导电结晶器电渣重熔中非金属夹杂物的去除

导电结晶器电渣重熔渣池局部发热密度最高值在电极角部和结晶器壁附近,电极端部下方仍存在"高温区",对非金属夹杂物去除提供热力学与动力学条件。电渣重熔过程中非金属夹杂物的去除主要发生在自耗电极端头熔滴形成阶段以及熔滴穿过熔渣层阶段。综合自耗电极端部熔化至熔滴形成过程阶段、熔滴滴落并穿过渣池至金属熔池阶段和金属熔池至铸锭凝固非金属夹杂物的上浮阶段的去除率,导电结晶器电渣重熔去除非金属夹杂物的能力不低于传统电渣重熔。     

电渣重熔过程中夹杂物的控制

电渣重熔过程中非金属夹杂物的去除主要发生在自耗电极端头熔滴形成期以及熔滴滴落穿过熔渣层阶段。电渣重熔过程中原生夹杂物去除的同时将产生新的夹杂物,为了有效地控制电渣锭中的夹杂物,使用复合脱氧剂对自耗电极进行终脱氧,采用合理的重熔速度、熔渣的化学组成和供电制度,以及严格控制电渣炉内氧位。     

自耗电极冶金质量对G20CrNi2Mo轴承钢电渣锭洁净度的影响

研究了G20CrNi2Mo轴承钢电渣重熔过程自耗电极对电渣锭洁净度的影响。结果表明,电渣锭洁净度与自耗电极的冶金质量有较大的相关性。随着自耗电极氧含量的升高,电渣锭氧含量呈升高趋势。通过扫描电镜-能谱仪分析发现,氧含量较高的自耗电极中低熔点CaO-MgO-Al₂O₃夹杂物数量比低氧含量自耗电极的要多。由于低熔点夹杂物与钢液的界面能较低,限制了其在电渣重熔过程中的去除效率,从而导致电渣锭氧含量较高。通过电弧炉出钢高拉碳操作,氧含量低于0. 002 0%的锭子数量占到总量的90%以上。     

电渣重熔钢中非金属夹杂物含量及成分的控制

在电渣重熔过程中，控制自耗电极冶炼的脱氧制度并配合电渣重熔渣系的选择，可以有目的地控制电渣重熔钢中非金属夹杂物的含量和成分。对于滚珠轴承钢ＺＧＣｒ１５，当自耗电极用钢采用Ｓｉ－Ｆｅ、Ｓｉ－Ｃａ脱氧并用酸性渣重熔可以获得最佳精炼效果，使钢中夹杂物转变为硅酸盐类塑性夹杂物。上述结论在工业生产中已得到验证。     

Numerical simulation of inclusion movement in electroslag remelting process

A comprehensive three- dimensional mathematical model, which adopted the Euler- Lagrange approach, was developed to study the motion of inclusions in electroslag remelting (ESR) process. The gravity, buoyancy, drag, added mass, lift and electromagnetic pressure forces were taken into account for the solution of inclusion trajectories. Due to the great difference between the conductivity of non- metallic inclusion and molten metal, the non- metallic inclusion would be drove to migrate to the mold wall by the electromagnetic pressure force. The movement behavior and removal rate of inclusions with different diameters were investigated in detail while the current ranged from 1200A to 1800A. The results show that more than 90% inclusions are captured by the top surface of the slag pool and the slag/mold wall. Only a small part of the inclusions are still suspended in the slag, and less than 4% inclusions would pass through slag/metal interface and enter into the metal pool. The removal rate of inclusions with larger diameter is higher than that of smaller diameter in the remelting process. With the increase of the current intensity, the removal rates of the inclusions with all diameters increase.     

Evolution of CaO–MgO–Al2O3–CaS–(SiO2) inclusions in H13 die steel during electroslag remelting process

The effect of Al–Mg alloy addition on the cleanliness and CaO–MgO–Al₂O₃–CaS–(SiO₂) inclusions during electroslag remelting of H13 die steel with low oxygen content was investigated by experimental study and thermodynamic calculation. The results show that the oxygen content of consumable electrode (15?×?10^?6) was invalid to be reduced after Al–Mg alloy addition during protective gas electroslag remelting (P-ESR) process. In the case of Al–Mg alloy addition during P-ESR process, the oxygen content pick-up and silicon loss of remelted ingot were avoided, and sulphur content was further decreased. CaS content of complex inclusions were decreased significantly after P-ESR process. The type of inclusions was not changed during P-ESR process with Al–Mg alloy addition, except the increase in the concentrations of CaS in individual inclusion. The original oxide inclusions inconsumable electrode transformed to liquid state during P-ESR, and original CaS inclusions were eliminated. The CaS portion in CaS-bearing complex inclusions is the inclusion that formed on the surface of oxide inclusion during the cooling of liquid steel process in liquid metal pool.     

