高碱度精炼渣对GCr15轴承钢洁净度的影响

 利用实验室渣-钢平衡试验研究了高碱度精炼渣对GCr15轴承钢中[w(T[O])]和夹杂物的影响。结合试验结果和热力学分析,探讨了钢中[w(T[O])、]夹杂物尺寸分布和粒径大小的变化规律,以及氧化物夹杂的转变过程。研究结果表明,碱度为6时,精炼渣(59.4%CaO-24.8%Al2O3-9.8%SiO2-6%MgO)可将钢中[w(T[O])]控制在0.000 6%以内,氧化物夹杂平均尺寸最小为2.26 μm。随着钢中[w([Ca])]和[w([Mg])]的增加,钢中氧化物夹杂转变过程为Al2O3→MgO·Al2O3→MgO→CaO-Al2O3-MgO复合夹杂物(核心为MgO,外围包裹着CaO-Al2O3)。渣-钢反应前期钢中以MgO·Al2O3为主,后期以MgO和CaO-Al2O3-MgO复合夹杂物为主。氧化物夹杂转变的试验结果与热力学分析结果相一致,大多数氧化物夹杂尺寸小于5 μm。     

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.     

Inclusion Composition Control During LF Refining for SPCC Using FactSage Combined With Industrial Trials

Steel plate cold common (SPCC) is a Al-killed steel with Ca-treatment. The control of Al2O3 inclusion into low melting point liquid region is beneficial for inclusion removal, cast-ability promotion and defects reduction during rolling. Thus it is essential to understand steel-inclusion equilibrium since inclusion composition is determined by composition of liquid steel directly through steel-inclusion reaction. Thermodynamic calculation software FactSage is performed to understand how to control inclusion composition during ladle furnace (LF) refining, and industrial trials are carried out to verify calculated results. Firstly, target region for controlling CaO-Al2O3-MgO ternary inclusion is analyzed on the basis of the ternary phase diagram and the relationship between activities related to pure solid and activities related to pure liquid was fixed by thermodynamic analysis in order to obtain reliable activities for components of inclusions in the target region by FactSage. In addition, inclusions in steel samples are detected by scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS). It is found that most of Al2O3 inclusions are modified into lower melting point region but a number of them are still located in high melting point region at the end of LF refining after Ca-treatment. Moreover, the composition of liquid steel equilibrating with liquid CaO-Al2O3-MgO inclusion is obtained by steel-inclusion equilibrium calculation when w[Al]s is approximating 0.03% as: a[O] is 1.0×10-6 to 4.0×10-6, w[Ca] is 20×10-6 to 50×10-6 and w[Mg] is 0.1×10-6 to 3.0×10-6. At last, stability diagrams of various calcium aluminates and CaS are established and they show that liquid calcium aluminate inclusions form when w[Ca] is more than 20×10-6, but CaS precipitation is difficult to prevent because sufficiently low w[S] (<0.003%) is required.     

顶渣对帘线钢中夹杂物塑性化的控制

以某钢厂生产的帘线钢铸坯试样为原料,使用硅钼棒炉对其进行顶渣熔炼实验,研究顶渣成分对CaO-Al2O3-SiO2 类夹杂物塑性化的影响。结果表明, 在顶渣碱度为0.8～1.2时,随着顶渣中Al2O3 质量分数的增加夹杂物中的Al2O3 质量分数也随之增加。当顶渣中Al2O3质量分数低于10%时,CaO-Al2O3-SiO2 类夹杂物的成分在塑性区范围,对应的此时钢液中的w［Al］s低于8×10-6。通过控制顶渣的成分可以把CaO-Al2O3-SiO2 类夹杂物的成分控制在塑性区内。     

SiO2-Al2O3-CaO-MgO系夹杂物低熔点区域优化及控制的热力学计算

为了预测CaO-Al2O3-SiO2-MgO系夹杂物具有良好变形能力的成分控制范围,首次通过热力学软件Fact-Sage对CaO-Al2O3-SiO2-MgO系液相投影图、低熔点区域大小进行了计算分析,并以阀门弹簧钢60Si2CrA为例,对CaO-Al2O3-SiO2-MgO系低熔点夹杂物的生成条件进行了探讨.结果表明...     

