A5O8-3钢热处理后的显微组织

利用光镜和电镜研究了热处理后 A508-3钢的各种显微组织。结果表明:在中等冷却速度(70—480℃/min)下组织为粒状贝氏体,经长时间高温回火后,不仅小岛发生分解,基体上还均匀析出合金碳化物 Mo_2C,这对钢的强韧性产生不利影响,为此,加入少量的铌是有利的。     

Isaichev取向关系的矩阵分析

借助电镜观察了粒状贝氏体小岛回火析出的渗碳体与铁素体之间的取向关系,利用取向关系转换矩阵特征值和特征向量的计算,对 Isaichev 关 系 作 了 分 析 。 结 果 表 明 Isaichev 关 系 确 实 是Kurdjumov-Sachs(K-S)关系与Pitsch关系的复合,从而确认了这一取向关系下渗碳体析自奥氏体而不是铁素体的观点。同时矩阵计算也说明了珠光体转变中奥氏体、铁素体和渗碳体之间所报道的取向关系是不能同时成立的。     

P11耐热钢窄间隙焊接接头组织分布特征与性能分析

针对P11耐热钢采用钨极氩弧自动焊进行多层单道窄间隙焊接,对接头进行金相试验和力学性能测试,重点探讨并总结了窄间隙钨极氩弧多层单道焊接接头组织的分布特征及与硬度的对应关系。测试结果表明：接头中的填充焊道组织为铁素体和屈氏体,粗、细晶区呈交互层叠状分布,组织较母材细小,硬度高于母材;盖面焊道组织以回火马氏体和粒状贝氏体为主,组织粗大且出现了网状屈氏体,硬度较填充焊道组织高;焊接热影响区中铁素体+珠光体组织呈条带状分布,与焊缝内组织相近。接头拉伸试验结果表明接头各区域抗拉强度较为均匀,与组织分析结果相吻合。冲击试验结果表明接头各区域冲击吸收能量均满足设计要求。     

焊后热处理对16MND5钢焊接组织结构与残余应力的影响

16MND5钢广泛应用于核岛承压容器构件,其焊接接头不可避免地会引入高的残余应力,而焊后热处理可有效消减焊接残余应力以克服应力腐蚀裂纹的影响。本工作利用轮廓法和中子衍射技术研究了焊后热处理对16MND5钢焊接残余应力的影响。结果表明,轮廓法与中子衍射测试结果在趋势和数值上取得了较好的一致性,焊后热处理使焊接态的残余应力峰值从约420 MPa降低至约210 MPa。同时,利用金相法和SEM研究了焊后热处理对焊缝区域组织结构的影响。结果表明,焊后热处理主要表现为贝氏体和少量自回火马氏体的焊缝中心组织转变为回火贝氏体和回火马氏体,热处理后的焊缝区晶粒明显长大。     

V对低合金MnSiCr空冷贝氏体/马氏体复相钢强韧性的影响

反应堆安全壳结构起着包容放射性物质和保护反应堆系统免受外界干扰的作用,是关系到核电站安全运行的重要结构。核反应堆筒体预应力钢筋混凝土结构用精轧螺纹钢筋的强韧性直接影响安全壳的寿命。为了开发新一代超高强钢筋,在新型空冷Mn系贝氏体钢的基础上进行V微合金化,并采用空冷回火工艺,实验钢筋的屈服强度达到1494MPa,抗拉强度1688MPa。利用SEM、TEM等方法研究V微合金化对实验钢强韧性、组织、相变的影响,对（Ti,V）C析出物形貌、分布及大小进行了观察和研究。     

低活化钢中MX相析出行为研究

研究了不同合金成分的低活化钢中MX（M＝Ta,X＝C、N）相在750℃下保温不同时间的转变行为,低活化钢中Ta的稳定析出相为TaC。经1050℃固溶处理后,平均尺寸约150nm的未溶TaC颗粒钉扎原奥氏体晶界和板条束界,阻碍晶界和板条束界的迁移。经750℃回火后,在晶界和晶内析出尺寸为15～45nm细小弥散的TaC相。低活化马氏体钢回火过程中回溶的Ta原子在随后的析出过程中在新位置形核,而不是在原TaC颗粒上形核长大,导致低活化马氏体钢中TaC有较小的长大速率。在回火初期,TaC在基体中共格析出,在长时间回火过程中,TaC以特定的原子面(200)_TaC、(111)_TaC析出、长大。     

控制棒驱动机构滚轮用马氏体不锈钢的显微组织研究

利用金相显微镜、扫描电镜、透射电镜和X射线衍射仪研究了9Cr18和9cr18Mo不同热处理状态的显微组织及冲击和拉伸断口.结合力学性能实验结果,分析了材料微观组织对力学性能的影响.结果表明:材料中大量脆性块状共晶碳化物呈带状分布是材料力学性能出现显著各向异性的原因;9Cr18Mo在350-550℃回火时出现的回火脆性,由杂质元素的偏聚引起.两种材料中都没有观察到明显的残余奥氏体相,回火过程中从基体析出的Cr含量不超过1%.     

