RH真空处理GCr15轴承钢中全氧及显微夹杂物的行为研究

针对RH工艺生产轴承钢,通过现场试验研究了RH真空处理时间对钢中全氧和显微夹杂物的影响.试验结果表明,延长RH真空时间可以进一步降低钢中全氧和显微夹杂物的数量,RH脱氧主要是通过显微夹杂物的去除,全氧与显微夹杂物随时间的变化关系基本一致;真空处理25min可使钢液中全氧和显微夹杂降低约60%,比14min时多降低约13%,并得出邢钢轴承钢生产条件下,RH精炼过程钢液的表观脱氧速度系数为-0.036min-1;工艺优化后147炉轴承钢产品的平均全氧为6.7×10-6.     

高品质GCr15轴承钢二次精炼过程中夹杂物的演变规律

采用FE-SEM/EDS研究了转炉流程生产的GCr15轴承钢LF、RH精炼过程中夹杂物的演变规律,分析了其演变机理。结果表明:钢中复合夹杂物的演变规律可归纳为:Al2O3→MgO·Al2O3→(CaO-MgO-Al2O3-(CaS))复合氧化物夹杂和Al2O3→(Al2O3-MnS)→(Al2O3-MnS-Ti(C,N))复合氧硫碳氮物夹杂2种方式。LF精炼过程脱硫作用明显,钢中的硫化物夹杂数量大幅减少。LF精炼初期钢中主要是MnS、Al2O3、TiN的单相夹杂物。LF精炼结束后钢中的夹杂物演变为Al2O3为核心外包氧化物及MnS、TiN、Ti(C,N)、CaS的复合夹杂物。精炼渣中的CaO和耐火材料中的MgO经还原后与钢中溶解氧反应导致LF精炼结束时D类夹杂物增加。RH及软吹处理进一步强化了去除钢中的硫化物,但D类及其与A、T类复合的夹杂物含量增加。在LF阶段,夹杂物尺寸主要集中在1~3μm范围内,到RH阶段,夹杂物尺寸则主要集中分布在小于1μm的粒度范围。最大夹杂物尺寸由10.79μm降到5.68μm,单位面积夹杂个数由372个/mm2降到258个/mm2。RH及软吹处理有效地降低了钢中大于3μm的夹杂物。     

钢液精炼和连铸过程中物理去除夹杂物现状及展望

夹杂物去除是钢液精炼的重要任务之一。目前与去除夹杂物相关的工艺方法主要有:钢包-电磁搅拌和钢包底吹氩;RH及RH侧底复吹;中间包-控流装置、气幕挡墙和通道电磁感应加热;结晶器电磁搅拌与电磁制动和水口吹氩。本文总结了钢水精炼中各个反应器去除夹杂物的方法和机理,并分析了影响夹杂物去除效率的主要因素,为钢水二次精炼的夹杂物去除工艺优化提供理论依据和参考。     

无取向硅钢RH精炼过程中夹杂物行为研究

针对无取向硅钢RH精炼工艺各阶段现场取样,系统研究了钢中夹杂物数量、尺寸及成分的演变规律及钢水的洁净度变化。结果表明,钢中夹杂物主要是Al_2O_3及其复合夹杂,尺寸大部分集中在0～2μm,形状以球形和椭球形为主。从RH进站到RH出站,钢中夹杂物数量不断减少,共减少了9.63个/mm2,而尺寸小于1μm的夹杂物仅仅减少了0.85个/mm~2,可见细小夹杂物去除效果不明显。加Al脱氧一个循环时,夹杂物体积百分数下降最快,平均去除率为71.6%,钢中平均总氧含量下降了70%,钢液的洁净度明显提高。但铝脱氧后生成大量细小夹杂物,且随着加Al循环的进行有明显长大的趋势。适当延长铝脱氧的净循环时间,可能是促进细小夹杂物充分长大去除的有效途径。     

