Multi-step Load Impression Creep Tests for a 1/2Cr1/2Mo1/4V Steel at 565°C

Abstract: Impression creep tests under multi-step load conditions were performed for a service-aged 1/2Cr1/2Mo1/4V steel at 565°C, corresponding to uniaxial stresses in the range of 100–150 MPa. Results of the tests have shown that the minimum creep strain rate data of the material, produced from the creep curves obtained under different load histories, are in good agreement. The results obtained indicate that the results from a multi-step load test of an impression creep specimen, which is particularly useful when the test material is very limited, can be used to obtain the secondary creep properties for a material from a very small test sample.     

汽轮机低压转子1Cr12Ni3Mo2VN不锈钢叶片的开裂原因分析

对某火力发电厂2号汽轮机组末级开裂叶片进行宏观检查、化学成分分析、金相组织以及断口扫描和元素成分能谱分析。结果表明：该叶片裂纹形成属于腐蚀疲劳失效,蒸汽中存在氯、硫等腐蚀介质引起叶片发生电化学腐蚀,在离心拉应力作用下发生沿晶应力腐蚀开裂,形成裂纹源。在腐蚀介质、拉应力和激振力综合作用下,腐蚀疲劳裂纹加速扩展,并最终发生瞬时断裂。     

2.25Cr-1Mo钢后续热处理中的磷偏聚行为

根据溶质晶界偏聚理论和原子扩散原理研究了2.25Cr-1Mo钢服役12年后磷晶界偏聚行为及脱脆处理工艺。采用俄歇电子能谱实验对溶质原子的晶界偏聚程度进行了测试分析。结果表明:对于已脆化的2.25Cr-1Mo钢,存在临界脆化温度,且脆化程度越高,临界脆化温度越低;高于临界脆化温度数小时的保温即可消除脆化现象,即2.25Cr-1Mo钢的脱脆速率远大于脆化速率。     

Optimization of Welding Process Parameters for 9Cr-1Mo Steel Using RSM and GA

Optimization of A-TIG welding process parameters for 9Cr-1Mo steel has been carried out using response surface methodology (RSM) and genetic algorithm (GA). RSM has been used to obtain the design matrix for generating data on the influence of process parameters on the response variables. A second-order response surface model was developed for predicting the response for the set of given input variables. Then, numerical and graphical optimization was performed using RSM to obtain the target depth of penetration (DOP) and heat-affected zone (HAZ) width using desirability approach. Multiple regression models were developed based on the generated data, and then the models were used in GA to determine the optimum process parameters for achieving the target DOP and HAZ width. GA-based models employed two different selection processes. Both the RSM- and GA-based models suggested a number of solutions in terms of process parameters, and the identified solutions were validated by experiments. GA-based model employing tournament selection has been found to be a more accurate method for determining the optimum A-TIG welding process parameters.     

热处理工艺对Y1Cr17Mo钢组织和性能的影响

Y1Cr17Mo钢属于铁素体-马氏体钢的范畴,其显微组织随热处理保温时间和温度的不同而发生变化,显然这也将影响到材料的力学性能。主要介绍了热处理工艺对Y1Cr17Mo钢显微组织的影响,摸索淬火温度、保温时间与显微组织、硬度之间的关系,以便为实际生产提供科学指导,从而得到所需的力学性能。     

2(1/4)Cr-1Mo钢的短裂纹低周疲劳扩展特性

对在空气中２（１／４）Ｃｒ－１Ｍｏ钢的短裂纹低周疲劳扩展特性进行研究发现，短裂纹的扩展行为与长裂纹有着相似的三个阶段，并有三个方程分别与之对应。经方程ｄａ／ｄＮ＝ｃ（ΔＪ）ｎ计算得到，临界裂纹扩展门槛值ΔＪｔｈ５６４×１０－６ＭＮ／ｍ。ＳＥＭ断口分析表明，三个阶段的短裂纹扩展特性各不相同。     

