Cracking of Upper Pipe of Hydraulic Prop Made of 32HA Steel: Case Study

Abstract

This article describes the cracking of a hydraulic cylinder pipe made of 32HA steel with an Ar-shielded gas tungsten arc–welded (GTAW) protective housing. Grade 32HA is a Polish grade of steel that contains approximately 0.32% carbon and is designed for use on pipes and tubes for hydraulic cylinders. A fragment of the cylinder pipe and a welded joint of the protective housing were subjected to light microscopy (LM)-based macro- and microscopic metallographic examination. Tests of mechanical properties and impact energy, measurements of hardness, and analyses of chemical composition were also carried out. It was determined that the primary reason for cracking was the overloading of the pipe with the pressure of the working liquid inside the cylinder during operation. It was also ascertained that the welding of the protective housing created a heat-affected zone in the steel; this HAZ was of a very hard and brittle martensitic structure consisting of a structural notch that increased the steel’s susceptibility to cracking in this area.