Steelmaking

Controlling on the quality of special steel billet produced by BOF-LF-CC process

CAI Kai-ke;SUN Yan-hui;QIN Zhe

2008, 24(04): 1-7. doi:

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Quality of finished steel product were effected by billet quality produced by BOF-LF-CC process. In this paper, [C] controlling in BOF, deoxidization and inclusions controlling, molten steel composition, top slag controlling and billet Internal quality were analyzed by anther experience and references. The demand of special for middle/high carbon strand must be content as follow us: the molten steel composition controlling in a narrow rang, molten steel being clean(T.O about 20×10－6), billet Internal steel qualing free defect (minimized shrinkage ), billet centre element (C, Mn, S, P)segregation should be minimizing. According to the practice production of home and abroad, the demand mentioned above can be met by reasonable technology in BOF-LF(VD)-CC process.

Quality analysis and process control on SWRH82B/SAE1080 of Xiangtan Steel

HE Dao-zhong;FU Yu-dong

2008, 24(04): 8-11,2. doi:

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Brittle fracture frequently occurs in drawing the high carbon wire rod SWRH82B/SAE1080 used for prestressed strand.The present paper analyzes causes to the breakdown of the wire rod such as the central shrinkage cavity and carbon segregation, surface transverse cracks, harmful structure of bulky pearlite and web shaped carbonide and puts forward a few relevant measures for improvement in the physical product quality and reduction of fracture rate of the wire rod including proper control of the casting temperature,drawing speed, intensity of secondary cooling as well as adjustment of the intensity of control rolling and accelerated cooling and optimization of the drawing parameters.

Production practice in reduction of internal cracks of small Billet by optimization of secondary cooling scheme

WANG Jian-xin;JIANG Guo-cai; LI Dong-shan ;ZHANG Huai-zhong;

2008, 24(04): 12-15,3. doi:

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Effects of the existing second cooling scheme on the Internal Cracks of 120mm×120mm Concasting Billet in No.1 Steel-making Plant Of Xinjiang bayi Iron & steel Corporation were evaluated and then by optimization of the second cooling scheme the effective results have been qained in reduction of the internal crack of the small billet .

A few important problems of electromagnetic stirring for continuous casting of billet

MAO Bin ;TAO Jin-Ming;JIANG Tao-xian

2008, 24(04): 16-20. doi:

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Based on the analysis of MEMS on-line Measurements,the present paper reveals two essential problems in EMS equipment: Core Saturation and quality of frequency Converter and points out some misunderstandings in EMS application through illustration of the Mechanism. It’s our strong desire that our elucidation on those problems can provide both the EMS manufacturers and users with some revelation. It must be emphasized that the electromagnetic torque should be seen as an important technical index of the EMS. This paper also puts forward a few problems for stainless steel EMS that need to be taken care of.

Effect of mould electromagnetic stirring on innter quality of heavy rail Steel bloom

ZHANG Gui-fang;CHEN Yong

2008, 24(04): 21-25. doi:

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The present paper analyzes the effect of different electromagnetic stirring intensities on the inner quality of the heavy rail steel bloom through comparison of the results out of different experiments. In the experiments 24 blocks of concasting bloom are used as the testing pieces and the stirring currents adopted are 250A, 350A,400A, 450A and 500A respectively. Results show that proportions of judging grade≤1.0 on the central segregation and central porosity of the bloom account to 95.83% and 87.50%,and the 500A current of electromagnetic stirring intensity determined in the research is a key technological parameter for improvement in the inner quality of heavy rail steel. Liquid phase convection at the solidifying front can be intensified due to the action of the electromagnetic force after implermentation of the mould electromagnetic stirring and at this time the intensified convection may further scour and rinse solidification front , and as the results the liquid flow at the solidification front inevitably leads to a mixture of the matrix with the liquid of the dual-phase and thus the concentration of the solute tends to be more homogeneous.

Research on non-metallic inclusions of high-pressure boiler steel

TANG Hai-yan;LI Jing-she;LIU Liang;GAO Jin-guo;WEN De-song;ZHANG Lu

2008, 24(04): 26-29. doi:

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In order to know the cleanliness of pressure vessel steel 12Cr1MoVG produced by EAF-LF/VD-CC route in Tianjin Pipe Corporation Ltd.,the quantity and changes of total oxygen, microinclusions and macroinclusions in the liquid steel in different processes were studied by the way of sampling systematically tracers and comprehensive analysis. The causes to form inclusions were analyzed and the improving measures were put forward.

