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Walking-beam furnace. A continuous-type furnace consisting of two sets of rails, one stationary and the other movable, that lifts and advance parts inside the hearth. With this system, the moving rails lift the work from the stationary rails, move it forward, and then lower it back onto stationary rails. The moving rails then return to the starting position and repeat the process to advance the parts again.
Water quenching. A quench in which water is the quenching medium. The major disadvantage of water quenching is its poor efficiency at the beginning or hot stage of the quenching process.
White cast iron. A cast iron that is essentially free of graphite and most of the carbon content is present as separate grains of hard cementite. White iron exhibits a white, crystalline fracture surface because fracture occurs along the iron carbide platelets.
White layer. Compound layer that forms in steels as a result of the nitriding process.
Widmanstiitten structure. A structure characterized by a geometrical pattern resulting from the formation of a new phase along certain crystallographic planes of the parent solid solution (Fig. 28). The orientation of the lattice in the new phase is related crystallographic ally to the orientation of the lattice in the parent phase. The structure was originally observed in meteorites, but is readily produced in many alloys-ferrous and nonferrous-by appropriate heat treatment.