Practical Considerations about the Hydrogen-Boiling in the Low C-Special Steel Manufacturing

Deguchi, K. 대한금속재료학회(대한금속학회) 1974 대한금속·재료학회지 Vol.12 No.2

As mentioned above, "How to obtain the sound ingots" is the first, most important technical problem than any others in high quality special steel manufacturing. And the hydrogen-boiling in the ingot of the low C-special steel melting is one of the most troublesome problems, especially in the humid season. We suffered formerly about this problem for a long time too. So that here I introduced the considerations on our bitter experiences, for reference. I showed at first, many statistics about [H]_Tap which we measured and then the test results in our practical melting operations. Finally I summarize the instructions, how to suppress the increase of [H] and to avoid the hydrogen-boiling in the low C-special steel. (1) About the increase of [H] from the oxidizing period to the reduction stage. In order to keep [H] (in the connection with [O]) in the lower level at the earlier stage of reduction, it is necessary to keep [H]²×[O] value at the end of oxidizing period as smaller as possible, and to keep Δ[H](=k₁[H]²×Δ[C]+k₂) as higher as possible. For these purposes, the most important point is, after all, how to choose the optimum temperature to begin the oxygen-blowing and at the same time its finishing temperature. The effective conditions for decarburization are also effective for dehydrogenation. Especially in this case, we must pay attention to the fact that, in the earlier stage of reduction, [H] is apt to increase to higher amount in low C steels than in medium, high C steels, even when the values of [H]²×[O] at the end of the oxidizing period are same. (2) About the degree of slag-off at the end of oxidizing period: as completely(by another reason) and as rapid as possible. About 1m exposure of bath surface may be sufficient. (3) After slag-off of the oxidizing period, we can say there is no difference in the charging sequence, that is, at first deoxidizing agent, or at first reducing slag. But we can say that [H]_(Tap) in the case when we use 50% Ca CO₃is lower than that of 100% CaO in the humid season. (4) The limes must be perfectly dried. It must be aimed at least H₂O<0.5%. About the ferro-alloys (especially the ferro-Cr) and other charging materials (including the scraps) too. (5) Reducing period must be operated as quick as possible. Basicity of reducing slag must be at least>2.0 and is better to be kept somewhat higher, as nearer to the end of reducing period. Of course, never sudden change of basicity. Slag conditions must be kept in the state of A or B, for the hydrogen problem in the humid season. And for this purpose the important point is the temperature control, that is, keeping the temperature in only gradually progressive drop without specially strong heating in the way from the end of the oxygen-blowing to the tapping. (6) Even though with the full cautions mentioned above, if H_(Tap) increases over the limited value, we can suppress such increasing amount of [H] by the argon-blowing max. 1.5㎥/Ton of steel, and avoid surely the hydrogen-boiling. Many practical data in this report are those which were measured formerly by our "Hydrogen Problem Committee" of Japan Special Steel Co. This time, I could introduce here these data, under permission of Japan Special Steel Co. I thank for that permission. At last for your eager listening, I want to express the thankfulness.

From our first test furnace construction to the recent development of ESR : mainly upon the high alloy special steels

