超声冲击处理焊接接头焊趾区材料的疲劳性能

利用自行研制的超声波冲击实验装置,对两种典型焊接结构用钢Q235B和16Mn焊接接头实施冲击处理,然后进行焊态与冲击处理态的弯曲与拉伸两种加载方式的疲劳对比试验,分别获得了各种情况冲击处理前后的Δσ-N曲线及疲劳强度(2×10     

氢离子辐照对CLAM钢微观结构的影响

利用氢离子辐照的方法研究了CLAM钢的辐照缺陷形成行为.实验发现,在基本成分的CLAM钢及添加Si的CLAM钢中都产生了辐照析出现象.耐腐蚀合金元素Cr是产生辐照析出的合金元素之一,合金元素Si对于提高CLAM钢的抗辐照析出性能具有显著作用.     

450℃高能电子辐照对CLAM钢微观结构的影响

为了研究低活化马氏体CLAM钢的抗辐照肿胀性能,在450℃下对CLAM钢进行大剂量高能电子辐照的原位动态实验.利用超高压透射电子显微镜观察发现,CLAM钢中产生了大量的间隙原子型位错环和多面体形状的辐照空洞.分析了它们的形核和长大规律以及相关机制.计算表明,CLAM钢在高能电子辐照下的最大肿胀率为0·26%,具有较好的抗辐照肿胀性能.     

35#钢摩擦焊多级加压对轴向缩短量及焊后组织的影响

以35#钢为焊接母材,应用连续驱动摩擦焊接方式,采用正交试验的方法并经过极差分析后,探究了中等直径焊件多级加压方式下各工艺参数对轴向缩短量的影响规律,并对焊接接头显微组织及显微硬度进行了分析.实验结果表明,对焊件轴向缩短量影响程度依次为:二级摩擦位移、二级摩擦压力、一级摩擦压力、一级摩擦位移;观察焊接接头显微组织发现焊缝处得到了细小的铁素体与珠光体相互融合的优良组织,焊缝组织达到正火态;通过对焊件焊缝及热影响区显微硬度测试后可以得出,各焊件焊缝的显微硬度值明显高于母材,不同焊接工艺参数组合方式对焊件接头晶粒存在一定影响并直接影响焊件接头硬度.     

热处理对CLAM钢TIG焊接接头显微组织影响

采用TIG焊接方法对中国低活化马氏体钢(CLAM 钢)进行了平板对接试验,分别对焊接接头采用不同温度的焊后热处理,试验温度分别为610,660,710,760,810℃,保温30 min.结果表明,焊后进行热处理与不做热处理两种情况下,CLAM钢焊接接头微观形貌和硬度存在很大不同;随温度增加,焊接接头焊缝中马氏体板条分布及尺寸均匀性得到提高,热处理温度710℃以上时板条均匀性最好,但晶粒尺寸与板条也会随温度升高而长大.焊后热处理使焊接接头各部分硬度随热处理温度的升高而逐渐降低,焊缝金属硬度下降值比母材和焊缝热影响区大得多,尤其在810℃时焊缝金属硬度下降值最大,降至与母材硬度相当.     

大端面铝与钢的摩擦焊焊缝组织及性能

以铝和钢为焊接材料,采用连续驱动摩擦焊技术对大截面铝与钢异种金属进行焊接试验.通过显微组织、电子探针、X射线衍射、力学性能分析及微区硬度测试检测焊接性能.结果表明:大截面铝与钢之间具有良好的摩擦焊接性,焊接接头强度等于或高于铝基材;焊接接头在近缝区发生晶粒细化,在粘塑层发生原子扩散,形成扩散层.     

