细小异相去除夹杂物的试验研究

提出用脱氧净化剂产生细小气泡去除夹杂物并同时生成低熔点液态复合氧化物吸附夹杂物的控制技术，用SiMo电阻炉进行了热态试验。结果表明，脱氧净化剂在高温下分解生成小气泡和小渣滴，去除了细小夹杂物，处理后钢中的氧化物夹杂物显著降低，全氧的质量分数最低达到19×10^-6。     

RH精炼喂CaSi线去除无取向硅钢中的非金属夹杂物

结合工业化生产的无取向硅钢,进行了RH精炼喂CaSi线去除钢中的非金属夹杂物试验研究.针对不同的钙处理条件,分析了CaS夹杂生成热力学,观察了夹杂物的形貌和尺寸分布,确定了夹杂物的类型、数量,探讨了钙处理后钢中夹杂物的变化规律.结果表明,本试验条件下,钙处理可以有效抑制MnS、AlN夹杂物的生成,有效促进钢中微细夹杂物的聚合、上浮、去除,钢质纯净度明显提高.经过合适的钙处理后,钢中的夹杂物以独立存在的CaO为主,同时有少量含CaO、SiO2 、MgO的复合夹杂,没有发现CaS夹杂存在.这部分夹杂物的尺寸集中分布在2～20μm,数量约为1.8×105 个/mm3.     

Al2O3夹杂物在钢-渣界面处的运动特性及去除率

通过理论计算和分析,研究了夹杂物颗粒在钢-渣界面处夹杂物去除层内的运动特性及去除率。结果表明:在夹杂物去除层内,Al2O3夹杂物颗粒的布朗扩散上浮临界尺寸为1.33μm,直径小于临界尺寸的夹杂物颗粒很难上浮去除;布朗碰撞的优势区域主要是直径为2.5μm以下的夹杂物颗粒之间以及直径为2.5～5μm夹杂物颗粒与0.5μm以下的微小颗粒之间的碰撞;直径为20～150μm的夹杂物颗粒在钢-渣界面去除层中9min内很容易完全上浮去除,而直径小于10μm的夹杂物颗粒去除率很低且升高缓慢,是提高钢液洁净度的主要控制对象。     

微小相去除夹杂物的水模型实验

采用水模型实验模拟了钢包钢水中微小相去除夹杂物的现象,利用高速摄像仪和图像处理技术分析了小气泡和夹杂物模拟物的运动行为,并且进行了净化剂和3种制球方式去除夹杂模拟物的实验,分析了气泡发生方式去除夹杂物的效果和原因,以提高钢水洁净度。结果表明:加入净化剂后,促进了夹杂物的去除,发现了气泡捕获多个夹杂模拟物的现象。在不同时刻,夹杂模拟物的去除率比没有产生小气泡时的去除率要高,平均提高13.66%。在3种气泡发生方式中,由于气泡生成时对内核材料的冲击作用,促进了净化剂的裂解,使得以外层净化剂加内核模拟物方式形成的复合球体最容易产生小气泡,夹杂物去除率100%,效果最好。     

稀土-镁复合处理对GCr15轴承钢中夹杂物的影响

为了尽可能的去除钢中大颗粒的夹杂物, 在实验条件下通过向GCr15轴承钢中添加适量镁、稀土对夹杂物进行改性, 并利用Aspex夹杂物自动分析仪和扫描电镜对钢中改性后的夹杂物尺寸、类型、形貌等进行了观察、分析, 研究了稀土-镁复合处理对夹杂物的影响规律.研究结果表明, 对轴承钢中加入微量镁处理, 可将未进行镁处理钢中的MnS-Al₂O₃、MnS、Al₂O₃夹杂改性为以含硫、镁复合夹杂物为主, 同时包含少量Al₂O₃、镁铝尖晶石夹杂.进一步采用稀土-镁复合处理后, 钢中的夹杂物转变为主要以含Re-S-O夹杂物为主, Al₂O₃、MnS、镁铝尖晶石夹杂逐步消失, 且夹杂物成球状分布, 绝大多数夹杂物在5 μm以下.稀土-镁复合处理轴承钢后, 10 μm以上的大颗粒夹杂物大大降低, 钢中的夹杂物明显得到细化.钢中镁含量不变时, 随着稀土含量的增加, 大颗粒夹杂物比例明显下降.而在稀土含量相近的情况下, 增加钢中的镁含量也有利于大颗粒夹杂物的去除.稀土-镁的相互作用进一步促进了夹杂物的细化.      

