Physical Property Influence on Foaming Index of Refining Slag

The foaming indexes of a group of refining slag were measured. The refining slag with better foaming ability was chosen,its composition (mass frachon in %) is CaO, 53.25, SiO2, 17.75, MgO, 9; Al2O3, 15 and CaF2, 5. The relationship between slag foaming index and physical properties of the slag was obtained by dimensional analysis, and the expression indicates that viscosity of slag is the most important factor which influences foamng index. The influence sequence of slap composition on foaming index was also obtained as follows: CaF2→MgO→Al2O3→ B (CaO/SiO2).

Oxidizing Capability of Refining Slags Containing BaO

According to the coexistence theory of slag structure melts, the oxidizing capability of the refining slag CaO-MgO-FeO- A12O3SiO2 is studied and the relationship between the mass action concentration of FeO (NFeO) and the activity of FetO (αFetO) for this slag is found to be as NFeo=0.656 1 αFetO. Furthermore, the calculating model of oxidizing capability of the refining slag BaO-CaO-MgO- FeOA12O3-SiO2 is established. A satisfactory result is obtained when using the above oxidizing capability relationship to calculate the desulphurizing capability of such refining BaO-slags.

Development of RH refining technology at Baosteel

With the strong demand for the development of automobile sheets, tin plates, household appliances, silicon steel, pipeline steel and other products as well as for the quality improvement of steel products, remarkable progress has been made in RH refining technology and equipment design since Baosteel began production more than 20 years ago. The vacuum degassing ratio of Baosteel has jumped from 35% in the initial stage when Baosteel began production, to the current ratio of approximately 60%, and will soon reach 75% in the near future. The independent innovations in RH refming technology in Baosteel, such as RH equipment optimization, vacuum decarburization, inclusion control, deoxidation, desulfurization, rhythm adjustment between primary steelmaking and continuous casting, the high efficiency of the RH refining process, and other aspects of RH technology, have all effectively met the requirements of developing new steel products, quality improvement and logistical control. Complete sets of RH equipment and refining technology have been successfully exported to the domestic steel plants. In the future, Baosteel will make further efforts to improve efficiency, stabilize production and quality, and realize special line production, so that the RH degasser will play a greater role in Baosteel.

Correction of secondary deformity of unilateral cleft lip with refined anatomic repair in orbicularis oris muscle

Objective To investigate the functional repair of secondary deformity of unilateral cleft lip. Methods The nasal branch,nasolabial branch,and labial branch of orbicularis oris muscle were dissected and repositioned precisely to correct the secondary deformity of unilateral cleft lip. Results 96 parients were treated

Technological progress in the production of pipeline steel at Baosteel

Baosteel started the production of pipeline steel in the early 1990s. The company has so far produced more than 4 Mt of API X42-X80 and hydrogen sulfide resistant X52-X65 steel. In 2006, it succeeded in producing X100 and X120 pipeline steels,which have been used in many important projects, such as the oil transporting project in the Tarim Basin, the pipeline project in Sudan,the West to East gas pipeline project,the Sino-Russian oil transporting project,etc. Baosteel has made great progress in the purity control of pipeline steel, the homogeneity control of slab composition and surface quality over the last ten years. The company has achieved this by improving its steelmaking equipment and operation management technology,and by integrating its process technology. The phosphorus and sulfur levels of the pipeline steel have been decreased to 50 ppm and 12 ppm respectively （1 ppm = 10-6）.

Improvement of the Structure and the Electromagnetic Characteristics of an Induction Ladle Furnace

Based on a numerical analysis of the alternating electromagnetic field in the process of Steel refining with an induction ladle furnace (ILF), the optimization of the structure of ILF and the electromagnetic field for melting is realized in the present work. The optimization of the ILF by outward extension of inner yokes can decrease the magnitic flux leakage obviously, reduce the eddy current energy loss dramatically and then, decrease the total power consumption.

