炉外精炼工艺流程.doc

Hunan University of Technology School of Metallurgical Engineering 102 Zhang Tianshan 10495200221Refining processIntroductionWith the development of modern scientific technology and industrial and agricultural requirements of steel quality improvement, steel has been widely used in secondary refining process, it has become an essential part of modern steelmaking process. Because of this technology can improve the steel-making equipment production capacity, improve the quality of steel,reduce energy consumption, reduce refractories, energy and iron alloy consumption, therefore, refining technology has become one of the worldsiron and steel metallurgy development direction. It is necessary to study forrefining problems and development direction of technical problems.1 Development course and the present situation of domestic and international 1refining technologyWith the development of steelmaking technology, refining outside the furnacehas occupied an important position in the modern iron and steel production,the traditional production process (blast furnace, steel furnace (EAF orfurnace), casting), has been a new process (blast furnace, molten iron pretreatment, steelmaking, refining, continuous casting) replaced. Has become the main process of large-scale iron and steel enterprise production at home and abroad, especially in the field of special steel, refining and continuous casting technology matures. The refining process plays a crucial role in the whole process, hand through this process can improve the purity of steel, removal of harmful impurities, micro alloying and inclusion modification;on the other hand, refining is a buffer unit, is conducive to the balance of the continuous casting production.Japan in the nineteen seventies in order to reduce the cost of steelmaking,improve the purity and quality of steel, will take the lead in refining technologyused in special steel production in Western Europe, then the iron and steel enterprises also added to the promotion and application of this technology in the ranks of the. According to reports, Japan as early as 1985 refining rate reached 65.9%, rising to 73.4% in 1989, the special steel refining rate reached 94%, the new EAF minimill 100% using the secondary refining technology. 80 years of continuous casting technology is developing rapidly,the original furnace is difficult to satisfy the requirements of continuous castingtechnology, promotes the development of the secondary refining technology,until 1990 the major industrial countries in the world has more than 1000 Taiwan (sets) refining equipment.In the early nineteen fifties end, 60 time metaphase in steelmaking productionwith high basicity slag in tapping process desulfurization smelting bearing steelladle degassing, static preliminary refining technology, but no refiningequipment. The mid 60s to 70s of some special steel enterprises (Daye,Wuhan Iron and steel) to introduce a number of vacuum refining device. In the 80s developed by refining equipment development gradually put into use(such as LF furnace, powder, mixing equipment), Heilongjiang Provincial Metallurgical Research Institute jointly developed a wire feeding machine, wiremachine and alloy cored wire, assistive technology improve the refiningtechnology. This technology is now very mature, the secondary refiningtechnology as the core of the Trinity short flow process is widely used in the domestic iron and steel enterprises, and achieved very good results. The primary smelting (electric stove or furnace), refining, continuous casting, atypical short technological process of modernization.2 refining characteristics and functions of TechnologyRefining refers to the process of smelting in the ladle, the vacuum, argon stirring, heating temperature, wire feeding powder, micro alloying technologyin different combinations, tapping to remove oxide slag in ladle, re reductive slag, keep the package in reducing atmosphere. Refining outside the furnaceis designed to reduce the steel of C, P, S, O, H, N, and other elements in steelcontent, in order to avoid segregation, white spots, large inclusion, reduced the tensile strength, toughness, fatigue strength, crack resistance and otherproperties of the steel. These work only in a refining furnace, its features and functions are as follows:1）You can change the metallurgical reaction