基于质点逆向追踪的铝合金空心型材横断面温度的不均匀性

采用挤压金属质点逆向追踪方法,分析了铝合金空心型材挤压过程中型材横断面温度分布不均匀性的原因及主要影响因素。结果表明:挤压过程中质点在分流孔内流动时的温度变化对模孔出口处型材横断面温度分布不均匀性的影响较大,而在焊合室内和模孔内流动时,温度变化对模孔出口处型材横断面温度分布不均匀性影响较小;挤压过程中各项热流作用对型材横断面温度分布不均匀性的影响程度由大到小依次为摩擦热、塑性变形热以及金属与工模具间的传热;通过模具结构设计和挤压工艺参数合理化,可使空心型材横断面温度分布的不均匀性得到较大的改善。     

过氧化叔戊醇对苯并噻吩类衍生物的氧化

Homogeneous oxidation using an oil-soluble oxidant, tert-amyl hydroperoxide (TAHP), for ultra-deep desulfurization was performed under mild conditions in the presence of molybdenum oxide catalysts. Dibenzothio-phene (DBT), benzothiophene (BT) and 4, 6-dimethyl-dibenzothiophene (DMDBT), which are the refractory sulfur compounds for hydrodesulfurization (HDS), were employed as model substrates for a simulated diesel fuel. Activ-ity of molybdenum oxide supported on a macroporous weak acidic resin was investigated. The mass conversion of DBT reached near 100% at 90°C and a TAHP/DBT molar ratio of 3 with 1% of molybdenum oxide supported on Amberlite IRC-748 resin for 1 h. It was further found that the activities of the model substrates decreased in the or-der of DMDBT＞DBT＞BT. In the flow oxidation using TAHP as the oxidant, mass conversion of DBT increased remarkably from 61.3% to 98.5% when dropping the weight hourly space velocity (WHSV) from 40 h－1 to 10 h－1. A series of experiments dealt with selectivity of this oxidation using TAHP revealed that the model unsaturated compounds, i.e. 4, 6, 8-trimethyl-2-nonylene, and 2-methylnaphthalene did not affect the oxidation of DBT. Car-bazole had nearly no effect on the conversion of DBT using TAHP, but had some influence on the one using tert-butyl hydroperoxide (TBHP). The mass conversion of DBT decreased remarkably from 75.2% to 3.6% when the content of carbazole increased from 0 to 500 μg•g－1. In the flow oxidation using TAHP as the oxidant, the con-centration of DBT in model fuels was reduced from 500 µg•g－1 to 7.2 µg•g－1 at WHSV of 10 h－1, and then reduced to 3.8 µg•g－1 by adsorption of Al2O3.     

停放时间对2024铝合金挤压型材力学性能影响

在495℃固溶保温50 min和175℃时效保温10 h工艺条件下,研究了停放时间对2024铝合金挤压型材力学性能的影响。实验结果表明:在该工艺条件下,淬火后停放8 h进行时效处理,2024铝合金挤压型材的屈服强度、抗拉强度、断后伸长率均达到最大值。结合实际生产效率,2024铝合金挤压型材淬火后应在8 h内进行时效处理。     

环缝式电磁搅拌对7N01合金连铸锭组织的影响

实现7N01铝铸锭组织细化均匀化是解决型材产品成材率低、力学性能不稳定、表面桔皮、条纹等缺陷问题的关键,为此开展了7N01铝合金铸锭环缝式电磁搅拌半连续铸造技术的研究。结果表明,施加环缝式电磁搅拌后,310mm规格的7N01合金连铸锭晶粒尺寸细化至200~300μm范围内,较普通铸锭晶粒尺寸降低了90%;晶粒自边部至心部尺寸分布范围由普通铸锭的800~3 200μm下降到施加环缝式电磁搅拌后的200~300μm内,均匀性得到显著改善;同时消除了普通铸锭易出现的粗大树枝晶等铸造缺陷,大大提高了铸锭质量。     

Cu、Mg对Al-Cu-Mg-Fe-Ni合金组织性能影响

随着铝合金行业发展,Al-Cu-Mg-Fe-Ni高强耐热型铝合金的需求越来越大。本文主要研究在确保耐热性能的前提下,通过调整合金中Cu和Mg元素的含量,改善组织来提高合金强度,最终通过试验确定最高耐热强度时Cu和Mg元素的含量。     

Fe、Ni元素对2A12铝合金组织和性能的影响

铸造过程中在2A12铝合金中加入Fe、Ni元素,分析了Fe、Ni元素对合金显微组织的影响。将加入和未加入Fe、Ni元素的合金试样置于不同的高温环境中,测量其高温性能,比较分析Fe、Ni元素对2A12铝合金高温性能的影响。结果表明Fe、Ni元素的加入可以提高合金的力学性能和高温性能。     

低体积分数铝基碳化硅强化的复合材料薄壁型材挤压工艺研究

铝基碳化硅(SiCp/Al)强化的复合材料具有较高的比强度、耐磨性,同时材料的流动性很差,挤压成型难度较大,型材表面极易出现挤压裂纹。本文通过对挤压温度、挤压速度等参数进行对比试验,结合最终的型材外形质量,提供适合的挤压工艺参数。