Steelmaking

High-carbon steel production process and quality analysis

2009, 25(04): 1-4. doi:

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The present paper introduces the production of high carbon steel by the technological process of Converter-LF-Conticaster, analyses the characteristics of the technology and quality and generalizes the essential points of the processs in Chonggang .It’s concluded that the crucial and most difficult points in production of the high carbon steel is to control the carbon segregation and the shape and content of the inclusions in molten steel.

Cold modeling experiment of 100 t LF bottom blowing processoptimization and Its application

2009, 25(04): 5-8. doi:

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Positions of two bottom tuyeres and parameters of bottom blowing process of 100t LF were optimized in cold modeling experiments by measuring mixing time. Desulfurization rate was improved by 15.5% by optimizing the process parameters in production. The optimum position of the single bottom tuyere and its bottom gas blowing parameters were determined. The research results could provide a base for further improvement of the LF.

Study on behavior of inclusions in Ti-IF Steel

2009, 25(04): 9-12. doi:

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In light of the inclusion behavior of Ti-IF steel in a specofic iron & steel works in China the present paper studies the law of evolution of the inclusions as well as the type, size and distribution of the lnclusions in the slab and the large grain size inclusions and analyzes the origin of various inclusions and puts forward measures to further reduce inclusions and improve the cleanliness of the slab of the Ti-IF steel.

Technical characteristics and production practice of combi-Caster

2009, 25(04): 13-15. doi:

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In this paper, the main technical characteristics and production practice of the combi-caster are introduced and production practice shows that the technology and equipments of the combi- caster of Xiangtan Iron & Steel Co., Ltd can fully satisfy the production and process requirements of the slab and rectangle slab. By optimizing the processing parameters the object of high productivity, high quality and high efficiency can be achieved.

Effect of MgO content on desulphurization of CaO-Al2O3-SiO2-MgO slag

2009, 25(04): 16-19. doi:

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The effect of different MgO content on the sulfide content of the CaO-Al2O3-SiO2-MgO slag series as well as on the sulfur equilibrium distribution with steel of 0.03%[Al] and 1600℃ are studied by Factsage software and KTH model. The results show the sulfur equilibrium distribution is up to 500 with the slag compositions of MgO<8%，CaO,54%～59%，Al2O3,25%～30%，SiO2,6%～10% and as the results the requirements of making super low sulfur steel can be satisfied.

Study on optimization of steelmaking process for GCr15 bearing steel bloom

2009, 25(04): 20-23. doi:

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One of the key factors to improve the bloom quality is the cleanliness of steel. Appropriate selection of the steel-making process as well as the pre-oxidizer, final deoxidizer and refining slag and their compositions will directly affect the the cleanliness of liquid steel and the quality of the bloom. In view of the deficiency of the smelting and refining processes of the GCr15 bearing steel previously implemented an optimized scheme was put forward and the industrial scale experiment carried out promptly and as the results the smelting and refining processes of the GCr15 bearing steel were optimized and the cleanliness of the liquid steel prominently improved.

Analysis on the cause of ladle slag bonding in MEIGANG and Counter- measures

2009, 25(04): 24-26. doi:

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In light of the problem of ladle slag bonding in MEISHAN Steel the chemical compositions of the converter slag of the Al deoxidized steel, Al-Si deoxidized steel, the ladle top slag and the built up elements on the wall of ladle as well as the phase of the substance for the used ladle firebrick were analyzed. Results indicate that the pattern of deoxidation, the conditions of the ladle and the temperature holding agent are primary factors affecting the slag bonding. Very satisfactory results have already been achieved since adoption of the appropriate counter measures.

