The improvement of casting quality requirements will lead to the reduction of machining allowance and defects. Therefore, some precision heat-resistant steel castings deflectively cast in air or vacuum, previously considered qualified, are now judged as scraps. Typical examples of this situation are surface defects of heat-resistant and corrosion-resistant steel castings, a previously acceptable defect known as "corrosion".

In actual production, it is often necessary to analyze casting defects in order to find out the causes of defects, so as to take measures to prevent them. For the designer of precision casting, it is helpful to know the defect of product and its causes, to design the casting structure correctly, and to draw up the technical requirements appropriately according to the actual conditions of casting production.
There are many defects in precision casting. The causes of defects are very complex. Sometimes it can be seen that there are many defects caused by different reasons on the same casting, or that the same reason may cause many defects when the production conditions are different.

Whether the defective precision castings are regarded as scrap or not must be determined according to the use and requirement of the castings and the location and severity of the defects. Generally, if there are minor defects, it can be used directly; if there are medium defects, it can be used after repair; if there are serious defects, it can only be scrapped.