Classifying of welding time series based on multi-scale time irreversibility analysis and extreme learning machine

•It is confirmed that the time irreversibility is an intrinsic property of welding time series and it can extend over multiple scales.•The superposition effect of multiple frequency components of welding time series results in enhances time irreversibility.•The MSTI index (Pm%, Gm%) and ELM are used to classify welding quality, and obtain a good classification results.