There are many advantages to using silicate as a
binder for sand, especially that no harmful substances are discharged. However, there are also some acute problems with the use of silicate-bonded sand, such as the dif- ficulty of shakeout, poor casting surface quality, difficult reclamation and low recycling rate. Te low recycling rate of used sand leads to large amounts of waste sand being discharged. Because silicate is a strong alkali and it is water soluble, the discharged waste sand can damage the environment and pollute surface water and groundwater. From an environmental protection standpoint, the use of silicate is a double-edged sword. Intensive research has been carried out worldwide on the
improvement of silicate binders; nevertheless, a satisfactory solution has not yet been achieved. With extensive use of various resin binders, the application of silicate binders has shown a downward trend. In recent years, due to the requirements of clean produc-
tion and environmental protection, the global metalcasting industry again focuses on various inorganic binders, and among them, silicate is considered first. It should be said that research on water-soluble silicate binders has entered a new stage, but of course, research in this respect has just started and has a long way to go. In the last 10 years, the German metalcasting industry has
carried out comprehensive and intensive research on silicate binders, in cooperation with various companies and institutes, which include: • Global binder manufacturers such as ASK and HZ, which engaged in the research and development of silicate sys- tem binders and their modification.
• Laempe & Mossner, which studied coremaking equip- ment suitable for volume production using silicate binder systems.
• The institute of foundry technology of TU (Technische Universität Bergakademie Freiberg) developed sand recla- mation and recycling.
• BMW, VW and Daimler’s nonferrous metalcasting facil- ity located in Mettingen, Germany, which carried out processing experiments and application. Based on intensive research and development, a new sili-
cate binder commenced production trials in 2006 to test the process feasibility and was soon put into volume production. It is now confirmed that for this new silicate binder, good results have been achieved in ecology, quality and economy. Tis research achievement marked a new era of applica- tion for silicate, especially in volume production in the auto industry. China’s FAW automotive group has introduced this technology for aluminium casting production. From production experiences, two principles need to be
followed to resolve the reclamation and recycling problem of silicate bonded sand: • The sand molds and cores must not be subjected to high temperature for too long a period. The water glass film around the sand grains cannot be allowed to lose bound water or combined water. More importantly, silicates cannot be allowed to fuse with the sand. At present, this
硅酸盐的制取工艺比较简单，原材料无匮乏之虞， 价格也相当低廉。
采用硅酸盐作型砂粘结剂，可以有多种造型工艺，
如：吹CO2硬化工艺、真空置换硬化工艺（简称VRH 工艺）和有机酯自硬工艺等。
硅酸盐粘结剂有很多优点，特别值得关注的是铸造 生产过程中不排放有害物质。但是，其在铸造生产中 的应用还存在一些棘手的问题，如落砂困难、铸件表 面质量较差、旧砂难以再生回用率低等。 旧砂回用率低当然导致废弃砂的排放量大。由于硅 酸盐的碱性很强，而且是水溶性的，排放的废弃砂会 影响周边的环境，并污染附近的水和地下水。因此， 就环保方面而言，这种粘结剂是一把双刃剑。 虽然，世界各国在硅酸盐粘结剂的改进方面都进行 了大量的研究工作，但长时间以来，都没有令人满意 的解决方案。在各种树脂粘结剂广泛应用的条件下， 硅酸盐粘结剂的应用早已呈现每况愈下的态势 近年来，出于清洁生产和环境保护的考虑，各国 工业国家的铸造行业再次将注意力转向各种无机粘 结剂，其中当然首先是硅酸盐类。应该说，对水硅酸 盐粘结剂的研究和应用又进入了一个崭新的阶段，当 然，这方面的研究工作还只是刚刚起步，来日方长。 近十多年来，德国的同行对硅酸盐类粘结剂进行了 全面而系统的研究、开发工作，力度非常之大，由许 多知名的单位分工合作，其中有： • ASK公司和HA公司等世界知名的粘结剂生产厂 商，从事硅酸盐系粘结剂及有关改性剂方面的研 究、开发工作；
• Laempe & Mossner公司，研制适用于用硅酸盐 系粘结剂、大批量自动化制芯的设备；
• TU矿业研究院铸造研究所负责旧砂再生、回用方 面的研究；
• BMW（宝马）公司、大众汽车公司和Diamler公 司位于Mettingen的轻合金铸造厂等生产企业从 事工艺试验和生产应用。
在大量研发工作的基础上， 2006年开始试生产， 以考核工艺的可行性，很快就正式在汽车工业大批量 生产中应用。现已确认：在生态、产品质量、经济等 方面都获得了很好的效益。这项成果，标志着硅酸盐 粘结剂的应用已经进入了一个崭新的纪元，其在汽车 行业大批量中的应用尤其值得重视。我国一汽公司最 近已经引进了这项技术，用于铝合金铸件的生产。 虽然未见报道与他们产品相关的具体技术内容，但 是，从许多生产厂家的情况介绍中，我们大致可以得
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FOUNDRY-PLANET.COM | MODERN CASTING | CHINA FOUNDRY ASSOCIATION February 2013
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