LF精炼渣碱度变化对304不锈钢夹杂物成分的影响

采用氧氮分析仪、扫描电镜、金相显微镜等分析手段,系统研究LF精炼渣系对304系不锈钢全氧质量分数wT[O]、夹杂物数量、尺寸及成分的影响。研究结果表明,当LF精炼渣碱度由1.5升高至2.6时,LF出站溶解氧质量分数w[O]由11.6×10~(-6)降低至4.8×10~(-6),铸坯wT[O]由47×10~(-6)降低至24×10~(-6),铸坯夹杂物总数量降低,但当量直径不大于10μm的夹杂物所占比率由77.7%增加至95.1%。热力学计算结果表明:在钢液中各元素达到平衡状态时,渣系碱度越高,低熔点夹杂物2MgO·2Al_2O_3·5SiO_2生成区域越小,MgO·Al_2O_3尖晶石类夹杂物生成区域越大,与生产试验结果一致。随着LF炉渣碱度升高,铸坯夹杂物成分中MgO和Al_2O_3的质量分数分别升高了14.4%和9.1%,当碱度不大于1.9时,铸坯中不会存在镁铝尖晶石。     

精炼渣碱度对304不锈钢夹杂物的影响

结合生产实际,采用定量金相和SEM+EDS统计分析方法,研究了硅脱氧条件下,精炼渣碱度对304奥氏体不锈钢在LF精炼、连铸过程夹杂物变化规律的影响。结果表明:钢水中主要形成球状CaO-Al2O3-SiO2类复合夹杂,适当高的精炼渣碱度有利于钢中细小夹杂物的形成。随精炼渣碱度的提高,复合夹杂物中CaO含量增加,SiO2含量减小,Al2O3含量变化不大。现场条件下,由FeSi合金带入钢中的Al形成的Al2O3对复合夹杂物的塑性变形影响较大。在精炼渣碱度分别为1.0和1.5时,铸坯复合夹杂物中Al2O3质量分数为25%左右,夹杂物的变形能力稍弱。     

低碱度低氧化铝精炼渣对帘线钢夹杂物控制

 研究了低碱度、低氧化铝精炼渣对帘线钢夹杂物控制情况。试验采用LD→LF精炼→软吹Ar→连铸工艺生产帘线钢,在碱度1.0、Al2O3质量分数为5%左右的精炼渣成分控制条件下,钢中酸溶铝AlS的质量分数控制在0.000 5%左右,进而控制夹杂物中Al2O3质量分数在22%以内,使得帘线钢中氧化物夹杂MnO-Al2O3-SiO2类、CaO-Al2O3-SiO2类复合夹杂物实现了良好的塑性化控制。根据分析,在帘线钢夹杂物去除方面,软吹氩处理对钢中CaO-Al2O3-SiO2系复合夹杂物去除效果比对MnO-Al2O3-SiO2类夹杂物更加明显;在成分控制方面,钢液中AlS含量随着炉渣碱度、炉渣Al2O3质量分数的升高而升高,而夹杂物中Al2O3质量分数会随着钢液中AlS含量升高而升高。     

齿轮钢中非金属夹杂物控制技术研究

为了降低钢的T[O]含量和生成较低熔点的非金属夹杂物以改善合金结构钢的抗疲劳破坏性能,在炉外精炼中采用了高碱度和高Al2O3含量的渣系.研究发现LF和RH精炼结束时钢液T[O]含量均随炉渣碱度增加而降低,在炉渣Al2O3含量低于25%时,T[O]随炉渣Al2O3含量减少而降低,而当炉渣Al2O3超过25%后,T[O]则随炉渣Al2O3含量增加而降低.精炼过程钢液中夹杂物按"Al2O3系夹杂物→MgO-Al2O3系夹杂物→CaO-MgO-Al2O3系夹杂物"顺序发生转变,其中MgO-Al2O3系夹杂物向CaO-MgO-Al2O3系夹杂物的转变是由外向内逐步进行的,转变速度相对较慢,因而致使LF结束时钢中仍存在许多尚未转变的Mgo-Al2O3系夹杂物.钢液T[O]对夹杂物转变有显著影响,降低T[O]含量有利于生成较低熔点的CaO-MgO-Al2O3系夹杂物.     

