EFFECT OF THE PRECIPITATION OF Cu-RICH CLUSTERS ON THE DBTT OF RPV SIMULATED STEEL

Abstract

Reactor pressure vessels (RPVs) are usually made of low alloy ferritic steels, among which A508-III steel is a typical one. The long-term neutron irradiation can induce the embrittlement of RPV steels, and the embrittlement may lead to a reduction of the RPV service life. Generally, this behavior of the embrittlement is well established and is typically assessed by the increase in the ductile-to-brittle transition temperature (DBTT) of the RPV steels. For many years, extensive studies have revealed that irradiation-induced ultrafine Cu-rich clusters (CRCs) play an important role and CRCs with high number density cause hardening and embrittlement of the RPV steels. In order to investigate the effect of the precipitation of CRCs on DBTT of RPV steels by thermal aging, it is necessary to increase the Cu content in RPV steel. A 40 kg ingot of RPV simulated steel based on the composition of A508-III steel with higher Cu content (0.6% in mass fraction) was prepared by vacuum induction melting, and it was forged and hot rolled to a plate with 7 mm in thickness. Specimens with a dimension of 7 mm×12 mm ×60 mm were cut from the hot-rolled plate. The heat treatment routes of the specimens consists of a soaking at 880 ¤ for 0.5 h, a water quenching, a tempering at 660 ¤ for 10 h, and a final aging at 370 ¤ for various times. The effect of the precipitation of CRCs on the *