【作者】 尤晶；

【导师】 冯乃祥；

【作者基本信息】 东北大学 ， 有色金属冶金， 2008， 博士

【摘要】 在铝合金中,铝硅合金是品种最多,用途最广的一类,目前生产铝硅合金的方法主要是兑掺法,这种工艺方法能耗较高,流程较长,而且需要高品位的铝土矿。电热还原法是世界公认的优于兑掺法的铝硅合金生产方法,该方法流程短,可以利用低品位铝土矿或非铝土矿资源,符合我国铝矿资源特点。但是,电热法生产的一次铝硅合金中含有大量的金属杂质和熔渣。为了制取符合工业标准的铸造用铝硅合金,在生产过程中必须要将金属杂质和熔渣去除。本文对从高岭土直接用电热法制得的一次铝硅合金为原料,经加铝稀释、加精炼剂除渣、加锰除铁后制取铸造用铝硅合金进行了研究。矿热炉生产的一次铝硅合金中,除了铝和硅,含有的熔渣主要是Al2O3和SiO2,它们大部分以Al2O3·SiO2复合氧化物形式存在。金属杂质主要是钙,铁和钛,其中杂质铁主要是以FeAl3和Al4FeSi2的形式存在,钙是以CaAl2Si2形式存在,钛则以TiSi2的形式存在。实验过程中首先对一次铝硅合金进行加铝稀释,然后加精炼剂进行除渣。实验采用的熔剂精炼法,以冰晶石、氯化钠和氯化钾为除渣精炼剂,在960℃进行精炼。通过实验发现,随精炼剂量的加大,绝对渣量增加；合金中硅、铁含量都呈直线下降,当达到一定值后,绝对渣量和硅、铁含量的变化趋于平缓。在精炼除渣的过程中发现,一次合金中的主要金属杂质之一—钙在精炼过程中大部分以氟化钙的形式进入渣中。精炼剂的最佳加入量为铝硅合金量的3.5%,在该加入量时可以去除合金大部分的熔渣和金属钙杂质。精炼除渣后的铝硅合金中,铁是铝硅合金中主要的有害杂质元素,也是衡量铝硅合金质量最为重要的指标之一。精炼后铝硅合金中的铁以δ6铁相存在。以锰为除铁剂,在960℃除铁后降温过滤,合金中的铁和硅的含量随着锰加入量的增加而逐渐减少并趋于一定值,随过滤温度的升高而增加,随过滤骨料粒度的变细及骨料厚度的增加而降低。最佳的锰加入量为锰铁比1.2：1,最佳的过滤温度为580℃,过滤骨料的最佳粒度为3-5mm,厚度为4cm。铝硅合金中的铁主要以三种方式除去：一种是少量的铁以FeMnO3的形式进入熔渣中(熔渣主要指一次渣和二次渣)；另一种是沉降到坩埚底部生成半固态的多元金属合金。另有一部分铁进入过滤滤渣中。当铝硅合金中富铁相(在合金中以四元金属间化合物的形式存在)中的锰铁和量较多时,合金中的铁相会沉到合金底部形成新的合金,当合金富铁相中的锰铁和量较少时,该部分富铁相一般不能自然沉降而是通过过滤去除较大块的铁相,剩余的铁相进入铸造用铝硅合金中。加氯化锰除铁时,虽然可以达到加锰除铁同样的效果,但由于铝损失较多不宜采用。锰铬联合除铁,由于铬的沉降较快,不能和富铁相生成含铬较多的金属间化合物,除铁效果不好。加入直流电磁场后,铝硅合金中的铁相体积增大,在磁场电流较小时,富铁相主要是以长片状和小片状形式存在,但仍有针状的富铁相存在,而当电流达到950A时,合金中的富铁相已经全部变成了球状。加入稳恒磁场后合金中富铁相中元素的含量发生了变化,富铁相中的锰量增加。合金中富铁相中含锰量越到合金的底部含锰量越高。锰与电磁场联合除铁时,在同样的过滤条件下,过滤后合金中的铁含量比加锰除铁法有所下降,除铁效果较好。一次铝硅合金经过除杂提纯后制取的ZL101合金和ZL102合金,化学成分能够达到国家标准要求,以锶作为变质剂进行变质处理后,制取的铸造铝硅合金ZL101和ZL102的力学性能达到国家标准的要求。在由一次铝硅合金生产铸造用铝硅合金工业试验的过程中,通过选择合理的过滤温度,过滤骨料的粒度和厚度,以及除渣除铁机制,最终获得了含铁量低于0.7%的铸造用铝硅合金。更多还原

