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1.
作用应力对2.25Cr-1Mo合金钢回火脆性的影响 总被引:4,自引:0,他引:4
在146.7MPa的作用应力下,对加氢反应器材料2.25Cr-1Mo合金钢(%:0.15C、2.32Cr、0.95Mo、0.011S、0.009P、0.0068As、0.0035Sb、0.0079Sn、0.01V)进行468℃125h和400h的等温回火脆化试验。根据加氢反应器母材试块脱脆、脆化和应力作用3种状态冲击功和温度关系曲线,得出各状态回火脆性转变温度VTr54.2(℃)值和回火脆化度ΔVTr54.2(℃)。结果表明,温度和等温时间是导致材料回火脆化的主要因素,作用应力对2.25Cr-1Mo钢回火脆性的影响不显著。 相似文献
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通过系列冲击试验,结合晶界偏聚理论,研究时效温度对经980.℃淬火和3个不同的温度时效后的2.25Cr1Mo钢的韧脆转变温度的影响.由系列冲击试验结果知,2.25Cr1Mo钢的韧脆转变温度随时效温度的降低而升高.据平衡晶界偏聚理论,说明时效温度越低,磷的平衡偏聚量越大,而对应试样的韧脆转变温度越高,断裂形态由解理方式转变为沿晶方式. 相似文献
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12%Cr耐热钢的脆化一直是材料研究的热点问题,借助于力学性能测试、金相分析、断口扫描分析以及TEM微观结构分析,研究了1Cr12Ni3Mo2VN(M152)耐热钢在淬火、回火以及时效过程中产生的脆性,结果表明:淬火时的冷却速度对冲击韧性有显著的影响,冷却速度过慢将导致不可逆脆性,其脆化机制是由于缓冷时M23C6碳化物沿原奥氏体晶界连续析出,以及回火时残余奥氏体发生分解导致M2C碳化物沿奥氏体薄膜连续析出,杂质元素的原奥氏体晶界偏聚不是产生脆化的原因,导致不可逆脆化的淬火缓冷通过的温度区间为820℃~660℃;与回火温度有关的脆性有二类:450℃~500℃回火产生的(475脆性),脆化严重,其脆化机制是杂质元素的原奥氏体晶界偏聚和脆性相的析出,去脆化处理可以恢复其韧性;另一类是在约625℃回火产生的,脆化程度较轻;高温回火后缓冷引起的脆化很复杂,杂质元素的晶界偏聚、粗碳化物的析出以及二次淬火均导致回火脆性,通过去脆化处理均可以恢复其韧性。杂质元素的晶界偏聚是脆化的主导机制,二次淬火引起的脆化受环境影响非常大,引起的脆化也非常严重,是产品质量不稳定的主要原因。595℃长期时效脆化主要是由碳化物的析出以及杂质元素的非平衡晶界偏聚引起的,临界时间约为100h,通过去脆化处理可以恢复其部分韧性。 相似文献
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本文研究了铈和钼对Ni-Cr-Mo钢在500℃长时间回火过程中的脆化倾向的影响。用AES测定了磷、镍和钼的晶界偏聚,用TEM+EDAX分析了铈的晶界偏聚浓度,测定了钢的FATT_50的变化。结果表明,铈和磷在一定浓度下形成Ce-P化合物,铈和钼综合合金化可减弱中碳CrNi3Mo钢长期回火脆化倾向。文中讨论了铈、钼和磷在钢中的相互作用。 相似文献
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采用Gleeble 3500热模拟试验机研究了轧制和卷取温度下磷元素晶界偏聚与热轧板高温热塑性的关联机制。研究结果表明,含磷钢中磷元素晶界偏聚符合空位-磷原子复合体非平衡共偏聚理论,800 ℃以上轧制温度对磷元素晶界偏聚引起的钢板脆性影响较小,而在500~650 ℃温度范围存在磷元素偏聚导致的热塑性低谷区,且在该温度区施加1%拉伸预应变将加剧磷元素晶界偏聚和钢板脆性。因此,本试验成分含磷钢热轧生产中卷取温度设定应避免550 ℃塑性低谷。 相似文献
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NiCrMoV转子钢回火脆性的研究(Ⅲ)——某些合金元素(锰、钼)对回火脆性敏感性的影响 总被引:1,自引:1,他引:0
本文就某些合金元素Mo和Mn加入到NiCrMoV转子钢中对回火脆性敏感性的影响进行了研究。当加入0.3%Mn以后,该钢的塑脆转变温度(FATT)在所有的时效时间都比不含Mn的相同钢大约提高了一倍。尽管Mn-P有某种共偏聚效果,但FATT的提高主要与Mn本身对晶界结合强度的固有影响以及P的脆化能力提高有关。 比较NiCr转子钢和NiCrMoV转子钢的杂质导致的脆性行为,根据FATT的测定就可清楚地看到Mo的有益贡献。试验结果显示了Mo的清扫剂作用,在体内Mo-P的交互作用而抑制了脆性,Mo与P在晶界的共偏聚从而降低了磷的脆化能力。本文还报告了在长时时效时碳化物中富集磷的试验结果。 相似文献
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The postweld heat-treatment response of simulated coarse-grained heat-affected zones in a new ferritic steel 总被引:1,自引:0,他引:1
J. G. Nawrocki J. N. DuPont A. R. Marder C. V. Robino 《Metallurgical and Materials Transactions A》2001,32(10):2585-2594
The tempering behavior of simulated coarse-grained (CG) heat-affected zones (HAZs) in two ferritic alloy steels, 2.25Cr-1Mo
and HCM2S, was investigated. The hardness of HCM2S was found to be stable at longer times and higher temperatures than the
2.25Cr-1Mo steel, even though the “as-welded” hardnesses were approximately equal. Both materials reached a peak secondary
hardness after tempering for 5 hours at 575 °C. The increase in hardness of the 2.25Cr-1Mo steel was due to precipitation
of Fe-rich M3C carbides within the prior-austenite grains, whereas the secondary hardening in HCM2S was due to a fine dispersion of intragranular,
W-rich carbides. The HCM2S steel retained its hardness at longer times and higher temperatures than 2.25Cr-1Mo steel, because
of the precipitation of intragranular, W-rich carbides and V-rich MC carbides that stabilized the lath structure. This study
shows that HCM2S should not be heat treated in the same way as 2.25Cr-1Mo steel and also provides a basis for defining the
postweld heat treatment (PWHT) of HCM2S. 相似文献
