J-B Weld ExtremeHeat is formulated to allow for repairs to iron, steel and metal in high temperature environments (2400°F / 1300°C). When fully cured, this metallic compound can be drilled, machined or sanded. It is great for repairing cracks, small gaps, seam connections or holes in exhaust manifolds, pipe connections, mufflers, catalytic …
https://www.amazon.com/J-B-Weld-37901-Temperature-Resistant/dp/B01IBOBY74