Thermodynamic research on alloying of manganese in CrMn-Austensitic stainless steel refining process

ZHOU Shu-cai; REN Zheng-de; YANG Zhi-li;

2008, 24(04): 33-35. doi:

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The present paper theoretically analyzes and calculate the feasibility of the important steps of the CrMn-austensitic stainless steel refining process as well as the problems of carbon removal and Mn preservation in the later stage of converter refining using the dual-step method of “electrical arc furnace+ multi-functions converter” from the viewpoint of metallurgical thermodynamics. As the results a theoretical basis is provided for manganese alloying and process optimization the in the whole austensitic stainless steel refining process．

Study on mechanism of TiN formation and precipitation in 430 sainlesssteel

SHI Xiao-fang;CHENG Guo-guang

2008, 24(04): 36-39. doi:

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The paper theoretically analyzes the condition of titanium nitride (TiN) formation in 430 ferritic stainless steel according to the thermodynamics and kinetics. The results of calculation indicate that trace of nitrogen and titanium may cause formation of TiN in terms of thermodynamics. However,according to the theory of kinetics the TiN can only be nucleated and precipitated by means of very high concentration of nitrogen and titaium as well as other external nucleation force. The studies also indicate that the lower the temperature, the easier TiN forms and precipitates. In order to make the TiN smoothly form and precipitate, and not to grow up in the subsequent solidification process，it is necessary to control the TiN formation temperature in a certain appropriate degree in two–phase zone.

Mathematical simulation on fluid flowing and mixing

NI Bing;DI Zhan-xia;LUO Zhi-guo;ZOU Zong-shu

2008, 24(04): 40-42,5. doi:

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The molten steel flow field in a 100 ton ladle was simulated by the method of programming the users’self- defined function (UDF) on the base of FLUENT software. Results show that inclusions could be removed effectively with an argon flow rate of 0.1～0.2 Nm3/min when the nozzle is placed on 2/3R location from ladle bottom center. In view of a good compromise between the inclusion removal and the slag line protection it would be better to relocate the nozzle from 2/3R to 1/3R . The results show that by using the software FLUENT as a platform very complicated behavior of the hot metal flowing in the ladle can be very clearly depicted with less work load for programming and it can be used as a guide in the production.

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

CHEN Yang;ZHANG jiong-ming;WANG San-zhong

2008, 24(04): 43-46. doi:

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Using the wide slab caster mold of a specific steelmaking plant as prototype, the water model with 1：1 scale is established to investigate the effects of casting speed 、immersion depth、nozzle port angle、nozzle port area and other parameters on the flow field and surface flow fluctuation in the different wide slab caster mold. The processing parameters are optimized in order to reduce the slag entrainment in mold. The results show that with increase in the casting speed or width of mold,the surface fluctuation is prominently severe. And it’s proved that by adoption of deeper immersion depth and larger outlet area of the nozzle the surface fluctuation can be checked and the entrainment of slag avoided effectively.

Research and application of solidification and heat transfer for liquid steel

ZHU Li-guang;HAN Yi-hua;WANG Yong-hao

2008, 24(04): 47-51. doi:

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In order to adapt the high speed of the 2nd caster of Tangshan Stainless Steel Company, the mathematical model for heat transfer during solidification of steel in the mould of slab caster has been established in this paper. The finite element software，ANSYS，has been applied to simulate solidification process. The temperature distribution and growth history of solidification shell have been described under the high speed and the influence of each processing factor on the behavior of steel heat transfer and solidification analyzed and then the reasonable processing parameters proposed and applied into the conticaster. The on-site practice proves that steel-leakage accident has been reduce obviously eversince.

Discussion on bottom tuyere configuration optimization of top and bottom combined blown converters

blown converters

2008, 24(04): 52-55. doi:

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It is shown from the experiments for the bottom tuyere configuration optimization in combined blown converters that the bath stirring intensity can be enhanced by using a suitable number of bottom tuyeres and, especially by positioning those bottom tuyeres in an asymmetrical and integrated configuration. Application of such an asymmetrical and integrated bottom tuyere configuration in the 100t combined blown converter of Sanming Iron & Steel Co. is the first in the metallurgical sector of the Country and practical results show that all metallurgical parameters for the converter melting have been greatly improved..

Experimental study on the melting characteristic of dephosphorizing slag series

ZHOU Yun;WANG Xiang-lin;PENG Jun

2008, 24(04): 56-59. doi:

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The present paper mainly studied the melting performance of the dephosphorizing reagent for low chromium-containing hot metal as well as the influence of BaCO3 and the other constituents on the melting point and speed of the slag by way of the quadratic orthogonal regressive experiments . Experimental results show that the melting point of the flux of the Magnesium chromium brick composed mainly of 21.5%CaO-15%BaCO3-40%Fe2O3 -12.5%CaF2-5%Cr2O3 -6% is lower (1 170 ℃), and its melting time faster (3mins), so the flux can satisfy the demand of dephosphorization of low chromium-containing hot metal.

BP neural network-based prediction model for quenching degree control of 20CrMnTiH

LIN Jun ;LIAO JUN

2008, 24(04): 60-62. doi:

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A three level BP neural network prediction model has been built and the J9 top quench value for 20CrMnTiH predicted by analysis of the chemical compositions in the process of refining.The hitting rate of the report has reached 96% with the tolerance controlled within the limit of±3HRC .The cause to the deviation is also analyzed.

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