【Abstract】 Al-Si alloy has the most species and extensive use in aluminum alloy. At present, most Al-Si alloys are produced by melting pure aluminum and silicon. The energy consumption of the technics is high, the line of production is long and it need high grade ore. It recognized at the present in the world wide that Electrothermal reduction is superior to the method of melting pure Al and Si. The electrothermal reduction has short line of production and can use low grade bauxite and other resource. However, this method also suffers its defect that there are so many impurities in coarse Al-Si alloy. The main impurities are metal and non-metal slag. In order to gain casting Al-Si alloy conforming to industrial standard, refined and removed iron should be done first. This article studies the process of the coarse Al-Si alloy which is gotten by the kaolin with electrothermal reduction to produce the casting grade Al-Si alloy after diluting by Al, refining by flux and iron removal by manganese.The coarse Al-Si alloy produced by submerged arc furnace has the main slag are Al2O3 and SiO2 and the slag is mainly in the Al2O3·SiO2 compound oxidate form. The metal impurities are Ca, Fe and Ti. The impurity Fe is mainly in the FeAl3 and Al4FeSi2 form. The impurity Ca is mainly in the CaAl2Si2 form. And the impurity Ti is mainly in the form of TiSi2.The test use the Al as the dilution agent for the the coarse Al-Si alloy first. And then adopts a refining method by flux to remove slag, and treating the alloy with a molten mixture of sodiume chloride, potassium chloride and cryolite at 960℃. It can be concluded after the experiment that the net quantity of slag increases and the contents of Al and Si decline linearly with increasing of the purificant addition initially, but the change becomes unobvious after the purificant addition exceeded a specific value. The optimal addition of purificant is about 3.5% of the mass of aluminum-silicon alloy.Iron is the major impurity in aluminum-silicon alloy after the refining and slag removal, and the content of iron is one of the crucial scales for grading Al-Si alloy quality. After refining the iron in the alloy is 5 phase. Adding manganese into the molten alloy at 960℃ and then filtering after cooling, the content of Si and Fe decrease with the increasing of manganese until the contents reached a particular value. The content of Si and Fe also increase with the increasing of filtration temperature and decrease with the decreasing of aggregate size. Manganese’s optimal addition is which make the mol ratio of Mn and Fe valuing 1.2:1, the filtration temperature is 580℃,and the filtration aggregate size is 3-5mm and the thickness is 4cm.The iron removal is mainly in three ways. A small amount of iron is fusing into the slag in the form of Fe2O3 and FeMnO3 (the slag contains first slag and second slag). Some of iron settling in the bottom of melting pot becomes semisolid multivariant intermetallic compound. And some of iron is in the filtration slag. The iron settles in the bottom of alloy and generates the new alloy when the sum content of Mn and Fe in the iron-rich phase(quaternary intermetallic compound) is more. But when the sum content of Mn and Fe in the ron-rich phase is little, the bigger iron phase is removed not by the way of the free settling but the filtration. The remainder of Fe phase is in the casting grade Al-Si Alloys.It can have the same iron removal result when the manganese chloride is used as deferrization agent. But the loss of Al is too high, the agent is not appropriate.The free settling speed of Cr is too high and cannot generate the intermetallic compound that containing more Cr with iron-rich phase. So the method of iron removal by Mn and Cr is not suitable.In the direct current electromagnetic field, the Fe phase volume in the Al-Si alloy is growing. The iron-rich phase is mainly in the forms of long flakes and small flakes but still has the acicular phase of the iron-rich phase when the electromagnetic current is small. But when the electric current achieves 950A, rich-iron phase in the alloy already completely turned into spherical phase. The contents in the rich-iron phase of the Al-Si alloy had changed in the adding of steady magnetic field, the content of manganese had increased. The manganese in iron-rich phase of the alloy is getting higher as approaching the alloy’s bottom. The effect of iron removal is fairly good when the manganese and the electromagnetic field are both used. Under same filtration condition, the iron content of the alloy is lower than using the manganese.The chemical compositions of ZL101 and ZL102 produced by the coarse Al-Si alloy can meet the national standard. And after modification by strontium the mechanical property of the ZL101 and the ZL102 can meet the commercial production request. During the process of producing the casting grade Al-Si alloy with the coarse Al-Si alloy, the casting grade Al-Si alloy which the iron content is under0.7% is gotten by choosing the suitable conditions including the filtration temperature, the aggregate size, the aggregate thickness, and iron removal method.更多还原