汽缸套内表面出现的微细孔穴统称为针孔。其大小多为0.1～0.3mm,肉眼可见。此种缺陷较常见,因而在现场生产和质检工作中时常要鉴别和分析所出现的针孔的本质和成因,多年来一直是个有争议的问题。其原因在于对缸套内表面出现的针孔至今未有进行科学的准确的分类,以至于在标准上也出现了某些不准确的规定。例如,61年农机部标准（草案）规定汽缸套不应有局部疏松、针孔、夹渣。其实疏松和夹渣都会带来针孔,那么这里所说的“针孔”是指什么就不明确。现场生产时常由于这种不明确规定而发生争论。又如GB1150—74的国家标准则规定汽缸套内表面允许有“石墨脱落而形成的针孔”。机加工必然使部分石墨脱落而留下长条状孔穴。但此种针孔宽度一般小于0.005毫米,是肉眼所不见的。而且就力学性能而论,铸铁中存在石墨等于存在孔洞,脱落与否影响不大。所以上述规定显然是多余的。相反,由于标准中确认存在着石墨脱落针孔也带来了混乱,常有人把形态与石墨完 Cylinder liner appears on the inner surface of the micro holes collectively referred to as pinholes. Its size is mostly 0.1 ~ 0.3mm, visible to the naked eye. Such defects are more common, so in the field of production and quality inspection work often identify and analyze the nature of the pinhole and causes, over the years has been a controversial issue. The reason for this is that pinholes on the inner surface of the cylinder liner have not been scientifically and accurately classified so far that there are some inaccuracies in the standards. For example, 61 years of the Ministry of Machinery Standards (draft) provides that the cylinder liner should not have local loose, pinhole, slag inclusion. In fact, porosity and slag will bring pinholes, then what is referred to here as “pinholes” refers to what is not clear. Onsite production often argues for such ambiguous rules. Another example is the national standard GB1150-74 provides cylinder liner surface allow “pinhole formed by the graphite off.” Machining is bound to make some graphite off and leave long holes. However, this pinhole width is generally less than 0.005 mm, is the naked eye can not see. And in terms of mechanical properties, the presence of graphite in the cast iron is equal to the existence of holes, shedding or not, little effect. So the above rules are clearly superfluous. On the contrary, due to the standard to confirm the existence of graphite off the pinhole also brought confusion, often someone to the form and graphite finished