Deguchi, K. 대한금속재료학회(대한금속학회) 1974 대한금속·재료학회지 Vol.12 No.3

I. Introduction ESR(Electro-Slag Remelting) was, as you know well invented in USSR in about 1954 and industrialized. In Japan, at the end of 1961 (according to my memories), one trading company introduced us the license of this ESR process (telling us that this invention was already patented in Sweden, France, D.F.R., England, USA and Canada). In 1963/1964, USSR MACHINO EXPORT recommended to bind the technical license with Japanese companies through the other trading company (In these duration Kobe Steel Co. contacted directly with USSR about ESR). But license fee was too expensive than we expected So that, in Japan Special Steel Co., we decided to design and to establish the ESR furnace by ourselves, and began to construct the test furnace, at first 20㎏, then in succession 100㎏ capacity, utilizing and reconstructing the old one ton capacity electric arc furnace which was installed in casting shop. We had many difficult experiences to make clear the optimum conditions to obtain the good ingots. Our little paper listed in TETSU-TO-HAGANE, Vol. 50 (1964), No. 11, p. 1780 is the first report of the technical operation data which was published upon ESR in Japan. After these bitter practical test researches Japan Special Steel Co. established 1 Ton and then in succession 4 Ton capacity ESR furnaces by our own designs and constructors. In the other side, about the patent of this process, USSR made an application in Nov. 2. 1961, and after the judgement the content of this application was officially notified in Nov. 30. 1966. The protests continued between USSR and us till Nov. 14, 1969, when they withdrew their application in Japan after 8 years in total. In about 10 years from our first test furnace construction, not only in Japan but also almost all over the world, ESR process made much progress and still now is being studied very vigorously, of course the number of furnaces installed by the professional furnace makers increased very much. 2. Classification of ESR The kinds of steels produced by ESR are; (1) The high alloy special steels, for example, tool steels, stainless and heat-resistant super alloy steels. (2) The construction steels. (3) The high tensile strength steels and other special purpose steels. The ingots produced by ESR are; (a) Relatively smaller round or square ingots which are to be forged or rolled (generally <1-5Ton). (b) Relatively larger round or rectangular ingots for the large forgings by press-forge(generally <15-25 Ton or more). (c) The giant slab ingots for the extra large forgings or for the extra heavy ultra-thick plates, for example, to be used for the reactor vessels (generally <150 Ton or more). And ordinarily (a) is applied for (1), but (b) and (c) for (2) or (3), particularly (c) is a new trend of ESR and now adapted or being investigated by the large steel makers, for example, USSR (Dnieprospetzstahl), Rheinstahl (Heraeus), Bo¨hler, Consarc Corp., Nippon Steel Corp., Kobe Steel Co., etc. Of course, to produce these large ingots, the multiple-bifilated electrodes are used. But I want here to talk mainly about(1)-(a)-monofilar system. 3. Characteristics of ESR. ESR is often compared with VAR (Vacuum Arc Remelting). The same points are: (1) The molten baths are protected from the contamination of the atmosphere, that is, in VAR, by the vacuum and in ESR, by the molten flux. (2) The molten baths coagulate layer by layer from the bottom in the water cooled Cu-moulds. The inner structures of the ingots due to this process improve the material qualities. Next the characteristic points of ESR different from VAR are; (1) The heat-source is the electrical resistance heat of the molten flux. So that we can control the electric power of melting continuously to zero. This perfects the hottop effect to remove the shrinkage cavities. (2) Almost complete metal-slag reactions at their boundary surfaces when the droplets of molten steels drop through the molten fluxes. In the consequence, the dissolved or mingled oxides, sulphides (and nitrides) transfer into the fluxes. of course, the kinds of fluxes have the important influences and the melting rate affects too. The non-metallic inclusions in the molten pool float up and are eliminated to the flux and in this case, the depth of the pool affects too. These refining reactions are the most characteristics of ESR. (3) More shallow pools of the molten baths of ESR than those of VAR. So that their solidification structures become finer and, owing to this point, ESR suits to produce the tool steels, for example, high speed tool steels etc. (4) The furnaces of the solidified ingots are covered with thin films of the flux. These smooth surfaces benefit the surface conditioning of the ingots. (5) Rather simple constructions of ESR furnace in comparison with those of VAR. This decreases the melting cost and the depreciation. (6) After all, the increases of yieldings owing to the quality improvement and to the minimizing the top cutting, and the decrease of the conditioning cost owing to the smooth surfaces of ingots these two points produce the more merits than compensating the remelting costs, in the high alloy special steels. 4. The problems Now, to obtain the merits mentioned above, it is necessary to master the optimum operation conditions. For example, those factors are; melting speed applied voltage, power consumption, AC or DC kind and amount of the flux fill ratio ie electrode mould diameter ratio surface condition and segregation of the compositions of the electrode size of mould starting method ie cold or hot start pool depth and its shape etc. These affect each other. Furthermore, we must consider the counter-measures for the hydrogen problem, the oxidation of the flux and the change of its compositions, the fame from the molten flux the damage of the stool due to the are between the igniter and the stool etc. Concerning to the problems of ESR, the most important points are the technical operation practices. I want to introduce these problems according to the many publisher data, mixing my little experiences.

