共查询到19条相似文献,搜索用时 203 毫秒
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低碳钢铸坯在连铸过程中表面容易产生夹渣缺陷。通过增加保护渣中MgO、MnO、Al2O3等的含量,可在提高保护渣黏度的同时加大保护渣的表面张力以及钢-渣界面张力,有利于钢、渣分离。根据经验公式η1 300℃·Vc=0.1~0.35以及武钢炼钢总厂四分厂连铸机拉速为1.3 m/min的实际情况,将试验保护渣黏度设计值由0.13 Pa·s提高到国内外专家要求的最大值0.25 Pa·s,连铸坯轧制钢材表面夹渣率由50%大幅度下降到20.5%。为了进一步降低夹渣率,根据试验情况及国内外保护渣设计理念,再次将保护渣的黏度由0.25 Pa·s提高至0.45 Pa·s,同时引入含量2%的Li2O,以改善传热条件,保证良好的润滑效果,实现保护渣均匀地消耗凝固,为坯壳均匀形成创造更有利的条件。最终将钢材表面夹渣率降到0.35%,提高了连铸坯及轧材合格率,满足了客户需求。 相似文献
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谭宏斌 《有色金属(冶炼部分)》2012,(3):47-49
以硝酸铝、氯氧化锆和酒石酸为原料,聚乙烯吡咯烷酮(PVP)为纺丝助剂,用溶胶—凝胶法制备了氧化锆/氧化铝复合纤维。结果表明,凝胶纤维的长度随PVP掺量增加而增加,凝胶纤维最大长度为60cm;凝胶纤维在1 200℃烧结后,纤维的物相为α-Al2O3和四方ZrO1.88,纤维的直径为4μm,纤维表面光滑,直径均匀。 相似文献
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采用溶胶-凝胶法制备了钇铝石榴石(YAG)纤维,并研究了YAG溶胶的粘度和纺丝性、红外吸收特征和热分解特性,分析了YAG纤维的物相结构和微观形貌。结果表明:当YAG溶胶的固含量为26%~28%、纺丝温度为20℃时,YAG溶胶纺丝性最佳;YAG溶胶中存在大量的Al—OH和Y—OH基团,二者之间失水可缩聚成大分子链,宏观表现出纺丝性;YAG溶胶热处理中失重主要发生在600℃之前。采用溶胶-凝胶法可获得单一相的YAG纤维;随着煅烧温度的升高、时间的延长,YAG纤维晶粒不断长大,晶粒之间的孔洞也逐渐增多、增大,导致纤维性能下降。 相似文献
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《稀有金属与硬质合金》2017,(4)
利用非水基体系凝胶注模法制备了复杂形状钨铜复合材料坯体。研究了分散剂含量以及固相含量对钨铜浆料黏度的影响,绘制了坯体的室温干燥曲线并制订了干燥制度,同时对坯体微观形貌、抗弯强度等进行了表征和测试。结果表明:分散剂添加量为0.15%(质量分数,基于金属粉末质量)时浆料黏度达到最低,在此基础上浆料的固相含量可达到45%(体积分数),满足凝胶注模的要求;坯体先在室温下干燥10h后放入100℃的恒温干燥箱中干燥8h,可得到表面无变形、无开裂的钨铜坯体;随着固相含量的增大,坯体致密性和均匀性均随之提高;坯体表面质量较好,抗弯强度可达到26.9 MPa。 相似文献
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在93W-4.9Ni-2.1Fe混合料中添加0.3%(质量分数)的长2~3 mm、直径15μm的钨纤维,在单柱液压机上反复挤出,获得直径12 mm的棒坯。采用扫描电镜和光学电镜观察棒坯断口和表面形貌,研究挤压次数、挤压料温度和挤压速度对挤压棒坯表面形貌和微结构的影响,并对挤压料的均匀性、流变性、钨纤维的定向排布进行研究。结果表明:通过多次挤压可以提高挤压料中增塑剂分布的均匀性。当挤压料温度为50℃时由于挤压料黏度小,增塑剂与粉末结合强度低,挤压料挤出不能成形;挤压料温度为35℃时,挤压料可挤出棒坯,但棒坯表面光洁度很差;挤压料温度为20℃时,挤压料挤出棒坯表面光洁度高,没有开裂和鼓泡现象。挤压速度为15 mm/s时,挤出棒坯表面光滑。粉末挤压可使挤压料中原来错综杂乱的钨纤维沿挤压方向实现一维定向排布。 相似文献
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溶胶-凝胶法制备钇铝石榴石纤维 总被引:3,自引:3,他引:0
以氯化铝、金属铝粉、氧化钇、冰醋酸为原料,采用溶胶—凝胶法制备了钇铝石榴石纤维。研究氯化铝和金属铝粉比例以及醋酸的加入,对前驱体溶胶纺丝性能的影响。结果表明,加入醋酸可得到纺丝性能良好的前驱胶体溶胶。凝胶纤维在1 000℃煅烧2 h,全部结晶为钇铝石榴石,纤维直径10~40μm。 相似文献
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溶胶—凝胶法微晶氧化锆纤维的研究 总被引:1,自引:0,他引:1
溶胶—凝胶法制备氧化锆纤维其结构的均与微晶化对使用性能至为重要,近年来,对此研究报道较多。通常以Y_2O_3为稳定剂的Y-PSZ纤维经过一定热处理过程可获得≤0.5 μm晶粒度的微晶结构。 采用溶胶—凝胶法制备氧化锆陶瓷材料,当进行热处理时锆质凝胶无机高分子转化成的无定形ZrO2将逐步晶化。本文对3.6 mol%Y_2O_3-ZrO_2纤维的制备及热处理中晶化现象进行了研究,并初步探讨了晶核剂的加入对晶化的影响。所制Y-PSZ纤维直径5~1μm,1400 ℃处理2h后,晶相为t-ZrO_2。和极少量m-ZrO2,晶粒度均小于0.1 μm。 相似文献
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Blast furnace slag is the main byproduct in the ironmaking process, which contains large amounts of sensible heat. In addition, it's the major raw material for cement. However, the sensible heat is wasted not only without any recovery in the traditional water granulation process at this present. The main challenge is to granulate the slag at a high cooling rate while the heat is also being recovered. This paper describes the hot experiments where a rotating multi‐nozzle cup atomizer (RMCA) is used to atomize the molten blast furnace slag without water impingement. The atomization process shows good agreement with Rayleigh's mechanism. The particle size of the slag particle is strongly controlled by the rotating speed and the nozzle diameter, and the higher rotating speed and smaller nozzle diameter are beneficial for obtaining smaller and more uniform slag particles. Moreover, the slag particle still has a high content of glass, which is suitable for cement manufacture. 相似文献
