Preventing and removing of heat tint

Abstract

Heat tinting is a thickening of the naturally occurring oxide layer on the surface of the stainless steels during welding. The thickness of the oxide layer next to the weld depends on the temperature, heating time, and oxygen concentration in the shielding gas. On stainless steels chromium is drawn from below the surface of the metal to form a chromium rich oxide surface layer. During welding, the shielding gas should be used to prevent hit tint formation. If formed, heat tint must be removed in order that the full corrosion resistance of the finished product is restored after welding. Mechanical and/or chemical methods of removing heat tint, that have been usually applied, are described in this article.

Obrazovanje heat tint-a predstavlja povećanje debljine prirodno formiranog oksidnog sloja na površini nerđajućih čelika, tokom zavarivanja. Debljina heat tint-a u neposrednoj blizini zavarenog spoja zavisi od temperature, vremena zagrevanja i koncentracije kiseonika u zaštitnom gasu. Kod nerđajućih čelika hromom bogat oksid formira se na površini metala, dok je podpovršinski sloj osiromašen hromom. Zavarivanje treba izvoditi u zaštitnom gasu da bi se sprečilo obrazovanje heat tint-a. Ukoliko se formira, ovaj oksid mora biti uklonjen da bi se sačuvala potpuna otpornost prema koroziji zavarenih delova. U ovom radu opisane su mehaničke i/ili hemijske metode za uklanjanje heat tint-a koje se obično primenjuju.