An analytical procedure was developed for reduction in fluidized beds with batch-wise iron ore feed based on the bubble assemblage model and the three-interface reaction model with solid-state diffusion. The experimental results of hydrogen reduction in the high pressure fluidized bed were analyzed according to the proposed procedure. The simulated results were able to describe the experimental data up to the final stage in which the reduction rate became extremely low. Effects of pressure, temperature, gas velocity, bed height, and fractional reduction on the reduction rate and the utilization factor for hydrogen were elucidated quantitatively by the proposed analytical procedure.

抄録全体を表示

For ignition furnaces of sintering plants, the combustion equipment free from troubles which are caused by coal ash melting has been developed for pulverized coal firing. The developed burner has a high combustion efficiency of fuel with a short stable flame, that is, when coal combustion rate is 30 kg/h and injecting coke oven gas is equivalent to 10% of total heat input of fuel, the flame length is 0.8 m. The developed distributor for pulverized coal has been proved to give a small distribution error of less than ±4%.
These burners and distributor were attached to an ignition furnace in the Sintering Plant. In comparison with the conventional coke oven gas firing (25 burners), heat input was increased by the change of heat distribution but ignition fuel cost was decreased 40%. Good quality of sintered ore was also achieved.

抄録全体を表示

A new spectrophotometric method for determination of elemental sulfur in blast furnace slag has been developed. The outline of the procedure is as follows. A slag sample is powdered with n-hexane using a disk mill and elemental sulfur in the sample is extracted into n-hexane at the same time. The ultraviolet absorption of the n-hexane layer is measured at 275 nm to determine the quantity of elemental sulfur.
By using this method elemental sulfur can be determined with high accuracy, provided the amount is higher than 0.002%. The coefficient of variations at the 0.05 and 0.2% levels of elemental sulfur are 2.3 and 1.4%, respectively. The time required for analysis of one sample is less than 10 min. There is no interference effect for sulfur compounds in the slag sample such as sulfate, thiosulfate, sulfite, sulfide and poly-sulfides.
When a slag sample is powdered under the dry condition before the n-hexane extraction, lower analytical values are obtained, because elemental sulfur changes into poly-sulfides by the reaction with Ca components of the slag sample. This chemical change is found to be suppressed by simultaneous performance of powdering and extraction. Based on this technique, an analytical method is proposed and successfully applied to determine elemental sulfur in a slag sample.

抄録全体を表示

In order to find the effect of phosphorus vapor on the gasification of graphite and coke in carbon dioxide, the gasification rates of electrode graphite and metallurgical coke in CO₂-CO-Ar gas mixture were measured in the temperature range of 900-1 000°C at atmospheric pressure. The rate of gasification decreased with increasing the partial pressure of phosphorus. Phosphorus was found to have strong retardation effect.
The experimental result were interpreted by use of Langmuir-Hinshelwood type reaction mechanism (R=k₁P_CO22/1+k₁/k₂R_CO22+k₃P_CO+k₄P_p) and the rate constants k₁, k₂ and the adsorption coefficients K₃, K₄ were obtained as follows.
For electrode graphite ; k₁=exp (17.78-65 851.2/RT) (mol/min · atm· g-c), k₂=exp (9.585-24 578/RT) (mol/min · g-c), k₃ = exp (-13.74 + 38, 108.3/RT) (atm^-1), and K₄=exp (-8.53 + 43 235.6/RT) (atm^-1), and for metallurgical coke ; k₁=exp (20.49-68 350/RT) (mol/min · atm · g-c), k₂=exp (5.478-14 405/ RT) (mol/min · g-c), K₃ =esp (-8.30 +23 330/RT) (atm^-1), and K₄=exp (-3.92 +31 704.7/RT) (atm^-1).
Activation energies for k₁, with electrode graphite and metallurgical coke are obtained 65.85kcal/mol and 68.35kcal/mol respectively.

