Fe-Mn-Al-C based alloy articles and parts and their treatments

Articles and parts made of an alloy consisting essentially of by weight 10% to 45% manganese, 4% to 15% aluminum, 0.01% to 1.4% carbon, 3% to 12% chromium, and the balance essentially iron, having the surface thereof treated by high energy pulse heating to provide a surface layer enhanced in chromium to improve the corrosion resistance thereof.

The melting method for producing a Fe-Mn-Al-C alloy which comprises melting ferromanganese and steel scrap in an arc furnace, adjusting the carbon content of the resulting melt to be not more than about 1.4 wt % by oxygen blowing, transferring the resulting melt to a ladle containing the desired aluminum addition, and while maintaining the metal temperature in the ladle in the range of about 1600.degree. to 1480.degree. C., mixing the melt in said ladle by blowing said melt with a non-oxidizing gas to obtain a homogeneous composition and tapping the resulting melt.

Articles and parts made of an alloy consisting essentially of by weight about 19% to about 30% manganese, about 4.9% to about 7.5% aluminum, about 2.8% to 6.5% chromium, about 0.69% to about 1% carbon, up to 2.1% molybdenum, up to 2% copper, up to 0.2% titanium, up to 0.1% columbium, up to about 1% nickel and the balance essentially iron, having the surface thereof treated chemically, electrochemically, or by high energy pulse heating to provide a surface layer depleted in manganese and enhanced in chromium to improve the corrosion resistance thereof.

Surface hardened Fe-Mn-Al-C alloys consisting essentially of 10% to about 45% manganese, about 4% to about 15% aluminum, about 0.01% to about 1.4% carbon, 0 to 12% chromium, 0.01% to 2.5% silicon and the balance essentially iron having a nitrided surface layer formed by nitriding at a temperature between about 400.degree. and 1150.degree. C. with a strong bonding between said surface layer and the matrix of said alloy.

The process for improving the corrosion resistance of an alloy consisting essentially of by weight about 10% to about 45% manganese, about 4% to about 15% aluminum, about 0.01% to about 1.4% carbon, 0 to 12% chromium, and the balance essentially iron which comprises subjecting the surface of said alloy to chemical or electrochemical pickling to provide a surface layer depleted in manganese as compared to the manganese content of the matrix of said alloy.

The process for improving the corrosion resistance of an alloy consisting essentially of by weight about 10% to about 45% manganese, about 4% to about 15% aluminum, about 0.01% to about 1.4% carbon, about 0 to 12% chromium and the balance essentially iron which comprises subjecting the surface of said alloy to high energy pulse heating to provide a surface layer depleted in manganese as compared to the alloy matrix of said alloy.