降低电渣重熔GCr15钢的氧含量

在420mm／250mm方形结晶器的工业炉上重熔1．2t锭,比较了含高氟的二元渣系、低氟和中氟的五元渣系、重熔气氛（Ar气保护）、自耗电极表面质量、渣中aFeO值和自耗电极含氧量对重熔钢氧含量的影响。结果表明,自耗电极氧含量为5．87×10-6和10×10-6．在氮气气氛、低氟五元渣系下重熔,电渣过程是一个增氧过程,重馆过程中降低渣中aFeO值,可使GCr15钢的氧含量降至15×10-6左右。     

37Mn5钢精炼过程夹杂物转变机理

 钢中非金属夹杂物在精炼过程中发生成分转变,影响最终产品性能。37Mn5石油套管钢生产精炼过程中,在不进行钙处理的条件下,夹杂物成分从LF炉进站时的Al₂O₃转变为软吹结束时的Al₂O₃-CaO-SiO₂-MgO-CaS复合夹杂物。为研究夹杂物改性原因,揭示夹杂物转变机理,从生产现场取钢样进行夹杂物分析。结果表明,大尺寸夹杂物与一般尺寸夹杂物的成分存在显著差异,随着精炼过程的进行,不同尺寸夹杂物成分和数密度变化趋势也有所不同。大于10 μm的夹杂物成分接近精炼渣,可能是由渣进入钢液引起的。在硅铁合金中钙的质量分数为1.17%,会起到类似钙处理的效果,快速生成大量小尺寸CaS夹杂物。通过对夹杂物成分、数量、形貌进行分析,结合渣成分和热力学计算结果,得到了37Mn5钢精炼过程夹杂物经历脱氧、耐材侵蚀、渣进入钢液、合金带入钙与钢液反应、夹杂物与钢液反应等过程,以及成分发生转变的机理。     

Investigation of inclusion re-entrainment from the steel-slag interface

The mechanism of inclusion elimination from continuous steel casting is investigated at the steelslag interface. Inclusion impact at the interface is considered under the concept of energy balance, with buoyancy forces, fluid dynamic forces, interfacial adhesion, and rebound forces determining whether the particle will pass through the interface or be retained by it. The effects of the inclusion, slag, and steel properties, as well as the effect of inclusion impact velocity, are considered at the interface. The interfacial tension between the slag and the inclusion should be smaller than that between the steel and the inclusion (negative wettability), so that the inclusions can pass into the slag layer and avoid re-entrainment. The inclusion particles that reach an equilibrium state at the steel-slag interface are subject to re-entrainment back into the steel, due to lift forces applied to them by the turbulent boundary layer at the interface. A removal criterion dependent upon the shear stress is introduced, and then the removal rates are calculated from the turbulent burst theory. It is found that the smaller diameter inclusions are trapped at the interface. Of the particles that remain at the interface, it is the larger ones that are more easily removed by the lift forces due to the turbulent shear stress. High slag viscosity is desirable, since it makes inclusion re-entrainment into the casting product more difficult.     

吹氩精炼钢包内非金属夹杂物去除机理

 通过物理模拟试验,研究分析了底吹氩精炼钢包内夹杂物去除机理以及吹氩量对其的影响规律。结果表明：钢包中夹杂物的上浮主要是通过上升的钢液流携带,底吹氩量对夹杂物在钢包表面的钢-渣界面去除行为存在重要影响。吹氩量较小时,钢-渣界面稳定,夹杂物在浮力、毛细作用力等共同作用下穿过平坦的钢-渣界面而被吸收;吹氩量较大时,钢-渣界面波动大,渣眼周围发生卷渣,夹杂物被卷入的液滴吸收,随液滴进入渣层;吹氩量大,渣眼周围形成渣泡,夹杂物被渣泡吸收,随渣泡进入渣层。吹氩量达到一定时,夹杂物被钢-渣界面的吸收成为其被去除的限制性环节,且吹氩量较大时夹杂物去除效果最差,为实际吹氩精炼过程吹气量的控制提供了指导。     