硬线钢夹杂物行为

针对唐钢硬线钢冶炼的现行工艺与条件,经过系统取样、综合分析对硬线钢生产过程中非金属夹杂物类型、来源、数量及分布进行了系统研究.研究表明:铸坯总体积率为0.0625%.显微夹杂的数量平均值为16.66个/mm2,面积百分比为0.018%.铸坯中的显微夹杂是硫化物夹杂、硅酸盐夹杂物、氧化铝夹杂物.铸坯中大型夹杂物的平均值为31.5mg/10Kg.铸坯中主要的大型夹杂物是硅酸盐和铝酸盐,其次还包括少量的硫化物.铸坯中夹杂物主要来源于脱氧产物、保护渣和覆盖剂的卷入.     

气瓶钢精炼过程中的MgO·Al_2O_3夹杂物

研究了EAF-LF-VD-CC流程冶炼气瓶钢30CrMo时精炼过程中含MgO.Al2O3夹杂物的生成和转化,对夹杂物进行了三维分析观察.研究结果表明:LF精炼30min后夹杂物中Mg含量减小,Ca含量增加,MgO.Al2O3夹杂物消失.LF精炼后期Mg含量变化不大,Ca含量减小,未出现MgO.Al2O3夹杂物;VD精炼过程中夹杂物中的Mg含量增加,Ca含量变化不大,重新生成了MgO.Al2O3夹杂物;精炼过程中MgO.Al2O3夹杂物可以向复合夹杂物转变的,但为防止精炼后期MgO.Al2O3夹杂物重新生成必须保证钢液中具有一定的钙含量.     

硬线钢夹杂物行为

针对唐钢硬线钢冶炼的现行工艺与条件,经过系统取样、综合分析对硬线钢生产过程中非金属夹杂物类型、来源、数量及分布进行了系统研究。研究表明:铸坯总体积率为0.0625%。显微夹杂的数量平均值为16.66个/mm2,面积百分比为0.018%。铸坯中的显微夹杂是硫化物夹杂、硅酸盐夹杂物、氧化铝夹杂物。铸坯中大型夹杂物的平均值为31.5mg/10Kg。铸坯中主要的大型夹杂物是硅酸盐和铝酸盐,其次还包括少量的硫化物。铸坯中夹杂物主要来源于脱氧产物、保护渣和覆盖剂的卷入。     

BOF-LF-CSP工艺低碳铝镇静钢精炼过程的夹杂物变化

对BOF-LF-CSP工艺生产低碳铝镇静钢精炼过程连续密集取样,运用ASPEX扫描电镜统计分析了夹杂物成分、尺寸分布和数量变化.发现喂铝线后夹杂物数密度和面积分数都急剧增加.精炼20 min至钙处理前软吹期间,夹杂物数密度变化不大,但夹杂物面积分数却明显下降.精炼结束时主要为含有少量CaO的MgO-Al2O3尖晶石类夹杂.钙处理后,夹杂物数密度和面积分数都有增加,主要为钙铝酸盐和由于喂入过量钙生成的CaS夹杂.     

BOF-LF-CSP工艺低碳铝镇静钢精炼过程的夹杂物变化

对BOF-LF-CSP工艺生产低碳铝镇静钢精炼过程连续密集取样,运用ASPEX扫描电镜统计分析了夹杂物成分、尺寸分布和数量变化.发现喂铝线后夹杂物数密度和面积分数都急剧增加.精炼20 min至钙处理前软吹期间,夹杂物数密度变化不大,但夹杂物面积分数却明显下降.精炼结束时主要为含有少量CaO的MgO-Al₂O₃尖晶石类夹杂.钙处理后,夹杂物数密度和面积分数都有增加,主要为钙铝酸盐和由于喂入过量钙生成的CaS夹杂.     

