Pullman-Peabody wants to buy Joy Manufacturing.

Princeton N.J.-based Pullman-Peabody said it will begin the $31-per-share offer for Pittsburgh-based Joy today. Joy has a total of 17.7 million shares outstanding, giving the deal a total value of about $549 million. Pullman-Peabody makes parts for the aerospace, communications, defense and energy industries, while Joy makes equipment and provides related services for coal, mineral and metal mining, oil and gas well drilling, air pollution control, air compression and ore processing.