共查询到20条相似文献,搜索用时 62 毫秒
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连铸过程中的奥氏体晶粒尺寸会显著影响铸坯的热塑性,铸坯表面裂纹缺陷也往往与粗大奥氏体的形成有关。实验研究了将铸坯重新加热至1 350 ℃后保温时间对石油套管J55钢奥氏体晶粒尺寸的影响。结果表明,随着保温时间的增加,奥氏体晶粒尺寸变大。综合分析表明,对于J55钢,在1 350 ℃时至少保温30 min才能使其晶粒尺寸达到连铸过程中当时的奥氏体晶粒级别。以往采用高温热拉伸实验模拟测量铸坯高温热塑性实验中,多未考虑连铸过程中的实际奥氏体晶粒大小,实验结果不能很好地反映高温铸坯的热塑性。 相似文献
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建立连铸坯凝固传热数学模型,利用现场实测数据对所建模型进行了验证,并对影响铸坯温度和坯壳厚度的拉坯速度、浇注温度、二冷区水量等因素进行了分析。结果表明:模型的计算精度满足实际生产的需要,影响因素中,拉坯速度和二冷区水量对铸坯温度和坯壳厚度的影响最大。因此调节拉速,改善二冷区制度是铸坯生产工艺中的重要操作。 相似文献
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Turbines fired with hydrogen or syngas from coal gasification will have significantly higher water vapor contents in the combustion gas than natural gas fired turbines. The effect of increased water vapor on alumina-forming coatings and model alloys was investigated at 1100 °C in furnace cyclic testing. Increasing the water vapor content from 10% to 50 vol.% increased the amount of scale spallation on undoped alumina-forming alloys. Compared to dry O2, increased spallation was observed for β and γ/γ' phase coatings on the substrates of alloys 142 and N5. In all cases, the addition of water vapor appeared to reduce the formation of alumina whiskers and ridges at the scale-gas interface, but did not significantly change the alumina growth rate. The addition of water vapor may have a detrimental effect on the selective oxidation of Al in γ/γ' alloys and coatings. 相似文献
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B.A. Pint G.W. Garner T.M. Lowe J.A. Haynes Y. Zhang 《Surface & coatings technology》2011,206(7):1566
To investigate the effect of increased water vapor levels on thermal barrier coating (TBC) lifetime, furnace cycle tests were performed at 1150 °C in air with 10 vol.% water vapor (similar to natural gas combustion) and 90 vol.%. Either Pt diffusion or Pt-modified aluminide bond coatings were applied to specimens from the same batch of a commercial second-generation single-crystal superalloy and commercial vapor-deposited yttria-stabilized zirconia (YSZ) top coats were applied. Three coatings of each type were furnace cycled to failure to compare the average lifetimes obtained in dry O2, using the same superalloy batch and coating types. Average lifetimes with Pt diffusion coatings were unaffected by the addition of water vapor. In contrast, the average lifetime of Pt-modified aluminide coatings was reduced by more than 50% with 10% water vapor but only slightly reduced by 90% water vapor. Based on roughness measurements from similar specimens without a YSZ coating, the addition of 10% water vapor increased the rate of coating roughening more than 90% water vapor. Qualitatively, the amount of β-phase depletion in the coatings exposed in 10% water vapor did not appear to be accelerated. 相似文献
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王文学杨超武曾晶梁龙王蓉 《连铸》2017,36(3):21-24
结合304奥氏体不锈钢高温凝固特性及现场连铸浇铸参数,分析304不锈钢连铸铸坯内外弧宽度尺寸相差约为4~7 mm的具体原因,如结晶器内外弧冷却不同、内外弧铜板锥度不同、水口不对中等。详细研究因结晶器内外弧冷却不同对铸坯内外尺寸的影响,实践证明,调整结晶器内外弧水量可以有效改善内外弧铸坯尺寸差异问题。 相似文献
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水的属性对石膏型性能的影响 总被引:3,自引:0,他引:3
在固定石膏品种及制备工艺的条件下,研究了水温从20℃至50℃,地下水、蒸馏水、磁化水等不同水质对石膏性能的影响。试验表明:随着水温的上升,石膏浆体的流动性下降,胶凝硬化时间缩短,硬化体的强度、收缩增加。蒸馏水及磁化水均使石膏硬化后强度显著增高,收缩明显加大,对石膏浆体的流动性及胶凝特性影响较小。 相似文献
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综述了纯水溢流阀工作稳定性的研究成果,对纯水溢流阀工作稳定性进行了计算机仿真分析,结果表明:工作介质、阀口直径、阻尼力、供液流量及主阀弹簧刚度是影响纯水溢流阀工作稳定性的重要因素. 相似文献
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Shu-Yong Zhang Yi-Fu DingShan-Jun Li Xiao-Wen LuoWei-Fang Zhou 《Corrosion Science》2002,44(4):861-869
Two epoxy resins, EP and EPA, with similar backbone structure but different water affinity, was obtained by curing o-cresol novolac epoxy resin with phenol novolac resin and phenol novolac acetate resin, respectively. By using these two resins, the effect of the polymeric structure on the corrosion protection of the coatings was studied. The free volume in EPA is larger than that in EP as demonstrated by room-temperature density measurement and positron annihilation, while water sorption of EPA is only half of that of EP. Therefore, water affinity of the resin is more important in determining water sorption of the resin than free volume. The cross-sectional area of water passage at coating/metal interface (Aw) was estimated using the electrochemical impedance spectroscopy and compared with that in the resin matrix (Acs). It was found that, for EPA, Aw is much less than Acs, which suggests a significant narrowing of water passage at the coating/metal interface. This narrowing of water passage at coating/metal interface due to the formation of a hydrophobic layer can greatly improve the corrosion protection of the coating. 相似文献