Practical Considerations about the Hydrogen Boiling in the Low C-Special Steel Manufacturing

Deguchi, K 대한금속재료학회(대한금속학회) 1974 대한금속·재료학회지 Vol.12 No.1

It is well know that, in the manufacturing of the low C-special steels as the case-hardening steels and the stainless steels, the ingots are apt to be not killed by the hydrogen boiling, especially in the humid seasons. I saw these problems last year in a plant in this country. We suffered formerly, too, about these troublesome hydrogen problems for a long time before vacuum remelting and vacuum degaussing installations. Here I want to introduce the considerations on our bitter experiences to help your practical operations. 1) P_(H₂O)(㎜Hg)=Mean value of the partial pressures of the moisture in the atmosphere in each month measured every day through a year. [H]_(Tap) (cc/100g Fe)=Mean value of the hydrogen contents at the tapping of the low alloy special steels melted by the basic electric are furnaces (B.E.F.) (10-15 ton) in each month. There can be seen relatively higher degree correlations between [H]_(Tap) and P_(H₂O) (n≒380), when we calculate the regression equation, assuming that both keep the linear relation. Of course, the histograms of [H]_(Tap) differ according to the kinds of steels, the melting furnaces and the terms of sampling. 2) Generally [H]_(MD) (at the melt-down) decreases a little by O₂-blowing, then increases very much suddenly at the reducing period and increases a little again at the tapping (n≒135). These amounts of increase of [H] at the reducing period and at the tapping are larger as when P_(H₂O) is higher. However when we check, for example, about the casehardening steels melted only in Jan. -Mar. (n= 120), there seems almost no correlation between [H]_(Tap) and P_(H₂O) when P_(H₂O) is under than about l0㎜Hg. Therefore, to decrease [H]_(Tap), we must investigate the counter-measures in both cases, that is to say, the manuals to decrease [H] in the ordinary melting processes and the special instructions in the humid seasons. The limits of [H]_(Tap) to avoid the hydrogen boiling are about 9-l0cc/100g in the ordinary case-hardening steels and about 12-14cc/100g in the stainless steels. 3) [H]_(MD) is driven out by the agitation of O₂-blowing and by the floating actions of the produced CO bubbles. Although Δ[H] is much smaller than those theoretically calculated from the decarburized amounts, it is sure that the effective conditions of O₂-blowing for decarburization are also effective for dehydrogenation. The ratio of [H]²× [O] at the end of oxidizing period to [H]²×[O] at the earlier period of reduction is kept about 1:1 for the low C-special steels and about 1:0.5 for the medium and high C steels. So that it suppresses the increase of [H] at the earlier period of reduction to decrease not only [H] but also [O] at the end of oxidizing period. 4) About the influences of the amounts of oxidizing slags which are brought into the reducing period, of the exposed area of the bath open to the atmosphere and the exposing time, or of the charging sequences of reducing slag-forming materials, it was difficult to obtain the distinct conclusion in our many practical operations. Next it is unsufficient to emphasize, only abstractively, the effects of the moisture contained in the charging materials, especially in humid seasons, so that I want to warn their importance, showing the test results of the practical operations. Of course, the most important points of ordinary melting processes, that is to say, how to control the temperatures and the basicities in the reducing period, are also very important for dehydrogenation. 5) If [H] increases over the limited value and the bath can not be killed in the humid seasons, even when the sufficients cautions are taken in the melting stages, the forced dehydrogenation methods are introduced, for example, using the dehydrogenation agent Freon 12 (C-CL₂-F₂) or the argon-blowing. Originally hydrogen is driven out only by the mechanical methods, but, in this case, the dehydrogenation is achieved chemically by formation of the hydrogen-halides. In our test operations, the effect of dehydrogenation was remarkable by blowing only a little amount of Freon 12, but it is necessaryly to consider specially the gas masks and the ventilation. About the argon-blowing, according to many results of stainless steels, relatively smaller amounts of [H] can be only removed than theoretical possibility, but the maximum amount was about 4.5cc/100g, and the dehydrogenations by this method are more effective as the contents of [H] are higher. Finally I want to summarize these instructions how to prevent the hydrogen boiling.