Experimental study on alkali slag containing dephosphorizer for hot metal pretreatment

2009, 25(04): 27-30. doi:

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The influence of CaCl2、CaF2 and basicity on dephosphorization was investigated.The experiments of dephosphorization of hot metal by using alkali slag and fluorite were performed in the lab.The results show that the dephosphorization effect using both of CaCl2 and CaF2 is better than using either of them exclusively. When alkali slag is used in substitution of CaCl2 in hot metal dephosphorization R=2 and When the mass fraction of the dephosphorizer addition comes up to14.8 % of the total alkali slag content and the CaF2 amounts to5.99 % the dephosphorization rate reaches 86 %. In addition, the melting point can be lowered and the dephosphorization rate raised by adding BaCO3 into the alkali dephosphorizer..

Study on melting properties of nickel and chromium containing desilicification flux and dephosphorization flux

2009, 25(04): 31-34，4. doi:

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In order to utilize Cr-and-Ni bearing rolling scales produced in stainless steel works in the desilicification and dephosphorization process and recycle valuable metals, melting experiments of desilicification and dephosphorizing agents and dephosphorization experiments of hot metal were carried out with dephosphorization fluxes of various compositions prepared with various proportion of Cr-and-Ni bearing rolling scales instead of sintering ore and then observed by the scanning electronic microscope. The results show that by proper adjustment of the proportion of the desilicifier and dephosphorizer, the Cr-and-Ni bearing rolling scales can be completely or partially substituted for iron scale and sinter used in desilicification and dephosphorization of hot metal.

Investigations in non-metallic inclusions modification effects of feeding SiCa wire in steel

2009, 25(04): 35-37，7. doi:

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The effect of calcium treatment in the current process of pipeline steel production in one specific Iron and Steel Group Co. has been studied in detail from the view point of inclusion size and composition change before and after calcium treatment in VD as well as from that of the oxide and sulfide modification effect. The results indicate that after calcium treatment in VD, the size of nonmetallic inclusions was decreased further and the type of inclusions changed either. The brittle Al2O3 inclusions and harmful MnS inclusions along boundaries were all modified in some extent. However, the oxide and sulfide inclusions were not modified absolutely.

Study on LF slag recycling use for desulphurization

2009, 25(04): 38-41. doi:

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Based on the analysis of the typical compositions of LF slag, recycling use of the LF slag for desulphurization is studied. The influence of initial (S) content, initial [S] content, as well as initial （Al2O3）on desulphurization is discussed and verified with test. It is found that desulphurization is possible with the recycled LF slag when dissolved [Al] at the level of 0.025 %-0.033 %. The desulphurization rate will decrease distinctly due to the the increase of sulphur content in the carry-over slag when initial (S) is more than 0.61%. The influence of （Al2O3）content is not very evident when it is below 25 %. With partly recycling of LF slag, desulphurization result can be guaranteed in practice.

Effect of secondary dendritic arm spacing on center carbon segregation of slab

2009, 25(04): 42-45. doi:

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Effects of different continuous casting processing parameters on the secondary dendritic arm spacing was determined by measuring the secondary dendritic arm spacing under the different working conditions such as the drawing speed, the cooling rate of the secondary cooling water and the over heat extent of the molten steel in production of the1900mmx250mm slab in Xinggang. Results show that the larger the secondary arm spacing, the higher the permeability and the more serious, the central segregation of carbon.

Mathematical model of decarburization in RH-TB refining process

2009, 25(04): 46-48，6. doi:

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A mathematical model of decarburization in RH-TB refining process was developed based on the theory of metallurgical thermodynamics and macro kinetics and at the same time the effect of initial carbon content, initial oxygen content and inner diameter of the dipping tube on decarburization process was analyzed. An out-line data base of mathematical model of decarburization in RH-TB refining process was established by utilizing the Microsoft Visual.Basic.net software and Microsoft SQL Server 2000 database software. The actual manufacturing data in RH-TB process was adopted to out-line check and examine the model and in review of the RH-TB process for 121 heats of IF steel the heats of the end-point liquid steel with w(C) error controlled within the limit of 0.001% amounted to 80%.

