Influence of Ni on the hardness and impact resistance of Cr-Mo cast steels containing Cr 1%, Mo 0.25% was investigated. The specimens were oil quenched from Ac₃+50°C and subsequently tempered at 180-700°C.
From the results of these studies, the author obtained the following conclusion:- In the case of low carbon content, the hardness of Cr-Mo cast steel rapidly increases as the Ni addition increases, but in higher carbon content, it does not increase hardness any more. At a low tempering temperature the hardness increases with the Ni content, but when the tempering temperature is elevated, the effect of Ni is slightly affected. Though Ni has a marked effect in impact resistance up to 2%, with further increase in Ni addition the impact resistance suddenly decreases. The "first" temper-brittleness occurs at the tempering temperature of 300-400°C. In case, however, the tempering temperature supercedes 500°C, the toughness is sensibly enhanced.
In short, Ni addition gives an excellent results for the low carbon, Cr-Mo steel, but not so for cast steel of every kind.

抄録全体を表示

An eutectoid steel cylinder, on the surface of which hot-junction of thermo-couple was welded, was heated to 780°C and quenched into various kind of. quenching liquid. Then the cooling curves were recorded by the oscillograph to indicate changing of thermo-electromotive force.
The results were as follows, (1) Numerous kinds of substances were added to water but any coolant could not be obtained which had a cooling ability similar to oil excepting waterglass solution. (2) Aqueous solutions of non-volatile substances showed very severe cooling ability and useful for the drastic quenching. (3) Aqueous colloidal solutions were not inflammable and their cooling power could be changed at will according to the concentration, then probably might be used in any particular quenching operation. (4) Concerning oils both mineral and fatty, the heavier or the larger was its molecular weight, the better proved its cooling ability. Fatty oil was more excellent in cooling ability than mineral oil. But even in fatty oil the cooling ability was not excellent if its acid value was high.

抄録全体を表示

Once the author has discussed about the solution and the diffusion of hydrogen in steel and about the cavity's effect on the behaviours of hydrogen in steel. (Tetsu-to-Hagane, vol. 36, 1950, No. 1, 23) Now, as one of applications of these investigations, he tried to estimate the quantity of hydrogen loss at the sampling in the course of hydrogen analysis of molten steel and to investigate the extracting temperature and time of hydrogen.
Then he tried to calculate the time necessary to remove hydrogen from steel by heating. Finally, he treated the problem of hydrogen escape from steel at the ordinary temperature.

抄録全体を表示

In the first and the second reports, it was cleared that oxygen is one of the greatest factors which influence upon grain size and hardenability of iron and steel. (Tetsu-to-Hagane, vol. 36, 1950, 108-113; vol. 37, 1951, 283-290.) However, it was not yet made clear what type of oxygen in iron or steel was so significant.
In the practical steel making process, most of steels are deoxidized by deoxidizers at the finishing period of the process, so steel is used to contain oxides in the form of non-metallic-inclusion. Moreover, even in the steel deoxidized by addition of much amount of deoxidizers, it has been recognized that the difference of oxygen content in the molten steel bath before addition of deoxidizers influences upon mechanical properties of these steels.
Therefore, from the above mentiond viewpoint, in order to know whether these effects were owing to the presence of oxides in steel or not, the auther prepared aluminium steel samples which contain constant amount of carbon and various amount of alumina in a laboratory furnace, and then, by using these samples, investigated their cleanliness, grain-size and hardenability.
Results obtained are as follows.
1) The aluminium steel containing little alumina had greater tendency to have large and uniform grain-size, but when containing much alumina, was apt to form fine grain-size and overheated structure.
2) In the aluminium steel containing little aluminium and much alumina, the abnormal structure was apt to appear, but even if in the steel containing much alumina, when it contained more than 0.4 percent aluminium, the abnormal structure was not observed.
3) The aluminium steel containing much alumina had distinctly lower hardenability, however, even in such steel, when it contained more than 0.5 percent aluminium, they became to have the same hardenability as that containing less alumina.
4) In the aluminium steels containing the same amount of total oxygen, the effect of oxygen present in the form of alumina on their grain-size and hardenability was larger than that of present in the form of ferrous oxide.
From the above mentiond, it was made clear that oxygen present in the form of oxides in steel influences on the properties of steel.
Therefore it is beyond doubt that the practical steel making process have to be performed chiefly to prevent oxidation of molten steel bath, futhermore, also in the case of using deoxidizers, it is presumed that the process must be operated to float and to separate deoxidized resultants in steel.

