共查询到19条相似文献,搜索用时 171 毫秒
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对马钢生产的耐火H型钢MGFR490B和Q345B H型钢进行了对比试验研究,完成了高温拉伸和高温持久两项力学性能测试和对两种钢微观组织的观察研究。结果表明,耐火H型钢MGFR490B的组织为多边形铁素体﹢珠光体﹢少量贝氏体混合多相组织,此种组织在高温下能保持很好的稳定性,并能在高温下析出合金碳化物,这对降低耐火H型钢MGFR490B的室温屈强比和保持高温屈强比小的波动范围有益。耐火H型钢MGFR490B获得了比Q345B H型钢好的高温强度性能,这与耐火钢的混合多相组织及添加合金元素密不可分。耐火H型钢MGFR490B在600 ℃高温下能保持高的强度,并且其持久断裂时间超过3 h,满足耐火钢的性能指标要求。 相似文献
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《热加工工艺》2018,(24)
对比了喷射成形新型热作模具钢与商用H13钢的性能差异,利用SEM和TEM进行微观组织分析,研究了合金元素对组织性能的作用规律。结果表明:喷射成形新型热作钢在韧性与H13钢相当的情况下,具有更高的回火抗性和高温强度。新合金在650℃回火时,组织仍然保持马氏体形态,在板条内发现了大量弥散细小的针状Mo2C,钉扎位错,推迟了马氏体的回复;而H13钢650℃回火组织中马氏体已经失去板条形态,位错密度大大降低,碳化物也明显聚集长大。仅仅降低钢中的Cr就可以明显提高新合金钢的回火抗性与高温强度,进一步增加Mo含量对高温强度影响较小,V含量的增加极大地增加了淬火后未溶碳化物的数量与尺寸,降低了固溶到基体的合金元素含量,反而降低了冲击韧性、回火抗性以及高温强度。 相似文献
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采用SEM、TEM以及拉伸测试等研究SCM435钢在870℃淬火、350~650℃回火后的组织和力学性能。结果表明,回火温度为350℃时,其组织是板条马氏体及少量碳化物;随着回火温度的升高,马氏体的板条形态逐渐消失,碳化物沿板条方向析出长大,其中525℃回火后的组织尚有明显的马氏体板条形态并弥散分布着短棒状渗碳体。在试验回火温度范围内调控SCM435钢的力学性能,可以满足8.8~12.9级紧固件的力学性能要求。试验验证了870℃淬火+525℃回火钢的疲劳性能,中值疲劳极限σa50为425 MPa,具有较好的疲劳性能。 相似文献
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采用低Mo及Ti的复合微合金化,设计3种试验钢配以合理的控轧控冷工艺,成功开发出低成本460 MPa级耐火钢。力学性能测试及显微组织分析结果表明,控轧控冷后水冷,试验钢板获得耐火钢的理想组织:粒状贝氏体和M/A岛。随Ti含量的增加,3种试验钢的平均晶粒尺寸递减。3种试验钢的室温屈服强度都大于460 MPa,600 ℃保温3 h的高温屈服强度都大于307 MPa,具有良好的高温力学性能。在相变强化、析出强化、细晶强化及位错强化的共同作用下,不同Ti含量的试验钢获得了良好的高温力学性能。0.07%Ti含量试验钢的YS值(600 ℃屈服强度/室温屈服强度)为0.68,完全满足耐火钢的使用标准。 相似文献
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采用OM、SEM、TEM、拉伸试验和冲击试验等,研究了600 ℃回火不同时间对690 MPa级高强抗震耐火钢板的力学性能、微观组织及析出行为的影响。结果表明,不同回火时间对耐火钢板的力学性能和微观组织有重要影响。耐火钢板经过600 ℃回火后强度稍有降低,但伸长率增大,屈强比降低,综合力学性能提高,低温冲击吸收能量随回火时间的延长而降低。最优回火保温时间为15 min,此时试验钢板的屈服强度为976 MPa、硬度为396 HV,-40 ℃冲击吸收能量为164 J,其组织由贝氏体+铁素体+少量马氏体构成,在马氏体和铁素体中均存在位错和细小析出相,析出相为富Nb的Nb、Ti复合碳化物,发挥沉淀强化作用;当保温时间延长至60 min后,析出大量细小Nb、Ti和Mo复合碳化物,但此时的沉淀强化作用不能弥补铁素体造成的强度损失,所以在相同温度回火过程中,随着回火时间的延长,抗拉强度和硬度下降。 相似文献
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Microstructure and properties of nippon fire-resistant steels 总被引:2,自引:0,他引:2
The microstructure and mechanical properties of two fire-resistant steels manufactured by Nippon Steel were investigated.
Microstructural observation was carried out using optical microscopy, transmission electron microscopy (TEM), and scanning
electron microscopy (SEM). It was found that the good hightemperature strength and creep properties of these steels are due
to the high lattice-friction stresses, which are a result of the very fine distribution of metal carbide (MC) precipitates
and molybdenum in solid solution. In addition, a strong secondary wave of precipitation at approximately 650 °C was observed.