抄録全体を表示

An accurate estimation of the resistance to hot deformation is one of the most important factors for the gauge accuracy of hot strip sheets. Application of an equation determined by data of single pass deformation to the calculation of the resistance to deformation for high speed continuous hot rolling often causes a considerable error. The main reason for the error lies in the metallurgical phenomena during a multiple deformation process, which are different from those of a single deformation. In this investigation, a new calculation model has been developed which takes the influence of the metallurgical phenomena like recovery and recrystallization on the resistance to hot deformation into consideration. It has been shown that the dislocation density is a suitable quantity which describes the influence of the metallurgical changes on the resistance to hot deformation quantitatively.
The model has been applied to a high speed continuous hot strip mill and a remarkable improvement in the estimation of the resistance to deformation has been achieved.

抄録全体を表示

A new electrogalvanizing line started its operation in January, 1982 at Chiba Works, Kawasaki Steel Corporation, which has several excellent characteristics on operation and products such as below mentioned.
(1) Plating voltage of CAROSEL method with chloride bath is so low as under 10 V for the current density 150 A/dm².
(2) Uncoated surface of one-side electrogalvanized product, which is perfectly free from Zn throw-around, has good phosphatability and paintability similar to those of cold rolled product.
(3) Newly designed counter flow system increases limited current density of Zn plating up to 200 A/dm².
(4) Zinc phosphate product has excellent whiteness and good paintability owing to appropriate control of Ni content in the phosphate film.
(5) Hydrogen quantitative feeding method has been developed for smaller deviation of Cr coating weight and color tone of chromate product. Resin coating on chromate product improves corrosion resistance and antifingerprint property.

抄録全体を表示

The direct quenching method, as a process of effectively using the heat after rolling is recently gaining interest not only because it saves energy but also because it increases the hardenability of steel. The mechanism of increasing the hardenability of steel, an outline of the manufacturing method of high strength steel plate by roller quenching equipment installed on-line in the plate mill and the characteristic properties of 60 kgf/mm² and 80 kgf/mm² high strength steel plates obtained by the direct quenching method are described.

抄録全体を表示

One housing 200 MW class steam turbine requires a rotor with both high temperature creep rupture strength and low temperature toughness.
A new rotor forging has been investigated in terms of the effects of additional elements (Nb and Ni) and heat treatments on 1Cr-1Mo-0.25V steel creep rupture strength and toughness. The additional elements and differential heat treatment (DHT) showed synergistic improvement in these mechanical properties. Thus, the 1Cr-1Mo-0.25V-Nb-Ni steel can be employed after DHT as rotor material for the one housing 200 MW class steam turbine.

抄録全体を表示

高温・高圧圧力容器材料として使用される各種のCr-Mo鋼HAZ粗粒化部のクリープ破断性質を評価し, 使用条件に即した適切な材料選定を行う上での基礎データを得た.本研究により得られた知見をまとめれば以下のとおりである.
(1) 1から5%のCr含有量を有するCr-Mo鋼HAZのクリープ破断延性はCr含有量により支配されており, 500℃を超えるクリープ温度域で使用する圧力容器は2 1/4Cr-1Mo鋼などCr含有量の高い材料により製作することが必要であろう.
(2) HAZのクリープ破断延性の低下はクリープ破壊時に切り欠き弱化の原因となり, 応力集中の存在する溶接継手部でのクリープき裂発生を容易にしている.
(3) PWHT温度の上昇は破断延性を改善する要因の1つであるが, 1Cr-0.5Mo, 11/4Cr-0.5Mo鋼HAZ部でその効果は小さく有効な対策とはならない.
(4) Cr含有量の増加にともなうHAZ部クリープ破断延性の向上は
・焼入性向上作用によるHAZ部の低温変態生成組織化
・変態温度の低温移行による粒界炭化物の微細化
・Mo₂C炭化物の析出密度の減少による粒内クリープ変形抵抗の低減
などCr自身の作用に起因しているものと考えられる.

抄録全体を表示

The α→γ transformation behavior and its correlation with mechanical properties were systematically investigated in two types of transformation-strengthened steel under a range of very low carbon content from 0.005% to 0.05%. Those are C-high Mn-Nb-B bainite steels and C-high Mn-Mo-Nb acicular ferrite steels. The effects of C content and controlled rolling on the microstructures and mechanical properties were studied, by focusing on the difference between these two steels. The microstructure of bainite steels was recognized as type I upper bainite which was characterized by lath structure of 0.5-1μm width with a retention of austenite grain boundaries in pan-cake shape. Acicular ferrite steels showed a mixed microstructure consisting of polygonal ferrite and upper bainite.
Transformation behavior and mechanical properties in bainite steels did not change markedly with both C content and the degree of controlled rolling, while they changed remarkably in acicular ferrite steels with those variables. Metallurgical factors controlling the strength and toughness in both steels were discussed in detail.