Analysis of inclusion and purity in steelmaking process

The paper mainly discussed the inclusions and the purity of molten steel and continuous casting slab in tapping,argon-bubbling,LF refining,VD vacuum degassing and continuous casting tundish processes during the steel making.At the same time,the improvement measures of smelting process were indicated. Si-Al-Ba alloy and Ca-Si deoxidation eventually were adopted in 120 t converter.The amount of the tapping was about 135t.After feeding Al wire and adding premelted slag in furnace,picked up the sample after the bottom argon-bubbling which had been done for over 5 minutes.The lime,fluorite,calcium carbide and Al powders were used to produce white slag in LF.Then the alloy compositions were adjusted. Feeding Ca wire after the treatment,and took out over 5 minutes' soft converting.The VD vacuum degassing should be kept for 15 minutes bellow 1.5 torr.After that,Ca wire could be fed.Finally,casting the slab into the size of 260 mm×2 280 mm. The research showed: (1) In converter procedure,the dephosphorization effect turned out good when the ratio of dephosphorization was 88.2%.The final oxygen and nitrogen contents satisfied the demand,and the effects of the final control and bottom-blowing were good. (2) During the LF refining process,the nitrogen seldom added.It showed the excellent sealing effect and the optimization of techniques on operating which had reached the domestic leading level. (3) After the VD vacuum degassing process,the Si,Mn,P,O,N contents were almost steady.The sulphur content kept decreasing to 0.003%and the[H]content was 1.9 ppm.The effect of the vacuum degassing process was good. (4) The oxygen content was controlled at 11 ppm in the continuous casting process,and the nitrogen content had increased to 53ppm with theΔ[N]28 ppm.Therefore,in order to prevent the molten steel from reoxidization,the protection of the continuous casting should be controlled rigorously. (5) The inclusions that existed before the LF refining process were mostly MnO-Al_2O_3-SiO_3 composite inclusions,while the inclusions were mostly calcium-aluminates inclusions after feeding Ca wires to LF or VD furnace.When the Ca/Al had reached to 0.1,7 Al_2O_3 12CaO were produced.The compositions and the sizes of the inclusions in continuous casting slab had changed obviously after the Ca treatment.The sizes were all within 100μm. (6) In order to prepare for the exploitation of the high-quality clean steel,the best process for feeding Ca wire,in LF or VD,and whether it should take one-step wire-feeding way or two-step way as well as the techniques of feeding Ca wire need to be studied further.The desulphurization in LF refining process didn' t reach balance.The ratio of desulphurization could be improved if extending the LF refining time and improving the kinetic condition.

Improvement in prolonging AOD refractory lining life in Baosteel

A series of improvements in prolonging the AOD refractory lining life in Baosteel are introduced and analyzed in this paper,including modification of the AOD shell shape, adjustment of the top slag components and selection of the side-blowing tuyeres. Firstly,the layout of side-blow tuyeres was altered with the angle between each two tuyeres being 22.5° instead of the original 18° ,and the connection of the outside steel shell in the side-blow area was modified from the former platform shape with great stress concentration into a new smooth circle shape. Secondly,the slag components were changed from the former CaO-FeO-SiO： system to the CaO-MgO-SiO2 system. Besides, the basicity of the top slag was kept higher than 1.8 ,and the MgO content in the slag was kept within the range of 8% - 12%. Finally,tuyeres with an inner diameter 13% smaller than that of the original tuyeres were used. Based on these research and optimization work,the thermodynamics and kinetics in the AOD refining bath has been improved markedly, and the campaign of the AOD has been prolonged from 45 heats at the beginning of its start-up to the current 185 heats. Meanwhile,the yield of chromium alloy and the decarburization efficiency have also been improved.

The development and future of steelmaking technology at Baosteel

Baosteel＇s steelmaking has developed greatly over the last 30 years in the areas of hot metal pretreatment, converter, electric arc furnace （EAF）, secondary refining, continuous casting, stainless steel and the comprehensive utilization of resources. The development of technologies, such as clean steel production, mhrstahl heraeus （RH） vacuum refining,a breakout prediction system for slab continuous casting and rotary cylinder slag treatment has created a good environment for the development of value-added products and the comprehensive utilization of resources at Baosteel. This paper describes the direction of development of Baosteel＇ s steelmaking in the future.

Direct Current Electric Arc-Electroslag Ladle Furnace

In order to solve the high consumption problem of small capacity ladle furnace (LF), the operation principle and control method of the DC are and electroslag heating ladle furnace are introduced. With only one arcing electrode, the distance between the are and the wall of ladle is enlarged, and consequently the consumption of the ladle refractory is decreased. In the invention, a signal electrode is embedded in the refractory lining of the ladle, which contacts directly with the liquid steel and the ladle shell. Two graphite anode ends are submerged in the slag layer. The signal electrode is used as voltage reference during refining process. The electroslag voltage between anode end and liquid steel is applied to control the depth of anode end in the slag layer during the refining process with this ladle furnace.

Study on formation of non-metallic inclusions with lower melting temperatures in extra low oxygen special steels

Investigations were made both in laboratorial and industrial scales on formation of non-metallic inclusions with relatively lower melting temperatures to improve the fatigue property of the special steels which contained extra low oxygen.It was found in laboratory studies that steel/slag reaction time largely affected non-metallic inclusions in steel.With the slag/steel reaction time increasing from 30 to 90 min,inclusions of MgO-Al2O3 spinel were gradually changed into CaO-MgO-Al2O3 system inclusions which were surrounded by lower melting temperature softer CaO-Al2O3 surface layers.By using high basicity and as much as 41 mass% Al2O3 refining slag,the ratio of the lower melting temperature CaO-MgO-Al2O3 system inclusions was remarkably increased to above 80%.In the industrial experiments,it was found that the inclusions changed in the order of "Al2O3 →MgO-Al2O3 system→CaO-MgO-Al2O3 system" in the secondary refining,and the change from MgO-Al2O3 system to CaO-MgO-Al2O3 system took place from the outside to the inside.The diffusion of CaO and MgO inside the layer of CaO-MgO-Al2O3 was considered as the controlling step of the inclusion transfer.Through LF and RH refining,most inclusions could be transferred to lower melting temperature CaO-Al2O3 and CaO-MgO-Al2O3 system inclusions.

