Intermediate Pass
The intermediate layer is an additional weld pass between root and cap layers in thick-walled components. It improves strength and distributes stresses, prevents cracks, and increases service life.
Physicochemical Mechanism of Action
The backing strip serves to improve stress distribution in thick-walled components. It creates an additional bond between the layers and prevents cracking by uniform load distribution.
Metallurgical Relevance & Risks in Welding
Without a backing strip, stresses can concentrate, leading to hot cracks and distortion. A proper backing strip prevents these problems and increases the mechanical strength of the component.
Workshop Practice & Instructions
For thick-walled components over 20 mm thickness, a backing strip is required. The weld should be about 1/3 of the total thickness away from the root. Use a steel backing strip with same or higher hardness than the component. Ensure the backing strip is smooth and free of cracks.