低碱度渣冶炼304不锈钢脱硫热力学和工业试验

为了减少不锈钢超薄板的表面缺陷,确定合适的工艺同时满足304不锈钢脱硫及夹杂物塑性化的要求。基于共存理论建立了冶炼304不锈钢九元渣系的组元活度计算模型和硫分配比LS计算模型,并与实际生产数据对比,发现AOD脱硫期及LF末期LS计算值与实测值吻合较好。理论结果显示,AOD炉渣碱度在1.4~2.4变化时,aCa O与碱度呈线性关系,得出了不同条件下精炼渣最低理论碱度,对实际生产具有一定的指导意义。由于低碱度渣脱硫效果较差,提出在AOD高碱度精炼渣脱硫、LF低碱度精炼渣使夹杂物塑性化的工艺,并进行了工业试验,结果表明,硫质量分数符合要求,钢中夹杂物处于塑性区域,为减少不锈钢超薄板的表面缺陷提供了可行方案。     

精炼渣碱度对弹簧钢夹杂物的影响研究

为了评价不同精炼渣对弹簧钢中夹杂物数量、组成、尺寸及形态的影响,在EAF→LF→RH→CC工艺流程下,设计了两种不同渣系,通过全氧分析、渣样分析、夹杂物分析等手段评价了两种精炼渣全氧及夹杂物控制水平。研究表明,相对于低碱度渣(1.0),高碱度渣(1.7)有利用钢水脱氧、脱硫,钢水全氧含量更低;不同碱度情况下,钢中夹杂物类型基本相同,主要由MnS、CaO-SiO_2-Al_2O_3、Al_2O_3-MgO、CaS-MnS、TiS-MnS等夹杂物所组成,低碱度精炼渣钢中MnS与CaO-SiO_2-Al_2O_3夹杂物数量显著多于高碱度精炼渣;高碱度渣的钢中A类、B类和D类夹杂物控制更好;从夹杂物控制水平考虑,采用碱度1.7的精炼渣更为合适。     

小方坯流程高品质轴承钢工艺

相比于电炉冶炼和大方坯流程,采用转炉冶炼加小方坯流程具有更低的生产成本。根据天钢的实际生产情况,对采用“铁水脱硫扒渣→转炉冶炼→LF造渣精炼→VD真空精炼→小方坯连铸”流程生产高品质轴承钢的关键技术进行研究。分析冶炼过程钢水及连铸坯中夹杂物可知：随着LF炉炉渣碱度的升高,钢液中wT［O］大幅降低,控制炉渣碱度R在一个较高范围（7.0~9.0）对于控制钢液中wT［O］很重要;LF精炼初期,夹杂物中Al2O3含量较高,随着精炼的进行夹杂物向着CaO-Al2O3-MgO系和Al2O3-MgO系方向夹杂物发展;VD真空处理促进钢-渣-夹杂物间反应向平衡方向移动,夹杂物接着向CaO-Al2O3-MgO系方向发展,夹杂物中CaO含量增加;在小方坯连铸过程中,采用两级电磁搅拌加低拉速、低比水量的模式获得了较小的碳偏析度。     

炉渣碱度对304纯净不锈钢冶炼的影响

通过钢液T[O]检测、夹杂物的金相电镜、扫描电镜的实验研究,分析冶炼过程不同炉渣碱度对304不锈钢钢水纯净度的影响。结果表明:304不锈钢冶炼过程的炉渣碱度较高,钢液纯净度较好。炉渣碱度分别为2.0-2.2、2.4-2.6的炉次,连铸中包钢液T[O]均值为43 ppm、26 ppm;炉渣碱度较高的4#、5#炉次,中包钢液中夹杂物总个数较少,较大尺寸11~15μm夹杂物个数明显较少;钢液中夹杂物为Ca O-Si O2-Al2O3系,炉渣碱度较低炉次的中包钢液夹杂物化学成分的Ca O含量较低。     