Cleanliness of Alloying Structural Steel

Alloying structural steel used for mechanical structures has a high requirement for cleanliness because its failures are greatly affected by non-metallic inclusions and total oxygen content in steel.It has been reported by some steelmaking plants to have some problems in controlling total oxygen content and inclusions during alloying structural steel production.For this purpose,cleanliness control in 0.2C-0.3Si-0.6Mn-1Cr-0.2Mo steel was investigated.Firstly,low melting temperature zone（≤1873 K） of CaO-Al2O3-MgO system and formation condition of low melting temperature inclusions were investigated through thermodynamic equilibrium calculation.On this basis,industrial tests were carried out.Through sampling at different stages,transformation of oxide inclusions and change of total oxygen content in steel were studied.The results show that：in order to form CaO-Al2O3-MgO system inclusions with low melting temperature,mass percent of Al2O3,MgO and CaO in inclusions should be controlled from 37.6% to 70.8%,0 to 17.4% and 25.5% to 60.6%;For the condition of 1873 K and 0.05%（mass percent） dissolved aluminum in steel,the activities of dissolved oxygen,magnesium and calcium should be controlled as 0.298×10-4-2×10-4,0.1×10-5-40×10-5 and 0.8×10-8-180×10-8 respectively.With secondary refining proceeding,average total oxygen content and inclusion amount decrease,the type of most inclusions changes from Al2O3 after tapping to Al2O3-MgO after top slag is formed during ladle furnace refining and finally to CaO-Al2O3-MgO after RH treatment.In the final products,average total oxygen content was 12.7×10-6 and most inclusions were in spherical shape with size less than 5 μm.

Overview:Development of Clean Steel Production at Baosteel

The development of clean steel technology at Baosteel can be dated back to the first production of IF steels and pipeline steels in the early 1990s.Now the technology has gradually covered nearly the whole range of products.This progressive development is introduced in the overview including the levels of cleanliness for some steel grades at Baosteel.The technologies at different processes for the production of clean steel and the removal of some impurity elements in molten steel are also discussed.Suggestions are given on the future research and development of clean steel technology at Baosteel in the aim to keep a sustainable development,which should focus on the basic research,inclusion control and making efficient use of inclusions,as well as stable and reliable low-cost manufacturing technology,removal of harmful residual elements,and the expanding of the technology to stainless steels and special steels.

Numerical model of inclusion separation from liquid metal with consideration of dissolution in slag

The transport of inclusion particles through the liquid metal/molten slag interface and their dissolution in the slag are two key processes of inclusion removal.Based on the latest version of inclusion transport model that takes into account full Reynolds number range and a dissolution kinetics model,a coupled model was developed to simulate the whole process of inclusion removal,from floating in the liquid steel to crossing the interface and further to entering and dissolving in the molten slag.The interaction between the inclusion motion and dissolution was discussed.Even though the inclusion velocity is a key parameter for dissolution,the simulation results show no obvious dissolution during moving state because the process is too short and most of the inclusions dissolve during its static stay in the slag side above the interface.The rate-controlling step of inclusion removal is the transport through the steel-slag interface for the small-size inclusion and static dissolution above the interface for the large-size inclusion,respectively.

Construction of High-Efficiency and Low-Cost Clean Steel Production System in Shougang Jingtang

This paper analyzes the technology for clean steel production in modern iron and steel plant,a philosophy with production efficiency,manufacturing cost and product performance in its core.It also makes a review on functions of high-efficiency,low-cost and high-quality steel products manufactured by the new generation iron and steel plant,in combination with the study on design of steelmaking-continuous casting process of Shougang Jingtang iron and steel Plant.By applying precise and dynamic design system to optimize and allocate systems and working procedures of hot metal pretreatment,converter smelting,secondary refining,continuous casting process,etc,a platform of high-efficiency,low-cost and high-quality clean steel production is built.

Process Analysis and Practice of Clean IF Steel Production

Based on the current process and equipment conditions of No.3 steelmaking and continuous rolling plant, which consists of desulphurization and slag skimming of hot metal, 260t combined blown BOF, rimmed steel tapping with slag stopping process, RH-TB vacuum treatment process and medium thin slab continuous casting, the methods for improving cleanliness of IF steel in BOF smelting, RH vacuum treatment and continuous casting were investigated. According to results of theoretical analysis and experiments, a series of quality controlling schemes were proposed for improving cleanliness of IF steel via controlling chemical composition, T[O] content, tapping temperature, shrouded casting and controlling stability of continuous casting.