抄録全体を表示

Following the 11th report (Lecture, Oct. 1943, Iron & Steel Inst. Japan) the author studied on the method of utilization of waste materials of high speed steels; for example, the method of making turning tool tips by using welding electrodes made from turning scraps of high speed steels, and the re-utilization of the smaller size broken pieces of the high speed steels.

抄録全体を表示

Usually Gakushin method is used for rapid analysis for determination of total FeO in acid slag. But it is not fit for a rapid method, because its procedure to fuse sample in a nickel crucible is very inconvenient.
Therefore the authors made a study on the direct dissolution by acid, and this extremely simple procedure was found to give satisfactory results. In order to investigate the accuracy of this improved method, the authors compared it with other various methods. As result of this investigation, it was observed that values obtained by a Mitsubishi method are slightly higher or lower than the standard value according with kinds of slag, though the results of Gakushin and a Muroran method agree each other.
Concerning this matter, the authors again studied on all kinds of acid slag and came to the following conclusion.
(1) Gakushin and Muroran methods give total FeO value, while Mitsubishi method gives active (free) FeO value, (2) so that the total FeO value must always give the lower figures when slag containing Fe^III is determined by the latter. (3) The cause of high value is due to the existence of Cr^II and it was known from results of this study that the percentage of Cr^II in chromium acid slag is about 30% of total Cr.

抄録全体を表示

Ordinarily, the distillation method (JES) is used for analysis of arsenic in iron and steel with very excellent results, but it is not fit for the rapid analysis on account of the long time being required for vaporization, drying and distillation.
Therefore, the authors studied on the rapid and simple method. Outline of the procedure is as follows:-
(1) Sample (2g) is dissolved by mixed acid solution.
(2) The combined carbon and the arsenous As^III) are oxidized by KMnO₄ sol. and the excess KMnO₄ is reduced by H₂O₂ (3%) solution.
(3) This is slowly poured into a boiling NaOH (20%) solution by stirring and cool down.
(4) It is diluted to exactly 200c.c., mixed throughly, and filtrated by the dry filter paper.
Finally, 50c.c. of this filtrate is pipetted off.
(5) 50c.c. of conc. HCl were added to it and cooled down. And then thereto are added 1c.c. of N/50 KBrO₃ solution and 10c.c. of KI (20%) solution to it.
(6) Immediately, the I₂ set free is titrated with N/50 Na₂S₂O₃ solution.

抄録全体を表示

Chemical analytical method (Phosphate gravimetric method or Oxine volumetric method) of Mg in ductile cast iron was planned and experimented by using the Mg standard solution, and compared with spectrographic determinations. Outline of the experiment is as follows:-
(1) Sample is dissolved in HCl+HNO₃, evaporated and baked. After cooling, it is dissolved by HCl, and then silica, graphite, etc., are separated by filtration.
(2) The filtrate is transfered to a separating funnel, and most of the iron is separated by ether treatment.
(3) Extractive acid layer solution is neutralized by Na₂CO₃, and the Fe, Al, etc. remained are precipitated by addition of NaCH₃CO₂. The solution is heated to boil and the precipitates are separated by filtration.
(4) Mn is separated by addition of Br water, and then Ca is separated by the (NH₄)₂O₂O₄ reagent.
(5) Gravimetric method: From the filtrate, Mg is usually determined as the pyrophosphate.
Volumetric method: From the filtrate, (if Cu is present, it is separated by H₂S gas) Mg is precipitated by oxine alcohol solution, then dissolved by HCl, and titrated with the N/25KBrO₃-N/25Na₂S₂O₃ standard solution.

抄録全体を表示