为了减缓铝液的氧化和吸气，铝合金应在熔剂层覆盖下熔炼。可向坩锅内加入KCl、NaCl等作为熔剂，以便将铝液与炉气隔离。为驱除铝液中已吸入地氢气，防止针孔的产生，在铝液出炉之前应进行驱氢精炼。
采用钢包精炼方法把夹杂物消灭在钢水进入结晶器之前是获得“干净”钢水的关键。
The elimination of inclusions from molten steel before casting into mould using ladle refining operation and tundish metallurgy is the key practice to obtain clean steel.
现在，我们只需要知道，一个case类允许精炼的简单对象的构造，以及一些预定义的方法。
For now, it will suffice to say that a case class allows for very terse construction of simple objects with some pre-defined methods.
但不同之处在于它们持续计算，并且精炼它们的反复试验方法，模拟在野外自然选择的方式来工作。
But the difference is that they continually crop and refine their trial-and-error solutions-mimicking the way natural selection works in the wild.
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