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本文研究了几种Cr-Ni-Mo钢的过热特征,提出把断口表面出现延性沿晶小平面作为过热的判据。在高的奥氏体化温度下,某种第二相粒子可以固溶,随后在冷却过程中沿高温奥氏体晶界重新析出,因而产生各种过热现象。MnS粒子的重新析出使普通硫含量的Cr-Ni-Mo钢发生沿晶延性破断,而AlN或VC粒子在高温奥氏体晶界的重新析出也能使低硫的Cr-Ni-Mo钢过热。稀土元素对几种Cr-Ni-Mo钢的过热都有抑制作用。当RE/S达到临界比值(约为4)时,不仅使MnS夹杂物完全转变成稀土硫化物和稀土硫氧化物,而且使高温奥氏体晶粒显著细化,改善韧性。如果RE/S比值远大于4,多余的稀土元素还可能与C,N原子发生交互作用。
In this paper, the overheating characteristics of several Cr-Ni-Mo steels were studied, and the criterion of ductility along the crystal facets as the overheating was proposed. At high austenitizing temperatures, some second-phase particles can be solutionized and subsequently recrystallize along the high-temperature austenite grain boundaries during cooling, resulting in various overheating phenomena. The re-precipitation of MnS particles causes a ductile rupture of the Cr-Ni-Mo steel with normal sulfur content along the crystal, and the re-precipitation of AlN or VC particles at high-temperature austenite grain boundaries also overheats the low-sulfur Cr-Ni-Mo steel . Rare earth elements have some inhibitory effects on overheating of several Cr-Ni-Mo steels. When RE / S reaches the critical ratio (about 4), not only the MnS inclusions are completely transformed into rare earth sulfides and rare earth sulfur oxides, but also the high temperature austenite grains are remarkably refined to improve the toughness. If the RE / S ratio is much larger than 4, the excess rare earth elements may also interact with C and N atoms.