and, on average, less than 0.2 metric ton of new sand was consumed for every metric ton of steel castings; in addition, discharged waste substances were signifi- cantly reduced. In Tian Qian Heavy Industries Co., Limited, which
produces large steel castings, after changing to Bangni resin sand, no new sand was added for the first 6 months operation and a recycling rate of 94% was achieved. Using Bangni resin sand, the cost of reclamation of
recycled sand is around 30%, compared to water glass (silicate) sand or alkaline phenolic resin sand. When considering the investment cost of hot reclamation equipment, sand cooling after heating and equipment depreciation, the energy and cost savings in used sand reclamation are remarkable.
Comprehensive Production Cost of Steel Castings Cost compared to silicate binder—Although the
price of Bangni resin is much higher than that of silicate binder, production experience has shown that when using Bangni resin, the overall cost per metric ton of steel castings is about 6% lower than when using a silicate binder. The main reasons are the increased recycling rate of used sand, lower cost of reclamation, high efficiency in shakeout and fettling, lower cost of fettling and shorter production cycle. Cost compared to alkaline phenolic resin—Accord- ing to the 2012 statistics of the QINYE Steel Foundry, when using Bangni resin, the comprehensive cost per metric ton of steel castings is about 15% lower than when using alkaline phenolic resin. Among these cost savings, the investment cost of hot reclamation equip- ment, equipment depreciation and operational costs when reclaiming alkaline phenol resin sand are not yet included.
Service Performance of Bangni Resin Second hardening characteristics—Bangni resin is
a type of modified resole phenolic resin, with which the prepared molding sand has second-hardening character- istics. During production, after coating with an alcohol- based coating, the coating is fired and the strength and surface stability of molds and cores are improved signifi- cantly. Compared to water glass and alkaline phenolic resin
sand, Bangni resin sand has remarkable features: after stripping from the pattern, the molds have a relatively high initial strength, which is beneficial for both strip- ping and subsequent handling; and the residual strength after pouring is not too high, which is good for shakeout and reclamation. The final mold strength is around 0.5MPa, but
because of the second hardening process, no castings are scrapped due to weak sand strength. For Wuxi Foundry production, the sand strength after 24 hours is controlled at 0.5 - 0.7MPa. When Tian Qian Heavy Industries Holdings Co. Ltd produced a 160-metric-ton steel casting, the strength
了废弃物的排放。
生产大型铸钢件的天乾重工公司，采用邦尼树脂粘结 砂后，前六个月未加任何新砂，旧砂回用率为94%。 采用邦尼树脂，除旧砂回用率高以外，每吨回用砂的 砂再生成本大约只是水玻璃砂或碱酚醛树脂砂的30％左 右。如果再考虑热法再生一次性的设备投入的费用、设 备折旧费用及加热后再冷却的费用，邦尼树脂砂在旧砂 再生方面节能和降低成本的效果是十分显著的。
3、铸钢件的综合生产成本
（1）与采用硅酸盐粘结剂的成本对比 虽然邦尼树脂的价格比硅酸盐粘结剂高得多，但无 锡铸造厂实际使用的经验表明，采用邦尼树脂砂，每 吨铸钢件的综合生产成本却比用硅酸盐粘结剂时低6 ％左右。其主要原因是旧砂回用率提高、砂再生费用 低、铸件落砂与清理效率高、清理费用低、生产周期 缩短等。
（2）与采用碱性酚醛树脂的成本对比
按秦伊铸钢厂2011年的统计，采用邦尼树脂，每吨 铸钢件的综合生产成本比与采用碱性酚醛树脂降低15％ 左右。
其中，还未计及碱酚醛树脂砂热法再生设备的投 资、运行费用和相关的折旧费用。
4、邦尼树脂的使用性能 （1）具有二次硬化的特性
邦尼树脂是一种改性的甲阶酚醛树脂，用以配制的 型砂具有二次硬化特性。生产过程中，铸型涂醇基涂 料并点燃后，砂型、芯子的强度与表面稳定性都有较 大的改善。
邦尼树脂砂与水玻璃砂、碱性酚醛树脂砂相比， 在生产中有一个突出的特点，即：砂型起模后初始强 度较高，有利于起模、搬运；浇注后的残留强度并不 高，有利于落砂与砂再生。
由于邦尼树脂有二次硬化过程，即使试样的终强度 在0.5MPa左右，在生产中也从未发生因型砂强度不 够而产生的废品。无锡铸造厂生产中，型砂试样放置 24h后的强度基本上控制在0.5—0.7MPa的范围内。 天乾公司生产160吨的铸钢件时，邦尼树脂砂的强 度完全满足了工艺要求，尤其在吊起70吨的大型砂芯
May 2013
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