GB720229A - Hydraulic or pneumatic stowing tubes - Google Patents

Abstract

720,229. Metal tubes. DEUTSCHE EDELSTAHLWERKE AKT.-GES., BRIEDEN, K., and KUHME, E., [trading as MASCHINENFABRIK, K. BRIEDEN & CO.]. July 29, 1952. [July 30, 1951] No. 19132/52. Class 99 (2). [Also in Group II] A tube through which material is hydraulically or pneumatically forced and which may be of unalloyed or lightly alloyed steel with a carbon content of 0.25 to 0.6 per cent., has ring-like hardened zones 2, or at least one helical hardened zone extending from the inside surface 1 of the wall of the tube through only a part of the wall thickness. The ring-like zones may be perpendicular or inclined to the axis of the tube, and may merge into the unhardened portions 3 of the tube wall. The width of the unhardened zones 3, Fig. 1, and Fig. 2 (not shown), or the hardened zones 2, Fig. 3 (not shown) may increase from the inside to the outside surface 4 of the tube wall. A heating device, e.g. induction heating apparatus, followed by a quenching device may be passed through the tube, or the tube may be passed over the heating and quenching devices, the feeding speed and heating output being so controlled to produce the hardened zones, and the outside of the tube being cooled by liquids or gases or by applying solid or plastic substances, e.g. a tube of silicone traversed by a cooling liquid can be applied to the outside of tube; alternatively, the wall of the tube is hardened throughout its thickness at the zones 2 which a.re afterwards independently tempered or annealed from the outside of the tube so that the zones do not extend to the outer surface 4 of the tube, or the tube may be tempered or annealed throughout its length, e.g. in a furnace, after the production of individual hardened zones extending through the thickness of the tube wall. The tube may be cooled on the inside during the tempering or annealing treatment.