P 15 Chromium steel
5% nitric acid in alcohol is necessary for eatching this steel. Micro-examination reveals a fine acicular structure which, in view of the hardness (D.P.N approx. 410), is considered to be predominantly a bainitic/martensitic structure. A check sample oil quenched from 910 degree Celsius gave a similar hardness value.
At low power particularly, a light network pattern, resulting from coring is apparent in this steel.