This study experimentally investigated, using a water-model hydrodynamic analogue, theeffects of crystallizer rotational speed and baffle configuration on the flow-field structure,mass transfer, and mixing behavior inside the crucible of a rotational segregation modelsystem relevant to silicon processing. Three configurations were examined: no baffle,straight baffles, and inclined baffles. Flow visualization and stimulus-response tracerexperiments were conducted at 200 and 300 rpm to compare their effects on the main flowpattern and mixing characteristics. The results showed that, without baffles, a completeannular main flow formed, and the fluid moved downward spirally along the crystallizerwall. Mixing was relatively fast, indicating limited potential for local tracer retention.With straight baffles, the main flow was strongly obstructed and redistributed, and themixing time in local bottom regions, especially in front of the 90 degrees baffle, was markedlyprolonged. This behavior suggested a more favorable hydrodynamic environment forlocal retention and accumulation in the model system, and the effect was most evidentat 200 rpm. With inclined baffles, transport in the upper region was enhanced, whereasbottom flow was weakened. Although the tracer could move downward along the bafflesurface, it was rapidly swept away after reaching the bottom, indicating reduced stabilityof local accumulation. Increasing the rotational speed from 200 to 300 rpm strengthenedthe overall flow and shortened the mixing time under all conditions. Overall, straightbaffles, particularly at 200 rpm, produced the strongest tendency for local retention in thepresent model system. These results provide preliminary hydrodynamic insight into flowregulation and transport behavior in rotational segregation systems.

Secondary refining is a critical stage that determines steel properties. Its effectiveness is directly governed by the flow and mixing behavior of molten steel. At present, water model experiments are widely employed to investigate flow and mixing behavior during ladle refining. However, the effects of tracer volume and the geometric scale ratio are often neglected. In this study, a 130 t industrial ladle was taken as the prototype, and two water models with geometric scale ratios of 1:5.6 and 1:3 were established. Six tracer volumes were designed to systematically investigate the flow and mixing behavior under different geometric scale ratios. The results show that, with increasing tracer volume, the transport pattern in the small ladle transitions from a top-to-bottom to a center-to-side, whereas in the large ladle, the transport pattern consistently remains top-to-bottom. In both ladles, the mixing time at all monitoring points exhibited a trend of first decreasing and then increasing with increasing tracer volume, although the inflection points differed between the two ladles. For the small ladle, the turning point occurred at Dimensionless tracer amount (Dta) = 0.39 & times; 10(-3), whereas for the large ladle, it occurred at Dta = 0.26 & times; 10(-3). Further analysis indicates that when Dta > 0.51 & times; 10(-3), tracer injection in the small ladle significantly disturbs the original flow field structure. Therefore, the optimal tracer volume for the small ladle is Dta = 0.39 & times; 10(-3). In contrast, the large ladle maintains a relatively stable flow field even at higher tracer volumes. This study clarifies the volume of tracers and the selection of geometric scale ratios. The research results can effectively reduce measurement errors and enhance the reliability of experimental results.

During continuous casting, the flow behavior of liquid steel in the tundish directly affects the temperature distribution of liquid steel, inclusion removal, and billet quality. In tundish-related research, water model experiments remain an intuitive method for investigating the flow process in the tundish. However, water model experiments are often conducted in different seasons, and variations in experimental temperature can change fluid properties such as density and viscosity, thereby affecting flow characteristics and the comparability of experimental results. In this study, a 1:3.57 transparent bare single-strand tundish model made of acrylic was used, and the differences in tracer transport processes at 7 degrees C and 20 degrees C, as well as the influence of different tracer dosages on the experimental results, were systematically investigated through flow visualization and stimulus-response experiments. The results showed that, under the 7 degrees C condition, the upward transport tendency of the pure ink tracer was weakened, the overall flow remained closer to the tundish bottom, the transport speed decreased, and the time required to reach the outlet was significantly prolonged. For the saturated KCl solution tracer, a lower temperature enhanced its transport along the bottom toward the outlet and suppressed its diffusion toward the liquid surface. The RTD results showed that, after the temperature was increased, the curves shifted to the left as a whole, and both the peak time and the mean residence time were shortened. The outflow percentage of tracer results showed that the difference for the 10 mL saturated KCl solution between the 7 degrees C and 20 degrees C conditions was the most significant. At 7 degrees C, the total outflow percentage of the 10 mL salt solution tracer at 1500 s was 76.86%, which was 22.97% lower than that at 20 degrees C. As the tracer dosage increased, the differences in the transport process, RTD curves, and outflow percentage curves under different temperature conditions gradually decreased, indicating that the effect of dosage on the experimental results gradually became stronger than that of temperature. These results indicate that the combined effects of experimental temperature and tracer dosage cannot be neglected in tundish water model experiments.

