Steelmaking

Study and practice on technologies of deep dephosphorization with single slag in 260 t combined converter

2011, 27(2): 1-5. doi:

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Based on the technical study of deep dephosphorization with single slag in the 260 t combined blowing converter some key controlling parameters which affects dephosphorization effect in converter such as blowing, forming and temperature etc, are optimized. And by taking rephosphoration control measures such as tapping with stopping slag, adopting low phosphorus alloy and modifying the top slag in ladle etc, the average phosphorus mass fraction could reach 75×10-6 at tapping in combined converter with single slag, and the average phosphorus mass fraction in finished product could reach 98×10-6.

Control practices of converter production with high cold charge ratio

2011, 27(2): 6-9. doi:

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n light of the problem such as temperature and composition fluctuation,low hitting rate at the end point of converter production with high cold charge ratio ,a technology has been integrated and developed in Sansteel MinGuang Co., Fujian. It consists of four key techniques namely, 1) doublecombining process in single converter with high cold charge radio, 2) Quicktap automation steelmaking, 3) tapping with slag controlling and 4) deoxidization with CaC2. Compared to the conventional steelmaking process, phosphorus mass fraction at tapping is lowered by 0.0112 %，about over 50 %，CT double hitrate is 90.82 % and reblow rate is decreased from 28.37 % to 6.76 % and submaterial consumption for converters is decreased to 55 kg/t. Slag layer thickness in ladles after tap is controlled within the limit of about 27 mm.

Industrial test of 20CrMnTiH gear steel produced by BOFrectangular bloom caster route

2011, 27(2): 10-12. doi:

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The 20CrMnTiH gear steel is successfully produced in BX Steel Group by adoption of the technological route of “hot metal desulphurization pretreatment→combined blown process→LF plus RH refining→rectangular bloom CC (350 mm×470 mm)→hot charging walking beam type reheating furnace→24 high heavy rigidness and short stress rolling mill→temperature hold→finishing packing”. The chemical compositions of the finishing products Φ90～180 mm gear steel are in conformity with the controlling index and each and every physical examination index completely meets the technological requirements.

Formation and control of longitudinal corner crack in heavy rail steel bloom

2011, 27(2): 13-15,3. doi:

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n view of the longitudinal corner crack appearing in heavy rail steel factors causing the formation of the corner cracks such as mould precision, property of mould flux, casting temperature, fluctuation of mould level and operating process are analyzed. Results of study show that undesirable mould precision and low quality of mould flux as well as substandard operation are principal factors leading to formation of corner cracks. The corner cracks can be effectively controlled by intensifying the mould examination, improving the properties of the mould flux, optimizing the structure of nozzle and normalization of operation.

Practice in controlling the quality of rectangular billet

2011, 27(2): 16-20. doi:

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Combined with the current situation of Chongqing Iron and Steel Co., Ltd., the reasons for rhombic、sag、bulging and inner crack of rectangular billet are analyzed and found that the primary cause to the quality defect is that the copper tube of the mould does not match with the steel grade and the casting speed. Thereby preventative and optimization measures are set up and the practical results are desirable.

Optimization of mould flux in continuously casting corrosionresistant steel by FTSR process and countermeasure for slab corner transverse crack

2011, 27(2): 21-24,6. doi:

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In the process of trial production of the corrosion resistant steel used for heating radiator by FISR technology in Tonghua Iron & Steel Co., corner transverse crack and sticking accidents are apt to occur. In order to improve the uniformity of the solidification shell newly formed in the mould the chemical compositions and properties of the mould flux are optimized under the prerequisite that the good lubricating ability be ensured and thereby soft cooling of the shell at the meniscus of the mould is realized. Thereupon the cooling process for the mould and the second cooling segment is optimized and technical measures for prevention of corner transverse crack are put forward. As the results the surface quality of the thin slab is improved.

Analysis of inclusions in cold rolling deepdrawn steel

2011, 27(2): 25-28,4. doi:

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The present paper introduces the content variation of T.O and N and inclusions in the cold rolled and deepdrawn steel DC06 and DC04 in refining the steel grade with LD→RH→CC route. The T.O mass fraction of DC06 through three minutes of RH alloying treatment is 77.08×10-6 and 44.98×10-6 in the end of refining and 44.38×10-6 in tundish and 24.23×10-6 in slab; that of DC04 is 69.35×10-6、41.55×10-6、38.05×10-6 and 23.55×10-6 respectively. In the process of RH refining N content is slightly reduced and in the pouring N pickup occurs to some extent. In the RH treatment and in the pouring the inclusion removal rate of DC06 is 44.0% and 32.7% respectively; and that of DC04 is 24.4% and 12.1%. In the location away from distance of a quarter of inside arch of the slab there are more micro inclusions of the unit area of the the slab than in other area. And this paper puts forward some control measure of the inclusions, it has great significance for production of clean steel.

