| 摘要 |
686,809. Making composite articles. FAIRCHILD ENGINE & AIRPLANE CORPORATION. Dec. 11, 1950, No. 30264/50. Class 83 (ii). [Also in Group XXXIV] In a method of making a composite metal article comprising a ferrous part bonded to an aluminium base alloy part by means of an alloy composed predominantly of the two metals and having opposite thermal stress conditions in the two parts at ordinary temperatures, the thickness of the aluminium alloy part is so chosen that such stress conditions are maintained at high temperatures instead of becoming reversed. The invention is described as applied to making a brake drum having an inner steel drum 10 bonded to an outer heat conducting and dissipating member 11 of aluminium base alloy by a bonding film 12 of ferro-aluminium. When fully cooled from the bonding operation, the outer member 11 will be in tension and the inner member 10 and film 12 in compression as a result of the different coefficients of expansion of the materials. These stresses tend to become reversed and so weaken the bond if the temperature rises, as it may do in use, to between 600‹ and 1100‹ F. For an outer aluminium alloy layer of a thickness exceeding about one inch, the temperature at which the stress reversal occurs is approximately constant and then increases rapidly with decreasing thickness of the layer. The thickness of the layer required in order to avoid stress reversal at a given maximum working temperature may be calculated. The invention may be applied to articles such as pistons, cylinders, bearings and vacuum tube casings. A heatconducting layer may similarly be applied to the sides of a gear-wheel or to the side and flat bottom of a cooking utensil. |
