1997 Volume 15 Issue 3 Pages 502-508
The temper embrittlement of the high-temperature type arises in the heat affected zones (HAZs) when the welded constructions of Cr-Mo steels were subjected to the stress-relief (SR) heat treatment in the temperature range above 900 K. In the temperature range below 900 K, there arose four types (the first to the fourth types) of temper emgrittlement as shown by the authors in the previous papers. The temper embrittlement of the high-temperature type (the fifth type) arising in 21/4Cr-1Mo and 11/4Cr-1/2Mo steels was examined in this research in connection with those four types. Charpy impact test was made on the synthetic HAZ specimens tempered at 900 K to 1000 K. Experimental results informed that 21/4Cr-1Mo steel in possiblly embrittled by SR treatment, because the SR temperature of this steel (about 975 K) meets that at which the fifth type arises. Shorter holding time is recommended for avoiding the embrittlement. 11/4Cr-1/2Mo steel is more possiblly suffered from the third type rather than the fifth type, because the SR temperature of this steel (about 925 K) meets that in which the third type arises. The role of carbide particles of inducing the fifth type of embrittlement was discussed in some detail.