The sprocket is composed of at least two or more parts, and is mostly composed of A type sprocket and wheel hub, and the product is fixed by welding (two protection welding) method. Compared with the integrated sprocket, the welding sprocket has low cost and many processing procedures. However, the welding sprocket can achieve the diversity of product shapes, which can show the difficult shape of the integrated sprocket through split processing, and can also show the large and heavy sprocket through welding.