You can work steel with bronze or copper tools just fine. Wood and stone tools will do, even.

Getting it hot enough to work might be harder, although it's surmountable and many stone age peoples managed (and manage!) it. Making tools that are as good as bronze ones isn't as easy for a number of reasons, including that bronze is actually just a good material.

But if it was a steel ingot coated in copper, slap a handle on that and you got yourself a hammer goin baby