高级别船板钢炉外精炼过程洁净度研究

为了研究采用BOF-LF-RH-CC工艺生产的A32船板钢洁净度水平,进行了三炉工业实验.通过对冶炼过程系统取样分析,研究了钢中总氧、氮含量变化,夹杂物的转变规律及机理.结果表明:该工艺生产的船板钢有较高的洁净度,中包总氧控制在2×10-5以下,氮含量控制在4×10-5以下;LF精炼过程中,钢中总氧、夹杂物数量密度和平均尺寸均降低,夹杂物转变为Ca O-Mg O-Al2O3三元系;RH精炼过程中,钢中总氧和夹杂物数量密度降低,而夹杂物平均尺寸升高;钙处理过程中,夹杂物数量密度升高,而夹杂物平均尺寸降低,夹杂物转变为Ca O-Al2O3-Ca S三元系.     

Cleaning IF molten steel with dispersed in-situ heterophases induced by the composite sphere explosive reaction in RH ladles

A novel fine inclusion removal technology was put forward with dispersed in-situ heterophases induced by the composite sphere explosive reaction. A composite sphere with this function was designed and prepared using a laboratory scale batch-type balling disc (at 12 r/min), and the composite sphere was fed at the end of the RH refining process. The results indicate that inclusions in the IF molten steel can be removed effectively by feeding composite spheres in RH ladle. Compared with conventional inclusion removal technology, using this novel technology, the amount of oxide inclusions can be decreased to a lower level and the inclusion size becomes finer, the total oxygen content in the as-cast slab can approach 5×10?6, and the cost per ton of steel produced can be reduced by 5-12 Yuan RMB.     

Cleaning IF molten steel with dispersed <Emphasis Type="Italic">in-situ</Emphasis> heterophases induced by the composite sphere explosive reaction in RH ladles

A novel fine inclusion removal technology was put forward with dispersed in-situ heterophases induced by the composite sphere explosive reaction. A composite sphere with this function was designed and prepared using a laboratory scale batch-type balling disc (at 12 r/min), and the composite sphere was fed at the end of the RH refining process. The results indicate that inclusions in the IF molten steel can be removed effectively by feeding composite spheres in RH ladle. Compared with conventional inclusion removal technology, using this novel technology, the amount of oxide inclusions can be decreased to a lower level and the inclusion size becomes finer, the total oxygen content in the as-cast slab can approach 5×10⁻⁶, and the cost per ton of steel produced can be reduced by 5–12 Yuan RMB.     

Ultrahigh cycle fatigue fracture mechanism of high-quality bearing steel obtained through different deoxidation methods

The mechanism of oxide inclusions in fatigue crack initiation in the very-high cycle fatigue(VHCF)regime was clarified by subjecting bearing steels deoxidized by Al(Al-deoxidized steel)and Si(Si-deoxidized steel)to ultrasonic tension-compression fatigue tests(stress ratio,R=−1)and analyzing the characteristics of the detected inclusions.Results show that the main types of inclusions in Si-and Al-deoxidized steels are silicate and calcium aluminate,respectively.The content of calcium aluminate inclusions larger than 15μm in Si-deoxidized steel is lower than that in Al-deoxidized steel,and the difference observed may be attributed to different inclusion generation processes during melting.Despite differences in their cleanliness and total oxygen contents,the Si-and Al-deoxidized steels show similar VHCF lives.The factors causing fatigue failure in these steels reveal distinct differences.Calcium aluminate inclusions are responsible for the cracks in Al-deoxidized steel.By comparison,most fatigue cracks in Si-deoxidized steel are triggered by the inhomogeneity of a steel matrix,which indicates that the damage mechanisms of the steel matrix can be a critical issue for this type of steel.A minor portion of the cracks in Si-deoxidized steel could be attributed to different types of inclusions.The mechanisms of fatigue fracture caused by calcium aluminate and silicate inclusions were further analyzed.Calcium aluminate inclusions first separate from the steel matrix and then trigger crack generation.Silicate inclusions and the steel matrix are closely combined in a fatigue process;thus,these inclusions have mild effects on the fatigue life of bearing steels.Si/Mn deoxidation is an effective method to produce high-quality bearing steel with a long fatigue life and good liquid steel fluidity.     

