The hardness of the quenched steel depends on the hardening temperature and the cooling velocity. when a steel is heated to high temperature above The critical range and cooled rapidely, the hardness increase with the hardening temperature until the maximum point and decrease gradually. This phenomene is observed more cleearly in the case of Nickel Chrome steels rather than Carbon Steels.
Hardness measurement is taken on 4 Steels of different contents of Nickel and Chrome, quenched from various temperatures between 700°C and 1, 200°C The hardness Curves connected to the quenching temperature and cooling velocity are traced, and the fonctional ralations between chemical composition, hardness, quenching temperature and cooling velocity are described.

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On the Relation between the tensile Strength of carbon Steels and the Steel making. By Benzo, Fukata. Kogakushi; The Specification of forged or rolled carbon steels differs in detail in countries or by authorities and is trouble for steel makers. The present writer studied these relations. Notwithstanding the real strength of the carbon steel is unknown, there are some changes in it, and happens sometimes disagreement between the specification and the maker.
Hence he assumed formulae for the calculation of the tensile strength (the main mechanical property of steel) of an ideal carbon steel, based on the mean strength of the pure iron got by four authorities Neville-Cain, Yensen, Escard and Gaellens.
In the same manner, he assumed the mean increasing value in tensile strength of the pure iron by carbon, manganese or silicon per 0.01% of each. In this way he got the following formulae.
32.0+70.3C+15M=A kg/m.m, m²
20.2+44.6C+9.4M=B t/_??_″
Where C and M denote the percentage of C and Mn in the steel. As the amount of silicon in common carbon steels is not so vary, it will be ableto assume 0.2% and the assumption used in the writer's formulae.
The calculated tensile strength of a carbon steel with the same chemical composition from the formulae given by Campbell, Darby, some works and some preactical data is less than that of the ideal value got from the above formulae, and differs from each other in degree.
This discrepancy must be attributed to some defects of an actual steel, though the actual one has the same chemical composition with the ideal one.
By his Experience in the open hearth steel works, some progress in the manufacturing steels have been made to let the tensile strength of the steel having the same composition with the ideal steel approaches to that of the ideal steel during some ten years past. Therefore the present writer wants to offer these two formulae A and B denote the tensile strength of the forged or rolled ideal carbon steel in the present knowledge. This might be the ideal condition to be attained by any process of steel making. The difference between that ideal value and those of steels indcates the skilfullness of the steel making art.
At any rate in the actual work the steel meeting is first of all, as the making of ingots occupies the greater part of the work.
When an ingot is made, it is limitted to very narrow range to modify some properties of it by heat or mechanical treatment.

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