Flat welding flange refers to a type of flange that is connected to a vessel or pipeline with a fillet weld, belonging to the arbitrary flange category. The flange ring comes in two types: with neck and without neck. The structure of the flat welding flange is simple, requiring less material during manufacturing. However, it has less rigidity and sealing performance than the socket welding flange, and is widely used for connecting medium and low-pressure vessels and pipelines.