This lattice friction stress maintained strength up to 600 °C. 相似文献
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TC4合金TIG焊接头组织转变与力学性能分析 总被引:2,自引:2,他引:2
针对TC4合金TIG焊接头微观组织特征以及焊接过程中的组织转变规律进行了研究,并对接头力学性能进行了分析.经历TIG焊接热循环之后,焊缝及热影响区粗晶区晶粒严重粗化,热影响区晶粒尺寸具有突变特征,过渡区组织呈带状分布,不存在明显的细晶区.升温过程中(α+β)→β转变过程包括两个阶段:原始β→高温β转变和原始α→高温β转变,而且在原始α→高温β转变开始之前,原始β→高温β转变已经完成.冷却过程中在β→α'转变区间冷速较慢时,α'相首先在高温β晶界上形核,并向晶内生长,生成针状α';在快速冷却时,α'相在晶内大量形核,形成"筐篮"组织.硬度测量结果表明,粗晶区部位存在一个软化区;接头抗拉强度与母材接近,接头性能优异.Abstract: The microstructure and phase transformation of TC4 alloy weld joints during TIG welding were investigated. The mechanical properties of the welded joints were also tested. When the TC4 alloy was heated by TIG arc, grains in the weld bead and heat affected zone (HAZ) were badly coarsening. The grain size in HAZ has mutant character. The microstructure in the transition region presented zonal distribution. There was no obvious fine grained region. In temperature-rise period, the transformation of (α + β)→β was divided into two processes which included the original β→ high-temperature β and the original α→ high-temperature β. And the previous phase transformation was finished before the next starting. In the cooling process, slowly cooling rate introduced α' phases nucleating at the high-temperature β grain boundary in the β→α transform temperature range. The α' martensite grew up into the center of the β grains and generated acicular martensite. With quicker cooling rate, large numbers of α' phase nucleated in the high-temperature β grains and generated orthogonally oriented martensites. Hardness measurements show there is a softened zone in HAZ. Tensile strength of welded joint was approximate with the base metal. And the properties of the welded joints were good. 相似文献
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采用Gleeble-3500热模拟试验机、拉伸试验机和光学显微镜研究了连续退火工艺中均热温度、缓冷温度和过时效温度对980 MPa级复相钢力学性能及组织的影响规律。结果表明,经连续退火处理后980 MPa级复相钢组织为典型的铁素体、贝氏体、马氏体组织,随均热温度的提高,贝氏体和马氏体含量逐渐增加,从而提高抗拉强度和规定塑性延伸强度;缓冷温度则能改变新生铁素体晶粒大小及马氏体含量,从而调控复相钢力学性能;随着过时效温度的升高,部分颗粒状碳化物开始析出,能够降低马氏体的强度即改善复相钢塑性。从多元调控的角度逐步优化980 MPa级复相钢的综合力学性能,最终确定均热温度800 ℃、缓冷温度700 ℃和过时效温度340 ℃为最优工艺参数。 相似文献
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采用盐浴对两种硅含量不同的试验钢进行了淬火配分处理,并用金相显微镜、扫描电镜与拉伸试验机对不同淬火温度下试验钢组织及性能的转变规律展开了研究。结果表明,试验钢的显微组织由铁素体、马氏体、残留奥氏体与贝氏体组成;硅含量增加,有利于试验钢中残留奥氏体体积分数提高,抗拉强度和屈服强度显著提高,伸长率降低,强度随淬火温度变化的幅度减小;经260 ℃淬火、360 ℃配分后,2.13%(质量分数)Si钢在拥有高强度的同时保持了较好的伸长率,其抗拉强度为958.66 MPa,屈服强度为458.99 MPa,伸长率为15.35%,强塑积为14.66 GPa·%,综合力学性能最佳。 相似文献
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The microstructure and mechanical properties of NiCrMoV-and NiCrSi-alloyed medium-carbon steels were investigated after multiple tempering. After austenitising, the steels were hardened by oil quenching and subsequently double or triple tempered at temperatures from 250 to 500 °C. The samples were characterised using scanning electron microscopy and X-ray diffraction, while the mechanical properties were evaluated by Vickers hardness testing, V-notched Charpy impact testing and tensile testing. The results showed that the retained austenite was stable up to 400 °C and the applied multiple tempering below this temperature did not lead to a complete decomposition of retained austenite in both steels. It was also found that the microstructure, hardness and impact toughness varied mainly as a function of tempering temperature,regardless of the number of tempering stages. Moreover, the impact toughness of NiCrMoV steel was rather similar after single/triple tempering at different temperatures, while NiCrSi steel exhibited tempered martensite embrittlement after single/double tempering at 400 °C. The observed difference was mainly attributed to the effect of precipitation behaviour due to the effect of alloying additions in the studied steels. 相似文献