Rare earth can modify inclusions in non-oriented silicon steel which is harmful to magnetic properties. This study focused on the 3.1% Si non-oriented silicon steel under industrial production conditions. Samples were taken during the stages before and after addition of rare earth ferrosilicon alloy in Ruhrstahl-Heraeus (RH) unit, different pouring time in tundish, and continuous casting slab. This study systematically examined the morphology, composition, and size distribution of inclusions throughout the smelting process of non-oriented silicon steel by scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS), and thermodynamic analysis at liquid steel temperature and thermodynamic analysis of equilibrium solidification. The research results demonstrated that the rare earth treatment ultimately modifies the original Al2O3 inclusions in the non-oriented silicon steel into REAlO3 and RE2O2S inclusions, while also aggregating AlN inclusions to form composite inclusions. After rare earth modification, the average size of the inclusions decreases. In the RH treatment process, the inclusions before the addition of rare earth ferrosilicon alloy are mainly AlN and Al2O3. After the addition of rare earth ferrosilicon alloy, the inclusions are mainly RES and REAlO3. In the tundish and continuous casting, the rare earth content decreased, and the rare earth inclusions transform into RE2O2S and REAlO3. For the size of inclusions, after adding rare earth ferrosilicon alloy, the average size of inclusions rapidly decreased from 16.15 μm to 2.65 μm and reach its minimum size 2.16 μm at the end of RH treatment. When the molten steel entered the tundish, the average size of inclusions increased slightly and gradually decreased with the progress of pouring. The average size of inclusions in the slab is 5.79 μm. Phase stability diagram calculation indicates the most stable rare earth inclusion is Ce2O2S in molten steel. Thermodynamic calculations indicated that Al2O3, Ce2O2S, Ce2S3, AlN, and MnS precipitate sequentially during the equilibrium solidification process of molten steel.

Mixing time, as a key parameter for evaluating ladle refining efficiency, has long attracted extensive attention from researchers. In typical experimental studies, salt solution tracers are introduced into ladle water models to assess the degree of mixing within the ladle. Previous studies have demonstrated that the volume of tracer can significantly influence the measured mixing time. However, the gas flow rates employed in these studies are generally relatively high, whereas, in industrial operations, especially during final composition adjustments, lower gas flow rates are often applied. To systematically investigate the effect of the salt solution tracer volume on the mixing efficiency in a ladle water model under asymmetrical gas stirring with a low gas flow rate, a 1:3-scaled water model was developed based on a 130-ton industrial ladle. The mixing behaviors corresponding to different tracer volumes were comprehensively analyzed. The results indicate that the relationship between tracer volume and mixing time is non-monotonic. As the tracer volume increases, the mixing time first decreases and then increases, reaching a minimum at 185 mL. When the tracer volume was small, the dimensionless concentration curves at Monitoring Point 4 exhibited two distinct patterns: A parabolic profile, which was when the tracer initially moved through the left and central regions and then slowly crossed the gas plume to reach the monitoring point. A sinusoidal profile, which was when the tracer predominantly circulated along the right side of the ladle. When the tracer volume exceeded 277 mL, the concentration curves at Monitoring Point 4 consistently exhibited a sinusoidal pattern. Compared with moderate gas flow conditions (8.3 L/min), the peak concentration at Monitoring Point 3 was significantly lower under a low gas flow (2.3 L/min), and the overall mixing time was longer, indicating reduced mixing efficiency. Based on the findings, a recommended tracer volume range of 185–277 mL is proposed for low gas flow conditions (2.3 L/min) to achieve accurate and efficient mixing time measurements with minimal disturbance to the flow field. It was also observed that when the tracer concentration was relatively low, the mixing behavior throughout the ladle became more uniform.

