Butt-weld elbows are a common pipe connector, primarily used to change flow direction, reduce fluid resistance, and connect directly to steel pipes by butt welding. They are made of steel and can be formed by hot pressing or forging. They are categorized by curvature radius as long (1.5D) or short (1D), and by angle as 45°, 90°, and 180°. They are widely used in industries such as petrochemicals, power generation, shipbuilding, chemicals, and food, and are a vital component of various industrial piping systems.