低氧高碳铬轴承钢LF-VD精炼时洁净度与夹杂物特征变化

研究了低氧高碳铬轴承钢在LF-VD精炼时洁净度与夹杂物类型、数量、尺寸等特征的变化规律,并关注了个别大尺寸夹杂物.试验中采用了二元碱度约为7、Al2 O3质量分数约30％ 的高碱度高Al2 O3精炼渣.LF精炼前期和中期钢中夹杂物主要为Al2 O3和MgO-Al2 O3:由于与钢液润湿性较差能够较好地去除,数量密度由L...     

高速重轨钢的脱氧与夹杂物控制

以U75V高速重轨为例,对冶炼过程的全氧含量和夹杂物的形貌、尺寸及成分进行了系统分析,对重轨钢精炼过程的脱氧与夹杂物控制进行了探讨.结果表明,炉渣碱度高有利于Si的脱氧,LF精炼后可将钢中全氧质量分数降至15×10-6以下,但高碱度会导致钢中脆性夹杂物增多;高真空虽然对碳脱氧有利,但易引起钢中铝含量升高,不利于夹杂物的...     

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。     

“两次造渣法”冶炼不锈钢超薄带理论和工业应用

 精密压延不锈钢冷轧超薄板带(<0.3 mm)要求具有良好的洁净度和夹杂物塑性化以获得良好的表面质量和力学性能,但钢水的洁净化和夹杂物塑性化在冶炼上是相互矛盾的,这增加了精密压延不锈钢板带的冶炼难度。为解决不锈钢超薄带夹杂物塑性化和钢水洁净化的矛盾问题,通过热力学理论分析和实验室渣-金平衡试验研究了精密压延不锈钢冶炼的关键问题并得出相应应对策略,炉渣碱度降低,对脱氧和脱硫不利,钢水洁净度变差,高碱度渣的使用是获得较高洁净度钢水的必要条件;随着炉炉渣碱度降低,夹杂物由CaO-SiO₂-Al₂O₃系演变为良好塑性的SiO₂-Al₂O₃-MnO系,低碱度炉渣是夹杂物塑性化必需条件; 钢中Al_s含量降低,夹杂物中Al₂O₃含量明显减小,塑性变好; 通过在渣中配加适量的MgO,可以有效抑止低碱度渣对炉衬的侵蚀。并在此基础上开发出新的“两次造渣法”冶炼工艺,在AOD脱硫期造高碱度渣脱硫和脱氧,在LF精炼造低碱度渣塑性化钢中夹杂物,实现不锈钢优异的钢水洁净度和夹杂物塑性化。工业试验结果表明, w(T[O])小于0.002 5%, w([S])小于0.001 0%,夹杂物成分为以SiO₂-Al₂O₃-MnO系为主的硅锰铝榴石类夹杂物,Al₂O₃平均质量分数小于20%,具有良好的塑性,满足生产不锈钢超薄板带的要求。     

Variation of Non-Metallic Inclusions Composition in X80 Pipeline Steel Refined by High Basicity Slag

The transformation of inclusions was studied when control technology of refining top slag in ladle furnace was used in X80 pipeline steelmaking.Sufficient amount of aluminum was added to experimental heats for final deoxidation during BOF tapping,and then the refining top slag with high basicity and strong reducibility was adopted to transform Al 2 O 3 to inclusions with low melting point.The results show that the composition of inclusions changes in order of "Al 2 O 3 → MgO-Al 2 O 3 system→ CaO-MgO-Al 2 O 3 system→ CaO-Al 2 O 3 system".And the inclusions after LF refining are liquid or semi-liquid state at the temperature of steelmaking,which are easily removable to obtain high cleanliness steel by collision,agglomeration and flotation.     

