ZL205A合金半连续铸锭夹渣缺陷的研究

Study on Slag Defects in ZL205A Aluminum Alloy Ingots Produced by DC Casting

以实际生产过程中的ZL205A合金Φ400 mm半连续铸锭在射线探伤检测时发现的夹渣缺陷为研究对象,采用X射线探伤机、金相显微镜、电子探针等手段对夹渣缺陷的产生原因进行分析,提出了新的半连续铸造工艺方案。结果表明:在熔体温度不超过800℃情况下,ZL205A合金的Ti元素溶解极限在0.14%～0.15%,剩余Ti元素作为未溶Al3Ti化合物悬浮在铝液中,在半连续铸造过程中,铝熔体在过滤槽和结晶器托盘中无法搅拌,未溶Al_3Ti发生沉淀、团聚,产生粗大金属化合物,宏观上表现为夹渣缺陷。铸造工艺改进后,Ti元素以0.15%铝钛中间合金+0.02%的铝钛硼丝的方式加入,所生产铸锭夹渣缺陷消除,X射线检验满足了Ⅰ类件要求,铸锭本体抗拉强度达到了464 MPa。

With taking the slag defects as the research object, which were found in the ZL205A aluminum alloy ingots of φ400 mm in diameterby the X-ray detection, the causes to generate these defects were analyzed by means of the X-ray flaw detector, metallographic microscope and electron microprobe, and a new direct chill （DC） casting process was proposed. The results show that the solubility limit of Ti element in ZL205A alloy is 0.14%-0.15% under the condition that the temperature of the molten aluminum alloy does not exceed 800℃, and the residual Ti element is suspended in the molten aluminum as the undissolved A13Ti compound. In the DC casting process, the molten aluminum cannot be stirred in the filter tank and in the crystallizer pallet, and the undissolved Al3Ti compound is liable to be precipitated and agglomerated, resulting in the formation of coarse metallic compounds, which are displayed as the slag inclusion defects in the ZL205A alloy ingots from the macro perspective. After the new DC casting process is carried out, in which Ti element is added in the aluminum melt in the manner of 0.15% Al-Ti master alloy and 0.02%; AlTiB wires, the slag inclusion defects are eliminated in the ingots and the X-ray inspection of them meets the requirements of Class I castings and the tensile strength property of the ingots is up to 464 MPa.