In the production process of electrical steel, with respect to the industrial RH (Ruhrstahl–Heraeus), the steel producers must balance the high-circulation flow rate (operating efficiency) and the frequent cleaning of cold steel in the vacuum chamber due to the splashing of liquid steel (high maintenance costs). Excessive lifting gas flow can induce splashing, causing cold steel to adhere to the inner walls of the vacuum chamber. To address this issue, this study utilized an 80-ton RH vacuum refining unit from a specific plant as the research prototype and established a 1:2.6 scale water model for physical model simulation. Two innovative blowing methods were implemented by adding gas injection nozzles to the sidewalls and to the bottom of the vacuum chamber, respectively. The study investigated the effects of altering the blowing method on liquid surface fluctuations, flow patterns, the circulation flow rate, and the mixing time without changing the total gas flow rate. For the macroscopic flow in the RH unit, implementing side-blowing on the sidewalls of the vacuum chamber can accelerate the diffusion rate of the ink tracer, whereas implementing bottom-blowing in the vacuum chamber has little effect on the diffusion rate. The results show that modifying the blowing method can effectively reduce liquid surface fluctuations and suppress the splashing behavior within the vacuum chamber. Firstly, implementing side-blowing causes the ink tracer flow pattern within the vacuum chamber to become triangular, to increase the circulation flow rate, to shorten the residence time of the ink tracer within the chamber, and simultaneously to promote mixing in the ladle, which reduces the mixing time. Secondly, implementing bottom-blowing results in the formation of a gas column at the center of the vacuum chamber, which suppresses fluid flow within the chamber. Compared with side-blowing, it reduces the circulation flow rate and increases the mixing time in the ladle. Combined gas blowing through the up-snorkel and sidewalls is effective in solving splashing issues and reducing the mixing time in RH vacuum refining, and this method is a good candidate for industrial applications.

In continuous casting, fewer strand operations are sometimes required to match production schedules. However, the study of flow behavior and temperature distribution under fewer strand casting conditions remains insufficiently systematic, especially with regard to the grade casting process, which has not yet been explored. This study presents an innovative investigation of the grade transition process in a symmetrical 12-strand tundish under fewer strand casting conditions. Seven operational cases were analyzed: standard casting (the normal symmetric Case 0), individual closure of strands 1–6 (the asymmetric Cases 1–6), and simultaneous closure of strands 1–2 (the asymmetric Case 7). Notably, strand closures in Cases 5 and 6 significantly impair flow characteristics in their respective strands. The impact area temperature reaches approximately 1844 K (new heat) after 30 min of continuous casting. However, Case 6 exhibits persistent low-temperature regions near strands 5 and 6. The average transition billet lengths for Cases 0 to 7 are 72.41 m, 70.16 m, 70.30 m, 71.68 m, 72.95 m, 72.12 m, 76.35 m, and 65.45 m, respectively. Based on a comprehensive evaluation of flow dynamics, temperature uniformity, and transition billet length, Case 1 emerges as the most favorable single-strand closure strategy. Operational recommendations suggest avoiding strand closure patterns implemented in Cases 5 and 6 during reduced strand casting operations.