conditions. In the steel-makingdeoxidation reaction product, decarburization, Degas for gas, refining can beperformed under vacuum conditions, the reaction was generally positive,working pressure 50Pa, suitable for molten steel degassing.2) can accelerate the mass transfer velocity of molten pool. Liquid phase mass transfer rate determining metallurgical reaction speed, refining processusing a variety of mixing form (gas stirring, electromagnetic stirring, stirring the melt) within the system flow, heat transfer, mass transfer in the melt during acceleration, achieve mixed objective.3) can increase the area of the slag steel reaction. Various refining equipment are mixing device, mixing process can make the steel slag emulsifying, alloy,steel slag with bubble rise occurred in the process of melting, melting,polymerization reaction, usually the slag steel reaction area 1 tons of steelliquid is 0.8 1.3mm2, when the amount of slag as the original 6%, steel slagemulsion formed after the radius 0.3mm of the slag drop, the reaction interface will increase 1000 times. Modification treatment of micro alloying,refining effect is increased by using this principle.4) in the furnace (BOF) and continuous casting buffer function betweenflexibility, refining furnace, the operation time, temperature control is morecoordination, to form a more smooth and continuous casting production process.3 refining the application in production has been recognized and widely usedoutside furnace refining method: LF method, RH method, VOD method.3.1 LF (ladle furnace method)It is 1971 by the present Japanese Datong steel company, using arc heating,ladle bottom blowing argon stirring.3.1.1The advantages of technology 1) arc heating and high thermal efficiency, heating rate, temperature control accuracy of 5 ;2) with stirring and alloying function, argon stirring is easy to achieve a narrow range of alloy composition control, improve the stability of the products; 3) and less investment in equipment, refining and low cost, suitable for the production of ultra low sulfur steel, ultra low oxygen steel.3.1.2Production process key points of LF methodHeating and temperature control of LF by arc heating, high thermal efficiency,the average temperature of molten steel at 1 power consumption of 0.5 0.8kW h, LF heating rate depends on the power supply to power ratio(kVA/t), melting loss index and power than the power depends on the ladlerefractories. By using submerged arc foaming slag technology, thermal radiation loss can be reduced by arc, thermal efficiency is 10% 15% higher,end temperature accuracy 5 . 2) using white slag refining process.Controlling slag amount in 5kg/t, generally use the Al2O3-CaO-SiO2 system slag, slag basicity R 3, in order to avoid RE oxide slag. To avoid the liquid steel exposed to argon stirring time.Alloy tuning and narrow composition range control. According to the testreport, the use of alloy cored wire technology can improve the metal recovery rate, recovery of gear of titanium in steel to achieve an average rate of 87.9%,the boron recovery rate was 64.3%, the feeding carbon line recovery rate as high as 90%, ZG30CrMnMoRE rare earth wire feeding rare earth recoveryrate reached 68%, higher recovery rate can be achieved with narrowcomposition control.3.1.3Application of LF method in production practiceIn 2000 June, casting workshop in AISC No.1 steelmaking plant formally put into production, refining equipment consists of two LF ladle refining furnace,liquid steel processing 2000000 T; a VD steel vacuum treatment device,annual processing 800000 t steel. LF furnace maximum heating rate was 4 ,LF furnace average processing cycle 28min; treatment effect: the averageH 0.0002%; the lowest H 0.0001%. The existing heavy rail productionplant in China (Panzhihua Iron and steel, Baotou Steel, Anshan Iron and steeland Wuhan Iron and steel production line of typical) as follows: LD LF VD WF CC, ladle to ladle crane LF processing line after, quick joints by artificial on ladle bottom argon blowing, the molten steel composition andtemperature requirements of the degree to determine the amount of material(including wire feeding) heavy rail steel with high carbon content, so it wasimportant, tapping liquid steel carbon content control for 0.2% 0.3% (WT),stove cementation to 0.60% 0.65% (WT), in LF furnace to increase 0.10% 