| 摘要 |
901,805. Making sheet materials; brazing. NORTHROP CORPORATION. Oct. 26, 1959 [Oct. 28, 1958], No. 36139/59. Classes 83 (2) and 83 (4). In brazing a honeycomb core panel or like structure the panel components are placed in a flexible metal envelope conforming to the shape of the panel, the envelope is sealed, placed vertically and purged by withdrawing the gas therein and replacing it with non-oxidizing gas below atmospheric pressure with the envelope vertical, the temperature of the envelope and components is raised above the melting temperature of at least certain of the components and then the envelope is rapidly chilled while applying uniform pressure over the sides thereof. A sandwich comprising a honeycomb core 16, Fig. 8, and a pair of panels 18 with a brazing material 20 in foil, powder or other form between the core and panels, is placed in the space formed by depressions 14 in a pair of stainless steel &c. envelope halves 10, Fig. 3, and 12, and the envelope is closed by welding around the edges of the halves. The bottom of the depressions may be covered with a material to prevent liquid brazing metal adhering thereto, a coating of heat-retaining material possibly of varying degrees of emissivity may be provided on the inside and/or on the outside of the envelope to cause more or less heat absorption in panels of varying thickness and a removable mask having cutouts may be placed outside of the envelope to control the heat absorption. The envelope is first evacuated and then inert gas, e.g. argon, helium, &c. is flowed into the envelope and this cycle is repeated several times, finally leaving inert gas below atmosphere pressure within the envelope. The evacuation and introduction of inert gas takes place through conduits 26, 28 arranged in arms 22 of the envelope. The envelope in a vertical position is hooked on a pair of hooks 38 suspended from a roller unit 34 on an I-beam 32 and is moved to between a pair of quartz lamp radiant heaters and gold reflectors 43 constituting a preheater stage. The envelope is then moved to a final, heating pair of radiant heaters and reflectors 44 where the brazing material is melted. The honeycomb cells being horizontal, the cell walls act as dams to prevent flow of the brazing metal to the bottom of the envelope. The envelope is then moved to between dies 46 having solid or resilient faces and movable together to contact the envelope, thus cooling and preventing distortion. The dies may be provided with cooling or heating medium. The I-beam may be vertical or the envelope may remain stationary and the heating &c. means movable. The preheat stage may be dispensed with or more heating stages may be provided and heating stages may be provided beyond the dies 46 for after heat treatment. Diffusion bonding is referred to. |