17-4PH不锈钢350℃长期时效组织演化的透射电镜观察

采用X-ray衍射（XRD）和透射电镜（TEM）研究了17—4PH马氏体沉淀硬化不锈钢在350℃长期时效过程中显微组织的变化规律。结果表明：在沉淀硬化回火处理后,在典型的板条马氏体基体中弥散分布着大量的纳米级的ε-Cu颗粒,二次碳化物M23C6沿马氏体板条束界析出。17-4PH马氏体不锈钢在350℃时效6个月后,组织发生一定变化,spinodal分解开始在晶界发生,另外析出的ε-Cu颗粒逐渐长大,并且有少量的逆转变奥氏体产生：17-4PH不锈钢在350℃时效15个月后,spinodal分解逐渐由晶界发生转向晶内,基体中析出大量有取向的细小的G相,并观测到少量sigma相。基体仍为板条马氏体。     

17-4PH不锈钢回火强化过程研究

将17-4PH钢在1 040℃保温1 h后水淬,于540℃回火不同时间,测试其硬度以研究其析出强化规律,利用原子探针层析技术(APT)研究了强化相析出演化过程。析出强化曲线显示,存在两个析出强化峰。APT分析表明,第1个强化峰是由于析出了大量纳米级富Cu相,第2个强化峰则是由于析出了Cr、V、Nb碳氮化物。APT分析还显示,在富Cu相的周围,Mn、Ni和Al也出现偏聚,而且位于富Cu相和基体的界面。     

核电机组二回路主蒸汽隔离阀螺栓“咬死”原因分析

某核电厂新建机组第一次大修期间,对主蒸汽隔离阀进行解体检修,发现多个阀盖螺栓与螺母发生了"咬死"现象,拆卸过程中个别螺栓甚至被拧断,对失效的螺栓、螺母进行了理化检验。成分分析表明,螺栓、螺母材料符合标准要求;硬度试验表明,螺母硬度值比螺栓高47 HB;金相分析表明,螺母组织为回火马氏体+回火索氏体,螺栓组织为回火索氏体。螺栓、螺母硬度值的不合理匹配,是二者发生"咬死"现象及拆卸过程中个别螺栓被拧断的根本原因。     

The effect of carbon on 2.25 Cr-1 Mo steel: (I). Microstructure and tensile properties

The microstucture, hardness, and the tensile properties of 2.25 Cr-1 Mo steel with 0.009, 0.030, 0.120, and 0.135 wt % C were determined on steels in the annealed (furnace-cooled from 927°C), normalized (air-cooled from 927°C), and normalized-and-tempered conditions. As annealed, the microstructure was primarily proeutectoid ferrite with spherical carbides and pearlite, the amounts increasing with increasing carbon content. During normalization ($\text{7}\text{8}$ in rods or 1 in plates were heat-treated), granular bainite formed: 1 to 2 and 15 to 20% bainite (remainder proeutectoid ferrite) for the 0.009 and 0.030 wt % C steels, respectively; the 0.120 and 0.135 wt % C steels were entirely bainite. On tempering, carbides precipitated. In all heat-treated conditions, there was little difference in the room temperature hardness of the 0.009 and 0.030 wt % C steels and between the 0.120 and 0.135 wt % C steels. Tensile tests from 25 to 565°C indicated that strength depends on microstructure, which is determined by carbon content.     

A5O8-3钢晶粒组织的细化

对 A508-3钢的原奥氏体晶粒、贝氏体束区及临界区淬火后平均晶粒的大小作了测定,并讨论了其影响因素。结果表明,低含铝量是原奥氏体晶粒出现严重混晶的原因,提高冷却速度可使贝氏体束区的尺寸变小,采用临界区淬火后晶粒组织得到大幅度的细化。     

CLAM钢TIG焊后的热处理工艺研究

为了解决利用钨极氩弧(TIG)焊方法焊接的CLAM钢在焊缝区存在的强度、硬度增加而韧性减弱的问题,从回火温度、回火时间以及重复回火等方面研究了回火对焊缝区硬度的影响,得到了回火温度选择为760℃、回火时间选择为2 h和在760℃保温1 h回火,重复进行两次的两种最佳热处理工艺.     

