Belleville spring washer (Belleville washer) is a conical disc-shaped spring fastener. It can provide high spring force within small deformation space. It is used for bolted joints to compensate thermal expansion, prevent loosening and absorb vibration. Stacking in series or parallel can adjust load and deflection. Widely applied in heavy machinery, hydraulic equipment, valves, automotive, wind power and high-strength bolt connections. Material: spring steel 65Mn / 50CrV4; surface options: phosphate, black oxide, zinc plating.