2.25Cr-1Mo与2.25Cr-1Mo-0.25V钢冷却转变对比分析

采用相变仪、光学显微镜及扫描电镜研究了2.25Cr-1Mo和2.25Cr-1Mo-0.25V钢冷却转变过程,并分析了钒对其冷却转变的影响。结果表明,与2.25Cr-1Mo钢的CCT曲线相比,2.25Cr-1Mo-0.25V钢铁素体转变区及贝氏体转变区均向右移,并且在现有试验条件下已无法观察到珠光体转变区;钒添加到2.25Cr-1Mo钢中,能够提高钢的淬透性,2.25Cr-1Mo-0.25V钢在48 000 ℃/h冷速下能生成部分马氏体;钒能够细化钢板显微组织,与2.25Cr-1Mo钢相比,2.25Cr-1Mo-0.25V钢在800 ℃/h冷速下组织更为细小。     

2.25Cr-1Mo-0.25V低合金钢用焊接材料的检验

0前言2.25Cr-1Mo-0.25V钢是制造加氢反应器的首选材料,但是其配套焊接材料开发难度大,比主体材料开发晚将近10年。国内制造的2.25Cr-1Mo-0.25V钢加氢反应器用低合金钢焊接材料全部依赖进口。在高温高压临氢工况下,2.25Cr-1Mo-0.25V钢及其焊缝容易发生回火脆化及低温韧性降低等材料劣化现象。目前,国内生产的2.25Cr-1Mo-0.25V钢性能已达到较高水     

在役2.25Cr-1Mo钢不同氢含量条件下韧脆转变行为

基于Charpy冲击实验研究加氢反应器用2.25Cr-1Mo钢长期高温服役后的回火脆化倾向.为了研究氢含量对该材料韧脆转变行为的影响,对已发生一定程度回火脆化的2.25Cr-1Mo钢进行电化学充氢处理,分别将试样氢浓度控制在2×10-6和4×10-6.对充氢后的试样进行Charpy冲击实验和慢速率拉伸试验,并对冲击断口形貌进行宏观与微观观察与分析.结果表明2.25Cr-1Mo钢长期高温服役后有较大的氢脆敏感性,充氢使2.25Cr-1Mo钢的韧脆转变温度升高,断口中出现沿晶断裂特征,且随着氢含量的增加,其韧脆转变温度持续升高,沿晶断裂特征所占比例增加.最后对2.25Cr-1Mo钢受回火脆与氢脆共同作用下的韧脆转变机理进行了探讨.     

回火温度对2.25Cr-1Mo-0.25V钢粒状贝氏体显微组织和力学性能的影响

利用纳米压痕仪,OM,SEM,TEM,XRD,EPMA等设备研究了加氢反应器用2.25Cr-1Mo-0.25V钢正火态粒状贝氏体组织及力学性能随回火温度的变化.结果表明,2.25Cr-1Mo-0.25V钢正火后得到由贝氏体铁素体、马氏体和残余奥氏体岛(M-A岛)组成的粒状贝氏体组织.纳米压痕测量结果表明,由于M-A岛中富集C,其硬度显著高于贝氏体铁素体.在回火过程中,M-A岛分解和贝氏体铁素体软化的综合作用导致了2.25Cr-1Mo-0.25V钢在-18℃的冲击功随着回火温度的升高先增加后减少.除了铁素体基体回复再结晶软化效应外,粒状贝氏体组织中硬相M-A岛回火转变程度以及析出碳化物形貌、尺寸和分布是影响2.25Cr-1Mo-0.25V钢冲击韧性的关键因素.     

2.25Cr-1Mo钢相变塑性的实验研究

试验测定了2.25Cr-1Mo钢贝氏体相变的相变塑性变形,并观测了相变塑性变形随相变进程的演化规律.根据试验结果确定了相变塑性模型.试验测定了应力对2.25Cr-1Mo钢贝氏体最大转变量和相变动力学参数的影响系数.     

调质态2.25Cr-1Mo-0.25V钢的显微组织与电化学腐蚀性能

对2.25Cr-1Mo-0.25V钢进行950 ℃淬火,再分别进行600 ℃和700 ℃回火,观察其显微组织和碳化物形貌,并测试了其耐蚀性。结果表明,2.25Cr-1Mo-0.25V钢在950 ℃淬火+ 600 ℃回火后具有较好的耐蚀性,而在950 ℃淬火+ 700 ℃回火后的耐蚀性变差,这是由于提高回火温度后大量合金碳化物析出,使合金元素流失,致使2.25Cr-1Mo-0.25V钢表面的氧化膜不能有效形成,导致耐腐蚀性下降。     

制造加氢反应器用2.25Cr-1Mo-0.25V钢的焊接性能试验

2.25Cr-1Mo-0.25V钢是一种抗氢用钢,该新型Cr-Mo钢与普通的2.25Cr-1Mo钢相比,各方面都有明显的优势:强度及许用应力、最高使用温度高,抗氢性能好,能够满足更苛刻的操作工况的需要,使用该钢的设备质量更趋轻量化.介绍了该钢种开发过程中的焊接性能试验结果,掌握用该材料制造加氢反应器的焊接工艺技术,为应用该种材料制造加氢反应器奠定了基础.     