Inclusion evolution in 50CrVA spring steel by optimization of refining slag

In order to control the CaO-Al2O3 -SiO 2 -MgO system inclusions in 50CrVA spring steel in a lower melting temperature region, high temperature equilibrium experiments between steel and slag were performed in the laboratory, under the conditions of the initial slag basicity within 3-7 and the con-tent of Al2O3 between 18-35 mass%, to investigate the formation and evolution of this type of in-clusion.The results indicate that the total oxygen content in the steel decreases with the increase of slag basicity and the decrease of Al2O3 content in slags, and CaO-Al2O3 -SiO 2 -MgO inclusions tend to deviate from the low melting point region with the increase of Al2O3 content in slags.The most fa-vorable composition for the refining slag is composed of 51-56 mass% CaO, 9-13 mass% SiO2 , 20-25 mass% Al2O3 and 6 mass% MgO.In this case, the inclusions in 50CrVA spring steel are mostly in the low melting point regions, in which their plasticities are expected to improve during steel roll-ing.The MgO-based inclusions were observed in the steel matrix and the formation mechanism was theoretically and schematically revealed.It is also found that adding around 11 mass% of MgO into the refining slags is beneficial to reducing the refractory corrosion.Further work should be carried out focusing on the evolution rates of MgO-based inclusions.     

SWRH82B硬线钢CaO- Al2O3- SiO2系夹杂物塑性化控制的生产实践

为了研究SWRH82B硬线钢通过控制精炼渣的组成实现夹杂物塑性化的可行性,通过对炼钢过程中各工序的精炼渣和钢液进行取样,并对精炼渣成分、钢液总氧含量以及夹杂物的形貌、尺寸、成分等进行检测分析。结果表明,采用无铝化脱氧,并将精炼渣的碱度控制在0.8~1.2,Al2O3质量分数控制在10%以下时,能使CaO- Al2O3- SiO2系夹杂物成为塑性夹杂物;钢水经过RH真空精炼后夹杂物尺寸变大,并且夹杂物的Al2O3质量分数降低,SiO2质量分数升高,通过相关检测分析了造成此现象的原因,并提出了改进措施。     

Cleanliness of Alloying Structural Steel

 Alloying structural steel used for mechanical structures has a high requirement for cleanliness because its failures are greatly affected by non-metallic inclusions and total oxygen content in steel. It has been reported by some steelmaking plants to have some problems in controlling total oxygen content and inclusions during alloying structural steel production. For this purpose, cleanliness control in 02C-03Si-06Mn-1Cr-02Mo steel was investigated. Firstly, low melting temperature zone (≤1873 K) of CaO-Al2O3-MgO system and formation condition of low melting temperature inclusions were investigated through thermodynamic equilibrium calculation. On this basis, industrial tests were carried out. Through sampling at different stages, transformation of oxide inclusions and change of total oxygen content in steel were studied. The results show that: in order to form CaO-Al2O3-MgO system inclusions with low melting temperature, mass percent of Al2O3, MgO and CaO in inclusions should be controlled from 376% to 708%, 0 to 174% and 255% to 606%; For the condition of 1873 K and 005% (mass percent) dissolved aluminum in steel, the activities of dissolved oxygen, magnesium and calcium should be controlled as 0298×10-4-2×10-4, 01×10-5-40×10-5 and 08×10-8-180×10-8 respectively. With secondary refining proceeding, average total oxygen content and inclusion amount decrease, the type of most inclusions changes from Al2O3 after tapping to Al2O3-MgO after top slag is formed during ladle furnace refining and finally to CaO-Al2O3-MgO after RH treatment. In the final products, average total oxygen content was 127×10-6 and most inclusions were in spherical shape with size less than 5 μm.