抄録全体を表示

It is known that the toughness of 13Cr-3.8Ni cast steel decreases when the steel is tempered at around 550°C and cooled at slow rate. Effects of tempering temperature, holding time and repetition of tempering on toughness deterioration of the steel are investigated by means of metallurgical observation and mechanical test. It is found that toughness decreases with increase of yield strength which accompanies the increase of corrosion loss in 6.0% HNO₃ solution. Fracture appearance transition temperature and yield strength tend to decrease with the increase of the degree of tempering, while the amount of austenite increases. Toughness is recovered when the steel is tempered at higher temperatures such as 630°C. From these results it is considered that the deterioration of toughness during tempering is ascribed to the rejection of carbon from reverted austenite during slow cooling and the formation of carbide.

抄録全体を表示

New steels HT60 whose goal is weight reduction, rationalization of fabrication and construction of power transmission tower are developed. In hot dip galvanizing process, weld heat affected zone cracking occurs occasionally due to liquid zinc embrittlement of steel. The larger the scale of fabricated sub-assembly for hot dip galvanizing, the larger is the thermal stress arised during the process. Improvement of susceptibility to liquid zinc embrittlement becomes, then, more important in development of new steels to be employed for larger scale tower.
This report describes 1) an estimation of weight reduction of tower by employing HT60 steels, 2) establishing test methods for assessment of liquid zinc embrittlement of steel, 3) effect of alloying elements on liquid zinc embrittlement of steel, and 4) properties of steel pipes, plate and flange developed based on the results of studies above mentioned.
New steels HT60 have satisfactory mechanical properties and weldability together with low susceptibility to liquid zinc embrittlement, and are favorable for the large scale power transmission tower application.

抄録全体を表示

Wear properties of high-chromium and adamite roll materials have been investigated by using roll wear machine designed to simulate the working conditions of a roll at high temperatures. It has been shown that high-chromium roll materials have better wear resistance than adamite roll materials. The use of the highchromium rolls for work roll in the primary stand of hot strip mill finishing train decreased roll cost without deteriorating surface of hot strip.

抄録全体を表示

Despite of ferrite pearlite structure, microalloyed and controlled rolled bar revealed good fatigue property almost equivalent to quenched and tempered plain carbon steels whose microstructure was tempered martensite. Detailed study was carried out to give a comprehensive interpretation for this phenomenon. The relation between static strengthening mechanisms and fatigue property was investigated quantitatively, using low and medium carbon steels conventionally or controlled rolled with variation of Si and Mn contents and V or Nb additions. As a result of this, it was clarified that each strengthening mechanism showed different contribution in improving fatigue limit. Compared with grain refinement, pearlite and dislocation strengthening, both solid solution and precipitation strengthening improved fatigue limit efficiently as well as dispersion strengthening. This was caused by their effectiveness both in preventing dislocation from migration under cyclic loading and in strengthening ferrite matrix comparatively uniformly.

抄録全体を表示

This investigation deals with the mechanism on the formation of white line in welded joints of ERW steel pipes. In order to demonstrate the formation mechanism, the difference in carbon contents between weld line and extruded melting bead in simulated resistance welded joints was investigated in detail, using hypoeutectics, eutectics and hypereutectics in Fe-C alloys.
In hypoeutectics, the carbon content in weld line is lower than that in base metal, while the carbon content in extruded melting bead is higher. On the other hand, the carbon content in weld line is higher than that in base metal and the carbon content in extruded melting bead is lower in hypereutectics. No difference in carbon content occurs between weld line and extruded melting bead in eutectics.
It can be deduced from these results that two phase region where solid and liquid phase coexist exists in weld line, and the liquid phase coexisting with solid phase is extruded outward and the solid phase remains in the weld line at upsetting. Thus, it can be concluded that the difference in the content of alloying elements between solid phase and liquid phase leads to the formation of white line in resistance welded joints such as ERW steel pipes.

抄録全体を表示