带有旋流的RH精炼系统循环流动的实验研究

探讨RH真空脱气装置水模型上升管中施加旋流以提高系统精炼效率的可能性,分别采用平直叶片叶轮和轴流式叶轮产生旋流,通过水模型实验,比较有旋流和无旋流上升管中气液两相流体流动现象的差别.利用超声波流量计测量系统的循环流量,利用摄像机记录气液两相流动状态.水模型实验结果表明,与无旋流情况相比,施加旋流后循环流量显著增大.由于向心力作用,气泡向管道中心区域积聚,从而使气泡与杂质物碰撞合并的机会大大增加;同时还能够避免气泡吸附在管壁上,提高RH真空精炼装置的寿命.     

18wt%Cr–8wt%Ni不锈钢中增塑性MnO–Al2O3–SiO2基非金属夹杂物的演变及其浸泡性能

The properties of MnO–Al₂O₃–SiO₂-based plasticized inclusion are likely to change during soaking  process due to its low melting point. In this study, the evolution of the MnO–Al₂O₃–SiO₂-based inclusion of 18wt%Cr?8wt%Ni stainless steel under isothermal soaking process at 1250°C for different times was investigated by laboratory-scale experiments and thermodynamic analysis. The results showed that the inclusion population density increased at the first stage and then decreased while their average size first decreased and then increased. In addition, almost no Cr₂O₃-concentrated regions existed within the inclusion before soaking, but more and more Cr₂O₃ precipitates were formed during soaking. Furthermore, the plasticity of the inclusion deteriorated due to a decrease in the amount of liquid phase and an increase in the high-melting-point-phase MnO–Cr₂O₃ spinel after the soaking process. In-situ observations by high-temperature confocal laser scanning microscopy (CLSM) confirmed that liquid phases were produced in the inclusions and the inclusions grew rather quickly during the soaking process. Both the experimental results and thermodynamic analysis conclude that there are three routes for inclusion evolution during the soaking process. In particular, Ostwald ripening plays an important role in the inclusion evolution, i.e., MnO–Al₂O₃–SiO₂-based inclusions grow by absorbing the newly precipitated smaller-size MnO–Cr₂O₃ inclusions.     

不同碱度精炼渣系对弹簧钢夹杂物的影响

哈贝马斯对《启蒙辩证法》的否定性解读,使得该著中的拯救逻辑遭到歪曲。由哈贝马斯的解读所延伸出的对《启蒙辩证法》拯救逻辑的美学化和精神分析化的重构与阿多尔诺的哲学思想相矛盾,由此我们必须重新反思哈贝马斯的解读模式。《启蒙辩证法》并非仅仅局限于工具理性批判,它通过有规定的否定达到了对现代启蒙当中现实权力因素的内在批判,它因此并没有彻底否定启蒙也没有重新树立新的乌托邦。对自然的回忆的拯救逻辑意味着思想必须对自身展开批判,以达到重新正视社会现实中的苦难现象,从而解构抽象主体的优先地位。     

A36和45A钢LF精炼过程效果分析

通过LF精炼生产A36和45A钢,分析了精炼碱度(R)和(FeO+MnO)含量对脱氧的影响,以及精炼碱度(R)和(FeO)含量对脱硫的影响,研究得到脱硫率分别为61.3%和64.3%.同时,对精炼过程中[P]、[H]、[N]含量的变化规律进行了分析,结果表明金相夹杂物去除率平均值为70.27%,最高值为85.62%.     

连铸中间包内夹杂物去除行为的水模型研究

通过选择乳状液滴模拟夹杂物和连铸中间包水模型实验,考察了控流装置、浇铸速度、夹杂物粒径对中间包内夹杂物去除行为的影响规律.结果表明:挡墙-挡坝组合控流夹杂物去除效果最佳,中间包内强湍流区夹杂物的碰撞聚合以及向上和表面流速的增加是主因;中间包注流区加入抑湍器,虽然其流体流动特征发生改变,但对夹杂物去除率的影响并不显著;较高的浇铸速度下,单纯靠控流装置的优化已不能很好地改善夹杂物的去除效果.