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熔模铸造中,蜡模挂砂后要放在氯化铵的水溶液中浸泡,使之起化学反应后硬化。模壳硬化得好坏,与它在氯化铵水溶液中浸泡时间——硬化时间和氯化铵水溶液的浓度有关。我们采用在水里投入过量的氯化铵的方法,使溶液成为氯化铵的饱和溶液。这样浓度固定了,硬化时间与模壳硬化得好坏就成了单因素的关系,故采用“折纸法”对硬化时间进行优选。根据实践经验,硬化时间在5～60分钟之间,少于5分钟或多于60分钟都不好。所以优选的范围在5～60分钟内,用一张有刻度的纸条表示,如图1所示。
In investment casting, the wax mold sand should be placed in an aqueous solution of ammonium chloride soaked, so that after the chemical reaction hardening. Mold shell hardening is good or bad, and its soaking time in ammonium chloride aqueous solution - hardening time and the concentration of ammonium chloride aqueous solution. We use the method of throwing in excess ammonium chloride in water to make the solution a saturated solution of ammonium chloride. This concentration was fixed, curing time and the mold shell hardened become single factor relationship, so the use of “origami method” on the curing time is preferred. According to practical experience, hardening time of 5 to 60 minutes, less than 5 minutes or more than 60 minutes are not good. Therefore, the preferred range is 5 to 60 minutes, with a graduated note, as shown in Figure 1.