电站汽动给水泵0Cr13Ni4Mo不锈钢主轴断裂失效分析

某300 MW火电机组运行中发生汽动给水泵0Cr13Ni4Mo不锈钢主轴断裂事故。通过化学成分分析、力学性能测试、显微组织分析及断口形貌分析等方法对其断裂原因进行了分析。结果表明:给水泵主轴断裂是由于其表面镀铬处理使得镀铬层内形成众多垂直于轴基体的微裂纹,不仅降低了材料的疲劳强度,并为轴体开裂提供了众多的裂纹源,这些微裂纹在扭转循环载荷作用下向基体内部不断疲劳扩展直至断裂。     

1Cr12Ni2W1Mo1V不锈钢表面等离子堆焊司太立熔覆层的组织及性能

为提高1Cr12Ni2W1Mo1V不锈钢的耐水蚀性能,采用等离子堆焊方法在其表面制备司太立熔覆层。研究了涂层的显微组织和显微硬度分布,分析了涂层的抗微粒冲蚀性能和耐水蚀性能。结果表明:司太立熔覆层与基体材料冶金结合良好,熔覆层组织细小、分布均匀,基体为枝晶状Co-Cr固溶体,枝晶间较均匀地分布着黑色碳化物,主要为M7C3和少量WC颗粒;司太立熔覆层的平均显微硬度(382.38 HV4.9 N)约为基材平均硬度(195.29HV4.9 N)的1.96倍,最高硬度值达到了421.00 HV4.9 N;堆焊第2层的硬度明显高于第1层的;司太立熔覆层合金的抗微粒冲蚀性能优于基材,其水蚀速度比基材小,在基材1Cr12Ni2W1Mo1V上堆焊司太立合金能有效提高其耐水蚀性能。     

Effects of hydrogen on the mechanical properties of a 2 1/4Cr–1Mo steel

This paper explores the effects of hydrogen on the mechanical properties of a 2 1/4Cr–1Mo steel. The results for both microstructural conditions, as received and aged, indicated a loss of ductility after hydrogen charging treatment, but the yield strength and ultimate tensile strength remained unaltered. The fractograph analysis revealed that the fracture mode was modified by the hydrogen. The steel in the as-received condition showed craters and fisheyes on the fracture surface. The aged steel showed a brittle appearance associated with cleavage facets and small portion of areas with dimples. The hydrogen diffusivity and solubility were investigated using electrochemical permeation technique. It was observed that the hydrogen diffusivity decreased from 2.3 ± 0.4 × 10⁻¹⁰ m² s⁻¹ in the as-received condition to 5.7 ± 0.1 × 10⁻¹¹ m² s⁻¹ in the aged condition. The hydrogen solubility showed an increase for the aged condition in comparison to the as received sample. Both phenomena can be attributed to carbide evolution during aging, resulting in an increase of the carbide/matrix interfacial area.     

Isolation,identification and quantification by X-ray diffraction of carbide phases in 2 1/4Cr-1 Mo steel

The addition of controlled amounts of phosphorus to 2 1/4Cr-1 Mo steel, heat treated under two different conditions, has produced microstructures containing a wide spectrum of types and amounts of individual carbide phases. X-ray diffraction analysis of carbide precipitates has been undertaken following quantitative extraction by anodic dissolution of the matrix. By combining this with selective chemical dissolution of certain carbide types, calibrations of relative weight fractions against the intensities of suitable X-ray diffraction peaks may be obtained without the need for the addition of a standard calibration powder. This has allowed the determination of the absolute amounts, within a given steel sample, of the carbide types M₆C, M₇C₃, M₂₃C₆ and, most importantly, the creep-strengthening M₂X phase.     

