金属管环扩张试验是钢管型式检验的一个重要项目，但ISO 8495:2004中对于如何测量扩口试验后管环试样的尺寸却没有规定。在大量钢管环扩口试验的基础上,针对有的钢管扩口试验后断口无法并拢的情况,提出了计算断后管环尺寸的修正公式,并对钢管环的扩张率进行了修正。结果表明: 对于扩口试验后断口无法并拢的试样，直接采用DIN 50137:1977 中的扩张率公式计算得到的扩张率偏大，通过对断后管环尺寸和扩张率公式进行修正后，计算得到的管环扩张率结果更加合理。

Tube-ring expanding test is an important part for steel tube’s type approval test. ISO 8495: 2004 has not clearly explained how to value the dimensions of the tested tubes after expanding test. On the basis of a lot of experiments in the way of ISO 8495:2004, correcting formulas about size and expansion rate are put forward in this paper aimed at the samples of which fractures are open. The results show the expansion rates of the test pieces mentioned above are relatively bigger and are more reasonable corrected by the size and expansion rate correcting formulas.