What are the metal parts inserted in the joint root to maintain the root opening during welding called?

The term that accurately describes the metal parts inserted in the joint root to maintain the root opening during welding is "joint spacers." These spacers serve the critical function of ensuring a consistent space between the workpieces, which helps control the weld's penetration and shape. Proper spacing is essential for achieving strong welds and preventing issues such as incomplete fusion or excessive distortion during the welding process.

Backing bars, while also related to welding, primarily refer to a form of reinforcement placed behind the weld joint to provide support and prevent burn-through, making them less focused on maintaining root spacing. Root supports are similar but typically refer to supports placed at the root of the weld joint after the initial parts are joined, rather than maintaining the joint itself during the welding process. Weld braces provide additional structural stability to the assembly but do not specifically address root opening maintenance.