电渣重熔过程中渣系对NiCrMoV合金钢电渣锭洁净度的影响

针对NiCrMoV合金钢电渣重熔过程中Ti元素的烧损严重问题,通过实验室实验和热力学计算研究了不同渣系对电渣锭化学成分及夹杂物数量、成分和尺寸分布的影响规律。结果表明,电渣重熔后电渣锭中总氧含量明显增加,由自耗电极的15.1×10^-6增加至(31.3～42.1)×10^-6,夹杂物数密度增加至6.54～15.95个/mm²,而氮含量变化不大;采用渣系70%CaF₂-30%Al₂O₃和55%CaF₂-25%Al₂O₃-17%CaO-3%MgO时,电渣锭中Ti元素的烧损严重,夹杂物以Al₂O₃为主,渣相中添加一定量的TiO₂能较好地控制重熔后Ti的烧损,夹杂物类型主要由Al₂O₃、Al₂O₃-CaO-TiO₂、其他氧化物夹杂...     

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。     

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。     

电渣重熔对GCr15轴承钢化学成分和夹杂物特性的影响

对采用(/%):45CaF_2,10CaO,40Al_2O_3,5MgO渣系重熔的2.3 t GCr15轴承钢电渣锭轧成的φ26 mm钢材进行了试验和分析。结果表明,电渣重熔后,电渣锭小头Al、Si烧损及增氧较大头更为严重,母材、小头、大头的Si,Ah和O含量(/%)分别为0.24,0.16,0.21;0.025,0.011,0.017和0.001 0,0.003 0,0.002 0。钢中夹杂物主要以Al_2O_3,Mg-Al-O,Ca-Al-O为主,并含有少量FiN以及以Mg-Al-O为核心,以TiN为外围的复合夹杂物;小头夹杂物总量为16.49个/mm~2,大头夹杂物总量为14.96个/mm~2,电渣锭小头以单一Al_2O_3夹杂物为主,大头以Mg-AlO,Ca-Al-O夹杂物为主,主要原因是大头Al含量较高,对渣中MgO,CaO的还原程度较高。     

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。     

CaF2-Al2O3-CaO渣系电渣重熔过程形成的渣皮结构及成分

分析了9.5 t热作模钢H13重熔锭在380 kg 60CaF₂-30Al₂O₃-10CaO三元渣的重熔过程中渣头和渣皮的结构和成分。结果表明,电渣锭生产过程的渣皮呈现明显的分层结构,自外侧向内,依次为急冷层、氧化铝析出层和内部返熔层;渣头中CaF₂含量普遍低于初渣值,而渣皮中CaF₂含量高于初渣值;铝氧化物在渣头外缘比重最高;重熔后渣的氧含量明显高于初渣。     

1Cr18Ni9Ti不锈钢1.2 t锭电渣重熔过程[Ti]烧损控制的实践

统计分析了1Cr18Ni9Ti钢1.2 t锭电渣重熔过程母材中的Ti含量-[Ti](0.586%～0.839%Ti)、渣中TiO₂含量(2.1%～4.8%TiO₂)和填充比(0.2～0.4)对[Ti]平均烧损值的影响。结果得出,电渣重熔过程电渣锭下部[Ti]的烧损较上部严重;随母材[Ti]的提高,电渣锭中平均烧损[Ti]降低;随渣中TiO₂含量-(TiO₂)提高,电渣锭下部[Ti]的平均烧损β值增加,而电渣锭上部β值没有明显变化,(TiO₂)不宜超过2%;提高填充比有利于抑制[Ti]烧损。     

核电用超纯奥氏体不锈钢316H电渣重熔氢含量控制

为研究电渣重熔过程氢含量控制影响因素，电渣重熔生产Φ590 mm电渣锭时试验了4种不同组成的电渣渣系，同时电渣重熔过程配合氩气保护。通过试验不同渣系组成及不同氩气流量下保护气氛，最终确定电渣重熔在w(CaF₂)∶w(Al₂O₃)∶w(CaO)=60%∶30%∶10%组成渣系下，采用40 L/min的氩气流量控制，可使Φ590 mm电渣锭成品氢含量控制在5×10^-4%以下。     

