A flat welding flange is a type of flange that is connected to a vessel or pipe using a corner weld. It belongs to the arbitrary type of flange. During design, it is checked as an integral or loose flange based on the degree of integration between the flange ring and the straight tube section. Flange rings come in two types: with neck and without neck. Compared to necked butt-welding flanges, flat welding flanges have a simpler structure, use less material, but are not as rigid or sealed as necked butt-welding flanges. Flat welding flanges are widely used for connecting medium and low-pressure vessels and pipes.