In order to reduce the cost price of iron and steel, it is necessary to utilize fully natural resources in Japan and South-East Asia. First of all it must be prepared for the future to use the natural resources of iron, which contain sulphur in ever-increasing proportion. A special bessemerizing process was devised to blow air or oxygen directly into the hearth of the blast furnace.
As regards this method a joint research of Tokyo University and Yawata Iron & Steel Co. Ltd., was executed in 1951-52, using a 3ton test blast furnace of the Technical Institute of this Company.
Through these experiments the slant tuyer for bessemerizing was invented, and the heat-proof blowing pipe of high durability was born, thus a safe and practical method was found which we were able to use in this process. During these two years the following results were confirmed:
(1) Through a simple operation, i.e. by only one bessemerizing (5-10 minutes) between tap to tap, a pig-iron of high temperature, containing low Si, S and high Mn, could be obtained even if the burden contained high sulphur.
(2) In combination with the deeper hearth the tap interval could be prolonged considerably (from 2-3 hours to 6-8 hours).
(3) A good condition of the furnace that is "cold top and hot bottom" could be maintained. The top-gas temperature was lowered and the hearth was kept hot.
(4) Liquid pig and slag in the hearth could be extracted as samples for analysis at will, which made it possible to find the metal components before tapping.
(5) By special designed jet-feeder it became possible to blow lime, ferro-silicon and other additional refining materials directly into the bath through the slant tuyer.
(6) The components of the slag and metal in the bath could be controlled at will by using (4) and (5).
(7) Through this special bessemerizing and the invention of a method to lower the metal bath temperature by blowing water and inert gases directly into the bearth, it became possible for the smelter to keep the bath temperature at the most desirable condition to detect impurities. in refining, and to discharge at the constant tap temperature.
In short, the special process of bessemerizing the bath in the blast furnace has made it possible to change the hearth which has been a dead space into an active one, and to make the most of bad natural resources containing high sulphur and other impurities. Still more, as a future prospect, it has made a step forward to the ideal blast furnace of "constant component, constant tapping temperature, and one to three taps a day".

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With eight varieties of samples taken from the hot-rolled high carbon steel strips containing 0.47-1.38% carbon, the effect of annealing temperature and the holding time on their hardness and structure was studied.
1) There was found a distinct relationship between the hardness and the structure, and when the structure was spheroidized the hardness value became minimum.
2) In hyper-eutectoid steels, the temperature to develop the minimum hardness was higher as the carbon content increased. And the minimum hardness value obtained was almost invariable being independent from the holding time.
3) In eutectoid and hypo-eutectoid steels, the temperature to develop the minimum hardness was lower as the holding time increased and the minimum hardness value obtained became low as the holding time increased.
4) The temperature to develop the minimum hardness value in each holding time was enhanced as the carbon content increased.

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In order to obtain the fundamental concept of the "press-tempering (or heat-setting)" method which was applied to correct the distortion of steels due to hardening, the plastic deformation of steels by heating under loads and the mechanical properties of these steels as affected by such deformation were studied.
As the specimens, the steels which contained 0.6% carbon and had been variously heat-treated were used.
The results were as follows:
1. The hardened steel showed an abnormally large plastic deformability during its tempering. The higher the temperature, the larger was the deformability.
2. In the hardened-tempered steel, such deformability appearred during heating at the temperature which wag bigher than that at which it had been tempered.
3. The annealed steel had no such abnormal deformability.
4. The magnitude of such abnormal defomation was proportional to the applied load and had a closer relation with the hardness variation during the process than with the hardness itself.
5. The influences of such deformation on the progress of transformation were found in the mechanical properties of steels after these treatments.
6. As the cause of such abnormal deformability, the appearance of so-called "position-change plasticity" accompanying the precipitation of the cementite during the tempering was presumed.

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Previously, one of the authors studied on the effects of each elements on the low tungsten-molybden-vanadium high speed steel (Sadao Koshiba, Jnl. Japan Inst. of Metals, 16, 1652, No. 9, 511)
In this experiment, the authors studied the changes in their hardness and microstructures bronght about by the heat treatments with the varions kinds of the moderately low tungsten-molybden-vanadium high speed steel containing C 0.7-1.4%, Cr 3.5-4.5%, W 4.0-8.0%, Mo 2.0-4.0%, V 1.5-3.5% from previons results, and also tested their durability by putting them in actual service, and then made a comparison with the low-tungsten high speed steel and molybdenum high speed steel.
From thess experiments, the moderate compositions of low-W-Mo-V high speed steel were ascertained as follows: - C 0.8-1.0%, Cr 4.0-4.5%, W 4.0-5.0%, Mo 3.0-4.0%, V 2.0-2.5%, and C 1.0-1.2%, Cr 4.0-4.5%, W 5.0-6.0%, Mo 2.5-3.5%, V 2.5-3.0%.