Research on thermal status of 300 ton ladle in the Process of Steel-making and continues casting

2009, 25(04): 49-53. doi:

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The thermal status of the ladle in the process of steel-making-refining-continues casting was tested and the distribution of the lining temperature and the law of the temperature variation in each and every turn-over phase of the ladle studied. The practical results show that the heat was obviously absorbed and stored in ladle lining in the first and second turn-over phases of the ladle and therefore the thermal compensation should be considered in those periods Howevr in the third and fourth phases of the ladle, the temperature in every points of the ladle lining changed smoothly. It shows that from the beginning of the 4th phase the change of the ladle lining was held in a recycling process of dynamic equilibrium.

Effect of cooling rate on the formation of acicular ferrite in Ti deoxidized steel

2009, 25(04): 54-57. doi:

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The microstructures obtained at different cooling rates were studied in the Ti deoxidized steel and the chemical composition was also analyzed by energy dispersive X-ray spectroscopy. The result shows that at the cooling rate of 8℃/s to 15℃/s, the acicular ferrites are formed within a temperature range of 500℃ to 800℃.The Ti-Al inclusions can induce nucleation of acicular ferrite and sympathetic nucleation as well, which make the acicular ferrite in steel interlocked and grains refined apparently.

Study on macro inclusions in 30CrMo gas cylinder steel

2009, 25(04): 58-60. doi:

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The variation of the size, quantity, morphology and chemical compositions as well as the origin of the macro inclusions of the 30CrMo gas cylinder steel produced by the EAF-LF-VD-CC processing route in the No.2 Steel Plant of Tianjin Pipe Corporation Ltd are analyzed and studied by way of overall flow sampling, rare earth oxide tracing and comprehensive analysis.Results show that reoxidation severely occurs in the tundish and the macro inclusions in the round billet are mainly composed of CaO-Al2O3-MgO、CaO-Al2O3、Al2O3-（Ca，Mn）S、Al2O3, which originate from the deoxidation produce, erosion caused peeling off of the ladle lining and slag entrainment in ladle and mold.

Study on mechanical properties of boron bearing low carbon micro-alloying cold heading steel

2009, 25(04): 61-64. doi:

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The low carbon boron bearing Nb and V micro-alloying cold heading steel has been trial-produced in laboratory. The microstructure and mechanical properties of the testing steels have also been studied contrastively. The results indicate that a proper amount of Nb、V in steel can refine the ferrite grain of the boron steel and enhance its tensile strength obviously, and the effect of boron bearing Nb and V composite micro-alloying steel is the best and next best is the boron bearing V and Nb steel. Analysis shows that the main function of Nb and V micro-alloying is assumed to refine the grain and enhance deposition.

Research on dimension decrement-based alloy charging intelligent prediction model

2009, 25(04): 65-67，7. doi:

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Since the alloy charging prediction model is used as an very important processing model for the steel refinement process its accuracy will play a very important role in further automation of the alloy charging and steel refinement processes. An alloy charging intelligent prediction model has been established on the bases of real data in combination of dimension decrement with the RBF nerve network. The result shows that the alloy charging model is of better predictive performance after dimension decrement

Study of Stainless Steel Produced with Twin Roll Strip Casting Process

2009, 25(04): 68-72. doi:

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Stainless steel is one of the important steel grades that can be produced with twin roll thin strip casting process. The present paper summarizes the classification and performance of the stainless steel and briefly recommends several modes of its production and discusses the technological key points and difficulties on stainless steel production with twin roll thin strip casting in detail.

Discussion on necessity of hot metal full pretreatment

2009, 25(04): 73-77. doi:

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The evolution of the hot metal pretreatment functions is analyzed and it’s considered that actual function of this process has already overpassed its originally designed limit of quality control and evolved step by step into an adjustor for coordinating and buffering the quality and energy in between processes. The necessity of “tri-de” for full hot metal is elaborated from six aspects and it’s pointed out that development of a new mode of “tri-de” of full hot metal in a large scale integrated steel work means to establish a platform for production of the clean steels high efficiently and cost-effectively and it’s also an inevitable road for strengthening the competitiveness of the products and pushing forward the development of China’s iron and steel industry in a high efficient way.

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