复合粉剂包芯线应用研究

将制备的Fe-Si+CaO复合粉剂包芯线加入钢液,研究其对去除夹杂物的作用.结果表明:复合粉剂包芯线能够加入到钢液,其中粉剂可以扩散分布到钢液中,与钢液中夹杂物形成硅钙铝复合夹杂物,外观呈球形,容易聚集上浮排出钢液.工业应用中,复合粉剂包芯线在不影响钢种成分控制的情况下,能够起到去除夹杂物、净化钢液的作用,应用复合粉剂...     

中间包双层挡墙钙镁质填料对钢液夹杂物的影响

带填料的双层挡墙是1种新型的中间包控流装置,选择合适的填料可以更好地去除钢液中夹杂物。研究了使用钙镁质耐火材料作为双层挡墙的填料时,钙镁质耐火材料中w(CaO)对去除钢液夹杂物的影响。研究发现:填入w(CaO)为20%的钙镁质耐火材料时,试样钢中单位面积的夹杂物减少12.92%;而填入w(CaO)为30%的钙镁质耐火材料时,试样钢中夹杂物减少了25.84%。可以看出,钙镁质耐火材料作为中间包双层挡墙填料可以强化中间包去除夹杂物的效果。     

钙处理时机对LF-RH精炼过程Al2O3基夹杂物的影响

为研究LF-RH精炼工艺生产Q690钢时不同钙处理时机下夹杂物特征的变化,开展工业试验对RH精炼前后钙处理炉次取样进行定量分析对比。钙处理后夹杂物中CaO质量分数持续增加,CaS质量分数瞬态增加,夹杂物熔点降低。RH精炼前钙处理炉次中,RH精炼过程夹杂物的成分接近低熔点区,结束时夹杂物数量密度和面积分数分别为15个/mm2和0.01%。RH精炼后钙处理炉次中,RH精炼过程夹杂物依旧为高熔点Al₂O₃-MgO类型,结束时夹杂物数量密度和面积分数分别降至1个/mm2和0.002 5%。RH精炼前钙处理会使RH精炼过程夹杂物熔点以及夹杂物与钢液间的接触角降低,导致夹杂物去除驱动力降低,从而抑制夹杂物的去除。因此LF-RH精炼工艺生产铝脱氧钢时,为提高精炼过程钢中非金属夹杂物的去除效率,应在RH精炼后进行钙处理操作。     

RH铝脱氧后夹杂物碰撞聚合去除的数学模型

在夹杂物碰撞经典聚合模型的基础上,使用了指数级增长的夹杂物分组方式,建立RH铝氧反应生成夹杂物、夹杂物碰撞聚合和夹杂物去除过程的数学模型,从而对RH冶炼过程夹杂物的质量分数及分布进行预测。得到结论如下：模拟结果与文献给出数据有很好的吻合度,模型真实可靠。夹杂物质量分数随着金属铝的加入而快速增加,循环300 s后,夹杂物的总质量分数从最开始的0升至0.065%左右,夹杂物质量分数达到最大值,继而在上浮、壁面吸附和顶渣吸附的作用下去除。经过900 s左右的钢液循环后,夹杂物的总质量分数降至0.01%左右,其整体去除率在84.6%左右,说明RH循环对夹杂物有很好的去除作用。加铝后900 s,2μm和50.8μm的夹杂物质量分数的最大值分别为0.000 02%和0.007 8%。     

中包扩容提升钢液纯净度生产实践

影响钢洁净度因素之一为钢中非金属夹杂物的数量、尺寸、成分和形貌.夹杂物的形核、长大和去除与钢液的流动、夹杂物颗粒间的碰撞密切相关.研究发现,在整个中间包浇注过程中,夹杂物颗粒间碰撞长大和去除过程一直处于非稳态,达到平衡所需时间为2440s,目前中间包平均停留时间仅为514s,随着碰撞过程的进行,小尺寸夹杂物颗粒逐渐碰撞...     