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The phosphorus grain boundary segregation kinetics during tempering at 680°C and aging at 500°C of 2.7Cr-0.7Mo-0.3V steels with phosphorus mass contents of 0.004, 0.014, and 0.027 % was investigated. To determine the grain boundary concentrations of phosphorus the Auger electron spectroscopy was used. Chemical compositions of carbide particles were determined by means of EDX/STEM. Xu Tingdong's and McLean's models of non-equilibrium and equilibrium segregations, respectively, were used to analyze experimental data. It was shown that a phosphorus grain boundary enrichment during tempering was mainly caused by non-equilibrium segregation. During aging the mechanism of the equilibrium grain boundary segregation was prevalent. Slow phosphorus segregation kinetics was observed in the experimental steels during aging. 相似文献
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In order to confirm the segregation characteristic of phosphorus in an Fe-17Cr alloy at grain boundary, the phosphorus segregation was obtained by Auger electron spectroscopy. The results show that a maximum phosphorus segregation appeared at 450 ℃ for all specimens aged for 30 rain at 350, 400, 450, 500, and 600 ℃ after being solution-treated at 1 000 ℃ for 1 h. These results were analyzed by the characteristics of segregation peak temperature of non-equilibrium segregation. 相似文献
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The constant embrittlement curve for constant segregation concentration on grain boundary of impurity element P and relationship between equilibrium grain boundary segregation concentration and operation time for 225Cr-1Mo steel were derived based on the theory of equilibrium grain boundary segregation. The mechanism of step-cooling test and mechanism of de-embrittlement for 225Cr-1Mo steel were explained. The segregation rate will increase but equilibrium grain boundary segregation concentration of impurity element P will decrease as temperature increases in the range of temper embrittlement temperature. There is one critical temperature of embrittlement corresponding to each embrittlement degree. When the further heat treating temperature is higher than critical temperature, the heat treating will become a de-embrittlement process; otherwise, it will be an embrittlement process. The critical temperature of embrittlement will shift to the direction of low temperature as further embrittlement. As a result, some stages of step-cooling test would change into a de-embrittlement process. The grain boundary desegregation function of impurity element P was deduced based on the theory of element diffusion, and the theoretical calculation and experimental results show that the further embrittlement or de-embrittlement mechanism can be interpreted qualitatively and quantitatively by combining the theory of equilibrium grain boundary segregation with constant embrittlement curve. 相似文献
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Phosphorus segregation to prior austenite grain boundaries in low alloy steel from exposure to temperatures of 300 to 600°C results in a susceptibility for intergranular fracture referred to as “temper embrittlement”. It has been observed that alloying steel with Mo greatly reduces the phosphorus segregation kinetics. Therefore changes in the ferrite matrix composition from carbide precipitation and evolution involving Mo can influence the segregation phenomenon and fracture properties. This study uses analytical electron microscopy of extraction replicas to characterize the changes in carbide chemistry of a NiCrMoV bainitic steel with 0.25 wt% C that accompany the phosphorus segregation during aging at 480°C for up to 3400 hr. The steel was doped with 0.02 wt% P and tempered at 650°C to two different hardness levels, i.e., two different initial carbide distributions. The amount of grain boundary phosphorus segregation produced by aging at 480°C correlates with the level of molybdenum that remains in solution in the ferritic matrix whereas changes in vanadium and chromium appear to have less influence on the temper embrittlement. 相似文献
