them from the treatment material in applications where they are not effective. If they have to be used, try to reduce the dosage as much as possible without affect- ing the quality of your metal castings. Foundries should find the optimal amount of rare earth additions through experimentation and analysis in the context of their own production conditions and products. Companies also can form coalitions to perform the research and share new technologies. Following are several measures that might be effective in limiting rare earth use.
1) Development of High Purity Pig Iron Te use of high purity pig iron can help metalcasters
facing increasing casting quality and stability requirements. High purity pig iron decreases the content of detrimental elements, which can mean lower quantities of rare earth metals are needed as a spheroidizing agent. In recent years, the foundry industry in developed
countries has begun to increase the use of high purity pig iron. According to the Japan Foundry Society, less than 20% of the total pig iron consumed in 1997 was high purity. In 2002, it increased to 31%. According to a report by the Kobe Steel Group, the percentage has increased to 60% in recent years. Several suppliers produce high purity pig iron for met-
alcasting facilities, per the specification dictated by the China Foundry Association. As production expands, the quality of the pig iron is expected to increase further, and more categories should be added to satisfy the require- ments of different customers. Te Japanese metalcasting industry realized many years
ago that using a greater percentage of high purity pig iron in induction furnaces means less high quality steel scrap is required to adjust the carbon content. Tis realization has been helpful for the improvement of casting quality and cost reduction.
2) Improvement of Spheroidizing Techniques In Chinese metalcasting facilities, spheroidizing
agents such as rare earth ferrosilicon magnesium alloys are added to the melt by a simple pouring method. With this method, the utility of the spheroidizing agent is only 30%. The act of pouring the agent into the melt also creates severe working conditions and an unstable spheroidizing effect. Other methods could save resources, lower costs and
reduce environmental pollution. The shift from the pouring method to a ladle covering method would be simple, with no need for a large investment in equip- ment. The application of the method can save 10-15% of the spheroidizing agent and improve working condi- tions and quality stability. Te wire feeding technique also has a series of advan-
tages, including: • elimination of the need for rare earth metals for usual ductile cast iron;
• significant savings of the spheroidizing agent;
而各企业要根据的具体生产条件、产品的特点和质量要求， 通过试验和分析研究，寻求最佳的工艺方案。已形成产业集 团的地区，可联合进行研究开发，各企业根据自己的特长分 担若干小课题进行试验，然后集中研讨，形成共有的专有技 术。以下，只就球墨铸铁的生产，提出几个可供行业同仁考 虑的方面：
1．推广应用高纯生铁
随着对铸件质量水平和质量稳定性的要求日益提高， 高纯生铁的推广应用已经成为不可逆转的趋势。采用高 纯生铁作为主要炉料，熔制的铁液中，各种干扰元素的 含量很低，球化剂中当然就可以少用或不用稀土元素。 近年来，一些工业国家铸造行业中，高纯生铁的应 用已日见增多。根据日本已发表的、不完全的统计数 字：1997年，全国消费的铸造生铁中，高纯生铁所占的 比重不到20％；2002年即已增长到31％。此外，据日 本神户制钢所的报道，该公司近期销售的铸造生铁中， 高纯生铁已增至60％左右。
为适应生产优质球墨铸铁件的需求，目前，我国已有 三家为铸铁厂提供高纯生铁的企业，产品的品质已不亚 于自加拿大或南非进口的Sorelmetal，而价格则便宜很 多。中国铸造协会也正在着手制定有关高纯生铁的行业 标准。今后随着生产规模的逐渐扩大、国产高纯生铁的 质量还可望进一步提高，而且还将逐步增加品种，以适 应不同客户多方面的要求。
日本早就有人认识到，采用感应电炉熔炼的铸铁企 业，高纯生铁在炉料中所占的比重将不断提高，今后， 有可能只用很少量的优质废钢调整碳含量，而以回炉料 和高纯生铁作为主炉料。这样，对于铸造企业提高产品 质量和降低生产成本都将大有裨益。
今后，面对减少稀土金属的用量的新形势，为了确保 产品质量下，高纯生铁的应用必将进一步增加。
2．改进球化处理工艺
目前，我国铸造厂生产球墨铸铁，球化剂主要是稀 土镁硅铁合金，大多数铸造厂球化处理都采用简单而粗 放的冲入法。虽然操作方便，但球化剂的收得率很低， 一般只有30%左右，而且处理过程中火光迸发、烟雾弥 漫，恶化作业环境，球化处理的效果也难以稳定。 笔者认为，我国作为一个铸造大国，无论从节约资 源、降低生产成本、环境保护和确保产品质量哪一方面 考虑，都应该尽快摒弃当前广泛应用的冲入法。 一般的铸造厂可采用盖包法。由冲入法改变为盖包法并 不复杂，生产设施方面无需很大的投入，技术方面也没有 什么难度。熟练掌握工艺后，球化剂可节省10%～15%， 作业场所的条件可明显改善，产品质量也将更为稳定。 采用喂丝球化的工艺，有很多优点，如： ◆ 一般球墨铸铁件的球化剂中都可以不用稀土；
Fall 2011
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