2.25Cr-1Mo-0.25V钢高温流变应力的BP神经网络模型

以2.25Cr-1Mo-0.25V钢热压缩实验得到的数据为样本,采用BP神经网络的方法建立了以应变、应变速率、变形温度为输入和流变应力为输出的流变应力模型,并采用遗传算法优化了网络的初始权值和阈值。结果表明,利用BP神经网络建立的2.25Cr-1Mo-0.25V钢热变形人工神经网络模型的可行性较高,拟合程度是0.52%。该模型较精确地预测了2.25Cr-1Mo-0.25V钢的高温流变行为,为更加合理地制定热工艺参数提供了依据。     

2.25Cr-1Mo-0.25V纯净钢的冶炼及效果

分析了2.25Cr-1Mo-0.25V纯净钢的冶炼难点,同时对低硅钢的冶炼工艺进行了深入的分析研究,提出了采用钢包炉用铝预脱氧并进行VD的冶炼工艺方案和真空浇注过程中严密保护防止二次氧化的工艺思路,并制作了中间包双气封保护装置,实际使用效果十分理想,所炼钢的质量达到了纯净钢的要求。     

淬火温度对2.25Cr1Mo0.25V钢组织与耐蚀性能的影响

对2.25Cr-1Mo-0.25V钢经950、1100和1200℃淬火处理后的显微组织、表面形貌和耐腐蚀性进行研究。结果表明,2.25Cr-1Mo-0.25V钢经淬火处理后的显微组织为贝氏体,随淬火温度的升高,显微组织的晶粒尺寸变大,钢中碳化物由粒状分布变为连续的条片状分布。与1100、1200℃淬火处理相比较,2.25Cr-1Mo-0.25V钢经950℃淬火处理后,在3.5%NaCl溶液中的腐蚀速率降低,自腐蚀电流密度减小,电荷转移电阻增加,耐腐蚀性能提高。     

The Influence of the Rare Earth Element Ce on the High-Temperature Oxidation Kinetics of Low-Cr Steels

The oxidation behavior of steels containing low-Cr concentrations (0.5-2.25 wt.%) has been studied in laboratory air in the temperature range of 400-550 °C. The oxidation rate of the steels was lower than that of pure iron, but higher than that of pure iron when a small amount of rare earth element cerium (0.03 wt.%) is added to the 2.25Cr1Mo steel. The mass change follows a nearly parabolic law for the case of pure iron and the steel without Ce addition, while linear behavior describes the oxygen uptake for the case of the 2.25Cr1Mo+0.03Ce steel. SEM cross-section observations and thermodynamic calculations confirm that there is no wustite (FeO) formation during oxidation of pure iron and low-Cr steels at 550 °C, whereas FeO might be formed in the oxide scale of 2.25Cr1Mo+0.03Ce at the same oxidation conditions (temperature, atmosphere, and exposure time). By investigating the temperature for FeO stability, this study reveals that the temperature for FeO formation on pure iron is 568 °C, for the 2.25Cr1Mo steel 589 °C, and 471 °C for the 2.25Cr1Mo+0.03Ce. This low value for the FeO stability temperature found for the steel 2.25Cr1Mo+0.03Ce steel explains why this steel oxidizes very fast at 550 °C.     

预变形高温扩散对合金元素分布和组织的影响

文章提出了2.25Cr-1Mo-0.25V钢锭高温扩散的改进措施,研究了高温扩散前进行不同程度的预变形对合金元素均质化过程以及组织均匀过程的影响。实验结果表明,与无预变形高温扩散相比,预变形后进行高温扩散,在相同保温时间下Cr、Mo元素的偏析比减小,且变形量越大,偏析比越小。预变形可大大缩短枝晶组织消除所需的保温时间。提出2.25Cr-1Mo-0.25V钢锭在1200℃高温扩散时,先进行20%的预变形再保温的建议。     

2．25Cr-1Mo-0．25V与Q345R异种钢焊接技术应用

在加氢容器生产制造过程中,常涉及到裙座材料Q345a与简体2．25Cr-1Mo-0．25V钢的焊接。通过实验和工艺评定,采取了先在2．25Cr-1Mo-0．25V钢一侧预堆焊一层低碳钢过渡层,热处理后再与Q345R钢组焊在一起的方法,克服了直接对两种母材进行焊接的不足之处,并且改善了焊接接头的综合性能。     