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本文主要研究了2.25C r-1M o钢正火处理后显微组织和回火过程中碳化物相对钢的强韧性的影响,奥氏体化处理后进行冷却(加速冷却和空冷),得到的显微组织为粒状贝氏体和先共析铁素体。对于2.25C r-1M o厚钢板,显微组织和碳化物相的变化是造成2.25C r-1M o钢强韧性能变化的主要原因。 相似文献
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Temper embrittlement of 2.25 Cr-1 Mo steel doped with P and Sn was studied systematically. Carbide extraction by electrolysis,
X-ray diffraction, transmission (replica) electron microscopy, chemical analysis of the matrix, and scanning Auger microprobe
analysis were conducted to determine the effect of carbide precipitation and subsequent variation of the Mo concentration
in solution on the segregation of P. These analyses were correlated with the ductile-to-brittle transition temperature (measured
by use of a slow-bend test), as well as hardness measurements and fractographic information obtained by scanning electron
microscopy. The results indicate that the principal role of Mo is to suppress embrittlement by scavenging of P, presumably
by a Mo-P compound formation, thereby diminishing P segregation. However, due to the stronger interaction between Mo and C,
Mo is precipitated in an M2C carbide during tempering or aging, and the matrix is depleted of Mo. The P thereby released segregates at a rate consistent
with the rate of M2C precipitation. At a Mo concentration >0.7 pct the beneficial effect of Mo is decreased due to enhanced M2C precipitation, the content of Mo in solution remaining essentially constant. The M2C is formed at the expense of Cr-rich M7C3; this results in more Cr in solution, thereby permitting more Cr-P cosegregation, and embrittlement increases. Tin was found
not to produce temper embrittlement in this steel when present at concentrations up to 0.04 pct. 相似文献
18.
Hans Berns Sergej Nikolaijevitsch Bugajchuk Vladimir Andrejevitsch Duz Rüdiger Ehrhardt Valentin Gennadijevitsch Gavriljuk Yuri Nikolaljevitsch Petrov Igor Arkabijevitsch Yakubzov 《国际钢铁研究》1994,65(10):444-450
Hardness measurements, dilatometry, internal friction measurements, Mössbauer spectroscopy and transmission electron microscopy are utilized in order to study the effect of tempering on the microstructure of a stainless martensitic steel containing 15% Cr, 1% Mo and 0.6% N. A similar carbon steel containing 15% Cr, 1% Mo and 0.6% C is used for comparison. Tempering of alloy Fe-15Cr-1Mo-0.6N in the low temperature range of 353-473 K leads to formation of hexagonal ?-nitride (Fe,Cr)2N, which is followed by precipitation of the orthorombic ?-nitride (Fe,Cr)2N at temperatures of 573-773 K. The hexagonal nitride Cr2N is precipitated at 923 K and preferably formed at grain boundaries. The alloy Fe-15Cr-1Mo-0.6C shows the expected tempering behaviour. ?-carbide (Fe,Cr)2C and cementite (Fe,Cr)3C are precipitated during low temperature ageing, followed by the formation of Cr7C3 carbides after the temperature has risen to 873 K. With a similar interstitial content the amount of retained austenite in the nitrogen martensite is nearly twice as high as in the carbon one. Furthermore, the thermal stability of the retained austenite of the nitrogen alloy is substantially higher than that of the carbon steel. 相似文献