X—60钢中晶内铁素体片的形成及其对焊接热影响区的作用

用晶内铁素体技术显著改善了Ｘ－６０钢熔焊热模拟后热影响区的韧性。试验发现：ＩＦＰ和冲击能密切相关，ＩＦＰ的体积分数〉７０％时，冲击能〉１５０Ｊ，光学金相和ＳＥＭ检验提示ＩＦＰ的特征，它是原奥氏体晶粒内出现的大量微细的铁素体片，是在焊后控冷过程中以“形核碚氧产物”为非自发形核核心而生成的。     

脱氧方式对焊接热影响区组织与性能的影响

通过对Al,Ti两种脱氧钢母材和焊接热影响区组织和性能的对比分析,研究了两种脱氧方式下焊接热影响区组织转变和性能特点.试验结果表明,两种钢具有相近的常规力学性能和组织结构,但在160 kJ/cm大热输入条件下,Ti脱氧钢焊接热影响区的韧性高于Al脱氧钢.在光学显微镜下,Al脱氧钢热影响区呈现上贝氏体形貌,Ti脱氧钢出现针状铁素体.通过扫描电镜观察,Ti脱氧钢热影响区的针状铁素体以夹杂物为核心形核并向四周扩展.夹杂物为含Ti氧化物及其与MnS的复合物.热影响区中可能存在多种夹杂物诱导铁素体机制.     

焊接热影响区针状铁素体的形核长大及其对组织的细化作用

通过观察焊接热循环冷却过程中不同温度取样直接淬火后的微观组织,研究了焊接热影响区(HAZ)晶内针状铁素体(IAF)的形核长大过程,论证了针状铁素体分割原奥氏体晶粒及细化晶内组织的机理.Auger电子能谱(AES)证实,在TiOx-MnS型复合夹杂物边界附近存在贫Mn区,IAF易于在这类复合夹杂物上形核,单个复合夹杂物能...     

大热量输入焊接EH40船板钢热模拟粗晶区组织与性能

采用Gleeble热模拟方法调查了钛镁钙复合处理与微钛处理两种不同成分的船板钢EH40在不同热输入条件下的粗晶热影响区的组织和冲击性能。结果表明：t_8/5时间13 ~ 550 s之间,钛镁钙复合处理的试验钢（A号）模拟粗晶区组织随t_8/5增加由粒状贝氏体逐渐转变为晶界铁素体+晶内针状铁素体+晶内多边形铁素体,同时发现大量尺寸在0.2 ~ 3 μm之间的TiO_x-MgO-Al₂O₃复合氧化物夹杂;t_8/5≤700 s时,其模拟粗晶区－20 ℃冲击吸收能量≥192 J;微钛处理的试验钢（B号）模拟粗晶区组织随t_8/5增加则由粒状贝氏体逐渐转变为晶界铁素体+上贝氏体组织,在t_8/5≤300 s时,其模拟粗晶区－20 ℃冲击吸收能量≥196 J。A号试验钢焊接性能优于B号试验钢,其原因在于A号试验钢中大量存在的复合氧化物夹杂促进了晶内铁素体形核,从而提高粗晶区的低温冲击韧性。     

冷却速度对含Ti非调质钢中晶内铁素体形成的影响

观察了不同冷速下获得的含Ti非调质钢的显微组织,并绘制了静态连续冷却转变曲线(CCT曲线).结果表明,在0.5～2.5℃/s的冷速范围内,会有晶内铁素体析出,其中在2℃/s冷却时可以获得大量针状铁素体.空冷条件下获得细小无序分布的晶内铁素体,明显提高试验用含Ti非调质钢的韧性.     

大热输入焊接高强度低合金钢热影响区的晶粒细化

研究了焊接热输入为110 kJ/cm三丝埋弧自动焊F36高强度低合金钢热影响区的晶粒细化行为;用自动图像分析仪测量了焊接热影响区诱导晶内铁素体形核夹杂物的大小、分布;用透射电镜观察了具有自细化行为晶内铁素体的形貌.结果表明,焊接热输入为110 kJ/cm三丝埋弧自动焊,焊接热输入对热影响区夹杂物的直径大小、分布几乎没有影响.E36高强度低合金钢中加入微量的Ti,能形成直径为0.2～0.8μm的MnO,TiO,SiO2,Al2O3与MnS组成的氧硫复合物.大热输入焊接时,氧硫复合物诱导热影响区的晶内铁素体形核,并促进晶内铁素体的感生形核,晶内铁素体及其感生晶内铁素体使热影响区粗晶区的晶粒细化,确保焊接热影响区粗晶区的强度与韧性不降低.     

