【正文】 ko, Substrucutral Hardening of Metals and Alloys [in Russian], Nauka, Moscow(1973), p. 64. 10． E. E. Glikman et al., Nature of reversible temper brittleness, Fiz. Met. Metalloved.,36, 365 (1973). 11. Oliver WC, Pharr GM (2020) J Mater Res 19:3 12. Kim JY, Lee BW, Read DT, Kwon D (2020) Scr Mater 52:353 13. Kim JY, Lee JS, Lee KW, Kim KH, Kwon D (2020) Key Eng Mater 326–328:487 14. Kim JY, Lee JJ, Lee YH, Jang JI, Kwon D (2020) J Mater Res 21:2975 15. Kim JY, Kang SK, Lee JJ, Jang JI, Lee YH, Kwon D (2020) Acta Mater 55:3555 16. Dowling NE (1993) Mechanical behavior of materials. Prentice Hall, Englewood Cliffs 17. Kim JY, Lee KW, Lee JS, Kwon D (2020) Surf Coat Technol 201:4278 18. DIN 1717579 (1979) Seamless steel tubes for elevated temperatures 19. Ahn JH, Kwon D (2020) J Mater Res 16:3170 20. Dieter GE (1988) Mechanical metallurgy. McGrawHill, Singapore 。 . This is confirmed by examination of the structure and by the variation of the yield strength with the tempering temperature. Thus, if no changes occurred in the boundary to increase embrittlement, then the variation of Tso with Ttemper would have the form of the dashed line. All theories explaining RTB [1, 2, 10] are based on the recognition of the dominant role of boundary effects. However, damage in the boundaries of prior austenite grains was not typical in our investigation (the fracture of heat 1 after quenching and after tempering was quasibrittle), and no effect of phosphorus was observed, which is evidently explained by the presence of molybdenum in the steel. It follows from the experimental data that the embrittlement of C–Mo–V steels during tempering is affected mainly by carbide formation, more precisely the rebuilding of carbides and factors affecting these processes. The mechanism of this effect can be presented in general terms as follows. With increasing tempering temperatures cementite begins to coalesce, precipitating at 250350 176。 the quantity of Fe3C carbide gradually decreases and the quantity of M7C3 increases. The concentration of strong carbideforming elements in the residues increases: Cr, Mo, and V. This process is particularly well developed at 500600 176。103A long are located near highly misoriented boundaries (grains, colonies of martensite laths, the most misoriented laths, etc.) and in the boundaries themselves. Precipitates of this type were identified by microdiffraction techniques as MTCa carbide. The structure of the steel changes sharply after tempering at 760 176。. Comparing heats 1 and 3, 6, differing in their metallurgical prehistory but similar in vanadium content (~%), one can see that the increase of Tso in the region of the peak is almost the same as for the quenched condition. In amounts of and %, phosphorus has no effect on Tso after the heat treatments tested. The changes in the mechanical properties of the steel during tempering evidently depend on changes in fine structure. Figure 3 shows the microstructure of heat in the quenched condition, after tempering at 600 176。. After tempering at 730 176。. As pared with the quenched condition the increase of Tso at the peak is 100 176。 . When the tempering temperature is raised from 600760 176。 (1 h). Samples were prepared from the plates after quenching and after tempering at 100760 176。 3。 15Kh3MFA類型的鋼都容易脆化，在給定的回火溫度 下 達到高峰。如 元素釩，促進碳化物細化，從而增加二次硬化 [8]，增加脆 化 。 這 原種影響的理 可以概括介紹如下 ， 隨回火溫度 的增加 滲碳 體 開始凝聚，在 250350℃開始沉淀 。因此，如果發(fā)生任何更改的邊界，增加脆化，那么， Tso同 Ttemper變化將有虛線的形式?？梢栽O想， Tso峰 值 是由于在邊界條件的變化。在鉻鉬釩鋼 的的 情況 二次硬化，體現(xiàn)在在 Ttemper = 300 500 ℃ 性能 的增強可能與這些相關的影響 有關 。 因此，氫脆回火過程中鉻鉬釩鋼，作為對 Tso與 Ttemper出現(xiàn)明顯的高峰表現(xiàn)，從我們的實驗結(jié)果。 析出的碳化物回火后的存在也證實了熱物理化學相分析 熱件 1。單元格的平均規(guī)模為 ? 。 帶