From our first test furnace construction to the recent developement of Electro-Slag Remelting Process : mainly about the high alloy special steels

Deguchi, K. 대한금속재료학회(대한금속학회) 1974 대한금속·재료학회지 Vol.12 No.4

About the manufacturing process and the characteristics (mainly the toughness) of the tool steel

Deguchi, K. 대한금속재료학회(대한금속학회) 1975 대한금속·재료학회지 Vol.13 No.3

Effect of Compost Application on Soil Temperature in Bare Andisol

Shin Deguchi,Hidenori Kawamoto,Osamu Tanaka,Akihide Fushimi,Sunao Uozumi 한국초지조사료학회 2009 한국초지조사료학회 학술대회논문집 Vol.2009 No.08

Soil temperature is an important factor influencing crop growth. Within limits, a higher soil temperature will promote crop growth, especially in cool climate regions. Compost application can increase soil temperature, however the mechanism of increasing soil temperature remains unclear. We conducted a pot experiment to examine the effects of compost application on soil temperature and evaporation in a bare Andisol. Pots with compost (16㎏ m?²) had a higher soil temperature and less evaporation than pots without compost. The decrease in evaporation and the increase in soil temperature by compost application were significantly correlated. We conclude that compost application increases soil temperature by decreasing evaporation from the soil surface.

Memory Search by Matching Features in Chaotic Neural Network

Toshinori Deguchi,Naohiro Ishii 대한전자공학회 1994 ICONIP : International Conference On Neural Inform Vol.3 No.2

Effect of Winter green Manure on the Phosphorus Nutrition and Yield of Succeeding Corn Crops in Northeast Japan

S. Deguchi,S. Uozumi,E. Touno,H. Uchino 한국초지조사료학회 2016 한국초지조사료학회 학술대회논문집 Vol.2016 No.08

New Circuit Topology of Single-Ended Soft-Switching PWM High Frequency Inverter and Its Performance Evaluations

Y.Deguchi,S. Moisseev,M.Nakaoka,I.Hirota,H.Yamashita,H.Omori,H.Terai 전력전자학회 2001 ICPE(ISPE)논문집 Vol.2001 No.10

This paper presents a simple and cost effective circuit topology of single-ended type high frequency quasi-resonant PWM inverter using IGBTs, which can operate under wide soft switching operation range based on ZCS for main power switch as compared with a conventional active voltage-clamped ZVS-PWM high frequency quasi-resonant inverter developed previously In principle, this new circuit topology can efficiently operate under a constant frequency PWM control-based power regulation scheme In particular, it is noted that the zero current soft switching (ZCS) commutation can achieve for the main active power switch On the other hand, the zero voltage soft switching (ZVS) commutation can also achieve for the auxiliary active power switch The operating principle of this high-frequency Inverter treated here and its power regulation characteristics are illustrated on the basis of the simulation and feasible experimental results.

Anti Pandemic Simulation by SOARS

Hiroshi Deguchi,Yasuhiro Kanatani,Toshiyuki Kaneda,Yusuke Koyama,Manabu Ichikawa,Hideki Tanuma 제어로봇시스템학회 2006 제어로봇시스템학회 국제학술대회 논문집 Vol.2006 No.10