50CrVa steel and 51CrV4 steel are named by different standards, 51CrV4 named according to German standard EN 10083, 50CrVa is according to the Chinese standard GB/T 3077. But materials are basically same.

51CrV4 steel is a kind of higher-level spring steel. 51CrV4 steel has good mechanical and technological properties, high hardenability, high fatigue strength and high yield ratio. 51CrV4 steel is used as the important spring of high load with large cross-section and valve spring, piston spring and safety valve spring with working temperature < 300 ℃.