氧化物弥散强化低活化合金的微观组织及力学性能

为了强化低活化合金(CLF-1)的高温性能,将采用Ar气超声雾化方法制备的CLF-1粉末与纳米Y₂O₃粉末混合后,经高能球磨和热等静压处理,获得氧化物弥散强化（ODS）CLF-1样品。对样品进行不同制度的热处理,并进行了微观组织分析和力学性能测试。分析结果表明,经过正火和回火处理,ODS CLF-1组织为回火马氏体,当正火温度为1 100 ℃时晶粒尺寸最为均匀。回火温度对显微组织影响不明显,但回火温度升高,维氏硬度下降。热处理后样品中观察到明显的弥散分布的Y₂O₃颗粒和位错塞积,证实了弥散强化的作用。Y₂O₃颗粒尺寸不均匀,100 nm左右的大颗粒倾向于沿晶界分布,而较小的颗粒则在晶内分布。ODS CLF-1样品具有良好的高温拉伸性能,600 ℃时抗拉强度为370 MPa,延伸率为18.5%。屈服强度和抗拉强度随热处理温度的升高而降低。     

High-temperature mechanical properties improvement on modified 9Cr-1Mo martensitic steel through thermomechanical treatments

In the framework of the development of generation IV nuclear reactors and fusion nuclear reactors, materials with an improved high temperature (≅650 °C) mechanical strength are required for specific components. The 9-12%Cr martensitic steels are candidate for these applications. Thermomechanical treatments including normalisation at elevated temperature (1150 °C), followed by warm-rolling in metastable austenitic phase and tempering, have been applied on the commercial Grade 91 martensitic steel in order to refine its microstructure and to improve its precipitation state. The temperature of the warm-rolling was set at 600 °C, and those of the tempering heat-treatment at 650 °C and 700 °C thanks to MatCalc software calculations. Microstructural observations proved that the warm-rolling and the following tempering heat-treatment lead to a finer martensitic microstructure pinned with numerous small carbide and nitride particles. The hardness values of thermomechanically treated Grade 91 steel are higher than those of the as-received Grade 91. It is also shown that the yield stress and the ductility of the thermomechanically treated Grade 91 steel are significantly improved compared to the as-received material. Preliminary creep results showed that these thermomechanical treatments improve the creep lifetime by at least a factor 14.     

Studies on hydrogen permeability of 2.25% Cr–1% Mo ferritic steel: correlation with microstructure

The influence of microstructure on the hydrogen permeability, diffusivity and solubility in 2.25% Cr–1% Mo ferritic steel was investigated using electrochemical permeation technique. Varieties of microstructures ranging from martensite in water-quenched (WQ) steel to a predominant ferrite structure in annealed steel were characterised using analytical transmission electron microscopy. In the tempered structures, continuous precipitation of a variety of carbides of different morphologies and sizes was also characterised. The hydrogen diffusivity showed a continuous increase as the structure changed from martensite to ferrite and also with increasing extent of tempering. Solubility showed a corresponding decrease. The trends have been understood in terms of the number of reversible traps available for hydrogen in these different structures. Accordingly, martensite structure offered the maximum resistance to hydrogen diffusivity and tempered structure the least resistance due to the annihilation of defects during tempering and reduction in the solute content of the matrix due to precipitation.     

Influence of tempering temperature upon precipitate phases in a 11%Cr ferritic/martensitic steel

The effect of tempering temperature on the precipitate phases in a 11%Cr ferritic/martensitic steel normalized at 1050 °C for 1 h and tempered for 2 h at temperatures ranging from 600 to 780 °C has been investigated using transmission electron microscope and energy-dispersive X-ray spectroscopy. The results show that tempering temperature does not affect the existences of niobium-rich carbonitrides, (Nb_0.7V_0.2Cr_0.1)(C,N) and (Nb_0.55V_0.35Cr_0.1)(C,N), vanadium-niobium-rich carbonitride (V_0.45Nb_0.45Cr_0.1)(C,N), chromium-rich carbonitride (Cr_0.83V_0.12W_0.05)₂(C,N) and chromium-rich carbide (Cr_0.7Fe_0.25W_0.05)₂₃-C₆, whilst the precipitations of vanadium-rich carbonitrides, (V_0.65Nb_0.2Cr_0.15)(C,N) and (V_0.55Nb_0.25Cr_0.2)(C,N) are dependent on tempering temperature, which were detected only at the higher tempering temperatures of 750 and 780 °C. No coarsening was occurred during the temperings for the niobium-rich and spherical vanadium-rich carbonitrides. There was a low coarsening rate for the chromium-rich carbonitrides and chromium-rich carbides with increasing the tempering temperature from 600 to 700 °C and 650 to 780 °C, respectively, and a high coarsening rate for the chromium-rich carbonitrides and chromium-rich carbides at the tempering temperatures 750 through 780 °C and 650 °C, respectively. The compositions show an increase in vanadium and a decrease in niobium and chromium contents for the niobium-rich carbonitrides, and a decrease in niobium and an increase in vanadium and chromium contents for the vanadium-niobium-rich carbonitrides, and an increase in vanadium and a decrease in tungsten contents for the chromium-rich carbonitrides. The chromium-rich carbides show an increase and a decrease in their iron and chromium contents, respectively, with increasing the tempering temperature from 650 to 780 °C.     

A508—3钢热处理研究

本文介绍国产 A508-3钢在不同的淬火、回火和退火条件下的热处理实验的某些结果。