My brother tried that once, it worked until he started his car. HEHE! I would suggest just taking it to a shop or welding it the correct way. I have heard of using it to spot like little tiny spots and shit like that but not actual pipes together. One of my buddies used it to repair a small mis hap on his transmission and yeah it worked fine for that.
If you don't want to weld the system just get some HD exaust clamps. They work fine if you use them correctly, and they make the system easier to work on later if you decide you want to change anything.