said. “So we started learning how far we could push Deni- son’s mixers and went as low as the mixer would let us go.” During testing, Denison discovered each mixer had different capabilities, but all of them have been able to manage 0.4% binder levels. “It’s important to know that your sand level is consistent and the mixer keeps the sand-to-binder ratio that was set,” Walker said. Denison uses 98% thermally reclaimed sand with 2%
Oklahoma 75 GFN sand. Te high quality Oklahoma sand is an advantage for running at low binder levels, according to Purcell, because it is a pure, round grain silica sand. Termal reclamation burns the binders off the sand grains, so Denison can remove the dust fines through a collection system, producing a better quality of sand grain to which the binder adheres. “What is happening at Denison is a trifecta—they’ve got
a good resin system, as well as a good sand system,” Tinker said. “Plus, the sand they are bringing to it is good.” Denison keeps its sand stored outside in a silo. “We’re not heating or cooling sand down except with a
cooler classifier on the thermal reclamation unit,” Walker said. “Te moisture from humidity is still there. We haven’t done anything to control the environment on the shop floor. We just adapted our process to run effectively with lower binders. We fully understand what percentages to run for various tempera- tures and set up times based on the data [from the testing].”
Chemical Compatibility
Denison’s investigation led to total knowledge of its nobake operations, from how a unique batch of new sand will affect the molding line to which chemicals are present and active in its release agent. Armed with this data, Walker says he knows how to adjust the system for cores that may be setting up and sitting for two weeks or are being produced on a humid day. He can calculate the cost going into each mold or core in the shop, and opportunities for improvement become more apparent with better understanding of all the variables. Case in point: Denison had been experiencing difficulty
removing molds from one of its larger nobake lines. After making sure the box was level and the shaker to remove the mold was operating properly, the metalcaster studied the release agent and its compatibility with the binder. It discov- ered the solvents in the release agent were some of the same chemicals used in the binder, and the combination was acting like a thinner, reducing the effect of the release agent. Te casting facility stopped using binder with similar chemicals, and the erosion of chemicals was eliminated. Once the binder was no longer negatively reacting with the release agent, Denison found it could use less of the agent on its molds. It now uses 12.5 gallons of release agent a year, compared to 250 to 275 gallons prior to the testing. “We never thought in our wildest dreams we could do
that,” Walker said. “It came along with looking at the process. And now the molds nearly fall out of the boxes.” ■ To receive this digital magazine in the future, go to
www.globalcastingmagazine.com.
说： “因此，我们开始研究我们到底可以把丹尼森工业 公司的混砂机用到什么水平，并尽可能地降低粘结剂的 用量。”在测试过程中，丹尼森工业公司发现每个混砂 机的能力不同，但都能达到0.4％的粘结剂水平。 Walker说：“重要的是要知道，砂子的水平是稳定一 致的，因此混砂机会保持设定的砂子-粘结剂比例。” 丹尼森工业公司使用98％的再生砂与2％的Okla- homa 75 GFN原砂混合。Purcell表示，高品质的 Oklahoma原砂是使用较低粘结剂水平的保证，因为它 是纯圆颗粒硅砂。热法再生烧掉了砂粒的粘结剂，因此 丹尼森工业公司可以通过收集系统清除掉粉尘，质量更 好的原砂可使粘结剂更好地粘接。 Tinker说：” 丹尼森工业公司是一举三得，他们得 到了良好的树脂体系，良好的砂系统，另外，他们得到 了好的型砂。”
丹尼森工业公司在户外仓中储存型砂。 “除了热回收单元的冷却分选器外，我们不加热或冷 却砂子，” Walker说，“环境湿度带来的水分仍然存 在。我们没有控制车间环境，我们只是调整了工艺来实 现较低的粘结剂水平。通过测试得到的数据，我们完全 掌握了不同温度下需要粘结剂的百分比和固化时间。”
化学相容性
丹尼森工业公司的研究工作得到了自硬砂操作的所有 知识，从某一特定批次的新砂如何影响造型线到脱模剂 中加什么化学物质和什么化学物质有活性。Walker说， 有了此数据后，他知道如何调整系统以适应各种砂芯， 如制芯后放置两周或者在潮湿天气制芯，他可以计算出 车间中每个砂型或砂芯的成本。更好地了解所有的参数 后，改进就变得更加容易。
案例分析：丹尼森工业公司曾在一个较大的自硬砂造 型线脱模时遇到过困难。在确保砂箱填砂以及振动脱模 正常运行后，铸造工作者开始研究脱模剂及其与粘结剂 的兼容性。最后发现脱模剂的溶剂与粘结剂有相同的化 学成分，它们结合后就像稀释剂，这就降低了脱模剂的 效果。铸造厂停止使用具有该类化学成分的粘结剂，降 低了该化学成分带来的侵蚀。一旦粘结剂不再与脱模剂 发生负反应，丹尼森工业公司发现它可以降低砂型中粘 结剂的用量。现在每年使用12.5加仑脱模剂，而测试前 每年250到275加仑。
“即使在我们最疯狂的梦想中，我们也从来没有想过 我们能做到这一点，” Walker说：“需要对过程保持
关注。现在砂型几乎都能完全落砂。” ■ 如果您需要订阅本刊，请登陆
www.globalcastingmagazine.com。
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FOUNDRY-PLANET.COM | MODERN CASTING | CHINA FOUNDRY ASSOCIATION Spring 2012
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