Steelmaking

Application and development of deep dephosphorization technology in top and bottom combination blown converters

2013, 29(4): 1-6,14. doi:

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Main dephosphorization processes with top and bottom combination blown converters in domestic steel plants involve singleslag process (for low carbon steel), new doubleslag process in one converter, duplux process in two converters. The parameters for dephosphorization are suitably lowering oxygen intensity, largely increasing bottom gas intensity, properly prolonging dephosphorization time, controlling temperature below the conversion temperature of phosphorus and carbon oxidation reactions, and suitably controlling basicity and T.Fe content in slag. The mass fraction of phosphorus range of 0.004 8 %～0.008 0 %or 0.01 %at end point can be achieved for low carbon or medium and high carbon steel, respectively. Obvious and deep dephosphorization results in top and bottom combination blown converters can be achieved.

Design innovation and production practice for steel-making process in CISC

2013, 29(4): 7-10,2. doi:

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New one-tank-system was used to connect the iron-making and steel-making in steel-making plant of Chongqing Iron and Steel Co.,Ltd.and the direct concatenation of continuous casting and hot rolling was carried out by hot charging process. The innovation design of without steam and without the railway network have been adopted. The high desulfurization rate can be achieved for the hot metal and thermal loss reduced by the short transport distance between blast furnace and KR desulfurization station. It is important of refining equipments, such as RH with dry vacuum pump, for producing clean steel. The slab stack yard and the produce time for the plate has been reduced through hot charging process. Since commissioning for more than two years, the logistics, energy flow and information flow are smooth and the variety and quality of steel plate are satisfied with customer requirements by continuous optimization and improvement for the process.

New hot metal desulfuration technology with complex powder injection in WISCO

2013, 29(4): 11-14. doi:

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The theory feasibility of hot metal new desulfurization process with passivated magnesiumfluidization CaO co-injection was studied. And through the optimization of process flow, parameters and transformation equipment, the process are used in industrial production of ultra-low sulphur steel. The results shows that, the ratio of the w(S) lower than 0.001 5 % in hot metal increases to more than 95 %,converter tapping w(S)≤0.004 % amounts to 99 % above.

Quality control practice of converter smelting GCr15 bearing steel

2013, 29(4): 15-18,2. doi:

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Panzhihua Steel ＆Vanadium Co.,Ltd. adopted “hot metal pretreatment→120 t top and bottom combined blown converter→LF→RH→billet, round billet continuous casting” technology product GCr15 bearing steel. The high titanium content and high oxygen activity in molten steel, pouring variable flow phenomenon occured in prodution. Through strengthen key point control of end point of converter steelmaking, LF, RH process and continuous casting protection casting, can stable production to meet the requirements of GB/T 18254—2002 of GCr15 bearing steel.

Smelting practice of TSMF166 high-nitrogen non-magnetic steel for drill collar

2013, 29(4): 19-21,4. doi:

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Smelting method with low carbon high manganese and nitrogen increasing through VOD and LF two techniques were developed by high nitrogen stainless steel TSMF166 smelting practice. Adjusting addition time of manganese alloy, using cheaper nitrogen instead of alloy nitride, during production of TSMF166 high-nitrogen non-magnetic steel for drill collar, control problems of carbon, nitrogen and manganese were solved. Smelting time of each procedure was shortened, such as K-OBM-S converter, VOD furnace and LF furnace. Cleanliness of steel was increased, production cost was decreased, and pollution problem because of addition of alloy nitride in LF was avoided completely. Finally, a new idea about nitrogen increasing through VOD and LF was proposed. This technique was economic and environmental, which was worthy to learned and spread in the steel industry.

Analysis and control on edge crack of medium and heavy plate of 45 steel

2013, 29(4): 22-25. doi:

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Based on the metallographic analysis of defective slab and normal slab of 45 steel medium and heavy plate the subsurface blowholes and corner transversal cracks of slab is the main reasons which cause the edge cracks of plate. By reducing the oxygen，nitrogen and aluminum content in liquid steel and adjusting secondary cooling schedule of slab continuous caster, the edge cracks of medium and heavy plate have been effectively controlled.

