De Yong Wang

Sulphur Removal from Sulphur Containing Phase(CaS) in Ladle Slag by Oxidizing Roasting

Slag is the main by-product of iron and steelmaking process. Ladle slag, melted fully after secondary refining, usually contains rich CaO, Al2O3 and 2CaO·SiO2 phase, which has a potential value to recycle into steelmaking process as the substitution of lime. However, reuse of ladle slag is easy to induce an accumulation effect of sulphur or phosphorus. In this present work, CaS powder was used to replace the sulphur containing phase in ladle slag to investigate the roasting process under different atmosphere conditions. The influence of temperature and oxygen pressure on sulphur removal mechanism and products composition has been discussed. By adding solid sulfur into molten ladle slag, the results of SEM has showed that sulphur element in ladle slag existed as independent CaS phase. Roasting experiments showed that lower oxygen pressure and higher reaction temperature were beneficial for CaS changing into CaO, it was very important to design the optimum roasting route for sulphur removal from the ladle slag.

A Coupling Dynamic Model for the Process of Chromium Ore Smelting Reduction in a Converter

Based on the mass and energy conservation, the coupling dynamic model for interfacial reaction between slag and metal was established using metallurgical thermodynamics, dynamics and reaction engineering. The different influencing factors were investigated and discussed. The results of the model show that the mass transfer of Cr2O3 in the slag phase is suggested to be rate-determining and the coke as reducing agent should be supplemented in the slag continuously. The model described and resolved the process of chromium ore smelting reduction in a converter preferably. A reference and basis on the constitution of rational processing route for a practical stainless steelmaking were provided.

Research on the Thermodynamics and Kinetics of Chromium Ore Smelting Reduction Process for Producing Stainless Steel

For describing and resolving the process of chromium ore smelting reduction preferably, the research status on the thermodynamics and kinetics of chromium ore smelting reduction process was summarized, based on the introduction of the process for smelting stainless steel with hot metal in a converter. The existing problems for smelting stainless steel by chromium ore smelting reduction in a converter were also discussed and some suggestions were made for the future work. A lot of investigations about the thermodynamics and the reduction mechanisms of chromium ore have been done. However, the consistent view about the thermodynamic feasibility and the mechanism of smelting reduction has not been achieved, so the application of research results is limited. Little work about the reaction kinetic model for the production of stainless steel by chromium ore smelting reduction and direct alloying has been done. So the synthetic kinetic model including a dissolution model and a reduction model of chromium ore should be built to predict and control accurately the process.

Material Balance Calculation of Chromium Ore Smelting Reduction and Direct Alloying Process in a Converter

The production process of stainless steel by chromium ore smelting reduction and direct alloying is an important and advanced way to raise the productivity of stainless steel, decrease the production cost, save electric energy and improve the economic profit. The material balance calculation of producing stainless steel crude melts by chromium ore smelting reduction in a 150 t converter is carried out by use of the empirical data and the calculation method of refining plain carbon steel in a converter, according to the blowing conditions of 185 t smelting reduction converter of No.4 steelmaking shop in Chiba Works of JFE Steel. It includes the actual oxygen consumption, furnace gas composition and occurrence amount, mass calculation of stainless steel crude melts and preparation of total material balance table. The absolute error of material balance is -2.859 kg and the relative error is -0.169%. The error is very small, so the material balance calculation can provide certain quantitative basis for determining reasonable design parameters and increasing smelting technology economic indicators.

Mixture Calculation of Chromium Ore Smelting Reduction Process in a Converter

The mixture calculation of producing stainless steel crude melts by chromium ore smelting reduction in a 150 t converter is carried out by use of the empirical data and the calculation method of refining plain carbon steel in a converter, according to the blowing conditions of 185 t smelting reduction converter of No.4 steelmaking shop in Chiba Works of JFE Steel. The calculation results show that the required total consumption of chrome ore, coke and limestone in the smelting reduction process is 224.942 kg, 154.9 kg and 99.223 kg, respectively, under the conditions of this calculation. The total amount of slag includes the amounts of hot metal elements oxidation into slag, lining erosion into slag and chromium ore, coke and adding flux into the slag, which is calculated respectively according to the basic raw data and the set values of process parameters. The slag component is confirmed, namely, the actual basicity w(CaO)/w(SiO2)=2.6, the percentage of CaF2 in slag is 3~4 wt%, and the calculated w(MgO)/w(Al2O3)=0.7. In the actual production, the addition of chrome ore, coke and flux is increased by 3%, 2% and 1%, respectively.

