Allegheny Technologies Inc. announced that the review period under the Hart-Scott-Rodino (HSR) Antitrust Improvements Act of 1976 has expired for its previously announced acquisition of Ladish Co. The expiration of the HSR waiting period satisfies one of the closing conditions set forth in the merger agreement, which was announced on Nov. 17, 2010. The transaction, which is also subject to approval by Ladish shareholders and other closing conditions, is expected to be completed in the first quarter of 2011.

A Ladish stockholder is seeking to block ATI’s proposed purchase of the company on the grounds that the price is low and harms its stockholders. The lawsuit, filed in federal court in Milwaukee, claims that Ladish and its board breached their fiduciary duty by accepting ATI’s offer.