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自2000年以来,在一些发动机工程中使用的铸铁缸套已在轻质金属曲轴箱内孔热喷涂铁基涂层所取代。相对于直接浇铸缸套,没有缸套的Al曲轴箱对其内孔区域的孔隙及抗拉强度具有更高要求。在铸造过程中,铸造体中最大孔隙的直径要控制在不能超过1mm2,以避免在机械粗化(MR)或高能水射流粗化(WR)工艺中刀具损坏(MR)或孔隙扩张(WR)。在NemakDillingen,这些困难被内孔组处理(CPS)技术所克服,并拥有高度灵活的铸造设计及几乎不受限制地选择铸造合金等优点。这些边界特性使得采用具有高强度及抗蠕变的Al-Si-Cu基二次合金A319制备轻质曲轴箱成为可能。通过对凝固铸造环境的细致热学设计获得了具有高质量的圆柱内孔表面。圆柱冷铁会在固化初始阶段形成稳定及致密的壳层,而补给在曲轴箱的侧墙结构进行。同时,为轴承座特殊设计的冷铁能够确保极短的固化时间,最终性能对承受重载荷的柴油发动机置关重要。在铸造和机械加工后,曲轴箱被机械粗化并喷涂0.8%碳钢。通过光学显微镜观察涂层及其与铸造Al基体的界面,研究涂层与基体的结合及铸造金属近表面的孔隙结构。
Cast iron cylinder liners used in some engine engineering have been replaced by thermal sprayed iron-based coatings in the bore of lightweight metal crankcases since 2000. Al-crankcase without cylinder liner has higher requirements on the porosity and tensile strength of its inner bore area than direct cast liner. During casting, the maximum pore size in the casting should be controlled not to exceed 1 mm2 to avoid tool damage (MR) or pore expansion (WR) during mechanical roughening (MR) or high energy water jet roughening (WR) . At Nemak Dillingen, these difficulties were overcome by the CUP technology, with the advantages of a highly flexible casting design and almost unlimited choice of casting alloys. These boundary characteristics make it possible to produce lightweight crankcase using Al-Si-Cu based secondary A319 with high strength and creep resistance. Through the meticulous thermal design of a solidified casting environment, a cylindrical bore surface of high quality is obtained. Cylindrical chill iron will form a stable and dense shell in the initial stage of cure, while replenishment takes place in the side wall structure of the crankcase. At the same time, chilled iron, specially designed for the housing, ensures extremely short curing times and the final performance is crucial for heavy-duty diesel engines. After casting and machining, the crankcase was mechanically roughened and sprayed with 0.8% carbon steel. The coating and its interface with the cast Al substrate were observed by light microscopy to study the bond between the coating and the substrate and the pore structure of the near-surface of the cast metal.