电渣重熔高氮钢的洁净度研究

对高氮钢电渣重熔前后夹杂物进行对比研究,分析不同渣系和自耗电极氧含量对重熔后夹杂物的影响。研究发现,不同渣系对电渣钢的洁净度影响很大,适当提高w(CaO)/w(Al2O3)可有效降低电渣锭中的夹杂物和全氧量。不同氧含量的自耗电极进行重熔后,电渣锭全氧量及夹杂物种类和组成成分差别不大,夹杂物成分中w(MnO)/w(MnO+Al2O3)≈0.23~0.32,自耗电极中的氧含量与电渣重熔的洁净度没有直接关系,采用氧质量分数为(40~100)×10-6的不同自耗电极,电渣重熔后氧质量分数始终保持在(20~30)×10-6。     

电渣重熔渣系对C-HRA-3耐热合金夹杂物的影响

本文利用10 kg级保护气氛电渣重熔炉，研究了两种电渣重熔渣系对C-HRA-3耐热合金电渣锭夹杂物数量、尺寸、分布规律的影响。结果表明，60%CaF₂-20%Al₂O₃-10%CaO-10%MgO渣系的液相线温度为1 417℃，新型50.4%CaF₂-26.1%Al₂O₃-19.5%CaO-4%MgO渣系的液相线温度为1 324℃，且固液两相区的温度区间较窄，液态熔渣的电阻率高，可实现C-HRA-3合金电渣重熔的高熔速稳定冶炼。两种渣系冶炼的电渣锭中，夹杂物主要包括氧化物、碳氮化物和硫化物等类型，电渣锭边缘位置夹杂物数量与自耗电极相近，电渣锭边缘到中心位置夹杂物数量呈现出逐渐减少的趋势。两种渣系冶炼的电渣锭中，氧化物夹杂的平均尺寸分别为3.019μm和2.341μm。新型渣系冶炼的电渣锭中，沿径向不同位置处，尺寸>3μm的氧化物夹杂数量占比均更小，对C-HRA-3合金大尺寸氧化物夹杂具有更显著的去除效果。     

稀土渣系电渣重熔H13钢铸锭的成分、组织及夹杂物特征

稀土(RE)微合金化是开发高品质模具钢的重要手段之一.采用稀土渣系结合电渣重熔实现H 13钢铸锭的稀土添加,重点对比研究了稀土氧化铝渣系和氧化铝渣系所制备H13钢铸锭的成分、组织及夹杂物特征,揭示了稀土氧化铝渣系对于H13钢铸态组织的稀土改性作用及机制.结果表明,采用稀土氧化铝渣系或稀土氧化钙渣系均可制备稀土质量分数约...     

Electrode reactions in dc electroslag remelting of steel rod

Abstract

The non-metallic inclusion content increased significantly when a steel rod of Fe-Ni was remelted by dc electroslag remelting. The silicon content increased slightly. The manganese and sulphur contents did not change. The total aluminium content in the ingot was max. 0·7%, while that in the electrode was only 10 ppm. The aluminium cations Al³+ in the slag are reduced to metallic aluminium at the slag/electrode interface, while O² - anions are oxidised to dissolved O in the metal pool. This Al and O subsequently recombine to form alumina inclusions in the metal pool. The inclusion content was dependent on the alumina content in the slag. When a rod of plain carbon steel was remelted, however, the increase in nonmetallic inclusion content was as little as one-tenth of that for the remelted Fe-Ni rod. The non-metallic inclusion content was independent of the polarity of the electrode.     