核电用CF8A不锈钢大型铸件表面探伤缺陷的成因及控制

摘要：CF8A不锈钢由于具有良好的耐蚀性和强韧性等优点,被用于铸造压水堆核电站主回路系统中循环泵的泵体,但铸件常出现表面探伤不合问题。通过对铸件表面探伤不合区域取样,并跟踪冶炼全流程取样,利用扫描电镜、能谱仪观察缺陷类型和夹杂物演变行为;结合Factsage软件计算,研究缺陷成因及控制方法。CF8A不锈钢冶炼过程中,AOD出钢前夹杂物主要为尖晶石;Ca处理后夹杂物主要为液态或双相CaO-Al2O3-MgO(-SiO2)夹杂;浇钢结束前,钢液中出现尖晶石和氧化铝夹杂;凝固过程中富氧化铝夹杂在铸件表面聚合造成铸件表面探伤不合。因此,控制钢液中Al元素的质量分数在0.01%左右,钙元素的质量分数在20×10-6~30×10-6左右,合理控制炉渣中SiO2和Al2O3的含量,可以减少氧化铝类夹杂的生成,提高铸件表面探伤合格率。     

高品质轴承钢BOF-LF-RH-CC和EAF-LF-VD-CC工艺夹杂物演变规律

以某公司两种不同轴承钢生产工艺为例,对BOF-LF-RH-CC和EAF-LF-VD-CC工艺生产的轴承钢中夹杂物进行了对比分析。初炼炉的出钢碳含量会对LF精炼前期夹杂物的数量以及成分产生影响,BOF出钢w(C)=0.07%的炉次,LF精炼初期夹杂物数量为5.04个/mm²且主要为Al₂O₃夹杂物;EAF出钢w(C)=0.58%的炉次,LF精炼初期夹杂物数量为2.49个/mm²且主要为MgO·Al₂O₃夹杂物,但在LF精炼结束时出钢碳含量对夹杂物数量的影响较小。LF精炼炉渣中CaO活度会对夹杂物中CaO的含量产生影响,BOF-LF-RH-CC工艺LF精炼渣CaO活度为0.632,对应的精炼结束时夹杂物中w(CaO)=5%;EAF-LF-VD-CC工艺LF精炼渣CaO活度为0.965,对应的精炼结束时夹杂物中w(CaO)=18%。对比分析过RH、VD后轴承钢夹杂物的成分和数量变化情况,发现经RH处理后MgO·Al₂O₃     

12CaO·7Al2O3 炉渣与合金钢液的反应

 12CaO·7Al2O3炉渣组成为w(SiO2)=6%,w(Al2O3)=46%,w(CaO)=48%,与合金结构钢钢液进行了实验室试验。结果表明,该渣具有很高的碱度,90 min反应结束后钢中w(TO)=0000 6%~0001 3%,w(S)=0000 4%~0001 0%。同时得出为控制钢中总氧含量应将炉渣碱度控制在9左右,钢中生成的夹杂物大都是低熔点、球状、尺寸很小的钙镁铝硅酸盐类夹杂物,这类夹杂物能够避免钢材产生各向异性,并且在轧制时能够稍许变形,能够提高钢材的抗疲劳性能。     

渣组成对钢水洁净度的影响

 在实验室基础上对比研究了w(CaO)/w(SiO2)为5、w(Al2O3)为25%的渣系A,w(CaO)/w(SiO2)为8、w(Al2O3)为46%的渣系B,与高强度合金结构钢液在1600 ℃条件下反应90 min后钢水洁净度的变化,研究结果表明：随着渣系由A到B,钢中总氧质量分数平均值由12.25×10-6降低到9.25×10-6,硫质量分数平均值由19×10-6降低到8.63×10-6,炉渣的硫分配系数LS由7~17增加到120~260;渣系A、渣系B与合金钢液反应后钢中夹杂物大部分是钙镁铝硅酸盐类夹杂,并且得出渣系B精炼条件下钢中这类夹杂熔点明显低于渣系A精炼条件下的此类夹杂。     

CaO-SiO2-Al2O3-MgO夹杂物控制影响因素的多尺度结构

 对CaO-SiO2-Al2O3-MgO夹杂物熔点的影响因素进行了多尺度分析,利用Factsage模拟了CaO质量分数对CaO-SiO2-Al2O3-MgO夹杂物熔点的影响规律。多尺度分析表明,工位操作（101 m）影响夹杂物成分（10-10 m）的最后可控因素为钙线喂入量。其通过影响局部钢液中钙质量分数（100 m）来改善熔池的动力学条件（10-3 m）,改变夹杂物中CaO质量分数（10-10 m）。模拟结果表明,当CaO质量分数为30%时,CaO-SiO2-Al2O3-MgO相图中低熔点区域的比例达到最大。通过实例分析得到了夹杂物控制的工位级效应,表明了对钢液洁净度进行多尺度深入研究的可行性。     

