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金沙官方赌场js5 阅读:- 公布日期:2018-05-10 12:00:00【

铁型覆砂锻造的热交换特性

 

Characteristics of heat exchange of 2 iron sand covered casting

 

液态金属浇入铁型覆砂铸型今后,“铸件——覆砂层——铁型”是一个不稳定的热交换体系。为了使题目简化,假定铸件是半元限的;并假定体系中各组元的温度场按直线规律散布的。图1示意体系的一部分,明显,一样的比热流q经由过程了体系中各个组元:

 

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:

 

令离别示意铸件取覆砂 层、铁型取覆砂层之间热交换强度的两个传热原则。k1是铸件热阻取覆砂层热阻之比;k2是铁型的热阻取覆砂层热阻之比。将k1和k2联合起来思索,跟着覆砂层厚度的转变,有以下三种实际上可能发生的“铸件——覆砂层——铁型”间差别的传热状况:

 

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,覆砂层正在一般的厚度以内,铸件的冷却速度跟着覆砂层厚度的削减而增大。

 

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当覆砂层的厚度凌驾某一厚度今后,铁型对铸件冷却已不发生影响,这时候便相当于一般的砂型锻造或树脂砂锻造。因为覆砂层的导热系数比铁型的导热系数小很多,以是铸件冷却迟缓。

 

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,这时候便相当于金属型锻造了。

 

When k = 1, K2 = 1, the thickness of sand layer is too thin, then the equivalent of the metal casting.

 

以上热交换特性已为实行所证明,当曲轴(CTЦ-14)铁型覆砂锻造的覆砂层厚度从4~32mm逐步转变时,曲轴构造中的渗碳体量络续削减,珠光体量和铁素体量络续增添。而当覆砂层厚度小于4mm时,铸件的冷却强度取金属型(薄涂料)邻近;覆砂层大于32mm时,则其冷却强度相当于一般树脂砂锻造了。

 

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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