轴承钢二次精炼过程夹杂物演变规律

 研究了轴承钢LF精炼和RH真空处理过程各类夹杂物的成分、种类和数量变化,并结合热力学模拟计算了夹杂物与钢液的界面参数,并对试验结果进行分析讨论。夹杂物分析结果表明,精炼25 min后,脱氧产物Al₂O₃消失,钢中夹杂物以纯尖晶石、含少量CaO的尖晶石、CaO·2Al₂O₃和CaO·Al₂O₃为主。继续精炼65 min至LF精炼结束,钢中夹杂物仍以纯尖晶石、含少量CaO的尖晶石、CaO·2Al₂O₃和CaO·Al₂O₃为主。RH真空处理25 min后,钢中夹杂物总数量较LF精炼结束降低75%,其中,纯尖晶石和含少量CaO的尖晶石去除率分别为99.5%和93.2%,CaO·2Al₂O₃去除率为67%。RH破空后钢中夹杂物以液态钙铝酸盐CaO·Al₂O₃和12CaO·7Al₂O₃为主。精炼过程尖晶石类夹杂物尺寸集中在10 μm以下,尺寸大于20 μm夹杂物主要为处于液相区的钙铝酸盐,这些钙铝酸盐在LF精炼前期就已经存在。与钢水接触角大于90°的固态夹杂物纯尖晶石、含少量CaO的尖晶石和CaO·2Al₂O₃在RH真空处理过程容易去除,与钢水接触角小于90°的液态夹杂物CaO·Al₂O₃和12CaO·7Al₂O₃不易去除。因此,将LF精炼结束的夹杂物控制为固态夹杂物有利于RH真空处理过程夹杂物的高效去除。热力学计算结果表明,当钢中w(T[O])为0.001 0%、w([Mg])大于0.000 18%时,脱氧产物Al₂O₃热力学上就不能稳定存在。铝脱氧、高碱度渣精炼条件下很难稳定地获得固态Al₂O₃夹杂物。为获得完全固态尖晶石或高熔点钙铝酸盐夹杂物,钢中w([Ca])需控制在0.000 1%以内。钢中w([Ca])大于0.000 2%,就具备生成液态夹杂物的热力学条件。     

Investigation on the removal efficiency of inclusions in Al-killed liquid steel in different refining processes

Industry trials were carried out to study the removal efficiency of inclusions in Al-killed liquid steel in the processes of BOF–LF–RH–CC and BOF–RH–CC. It was found that the removal efficiency of inclusions has a high dependence on inclusion types. Solid inclusions are more easily to be removed than liquid inclusions. The removal efficiency of solid Al₂O₃ inclusions is higher than that of solid CaO–Al₂O₃–MgO inclusions. As liquid CaO–Al₂O₃–MgO inclusions coexisted with solid CaO–Al₂O₃–MgO inclusions in the liquid steel, the low removal efficiency of inclusions in RH degassing process was found in BOF–LF–RH–CC process. However, high removal efficiency and ultra-low total oxygen (T.O) content were obtained in BOF–RH–CC process because the inclusions were mainly composed of solid Al₂O₃ although initial T.O content before RH degassing was relatively high. This is due to the fact that solid Al₂O₃ tends to form cluster-shaped inclusions which have both a higher contact angle and a lower work of adhesion with steel than calcium aluminate, resulting in easier removal by RH degassing. Therefore, it is proposed to weaken steel–slag reaction and calcium treatment before RH degassing to retain solid Al₂O₃ inclusions in the steel.     

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。     

GCr15轴承钢EAF-LF-VD-CC流程非金属夹杂物的演变

 为研究GCr15轴承钢中非金属夹杂物的演变,对某钢厂EAF-LF-VD-CC流程生产的GCr15轴承钢进行全流程取样,利用可进行大面积自动检测分析的ASPEX扫描电镜结合普通扫描电镜(SEM-EDS),系统分析了各工序中夹杂物的演变行为。结果表明,GCr15轴承钢精炼过程中夹杂物主要类型为MgO-Al₂O₃-CaO类复合夹杂物与MnS,少量SiO₂-Al₂O₃,90%以上夹杂物尺寸为1～8 μm。随着精炼的进行,夹杂物数量逐渐减少,在VD软吹阶段后期夹杂物数量及总面积降到最低。精炼期间,夹杂物成分在最初的高Al₂O₃(w([Al₂O₃])>80%)的区域逐渐向MgO、CaO含量升高的区域转移,VD破真空后MgO(w([MgO])>20%)、CaO(w([CaO])>30%)达到最高,之后向Al₂O₃含量升高的区域移动,最终在中间包浇注时停留在高Al₂O₃(w([Al₂O₃])>65%)的区域。钢中Ds类夹杂物主要为MgO-Al₂O₃-CaO类复合夹杂物,Ds类夹杂物的生成及去除随机性强,VD对Ds类夹杂物有较强去除作用。     

Analysis of formation mechanism about Ca-Mg-Al spinel type inclusions in cold thin rolling sheet

The cracking of ultra low carbon Al deoxidized killed steel during cold rolling and stamping was analyzed by SEM and EDS. It was determined that the main inclusions consisted of Al2O3, CaO and MgO, which are Ca-Mg-Al spinel inclusions. The composition of the ladle top slag and corrosion of the tundish covering agent and coating were investigated, and the source of inclusions was discussed. It was found that Al2O3 is the product of deoxidation and secondary oxidation. The source of CaO is the reaction between CaO of higher activity in slag with acid soluble aluminum Als in molten steel, which leads to the entry of element Ca into molten steel and the formation of CaO with oxygen in molten steel. The reaction of MgO, which comes from MgO in tundish covering slag and MgO corroded from tundish coating, with Als in molten steel leads to element Mg entering molten steel, and then MgO is formed with oxygen in molten steel.     