喷焊层对焊缝组织性能的影响规律

为解决油田管线焊接接头防护问题，利用金相显微镜对焊缝组织形貌进行了观察。得到了镍基喷焊层元素熔入量对奥氏体焊缝显微组织及裂纹敏感性的影响规律。结果表明，镍基合金喷焊层的合金元素对奥氏体焊缝显微组织有明显影响，随着喷焊层元素熔入量的增加，焊缝柱状晶变得粗大，且方向性变得更明显。在一定范围内，增加喷焊层元素熔入量，焊缝的热裂纹敏感性将增大，但当熔入量再继续增加时，由于过量的喷焊层形成的大量低熔共晶物对焊缝冷却过程中的微裂纹起到了“愈合作用”，使焊缝裂纹敏感性有所降低。同时，熔入过量喷焊层元素使得焊缝的薄弱位置发生了变化，热裂纹产生的位置由等轴晶区转移到柱状晶区。为了降低焊缝的热裂纹敏感性，应该在保证喷焊层耐蚀性的前提下，尽量降低喷焊层的厚度。     

冲击荷载作用下钢-混凝土组合梁的动力性能研究

通过对6根简支钢-混凝土组合梁缩尺模型进行冲击试验,得到了相应的应变和挠度时程曲线.用大型通用有限元计算软件ANSYS/LS-DYNA进行参数比较分析,得出了钢-混凝土组合梁在冲击荷载作用下的更多的力学行为,如变形曲线、位移曲线、应变、速度、加速度时程曲线.分析表明,组合梁跨中附近钢筋混凝土上面层的横向变形最明显;加速度值从钢筋混凝土上面层到下面层逐渐减小.     

微观结构尺寸对钢疲劳性能的影响

研究了超高强度钢 30 Cr Mn Si Ni2 A的微观结构尺寸对其疲劳性能的影响 .试验结果表明 :在淬火 低温回火状态下 ,这种钢的旋转弯曲疲劳极限σ- 1随其微观结构尺寸(原奥氏体晶粒或马氏体束径尺寸 )的减小而提高 ,且有关系式σ- 1=σ0 kd- 1/ 2 .这样 ,就可以通过测量钢的微观结构尺寸来估算其疲劳性能     

混合气体保护焊对焊缝金属组织与性能的影响

通过改变Ａｒ／ＣＯ２混合气体配比，对Ａ３，１６ｍｎ钢焊缝金属组织与性能的影响进行了研究。并得出相应的一些规律。     

钇基稀土对E36钢板显微组织及冲击性能的影响

运用扫描电镜及能谱等分析手段研究了钇基稀土对E36钢中夹杂物的变质作用以及对显微组织和冲击性能的影响.研究表明,钇基稀土改善了E36钢的显微组织,减少了珠光体的片间距和含量.加入钇基稀土后,E36钢的冲击断口由典型的解理断口变为准解理+韧窝型断口,韧窝中细小球状的稀土夹杂是其转变的主要原因.加入少量的钇基稀土显著改善了E36钢的冲击韧性,尤其是低温冲击性能.在-60℃情况下,E36Re钢的纵向冲击功较E36钢提高了33.5%,横向冲击功提高了113.7%.并且,钇基稀土显著改善了E36钢纵横向冲击性能的差异性,未加稀土E36钢的纵、横冲击比均大于1.70,-60℃条件下达到2.77,而E36Re钢的纵、横冲击比为1.51~1.73.     

Effect of microstructure on the impact toughness of a bainitic steel bloom for large plastic molds

The correlation between the impact toughness and microstructural characteristics of a large bainitic steel bloom has been investigated. The study focuses on microcrack nucleation and propagation in the basic cleavage plane. To analyze the phase transformation during the wind-cooling process, the temperature field of the bloom was acquired by computer simulation, and a continuous cooling transformation experiment was conducted. The results show that compared with the surface of the bloom, the toughness of the bloom’s core is decreased by the increase in proeutectoid ferrite and the coarsening of tempered martensite–austenite constituents. The proeutectoid ferrite decreases the toughness via its effects on carbide precipitation, the formation of martensite–austenite constituents, and the bainite transformation. The relatively large tempered martensite–austenite constituents are conducive to microcrack nucleation and propagation.     