X60钢级管线钢焊接热影响区的热模拟研究

采用焊接热模拟技术对X60钢级管线钢进行了热影响区模拟试验。研究了该钢在不同的峰值温度和冷却时间下的韧性和组织,测定了其热影响区的硬度。结果表明,峰值温度越高X60钢级管线钢的组织越粗大、韧性越低;在不同的峰值温度下,冷却时间对该钢焊接热影响区组织及韧性的影响是不同的。     

低合金高强钢大热输入焊接热影响区组织性能

利用MMS-200热力模拟试验机研究了610 MPa级低合金高强度钢不同热输入焊接热影响区粗晶区(coarse grain high affected zone,CGHAZ)的组织和性能.结果表明,随着热输入的增加,试验钢CGHAZ组织逐渐粗大,低温冲击吸收功下降,但在80～100kJ/cm的大热输入冲击下,热影响区仍...     

铁素体不锈钢焊接热影响区晶粒长大过程模拟

提出一种用Monte Carlo模拟单相合金的热影响区（HAZ）晶粒长大方法,可以将焊接实际时间与模拟过程对应起来,应用有限元方法计算出焊接热循环,并结合晶粒长大的Arrhenius公式,模拟了铁素体不锈钢EB26-1在一定规范下HAZ晶粒的演变情况,模拟结果表明,此方法可以预测HAZ中晶粒的分布以及存在于HAZ中很陡的温度梯度对晶粒长大的阻碍作用。     

EFFECT OF Zr ADDITION TO Ti-KILLED STEEL ON INCLUSION FORMATION AND MICROSTRUCTURAL EVOLUTION IN WELDING INDUCED COARSE-GRAINED HEAT AFFECTED ZONE

Effects of Zirconium on the chemical component and size distribution of Ti-bearing inclusions, favored the grain refinement of the welding reduced, coarse-grained heat affected zone （CGHAZ） with enhanced impact toughness in Ti-killed steels, which were examined based on experimental observations and thermodynamic calculations. It indicated that the chemical constituents of inclusions gradually varied from the TiO oxide to the Ti-O＋Zr-O compound oxide and a single phase of the ZrO2 oxide, as the Zr content increased from zero to 0.0100%. A trace of Zr （0.0030%-0.0080%, depending on the oxygen content in liquid steel） provided a large amount of nucleating core for Ti oxide because of the larger specific density of ZrO2 oxide, and produced a small size distribution of the inclusions favorable for acicular ferrite transformation with a high nucleation rate in the CGHAZ, and a high volume fraction of acicular ferrite was obtained in the CGHAZ, with enhanced impact toughness. Otherwise, a high content of Zr （-0.0100%） produced a single phase Zr02, which was impotent to nucleate acicular ferrite, and a microstructure composed of ferrite side plate and grain boundary ferrite developed in the CGHAZ. The experimental results were confirmed by thermodynamic calculations.     

MICROSTRUCTURE AND INCLUSION CHARACTERIZATION IN THE SIMULATED COARSE-GRAIN HEAT AFFECTED ZONE WITH LARGE HEAT INPUT OF A Ti-Zr-MICROALLOYED HSLA STEEL

1. IntroductionA pplication oflargeheatinputw elding techniques, w hich have been developed forlarge engineer-ing structure, e.g., big oiland gas tanks, bridge, pipe-line and architecture constructions etc. usuallycausesdeterioration ofm echanicalproperti…     

STRUCTURAL CHANGE IN HEAT AFFECTED ZONE AND ITS INFLUENCE ON PROPERTIES OF WELDED WHITE CAST IRON

The structural change in heat affected zone(HAZ)and its influence on properties of welded white cast iron have been investigated by means of thermal cycle simulation technique.The structure of the white cast iron at peak temperature 800℃ was examined as cementite in pearlitic matrix,of which the hardness and impact toughness are the lowest,while the struc- ture after cyclic heating at high peak temperature is mainly cementite together with twin martensite,of which the hardness and impact toughness are rather higher.The phase bounda- ries in the structure of low hardness are smooth and regular as well as with fine precipitates. Both the cleavage and interphase fracture were revealed in the structure of low hardness,while the transgranular fracture was found in those areas of higher hardness.     

MICROSTRUCTURE AND INCLUSION CHARACTERIZATION IN THE SIMULATED COARSE-GRAIN I-IEAT AFFECTED ZONE WITH LARGE HEAT INPUT OF A Ti-Zr-MICROALLOYED HSLA STEEL

The microstructure and the characteristics of the inclusions embedded in ferrite matrix in simulated coarse-grain heat affected zone (CGHAZ) of a Ti-Zr-treated high strength low alloy (HSLA) steel have been investigated. The microstructure of the simulated CGHAZ dominantly Consisted of intragranular acicular ferrite (IAF) combining with a small amount of polygonal ferrite (PF), widmanstiitten ferrite (WF), bainite ferrite (BF), pearlite and martensite-austenite (M-A) islands. The PF, WF and BF were generally observed at the prior austenite grain boundaries and the interlocking acicular ferrite was usually found intragranularly. It was found that the inclusions were composed of Ti2O3 ZrO2, Al2O3 locating at the center of the particles and MnS lying on the surface layer of the inclusions. The intragranular complex inclusions prorooted the acicular ferrite formation and the refinement of microstructure whilst those at prior austenite grain boundaries caused PF formation on the inclusions. The simulated CGHAZ consisting of such complicated microstructure exhibited desired mechanical properties.     