17-7PH沉淀硬化不锈钢电渣重熔过程洁净度的变化

采用35 t电弧炉-AOD脱碳-LF精炼-模铸工艺制备了17-7PH沉淀硬化不锈钢自耗电极,并通过气体保护电渣炉重熔得到了2 t重的电渣锭。利用ASPEX扫描电镜分析了电渣重熔前后17-7PH钢中夹杂物数量、尺寸、成分的变化规律,并采用SEM-EDS进一步观察夹杂物的形貌及组成。研究结果发现,电渣重熔后,O含量由6.6×10^-6降至5.7×10^-6,N含量由200×10^-6降至180×10^-6。重熔前后夹杂物的类型没有变化,重熔后总的夹杂物数量大幅减少,特别是大颗粒夹杂物的数量明显减少、尺寸减小。电渣锭中总的夹杂物以AlN夹杂物为主,其尺寸较大、数量最多。为了提高17-7PH钢电渣锭的洁净度,应尽可能减少自耗电极中的N含量,以减少电渣重熔过程AlN夹杂物的生成量。     

Research Status of Numerical Simulation of Nonmetallic Inclusions Interfacial Removal

The removal of inclusions in liquid steel has always been the focus of research, and the removal of inclusions is mainly through the process of the inclusion through the slag–steel interface. The inclusion removal process can be subdivided into inclusions in molten steel grew up rise, in steel–slag interface through separation, adsorb dissolved in molten slag 3 steps. Based on the microscopic process of three steps, this article summarizes and discusses the mathematical model, fluid mechanics model, and experimental verification method of inclusion removal process, analyzes limiting and influencing factors of inclusion removal process, and comprehensively describes the numerical simulation research progress of inclusion removal process. With the development of numerical simulation techniques and experimental equipment, some progress has been made in the study of interfacial removal of inclusions. The inclusion interface removal behavior can be analyzed semiquantitatively based on dynamic force model. The computational fluid dynamics model has advantages in studying the phenomena of the inclusion interface, and the phase-field method is often used to simulate the removal process of the inclusion interface. The combination of water model and numerical simulation, high-temperature laser confocal method, and other methods is of great help to explore the interface behavior of inclusions.     

Modelling Effect of Circulation Flow Rate on Inclusion Removal in RH Degasser

Based on the similarity principles,a 1∶ 7 scale physical model was established to study the behavior of molten steel flow and inclusion removal in a 145 t Rheinsahl-Heraeus( RH) degasser.On the basis of the quantitative measurements of the circulation flow rate and inclusion removal under various lifting gas flow rates,the effect of circulation flow rate on inclusion removal was investigated in the RH degasser.The inclusion removal rate shows the trend of first increase and then decrease twice with increasing the circulation flow rate when the circulation flow rates are smaller than 104.7 L/min.Whereas,the inclusion removal rate increases again with the further increase in circulation flow rate when the circulation flow rate is larger than 104.7 L/min.At lower circulation flow rates,inclusions are mainly removed by Stokes flotation to the slag/steel interface after inclusions are transferred near the slag/steel interface by the circulation flow.At higher circulation flow rates,the collision and aggregation of inclusions improves the inclusion removal efficiency.With the further increase in the circulation flow rate,inclusions are mainly removed by following the turbulent fluctuation( turbulent diffusion)to the slag/steel interface after inclusions are transferred near the slag/steel interface by the circulation flow.     

Inclusion Variations of Hot Working Die Steel H13 in Refining Process

 Inclusion variations of die steel H13, including changes of species, morphologies, compositions, amounts and sizes, in the production of EAF→LF→VD→ingot casting→electro-slag refining (ESR) procedure, were investigated by systematic sampling, and analyzed with scanning electron microscope (SEM), energy dispersive spectrum (EDS), and metallographic microscope. The variation mechanism was studied by comprehensive analysis of total oxygen, nitrogen, and acid soluble aluminum as well as chemical test of refining slag. Based on the investigations, technical measures for cleanness improvement were discussed. The results show that oxide inclusions in H13 steel change from irregular Al2O3→near globular CaO-MgO-Al2O3 and CaO-Al2O3-SiO2 complex inclusions→finer CaO-Al2O3-SiO2 inclusions with higher CaO content→CaO-Al2O3-SiO2 inclusions with higher Al2O3 content and irregular MgO-Al2O3 inclusions→fine irregular MgO-Al2O3-CaS inclusions in various steps of the production; the variations are related with changes of acid soluble aluminum content, reactions between slag and steel, re-oxidation of liquid steel during casting, and refining of ESR. It is also found that Al2O3 inclusions are modified by refining slag in LF and VD refining; and ESR plays a good role in inclusion removal, especially in controlling the large linear VC-CrC-MoC inclusions distributed in grain boundaries. It is suggested that casting protection should be improved, and the basicity of refining slag and acid soluble aluminum content in steel should be raised.     