热处理工艺对1Cr15Ni4Mo3N钢组织和性能的影响

通过力学性能测试和显微组织观察,研究了热处理工艺对1Cr15Ni4M03N钢显微组织和力学性能的影响。结果表明：该钢经780℃×5h空冷和590℃×4h空冷二级退火处理后具有良好的切削性能,适合进行机加工;再经过1070℃×1h油淬、-70℃冷处理和200-470℃回火处理后,可获得较好的综合力学性能。     

药芯焊丝Mo含量对低合金钢焊缝金属性能影响

通过在金红石型药芯焊丝中加入不同含量的金属Mo,研究了Mo对熔敷金属组织及力学性能的影响。研究表明,药芯焊丝中的Mo基本全部过渡到焊缝中;添加微量Mo时,焊缝金属强度显著提升,同时冲击韧性恶化严重;进一步增加Mo含量,焊缝金属强化效果不明显,而冲击性能继续下降。组织分析发现,增加焊丝中的Mo含量,首先会降低奥氏体转变温度,增加基体中的碳化物析出相;继续增加Mo时,碳化物含量减少,但M-A组元含量增加,导致韧性持续下降。     

H2+H2O还原法制备超细金属磁记录粉

采用H2＋H2O还原法,通过控制H2O／H2比可改善粉体晶粒链状结构的晶间界面结构,采用XRD、TEM、VSM等方法测试粉体的晶体结构、粒子形貌和磁性能,结果为金属磁偻的矫顽力提高;粒子形状均匀,表面平滑,毛刺少;460℃时H2＋H2O还原金属磁粉的矫顽力为1520Oe,比传统氢还原工艺矫顽力1440Oe提高5.6%。采用流化床反应器,具有温度均匀,气固接触充分,可防止颗粒烧结等优点,工业应用前景广阔。     

热处理对12Cr2Mo1R耐热钢断裂韧度的影响

本文对12Cr2Mo1R耐热钢板进行了正火+回火处理(NT),然后再进行模拟焊后热处理(SPWHT),研究了这两种状态钢板在不同温度下的J-Δa阻力曲线,并对断裂韧度J0.2BL值进行了分析。研究结果表明,这两种热处理态组织均以贝氏体为主,所含碳化物都由M3C、M2C、M7C3和M23C6组成,其中M代表合金元素Cr、Mo、Mn和Fe或者它们的组合;在相同热处理的状态下,温度越高,断裂韧度值越高;相同温度情况下,正火+回火态12Cr2Mo1R耐热钢表现出较高的断裂韧度,因为其碳化物含量较小,碳化物之间的间距相对较大。     

2(1/4)Cr-1 Mo钢的短裂纹疲劳断裂特征

本文用弹塑性断裂力学分别研究了在空气和氢中 ,压力容器器壁的承载材料 2 ( 1 / 4 )Cr— 1 Mo钢的短裂纹低频疲劳特性 ,结果表明 :都可用 da/ d N =C(ΔJ) n 的关系式计算上述两环境中的短裂纹扩展速率 .裂纹呈穿晶扩展 .氢明显增加了 2 ( 1 / 4 ) Cr— 1 Mo钢的断裂敏感性     

Determination of Neutron Irradiation-Induced Phosphorus Segregation on Grain Boundaries in a P-doped 2.25Cr1Mo Steel

Irradiation-induced impurity segregation to grain boundaries is one of the important radiation effects on materials.For this reason, phosphorus segregation to prior austenite grain boundaries in a P-doped 2.25Cr1Mo steel subjected to neutron irradiation is examined using field emission gun scanning transmission electron microscopy (FEGSTEM) with energy dispersive X-ray microanalysis (EDX). The steel samples are irradiated around 270 and 400℃, respectively.The irradiation dose rate and dose are ～1.05×10-8 dpa/s and ～0.042 dpa respectively for 270℃ irradiation, and 1.7×10-8 dpa/s and 0.13 dpa respectively for 400℃ irradiation. The FEGSTEM results indicate that there is no apparent phosphorus segregation during 270℃ irradiation but there is some during 400℃ irradiation.