Percentage elongation after fracture is a typical index to characterize the plasticity of the pipe

and the partial size of the pipe such as the welded joint can not carry out a single⁃axis tensile test

and it is necessary to complete the sampling and testing with the help of micro⁃specimen test methods.As a micro⁃specimen test method

the small punch test can be used to obtain a variety of mechanical property parameters.In the current study

the key parameters such as the maximum displacement

the corresponding displacement of the maximum load and the arc length after fracture are correlated to the percentage elongation after fracture of the material mainly through the empirical correlation method.However

the applicability of the above method to pipeline steel is not clear

making it impossible to directly apply to pipeline steel materials.In view of this problem

firstly

the applicability of the above⁃mentioned empirical association method based on different characteristic parameters to pipeline steel was discussed

and then a simplified calculation method for arc length after fracture was provided

and an empirical association formula based on the arc length after fracture for the pipeline steel was formed.On this basis

the thickness effect correction was carried out

and the empirical formula for determining the percentage elongation of pipeline steel material after fracture was established based on small thickness specimens and the reliability was verified.The results show that the maximum error of the percentage elongation after fracture determined by the empirical association formula based on the simplified calculation method of arc length after fracture is 5.08%

and the maximum error of the thickness effect correction formula for the calculation result of small thickness specimen is 5.53%

which proves that the established empirical association formula has good fitting effect and good applicability to pipeline steel

which can provide a theoretical basis for the calculation of percentage elongation after fracture in the local area of other steel grade pipelines.