白口铸铁焊接热影响区组织转变及其对性能的影响SCIEI

采用热模拟技术再现白口铸铁焊接热影响区的组织,研究了焊接热影响区的组织转变及其对性能的影响,发现热循环峰温为800℃时,白口铸铁的组织为渗碳体加珠光体,其硬度最低,冲击韧性最差;高峰温热循环作用后的组织主要为渗碳体加孪晶马氏体,其硬度较高,冲击韧性较好;低硬度组织的相界面平滑、圆整,并且界面上有细小化合物析出,其断裂为解理加沿相界断裂,高硬度组织的断裂为穿晶断裂。     

Ti脱氧钢含Ti复合夹杂物诱导晶内针状铁素体的原位观察

采用高温共聚焦激光显微镜(CSLM)对含Ti复合夹杂物诱导晶内针状铁素体(IAF)进行动态原位观察,并用OM,FE-SEM,EDS和EPMA研究奥氏体晶粒尺寸和冷却速率对含Ti复合夹杂物诱导生成IAF的影响.结果表明,IAF的开始生成温度随奥氏体晶粒尺寸的增加,先升高后降低;生成IAF体积分数随冷却速率的提高显著增加,...     

低碳贝氏体钢焊接热影响区中不同亚区的组织特征与韧性

根据焊接热影响区中不同亚区的热循环特征对低碳贝氏体钢进行了焊接热模拟实验.采用示波器载荷冲击试验机检测焊接热模拟试样的冲击韧性,结合OM,SEM,TEM以及EBSD技术对模拟显微组织的观察,分析了不同亚区的显微组织特征与冲击韧性之间的关系.结果表明,当冷却时间t_(8/5)=30 s时,各亚区的裂纹形核功相差并不太大,其值在40—70J之间.细晶区(FGHAZ)具有良好的止裂能力,裂纹扩展功高达122 J;而部分相变区(ICHAZ)和粗晶区(CGHAZ)的裂纹扩展功较小,分别为51.8和17 J.随t_(8/5)的延长,各亚区的裂纹形核功和扩展功均下降,其中CGHAZ的裂纹形核功和FGHAZ的裂纹扩展功的下降最为显著.不同冷却速率下,M-A组元尺寸和形态的变化是影响裂纹形核功的重要因素.对于裂纹扩展功来说,高冷却速率下,具有高密度大角晶界的FGHAZ具有良好的抗裂纹迅速扩展的能力,但当冷却速率降低,由于原始奥氏体晶粒长大而使裂纹扩展功下降.ICHAZ有效晶粒尺寸不均匀,并随冷却速率的降低,晶粒尺寸明显增大,裂纹扩展功下降.而在CGHAZ中原始奥氏体晶粒显著粗化,大角晶界密度的下降导致裂纹扩展功降低;随冷却速率...     

1ONi8CrMoV钢热影响区粗晶区组织和性能研究

采用焊接热模拟技术研究了焊接热循环对IONi8CrMoV钢热影响区粗晶区（L为1300℃）组织和性能的影响。结果表明，经历不同冷却速度（t8/5为7-112s）的热循环后，1ONi8CrMoV钢粗晶区低温冲击吸收功较基体冲击吸收功有较大幅度的提高，且随着冷却速度的增加，冲击吸收功降低幅度很小；在不同的冷却速度下，粗晶区组织均为粗大的板条马氏体组织，晶粒尺寸较大，板条马氏体界面上奥氏体薄膜的存在是粗晶区韧性提高的原因。     

STUDY OF THE MICROSTRUCTURE AND PROPERTIES OF SIMULATED HEAT AFFECTED ZONE IN LASER WELDING OF ULCB 600 STEEL

1.IntroductionbeerbeamweldingilasbeenwidelyusedasanimportantprocessinsheetsteelstrUcture.WiththedevelOPmentofhighpowerlaseranditsincreasingsuccessfalaPPlicationsinindustry,itisbecomingObViousthatthatlaserweldingwillalsohaveanimportantimpactonthemediumandheaVysectionindusalintheneaxfutUre.Theleadingindustryforinboducinghighpowerlaserweldingistheshipbuilding['j.ULCBanisalatelydevelopedsteelinWuhanSteelwithultra--lowcarboncontentanddondnativendcrostructureOfbainite,whichwillbewidelyusedinsh…