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铸造生铁含有许多微量元素,它们在标准中一般均未给予规定,其中某些微量元素妨碍镁球墨铸铁中球墨的形成。以铈铁或火石合金(mischmetal)形式加入少量某些稀土元素能有效地抵消这些杂质的有害影响。这些稀土元素的合金除铈外,尚含有相当数量的La(镧)、Nd(钕)、Pr(镨)。目前关于这些元素单独对金属组织和性能的影响的资料很少,且实际上未曾将稀土元素的影响程度同铸造生铁杂质的含量和特性联系起来。本文试图提供有用的数据来弥补这个漏失的环节。碳当量近似的四种铸造生铁在高频感应电炉内重熔,并加入0.03—0.3％的稀土元素(La、Ce、Pr、Nd和它同镁的合金)进行处理。研究铸态和热处理后的试样表明,这四种原始铸造生铁承受处理的程度各不相同。所有稀土元素对球墨的大小和形状,铸铁的白口倾向,抗拉强度和RG/RH比值的影响也极不相同。一般而言,发现稀土元素降低铸铁中的总碳量和硅量。加入0.05％稀土元素起到类似普通孕育剂的作用,使共晶团细化。对于铸铁的白口倾向按以下顺序递增:La、Nd、Pr、Ce。镧极大地改善铸铁的抗拉强度,而铈的效果最差。各种铸造生铁承受这种处理程度各不相同,并取决于其中含有的杂质的特性和数量。
Foundry pig iron contains many trace elements, which are generally not specified in the standard. Some of these trace elements interfere with the formation of nodular graphite in magnesium nodular cast iron. Addition of small amounts of certain rare earth elements as cerium or mischmetal effectively counteracts the detrimental effects of these impurities. In addition to these rare earth elements of cerium, it contains a considerable amount of La (lanthanum), Nd (neodymium), Pr (praseodymium). There is currently little information on the impact of these elements alone on the microstructure and properties of metals and the fact that the extent of the effects of rare earth elements has not been linked to the levels and properties of cast iron impurities. This article attempts to provide useful data to make up for this missing part. Four types of pig iron with similar carbon equivalent are remelted in a high frequency induction furnace and treated with 0.03-0.3% rare earth elements (La, Ce, Pr, Nd and its alloys with magnesium). The study of as-cast and heat-treated specimens showed that the four raw cast irons were handled differently. The effect of all rare earth elements on the size and shape of the inks, the tendency of the white cast iron, the tensile strength and the RG / RH ratio is also very different. In general, rare earth elements have been found to reduce the total amount of carbon and silicon in cast iron. Adding 0.05% rare earth elements play a role similar to ordinary inoculant, the eutectic group refinement. White cast for cast iron tends to increase in the following order: La, Nd, Pr, Ce. Lanthanum greatly improves the tensile strength of cast iron, while cerium has the worst effect. The extent to which castings of various castings withstand this treatment varies, depending on the nature and amount of impurities contained therein.