Final answer:
If the metal is not sufficiently heated during braze welding, the filler metal won't properly flow or bond, resulting in a weak or non-existent joint.
Step-by-step explanation:
When braze welding, if the metal is not hot enough, the filler metal will not flow properly or bond effectively to the base metals.
This insufficient heat leads to a weak joint or possibly no joint at all, as the filler cannot melt and fuse with the base material.
Proper heat is crucial for the brazing process to ensure that the filler metal adequately wets the base metal surfaces and capillary action pulls the molten filler into the joint, creating a strong bond upon cooling.