Effect of electromagnetic stirring on inclusions in 304 stainless steel electroslag ingot

Based the self designed electroslag remelting furnace with electromagnetic stirring, the effect of external magnetic field on the number, size and type of inclusions in 304 stainless steel electroslag ingot was analyzed in detail. The content of oxygen and nitrogen in electroslag ingot was analyzed by ONH analyzer, and the morphology and element distribution of inclusions were observed by SEM. Finally, the ASPEX was used to analyse the size, number and type of inclusions. The results show that the oxygen content in electroslag ingot increases from 23.7×10-6 in consumable electrode to 64.70×10-6 whether magnetic field is applied or not, and the oxygen content increases to 67.4×10-6 at most from 23.7×10-6 in the electrode. But the nitrogen content in electroslag ingot decreased slightly to 659.3×10-6 from 675.5×10-6 in the electrode. The magnetic field has almost no effect on the type of inclusions, which mainly includes Al2O3, MnS-Al2O3, Al-Si-O, Al-Ca-O, Al-Si-Ca-O, Al-Mg-O and other inclusions. After the magnetic field is applied, the amount of large inclusions in electroslag ingot decreases, but the total number of inclusions increases when the magnetic induction intensity is small. When the magnetic induction intensity is 10 mT, the number of inclusions increases by 42.60%, but the maximum size of the inclusions decreases.     

电磁搅拌对304不锈钢电渣锭夹杂物的影响

摘要：通过自行设计的带电磁搅拌的电渣重熔炉,以304奥氏体不锈钢为研究对象,详细分析外加磁场对电渣锭夹杂物数量、大小以及类型的影响。采用氧氮氢分析仪检测氧、氮气体含量,采用扫描电镜观察夹杂物的形貌、组成,并采用ASPEX分析夹杂物的尺寸变化。结果表明,无论是否外加磁场,电渣锭中的氧含量都有所增加,从自耗电极中氧质量分数由23.7×10-6最高增至64.70×10-6;而相比于自耗电极,氮含量略微降低,其质量分数从675.5×10-6降低至659.33×10-6;无论是否加入磁场,电渣锭中的夹杂物种类并无变化,主要由Al2O3、MnS-Al2O3、Al-Si-O、Al-Ca-O、Al-Si-Ca-O、Al-Mg-O及其他夹杂物组成;在施加磁场后,电渣锭中的大颗粒夹杂物数量有所减少。外加磁场强度较小时并不能有效去除夹杂物,反而会增加夹杂物的数量,当磁感应强度为10mT时,夹杂物数量相比于未加磁场时增加了4260%,但是最大尺寸有所减小。     

现代电渣重熔先进技术特征与演进

 电渣重熔是制备高端特殊钢和合金的关键冶炼工艺,在铸锭质量和成材率方面优势明显。随着中国装备制造业的快速发展,对所用钢及合金的质量和性能要求不断提高,而传统电渣重熔技术面临电耗高、产品质量稳定性差等问题。现代电渣冶金技术的发展核心在于浅平熔池形状的稳定控制和杂质元素的高效去除,目标是更高洁净度、更高凝固质量和更高生产效率。为了让国内冶金工作者了解目前电渣重熔技术的最新发展动态,助力中国电渣冶金技术的开发和应用,综述了近年来国内外相继涌现的先进技术与理论,分析了国内外在相关技术的应用特征和演进方向。中国在电渣炉设备制造、气体保护电渣重熔技术、同轴供电技术和结晶器导电技术方面基本与国际先进水平同步,但尚未形成完善可靠的渣系配置理论、精炼过程的热力学及动力学理论,较国外仍有差距,这已成为限制电渣产品质量提升的主要因素之一。低频电源技术、真空电渣重熔技术和旋转电极电渣重熔技术具有极高的工业化应用前景,需要进一步明确其对工艺过程和产品质量的影响规律。摆动控制已成为国际先进电渣企业的主流控制技术,却是中国电渣炉设备制造的短板,借助在线检测和模拟仿真技术的恒熔池形状控制技术是中国电渣冶金控制技术的发展方向。     

