If you reheat your work and re weld the could shunts it might work but then again you always compress the steel with each weld.You may ruin your work. I'd make a new billet and start over. Remember forge welding is difficult and takes a bit of experience. Folding your billet makes finer lines ,the fewer the folds the the larger the pattern will be. The force of your hammer blows depends on a huge list of variables such as the steel you use ,the thickness of your billet ,and so on. Use consistent force with each weld. Remember your first weld is already stuck . You just need to make the next one stick . I usually strike the steel hard when I make chain because of the thickness of the steel. Oh and another thing ,for the most part there's nothing a press or power hammer can do that a sledge hammer can't accomplish.
Cesare