RH用低碳深脱硫预熔渣

为实现低碳、超低碳钢在RH中进行深脱硫且钢水不增碳,在200kg真空感应炉上对RH用低碳深脱硫预熔渣进行了脱硫试验研究,结果表明:以CaO-Al2O3-SiO2-MgO为主的低碳深脱硫预熔渣熔点低、脱硫率高,可在真空条件下将钢液中硫的质量分数由30×10-6~50×10-6脱至10×10-6~20×10-6以下,脱硫率达到55%以上,脱硫效果好,脱硫率稳定。该预熔渣中碳的质量分数小于0.05%,在脱硫过程中钢水几乎不增碳,适用于在RH中低碳、超低碳钢深脱硫。研究表明:适当地提高炉渣的光学碱度,可大大地提高其硫容量,增强炉渣的脱硫能力。使用该预熔渣处理钢水有利于钢中夹杂物的去除和细化。     

超低氧齿轮钢非金属夹杂物控制热力学计算及应用

 利用热力学软件计算了齿轮钢氧含量与夹杂物成分的关系、夹杂物转变条件。结果表明,超低氧20 CrMoH钢中具有较高塑性的非金属夹杂物成分为：SiO2 0%~10%、Al2O3 22%~55%、CaO 42%~60%、MgO 5%~10%,与之平衡的时钢液中铝含量在0.020%左右,钙含量>0.7×10-6,氧含量在0.0005%左右;选择组成为CaO>40%、Al2O3≤37%、MgO10%、(%CaO+%MgO)/%SiO2为10、SiO2含量尽量低的渣系,钢中Al2O3、MgO•Al2O3夹杂物可转变为低熔点的钙铝酸盐。上述结果在工业试验中得到了验证。     

Study on Transformation of CaO-Al₂O₃-SiO₂-MgO System Inclusions in ZG06Cr13Ni4Mo Stainless Steel

This paper aims at generally studying on the inclusions of ZGG06Cr13Ni4Mo ultra-low carbon stainless steel used for large scale hydraulic turbine sets. On the basis of analysis the industrial test samples, thermodynamic software FactSage is used to study inclusions transformation process in CaO-SiO2-Al2O3-MgO system while stainless steel is been smelting. The results illustrate the inclusions melting points and plasticity variation law. The reasonable inclusions plasticity controlling area is found out in low melting point. The melting point is up to 1280℃ While MgO weight concentration is 10% in CaO-SiO2-Al2O3-MgO system, SiO2, Al2O3 and CaO in inclusions are in weight concentration range of 50-70%, 10-20% and 10-40%, respectively. For purpose of gaining low melting point inclusions, silicon alumina radio in deoxidant should be controlled between 2-5 for ultra-low carbon stainless steel refining in industry.     

Experimental Study on Deep Desulfurizer in LF Process

 Abstract： CaO-Al2O3-SiO2-CaF2-MgO was selected as the slag system for desulfurization in LF process. The reaction between steel and slag during desulfurization has been simulated by using Factsage software to study the influence of component on the sulfur distribution ratio. In order to research the influence of CaO content, aluminum powder content and its granularity on desulfurization, laboratory experiments have been carried out in a 200 kg inductive furnace. Results showed that the optimal composition of deep desulfurizer is wCaO=64% and aluminium powder 10% with a granularity of 30 μm. Industrial trials showed that the main composition range of final slag in LF process is wCaO=530%-570%, wAl2O3=234%-251%, wSiO2=81%-100%, and wCaF2=32%-47%. The sulfur mass percent in steel is lower than 00008% with a desulfurization rate above 89%. According to the result of industrial production, this desulfurizer could meet the production requirement for ultra-low sulfur steel, of which sulfur mass percent is under 00015%.     

典型含钛超纯铁素体不锈钢冶炼-连铸过程夹杂物衍变研究

通过热力学分析、扫描电镜和EDS能谱分析等方法,系统研究了一种典型含钛超纯铁素体不锈钢（/%:≤0.01C,17.5～18.5Cr,0.40～0.55Nb,0.10～0.25Ti）80 t K-OBM-S-VOD-LF-200 mm×1 240 mm CCM过程夹杂物的衍变。结果表明,VOD还原期采用Si-Al复合脱氧,夹杂物类型以Al2O3-CaO-SiO2-MgO和Al2O3-CaO-MgO为主,钛合金化后夹杂物转变为Al2O3-CaO-TiOx-MgO,由于此类夹杂物熔点高、尺寸大,且很难通过钙处理变性,容易聚集造成水口堵塞。通过提高铝钛比至0.11以上,降低钛合金化前钢中全氧含量至25×10-6以下,使用纯净的钛铁合金可以避免形成大尺寸的含TiOx夹杂物。     

