Hydrogen Permeation Behaviors of Microalloyed TRIP-assisted Annealed Martensitic Steels
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摘要: 通过在0.2% C-1.5% Si-2.0% Mn成分基础上进行Nb、V和Ti微合金化成分设计以及“完全奥氏体区淬火+临界区淬火至马氏体相变点以上温度配分”工艺,获得组织为退火马氏体基体+残余奥氏体的退火型马氏体TAM。对各种钢氢渗透行为的研究发现,微合金元素析出物能够显著抑制氢在钢基体中的扩散行为。Nb、V和Ti处于可比的加入水平时,Nb微合金化钢的氢扩散系数最低,为0.716×10-7 cm2/s,Ti微合金化钢为1.136×10-7 cm2/s,0.052% V钢为2.647×10-7 cm2/s,这些值均低于参照钢。对含钒钢,随着钢中V含量增加,氢渗透时间长,产生的氢陷阱作用增强。认为Nb和Ti在高温析出粗大的碳化物对氢的抑制作用强烈,而V在低温析出的高密度细小、弥散分布的碳化物,使基体具有大量的氢陷阱,保证材料获得强的抑制氢扩散能力。Abstract: In this paper a serials of TRIP-assisted annealed martensitic(TAM) steels had been obtained through niobium,vanadium and/or titanium microalloying additions into a base chemistry of 0.2%C-1.5%Si-2.0%Mn,and a complex heat cycles of double quenching+tempering processes.From the hydroden charging curves microalloyed precipitates have significant effects on delaying/retaining the hydrogen diffusion through steel matrixs.Hydrogen charging test results indicates that when microallying additions are at silimar level,Nb microalloying steel has the lowest apparent hydrogen diffusive index Da=0.716×10-7 cm2/s,Ti steel with moderate Da=1.136×10-7 cm2/s,while value is 2.647×10-7 cm2/s for 0.052%V steel.However,all these values are far lower than that of refered steel with its Da=4.215×10-7 cm2/s.For V-microalloyed steels,the SSRT results show that the hydrogen induced ductility loss ID is 76.2% for 0.2%V steel,compared with 86.5% for V-free steel.The trapping mechanism of the steel containing different V contents is analyzed by means of TDS and TEM observation.It is found that the steel containing 0.2%V can create much more traps and higher activationenergy for hydrogen trapping compared with V-free steel,which is due to VC as hydrogen traps capturing hydrogen.The relationship between hydrogen diffusion and hydrogen trapping mechanism is discussed in details.
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Key words:
- TAM steel /
- microalloyed /
- hydrogen permeation /
- hydrogen trapping site
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