cant sacrifice artifacts to scrap welder or sac blood harvester
automatically acts as cancelled despite having artifacts available and the creatures are highlighted to activate.
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Rezzahan#77802 commented
Blood Harvester's ability has a sorcery restriction, so can't be sacrificed in combat.
As for the Welder, do you have an artifact card to target in your graveyard? If you can't choose a target, then it doesn't matter if you have artifacts on the field. and you can't target what is not in the graveyard yet, as choosing targets comes way before paying for the ability. And it would have to be a cheap artifact card, mana value 1 or 0, since you only have artifacts with mana value up to 2 available to sacrifice.