Heat Balance Calculation of Chromium Ore Smelting Reduction Process in a Converter

The heat balance calculation of producing stainless steel crude melts by chromium ore smelting reduction in a 150 t converter is carried out by use of the empirical data and the calculation method of refining plain carbon steel in a converter, according to the blowing conditions of 185 t smelting reduction converter of No.4 steelmaking shop in Chiba Works of JFE Steel. In the heat balance calculation, the heat consumption is calculated according to the actual reduction process in the converter and the thermal efficiency and the coefficient of thermal energy of smelting reduction converter are calculated. The calculation results show that the thermal efficiency η is 60.143% and the coefficient of thermal energy KT is 71.743%. The calculated relative error of heat balance is 0.019%. Heat balance calculation is an important part of the converter smelting process calculation, and it is extremely significant in the pursuit of the converter production of high quality and low energy consumption.

Effect of Ball Milling on Reaction Mechanism between Ti and B4C and Subsequent Densification

The effect of ball milling pretreatment of the starting Ti and B4C powder blends on the synthesis of dense TiB2/TiC composite was investigated. X-ray diffraction analysis showed that the TiC phase was not produced until the milling time was up to 18h and only a minimal amount of TiB2 was generated, even after 48h of milling. It is clear that no complete conversion of the starting reactants to the desired products characterized as TiB2/TiC powder mixture take place within the investigated conditions. The decreased particle sizes of the reactants and high concentration of defects induced from ball milling, allow the completely chemical reaction of reactants into the desired composition (2TiB2/TiC), corresponding to the rapid and significant sample shrinkage occurring before 500°C. The target products obtained starting from mechanical activation reactants also showed relatively uniform microstructures and densities greater than 98% of the theoretical value.

Reduction Feature and Selection Principle of Chromium Ore for Stainless Steelmaking in a Smelting Reduction Converter

This paper starts with the mineral structure, reducing properties of chromium ore and the physical and chemical properties of chromium oxide and discusses the requirements of the chemical composition of chromite and confirms the selection principle of chromium ore and reducing agent of chromium ore smelting reduction. The chemical compositions of the available chromite request the relatively high contents of chromium and iron, the lower contents of Al2O3, MgO and P in gangue and the lower Cr/Fe ratio in keeping with the case of high chromium. Chromoium ore in South Africa is considered to be suitable for smelting stainless steel crude melts in a smelting reduction converter. From the reducing power and economy angle, carbon as a reducing agent is more suited to reducing chromium ore.

Study and Design of Chromium Ore Smelting Reduction Process for Producing Stainless Steel in a Converter

This paper describes the concept of the construction of steelmaking shop, which is carried out as part of a modernization plan aimed at creating a 21st century environmental-friendly iron and steel works, designs the smelting reduction process of producing stainless steel crude melts in a 150 t converter and presents an outline of the equipment specifications and the conditions of operation, according to the blowing conditions of 185 t smelting reduction converter of No.4 steelmaking shop in Chiba Works of JFE Steel. In the future, a rational production system will be constructed by flexible selection of raw materials in response to changing stainless steel raw material prices and further improvement in productivity and quality, making the maximum use of functions of the equipment.

Process Calculation of Producing Stainless Steel Crude Melts by the Chromium Ore Smelting Reduction in a Converter

The process calculation of producing stainless steel crude melts by smelting reduction in a 150 t converter is carried out for the first time by use of the empirical data and calculation method of refining plain carbon steel in a converter, according to the blowing conditions of 185 t smelting reduction converter of No.4 steelmaking shop in Chiba Works of JFE Steel. Using the self-programming procedure for the processing calculation, the proper coke quantity and a complete set of calculation data for the process of smelting reduction in a converter are obtained, including the batch calculation, the material balance and heat balance calculations. The calculation results show that the increase of PCR can decrease the quantity of coke and actual oxygen consumption considerably, and improve the thermal efficiency of smelting reduction converter. For producing 18 wt% Cr stainless steel crude melts, comparing with the process of electric arc furnace, the process of smelting reduction in a converter can reduce the production cost greatly. The use of the recycled metal containing chromium can shorten blowing time and improve the yield of chromium.