Ti content control of GCr15 bearing steel

2011, 27(2): 29-32. doi:

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Proceeding from the point of view of bearing steel production and quality requirements the main elements that influence \[Ti\] content of bearing steel are analyzed and discussed by laboratory experiments and statistical data of massive production. This paper discusses emphatically the effect of slag basicity, Al2O3, TiO2and AlS on the average mass fraction of titanium in bearing steel. The mass fraction of titanium in the steel can be controlled within the limit of 45×10-6by technical optimization.

Preliminary research on the behavior of limestone charged intoconverter in the process of making slag

2011, 27(2): 33-35,5. doi:

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The behavior of limestone which is utilized for slagging instead of lime during converter steelmaking process was discussed with the data collected from laboratorial and industrial experiments. The result can be concluded that: limestone which is directly charged into converter as slagforming material during early period of steelmaking process can be quickly decomposed and involved in making slag and in addition it has more advantages over lime in several respects; the anticipant result can be achieved using limestone to make slag, and limestone is completely decomposed during 5~6 minutes in converter steelmaking process; high temperature is propitious to calcium carbonate decomposing, just as the result of laboratorial experiments shows that the decomposition rate of CaCO3 at 1 400 ℃ is 3～4 times greater than that at 1 100 ℃ in spite of only 300 ℃ difference, therefore, the early period temperature has a great effect on the decomposition and slagging processes.

A probing to technology of smelting high carbon steel with high manganese pig iron

2011, 27(2): 36-40. doi:

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According to the thermodynamic equation of selective oxidation of CP and test results some regularities of smelting highcarbon steel have been discussed. It's determined that the best operating schedule for smelting the high carbon steel is the schedule of "highlowhighlow" oxygen pressure and operation at the lance position and the best slagforming schedule is assumed to be double slag process with appropriate amount of deslagging. A criteria value for the optimal slag series is put forward as well.

Analysis on decarburization rate based on numerical simulation in EAF steelmaking

2011, 27(2): 41-44,6. doi:

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A threephase and threedimensional mathematical model for a 150 t EAF has been established with CFD software. The results of numerical simulation on the jet flow impingement depth are compared with that of the extrapolation by the water model experiments and they are in good agreement with each other. Simulation results show that an exposed liquid steel surface uncovered with slag layer is formed at the bathe surface due to the impingement of the oxygen jet flow and the exposed liquid steel surface is the main area where oxygen and the liquid steel are in contact with each other. By means of the infrared fume analytical technology based decarburization model the decarburization rate under the different conditions of the oxygen flow is measured in the process of EAF steelmaking and effects of the liquid steel flow rate flowing over the exposed surface on the reaction rate of decarburization is analyzed as well.

Study on control of refining slag in clean steel production

2011, 27(2): 45-47,5. doi:

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The ladle slag control process in clean steel production is introduced and various properties of the modified refining slag investigated. Results show that the FeO and MnO quality fraction in the slag could be lowered to less than 3 % and low melting point and low viscosity ensured sound fluidity. The dissolution rate of Al2O3 into slag is relatively high, which resulted in high level of slab cleanliness. Strong desulphurization capability is obtained owing to the high optic basicity and desulfurization capability.

Study on using LF cold slag for desulphurization

2011, 27(2): 48-51. doi:

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The present paper studies the compositions and sulphur content of the LF cold steelmaking slag series in the Anlong Iron & Steel Co., Ltd. and analyzes and discusses about thermodynamic and kinetic factors affecting the liquid steel desulphurization and puts forward the technological measures in respect of desulphurization of LF refining, in connection of the practical steelmaking conditions and characteristics of steel grades, in order to improve the oxidizability, Mannesmann index and amount of CaF2 in the slag. It also introduces technologies of how to reclaim the cold state steelmaking slag of the LF furnace for desulphurization purpose and therefore provides a more practical approach to the energy saving and consumption reduction for the iron and steel sector of China.