0.15% (WT). Upper limit of carbon to the standard component, after treated by VD can meet the requirements of its components.3.2 RH (vacuum degassing method) this method is invented in Germany in 1958, its basic principle is to use the bubble will improve to the molten steelvacuum degassing, decarbonization, and then return to the ladle.3.2.1Advantages of RH methodThe reaction speed. Vacuum degassing cycle is short, generally 10 minutescan complete degassing operation, 5 minutes can complete the alloying andtemperature uniformity, and can be used in conjunction with the converter.High reaction efficiency. Steel reaction directly in the vacuum chamber, the steel can reach H 1 10-6, N 25 10-6, C 10 10-6, super clean steel.For oxygen decarburization and two combustion thermal compensation,reduce refining process of temperature drop.3.2.2 RH process parameters1) RH circulation. Cycle refers to the amount of unit time through theascending pipe or falling steel water pipe, the unit is t/min. The computational formula for the information given is: Q=0.002 Du1.5 G0.33, type: Q - circular flow, t/min; Du - rising pipe diameter, cm; G - rising pipe and argon flow rate, L/min.2) cycle factor. He is in RH process by molten steel and processing of vacuum chamber ratio, the formula is: =w t/v type: - circular factor, time; W - circulation, t/min; t - cycle time, min; V - ladle capacity, t. 3) the relationship between the intensity of oxygen supply and carbon content. In the RH oxygen can improve the decarburization rate, namely RH-OB method. When C/O0.66 mass transfer rate of oxygen decarburization rate in ladle is decided, the calculation formula is as follows: QO2=27.3 Q C type: QO2 - oxygen intensity, Nm3/min; Q - circulation, molten steel t/min; C - the amount of carbon, Nm3/t. Application of 3.2.3 RH method in production practiceJapans Shanyang steel LF and RH with the production of bearing steelproduction line of EF-LF-RH-CC bearing steel, steel in total oxygen contentreached 5.8 10-6. LF-RH method using LF furnace to molten steeltemperature, using the LF mixing and slag refining function reduction refining,is molten steel desulphurization and pre deoxidation of molten steel, and theninto the RH for dehydrogenation and two deoxy. After such treatment improvesthe cleanliness of molten steel, and the temperature of molten steel tocontinuous casting temperature.Baoshan Iron and steel refining equipment RH-OB, ladle injection device, CAS refining device, an ideal metallurgical effect of RH-OB, dehydrogenation rate is 50% 70%, nitrogen removal rate is 20% 40%, under normal circumstances, after treated with RH-OB, H 2.5 10-6, C 30 10-6,removing inclusions can generally reach 70% non steel, steel total oxygen in 25 10-6, and in RH alloy treatment can improve the yield and the control precision alloy, precision control of C, Si, Mn can reach 0.01%, aluminum precision can reach 1.5 10-3, obtained better refining effect.3.3 VOD (vacuum tank ladle oxygen blowing gas method)Characteristics of VOD 3.3.1 VOD is the first application of Germany in 1965,it is the ladle into the vacuum tank from top oxygen blowing lance to ladledecarburization, also from the ladle bottom argon stirring up. This method is suitable for the production of ultra low carbon stainless steel, the chromium tocarbon, can be used in conjunction with the converter. He has the advantage of the thermodynamics and kinetics of the necessary low carbon stainless steel smelting conditions - high temperature, vacuum, stirring.3.3.2 Application of VOD method in production practiceThe early nineteen ninties, Shanghai Dalong forging factory from GermanyLEYBOLD (LEYBOLD) key equipment and technology of software companies to import 1 sets of 15tVODC. The process of refining molten steel by VODCrefining furnace, refining extra low carbon steel, low alloy steel and carbon steel, the metallurgical effect very good, reduce the non metallic inclusions in steel, hydrogen content is less than 3 10-6 oxygen content is less than 6.5 10-6, stainless steel chrome recovery rate was 98% 99% excellent performance, with the refined steel. VODC refining technology is mature, easy control, adapt to the small and medium-sized steel mills and steel plant of steel, small tonnage refining production needs, the development of steel industry production will play a large role, with broad