Ferrosilicon deoxidization process with low-cost for checker plate

2013, 29(4): 26-29. doi:

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In order to produce low-cost checker plate with ferrosilicon deoxidization process, converter slagtapping, deoxidation products activity and cleanness of molten steel were analyzed. In addition, under the practice of primary checker plate production with ferrosilicon instead of aluminium, modifying process of ladle slag, control of dexodation products and calculation of dexodation cost were researched as well. Ferrosilicon deoxidization process with lowcost for checker plate has been developed. The results show that SiO2 activity in slag is not more than 0.3, w(Mn)/w(Si) value is around 10 in molten steel, reduction of dexodation cost is about 6 yuan per ton of steel.

Analysis of influencing factor on desulfurization efficiency of complex powder injection

2013, 29(4): 30-32. doi:

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The influence of primary sulfur content of molten iron, temperature, desulfurization size, mixing efficiency, fluidity of slag, slag-removing operation on complex powder injection desulphurization efficiency are analyzed from raw materials condition, kinetics condition and slag-removing efficiency three aspects. Some proposals are provided to improve the desulfurization efficiency in the steel-making plant.

Based on the numerical simulation optimization study of the oxygen lance jet of 120 t converter

2013, 29(4): 33-36. doi:

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Oxygen jet and threedimensional mathematical model for a 120 t converter of Sansteel MinGuang Co.,Ltd.,Fujian has been established with CFD software. The simulation results show that，four-hole top lance is better than three-hole top lance in dephosphorization and melting slag, and fourhole lance makes impact area and effects of dephosphorization good for steelmaking. Lance designed Ma=2.03is better than Lance designed Ma=1.98in melting slag and decarbonization. To test the simulation results, the new oxygen lance applied to two 120 t converters of Sansteel MinGuang. The results showed that the new lances are good at dephosphorization, and control temperature well. To achieve the purpose of dephosphorization at first and then decarbonization for temperature rising.

Research on manganese ore smelting reduction based on double slag process in BOF

2013, 29(4): 37-40. doi:

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In order to find a way to increase the rate of manganese yield in manganese ore smelting reduction based on double slag process in BOF, the basic thermodynamic of the process was analyzed and preliminary results were got, experiments including slagmolten steel reaction in lab and steelmaking simulation in pilot plant were done, and all the results above were proved to be valid in industrial scale experiment in general steelmaking factory of WISCO. The final results shows that 35 %～45 % manganese yield could be got with some given conditions in traditional BOF process base on double slag technology, which can benefit to efficiency of BOF process as well as less carbon emissions as a whole.

Influence of solid particles on the viscosity of BOF slag

2013, 29(4): 41-43,4. doi:

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The effect of solid particles on BOF slag viscosity was invesigated by high temperature experiment. In high temperature experiment, the crystallization of Ca2SiO4and MgO from liquid slag was adopted. Experimental results indicate the viscosity of two phase fluid increases significantly with volume faction of crystallization. In addition, experimental data were used to examine the applicability of the existing models. Roscoe, Ruiz and Zholkov models can give good predictions for present experiment（relative error is less than 5.4 %）. The work gives a good guidance for the prediction of slag containing solid particles.

Analysis on behavior of carbon and sulfur of silicon steel in RH process

2013, 29(4): 44-48. doi:

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The present article analyzes the principle of decarburization and desulfurization in refining the cold rolled silicon steelin the 80 t RH in No.2 Steelmaking Plant of Taiyuan Iron & Steel (Group) Corp., and its influencing factors. It’s determined that the decarburization effect can be achieved by properly controlling the cabon and oxygen contents in the hot metal coming into the RH station, enlarging the inner diameter of snorkel and adopting the fast evacuation method. In the meanwhile the desulfurization rate in RH can be raised by reducing FeO and MnO contents in the top slag and ensuring the circulation time after charging the desulfuizer.

Study on inclusion behavior in X80 pipeline steel during secondary refining process

2013, 29(4): 49-52,6. doi:

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The change of nonmetallic inclusions in X80 pipeline steel produced by a domestic plant has been studied. With adding aluminum during BOF tapping for intensifying deoxidation, the most of inclusions were Al2O3accompanied a little MgO. High basicity and reducibility refining slag were used in LF refining process, the Al2O3 inclusions in steel were transformed to calcium aluminates and CaO-MgO-Al2O3 complex compound inclusions whose average composition was close to low melting point zone. After RH process, the content of Al2O3 and MgO in inclusions were decreased while the content of CaO was increased, the distribution of inclusion composition was dispersed. After calcium treatment, the proportion of CaO-MgO-Al2O3complex compound inclusions were decreased, while the proportion of CaO and CaS inclusions were increased, the average composition was far from low melting point zone, the metallurgical effect of high quality pipeline steel was achieved.

