Steel cracking at welding heat!!

[Zander94]

Hi guys! Just picked up a bulk find of files from an antique shop some nicholson, simmonds and a few other i cant remember at the moment at less then a Buck a piece, figured I'd try to practice forge welding with them. So i ground all the teeth off a nicholson cut it in half, tac welded it and threw a handle on it and dumped it into a strictly coke fire. First heat went fine, seemed to stick together but after second heat i went to hit it and it simply cracked in half and sent top half of "billet" flying! Any knowledge of why this happened would be greatly appreciated. Area where it cracked was very slightly sparking after i pulled it out of forge. Thanks guys!

[Steve Sells]

normally you get that from over heating, sparking is definitely too hot for high carbon steel.  not all steels forge weld at the same temperature

[Zander94]

Thanks for the response, im new to high carbon steels, does the sparking mean the hc steel it's ruined or can i try to weld again using the 2 pieces that split apart and still makes a decent tool it of it

[basher]

I would assume its ruined. The first thing that happens as carbon steel burnes is that there is heavy oxidation at the grain boundries. The lucky flip side to this is that high carbon steel is much easier to weld together than mild and wrought iron as it can be done at a much lower temeprature.