The study focuses on the four-strand tundish as the research object, aiming at the phenomenon of fewer strand casting (stable blockage) and sudden blockage of the tundish in industrial production. Numerical simulation methods are employed to compare the velocity vectors, flow fields, residence time distribution (RTD) curves, and outflow percentage curves under stable blockage and sudden blockage of the tundishes with a double-weir structure, U-shaped weir structure, and U-shaped weir structure with holes in the front. The results indicate that, after sudden blockage of the tundish strands, the flow field transitions from an unstable four-strand flow field to a stable three-strand flow field. Both the double-weir tundish and the U-shaped weir tundish reach a stable state after 200 s, while the U-shaped weir tundish with holes in the front reaches stability after 150 s. Additionally, compared to other structures, the tundish strands of the U-shaped weir with holes in the front are less affected by blockage, showing better consistency among strands and better adaptability under non-standard casting conditions.

The compromise between inclusions removal by small bubbles and proper agitation of fluid flow in tundish by gas blown is challenging. The single‐strand tundish without flow control devices (bare tundish) is used to study the effects of side‐wall gas blowing on the flow field. The water model, particle image velocity measurement and computational fluid dynamics simulation are used to study bubble behavior, fluid flow field, and tracer transport. A large horse shoe vortex and a short circuit flow at the bottom are formed in the bare tundish. Gas blowing at the outlet‐side wall of the tundish creates multiple vortices in the right‐side region, with blowing rate and position greatly influencing the surface flow within the tundish. Gas blowing at the front‐side wall creates a large spiral vortex, agitating the fluid in the tundish and improving the flow field. Increasing the blowing rate strengthens the vortex in the right region, but raising the blowing position affects surface flow and creates a counterclockwise flow toward the shroud. In all schemes, gas blowing at a low position on the front‐side wall with a small gas flowrate is the optimized scheme which shows the smallest dead volume and enhances surface flow.

The measurement of mixing time in a water model of soft-stirring steelmaking ladles is practically facing a problem of bad repeatability. This uncertainty severely affects both the understandings of transport phenomenon in ladles and the measurement accuracy. Scaled down by a ratio of 1:4, a water model based on an industrial 260-ton ladle is used. This paper studies the transport process paths and mixing time of salt solution tracers in the water model of eccentric gas-stirred ladles with a low gas flow rate. After a large number of repeated experiments, the different transport paths of the tracer and the error of the mixing time in each transport path are discussed and compared with the numerical simulation results. The results of a large number of repeated experiments on the water model show that there are five transport paths for the tracer in the ladle. The tracer of the first path is mainly transported by the left-side main circulation flow, which is identical to the numerical simulation results. The tracer of the second and third paths are also mainly transported by the left-side circulation flow, but bifurcations occur when the tracer in the middle area is transported downward. In the third path, the portion and intensity of the tracer transferring to the right side from the central region is higher than in the second path. The fourth path is that the tracer is transported downward from the left, middle, and right sides with a similar intensity at the same time. While the tracer in the fifth path is mainly transported on the right side, and the tracer forms a clockwise circulation flow on the right side. The mixing times from the first transport path to the fifth transport path are 158.3 s, 149.7 s, 171.7 s, 134 s and 95.7 s, respectively, among which the third transport path and the fifth transport path are the maximum and minimum values among all transport paths. The error between the mixing time and the averaged mixing time at each monitoring point in the five transport paths of the tracer is between −34.7% and 40.9%. Furthermore, the error of the averaged mixing time of each path and the path-based average value is between 5.5% and 32.6%.

