Springer Online Journal Archives 1860-2000
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Conclusions 1. During low-temperature aging of soft open-hearth steel (killed and boiling) phases of the nitride type are precipitated and the nitrogen in them is partially replaced by carbon. The independent precipitation of carbon and formation of carbide does not occur until 200° or higher. Clearly, cementite is formed because of the low supersaturation. During low-temperature aging of soft steel, the carbon is precipitated as part of the metastable α″-phase Fe16(N, C)2. This phase can be detected in diffraction patterns after aging at 100° for one hour. The properties are affected to the greatest extent by growth of the α″-phase precipitations and its transformation into theγ′-phase. 2. Particles of theγ′-phase Fe4(N, C), may evidently form from oriented precipitated and inter-growing α″-phase particles. The rate at which theγ′-phase is formed during low-temperature aging depends on the preceding heat treatment and on the composition of the steel. The amount of carbon which, as a result of quenching, remains in the solid solution and then becomes part of theα″-phase probably restricts the coherent growth of the particles of this phase and speeds up the transformation.
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