Following up on its April announcement that it was raising base prices (effective May 6) on 200, 300, and 400 series flat-rolled stainless steel products, steelmaker AK Steel (AKS) announced Thursday that it is now also raising current spot market prices for all of its carbon flat-rolled steel products.

Prices on these products will be going up by "a minimum" of $40 per ton, and this rate hike is effective immediately for all new orders.

Investors responded positively to the development, bidding AK shares up 6.2% in Wednesday trading, to close at $3.62.