In previous research simulating steelmaking ladles using cold water models, the dosage/volume of the salt tracer solution is one of the factors that has been overlooked by researchers to a certain extent. Previous studies have demonstrated that salt tracers may influence the flow and measured mixing time of fluids in water models. Based on a water model scaled down from an industrial 130-ton ladle by a ratio of 1:3, this study investigates the impact of salt tracer dosage on the transport and mixing of tracers in the water model of gas-stirred ladle with a moderate gas flow rate. A preliminary uncertainty analysis of the experimental mixing time is performed, and the standard deviations were found to be less than 15%. It was observed in the experiments that the transport paths of tracers in the ladle can be classified into two trends. A common trend is that the injected salt solution tracer is asymmetrically transported towards the left sidewall of the ladle by the main circulation. In another trend, the injected salt solution tracer is transported both by the main circulation to the left side wall and by downward flow towards the gas column. The downward flow may be accelerated and become a major flow pattern when the tracer volume increases. For the dimensionless concentration curve, the sinusoidal type, which represents a rapid mixing, is observed at the top surface monitoring points, while the parabolic type is observed at the bottom monitoring points. An exception is the monitoring point at the right-side bottom (close to the asymmetric gas nozzle area), where both sinusoidal-type and parabolic-type curves are observed. Regarding the effect of tracer volume on the curve and mixing time, the curves at the top surface monitoring points are less influenced but curves at the bottom monitoring points are noticeably influenced by the tracer volume. A trend of decreasing and then increasing as the tracer volume increases was found at the top surface monitoring points, while the mixing times at the bottom monitoring points decrease with the increase in the tracer volume.

在某企业生产的中高牌号DG47A(Fe-2％Si-0.36％Al-0.26％Mn)无取向硅钢热轧板中发现有长度达50 μm左右的团簇状镁铝尖晶石夹杂物,这会影响后续加工过程的产品质量.通过对BOF→RH→中间包→铸坯进行取样分析和热力学计算研究其冶炼流程中夹杂物的演变规律.采用扫描电子显微镜和能谱仪(SEM-EDS)对夹杂物的形貌、尺寸和种类进行分析,通过热力学计算了镁铝尖晶石夹杂物的生成条件,使用热力学计算软件PAN-DAT计算了该钢种凝固过程析出相变化规律.结果表明,RH脱碳后,夹杂物为SiO2;RH加铝3 min后,有Al2O3和少量SiO2夹杂物;在RH加硅铁、纯锰合金化后,出现Al2O3-MgO和含MnS的复合夹杂物;在加入脱硫剂后,出现含CaS的复合夹杂物;RH破空后,不再有单相A12O3夹杂,出现Al2O3-MgO-MnS夹杂物,并发现少量含MgS的夹杂物.中间包及铸坯中多为Al2O3-MgO-CaS和Al2O3-MgO-MnS复合夹杂物,随着浇注的进行,CaS和MnS在复合夹杂物中的含量有增加的趋势,MgO质量分数均保持为25％左右.CaS和A1N等夹杂物通常包裹在Al2O3-MgO夹杂物的外侧边缘.在铸坯中也有大量单独析出的AlN、MnS类夹杂物.RH加铝阶段,夹杂物平均尺寸为20～25 vm,RH破空后下降至2～5 μm.中间包和铸坯中,随着钢液的冷却,第二相在夹杂物表面析出,夹杂物平均尺寸为3～6μm,略有增大.热力学计算结果表明,1 873 K下当钢液中Mg质量分数大于0.000 26％时,则生成Al2O3-MgO夹杂物.钢液在冷却过程中,随着温度的降低,先后析出A1N和MnS夹杂物.

研究了苹果酸作为浸出剂和还原剂,H2O2作为辅助还原剂,还原浸出废旧锂电池中的Ni、Co、Mn等有价金属,并探讨了不同反应条件对有价金属浸出效率的影响.同时,采用溶胶-凝胶法,以浸出液为原料,原位合成了LiNi1/3 Co1/3 Mn1/3O2三元正极材料.通过X射线衍射(XRD)、扫描电镜(SEM)和电化学测试对再合成三元正极材料进行结构和电化学性能的表征.结果表明,在苹果酸浓度为2.5 mol/L、固液比120 g/L、浸出时间80 min、浸出温度90℃、H2O2用量10％(体积分数)的浸出条件下,有价金属的复合浸出率达到97.5％.同时,再合成材料具有良好的结晶性能,且再合成材料在1C充放电100次后比容量为103.4 mAh/g,容量保持率85.5％,经倍率充放电后,容量恢复率为92.32％.