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Viscosities Behavior of CaO-SiO2-MgO-Al2O3 Slag With Low Mass Ratio of CaO to SiO2 and Wide Range of Al2O3 Content 总被引:1,自引:0,他引:1
The present paper is aimed at recycling of coal ash and blast furnace slag to produce mineral wool. Considering the mineralogical constitutions of coal ash and blast furnace slag, the primary quaternary slag compositions of CaO-SiO2-MgO-Al2O3 with basicity (mass ratio of CaO to SiO2) ranging from 05 to 09 and alumina ranging from 5% to 20% were investigated through a rotating cylinder method. The experimental results indicated that the viscosities decreased with increasing basicity above the liquidus temperature, and increased with increasing alumina content, and the maximum values were reached and as the alumina content was 20%, followed by the decrease with further increasing alumina content due to its amphoteric behavior. The amphoteric behavior of Al2O3 also performed in the relationship between viscosity and non-bridging oxygen per tetrahedrally-coordinated atom (NBO/T), and the viscosities decreased with increasing the NBO/T except the slag with a basicity 05 and Al2O3 20% which have a low NBO/T value and a low viscosity than others.- 相似文献
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Y Wakisaka Y Okuzono Y Taenaka K Chikanari T Masuzawa T Nakatani E Tatsumi T Nishimura Y Takewa T Ohno H Takano 《Canadian Metallurgical Quarterly》1997,21(7):651-654
A flow rate estimating method was investigated for a centrifugal blood pump developed in our institute. The estimated flow rate was determined by the power consumption, the rotating speed of the motor, and the hematocrit value. The power consumption and the rotating speed of the motor were measured with a wattmeter. The examinations were performed in a closed mock loop filled with goat blood with hematocrit values of 21.5%, 28%, 34%, and 42%. Measured values of blood viscosity were 2.47, 3.09, 3.71, and 5.07 mPa.s at a share rate of 37.5/s, respectively. A linear correlation between the power consumption and the pump flow rate was observed in all hematocrit values. But variations in hematocrit caused a difference in the flow rate up to 1.1 L/min at the same power consumption and rotating speed. Effects of blood viscosity on the flow estimation were corrected by the hematocrit value. The value of the coefficient of determination, R2, between the estimated flow rate and the measured flow rate was 0.988. These results may indicate that the flow estimating method calculated by the power consumption of the motor, the rotating speed, and the hematocrit value is useful in the clinical situation. 相似文献
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Infiltration experiments on aluminum cast into SAFFIL alumina fiber preforms containing a silica binder and of fiber volume
fraction varying from 10 to 25 pct are reported. Data are compared with the theory presented in Part I and used to characterize
