Sleeve chain (seamless sleeve) consists of 4 parts: inner chain plate, outer chain plate, pin shaft and sleeve. Qingdao Zhenghe adopts imported raw materials and processing equipment, uses chromizing and isothermal treatment technology, and obtains products with high fatigue and wear resistance through chain precision assembly and automatic strengthening pre-drawing. The product uses the seamless sleeve formed by cold extrusion technology. The sleeve is seamless and not easy to deform. The seamless sleeve and the pin are in contact with each other to improve the wear resistance of the product.