Purposes In ladle metallurgy, block or whole bag alloy materials and lime are usually added. In recent years, some companies have reported a new process of adding scrap steel to ladle refining furnace. Studying the melting and homogenization mechanism of the above solid substances in the ladle refining process can optimize the refining process and accelerate production rate. Methods Ice sample and ice sphere made by KCl solution were used in the water model experiment separately to study the mechanisms of motion, melting, and mixing of alloy in a 260 t ladle. These two samples were selected to simulate the light and heavy alloys respectively. The effects of factors such as temperature, bottom blowing flow rate, liquid level height, and addition position on the mechanicms were studied. Findings The results show that the melting time of both two ice samples decreases dramatically with increasing temperature. The melting process of light ice sample (ice sphere) can be obviously accelerated by increasing the gas flowrate. When the liquid level is high, i.e. the ratio of liquid level to the diameter is 1.1, the melting time of ice sphere is relative short. The melting of ice sphere can hardly be affected by its adding position. For the heavy ice sample (salt sphere), when added from a position which is far away from the nozzle, it stays at the bottom of the ladle and melts slowly. When the salt sphere is added above the nozzle, the chances of washing by the bubbles from plume area increase and the melting time is shortened. Increasing the gas flow rate can reduce the melting time of the salt sphere, and the liquid level has a negligible effect. When the salt sphere is scoured by the bubbles in plume area, the melting time and mixing time are shortened.

The elimination of inclusions in steelmaking processes has been widely studied. The removal of inclusions by slags containing the rare earth oxide Ce2O3 are studied using an integrated numerical model. The integrated model involves the inclusion motion model, interfacial tension calculation model, surface tension calculation model of slag, and the mass action concentration model, based on ion and molecule coexistence theory. The motion behaviors of both solid Al2O3 inclusions and 50%wtAl2O3–50%wtCaO liquid inclusions of varied sizes at CaO-Ce2O3-SiO2-Al2O3(-MgO) slag systems are evaluated. The results show that it is more difficult to remove the inclusions with smaller sizes and in slag with a higher viscosity. Liquid inclusions are more difficult to remove than solid inclusions. It is found that the CaO-Ce2O3-SiO2-Al2O3-MgO refining slag shows a better ability to remove Al2O3 inclusions than that of the CaO-SiO2-Al2O3-MgO slag. The reason for this is that the addition of the rare earth oxide Ce2O3 can decrease the viscosity of slags, as well as improving the wetting effects of slags on Al2O3 inclusions. For two slags systems, the CaO-Ce2O3-SiO2-Al2O3-MgO slag system shows a better ability to remove Al2O3 inclusions than the CaO-Ce2O3-SiO2-Al2O3 slag system. The addition of 5% to 8% Ce2O3 in a CaO-SiO2-Al2O3-MgO slag is an optimized case for industrial applications.

采用溶胶-凝胶法制备出不同Fe掺杂量的LaCo1-xFexO3,并将其作为锌-空气电池的空气电极活性材料.分别通过XRD、SEM以及电化学测试研究了其形貌结构和电催化性能.结果表明,当Fe取代量超过50％时,LaCo1-x Fex O3的晶体结构由菱面体开始转变为立方体.其中,LaCo0.5 Fe0.5 O3颗粒均匀,晶粒尺寸达到纳米级别,在-0.7 V电位下,表现出了最大的极化电流密度4.92 mA·cm-2.将LaCo0.5 Fe0.5 O3应用于锌-空气电池空气电极中,在1mA恒定电流下,放电电压稳定在1.2V.在80个循环后,充放电压差为0.85V,往返效率保持在57.2％,优于L aC o O 3的0.95 V和52.0％.

