 2012/09/20
ジャーナル フリーThe authors have reported previously that the rates of isothermal second stage graphitization in spheroidal graphite and black heart malleable cast irons are controlled by two factors : the graphite nodule number and the growth rate constant of the ferrite layer. In this paper, it is shown how the time for completion of the second stage graphitization can be expressed in terms of the two factors described above, and the changes in two factors caused by the differences of manganese and silicon content in irons are also examined experimentally.
The time for completion of isothermal second stage graphitization, t, is related to the graphite nodule number per unit area, NA, and the growth rate constant of ferrite layer, K, as
K NA t=0.37 for spheroidal graphite iron
K NA t=0.40 for black heart malleable iron
Experiments carried out in spheroidal graphite irons ascertained the validity of the above relation.
The growth rate constant of ferrite layer, K, has its maximum value at about 0.2% manganese when manganese content in iron is variable. And the higher the silicon content, the greater is the value of K. Graphite nodule number, NA, decreases as manganese content in iron increases, and NA increases with the increase in silicon content. Even if the main chemical compositions of irons are the same, the growth rate constant of ferrite layer varies considerably by the different amount of Fe-Si inoculant and sometimes by factors yet undetermined.抄録全体を表示PDF形式でダウンロード (705K) -
片島 三朗, 松浦 正史1974 年 46 巻 9 号 p. 840-845
発行日: 1974/09/25
公開日: 2012/09/20
ジャーナル フリーCondensation constant C2' and C2 which represents the position of moisture condensed layer's front was obtained by the moisture content and rate of the steam transfer. The former C2' was obtained by the following formula :
C2' = [m⁄(m-M)] C1
where C1 : evaporation constant, cm/sec1/2
m : saturated moisture content, %
M : initial moisture content, %
The latter C2 was, as some steam are sent to the moisture condensed specimen, obtained by correcting the above formula by the back pressure of the steam which is passing through the testing apparatus.
C2 = (Pa⁄Px) C2'
where Pa : back pressure at standard specimen, cmAq
Px : back pressure at x% bentonite content, cmAq
This condensation constant was maintained as critical conditon and adding the initial condition, a heat transfer equation for a semi-infinite solid body was solved analytically.
θ=θ0+[100−θ0⁄(erfc(C2/2√k))] erfc(x⁄(2√kt))
θ0 : initial temperature of the mold, °C
k : temperature diffusivity, cm2/sec
To confirm the solution, a pouring test was conducted with pure aluminum and cast iron. As far as the analytical solution was concerned, good approximate values were not obtainned, but it is good to use the result to see the tendencies observed in temperature disribution of the green sand mold.抄録全体を表示PDF形式でダウンロード (721K) -
上田 俶完, 和出 昇1974 年 46 巻 9 号 p. 846-851
発行日: 1974/09/25
公開日: 2012/09/20
ジャーナル フリーThe authors have reported previously of the age hardening phenomenon of an aluminum-containing spheroidal graphite cast iron. In this work, the age hardenings of spheroidal graphite cast irons with aluminum, nickel and copper was investigated. The cast irons prepared were Cu-series with up to 1.5%Cu, Al-Ni series with 1 and 2%Al and 1 to 5%Ni, and Al-Ni-Cu series with 1%Cu, 1 and 2%Al and 1 to 3%Ni. Before aging, the specimens were annealed at 900°C for 1hr., and those containing Cu were cooled slowly to 730°C and held at 730°C for 5hrs and others were cooled to 700°C and held at 700°C for 2hrs., and then quenched into water. The aging treatment was performed at 450, 500, 550 and 600°C. In addition, the age treatment was tried for specimens with other thermal histories such as those that were air-cooled from 900°C and 700°C and as cast. The reversibility of aging was also studied.
The hardness of ferrite matrix is increased by nickel addition and the aging treatment. Aluminum and copper also contribute to age hardening, but copper alone contributes only a little. In the series of Al-Ni and Al-Ni-Cu, age hardening proceeds rapidly to reach a large maximum hardness, but overaging proceeds very slowly. The maximum hardness increase over ΔHv=50 is obtained by Al+Ni≧4% and Al+Ni+Cu≧4%. Age hardening is affected by the matrix structure before aging.
The reversibility of aging was observed and it was assumed that coherent precipitation proceeds in aging. The precipitates in the series of Al-Ni consist of NiAl compounds and develop hair-like precipitates at grain boundary. Copper prevents the development of the hair-like precipitates from grain boundary reaction.抄録全体を表示PDF形式でダウンロード (813K)
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