Permanent or temporary backing strip
A backing bar is a metal or ceramic aid placed at the root side to support the molten weld metal. It increases the heat input and prevents uncontrolled root sagging.
Physical-Chemical Mechanism of Action
The backing bar absorbs and supports the molten weld metal, increasing the heat input of the weld. This prevents the weld metal from reaching the root and causing uncontrolled sagging.
Metallurgical Relevance & Risks in Welding
Without a backing bar, molten weld metal can flow into the root, causing uncontrolled root sagging and potential cracks. This can affect the strength of the weld and reduce the service life of the component.
Workshop Practice & Instructions
Use backing bars in welding processes with high pressure or high heat input. Place the backing bar at the root side and ensure it is correctly positioned. Incorrect positioning can damage the backing bar itself or impair its function.