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。     

50Cr5MoV钢中非金属夹杂物及全氧

 对采用“EBT→LF→VD”工艺路线生产50Cr5MoV锻钢轧辊炼钢过程的全氧质量分数和夹杂物类型与数量进行了分析。结果表明：LF精炼后钢液中[w(T[O])]平均为0.004 7%,VD出站[w(T[O])]为0.001 4%,中间包[w(T[O])]为0.001 55%,铸坯[w(T[O])]为0.001 8%,轧材中[w(T[O])]降低至0.001 0%。LF精炼初期,钢中夹杂物主要是不规则的Al2O3夹杂,其中96.75%的夹杂物尺寸小于10 μm。LF精炼结束后,大量夹杂物转变成以CaO-Al2O3-SiO2为主要成分的0～1 0 μm复合氧化物夹杂。钢水从VD真空精炼炉向中间包转移过程中,由于保护性浇注效果差,二次氧化严重造成钢水夹杂逐渐增多,其中夹杂物主要为球形的[mCaO·nAl2O3]复合夹杂物。铸坯中99.65%的夹杂物尺寸小于10 μm,其中大部分为球形钙铝酸盐夹杂物,还有少量球状硅铝酸钙复合夹杂物。轧材中98.77%的夹杂物尺寸小于10 μm。通过对炼钢过程中各工序的工艺优化,可实现对夹杂物的有效控制, 从而确保50Cr5MoV合金铸钢的产品质量。     

含钙钡合金脱氧和非金属夹杂物控制技术研究

采用MoSi2电阻炉在1〖KG-*9〗873 K下开展了含钙钡合金脱氧和非金属夹杂物控制技术研究。结果表明，各组实验终点钢中夹杂物平均长度均小于8 μm，并都有纯三氧化二铝夹杂物存在。采用含钙钡合金的复合脱氧工艺，终点钢中未发现含钡夹杂物，有较多以CaO Al2O3为主要成分的复合夹杂物，w（T.O）＞50×10-6。用AlMnCa脱氧，终点钢样w（T.O）＝37×10-6，含氧化钙夹杂物较少，大于20 μm的夹杂物数量占总夹杂物数量的1.2%。     

超低氧齿轮钢28MnCr5中镁铝尖晶石夹杂物的控制

利用FactSage软件对28MnCr5钢液和镁铝尖晶石夹杂物的平衡反应进行了分析,当w[Al]在0.02%~0.04%之间,w[Mg](0.39~0.42)×10-6的临界范围时开始生成镁铝尖晶石。计算发现:在现有28MnCr5钢精炼工艺条件下,钢液中会不可避免生成镁铝尖晶石夹杂物。当钢液w[Mg]8.5×10-6时,加入钙不能使其转变成低熔点液态夹杂物;而当钢液w[Mg]小于此值时,增加w[Ca]时,夹杂物按照"镁铝尖晶石→CaO-Al2O3-MgO系液态夹杂物→CaO"路径转变,钢液w[Ca]增加至3×10-6左右时均能将其转化为CaO-Al2O3-MgO系液态夹杂物。计算表明,精炼渣还原提供的[Ca]不能使28MnCr5钢中镁铝尖晶石夹杂物完全变性,须采用向钢液中喂钙线等手段来提高钢液中的钙含量。     

钢包初始状态对帘线钢夹杂物的影响

运用Aspex Explorer扫描电镜对比了3种不同初始状态钢包冶炼条件下的帘线钢盘条中夹杂物成分、变形性能以及数量密度等,指出不同初始状态的钢包对帘线钢精炼渣成分和成品[Al]含量的影响。结果表明,同等条件下,分别使用冶炼过Si、Al-Si以及Al脱氧钢的钢包冶炼帘线钢时,精炼渣碱度、渣中Al_2O_3含量和成品[Al]含量均呈上升趋势,对应精炼渣碱度分别为0.95、1.1、1.4,渣中Al_2O_3质量分数分别为7.0%、11.0%、15.0%,成品[Al]的质量分数分别为7×10~(-6)、13×10~(-6)、16×10~(-6)。采用冶炼过Al、Al-Si脱氧钢的钢包冶炼的帘线钢盘条夹杂物数量密度分别为0.96、1.20个/mm~2,夹杂物中Al_2O_3平均质量分数分别为25.9%、31.8%,夹杂物塑性差,轧制后长宽比平均值分别为5.6、5.1。采用冶炼过Si脱氧钢的钢包冶炼的帘线钢盘条中夹杂物数量密度为0.79个/mm~2,夹杂物中Al_2O_3平均质量分数为15.0%,为塑性夹杂物,轧制后长宽比均值为11.3。实验证明,冶炼帘线钢不宜使用初态为Al脱氧或者Al-Si脱氧的钢包。