wettability of the preforms by plotting the infiltrated length of composite divided by the square root of time as a function
of applied pressure. The intercept of the resulting curves with the abscissa axis is shown to be a measurement of the capillary
pressure needed to fully infiltrate the fiber preforms. Resulting experimental values of this capillary pressure are then
used with Brunauer, Emmett, and Teller (BET) adsorption isotherm measurements of the preform’s specific surface to derive
an apparent wetting angle of the fibers by aluminum during infiltration. In this manner, the effective wetting angle of pure
aluminum on the alumina/silica fibers is found to be 106 ±5 deg, independent of fiber preform temperature. We also propose
a mechanism for preventing preform compression during infiltration.
Formerly Undergraduate Student with the Department of Materials Science and Engineering, Massachusetts Institute of Technology. 相似文献
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S. Nourbakhsh O. Sahin W. H. Rhee H. Margolin 《Metallurgical and Materials Transactions A》1991,22(12):3059-3064
A pressure-cast NiAl composite reinforced with polycrystalline alumina (PRD-166) fibers containing 0.2 weight fraction of
partially stabilized zirconia was examined by optical and transmission electron microscopy (TEM). Fibers in the preform used
for casting were forced into contact, and fiber bonding occurred in a number of instances. Fiber volume fraction was increased
from an initial value of 0.4 to 0.6 as a consequence of the applied pressure. An explanation is offered for the interaction
of applied pressure, wetting angle, and the rigidity of the fiber preform on the final volume fraction of the fibers in the
composite. At the fiber/matrix interface, the alumina was free of zirconia particles. It is proposed that alumina grain growth
forced the zirconia into the molten NiAl, where it dissolved. As solidification took place, the concentration of zirconium
in the molten NiAl increased to a point where zirconium reacted with alumina to form zirconia again. 相似文献
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针对攀钢V和V-Nb微合金化低碳梁板钢200 mm连铸坯出现角部横裂纹缺陷,通过综合优化连铸工艺参数-将结晶器铸坯窄宽面热流比由原先的0.90~1.10降至0.75~0.85,保护渣的粘度由0.20 Pa • s降至0.16 Pa • s,稳定连铸拉速和连铸机工况条件,使铸坯角部横裂纹缺陷得到了明显改善,并消除了由此引起的热轧饭卷表面线纹和起皮缺陷,因梁板钢热轧板卷表面缺陷引起的降级改判率由30%降至0。 相似文献
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V. J. Michaud A. Mortensen J. L. Sommer 《Metallurgical and Materials Transactions A》1999,30(2):471-482
Infiltration by a pure matrix in the presence of preform deformation and partial matrix solidification is analyzed using a
bounding approach for the preform rheology where solid metal is present. It is found, using parameters for the infiltration
of short alumina fiber preforms by aluminum, that the two bounds are close in comparison to other factors of uncertainty in
the prediction of infiltration rate. Using this approach, preform compression is shown to exert a significant influence on
the infiltration rate for the system explored; in particular, the analysis shows the existence of an optimal value of applied
pressure. Simplifications in the analysis are also presented, which yield fairly accurate results while easing their computation
significantly. 相似文献