Rockwell hardness tests shall be made on specimens from two ASTM A179 seamless tubes from each lot. The term lot applies to all tubes, prior to cutting, of the same nominal diameter and wall thickness which are produced from the same heat of steel. When final heat treatment is in a batch-type furnace, a lot shall include only those tubes of the same size and the same heat which are heat treated in the same furnace charge. When the final heat treatment is in a continuous furnace, a lot shall include all tubes of the same size and heat, heat treated in the same furnace at the same temperature, time at heat, and furnace speed. The ASTM A179 tubes shall have a hardness number not exceeding 72 HRB.