prospects for development 10.Fushun Special Steel Co., Ltd. 30tVOD furnace, using EAF+VOD technologyfor stainless steel refining, can make H 2.58 10-6, TO 41.9 10-6,chromium recovery rate reached 99.5%, desulfurization rate of 64.2%, TO refining of high carbon chromium bearing steel 12.13 x 10-6.4 the development of the secondary refining technology for furnace problems and development direction to solve the refining technology has been used for 40 years, to improve the purity of steel, precise control of composition andrefinement of the organizational structure have played an important role, so that smelting cost is greatly reduced, while improving the quality andperformance of the steel. But there are some problems in the development process, need to be solved, make this technology more perfect.Intelligent control of refining process outside of the furnace, according to thevarious technical parameters of incoming molten steel, the use of information technology, the best scheme refining process, and the refining process iscontrolled by computer. Refining station equipped with rapid analysis equipment, realize the data network, reduce the heat stop waiting time.2) furnace processing equipment will achieve the multi function. In steelrefining slag washing equipment, refining, vacuum metallurgy, mixing process and heating temperature control functions are combined, realize the refining,in order to meet the social needs of ultra clean steel production.3) the quality of basic refractories development of high purity, high density,high strength, in order to adapt to different needs refining furnace, stability,pay attention to product quality. The use of refractory conditions should beconsistent with the slag, reduce erosion rate. To form the supporting materialsof different levels according to the actual situation of refining equipment,research and development of heat preservation and repair technology,improve the service life of the furnace lining.4) to reduce pollution emissions of the refining process, refining processproduces large amounts of emissions, including SO2, Pb, metal oxides,suspended particles, containing solid suspended matter, Pb, Zn in the vacuum degassing cooling water, these pollutants to be related to treatment by theenterprise, the pollution degree of reduced to meet emissions standards and then discharged, strengthen the consciousness of environmental protection.5 ConclusionRefining technology is an advanced technology to improve product quality,reduce production cost, is an important part of modern steelmaking processindispensable, precise control, chemical composition and temperature ofinclusions are excluded, the top slag reduction and S, Ca, inclusion morphology control, removal of H, O, C, S and other impurities, vacuumdegassing metallurgical function. Only by strengthening the each function, canplay the advantages of refining outside the furnace, the production of high quality and pure steel.湖南工业大学 冶金工程学院 102 张天山 10495200221炉外精炼工艺流程引言 随着现代科学技术的发展和工农业对钢材质量要求的提高,钢厂普遍采用了炉外精炼工艺流程,它已成为现代炼钢工艺中不可缺少的重要环节。由于这种技术可以提高炼钢设备的生产能力,改善钢材质量,降低能耗,减少耐材、能源和铁合金消耗,因此,炉外精炼技术已成为当今世界钢铁冶金发展的方向。对于炉外精炼技术存在的问题及发展方向有必要进行探讨。 1 国内外炉外精炼技术的发展历程和现状 随着炼钢技术的不断进步,炉外精炼在现代钢铁生产中已经占有重要地位,传统的生产流程(高炉炼钢炉(电炉或转炉)铸锭),已逐步被新的流程(高炉铁水预处理炼钢炉炉外精炼连铸)所代替。已成为国内外大型钢铁企业生产的主要工艺流程,尤其在特殊钢领域,精炼和连铸技术发展得日趋成熟。精炼工序在整个流程中起到至关重要的作用,一方面通过这道工序可以提高钢的纯净度、去除有害夹杂、进行微合金化和夹杂物变性处理;另一方面,精炼又是一个缓冲环节,有利于连铸生产均衡地进行。 日本在20世纪70年代为了降低炼钢成本,提高钢的纯净度和质量,率先将炉外精炼技术应用于特殊钢生产中,随后西欧的钢铁企业也加入到推广和使用这项技术的行列中。据资料报道,日本早在1985年精炼率达到65.9%,1989年上升到73.4%,特殊钢的精炼率达到94%,新建电炉短流程钢厂100%采用炉外精炼技术。80年代连铸技术发展迅速,原有的炼钢炉难以满足连铸的技术要求,更加促进了炉外精炼技术的发展,到1990年为止世界各主要工业国家拥有1000多台(套)炉外精炼设备。 我国早在20世纪50年代末,60年代中期就在炼钢生产中采用高碱度合成渣在出钢过程中脱硫冶炼轴承钢、钢包静态脱气等初步精炼技术,但没有精炼的装备。60年代中期至70年代有些特钢企业(大冶、武钢等)引进一批真空精炼设备。80年代我国自行研制开发的精炼设备逐渐投入使用(如LF炉、喷粉、搅拌设备),黑龙江省冶金研究所等单位联合研制开发了喂线机、包芯线机和合金芯线,完善了炉外精炼技术的辅助技术。现在这项技术已经非常成熟,以炉外精炼技术为核心的“三位一体”短流程工艺广泛应用于国内各钢铁企业,取得了很好的效果。初炼(电炉或转炉)精炼连铸,成了现代化典型的工艺短流程。 2 炉外精炼技术的特点与功能 炉外精炼是指在钢包中进行冶炼的过程,是将真空处理、吹氩搅拌、加热控温、喂线喷粉、微合金化等技术以不同形式组合起来,出钢前尽量除去氧化渣,在钢包内重新造还原渣,保持包内还原性气氛。炉外精炼的目的是降低钢中的C、P、S、O、H、N、等元素在钢中的含量,以免产生偏析、白点、大颗粒夹杂物,降低钢的抗拉强度、韧性、疲劳强度、抗裂性等性能。这些工作只有在精炼炉上进行,其特点与功能如下: 1) 可以改变冶金反应条件。炼钢中脱氧、脱碳、脱气的反应产物为气体,精炼可以在真空条件下进行,有利于反应的正向进行,通常工作压力50Pa,适于对钢液脱气。 2) 可以加快熔池的传质速度。液相传质速度决定冶金反应速度的快慢,精炼过程采用多种搅拌形式(气体搅拌、电磁搅拌、机械搅拌)使系统内的熔体产生流动,加速熔体内传热、传质的过程,达到混合均匀的目的。 3) 可以增大渣钢反应的面积。各种精炼设备均有搅拌装置,搅拌过程中可以使钢渣乳化,合金、钢渣随气泡上浮过程中发生熔化、熔解、聚合反应,通常1吨钢液的渣