Study of inclusion size distribution in tundish of continuous casting machine

2011, 27(2): 52-55. doi:

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The size distribution of Al2O3 inclusion in Al killed liquid steel in the tundish is studied with a mixing model of constant flow stirred tank reactor and piston flow reactor. The flow fields and inclusion removal ratios of bare tundish and the tundish with dams and weirs are compared and the inclusion removal ratio of bare tundish is only 19%. However by installation of dams and weirs in the tundish the inclusion removal ratio reaches 37 %, which is greatly superior over that of the bare one owing to continuously growth of the grain sizes of the inclusions arising from turbulent flow and piston flow caused collision of the inclusions with each other.

Water model experiments on surface flow fluctuation patterns in slab caster mold

2011, 27(2): 56-60. doi:

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Using the slab caster mold of a specific steelmaking plant as prototype a water model with 1∶1 scale is built up and effects of the processing parameters such as drawing speed, outlet angle and submerging depth of the submerged nozzle and structure of the bottom of the water gate on the inner flow field and surface fluctuation of the slab mould are studied on the basis of the instantaneous wave height and the processing parameters for optimizing the flow field of the mould are put forward so as to provide necessary guide for reduction of slag entrainment in the mould in the actual production. Results show that drawing speed is the greatest influential factor to the level fluctuation of the mould and inclination of the nozzle is the next. The influence of each and every processing parameter on the inner flow field of the mould is restricted with one another; and in accelerating the drawing speed the submerging depth of the nozzle has to be increased appropriately so as to avoid slag entrainment due to surface fluctuation.

Numerical simulation on molten steel temperature drop of 210 t ladle

2011, 27(2): 61-64. doi:

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By means of establishment of a finite element heat transfer mathematical model the transient temperature fields of the ladle during heat transfer process are simulated. The effect of different baking temperature and different adiabatic layer material of 210 t ladle on molten steel temperature drop is investigated by employing typical value method and energy conservation method. Molten steel temperature drop rate in different conditions has been predicted and the predicted values are compared with the measured ones. The results show that the temperature drop of the liquid steel is greatly affected by the baking temperature of the ladle; and the temperature drop rate of the hot metal in the process of casting is greater than that of the hot metal at stand by status; the onsite measured temperature drop rate lies in between the calculated value by the energy conservation method and by the typical value method. The simulation results provide a theoretical basis for reduction of the molten steel temperature drop in the Steelmaking Plant of Chongsteel.

Study on characteristics of flow area in annular gap washing device in converter

2011, 27(2): 65-67. doi:

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Characteristics of the flow area of annular gap washing device is investigated in this paper. The relationship between the minimum flow area and the position of movable inner cone is defined by a general formula.Based on this relationship, the formula of blocking flow rate is given，which can be used as a reference for the AGE design or operating.

Application of expert system of mould in continuous casting in Lingyuan Steel

2011, 27(2): 68-70. doi:

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The present paper introduces installation of an expert system of mould in the continuous caster of the Converter Steelmaking Plant in Lingyuan Iron & Steel Group Co., Ltd. Results of practical running show that the system is running perfectly well. By application of the system not only the adhesive breaking out accident can be prevented, but the abnormal conditions of the processing parameters of the mould can also be measured out instantly and in the meanwhile the plan of mould flux and other operation is also optimized and thus the occurrence rate of longitudinal crack and adhesion is accordingly reduced.

Review of heat transfer between mold and strand through mold flux film in continuous casting

2011, 27(2): 71-73,7. doi:

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This article is an overview about the recent researches on heat transfer performance of mold flux between mold and strand, its detection methods and heat transfer calculation both at home and abroad. It is concluded that the present heat transfer detection method which is based on the principle of one-dimensional theory can reflect the essential heat transfer properties of the mould flux and it can be used as the basis in selection of the proper mould flux. However it's considered that the research work uptodate is barely confined in very simple treatment on the slag film structure of the mould flux and ignores the heat transfer of the mould flux near the meniscus. Therefore it is needed to strengthen the study of heat transfer calculation of mould flux.

Status quo and progress of deoxidation technology for clean steel

2011, 27(2): 74-77. doi:

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The present paper introduces the status quo of the secondary refining (deoxidation) technology for clean steel making purpose, expatiates new progress of deoxidization by Mg evaporation method and the research on inclusions of deoxidization by titanium at JEF as well as the technical characteristics of deoxidization method using Ti plus rare earth adopted by Nippon Steel and indicates that formation and distribution of the inclusions in the process of hot metal deoxidization can be predicted and simulated by CFD model and points out that deoxidization by electrochemistry is a brand new technology for hot metal deoxidization without contamination and deals with the progress of application of oxygen penetration film in hot metal deoxidization by electrochemistry in POSCO.

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