冲量及层理对煤块冲击韧度的影响

为了研究不同冲击速度条件下块煤冲击韧度的变化特征,以及块煤节理方向性对块煤冲击韧度的变化特性。采用传统的冲击试验机对北京大安山煤矿的块煤进行了不同冲击速度、不同的冲击方向条件下的有缺口冲击试验。试验结果表明,当冲量小于25N.s时,沿着垂直层理方向和平行层理方向施加冲量后,试样的变化形态十分接近,而在此之后两者的差异随冲量的增加而增大。同时发现裂纹在试样中扩展所需能量随速度的增加而增加,裂纹扩展速度的所需能量与冲击方向密切相关,并且这种由不同结构产生的冲击韧度的差异随冲击速度的增加而加大。对于沿着垂直节理方向施加冲量的块煤产生的断裂面平整,破碎的块数较少;而对于沿着平行节理方向施加冲量的块煤,断裂面也就不平整,破碎的程度严重,碎块数较多。这反映了冲击韧度对煤块的某些缺陷很敏感。     

X100管线钢焊接热影响区组织与韧性研究

采用热模拟试验技术,研究了X100管线钢焊接热影响区的组织与性能变化规律,结果表明:采用高Nb、微Ti设计的低碳X100管线钢的焊接粗晶区经焊接热循环后仍保持良好的韧性。焊接热影响区的脆化区出现在峰值温度为750℃的两相区。沿原奥氏体晶界形成的岛状组织是导致韧性降低的主要原因。     

热输入对深海X70粗晶区组织和韧性的影响

为解决深海X70管线钢在实际焊接中粗晶区(CGHAZ)的脆化问题,在不同热循环工艺下对X70管线钢进行了热模拟研究。采用Gleeble-3800热模拟机模拟X70管线钢CGHAZ,研究CGHAZ在10～60 kJ/cm不同热输入(HI)条件下组织和韧性的变化规律,并通过光学显微镜(OM)、扫描电镜(SEM)和夏比冲击试验等手段表征CGHAZ的组织和韧性。结果表明,不同热输入下试验钢的组织主要由粒状贝氏体(GB)、贝氏体铁素体(BF)和马-奥组元(M-A组元)组成;当HI不断增大时,BF比例减少,GB比例增加,M-A组元粗化,冲击吸收能先升高再降低;当HI为20 kJ/cm时,BF和GB可获得优异组合,断口为韧性断裂,冲击吸收能达到173.8 J;当HI大于20 kJ/cm时,断口解离断裂,冲击吸收能下降明显,最低为18.8 J。因此,较低的热输入可提高CGHAZ的韧性,使X70管线钢具有高强度、高韧性和良好的焊接性。研究结果可为优化焊接工艺提供理论依据。     

Effect of microstructure on the low temperature toughness of high strength pipeline steels

Microstructure observations and drop-weight tear test were performed to study the microstructures and mechanical properties of two kinds of industrial X70 and two kinds of industrial X80 grade pipeline steels. The effective grain size and the fraction of high angle grain boundaries in the pipeline steels were investigated by electron backscatter diffraction analysis. It is found that the low temperature toughness of the pipeline steels depends not only on the effective grain size, but also on other microstructural factors such as martensite-austenite (MA) constituents and precipitates. The morphology and size of MA constituents significantly affect the mechanical properties of the pipeline steels. Nubby MA constituents with large size have significant negative effects on the toughness, while smaller granular MA constituents have less harmful effects. Similarly, larger Ti-rich nitrides with sharp corners have a strongly negative effect on the toughness, while fine, spherical Nb-rich carbides have a less deleterious effect. The low temperature toughness of the steels is independent of the fraction of high angle grain boundaries.     

