Nb-Mo微合金高強鋼的強化機理及鋼中納米級碳化物析出行為的研究
發布人：上海艾荔艾合金股份有限公司www.shailiai.cn
更新時間：2016-01-26
采用 SEM, EBSD, HRTEM 和物理化學相分析等技術分別對 Nb (0.1%)和 Nb (0.1%)-Mo (0.19%)微合金低碳熱軋鋼進行了微觀組織形貌、鋼中析出相及強化機理的觀測和分析.
Nb-Mo微合金高強鋼的強化機理及鋼中納米級碳化物析出行為的研究PRECIPITATION BEHAVIOR OF NANOMETER-SIZED?CARBIDES IN Nb-Mo MICROALLOYED HIGH STRENGH STEEL?AND ITS STRENGTHENING MECHANISM OF THE STEEL采用 SEM, EBSD, HRTEM 和物理化學相分析等技術分別對 Nb (0.1%)和 Nb (0.1%)-Mo (0.19%)微合金低碳熱軋鋼進行了微觀組織形貌、鋼中析出相及強化機理的觀測和分析. 結果表明, 與 Nb 鋼相比,?Nb-Mo鋼的組織較為細小, 組織中小角度晶界密度也較高, 且Mo的添加使得Nb的析出率升高, 尺寸在10?nm以下的納米級MC型析出相(Nb, Mo)C含量較高, 這種納米級析出相(Nb, Mo)C具有較低的熟化速率, 不易粗化, 因此具有較高的沉淀強化增量, 這也是 Nb-Mo 鋼強度高于 Nb 鋼的主要原因.?
Recently, increasing attention has been focused on the high strength low alloy (HSLA) steels?mircoalloyed with multiple miroalloying elements, such as Nb-Ti, Nb-V and Ti-Mo, which can form synthetic?carbide in steel, such as (Nb, Ti)C, (Nb, V)C and (Ti, Mo)C. Compared with the simplex carbide, such as NbC,?TiC, those synthetic carbides with nanometer size exhibiting a superior thermal stability do exert their powerful?influence mainly through their precipitation hardening in ferrite. It is reported that the precipitation hardening of?approximate 300 MPa which can be obtained in Ti-Mo-bearing steel was developed by JFE steel, attributing to the?synthetic (Ti, Mo)C particle precipitated in ferrite. However, as common microalloying elements, Nb and Mo are?added synchronously in steel. The strengthening mechanism of Nb-Mo mircoalloyed as-rolled steel and the role of?the carbide precipitated in Nb-Mo mircoalloyed as-rolled steel are rarely reported. Therefore, in the present study,?the strengthening mechanism, microstructure and the precipitate characteristics of Nb and Nb-Mo microalloyed?steels produced by thermo mechanical control process (TMCP) were comparatively investigated by means of?SEM, EBSD, HRTEM and physical and chemical phase analysis, in order to systematically study the synergistic?effect of Nb-Mo addition on the strength of as-rolled steel. The results shows that the microstructure is finer and?the density of low-angle grain boundaries is higher in Nb-Mo microalloyed steel compared with that of in the Nb?microalloyed steel. What’s more, the Mo addition could increase the precipitation ratio of Nb, and the amount of?the MC-type carbide with nanometer size in Nb-Mo microalloyed steel is evidently larger than that of in Nb?microalloyed steel. Those MC-type carbide were identified as synthetic carbide (Nb, Mo)C, exhibiting low?coarsening rate than that of NbC precipitated in Nb microalloyed steel, which thus contributed to a higher?precipitation hardening. This is main reason of the difference in strength between Nb and Nb-Mo microalloyed?steel.?
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