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52 巻, 9 号
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研究論文
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水野 兼雄, 福迫 達一1980 年 52 巻 9 号 p. 523-529
発行日: 1980/09/25
公開日: 2012/03/28
ジャーナル フリーThe present paper examines the mass effect of different forms of castings with the same modulus values using round, square and triangular bar castings. It became clear that the mechanical strength differed even with the same castings modulus according to the shape of the gray cast iron. The value became lower in order of round, square and triangular bar castings. On the assumption that the cooling rate in castings depends on the ratio of the surface area (s) to the volume (v) of the castings and the mechanical strength of gray cast irons is closely related with the cooling rate [1/(v/s)], the following expression was obtained for the tensile strength. σB=K(1/(v/s)]n, where K and n are experimental constants. A well corresponding equation to the strength of round, square and triangular bar castings was introduced as follows :
For round bar casting, σB=K[1/(v/s)]2.0, where K is 3,000kg/mm in FC 30, 2,600kg/mm in FC 25, 2,000kg/mm in FC 20.
For square bar casting, σB=K[1/(v/s)]2.3, where K is 6,000kg/mm in FC 30, 4,900kg/mm in FC 25, 3,700kg/mm in FC 20.
For triangular bar casting, σB=K[1/(v/s)]2.5, where K is 9,000kg/mm in FC 30, 7,400kg/mm in FC 25, 5,500kg/mm in FC 20.抄録全体を表示PDF形式でダウンロード (732K) -
蓑輪 晋, 太田 英明, 二宮 三男1980 年 52 巻 9 号 p. 530-535
発行日: 1980/08/25
公開日: 2012/03/28
ジャーナル フリーMeasurements were taken of the change of hardness and weight of the frozen mold with time, the inflow of air to the mold at low temperatures and the change of pressure resulting from the condensation of water vapor in air. Further, the relation between water contents in the mold and cooling rate, and the effect of water content and temperature on the strength of the mold were studied. The cooling rate increased as the water content increased in the mold. When the mold sand was immersed directly in liquid nitrogen used as a refrigerant, the nitrogen which penetrated did not vaporize rapidly. The maximum tensile strength of the mold containing 2∼4% water was gained between −50 and −60°C, the value of which were 17kg/cm2∼33kg/cm2. When a dilute solution made of copolymer of isobutylene and maleic acid were added to the mold, the tensile strength increase was more than when only water was added to the mold.抄録全体を表示PDF形式でダウンロード (602K) -
堤 信久, 今村 正人, 佐久間 芳信1980 年 52 巻 9 号 p. 536-541
発行日: 1980/08/25
公開日: 2012/03/28
ジャーナル フリーVariation of graphite form occuring during holding for a long time at high temperature after the treatment for graphite spheroidaization were analyzed using image analyzing computer QTM 720 on factors such as NIK nodularity, shape factor, area and excursion ratio of graphite. A-series molten iron from a basic lined high frequency induction furnace charged with commercial spheroidal iron scrap was treated with Fe-Si-Mg alloy, then poured into CO2 process sand mold at a given time. Besides, K-series specimen were made in the same way as A-series one from the melt treated with CaSi-MgF2 alloy on the molten iron from special Jiroh type are furnace using basic slag covering.
The ratio of spheroidal graphite to total graphite decreases with holding time. In stead of formation of spheroidal graphite, larger quasi flake graphites having more than 1,000μm2 of area are formed, and lump graphites with more branch-out are also formed. Smaller sized graphite having various form however, shows no distinct change in form distribution. Magnesium content decreases clearly at first stage but becomes faint after arround 20min holding. CaSi-MgF2 treated specimen series show much less decrease in magnesium content. Moreover, larger spheroidal graphite having more than 1000μm2 area and showing high shape factor, as much as 0.9, is formed in this specimen. Even in the specimen cast after holding 30min at 1,350°C, a large number of spheroidal graphite having high shape factor mixed large quasi flake graphite is obtained.抄録全体を表示PDF形式でダウンロード (767K) -
倉部 兵次郎, 村松 晃, 牧口 利貞1980 年 52 巻 9 号 p. 542-547
発行日: 1980/09/25
公開日: 2012/03/28
ジャーナル フリーWater-soluble CO2 gas setting mold made from alumina sand and sodium aluminate of few percentages was developed to facilitate the disintegration of the mold by water-spraying after casting. This study was carried out to investigate the influence of water-spraying under A1 transformation temperature on the increase of residual stress in cast iron, and also consider whether or not residual stress influences the fracture toughness of cast iron. The water-spraying treatment under A1 transformation temperature caused a small increase in the residual stress compared to the conventional ones, because of permanent strain occuring due to temperature difference between the rapid cooling and the slow cooling part. A discontinuous water-spraying for avoiding large temperature difference was effective in reducing additional increase in residual stress in cast iron. Residual compressive stress at surface layer induced by rapid cooling of water-spraying somewhat ameliorated the fracture toughness of cast iron. This study indicated the suitability of a water-soluble treatment for reducing the amount of increase in residual stress.抄録全体を表示PDF形式でダウンロード (635K) -
佐藤 健二, 萩野谷 生郎, 玉崎 洋一1980 年 52 巻 9 号 p. 548-552
発行日: 1980/09/25
公開日: 2012/03/28
ジャーナル フリーAl-Si-Mg alloys were melted under a commerical covering flux containing NaCl, KCl, Na2SiF6 and NaF in an open type heavy oil-fired or natural gas-fired furnace. Hydrogen content in the melt was measured by means of initial bubble testing. Hydrogen content in the degassed melt without flux covering rapidly increases. Such rapid hydrogen absorption is prevented by flux covering. Humid atmosphere, prolonged holding and elevated temperature cause increase in hydrogen content in the melt even under flux covering. Use of more amount of flux effectively controls hydrogen absorption. Covering flux can itself dehydrogenate but the ability to do so gradually weakens as holding is prolonged. The flux layer on the melt gradually transforms from liquid to dense solid and subsequently to porous solid as holding is prolonged. This leads to increase of hydrogen content in the melt.抄録全体を表示PDF形式でダウンロード (611K) -
上田 俶完, 滝田 光晴, 石川 克彦, 山本 保1980 年 52 巻 9 号 p. 553-557
発行日: 1980/09/25
公開日: 2012/03/28
ジャーナル フリーHeterogeneous nucleation of graphite in cast iron was studied and discussed following the classical nucleation theory in order to clarify the nucleation mechanism of graphite. Molten iron was treated with molten glass to remove the heterogeneous nuclei. Thereafter, plate or powder of different substances was inserted into the treated molten iron to determine the nucleation ability. The molten iron was solidified in the molten glass to prevent nucleation on the crucible wall. The degree of undercooling determined from the thermal analysis curve was related to the ability of nucleation of inserted substances.
The nucleation ability of the substances was arranged in order of decreasing efficiency as graphite, BN, MnS, Al2O3, CaO, CaC2, CaS, cristobalite and Si3N4. It is clear from nucleation theory that the substance which is effective for nucleation has a little interfacial energy with the nucleated crystal. It is also confirmed that the interfacial energy between two solids is affected by crystallographic matching. The better the crystallographic matching, the larger the nucleation ability. The results agree with the expectation from classical nucleation theory.抄録全体を表示PDF形式でダウンロード (566K)
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