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1.
The mass transfer among the multiphase interactions among the steel, slag, lining refractory, and nonmetallic inclusions during the refining process of a bearing steel was studied using laboratory experiments and numerical kinetic prediction. Experiments on the system with and without the slag phase were carried out to evaluate the influence of the refractory and the slag on the mass transfer. A mathematical model coupled the ion and molecule coexistence theory, coupled-reaction model, and the surface renewal theory was established to predict the dy-namic mass transfer and composition transformation of the steel, the slag, and nonmetallic inclusions in the steel. During the refining process, Al2O3 inclusions transformed into MgO inclusions owing to the mass transfer of [Mg] at the steel/refractory interface and (MgO) at the slag/re-fractory interface. Most of the aluminum involved in the transport entered the slag and a small part of the aluminum transferred to lining re-fractory, forming the Al2O3 or MgO·Al2O3. The slag had a significant acceleration effect on the mass transfer. The mass transfer rate (or the re-action rate) of the system with the slag was approximately 5 times larger than that of the system without the slag. In the first 20 min of the re-fining, rates of magnesium mass transfer at the steel/inclusion interface, steel/refractory interface, and steel/slag interface were x, 1.1x, and 2.2x, respectively. The composition transformation of inclusions and the mass transfer of magnesium and aluminum in the steel were predicted with an acceptable accuracy using the established kinetic model.  相似文献   
2.
研究北祁连造山带玉石沟橄榄岩中富甲烷流体包裹体。激光拉曼光谱原位分析结果显示, 这些流体包裹体主要由液态或气态 CH4+C(石墨)组成, 次要成分为N2, H2O, C2H6和C3H8, 代表还原性的C-H流体形式。根据石墨的拉曼特征谱峰, 利用石墨化碳质拉曼光谱(RSCM)温度计计算石墨形成温度, 结果指示石墨在流体中沉淀的最低温度介于430~590°C之间, 表明CH4+C是非生物成因的, 并形成于地幔环境。  相似文献   
3.
主要利用微分包含的方法得到模糊微分方程的反周期解的存在性结果,并给了一个例子说明主要结果的可行性.  相似文献   
4.
5.
利用集值映射的不动点定理得到具有限时滞的混合型脉冲泛函微分包含温和解的存在性结果,改进和推广了已有的一些结果.  相似文献   
6.
硫含量对中碳非调质钢中硫化物及组织的影响   总被引:1,自引:0,他引:1  
利用真空感应炉冶炼了不同硫含量的中碳非调质钢,研究了S含量对非调质钢中硫化物形态分布及显微组织的影响.结果表明:在0.025%~0.065%范围内,随S质量分数的增加,非调质钢中硫化物的数量增多,偏聚分布现象加重;晶内铁素体比例随之升高,组织得到细化.通过热力学计算及相图信息研究了硫化物的类型转变. S含量增加时第Ⅲ类MnS在凝固末期以离异共晶形式较早析出,剩余液相中的S在凝固结束时以共晶形式析出为第Ⅱ类MnS.单独MnS以及MnS- V( C, N)复合硫化物均可作为晶内铁素体的有效形核核心,促进铁素体的生成.  相似文献   
7.
为了进一步完善增氮析氮法生成气泡去除钢液中显微非金属夹杂物技术,研究了真空处理时间、充氮压力、气体类型等因素对钢中全氧和显微非金属夹杂物的影响.结果表明:减压处理过程中,钢液中非金属夹杂物可为过饱和气体氮气形成气泡提供非均相形核核心;增氮析氮法可有效地降低钢中全氧,去除钢中显微非金属夹杂物;真空处理时间越长,钢中全氧和显微非金属夹杂物数量越低,当真空处理时间为30 min时钢中全氧去除率达到了81.6%,而且全氧质量分数最低达到7×10-6.  相似文献   
8.
实验采用MoSi2炉研究了MgO,MgO-CaO两种耐火材料对55SiCr弹簧钢中夹杂物的影响.结果表明,MgO,MgO-CaO两种坩埚冶炼均能使钢种成分控制在目标范围内,但与MgO坩埚相比,MgO-CaO坩埚净化钢液的效果更好:一方面,经MgO-CaO坩埚冶炼的55SiCr弹簧钢,钢中P,S,酸溶铝[Al]s 以及全氧T.O质量分数分别降低至56×10-6,10×10-6,≤5 ×10-6,以及4×10-6;另一方面,钢中夹杂物的平均直径由1.376μm降低至1.222μm,夹杂物尺寸<2μm的比例由79%上升至89%.这主要是因为碱性MgO-CaO坩埚兼具脱磷、脱硫、脱氧的作用,同时CaO还能与钢中的Al2O3夹杂物发生反应,生成熔点更低的复合夹杂物,因此更容易上浮去除,进一步净化钢液.  相似文献   
9.
Data from a thermodynamic database and the calculation software FactSage were used to investigate the phase diagrams of the MnO?CaO?SiO2?Al2O3 system in cutting-wire steel and the effects of oxide components on the low-melting-point (LMP) zone in the cor-responding phase diagrams. Furthermore, the activities of oxide components in the quaternary system at an Al2O3 content of 25wt%were calculated. The contents of dissolved [Al] and [O] in liquid steel in equilibrium with LMP inclusions in the MnO-CaO-SiO2-Al2O3 system were optimized. The results show that the MnO-CaO-SiO2-Al2O3 system possesses the largest LMP zone (below 1400℃) at an Al2O3 content of 25wt%and that the CaO content should be simultaneously controlled in the range of 40wt%to 45wt%. The activities of the oxide components CaO, MnO, and SiO2 should be restricted in the ranges of 0 to 0.05, 0.01 to 0.6, and 0.001 to 0.8, respectively. To obtain LMP inclusions, the [Al] and [O] contents in cutting-wire steel must be controlled within the ranges of 0.5 ×10^-6 to 1.0 ×10^-5 and 3.0 ×10^-6 to 5.0 × 10^-5, respectively.  相似文献   
10.
In the 20CrMnTi steel production process, the nitrogen content increased by 19 × 10^-6 and 29 × 10^-6, respectively, during ladle furnace(LF) refining and during the casting process from ladle to tundish. The protective casting is the key to decrease the N content. The results of thermodynamic calculations and a growth kinetics investigation show that TiN formation occurs only when the solidification fraction is greater than 0.533 under the controlled conditions used in this study for the manufacture of 20CrMnTi steel; the radius of TiN particles decreases as the Ti and N contents decrease and as the cooling rate increases. Furthermore, the theory of austenite grains controlled by second-phase particles was analyzed. The elemental analysis results showed that the Ti content was controlled at 0.04wt%–0.06wt% and the N content decreased to 0.005wt%, which satisfy the requirements for grain refinement but can also effectively prevent the precipitation of TiN inclusions in 20CrMnTi steel.  相似文献   
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