1 200 MPa级HSLA钢的SH-CCT曲线及其热影响区组织与性能

为在工程应用中对焊接工艺的合理选取与制定提供理论和试验依据,采用焊接热模拟技术研究了800~500℃冷却时间(t8/5)对1 200 MPa级低合金高强钢焊接热影响区粗晶区(CGHAZ)显微组织和性能的影响.结果表明:t8/5为6~20 s时,该钢热影响区的粗晶区组织为板条马氏体,硬度为477~456 HV5;随着冷却时间的延长,组织中开始出现板条贝氏体,在t8/5为60 s时硬度下降到380 HV5;当t8/5为60~600 s时,粗晶区组织为板条贝氏体和粒状贝氏体,硬度为380~300 HV5;t8/5600 s时粗晶区组织主要为粒状贝氏体,硬度为300~315 HV5.试验钢碳当量为0.626%,冷裂纹敏感系数为0.335%,说明其淬硬倾向较大,焊接热影响区容易产生裂纹.     

焊接热输入对06CuNiCrMoNb钢HAZ组织与性能的影响

研究了热输入对06CuNiCrMoNb钢焊接热影响区不同部位组织和性能的影响,重点分析了粗晶区的韧性与组织之间的关系。结果表明,模拟焊接热影响区没有出现"软化"现象,但是当线能量大于30kJ/cm情况下,粗晶区低温韧性迅速下降。对粗晶区的分析显示,线能量17kJ/cm条件下贝氏体铁素体呈细小板条状,在板条间存在着残余奥氏体薄膜,随线能量的增大,块状的铁素体数量增多,并且出现不规则片状M+A组元。     

C、Al、Ti对钢焊接热影响区韧性的影响

微量Ａｌ、Ｔｉ对７９０ＭＰａ级钢焊接ＨＡＺ的韧性有重大的影响，加入Ａｌ后，在５ＫＪ／ｍｍ的焊接线能量下，热模拟试样的ＡＫＶ（－２０℃）与ＡＫＶ（－４０℃）分别为１０４Ｊ与２０Ｊ与不加Ａｌ的钢相比，分别提高了４．９倍和１．６倍．Ａｌ与Ｔｉ同时加入则ＡＫＶ（－２０℃）与ＡＫＶ（－４Ｏ℃）分别为１５１Ｊ和３８Ｊ．如果把母材中的含Ｃ量降低到０．０４％，ＨＡＺ的低温韧性得到更大的改善．本文也探讨了ＡＩＮ、ＴｉＮ在焊接热循环过程中的溶解与析出行为．     

细晶钢焊接热影响区晶粒长大及组织转变

分析了细晶钢的晶粒长大现象及其影响因素，讨论了ＨＡＺ的组织转变及其影响因素，提出了防止上贝氏体Ｂｕ和Ｍ－Ａ组元形成的有效控制措施。     

T91钢焊缝及热影响区显微组织图象分析

T91钢具有良好的高温抗氧化性和抗腐蚀性,该钢含8％－9．5％Cr,合金含量复杂,焊接难度大,运用金相显微镜和扫描电镜（SEM）分析了不同爆接工艺条件下T91耐热钢焊缝及热影响区或区域显微组织特征,利用XQF－2000型显微图象分析仪对显微组织中各相的相对含量和奥氏体晶粒度进行了测量,分析了焊接线能量对T91钢焊接接头区组织性能的影响,结果表明,采用多道焊焊接工艺,严格控制焊接线能量在16kJ/cm左右,可以防止T91钢焊缝区奥氏体晶粒粗大,避免在热影响区出现声状铁素体组织,从而保证焊接接头区具有良好的组织性能。     

稀土铝锂合金2090Ce焊接热影响区组织和性能研究

采用焊接热模拟试验方法系统地研究了稀土铝锂合金２０９０Ｃｅ焊接热影响区（ＨＡＺ）组织和性能；探讨了稀土元素Ｃｅ和焊接热循环峰值温度的影响及作用机制。结果表明，焊接热循环将使２０９０Ｃｅ合金ＨＡＺ发生软化，而适量的铈能够阻碍合金的再结晶、晶粒长大以及强化相Ｔ１相的溶解和聚集长大，使ＨＡＺ的软化程度降低，塑性得到改善。     

