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    • 铁型覆砂铸造工艺设计及实际生产主要解决:
    • 本站编辑:浙江省机电设计研究院有限公司发布日期:2017-09-11 13:49 浏览次数:
    ①铁型壁厚和覆砂层厚度及二者的配合,以满足不同壁厚和不同材质铸件对凝固和冷却的不同要求;
     
    The thickness of iron wall and the thickness of sand coating layer and the matching of the two parts to meet the different requirements of solidification and cooling of castings with different wall thickness and different materials;
     
    ②便捷和经济的覆砂成型方法,以满足不同铸件对表面质量和尺寸精度的要求;
     
    Convenient and economical sand forming method to meet the requirements of surface quality and dimensional accuracy of different castings;
     
    ③工艺参数。如浇注系统、射砂系统、排气系统等的确定;
     
    Process parameter. Such as pouring system, sand shooting system, exhaust system and so on;
     
    ④批量生产的实现。例如生产线及覆砂主机和辅机的设计定型;
     
    The realization of mass production. For example, the design of the production line and the coating machine and the auxiliary machine is finalized;
     
    ⑤工艺规程的制定,例如浇注、冷却和开箱等规程,以及铸件成分的调整等。
     
    Process planning, such as pouring, cooling and unpacking, as well as the adjustment of casting components.
     
    2铁型覆砂铸造的热交换特点
     
    Characteristics of heat exchange of 2 iron sand covered casting
     
    液态金属浇入铁型覆砂铸型以后,“铸件——覆砂层——铁型”是一个不稳定的热交换系统。为了使问题简化,假设铸件是半元限的;并假设系统中各组元的温度场按直线规律分布的。图1表示系统的一部分,显然,同样的比热流q通过了系统中各个组元:
     
    After the liquid metal is poured into the iron mold, the casting - sand layer - iron type is an unstable heat exchange system. In order to simplify the problem, it is assumed that the casting is half yuan, and it is assumed that the temperature field of each element in the system is distributed in a straight line. Figure 1 represents a part of the system, and it is clear that the same heat flow Q passes through each component of the system:
     
     
     
    令分别表示铸件与覆砂 层、铁型与覆砂层之间热交换强度的两个传热准则。k1是铸件热阻与覆砂层热阻之比;k2是铁型的热阻与覆砂层热阻之比。将k1和k2结合起来考虑,随着覆砂层厚度的变化,有以下三种实际上可能发生的“铸件——覆砂层——铁型”间不同的传热情况:
     
    Two heat transfer criteria for heat exchange between casting and sand layer, iron and sand layer, respectively. K1 is the ratio of thermal resistance of casting to sand layer; K2 is the ratio of thermal resistance of iron to thermal resistance of sand coating. Taking K1 and K2 into consideration, with the change of the thickness of the overlying sand layer, there are three kinds of heat transfer conditions, namely, casting - sand layer - iron type, which may actually happen:
     
    ①当k≤1,k2≤1时,覆砂层在正常的厚度之内,铸件的冷却速度随着覆砂层厚度的减少而增大。
     
    When k = 1, K2 = 1, the sand layer within the normal thickness of the casting cooling speed increases with the decrease of the thickness of sand layer.
     
    ②当覆砂层的厚度超过某一厚度以后,铁型对铸件冷却已不产生影响,这时就相当于普通的砂型铸造或树脂砂铸造。由于覆砂层的导热系数比铁型的导热系数小得多,所以铸件冷却缓慢。
     
    When the thickness of the sand layer exceeds a certain thickness, the iron mould has no effect on the cooling of the casting, and this is equivalent to the ordinary sand casting or resin sand casting. Because the thermal conductivity of the overlying layer is much smaller than that of the iron type, the cooling of the casting is slow.
     
    ③当k≧1,k2≧1时,覆砂层厚度太薄,这时就相当于金属型铸造了。
     
    When k = 1, K2 = 1, the thickness of sand layer is too thin, then the equivalent of the metal casting.
     
    以上热交换特点已为实验所证实,当曲轴(CTЦ-14)铁型覆砂铸造的覆砂层厚度从4~32mm逐渐变化时,曲轴组织中的渗碳体量不断减少,珠光体量和铁素体量不断增加。而当覆砂层厚度小于4mm时,铸件的冷却强度与金属型(厚涂料)相近;覆砂层大于32mm时,则其冷却强度相当于普通树脂砂铸造了。
     
    The above heat exchange characteristics have been confirmed by experiments, when the crankshaft (CT Max -14) iron coated sand foundry sand thickness from 4 to 32mm gradually changes, cementite in crankshaft continues to decrease, the amount of pearlite and ferrite volume increasing. When the thickness of the sand layer is less than 4mm, the cooling strength of the casting is similar to that of the metal mold (thick coating). When the sand layer is larger than 32mm, its cooling strength is equivalent to that of ordinary resin sand.

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