X0101 EFFECT 33 LIVE 2020-03-25 16:00:00

S-4

0000018172 A. M. Castle & Co. 333-236682 0001545603 Total Plastics, Inc. 333-236682-07 0001545607 Keystone Tube Company, LLC 333-236682-06 0001803191 Keystone Service, Inc. 333-236682-05 0001803165 HY-Alloy Steels Co 333-236682-04 0001803272 Castle Metals de Mexico, S.A. de C.V. 333-236682-03 0001803210 Castle Metals de Mexicali, S. A. de C. V. 333-236682-02 0001803234 A.M. Castle & Co. (Canada) Inc. 333-236682-01