析出强化超细晶粒钢焊接热影响区粗晶区的组织和性能

为研究焊接对800 MPa级Ti、Nb复合微合金化析出强化超细晶粒钢组织性能的影响.运用Gleeble3500热模拟试验机,对实验钢进行单道次焊接热循环试验,并研究冷却速度、冷却时间t8/5对焊接热影响区粗晶区(CGHAZ)组织、性能的影响.结果表明:冷却速度5~15℃/s,CGHAZ的组织为贝氏体,冷却速度进一步增大,会出现马氏体.随着冷却时间t8/5的增加,原奥氏体晶粒尺寸逐渐增加,硬度值逐渐降低,冲击韧性先上升后下降.t8/5为20~120 s时,CGHAZ显微硬度(223~250.4 HV)均小于母材的显微硬度(270.6 HV),出现软化现象,t8/5为20 s时,冲击吸收功最高,为18.2 J,但仅有母材的25.3%.经历焊接热循环后,奥氏体晶粒粗化以及CGHAZ出现贝氏体组织是导致脆化的主要原因.     

9Ni钢焊接热影响区组织转变规律的研究

采用热模拟技术研究了液化天然气储罐用9Ni钢焊接热影响区的组织转变规律。实验结果表明,9Ni钢经历热循环后的显微组织类型包括贝氏体和马氏体两种。低冷却速度条件下,9Ni钢经历热循环后的主要转变产物为贝氏体(包括粒状贝氏体和上贝氏体两种类型);随着冷却速度的提高,组织类型由粒状贝氏体向上贝氏体转化。高冷却速度条件下,经历热循环后的转变产物为马氏体。     

M-A组织对拉伸和冲击性能的影响

用18Cr2Ni4WA钢研究了M－A组织对拉伸和冲击性能的影响。结果表明,粒状组织和粒状贝氏体的屈服强度ρp0.2／ρb、断面收缩率ψ和冲击韧度Ak与马氏体及M－A含量有很好的线性相关性,而且其与马氏体的线性相关性高于与奥氏体的线性相关性。     

10CrNi3MoV钢焊接热影响区组织和性能研究

通过热模拟试验研究了１０ＣｒＮｉ３ＭｏＶ 钢在线能量为１５～１００ｋＪ／ｃｍ 范围内时焊接热影响区（ＨＡＺ）组织和性能的变化规律。结果表明,经过一次热循环后,特别是峰值温度为１３００℃时,冲击韧性显著降低。金相分析表明,冲击韧性的降低与组织和晶粒粗大有关,但总体低温冲击韧性能够保持在较高的水平上（Ａ ｋｖ,－ ５０℃＞６０Ｊ）。经过二次热循环后,线能量较低时,热影响区冲击韧性得到改善;线能量较高时,热影响区冲击韧性大大降低     

Fine structure in the inter-critical heat-affected zone of HQ130 super-high strength steel

The microstructure in the intercritical heat-affected zone (ICHAZ) of HQ130 steel, has been investigated by thermo-simulation test, SEM and TEM. The problem of toughness decrease in the ICHAZ (T _p = 800°C) as well as the effect of M-A constituent and carbide precipitation on brittleness was analysed. The test results indicated that the microstructure in the ICHAZ of HQ130 steel was mostly a mixture of lath martensite (ML) and granular bainite (Bg) with a fine but nonuniform grain structure. The cause of brittleness in the ICHAZ was related to production of the M-A constituent in the local region and carbide precipitation. By controlling the welding heat input carbide precipitation and the formation of the M-A constituent can be avoided or decreased.     