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Since the termination of the war a remarkable progress had been made in the methods of chemical analysis. Especially partial adoption of a physical process in place of a wet process could be regarded as one of the development. In the wet process personal elements enters so largely that accurate results are difficult to obtain. Rapid methods in conformity with the factory operation were under the control of time. According to the statistics, variation was usually big and the biased values frequently appeared. It is a matter of common knowledge that the cause of personal error lies in unskillfullness of workers. Nowadays, various methods concerning the error control have been given in academic journals.
1. Preparation of standard samples, then leaving the workers engaging in analysis uninformed the mixing of them among samples.
2. In practising this research, the sources of variation were designed so as to make as uniformly as possible, and the order of analysis was randomized.
3. Comments were given on the comparative results of analytical value determined by workers with the standard value and its rejection limits.

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In order to decide the most suitable method to take the samples of cast iron used for chemical analysis, we prepared six square bars which were cast in sand mould of various sizes (10×10×100-100×100×100mm).
Each bars were cut from the center and twelve analytical samples taken from the outer and inner layers of them by drilling. Investigation was made on the influence of the particle size and of the rate of cooling on chemical composition of cast iron. We further made a metallurgical consideration from the relation between microscopic structure and mechanical properties.
The results were:
(1) The difference of chemical composition between the bars with the largest cross section and the bars with the smallest cross section is remakable. Namely, it is obvious that the chemical composition of cast iron is much effected in the structure of it. In other words, the rate of solidification as well as the rate of cooling after solidification play on important part in the change of structure.
(2) Therefore, the white cast iron on which the change in the structure is very small indicates the standard value of chemical analysis.
(3) In the gray cast iron, results of chemical analysis are much effected by the sampling method. However in any way, the coarse particles nearly indicate average value for chemical analysis, and the fine particles indicate marked defference.
From the results of above experiments, it was found that the analytical results of each compositions of cast iron is much influenced by the particle sizes of shavings as well as the structure of specimens, and the coarser particle size than the particle size of 20 mesh indicates the standard values of chemical analysis. Further as a result of the comparative studies on the various methods of sampling of cast iron, it was confirmed that the most simple method of would be to analyse the coarse particles which were obtained by drilling with a 1-in. dia large-angle-edge (about 150°) drill at about 80r.p.m.

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An inducton heating circuit is fundamentally a transformer wherein the inductor carrying the alternating currents is a primary and the substence to be heated is made the secondary. And the total power (P) absorbed in the work which is a cylynder in this case is: where H₀ represents the magnetic intensity of the solenoid. The conductivity of the cylinder is σ mhos per centimeter cube; a represents the radius of the cylinder; μ_r permeability; & f, applied frequency.
And as the power absorbed in the cylinder to the power lost is proportional to F, it is understood that the importance of using high frequency to an effective coupling and a critical frequency for the effective coupling is: There are three sources of high frequency current which find a commercial acceptance for induction heating.
a) A rotating equipment (motor-generator) of frequency from 1000 to 10, 000 is used at capacities up to 10, 000 kilowatts.
b) Oscillators of spark-gap type, provide frequecey in the order of 100, 000 to 400, 000 cycles. In Japan this type is conveniently used known as a Torikai's apparatus.
c) Frequencies of several hundred thousand cycles are developed by vacuum-tube oscillators with the capacities up to 150 kilowatt input. In Japan there is a tendency to use this type instead of spark-gap oscillator types.
Noteworthy applications of the induction heating are as follows.
a) Surface hardening. This heating is used for suface hardening for its advantages in technical & economical merit. But to enjoy this merit, design of the work coil (a secondary circuit to heat the substance) is very important and therefore the patents of the coils are too numourous to be mentioned. The majority of machine assembly depend to a large extent on induction hardening, especially large gears of tracks (transmission gear of 10t track & D-8 tractor) are subjected to complete machining, including shaving, in the soft-annealed state. Then they are induction-hardened without distortion, very improved wearing qualities being obtained.
b) Heating for Forging and Forming. Many advantages inherent in the use of induction heating for forging operations are responsible for the wide acceptance and use of this way of heating. Induction units which heat slabs for upsetting machines are provided with automatic fixtures, where the passage of the parts thorough the inductor is controlled by a plunger mechanism. A magazine feed runs from the timer or mechanically is tied with the operating lever of the press. The entire operation requires only one operator. But in Japan, this process is still in its infancy,
c) Brazing and Soldering. Also many advantages are obtained in brazing and soldering by using an induction heating too. This process is utilized extensively in the automotive, and farm machinery, soldering of cans, high speed tools or carbide tips fixed to mild steel tools etc., and will be developed to infinitely.
d) Annealing and Normalizing.
e) Welding. f) Cutting. g) Sintering. h) Melting.

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