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Fabrication of Thin Aluminum Alloy Slab and Technological Development for Its Application

铝合金薄板坯的制备及其应用技术开发

基本信息

批准号：
10555228
负责人：
KAMADO Shigeharu
金额：
$ 1.73万
依托单位：
Nagaoka University of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

The main purpose of this study is to fabricate a thin aluminum alloy slab using electromagnetic casting(EMC), which will enable us to make a thin plate only by cold rolling without hot rolling and intermediate annealing, . Firstly relationships between outward appearances and manufacturing conditions were investigated. Fabrication of billets as raw materials for semi-solid forming were also tried to confirm the characterization of EMC.Furthermore, mechanical properties of the rolled plates and the semi-solid formings manufactured using the EMC slabs and billets were evaluated. Obtained results are summarized as follows ;(1) At the early stage of continuous casting the meniscus thickness largely depends on the thickness of bottom block and as a result the fabricated slab thickness is nearly equal to the thickness of bottom block. When the thin slab is fabricated under a casting speed of 960mm/min and a water cooling rate of 20L/min, it has a uniform thickness of 7mm, smooth surface and … More equiaxed grains. Application of EMC to the fabrication of thin slab makes the microstructure to be very fine up to dendrite arm spacing of 10μm due to a large cooling rate caused by the thin thickness and direct water cooling. Such a fine microstructure leads to a good rolling ability up to the rolling ratio of 75% with no edge cracks.(2) Crystallized compounds increase with increase in Fe content and cooling rate, but the tensile properties of the rolled thin plate are improved because the compounds are fine and distribute uniformly and, therefore, useful for the dispersion strengthening and for refining the recrystallized grains. As a result, even when 5052 aluminum alloy contains a large amount of Fe as an impurity, tensile properties of heat-treated sheets of directly cold rolled EM cast thin slabs satisfy JIS requirements if Mg content is reduced to 2.05% which is smaller than the lower limit specified by JIS for 5052 aluminum alloy. This indicates that the application of EMC to the fabrication of the thin slab is very useful for reduction of bad influences by impurities.(3) Addition of a grain refiner and application of EMC process ensures the production of sound billets with fine and equiaxed grain throughout the entire structure. Upon semi-solid forming using the billets at optimum temperatures, fine and nearly spherical solid particles distribute uniformly throughout the formed specimens and an increase in fluidity even for thin parts are observed for all investigated alloy. Furthermore, tensile properties of T6-treated specimens of semi-solid formed samples of 7475 and A357 aluminum alloys are close to those of the forged samples of 7475 wrought alloy and A357 casting aluminum alloy sample thixocast using billets fabricated by DC casting with electromagnetic stirring, respectively. Less

本研究的主要目的是利用电磁铸造（EMC）制造薄板铝合金，使我们能够只进行冷轧而不进行热轧和中间退火。首先研究了外观与制造条件的关系。同时，还尝试了半固态成形坯料的制备，以确定电磁兼容的特性。此外，还评估了用电磁干扰板和钢坯制造的轧制板和半固态成形件的力学性能。所得结果总结如下：(1)在连铸初期，半月板厚度在很大程度上取决于底块的厚度，因此铸坯的厚度几乎等于底块的厚度。当浇铸速度为960mm/min，水冷速度为20L/min时，薄板坯厚度均匀，为7mm，表面光滑，晶粒等轴性好。采用电磁兼容技术制备薄板，由于薄板厚度较薄且直接水冷却导致冷却速率大，使得组织非常精细，枝晶臂间距可达10μm。良好的微观组织使其具有良好的轧制性能，轧制率可达75%，且无边缘裂纹。(2)随着铁含量的增加和冷却速度的增加，结晶化合物增加，但由于这些化合物细小且分布均匀，有利于弥散强化和再结晶晶粒的细化，使轧制薄板的拉伸性能得到改善。结果表明，即使5052铝合金中含有大量的Fe杂质，当Mg含量低于5052铝合金的最低标准值2.05%时，直接冷轧EM铸薄板热处理板材的拉伸性能仍能满足JIS的要求。这表明电磁兼容在薄板制造中的应用对于减少杂质的不良影响是非常有用的。(3)晶粒细化机的加入和电磁兼容工艺的应用，保证了整个结构中晶粒细小等轴的良好坯料的生产。在最佳温度下使用坯料进行半固态成形时，细小且接近球形的固体颗粒均匀分布在整个成形试样中，并且在所研究的所有合金中观察到即使是薄零件的流动性也有所增加。7475铝合金半固态成形试样和A357铝合金半固态成形试样经t6处理后的拉伸性能分别接近于7475变形合金和A357铸造铝合金电磁搅拌小方坯的锻件的拉伸性能。少