热作模具钢H13的非金属夹杂物研究

 通过对EAF－LF－VD－MC－ESR工艺生产模具钢H13各工艺环节系统取样,采用多种分析方法分析夹杂物的形貌、尺寸、数量及组成,系统研究了H13钢生产过程中夹杂物演变规律,同时对模具钢中TiN和VC夹杂物的析出进行了理论分析,并提出了生产过程中控制TiN和VC夹杂物析出的措施。     

不同碱度低氧化铝精炼渣对弹簧钢夹杂物成分的影响

为了优化55SiCrA弹簧钢中夹杂物的组成和形态,采用热力学软件Factsage分别研究了CaO、SiO_2含量对CaO-SiO_2-Al_2O_3-MgO与CaO-SiO_2-Al_2O_3-MnO系相图低熔点区域面积的影响,研究结果表明:随着CaO和SiO_2含量的增加,CaO-SiO_2-Al_2O_3-MnO系相图低熔点区域面积分数逐步增大;在CaO-SiO_2-Al_2O_3-MgO系中,当CaO的质量分数为40%,SiO_2的质量分数为50%时,对应相图的低熔点区域面积最大。同时,研究了不同碱度的精炼渣对钢样中夹杂物的影响,结果表明:当精炼渣的Al_2O_3含量相同时,随着精炼渣碱度的增大,夹杂物中Al_2O_3的含量不断增加,其成分逐渐偏离低熔点区域。当精炼渣中Al_2O_3的质量分数为8%,碱度为1.2时,可得到低熔点的塑性夹杂物,形貌多为球形,尺寸在5μm以下。     

G102Cr18Mo不锈轴承钢VIM-VAR冶炼过程夹杂物的演变

通过真空感应冶炼、真空自耗重熔,制备了 G102Cr18Mo不锈轴承钢锭,利用Aspex扫描电镜分析了夹杂物数量、尺寸、面积的变化规律,并采用SEM-EDS进一步观察夹杂物的元素分布.研究结果发现,不论是真空感应还是自耗重熔,夹杂物的组成变化不大,主要由硫化锰、铝酸钙、Al-Ca-Mn-(Ti)-O-S复合夹杂物3类夹...     

电渣重熔渣系对GCr15轴承钢洁净度的影响

针对目前在电渣重熔(ESR)GCr15轴承钢D类夹杂物超标问题,设计不同渣系,并分别借助Factsage软件和经验公式计算了渣系的熔化特性、黏度、电导率等物性参数,采用实验室渣金平衡实验及现场2.5 t电渣重熔实验分析得出：最优ESR渣系为55CaF₂-25Al₂O₃-15CaO-5MgO。使用新渣系平均全氧含量较传统渣系降低41.98%,并且能够降低电渣锭不同位置的全氧含量;对于1～5μm夹杂物个数较原始渣系下降了31.25%。通过渣系对夹杂物调控,改善了GCr15轴承钢中D类夹杂物,评级级别可达到0.5级,能够更好地“净化”电渣锭。     

高端抗硫管线钢非金属夹杂物研究

采用扫描电镜和大样电解等检验方法对抗硫管线钢的冶炼过程试样和连铸坯中夹杂物的数量、尺寸、成分、形貌进行系统分析。结果表明:钢液经过LF精炼后,显微夹杂物的面积比降低了34.7%;中间包钢液的夹杂物面积比较VD出站增加了6.1%。LF进站钢液中的夹杂物主要为Al_2O_3夹杂物,在LF精炼和VD真空处理过程中由于钢渣间的相互作用,形成以CaO、MgO、Al_2O_3为主要组成的复合型夹杂物。钙处理后夹杂物中的CaO和Al_2O_3的物质的量比接近12∶7,并与钢液发生了脱硫反应,形成了含CaS的复合夹杂物。中间包开浇阶段铸坯中的显微夹杂物和大型夹杂物都明显高于稳定浇铸状态;在稳定浇铸状态下,铸坯中的w(T[O])小于15×10~(-6),大型夹杂物的含量小于0.2 mg/kg;大型夹杂物的主要来源是钢包引流砂、结晶器保护渣。     

不同冶炼方法对扭杆弹簧钢超高周疲劳性能的影响

摘要：以一种新型扭杆弹簧用高强钢（代号N1）为研究对象,采用真空自耗(VAR)和电渣重熔(ESR)冶炼方法制备得到2种实验钢（N1 VAR、N1 ESR）。研究了VAR、ESR冶炼方法对实验钢洁净度和超高周疲劳性能的影响。结果表明：采用电渣重熔工艺冶炼的N1 ESR试验钢中氧的质量分数为9×10-6,而采用真空自耗冶炼工艺的N1 VAR试验钢中氧的质量分数仅5×10-6,N1 VAR中氧化物夹杂数量和尺寸减小,夹杂周围裂纹萌生驱动力减小,超高周疲劳强度较高,疲劳寿命增加。