The flow field, tracer dispersion and uniformity of strands in two designs of four-strand tun-dishes under normal conditions and single-strand blockage conditions are studied by numerical simulation. The casting speed (flow rate) of strands are increasing uniformly or non-uniformly to improve the strand blockage condition. The uniformity of strands of the cases are evaluated by a novel outflow percentage analysis method. The results show that the flow field in the tundish does not change significantly when the single-strand is blocked or the casting flow rate is increased. After blockage of one strand, the consistency of each strand of u-shaped weir tundish is better than that of double-weir tundish. With the uniform increasing of the casting flow rate, the response time of each strand decreases and the outflow percentage increases. However, the uniformity of strands improved slightly in double-weir tundish but decreased in u-shaped tundish. For the double-weir tundish, significantly increasing the casting flow rate of the strand located in the blocked part by a factor of 1.5 and slightly increasing the casting flow rate of the other strands by a factor of 1.25, the consistency of each strand is the best. For the u-shaped weir tundish, the consistency of each strand is improved by non-uniform increasing of the casting flow rate of the strands. The flow rate of the strand located in the blocked part and the other strands is increased by a factor of 1.25, and 1.375 or 1.2 and 1.4 are the optimized cases.

The improvement in mixing conditions in a vacuum refining unit plays an important role in enhancing the purity and decarburization of molten steel. Mixing time is an important index to evaluate the operation efficiency of a metallurgical reactor. However, in water models, the effect of salt tracer dosages on the measured mixing time in a vacuum reactor is not clear. In this study, a water model of a Single Snorkel Refining Furnace (SSRF) was established to study the effect of salt solution tracer dosages on the mixing time of monitor points. The experimental results show that, in some areas at the top of the ladle, the mixing time decreases first and then increases when increasing the tracer dosage. Numerical simulation results show that, when the tracer dosage increases, the tracer flows downwards at a higher pace from the vacuum chamber to the bottom of the ladle. This may compensate for the injection time interval of large dosage cases. However, the mass fraction of the KCl tracer at the right side of the bottom is the highest, which indicates that there may be a dead zone. For the dimensionless concentration time curves and a 99% mixing time, at the top of the vacuum chamber, the curve shifts to the right side and the mixing time decreases gradually with the increase in tracer dosage. At the bottom of the ladle, with the increase in tracer dosage, the peak value of the dimensionless concentration time curve is increased slightly. The mixing time of the bottom of the ladle decreases significantly with the increase in tracer dosage. However, in the dead zone, the mixing time will increase when the tracer dosage is large. At the top of the ladle, the effect of the tracer dosage is not obvious. The mixing time of the top of the ladle decreases first and then increases when increasing the tracer dosage. In addition, the mixing time of the top of the ladle is the shortest, which means that sampling at the top of the ladle in industrial production cannot represent the entire mixing state in the ladle.

采用光学显微镜、扫描电镜、电子万能试验机、数显显微硬度计,研究了一步法淬火配分(Q&P)工艺和热轧一步法淬火配分(HR-Q&P)工艺在不同配分温度下处理后Q235钢的组织和力学性能.结果表明:HR-Q&P工艺使试验钢晶粒明显细化,显微组织由马氏体、铁素体和贝氏体组成,在350℃配分下,屈服强度和抗拉强度都达到最大值,分别为449 MPa和560 MPa,伸长率与原样相比下降了8％,但仍然超过30％;硬相的马氏体和贝氏体的同时出现,导致断口出现二次裂纹;一步法Q&P工艺下,与未处理试验钢相比,抗拉强度提高约32％,屈服强度提高近1倍,伸长率保持在26％以上.

为了提高精品课程的建设质量,对冶金传输原理实验教学环节进行改革,通过优化实验内容、加强实验过程管理和确立科学考核办法等途径,提高了学生实验主观能动性,激发了学生的科研创新能力,确保了实验教学效果.