The equilibrium of oxygen in liquid iron with H2-H2O mixtures has been studied at 1550°C, 1607°C and 1663°C respectively. Effects of nickel, cobalt, tungsten, molybdenum, chromium and tin on the activity of oxygen in liquid iron have been studied at 1600°C. The data obtained are summarized as follows: 1. H2+O=H2O log K1[=PH2O/PH2·a0]=7, 480/T-3.421 ΔF01=-34, 220+15.65T 2. The interaction parameter of oxygen in liquid iron, e′0: e′0[=∂log f′0/∂[%O]]=-10, 130/T+4.94 3. The effects of alloying elements on the activity coefficient of oxygen in liquid iron: e(Ni)0=∂log f(Ni)0/∂[%Ni]=+0.0053 Ni<40% e(Co)0=∂log f(Co)0/∂[%Co]=+0.0080 Co<40% e(W)0=∂log f(W)0/∂[%W]=+0.0117 W<20% e(Mo)0=∂log f(Mo)0/∂[%Mo]=+0.0117 Mo<10% e(Cr)0=∂log f(Cr)0/∂[%Cr]=+0.0117 Cr<12% e(Sn)0=∂log f(Sn)0/∂[%Sn]=+0.0117 Sn<14%
The mechanisms of deoxidation utilizing the potential difference of oxygen between metal and acidic or basic slag and of other accompanying reactions were intended to be solved. At first oxygen, manganese and silicon transfer rates between iron bath and MnO-FeO-SiO2 ternary slag saturated with silica were measured. Then the reactions between such slags and iron bath which previously contained manganese and silicon to confirm the existence of quasi-equilibrium states were investigated. The obtained results were discussed with the unsteady diffusion equations and rate determining steps were worked out by experimental results and calculations. The conclusions are as follows: 1) The deoxidation rate would be mainly controlled by the transfer rate of oxygen from iron bulk to the interface but the resistance of slag to the diffusion of oxygen could not be neglected. 2) The dissolution rate of manganese oxide might be controlled by the diffusion of manganese from the interface to iron bulk. 3) Addition of lime to those ternary slags increased the dissolution rate of manganese oxide but decreased the deoxidation rate. 4) Quasi-equilibrium states, in other words, minimum or maximum values of some components wefe observed. For the experiments using basic slags the authors developed lime crucibles utilizing appropriate amount of titanium oxide as binder in order to keep both phases, slag and metal. Because of some failures in making crucibles, attention was mainly paid to the transfer rate of manganese between metal and slag. According to the obtained results: 1) The deoxidation is a little faster than in case of acidic slag because of difference of slag constitutions. 2) The dissolution rate of manganese oxide would be controlled by the diffusion of manganese ion. 3) Silicon in iron bath increases the dissolution rate of manganese oxide. 4) The rate of elimination of manganese in iron bath by iron oxide of slag could be controlled by the diffusion of manganese in iron bath. 5) Manganese transfer between iron bath and magnesium oxide bearing slag is much slower than in case of lime bearing slag.
Nonmetallic inclusions formed in high carbon chromium steel were classified into microscopic and macroscopic ones. The behavior of their formation was studied. The results are summarized as follows: 1. During solidification of steel, oxides and sulfides which have been dissolved in melt as oxygen and sulfur, are almost precipitated, forming microscopic inclusions. Inclusions produced in melt float up and are excluded rapidly. 2. In solid steel, oxygen can not virtually be dissolved and remains as oxide. Consequently the amount of oxide inclusions increases approximately in proportion to the oxygen content in steel. 3. Although the amount of sulfide inclusions increases according to the total amount of sulfur, they can be partially dissolved in steel. Therefore the amount of sulfide inclusions is also dependent on the amount of sulfur dissolved in solid steel. Sulfur content in steel is very effective for the cleanliness of steel. 4. When microsegregation degree of steel is decreased, the amount of sulfur dissolved in solid steel is increased. Therefore the amount of sulfide inclusion is decreased. 5. When molten steel containing much oxygen is killed with aluminum, cloudlike inclusions are produced. Relation among these inclusions, various melting and casting conditions, and microsegregation is investigated. It is shown that alumina type inclusions are also precipitated during solidification of steel, and that these inclusions produced in molten steel are separated rapidly. In spite of containing much aluminum, oxygen can be dissolved in molten steel super saturatedly. 6. The melting condition for occurrence of B-type inclusions in killed steel is experimentally examined. Addition of aluminum, enrichment of oxygen and holding of molten steel are needed for occurrence of B-type inclusion. These conditions may be attributed to oxidation of aluminum in molten steel. 7. By analyzing the type of length distribution of inclusions found in steel parts, it is suggested that macroscopic inclusion is not a large inclusion which has grown up accidentally, but another type inclusion is produced under a particular condition. 8. Experimentally, macroscopic inclusion can be intentionally produced by promoting air oxidation of molten steel in teeming process. Accordingly, teeming in argon atmosphere was effective for preventing the occurrence of macroscopic inclusions. Air oxidation of molten steel by carrying air bubbles down into the molten steel in mold has much effect on the occurrence of macroscopic inclusions. 9. It is shown that there is another unknown factor for occurrence of macroscopic inclusions appearing through a certain teeming process, accompanied with air oxidation of molten steel. 10. Large inclusions adjacent to pinhole and blowhole, and B-type inclusions are regarded as a factor influencing the occurrence of macroscopic inclusions in special cases.
The rates of dissolution V of rotated steel rods (2-10mm ƒ) in molten Al (775°C), Zn (600°C) were measured. Experimental results were examined in the light of diffusion theory and it was found as follows: 1) At the lower stirring speed (Re<5×102), the rate controlling mechanism of the dissolution is Fe-diffusion in liquid metals and the obtained data can be correlated to the formula: _??_ 2) At the higher stirring speed (Re<103), the rate controlling mechanism of the dissolution depends on both processes i.e. Fe-transfer from solid alloy surface to liquid metal and Fe-diffusion in liquid metal, simultaneously. So, above equation is not applicable to these high stirring conditions.
It has been recognized that the protective atmosphere, such as RX or DX gas, is necessary to prevent the oxidation and decarburization of steels under heat treatment. Previously, we have used the popular analysing instruments, viz. Orsat's and dew point apparatus, though the quantitative and qualitative analysis of the specimens containing hydrocarbons was difficult and time-consuming by them. Gas chromatography possesses inherent advantages that make it particularly favourable for the characterization and quantitative analysis of complex mixtures. In addition to providing a direct method of analysis for unknown specimens, it has proved to be a powerful adjunct to ultraviolet, infrared and spectroscopic techniques. From the preliminary experiment, we found silica gel and molecular sieve to be moderate column packings for our objects. But, it was necessary to know the reliability of this application. So, we analyzed the results by simple statistical treatment. From the results obtained in the analysis of RX gas, it was concluded that 1) accuracy of results depends upon sample size, and the smaller the sample size, the better; 2) the results obtained from oxygen, carbon monoxide and methane have 95% confidence coefficient and±10 mm2 accuracy of profile area in the case of 1 to 5 times repetition but the results from carbon dioxide, nitrogen and hydrogen are worse; and 3) the carrier gas flow rate from 25 to 30 ml/min. is appropriate to this study.
It is wellknown that chromium has a quality as deoxydation reagent within its concentration in the liquid metal up to 3%. Using X-ray microanalyzer, authors measured the process of the growth of oxide inclusion which was produced by deoxydation reaction at the process of the dissolving of metallic chromium. The result shows that it takes much time for the growth of chromic oxide compared with other reactions.