The heat-affected zone (HAZ) hardness in boron-containing steels increases with an increase in the reheating temperature above the AC3 temperature, and the HAZ hardness gradually decreases with an increase in the reheating temperature after there is a maximum hardness at a certain peak temperature. On the other hand, the HAZ hardness in boron-free steels increases with an increase in the reheating temperature in the austenite region above the AC3 temperature during welding. Boron segregates to the austenite grain boundary during cooling after welding. This is called the non-equilibrium segregation phenomenon. This non-equilibrium segregation during cooling causes the boron concentration in the austenite grain boundary to increase with an increase in the reheating temperature. However, boron begins to precipitate in the austenite grain boundary when the boron concentration in the austenite grain boundary reaches the critical boron concentration required for the precipitation. Therefore, the HAZ hardness begins to decrease with an increase in the reheating temperature after the maximum boron segregation is reached in the austenite grain boundary, which corresponds to the maximum hardness. This is the reason that the HAZ hardness distribution of boroncontaining steels is considerably different from that of boron-free steels.
HAZ hardness distribution of low-carbon boron-containing high-strength linepipe steels
Härteverteilung in der Wärmeeinflusszone von niedrig-gekohlten, borhaltigen, hochfesten Pipelinestählen
2013
7 Seiten, 10 Bilder, 3 Tabellen, 15 Quellen
Aufsatz (Konferenz)
Datenträger
Englisch
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