Patent GB-969211-A (GB)
Title: Preparation of laminate metal stock by use of organic anti-welding materials
IPC: B21D51/26
Filed: 1960-12-12
Abstract: 969,211. Making internally passaged metal plates; rolling. CONTINENTAL CAN CO. Inc. Dec. 12, 1960 [July 20, 1960], No. 42611/60. Headings B3A and B3M. In a process for producing slitted metal stock from a billet having an internal cavity, an organic compound is placed in the cavity, said compound being liquid at the hot rolling temperature of the billet, the billet is then rolled at a temperature not exceeding 1,100‹ F., and further deformed with air excluded from the cavity. The organic compounds are used as stop-weld materials, and are effective as such down to final thicknesses of less than 0.0001 inch. A billet having a number of longitudinal channels closed at one end is partially or completely filled with stop-weld material at room temperature, the material being in the form of pellets, powder or strip. Alternatively, loading may take place at a temperature at which the stop-weld material is liquid but not damaged by air contact, such as 500‹ F. If the cavities are partially filled and the filling end not sealed, then initial light rolling is carried out at a temperature low enough to ensure that no decomposition of the stop-weld material takes place due to the contact of air, thus reducing the cavity section and spreading the stop-weld material to entirely fill the reduced cavity. The billet is then heated to a hot-rolling temperature (i.e. a temperature above that at which strain hardening becomes impossible), such as 900-1000‹ F. for aluminium, and the hot rolling performed; when the series of light passes is employed, it is preferable for the cross-section of the cavity to be reduced at its lateral extremities (Figs. 1 and 2, not shown), in order to provide a cavity at the conclusion of rolling which is of substantially constant cross-section. The cavities in the billet may be completely filled with stop-weld material and both ends of the cavities closed prior to rolling by peening and welding the billet ends. The laminate may be used in the manufacture of heat-exchangers and as cylindrical bodies for food containers and printing and decorative features may be applied to the exterior of the laminate before or after being cut into single widths. The laminate exterior may also be provided with ribs and grooves for stiffening its walls when opened. . Among the stop-weld materials used are included epoxide, silicone, polycarbonate, polycaprolactam, terephthalic-isophthalic, novola phenolic and terpene resins; polyethylene, polypropylene, iron stearate, aluminium stearate, and polymethyl styrene. The abovementioned materials have molecular weights in the region of 500, become liquids when heated to within the range 500-1000‹ F. under non- oxidizing conditions, and do not suffer deterioration or polymerization in this temperature range when subjected to rolling pressures. These stop-weld materials are used with billet materials such as aluminium, copper, zinc, magnesium and their alloys. The cavities in the billet may be formed by casting the billet about removable cores, by casting the billet about hollow tubes which subsequently become integrated with the billet metal, or by boring or piercing the billet. Where the laminate is to be used for the manufacture of food containers, the tube interior is enamelled or lacquered after fluid inflation and it is preferable to choose a stopweld material which is satisfactorily bonded to the tube interior, is non-toxic, and is compatible with the final coating to be applied. In order to aid the forming of a coating on the cavity surfaces, it is sometimes necessary to roughen these surfaces prior to cavity filling by the use of a suitable etchant. If the stop-weld film becomes discontinuous, or too thin, during rolling, the leading end of the strip may be opened and additional liquid stop-weld material inserted. This additional material is forced through the strip by the nip and a satisfactory film is thereby re-established for further rolling.