电渣重熔对FeCrAl不锈钢中夹杂物的影响

应用扫描电镜(SEM)及X射线能谱分析仪(EDS)对真空感应炉熔炼(VIM)和电渣重熔炉熔炼(ESR)的FeCrAl不锈钢中夹杂物的成分、形貌、数量、大小进行统计分析。结果表明,AlN是2个钢锭的主要夹杂物,电渣重熔过程中产生的高熔点稀土化合物可作为AlN析出的异质核心。电渣重熔使自耗电极中尺寸大于10μm的夹杂物基本消失,ESR锭中尺寸小于5μm的夹杂物达到86.7%。电渣重熔减小了AlN的平均尺寸,去除了大尺寸的AlN,使AlN的总面积明显减小。热力学计算结果表明,VIM锭中AlN可以直接在液相中析出;ESR锭中氮含量的降低造成AlN不能直接在液相中析出,随着凝固的进行,[Al]和[N]在残余液相中富集,当凝固分率大于0.615后,AlN才能在凝固前沿的残余液相中析出。     

Effects of relative motion between consumable electrodes and mould on solidification structure of electroslag ingots during electroslag remelting process

Abstract

Steel solidification process control, especially in the solidification process of high alloy steel, and improvement of the solidification structure have been increasingly gaining interest among metallurgists, particularly the electroslag workers. To further develop the electroslag remelting (ESR) process and to improve the advantage of the ingot solidification structure, the effects of relative motion between the consumable electrodes and the mould (namely, mould rotation) on chemical element distribution were observed in this study, as well as the compact density changes in electroslag ingots. Experiment results show that applying relative motion between the mould and the consumable electrodes in ESR results in a more uniform chemical element distribution in the electroslag ingots. Compared with the electroslag ingot of conventional ESR, maximum segregation of carbon could decrease from 3·19 to 1·146, and statistical segregation decreased from 0·2636 to 0·0608. Maximum segregation of chromium could decrease from 1·316 to 1·253, and statistical segregation decreased from 0·2753 to 0·1201. The compact density for the stationary mould increased from 0·7693 to a compact density of 0·9501 for the rotating mould. The improvement in the solidification structure of the electroslag ingot can be attributed to mould motion, which led to the generation of a shallow pool and the improvement of the solidification structure. But the excessive rotation rate is harmful to solidification structure instead due to the molten metal pool motion caused by violent slag pool motion.     

Effect of Slag on Inclusions During Electroslag Remelting Process of Die Steel

Many factors influence the non-metallic inclusions in electroslag steel including furnace atmosphere and inclusions’ content in the consumable electrode, slag amount and its composition, power input, melting rate, filling ratio, and so on. Fluoride containing slag, which influences the non-metallic inclusions to a great extent, has been widely used for the electroslag remelting process. The current paper focuses on the effect of fluoride containing slag on the inclusions in electroslag ingots based on the interaction of the slag-metal interface and electroslag remelting process. In this work, die steel of CR-5A and several slags have been employed for investigating the effect of slag on inclusions in an electrical resistance furnace under argon atmosphere in order to eliminate the effect of ambient oxygen. Specimens were taken at different times for analyzing the content, dimensions, and type of non-metallic inclusions. Results of quantitative metallographic analysis indicate that a multi-component slag has better capacity for controlling the amount of inclusions; especially protective gas atmosphere has also been adopted. The findings of inclusions in electroslag steel by SEM–EDS analysis reveal that most non-metallic inclusions in electroslag steel are MgO-Al₂O₃ inclusions for multi-component slags, but it is Al₂O₃ inclusions when remelting using conventional 70 wt pct CaF₂-30 wt pct Al₂O₃ slag. The maximal inclusions’ size using multi-component slags is less than that using conventional binary slag. Small filling ratio as well as protective gas atmosphere is favorable for controlling the non-metallic inclusions in electroslag steel. All the results obtained will be compared to the original state inclusions in steel, which contribute to choice of slag for electroslag remelting.