Rocketman...I have driven and folded carbon into mild steel more than I should have, I could have been working for money during that time. The technique is like reloading in that you're stuck adhering to a few concepts that can't be deviated from or falure will occur. For the moment, forget the 30-50 inch continous blacksmith weld that is required for one tube, and try welding the basic lap joint. Without the coal dust and fresh (unburned) ground bone in between the two pieces, to outgas carbon while welding you will get a "cold weld"...Cold welds are where most failures occur. Probaly by not removing all the scale before welding. If you adhere to time tested techniques, like applying the bone to the surface to be welded directly from your sieve, there is little chance of a bone chunk causing an inclusion the way residual scale will. Even if you apply too much bone in one spot, it simply burns off. I spent several years during and after college on the edge of anvil