Evaluation of repair welding procedures for 2.25Cr–1Mo and 9Cr–1Mo steel welds

Abstract

Chromium–molybdenum steels are extensively used in the steam generator circuits of power plants. These components may require welding of the cracks that can develop during fabrication, storage, and transportation stages, or during the service life of the plant. This investigation compares repair welding methods for Cr–Mo steels, using 2.25Cr–1Mo and 9Cr–1Mo materials. To simulate aging during service, welds were heat treated at 873 K for 5000 h. Simulated repair welding of the aged welds was carried out at the weld/base metal interface, i.e. at the location at which cracks are usually reported to occur during service. Two repair welding methods (half bead and butter bead temper bead methods) conforming to the ASME Boiler and Pressure Vessel Code were used. Tensile properties, hardness profiles, and X-ray diffraction based residual stress distributions were determined for both the Cr–Mo steel welds to evaluate the simulated repair welds. Analysis of the test results showed that both the repair welding methods can be used for 2.25Cr–1Mo steel welds, although the butter bead temper bead method is much more suitable for both the 2.25Cr–1Mo and 9Cr–1Mo steel welds.     

INVESTIGATION OF INFLUENCE OF HYDROGEN ATTACK ON FATIGUE PROPERTIES OF PRESSURE VESSEL STEELS

1.IntroductionLowalloysteelsexposedtohydrogenatmoderatepressuresandtemperaturessufferalossinmechanicalandfatigueproperties.Thisphenomenon,calledhydrogenattack(HA)['],isduetothemethanegeneratedbychemicalreactioll:abC. 2H2~ac ACHe.Methaneformationmayoccureitheratafreesurface(surfacedecarburization)oratinternalsiteinthemetal(internaldecarburiatioll)suchasgrainboundariesanddefects.Internalmethaneisunabletodiffuseoutofthesteel,anditmaybllildupintheinterllalvoidsandgrainboundaries,growandcoalesce…     

2.25Cr-1Mo与0Cr18Ni9钢焊接工艺研究

在筒体母材为2.25Cr-1Mo钢的大型压力容器生产制造过程中,常涉及到0Cr18Ni9不锈钢内构件与筒节2.25Cr-1Mo钢的焊接。阐述了采用药芯气体保护焊(FCAW)方法焊接该类异种钢的有关工艺要素。通过试验分析了如何调整工艺以改善焊接接头易出现脆化组织的情况,以使接头性能满足产品设计要求。     

低碳中铬钢渗碳层的耐磨粒磨损性能研究

对低碳中铬钢（1Cr6Si2Mo）固体法稀土渗碳层的组织和耐磨性能与渗碳20钢及淬火Cr12Mo1V钢进行了对比试验研究。1C6Si2Mo钢的渗碳层内含有大量粒度为2．5－3．0μm、弥散分布的铬碳化物,其尺寸比Cr12Mo1V钢中的共晶碳化物小。渗碳淬火后的1Cr6Si2Mo钢试样耐磨粒磨损性能大大优于渗碳淬火后的20钢,但不及真空热处理的Cr12Mo1V。     

Cr12Mo1V1钢真空热处理

叙述了Cr12Mo1V1钢的入库检验方法,并详细介绍了Cr12Mo1V1钢的真空热处工艺。     

Embrittlement of a Cr-Mo Low-Alloy Steel due to Low-Temperature Neutron Irradiation

Embrittlement of a 2.25CrlMo steel stemming from neutron irradiation at 270℃ is studied by virtue of small punch testing in conjunction with scanning electron microscopy. The ductile-brittle transition temperature determined by the small punch test is much lower than that determined by the standard Charpy test. There is some irradiation-induced embrittlement effect after the steel is irradiated for 46 days with a neutron dose rate of 1.05×10-3-adpa/s(displacement per atom per second).     

Naphthenic acid corrosion characteristic and corrosion product film resistance of carbon steel and Cr5Mo low alloy steel in secondary vacuum gas oil

Although naphthenic acid corrosion (NAC) has been studied for many years, the mechanism of NAC is not fully understood. The objective of this paper is to study high-temperature NAC in secondary vacuum gas oil of an industrial crude oil vacuum distillation tower. A high-temperature autoclave was applied to conduct high-temperature corrosion test to investigate NAC behaviour of carbon steel and Cr5Mo low alloy steel at different sulphur contents and total acid numbers (TAN). The result shows that the corrosion rate of carbon steel and low alloy steel is high at low TAN and high TAN while it keeps at a low value at medium TAN. Corrosion product film on Cr5Mo low alloy steel surface is denser and more compact than that of carbon steel at high TAN. The chromium present in Cr5Mo low alloy steel plays an important role in NAC resistance by the formation of Cr₇S₈ film in the inner layer of the scale. Corrosion rates of the two steels in secondary vacuum gas oil are high at low TAN and high TAN, but low at medium TAN which are strange and different from previous experimental results conducted in non-industrial oil solution. A tentative explanation for this new phenomenon is also put forward.