铌和氧化铈对堆焊金属耐磨性及冲击韧性影响

在自保护药芯焊丝中添加不同量的Nb和氧化铈,分析Nb和氧化铈对堆焊层组织和性能的影响．测试了堆焊层的硬度和冲击韧性,使用自制干砂一橡胶轮装置进行堆焊层试样的磨粒磨损测试．使用光学显微镜、扫描电镜和x射线衍射分析堆焊层的组织,并使用扫描电镜分析了堆焊层磨损后的表面形貌．结果表明：Nb和稀土氧化铈都可以细化堆焊金属,从而使得堆焊金属的硬度提高;Nb的添加对提高堆焊金属的冲击韧性有一定的影响,但是效果不如稀土氧化铈明显;堆焊层的磨损形式主要为显微切削和“犁”作用2种形式,添加Nb和稀土氧化铈后,堆焊层的耐磨性有明显提高．     

Determining role of heterogeneous microstructure in lowering yield ratio and enhancing impact toughness in high-strength low-alloy steel

Here we present a novel approach of intercritical heat treatment for microstructure tailoring, in which intercritical annealing is introduced between conventional quenching and tempering. This induced a heterogeneous microstructure consisting of soft intercritical ferrite and hard tempered martensite, resulting in a low yield ratio(YR) and high impact toughness in a high-strength low-alloy steel. The initial yielding and subsequent work hardening behavior of the steel during tensile deformation were modified by the presence of soft intercritical ferrite after intercritical annealing, in comparison to the steel with full martensitic microstructure. The increase in YR was related to the reduction in hardness difference between the soft and hard phases due to the precipitation of nano-carbides and the recovery of dislocations during tempering.The excellent low-temperature toughness was ascribed not only to the decrease in probability of microcrack initiation for the reduction of hardness difference between two phases, but also to the increase in resistance of microcrack propagation caused by the high density of high angle grain boundaries.     

Determining role of heterogeneous microstructure in lowering yield ratio and enhancing impact toughness in high-strength low-alloy steel

Here we present a novel approach of intercritical heat treatment for microstructure tailoring,in which intercritical annealing is introduced between conventional quenching and tempering.This induced a heterogeneous microstructure consisting of soft intercritical ferrite and hard tempered martensite,resulting in a low yield ratio(YR)and high impact toughness in a high-strength low-alloy steel.The initial yielding and subsequent work hardening behavior of the steel during tensile deformation were modified by the presence of soft intercritical ferrite after intercritical annealing,in comparison to the steel with full martensitic microstructure.The increase in YR was related to the reduction in hardness difference between the soft and hard phases due to the precipitation of nano-carbides and the recovery of dislocations during tempering.The excellent low-temperature toughness was ascribed not only to the decrease in probability of microcrack initiation for the reduction of hardness difference between two phases,but also to the increase in resistance of microcrack propagation caused by the high density of high angle grain boundaries.     

焊接热循环对P460NL1高强正火容器钢微观组织及低温冲击韧性的影响

采用焊接热模拟技术,结合OM、SEM、TEM及-40℃低温冲击韧性实验,研究了焊接热循环(不同峰值温度和t_(8/5)参数)对P460NL1高强正火容器钢热影响区组织和低温韧性的影响,重点分析了不同焊接热循环中强化相V(C,N)粒子的演变。结果显示,当t_(8/5)同为45 s时,P460NL1钢模拟热影响区的低温冲击韧性随峰值温度的升高大致呈降低趋势,且温度超过1200℃后冲击韧性急剧降低。峰值温度为1350、1200℃且t_(8/5)在15～100 s范围时,模拟的是P460NL1钢焊接热影响区粗晶区,组织主要为铁素体和贝氏体混合组织,此条件下P460NL1钢的低温冲击韧性较低且基本不随t_(8/5)的变化而变化;t_(8/5)为45 s时,峰值温度1100、950℃对应的是焊接热影响区细晶区,此时组织为铁素体+贝氏体+珠光体混合组织,峰值温度870℃模拟的是两相区,主要为铁素体和珠光体组织。利用Thermal-Calc软件计算得到P460NL1钢中V(C,N)溶解温度为1160℃,故当峰值温度超过1200℃时,V(C,N)粒子完全溶解且未再析出,基体中存在的游离N会降低P460NL1钢的低温冲击韧性,且当峰值温度为1350℃时,随着t_(8/5)增加,晶粒尺寸逐渐增大,但冲击韧性却没有因此而降低,表明游离氮是热影响区粗晶区冲击韧性的关键因素。