(1.甘肅工業(yè)大學 材料科學與工程學院, 蘭州 730050;
2. 華中科技大學 材料科學與工程學院, 武漢 430074)
摘 要: 對5種典型鋅鋁合金在熱型連鑄工藝條件下的連續(xù)定向凝固進行了研究，探討該工藝下鋅鋁合金線材表面缺陷的產生機理，并對部分缺陷的組織結構進行了顯微分析。結果表明：只有金屬液壓頭、型口溫度、拉鑄速度和冷卻條件諸工藝參數(shù)在一定范圍內的協(xié)調配合，才能拉鑄出表面光滑的鋅鋁合金線材。不合理的工藝參數(shù)將導致熱裂、表面粗糙、糊狀型口和拉漏等缺陷。固液兩相區(qū)的形狀和位置對上述缺陷的形成有重要影響，當固液兩相區(qū)位于型口或型內時，凝固界面將向型內凸入，如果剩余液體不能抵消凝固收縮，就會出現(xiàn)表面粗糙；若凝固界面深入型內較多，則使型內凝固的鑄錠摩擦力過大，形成熱裂；固液兩相區(qū)移至型外，凝固界面將變成平面，容易發(fā)生拉漏。
關鍵字: 連續(xù)鑄造； 定向凝固； 加熱鑄型；鋅鋁合金； 缺陷
made in continuous casting by heated mold
（1. School of Materials Science and Engineering, Gansu University of
Technology, Lanzhou 730050, P.R.China;
2. School of Materials Science and Engineering, Huazhong University of
Sci and Tech, Wuhan 430074, P.R.China）
Abstract:The continuous directional solidification technique of five kinds of special ZA alloys with eutectic, peritectic and eutectoid transformation under the condition of continuous casting by heated mold was studies. The mechanism of surface defects appearing in ZA alloy line was discussed and the structure of some defects were analyzed by SEM. The results show that only when the fitting of various technique factors, pressure head, outlet temperature, pulling speed and cooling condition is reasonable under a certain range, can the ZA alloy smooth line be continuously pulled out. Unreasonable technique will result in hot tear, rough surface, mush outlet, leaking and other defects. The shape and location of solidliquid zone have the importance influence on the forming of above defects. When the solidliquid zone is located in the mould outlet or inner mould, the surface of solidification will protrude into the inner mould. If the left liquid can not counteract the solidification contract, the rough surface will appear. If the solidification surface further into the mould, the ingot in mould will have a big friction force when pulling and form hot tear. When the solid-liquid zone is moved out of mould, the solidification surface will turn into a plane, which made it easy to form leaking. The vibration or unstable operation will make the ingot winding during pulling.
Key words: continuous casting; directional solidification; heated mold; zinc-aluminum alloy; defects
