Relationship between coking pressure and displacement of oven wall during carbonization in coke oven was investigated at Muroran No. 6 coke oven battery (preheated-coal charging system). Determination was performed at both a superannuated oven chamber after 26 years from start and a sturdy oven chamber after a year from replacement of oven top, entire walls and oven sole. Wall displacement was observed when the internal gas pressure of plastic layer at oven center became the maximum in both oven chambers. The wall displacement increased in proportion to the internal gas pressure of plastic layer at oven center, and the displacement at superannuated oven per maximum gas pressure was larger than the one at sturdy oven. The pushing force (maximum electric current of pushing machine) greatly changed according to gas pressure of plastic layer at superannuated oven compared with the one at sturdy oven. It was concluded that the wall displacement by coking pressure greatly influences the pushing force of coke cake at superannuated oven chamber.
The effect of microsegregation on porosity formation in high nitrogen steels containing high chromium under pressurized atmosphere was investigated using pressurized directional solidification furnace. In this study, it was successful to add over 0.70 mass% nitrogen in the ingot with no porosity. Nitrogen distributions in unidirectional solidification ingots were almost homogeneous regardless of the presence of porosities. In the case of low nitrogen content and peritectic solidification, porosities were observed inside the ingot solidified under nitrogen–argon gas mixture in the total pressure below certain critical value. In the case of high nitrogen content and austenitic solidification, porosity was not observed inside the ingot solidified under nitrogen gas condition. Liquidus and solidus temperature, equilibrium partition coefficient, solid fraction and temperature at peritectic transition, the relationship between solid fraction and temperature during solidification were calculated with Thermo-calc. The microsegregation tendency of nitrogen and alloying elements was simulated using Scheil equation and the modified method of Ohnaka's microsegregation model in this study. As a result of solidification simulation, in high chromium steel, it is suggested that supersaturated solution of nitrogen caused by bubble formation during solidification is likely to occur near the peritectic transition. Defined critical pressure of porosity formation in this study would be effective to determine the pressure conditions to manufacture high nitrogen steel.
RBM (Risk Based Maintenance) that is a promising technique for the maintenance of aged industrial plants. The risk here is defined as likelihood by multiplication of consequence. Likelihood is decided by means of a technical module of each damage mechanism. In each technical module, there are some damage sensitivity prediction models for several environments. Technical module is needed to determine likelihood of failure, but currently, available technical module to evaluate likelihood is limited mainly for refinery and petrochemical plants. This study is targeting to construct exhaustive technical modules. As the first step, the technical module of erosion-corrosion that is strongly required from many industries is developed. In this paper, a new corrosion rate prediction model of erosion-corrosion is proposed based on published data and the modification is done using originally collected actual plant data. Finally, it is demonstrated that the new model is adequate to predict remaining life of the plant that is damaged by erosion corrosion.
We investigated the effect of B1 compounds on ferrite transformation during continuous cooling in C–Mn steel. TiO, TiN and MgO were employed as B1 compounds of similar lattice parameters to exclude the effect of lattice matching. Single-crystalline grains of the B1 compounds were hot-pressed with steel and embedded in austenite grains by subsequent reheating in austenite region, which were then cooled at 1K/s or 5K/s. Polygonal ferrite was found at all the interface of the three compounds similarly in the case of 1K/s cooling, where the Baker–Nutting (B–N) orientation relationship was well-identified between the ferrite and all the compounds. In the case of 5K/s cooling, ferrite formed from only some parts of the interface of MgO while still from the entire interface of TiO and TiN. The portion of ferrite developed from TiO without the B–N relationship increased, while such trend was not found in ferrite from TiN and MgO. First principle calculation suggests that interfacial energy is the lowest when the B1 compounds and ferrite lie with the B–N relationship, and the energies of the interfaces of TiN and TiO are lower than that of MgO. Increase in interfacial energy is significant for the interface of TiN without the B–N relationship, while negligible for the interface of TiO. Those results are explained by electron bonding behaviors at the interface between ferrite and the B1 compounds, and are well correlated with ferrite formation from the B1 compounds observed.
To strategically discuss how steel should be produced, used and recycled, understanding of current and future flow and stock of steel is of high importance. Because steel is used in the society for many years, records in the relevant industries including import and export from the past years are crucial as well as the current up-to-date statistics when illustrating flow and stock of steel in a year. Following the pioneering national flow and stock figures developed in Japan, this paper presents Taiwanese 2006 and 2007 versions of illustration of iron and steel flow, stock, and recycling, as well as list of data sources, estimation method for missing data, prediction method for the future flow and stock and recommendation for future refinement. The methodologies were modified basing on the Japanese method, due to differences in data availability, collection methods and social background of the data. Using a bottom-up approach, stock and obsolete scrap flows are estimated for three major household appliances, i.e. washing machine, refrigerator, and air conditioner. From comparison of the 2006 and 2007 versions, increasing importance of scrap materials in Taiwanese crude steel production and increase of importance of external market can be seen. Increasing the number of steel products covered by bottom up approach and its combination with top-down approach is recommended, as well as the refinement of assumptions from accumulating recorded data to increase completeness of the future versions.