X90钢级管线钢预精焊接头的性能研究

为综合研究X90管线钢的焊接性,选用国内某钢厂轧制的X90管线钢卷板,利用预精焊工艺制备试验钢管4根,采用金相分析、扫描电镜(SEM)断口分析、夏比V型缺口冲击试验、拉伸、弯曲、硬度等试验,研究了焊接接头各个区域的组织和性能.试验结果表明:内外焊缝区组织均为针状铁素体,热影响区(HAZ)粗晶区晶粒粗化严重,主要组织为粒状贝氏体和贝氏体铁素体,在原奥氏体晶界和贝氏体板条内部存在块状或条状的(马氏体-奥氏体)M-A组元;HAZ冲击功离散性较大,出现了单值较低(45 J)的试样,SEM断口分析呈现典型的解理断裂特征;焊接接头抗拉强度805~815 MPa,断裂位置均在HAZ;焊接接头反弯试样易在HAZ出现裂纹和脆断现象;HAZ硬度在220~250 HV之间,较母材下降30 HV左右.HAZ是X90预精焊钢管焊接接头的薄弱环节,为提高X90管线钢的焊接稳定性,应重点研究精焊内外热循环双热影响亚区的组织转变和脆化机理.     

Microstructure characterization in the weld metals of HQ130 + QJ63 high strength steels

Microstructural characterization of the weld metals of HQ130 + QJ63 high strength steels, welded under 80% Ar + 20% CO₂ gas shielded metal arc welding and different weld heat inputs, was carried out by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The relative contents of acicular ferrite (AF) and pro-eutectic ferrites (PF) in the weld metals were evaluated by means of XQF-2000 micro-image analyser. The experimental results indicate that there is acicular ferrite in the grain and some pro-eutectic ferrite on the boundary of original austenite grains when the weld heat input is small (E = 9.6 kJ/cm), but the main microstructure is ferrite side plate (FSP) when the heat input is larger (E = 22.3 kJ/cm). So the weld heat input should be strictly controlled in the range 10 ∼ 20 kJ/cm and then the content of pro-eutectic ferrite is limited to < 25%. Thus weld metals of HQ130 + QJ63 high strength steels with high toughness and excellent resistance to cracking can be ensured.     

高强钢焊接接头显微组织的研究进展

综述了热输入、合金元素、冷却速率和应变速率对高强钢焊接接头显微组织的影响和高温共聚焦显微镜原位观察高强钢显微组织的最新研究进展,总结了高强钢焊接接头粗晶热影响区显微组织的转变机理.结果表明:通过延长冷却时间、减少热输入量、控制合金元素的含量和采用预处理提高应变速率等方法,可以调控高强钢焊接接头显微组织中马氏体、粒状贝氏...     

Hybrid laser/arc welding of advanced high strength steel in different butt joint configurations

An experimental procedure was developed to join thick advanced high strength steel plates by using the hybrid laser/arc welding (HLAW) process, for different butt joint configurations. The geometry of the weld groove was optimized according to the requirements of ballistic test, where the length of the softened heat affected zone should be less than 15.9 mm from the weld centerline. The cross-section of the welds was examined by microhardness test. The microstructure of welds was investigated by scanning electron microscopy and an optical microscope for further analysis of the microstructure of fusion zone and heat affected zone. It was demonstrated that by changing the geometry of groove, and increasing the stand-off distance between the laser beam and the tip of wire in gas metal arc welding (GMAW) it is possible to reduce the width of the heat affected zone and softened area while the microhardness stays within the acceptable range. It was shown that double Y-groove shape can provide the optimum condition for the stability of arc and laser. The dimensional changes of the groove geometry provided substantial impact on the amount of heat input, causing the fluctuations in the hardness of the weld as a result of phase transformation and grain size. The on-line monitoring of HLAW of the advanced high strength steel indicated the arc and laser were stable during the welding process. It was shown that less plasma plume was formed in the case where the laser was leading the arc in the HLAW, causing higher stability of the molten pool in comparison to the case where the arc was leading.     

X70管线钢的局部脆化

研究了X70管线钢模拟热影响区的局部脆化现象和临界再热粗晶区粒状贝氏体的形成及其对韧性的影响规律.结果表明,二次峰值温度为780℃时,M-A组元在原奥氏体晶界成链状分布;二次峰值温度为840℃时,原粗晶区晶界位置生成了细晶贝氏体带,及大颗粒的M-A组元;二次峰值温度为900℃时,M A组元弥散分布,原粗晶区的奥氏体晶界消失.在二次加热过程中奥氏体主要在原粗晶区晶界形核长大.X70钢的粗晶区出现再加热脆化现象,它的脆化温度区间是一个比Ac1-Ac3更窄的温度区间,主要在T2P=Ac1-840℃温度范围内.临界再热粗晶区脆化的主要原因是在晶界上有链状分布的M-A组元.     

