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根据强化低碳位错马氏体的指导思想研制的低碳多元低合金钢25SiMnCrNiMoV经简单的淬、回火处理后,其强度σ_b≈180kg/mm~2,σ_(0.2)≈150kg/mm~2左右,K_(1c)≈400kg/mm3/2以上,其强韧性已超过4340,300M钢,且可与18Ni马氏体时效钢媲美。 透射电镜观察表明,25SiMnCrNiMoV钢淬火后具有自回火ε相,其组织以位错马氏体为主,两相有时具孪晶关系;两邻接位错马氏体与其间残余奥氏体体膜间可分别遵循K-S及N-W关系;钢中除位错马氏体外,也存在一定量内孪晶的位错马氏体,个别部位尚见孪晶马氏体,500℃2h回火后孪晶仍然存在,钢的低温回火性能与之无关。Si的加入增加了ε相的稳定性,减缓了马氏体的分解,将TME推迟到500℃左右,对残留奥氏体的起始分解及TME的上限起始温度似乎没有什么影响。本材料的脆性与残留奥氏体失稳分解,断续碳化物在马氏体板条界,以及碳化物在孪生面的析出有关。
The low carbon multi-element low-alloy steel 25SiMnCrNiMoV developed according to the guiding ideology of strengthening low-carbon dislocation martensite has a strength of σ_b≈180kg / mm ~ 2 and σ_ (0.2) ≈150kg / mm ~ 2 after simple quenching and tempering treatment, 2 or so, the K_ (1c) ≈400kg / mm3 / 2 or more, its toughness has more than 4340,300 M steel, and comparable with 18Ni martensitic aging steel. Transmission electron microscopy showed that 25SiMnCrNiMoV steel with self-tempering ε phase after quenching, the organization of the main dislocation martensite, two-phase sometimes twins; two adjoining dislocation martensite austenite body along with retained Between the KS and NW can be followed respectively; in addition to the dislocation martensite in steel, there is also a certain amount of twins dislocation martensite, twinned martensite still appears in some parts, after tempering 500 ℃ 2h twins Still exists, the low temperature tempering of steel has nothing to do with it. The addition of Si increases the stability of ε phase and retards the decomposition of martensite. The delay of TME to about 500 ℃ seems to have no effect on the initial decomposition of retained austenite and the initial onset temperature of TME. The brittleness of this material is associated with the decomposition of retained austenite, the discontinuities of carbides in the martensite lath and the precipitation of carbides in the twin surfaces.