Thermodynamics research of inclusion precipitation behavior in 45 steel

2013, 29(4): 53-56,6. doi:

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According to the oxide metallurgy technology, based on the inclusion that has a good induced intragranular ferrite nuclear ability, and introduces the development that the thermodynamics and dynamics of the most effective induced nucleation inclusion, systematically analyses MnS, VC, VN, V (C, N) precipitating thermodynamic conditions in the Ti-Al-O-N system, thus, the conclusion is drawn inclusions precipitate opportunity. And theoretical analysis is verified by experiment results, for inclusion precipitation through temperature control provides the basis for size, number and distribution.

Influence of big stroke liquid core reduction on microstructure of slab

2013, 29(4): 57-61. doi:

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Through the industrial experiments on the thin slab continuous casting and rolling production line（CSP） for the big stroke liquid core reduction in Masteel. The relationship between the microstructure of the slab and the value of liquid core reduction for low carbon steel, medium carbon steel and silicon steel have been researched when the maximum value of liquid core reduction increased to 35 mm from the original design of 20 mm. The results show that，within the scope of the trials study ,the value of the liquid core reduction have no significantly influence on internal cracks and triangle cracks, the big stroke liquid core reduction can improve the central segregation, the degree of center segregation is improved with increasing reduction, especially for medium carbon steel Q235B and silicon steel MGW1300.

Application and thermodynamics analysis on alumina and titaniainclusion formation in welding steel containing titanium

2013, 29(4): 62-66. doi:

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Thermodynamics method was adopted to calculate the forming condition of alumina and titania inclusion in welding steel containing titanium. The characteristic of the inclusion was analyzed by SEM. It was showed that the critical condition of the TiO₂-Al₂O₃ and Ti₂O₃-Al₂O₃competitive oxidation was [%Ti]/[%Al]^4/3=84.49 and [%Ti]/[%Al]=7.46 respectively. When [%Ti]/[%Al]^4/3<84.49 and [%Ti]/[%Al]<7.46, Al₂O₃ formation was preferential; on the other hand, Ti₂O₃ or TiO₂ formed. The inclusion was changed from Al₂O₃ to Al₂O₃-TiOx and to TiOx successively when Alt content decreased from 0.0360% to 0.0046%, which agreed with the result of calculation. By controlling the w(Al_t)<0.0050% and soft blowing parameters, Al₂O₃ was effectively reduced and continuous casting heats increased to 6 heats.

Application and research on solid core pure calcium line in LF refining process

2013, 29(4): 67-70. doi:

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In order to improve the effect of calcium treatment, solid core pure calcium line test was applicated in Shouqin 100 t LF. Studies show that，the use of solid core pure calcium line for calcium treatment has good metallurgical effect.Through the test found that proper feed speed, higher liquid steel temperature, high aluminum content can improve the yield of calcium.

Application practice of refractory material of 250 t converter skateboard type slag blocking mechanism in Baosteel

2013, 29(4): 71-74,7. doi:

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By means of test and combination site actual, the service life of the internal and external refractory material of converter skateboard type slag blocking mechanism was statisticed and analysised. And the components of internal refractory material have been improved, to further improve the skateboard slag online service life. It provides a favorable support for reducing workload of the offline maintenance and online replacement times in skateboard slag blocking, and have good promotion value for domestic largescale mills using of converter skateboard type slag blocking method.

Selecting strategy of RH ladle lifting system under different conditions

2013, 29(4): 75-78. doi:

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Various types of RH ladle lifting are introduced，according to different forms of actuating mechanism, they are divided into hydraulic form and electrical form; according to makeup of equipment, they are divided into single hydraulic cylinder lifting, double hydraulic cylinders lifting, winding lifting and four hydraulic cylinders lifting. Some analysis through comparison are putted forward as well as some basic principles which need to be followed during selection of RH ladle lifting type is summarized. It will be help to deepen the understanding of RH process and provide reference for steel enterprises' design and mode selection.

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