冷轧薄板钙镁铝尖晶石类夹杂物成因分析

摘要：针对超低碳铝脱氧镇静钢在冷轧冲压过程中出现开裂情况进行了电镜和能谱成分分析,确定了主要夹杂物含有Al2O3、CaO及MgO,为钙镁铝尖晶石类夹杂物。研究了该问题炉次的钢包顶渣组分、中间包覆盖剂及涂层侵蚀情况,讨论了夹杂物的来源。结果显示,Al2O3为脱氧产物及二次氧化的产物;CaO的来源为渣中较高活度的CaO与钢水中酸溶铝Als反应导致Ca元素进入钢水,进而与钢水中的O生成CaO。MgO主要为中间包覆盖剂氧化镁及涂层融蚀的氧化镁进入中间包渣系,与钢水中的Als反应导致Mg元素进入钢水,再与钢水中的O生成MgO。     

Study on Formation Mechanism of CaO-SiO<Subscript>2</Subscript>-Based Inclusions in Saw Wire Steel

Attempts were made to elucidate the formation mechanism of CaO-SiO₂-based inclusions in saw wires by both laboratory experiments and industrial trials. The key point was to make clear the origin of CaO in such oxide inclusions. Probable origins of [Ca] in steel were first discussed, which can be taken into steel from the steel-slag reaction or ferrous alloy. As a result, slag-steel chemical reaction equilibrium was carefully evaluated at 1873 K (1600 °C) to classify the changes of dissolved aluminum ([Al]), total magnesium (Mg), and total calcium (Ca) in steel and the caused composition variations of inclusions. With the rise of slag basicity from 0.5 to 1.8, [Al] was remarkably increased from 0.00045 to 0.00139 mass pct, whereas Mg varied in the range of 0.00038 to 0.00048 mass pct. By contrast, Ca was constantly kept below 0.00003 mass pct. Accordingly, Al₂O₃ and MgO in inclusions witnessed obvious rises from 5 to 23 mass pct and from 2 to 8 mass pct, respectively. By contrast, inclusions were free of CaO when slag basicity was below 1.5. With slag basicity further increased to 1.8, CaO witnessed a negligible rise to only 1.0 mass pct on average. This phenomenon agreed well with thermodynamic calculations, which revealed that chemical reaction between steel and CaO in slag (for example, between [Si] and CaO) was weak to hardly supplying sufficient [Ca] to steel to increase CaO in inclusions. Ca contained in ferrous alloys as contaminations was not the cause of CaO-SiO₂-based inclusions, either. The industrial trial results indicated that CaO-SiO₂-based inclusions have been readily produced in short time just after BOF tapping. Also, a percentage of them changed slightly with the proceeding of refining. Based on the good agreement of laboratory, industrial, and thermodynamics calculations results, it can be reasonably concluded that CaO-SiO₂-based inclusions in saw wire were exogenous particles from entrapped/emulsified top slag, but not products of slag-steel-inclusion chemical reactions.     

电渣重熔过程中氧化物夹杂的变化

利用扫描电镜分析了自耗电极和电渣重熔钢中夹杂物的特征,结合热力学计算,分析了氧硫复合夹杂物在电渣重熔过程中的转变机理。结果表明,电渣重熔采用气氛保护结合脱氧操作可以将自耗电极全氧质量分数由0.0017%降低至0.0008%。电渣重熔之后钢中小于3 μm夹杂物的比例显著增加。自耗电极中的夹杂物为CaS与含质量分数3%和11%左右MgO的CaO–Al₂O₃–SiO₂–MgO结合的两类复合夹杂物。电渣过程未被去除的氧化物夹杂中的SiO₂被钢液中酸溶铝还原,保留至电渣锭中。电渣锭中含约1%MgO和2%SiO₂且成分均匀的CaO–Al₂O₃–SiO₂–MgO是在电渣过程中新生的夹杂物。自耗电极中的CaS通过分解为钢液中溶解Ca和S,以及通过与液态氧化物夹杂中Al₂O₃反应的途径在电渣过程被去除。电渣锭中低熔点氧化物夹杂周围环状CaS是钢液凝固过程中溶解S、酸溶铝Al与氧化物夹杂中CaO的反应产物,高熔点氧化物夹杂周围环状CaS是钢液凝固过程中Ca和S偏析后反应新生的夹杂物。复合夹杂物中补丁状CaS是在电渣重熔钢液冷却过程中由复合夹杂物熔体中析出的。