Microstructure evolution in heat affected zone of T4003 ferritic stainless steel

In this work, microstructural characteristics and development within the heat affected zone (HAZ) of T4003 ferritic stainless steel (FSS) welded joint were investigated combining experimental measurement with finite element simulation of welding temperature field. The results indicate that the HAZ was characterized with heterogeneous microstructure due to the extensive peak temperature range which could be divided into three sub-zones named as HAZ1, HAZ2 and HAZ3. The HAZ1 (the region next to weld zone boundary) experienced peak temperatures of 1300–1500 °C during welding process. This region presented almost fully δ ferrite microstructure with irregular grain, which was attributed to the high element diffusion rate and the absence of elevated-temperature austenite. The HAZ2 (center region of HAZ) suffered the peak temperatures of 1150–1300 °C. It presented martensite + δ ferrite dual microstructure with limited grain growth due to the formation of γ phase at grain boundaries. The HAZ3 (the region closed to the base metal) was undergone the peak temperatures of 830–1150 °C and was characterized with both martensite and ferrite structure.     

Fatigue crack growth behavior of the simulated HAZ of 800 MPa grade high-performance steel

The present study focuses on the fatigue properties in the weld heat-affected zone (HAZ) of 800 MPa grade high-performance steel, which is commonly used in bridges and buildings. Single- and multi-pass HAZs were simulated by the Gleeble system. Fatigue properties were estimated using a crack propagation test under a 0.3 stress ratio and 0.1 load frequencies. The microstructures and fracture surfaces were analyzed by optical microscopy, scanning electron microscopy, and transmission electron microscopy. The results of the crack propagation test showed that the fatigue crack growth rate of coarse-grained HAZ (CGHAZ) was faster than fine-grained HAZ (FGHAZ), although both regions have identical fully martensite microstructures, because FGHAZ has smaller prior austenite grain and martensite packet sizes, which can act as effective barriers to crack propagation. The fatigue crack growth rate of intercritically reheated CGHAZ (ICCGHAZ) was the fastest among local zones in the HAZ, due to rapid crack initiation and propagation via the massive martensite-austenite (M-A) constituent.     

Ageing and cracking of simulated heat affected zones in 321 stainless steel

The heat affected zone (HAZ) of stabilised austenitic stainless steel welds may exhibit a serious form of intercrystalline cracking during service at high temperature. This type of embrittlement, well known as stress relief cracking, is related to thermal ageing: a fine and abundant intragranular Ti(C,N) precipitation appears near the fusion line during service at high temperature and modifies the mechanical behaviour of the HAZ. To analyse this embrittlement micro mechanism and to assess the lifetime of real components, different HAZ were simulated by various solution heat treatments, cold rolling and ageing conditions. The mechanical behaviour of these resulting materials was investigated using creep and tensile tests on smooth bars. Then, creep tests were carried out and simulated on notched bars by finite element calculations. A damage model was identified from intergranular damage measurements made on notched specimens and compared with calculated mechanical fields. Further tests on fatigue precracked specimens showed that crack propagation occurred under stress relaxation conditions in simulated HAZ material.     

热输入对Q890高强钢焊缝组织及性能的影响

针对国内某钢厂最新研制的Q890高强钢,采用三种不同的热输入对其进行气体保护焊接,研究了不同热输入对焊缝金属组织、硬度及冲击韧性的影响.结果表明,3种热输入下,焊缝组织主要以板条贝氏体为主,并含有粒状贝氏体、少量的板条马氏体和残余奥氏体.随着热输入的增大,焊缝组织中贝氏体铁素体板条粗化,板条马氏体逐渐减少,而粒状贝氏体逐渐增多,部分残余奥氏体由薄膜状向块状转变;焊缝金属硬度随着热输入的增大而下降;焊缝金属的冲击韧性亦呈逐渐下降的趋势.