Abstract
By the impact-test the effect of N2 on the temper-brittleness in carbon steels and low manganese steels containing nitrogen was investigated.
Specimens containing different amounts of nitrogen were made by addition of nitrified manganese in required proportions. AN specimens were quenched from 950°, tempered at temperatures from 400° to 650° for 1 to 3 hours, and water quenched or furnace-cooled.
Then the impact-value and vickers hardness were measured. From the present investigation the following results were obtained. That is,
a) The temper-brittleness in medium carbon steels appear by the addition of 0.01% nitrogen and is markedly observable as the nitrogen content increases.
b) The temperbrittleness is not affected by manganese content but increases with nitrogen content.
c) This phenomenon is due to the solubility change of nitrogen in a-iron at temperature lower than about 580°.
d) On heating at. temperatures higher than about 580° the brittleness decreases with the increase of holding time.
e) The impact value of specimens tempered at 600° or 650° and water quenched decreases with time by aging at room temperature probably owing to the carbon.
