He piston rod is made of the precision grinding high-strength alloy steel. Medium-frequency hardening on the piston rod surface makes its hardness reach HRC52~60. The nickel chrome plating and buffing on the piston rod surface is under Rma×0.8, which provides the surface of impact resistance, prevents the piston rod being damaged and extends the lifetime of the sealing elements. The SFA full-automatic robot welding machine and SFA piston rod assembly machine are imported from Korea, and the welding joints are all inspected in UT inspection, ensuring the welding quality.