| 摘要 |
740,474. Making clad plates. CHICAGO BRIDGE & IRON CO. March 17, 1953, No. 7304/53. Classes 83 (2) and 83 (4). Brazing; welding.-In the cladding of a metal plate 20 with another plate 24, the two plates are superposed with a layer of brazing material 23 between them, and the space between the plates is sealed and is then evacuated through a connection 27, and whilst maintaining the vacuum, the plates are heated to the fusion temperature of the brazing material, thereby causing the latter to melt and effect a seal. The edges of the plates are sealed such as by a weld 26. The base-plate 20 is preferably mild steel and the cladding plate 24 is a corrosion or heat-resistant metal or alloy, e.g. stainless or chromium steels, nickel, nickel alloys or aluminium. A stainless steel base-plate may be clad with copper or a mild steel base-plate may be clad with another mild steel plate. The brazing material may be copper, bronze, or alloys of copper and silicon or copper and phosphorus; for cladding steel with aluminium a copper-aluminium-silicon alloy is used. This brazing material may be in the form of powder, film or foil, ribbons or rods or preferably in the form of a foraminous screen. The mating surfaces of the two plates are cleaned by sandblasting and preferably also by washing with hydrochloric acid. The surfaces of the brazing material are cleaned in a similar manner or, in the case of copper, with methyl alcohol. The plates are heated in a gas furnace and the vacuum is continued until the assembly has cooled below the solidification temperature of the brazing material. Slow cooling of the plates causes them to be annealed. Due to the weld 26, the plates 20, 24 will be spaced further apart near the edges when the cladding is completed. This margin may later be trimmed off. The connection part 22 may be plugged or eliminated by trimming. In another embodiment, Fig. 4, the edges of the two plates 30, 32 are sealed by a flexible metal plate 37 welded to the edges of the two plates. A connection 34 leads to a vacuum pump and a second connection 36 may also lead to a vacuum pump or preferably it is connected to a source of non- oxidizing gas such as argon, helium or hydrogen. In this embodiment the plates 30, 32 will be spaced a smaller distance apart at their edges. Two sets of plates may be clad simultaneously, Fig. 6 (not shown). Clad plates may be welded together at their edges, Fig. 7 (not shown), different weld metals 73 and 74 respectively being used for the base metal and cladding metal. In another embodiment, Fig. 8 (not shown), the cladding plate is not welded at its edge to the mild steel base-plate but is covered by another mild steel plate which is edge-welded to the base-plate. Specific examples are given of the cladding process for various metals of various dimensions including the temperatures used for melting the brazing metal. |
