Nitrogen as the Alloying Element in Steels. I : On the Effect of Nitrogen on the Temper-Brittleness in Steels

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The present investigation has been carried out to ascertain the effect of nitrogen on temper-brittleness in steels, the effect of nitrogen was first examined with the impact test on carbon steels and on low manganese steels, both containing different amounts of nitrogen. From these investigations it became clear that the temper-brittleness in medium carbon steels begins to appear with the addition of 0.010 percent of nitrogen and become conspicuous as the nitrogen content increases, owing to the solubility change at temperatures below about 580°. We also confirmed that molybdenum or tungsten is not always necessary to prevent the temper brittleness, but if the free nitrogen in iron is stabilized in the form of nitrides by adding the elements possessing a higher affinity with nitrogen and these nitrides undergo no solubility change for α-iron the temper brittleness may be prevented. Hence aluminium and titanium have been studied as fixers of nitrogen. From these investigations it became clear that the temper-brittleness decreases or almost disappears by the addition of these elements. Carbon had little effect on the temper-brittleness even if it had been at temperatures below 600℃.
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