Most of the hydraulic cylinder is composed of a cylinder, cylinder head, piston and piston rod and sealing device. The comprehensive performance of the cylinder such as pressure resistance, wear-resistance and fatigue strength, determines the service life of the hydraulic cylinder. The cylinder is usually required to withstand pressure within 20Mpa (continuous pressure), and the application of mixing and pressure can even reach 55Mpa. General hydraulic cylinder made of carbon steel or low alloy cold-drawn steel tube, such as ST52 E355, which treated by usually used to stress annealing. The heat treatment depends on the performance of the steel after cold working conditions of the hydraulic cylinder in actual production are mostly use the following heat treatment process for processing.
Stress relief annealing adopts a heat treatment process lower than the heating temperature of recrystallization, which aims to eliminate the residual stress in the steel tube caused by plastic deformation processing but still retains the cold work hardening, so as to prevent the steel tube from deformation cracking. For ST52 honed tubing material, the specific stress relief annealing process is as follows: heating to 480 ~ 500℃, holding for 180min, after stress-relief annealing, the steel tube is tested. The geometric dimension accuracy and properties are shown in the table below.