METHOD OF SALT BATH NITRIDING FOR PRODUCING IRON MEMBER HAVING IMPROVED CORROSION RESISTANCE AND IRON PARTS

摘要

A new nitriding process by using a salt bath to produce iron and steel parts having excellent abrasion resistance and corrosion resistance are explained. A iron lithium complex oxide layer are formed at the outermost surface of the iron part by immersing the iron and steel parts in a salt bath containing cationic component of Li, Na and K and anionic components of CNO<-> and CO3<2->, where hydroxide compound selected from lithium hydroxide, sodium hydroxide and potassium hydroxide are added to the salt bath. Materials being in a hydrated state or in a free water containing state can be used for preparation or replenishing of the salt bath. An moistend air of (1x10<-2> kg.H2 O) / (1 kg dry air) can be used for mixing the salt bath. Containing ratio of Li, Na, K is preferable where a solidifying temperature of the mixture of carbonates of Li, Na, K in that ratio is lower than 500 DEG C. It is preferable that the mol ratio of Na and K is to be 2 : 8 SIMILAR 8 : 2, the content of CNO<-> is to be 5 SIMILAR 35 wt %, the content of CN<-> in the salt bath is less than 2 wt% and the temperature of the salt bath is to be 450 SIMILAR 650 DEG C.