Roll composite

Perhaps the most extensive appHcation for conversion-rolled, explosion-bonded clads was for U.S. coinage in the 1960s (34) when over 15,900 metric tons of explosion-clad strip that was suppHed to the U.S. Mint helped alleviate the national silver coin shortage. The triclad composites consist of 70—30 cupronickel/Cu/70—30 cupronickel. 

Requirements for tire cord material will to some extent be driven by new vehicle trends. Eor example, the clean air emphasis in North America places lightweight vehicles and materials at a premium. Eor tire cord the fuel economy or rolling resistance provided by the cord—mbber composite may shift the pattern of usage. A common requirement for all types of tire cord surfaces is a high strength-to-weight ratio. 

There is one obvious drawback of high-hysteresis rubber. In normal rolling operation, considerable elastic deformations still take place in the tyre wall, and high-loss tyres will consume fuel and generate considerable heat. The way out is to use a low-loss tyre covered with a high-loss tread - another example of design using composite materials (Fig. 26.9). 

Carbon steels as received "off the shelf" have been worked at high temperature (usually by rolling) and have then been cooled slowly to room temperature ("normalised"). The room-temperature microstructure should then be close to equilibrium and can be inferred from the Fe-C phase diagram (Fig. 11.1) which we have already come across in the Phase Diagrams course (p. 342). Table 11.1 lists the phases in the Fe-FejC system and Table 11.2 gives details of the composite eutectoid and eutectic structures that occur during slow cooling. 

For the manufacture of medium-shock-resisting grades the preblend of resin, filler and other ingredients does not readily form a hide on the mill rolls. In this case the composition is preblended in an internal mixer before passing on to the mills. 

As an alternative to the wet process described above, moulding compositions may be made by mixing a powdered resin or a methylol derivative with other ingredients on a two-roll mill or in an internal mixer. The condensation reaction proceeds during this process and when deemed sufficiently advanced, the composition is sheeted off and disintegrated to the desired particle size. This dry process is not known to be used in any current commercial operation. 

Ebonite compositions may be prepared without difficulty either in an internal mixer or on a two-roll mill. In addition to the rubber and sulphur, fillers are invariably present in commercial mixes. These materials have the important function of diluting the rubber phase. Because of this the exotherm will be... 

Perhaps the most important innovation of all is in the thermomechanical control processes, involving closely controlled simultaneous application of heat and deformation, to improve the mechanical properties, especially of ultra-microalloyed compositions. Processes such as controlled rolling are now standard procedures in steel mills. 

The Nippon Steel Corporation in 1972 pioneered the use of continuous annealing lines , in which rolled steel sheet is heat-treated and quenched under close computerised control while moving. For this advanced process to give its best results, especially when the objective is to make readily shapable sheet for automobile bodies, steel compositions have to be tailored specifically for the process composition and processing are seamlessly tied to each other. Today, dozens of these huge processing lines are in use worldwide (Ohashi 1988). 

For composite stiffeners, all shapes are builtup from individual layers of material. Of course, some stiffener shapes can be produced by roll forming or pultrusion, for example, and then fastened to panels. Or, the stiffened panel could be made in a single operation involving the placement, usually by hand, of individual laminae of various dimensions in positions such that a builtup structure results. Stiffeners can be fastened to panels by bonding, stitching, or mechanical fastening. 

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