在冶金产品标准中，除规定相应的力学性能、化学成分、工艺性能、金相组织等这些可测技术指标外，还常规定一些非量化指标，如某些外观缺陷（不允许存在或不允许超过某一限定）。这些缺陷通常是不能通过仪器仪表测量确定的，而主要是通过感观检验而判定其存在及程度。例如：钢 In the metallurgical product standards, in addition to the provisions of the corresponding mechanical properties, chemical composition, process performance, microstructure and other such measurable technical indicators, but also often set some non-quantitative indicators, such as some appearance defects (not allowed to exist or not allowed Exceed a certain limit). These defects are usually not measured by instrumentation to determine, but mainly through the sensory test to determine the existence and extent. For example: steel