铸造缺陷简介

以下是主要缺陷，可能发生在沙铸件中

Gas defects
收缩腔
Molding material defects
Pouring metal defects
Mold shift

气体缺陷

A condition existing in a 由气体捕获在熔融金属或模具中引起的铸造 gases evolved during the pouring of the casting. The defects in this category can be classified into blowholes and pinhole porosity. Blowholes are spherical or elongated cavities present in the casting on the surface or inside the casting. Pinhole porosity occurs due to the 氢气的溶解，在加热期间被捕获 molten metal.

Causes

较低的气体趋势模具，这可能是由于通风较低，渗透率较低 the mold or improper design of the casting. The lower permeability is 由沙子的晶粒尺寸较小，霉菌中的粘土比例高 mixture, and excessive moisture present in the mold.

Metal contains gas
霉菌太热了
Poor mold burnout

Shrinkage Cavities

这些是由液体引起的 shrinkage occurring during the solidification of the casting. To 补偿这一点，需要适当的液态金属喂食。为了这个原因放置在模具中的适当位置。泉水可能太薄，太长或不在适当的位置附着， causing shrinkage cavities. It is recommended to use thick sprues to 避免收缩腔。

成型材料缺陷

此类别中的缺陷是切割和洗涤，金属穿透，融合和膨胀。

Cut and washes

这些看起来像粗糙的斑点 areas of excess metal, and are caused by erosion of molding sand by the 流动的金属。这是由成型沙子没有足够的造成的 strength and the molten metal flowing at high velocity. The former can be taken care of by the proper choice of molding sand and the latter can be overcome by the proper design of the gating system.

金属穿透

When molten metal enters into 沙粒之间的间隙，结果是粗糙的铸造表面。发生这种情况是因为沙子是粗或没有霉菌洗的 the surface of the mold. The coarser the sand grains more the metal 渗透。

Fusion

This is caused by the fusion of the sand grains with the molten metal, giving a brittle, glassy appearance on the casting surface. The main reason for this is that the clay or the sand particles are of lower refractoriness or that the pouring temperature is too high.

胀

Under the influence of 金属固定力，霉菌墙可能会向后移动，导致膨胀铸件的维度。适当的模具将纠正 this defect.

夹杂物

Particles of slag, refractory 材料，沙子或脱氧产品被困在铸件中在倒入凝固过程中。在门控中提供cho 系统和模具顶部的倒水池可以防止 defect.

倒金属缺陷

The likely defects in this category are

Mis-runs and
Cold shuts.

当 metal is unable to fill the mold cavity completely and thus leaves 未填充的腔。当金属太冷而流动时，会产生错误的结果在冷冻之前到达霉菌的四肢。长而薄的部分受到此缺陷的约束，应避免铸造设计。

A cold shut is caused when two streams while meeting in the mold cavity, do not fuse together properly thus forming a discontinuity in the casting. When the molten metal is poured into the mold cavity through more-than-one gate, multiple liquid fronts will have to flow together and become one solid. If the flowing metal fronts are too cool, they may not flow together, but will leave a seam in the part.

Such a seam is called a cold shut, and can be prevented by assuring sufficient superheat in the poured metal and thick enough walls in the 铸造设计。

The mis-run and cold shut
defects are caused either by a lower fluidity of the mold or when the 铸件的截面厚度很小。流动性可以提高通过更改金属的成分并增加浇注金属的温度。

霉菌移动

The mold shift defect occurs when cope and drag or molding boxes have not been properly aligned.

铸造缺陷：

The 铸件中的缺陷可能是由于图案和成型箱设备，成型沙子，芯子，门控系统或熔融金属。一些缺陷 are:

1: Mould shift

它results in a mismatching of the top and the bottom parts of the casting , usually at the parting line.

2: Swell

这是通过熔融金属压力扩大霉菌腔，导致铸造的局部或一般增大。

3: Fins and Flash

These 是金属的薄凸起，不打算作为铸造的一部分。 These usually occurs at the parting line of the mould.

4: Sand Wash

它通常发生在大门附近，因为铸造表面上的粗糙团块。

5: Shrinkage

它 is a crack or breakage in the casting on the surface of the work piece, which results from un equal contraction of the metal during 凝固。

6: Hot Tear

它is an internal or external ragged discontinuously in the metal casting resulting just after the metal has solidified.

7：沙吹或吹孔

它is smooth depression on the outer surface of the casting work piece.

8: Honeycombing or Slag holes

这些是铸件上表面上的光滑抑郁症。它们通常发生在凹痕附近。

9: Scabs

These are patches of sand on the upper surface of the casting component.

10：冷关

These happens when the mould cavity is not completely filled by the molten and insufficient material or metal.

11：淘汰和破败

这些允许金属从腔中排出，并导致不完整的铸造。

More Resources /articles

什么是铸造缺陷？

铸造缺陷简介