Mixer equipment performance affects the required binder level in a nobake operation.
混砂设备的性能对粘结剂可以 降低到什么水平也有影响。
Bringing Down the Binder In each test conducted,
the casting company learned where failure occurred to establish a nominal operating range. Tests for failure were conducted offline so shop per- sonnel could remain unbiased toward the various binder mixtures being tested. As Denison passed through
round after round of tests, ratcheting down the amount of binder chemical used, it discovered the plant could operate at a high level with much less binder than it had been. Eventually, the plant was producing 600-lb. cores in the summer with 0.4-0.45% binder—down from 0.65%— resulting in castings with C60 surface finish or better. “I didn’t know what to
expect,” Walker said. “We were standing on the edge of a cliff. But we took the data and remained unbiased about what the process could do.” Walker said Denison has successfully produced cores with binder percentages as low as 0.38% but holds at 0.4% to maintain a comfortable level. “If someone would have told me they would be able to make a core at 0.38% binder, I would have said they were crazy,” Purcell said. According to Purcell, most aluminum nobake casting facilities use binder levels from 0.7 to 1%. Te lower binder level means both decreased VOCs in the
casting facility and an increase in the two-part binder’s flash points (the point at which chemical vapors will ignite) to 198.9C for part 2 and 93.4C for part 1.
Other Factors
According to Purcell, mixing equipment also plays a role in binder performance. Wil Tinker, president of Tinker Omega, Springfield, Ohio, U.S.A., said a mixer’s perfor- mance is based on the diameter vs. the length of the chamber (where the sand is mixed) and the overall tip speed of the mixing blades. Te accuracy of the pumping system, design and type of pump and spin control yield accuracy of delivery. Accuracy in the pumping system allows for a lower overall binder percentage, Tinker said. “Once you get to a certain binder percentage, [going lower] depends on how good of a mixer you have,” Purcell
降低粘结剂使用量
每做一次测试，铸造公 司就了解到哪里会有问题发 生，然后确定一个合理的工 作范围。破坏性的实验在线 下进行，这使车间人员能无 偏见地对待正在测试的各种 粘合剂混合物。
丹尼森工业公司通过一轮 一轮的实验，降低了粘结剂 的使用量，发现工厂可以用 相比过去较少的粘结剂来保 持一个较高的质量水平。最 终，该厂在夏天生产的600 磅砂芯中使用了0.4-0.45％ 粘结剂，铸件表面光洁度更 好，而过去需要用0.65％的 粘结剂。
“我不知道会发生什
么，”Walker说：“我们站在悬崖边，但是我们拿到了 数据，对这个过程能做什么没有偏见。” Walker 说丹尼森工业公司已经成功生产了含0.38%粘结 剂的砂芯，但是使用0.4%的粘结剂以保持质量的稳定性。 “如果有人告诉我他们能够做0.38％粘结剂的砂型， 我会说他们疯了，”Purcell说。据Purcell的说法，大部 分铝自硬砂铸造厂使用粘结剂的含量水平为0.7%~1％。 粘结剂含量水平较低意味着铸造厂的挥发性有机 化合物的排放减少，以及两组分粘结剂的燃点增加， 第2组分的燃点为389.98F（198.9℃）和第1组分为 200.1F（93.4℃）。
其它因素
据Purcell的说法，混砂设备对粘结剂性能也有一定 的影响。Tinker Omega 总裁Wil Tinker说，混砂机性 能基于搅拌室长度与直径和搅拌叶片的叶尖速度。泵输 送系统的精度、泵和转子的设计和类型决定了粘结剂比 例。精确的泵输送系统有助于采用较低的粘结剂比例。 “一旦确定了粘结剂的某一百分比，进一步降低粘 结剂的百分比取决于混砂机是不是足够好，” Purcell
Spring 2012
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