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铝合金铸件都存在一个通病，那(nei)便是(shi)有(you)因吸气而构成的(de)气孔缺(que)点，并且还有(you)可能(neng)是(shi)不(bu)同型式的(de)气孔
经剖析(xi)证明，铝合金(jin)铸件上气孔(kong)(kong)的主要成(cheng)分是氢气，并(bing)且是没(mei)有(you)必定的规则(ze)可循，常见的是针(zhen)孔(kong)(kong)。针(zhen)孔(kong)(kong)指(zhi)的便是小(xiao)于1mm的分出性气孔(kong)(kong)，多(duo)呈圆形，并(bing)不均匀散布在(zai)铸件整个(ge)断面(mian)上，特别是在(zai)铸件的厚(hou)大断面(mian)和冷(leng)却(que)速(su)度较小(xiao)的部位。
依据分出(chu)(chu)性气孔(kong)(kong)的散布(bu)和(he)形状(zhuang)特征，针(zhen)(zhen)(zhen)(zhen)孔(kong)(kong)又(you)能(neng)够分为网状(zhuang)针(zhen)(zhen)(zhen)(zhen)孔(kong)(kong)、点(dian)状(zhuang)针(zhen)(zhen)(zhen)(zhen)孔(kong)(kong)及综合(he)(he)性气孔(kong)(kong)三类。网状(zhuang)针(zhen)(zhen)(zhen)(zhen)孔(kong)(kong)望文生义便是针(zhen)(zhen)(zhen)(zhen)孔(kong)(kong)密布(bu)相连成网状(zhuang)，且有少量较(jiao)大的孔(kong)(kong)洞；点(dian)状(zhuang)针(zhen)(zhen)(zhen)(zhen)孔(kong)(kong)概(gai)括(kuo)明晰且互不接连，能(neng)数出(chu)(chu)每平方厘米面(mian)积上(shang)针(zhen)(zhen)(zhen)(zhen)孔(kong)(kong)的数目，并(bing)能(neng)测得出(chu)(chu)其直径(jing)。而综合(he)(he)性气孔(kong)(kong)是上(shang)述两(liang)种(zhong)的中(zhong)心型，其中(zhong)大针(zhen)(zhen)(zhen)(zhen)孔(kong)(kong)较(jiao)多并(bing)呈(cheng)多角形。