帘线钢夹杂物熔化温度与变形状态的研究

使用热力学软件FactSage计算固定CaO、MgO含量的MnO-SiO2-Al2O3渣系相图低熔点区(≤1 500℃),及固定MnO、MgO含量的CaO-SiO2-Al2O3渣系相图低熔点区;同时按照扫描电镜能谱分析得到的帘线钢盘条中夹杂物成分,用分析纯试剂配制夹杂物,测定其熔化温度,将其标在相图中相应位置,并与FactSage计算的熔点结果对比.结果表明,夹杂物熔化温度测定结果与FactSage计算结果基本相符,在此基础上,讨论了夹杂物熔点与变形状态的关系.     

精密铸造型壳缺陷分析

分析了精密铸造型壳的两种缺陷——"浆片"夹杂物、"型壳面层脱落"形成的原因。浆片夹杂物是因为蜡模之间配合处或浇注系统与蜡模之间存在缝隙形成的。型壳面层脱落是因为热膨胀导致结合面的结合不紧或组树不当造成的。这两种缺陷通过改变蜡模结构、组树方式、改变浇注方式等措施避免。     

X80管线钢LF-RH二次精炼过程夹杂物行为及控制

研究了210 t BOF-LF-RH-CC工艺流程生产X80管线钢(%:0.041～0.044C、0.15Si、1.78～1.80Mn、0.007～0.010P、0.000 8～0.001 2S、0.039～0.047[Al]s)时精炼过程中夹杂物的变化。在BOF出钢阶段采用加Al强脱氧(0.01%～0.02%[Al]s),LF精炼过程采用高碱度、强还原性精炼渣(精炼渣成分%:50～58CaO、7～10MgO、20～25Al₂O₃、4～7SiO₂、0.5～1.4TFe),炉渣和钢液反应活跃,使得钢中Al₂O₃夹杂物很快向液态钙铝酸盐和部分液态CaO-MgO-Al₂O₃复合夹杂物转变。液态夹杂物通过碰撞、聚合、长大及上浮去除,提高了钢液的洁净度。浇铸前T[O]降到(7～10)×10^-6,钢中夹杂物尺寸在3～5μm,试验炉次的热轧板内未发现大尺寸的低熔点钙铝酸盐类长条夹杂物。     

基于模糊包含的粗糙集模型与模糊信任测度

提出基于模糊包含的模糊粗糙集模型,并给出其相关性质。讨论由模糊粗糙集的下、上近似所决定的模糊信任测度、模糊似然测度的性质并将之应用到随机模糊信息系统的属性约简中。     

50 t EBT EAF-LF( VD) -CC流程生产G55SiMoVA轴承钢的工艺实践

石油钻具用轴承钢G55SiMoVA(/%:0.52~0.55C,0.90~1.10Si,0.30~0.50Mn,0.40~0.60Mo,0.20~0.30V,≤0.015P,≤0.015S)的工艺流程为废钢+60%~70%铁水-50 t UHP EBT EAF-60 t LF-VD-260 mm×300 mm连铸。通过采用电弧炉全程泡沫渣埋弧操作,EBT出钢合金化,控制LF二次精炼渣(/%:46~54CaO,10~16SiO₂,11~13Al₂O₃,4.5~7.0MgO)碱度3.2~4.5,SiC扩散脱氧和60~80 L/min流量氩气搅拌,VD 67 Pa真空状态下保持20 min,连铸全程保护浇铸,所生产G55SiMoVA轴承钢轧材中氧含量为9×10^-6~10×10^-6。     

履带钢低倍缺陷原因浅析

针对履带钢成品低倍试验后存在肉眼可见的贯穿“裂纹”缺陷进行分析,发现缺陷是由大量夹杂物经酸洗腐蚀后形成的易腐蚀线;结合履带板轧制孔型设计基本原理,计算出该缺陷在未轧制前位于连铸坯心部位置,推断该缺陷是由连铸坯心部缩孔引起;针对连铸坯心部缩孔提出纠正预防措施。     

Evolution of Al2O3 inclusions by cerium treatment in low carbon high manganese steel

The influence of cerium (Ce) treatment on the morphologies, size and distributions of Al2O3 inclu-sions in low carbon high manganese steel was investigated by OM, SEM-EDS and theoretical calcula-tion.The results showed that Ce can modify the morphologies and types of Al2O3 inclusions.After Ce treatment, the irregular Al2O3 inclusions were replaced by smaller and dispersive spherical cerium oxysulfides.The effects of treatment time and Ce content on the evolution of Al2O3 inclusions were examined.It indicated that Al2O3 inclusions were wrapped by rare earth inclusions to form a ring like shape Ce-enriched band around the inclusions.Model was established to elucidate the evolution mech-anism of Al2O3 inclusions.Evolution kinetics of inclusions was discussed qualitatively to analyze the velocity controlled step.It was found that diffusion of Ce3 + and Al3 + in solid inclusion core and the formed intermediate layer would be the limited step during the evolution process.     

Effect of alloy addition on inclusion evolution in stainless steels

The number, morphology, size and composition of inclusions after deoxidation and alloying in Ti-stabilised stainless steel were investigated. This was carried out by electrolytic extraction of inclusions from steel matrix, followed by microscopic examination. It was found that after the addition of ferrosilicon and manganese, and later aluminium, the composition of inclusions changed from manganese silicate-rich inclusions to alumina-rich inclusions. After tapping and titanium wire feeding, three types of TiN inclusion morphologies were observed, single, twinned and clusters. Both the turbulence and Stokes' collision mechanisms play a considerable role in the formation of TiN clusters.     

Influence of calcium treatment on cleanness and fatigue life of 60Si2MnA spring steel

Contrasting experiments of Al killed 60Si2MnA spring steel were carried out between using and excluding calcium treatment under LF refining slags with low and high basicity ratios (R: CaO/SiO₂?=?3.4, 5.0), respectively. Results showed the high basicity refining slag had a certain effect on controlling inclusions and improving the cleanness of spring steel similarly to calcium treatment. The T.[O] (total oxygen) content of steel without calcium treatment got to below 15?ppm and the fatigue life was long, up to 7.8?×?10⁶?cycles. But in order to reduce the T.[O] below 10?ppm, as well as inclusion number and size in spring steel further, meanwhile, the appropriate calcium treatment should still be used. Besides, as the [Ca] content in the steel with calcium treatment increased, inclusions transformed from Al₂O₃–SiO₂–CaO–MgO to Al₂O₃–SiO₂–CaO–MgO–CaS completely, which reduced the formations of voids between inclusions and steel matrix, and voids decreased with the increase of CaO/Al₂O₃ value and CaS content of inclusions. Finally, the fatigue life of spring steel with high basicity slag and calcium treatment increased to 9.1?×?10⁶ cycles.     

Stress-Focusing Effect Following Dynamically Transforming Anisotropic Strains in a Spherical Zirconia Inclusion

When an infinite elastic medium with a spherical inclusion of zirconia is suddenly subjected to an instantaneous transversely anisotropic phase transformation caused by impact cooling, stress waves occur at the surface of spherical inclusion the moment instantaneous transformation strains are applied. The stress waves in an inclusion proceeds radially inward to the center of the inclusion and show the stress-focusing effects. This paper analyzes the stress-focusing effects caused by the transversely isotropic phase transformation in the spherical inclusion of zirconia embedded in the infinite domain. By using the ray theory, the numerical results give a clear indication of the mechanism of stress-focusing effects caused by the phase transformation.