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基于冷金属过渡(CMT)焊接技术,对1.2 mm厚DP980双相钢进行焊接试验。研究3~6 m/min送丝速度和350~600 mm/min焊接速度工艺参数对焊接接头显微组织与力学性能的影响。结果表明,CMT搭接焊工艺可制备无明显缺陷、成形性良好的DP980双相钢焊件;焊接接头热影响区分为完全相变粗晶区、完全相变细晶区及不完全相变软化区3个部分,主要由马氏体、铁素体和少量贝氏体组成;随着送丝速度的增大,粗晶区晶粒尺寸由13.89μm增大至25.17μm;随焊接速度的增大,粗晶区晶粒尺寸由26.86μm减小至16.11μm;完全相变细晶区平均显微硬度可达400 HV,而软化区硬度则降低至260 HV;在3 m/min送丝速度和500 mm/min焊接速度条件下,焊件拉伸性能最佳,抗拉强度可达967 MPa;由于软化区铁素体富集,断口产生于软化区,断裂方式为韧性断裂。 相似文献
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以DP540双相钢轮辋焊接接头为研究对象,借助光学显微镜(OM)和扫描电子显微镜(SEM)对焊接接头特征区域的显微组织进行了观察与表征。并结合显微硬度的测试和拉伸试验,对接头拉伸断裂位置不同的原因进行了分析。结果表明:DP540双相钢母材为铁素体和马氏体双相组织,但2号试样的组织明显比1号试样细小。焊缝中心区硬度最高,从粗晶区到母材区硬度逐渐降低。1号接头试样的母材组织粗大且马氏体呈大块状,母材硬度为150~170 HV0. 2,在拉伸变形时断裂在粗晶区; 2号接头试样的母材组织细小且马氏体呈岛状弥散均匀分布,母材硬度为160~180 HV0. 2,在拉伸变形时断裂在母材。因此,两种钢母材组织的差异进而影响整个焊接接头的组织分布是造成焊缝断裂位置不同的主要原因。 相似文献
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采用光纤激光焊实现了异种汽车用先进高强钢QP980与DP980的拼焊连接,对异种焊接接头的微观组织、硬度分布进行了观察和测试,对焊接接头的拉伸性能进行了测试,对断口形貌进行了观察和分析。结果表明,焊缝区域的组织全为马氏体组织,且硬度最高(535 HV);两侧焊接热影响区均可分为完全相变区、不完全相变区和回火区三个区域。两侧热影响区中的完全相变区由于冷却速度快全部为马氏体组织,硬度提高;不完全相变区部分形成马氏体,成为马氏体和铁素体的混合区,回火区由于回火马氏体的出现使其硬度下降。QP980侧的回火区由回火马氏体、铁素体和残余奥氏体组成; DP980侧的回火区由回火马氏体和铁素体组成。接头拉伸断裂发生在DP980侧热影响区,抗拉强度达到DP980母材的98. 9%,断后伸长率约为DP980母材的70. 9%,断裂模式为韧性断裂。 相似文献
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采用光纤激光器对厚度为1.6 mm的DP590钢板进行激光对焊。结果表明,DP590钢焊缝组织主要是板条马氏体,硬度明显高于母材;热影响区可分为完全淬火区、不完全淬火区、回火区;焊接接头硬度分布不均匀,在焊缝有着最高硬度;热影响区过渡到母材时,硬度急剧下降,且存在轻微的软化区,最低硬度仅为176.4 HV;随着焊接速度的升高,焊接接头各区域宽度变窄,硬度随之增加,当焊速达到5 m/min时,其焊缝的最高硬度为所有试样中的最大值;在垂直于焊缝的负载下,3~5 m/min焊接速度的拉伸试样均断裂在母材,为韧性断裂。 相似文献
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Chaojie Xie Shanglei Yang Haobo Liu Qi Zhang Yaming Cao Yuan Wang 《Journal of Materials Engineering and Performance》2017,26(8):3794-3801
In this paper, cold-rolled DP590 dual-phase steel sheets with 1.5 mm thickness were butt-welded by a fiber laser, and the evolution and effect on microhardness, tensile property and fatigue property of the welded joint microstructure were studied. The results showed that the base metal is composed of ferrite and martensite, with the martensite dispersed in the ferrite matrix in an island manner. The microstructure of the weld zone was lath-shaped martensite that can be refined further by increasing the welding speed, while the heat-affected zone was composed of ferrite and tempered martensite. The microhardness increased with increasing welding speed, and the hardness reached its highest value—393.8 HV—when the welding speed was 5 m/min. Static tensile fracture of the welded joints always occurred in the base metal, and the elongation at break was more than 16%. The conditional fatigue limits of the base metal and the weld joints were 354.2 and 233.6 MPa, respectively, under tension–tension fatigue tests with a stress rate of 0.1. After observation of the fatigue fracture morphology, it was evident that the fatigue crack of the base metal had sprouted into the surface pits and that its expansion would be accelerated under the action of a secondary crack. The fatigue source of the welded joint was generated in the weld zone and expanded along the martensite, forming a large number of fatigue striations. Transient breaking, which occurred in the heat-affected zone of the joint as a result of the formation of a large number of dimples, reflected the obvious characteristics of ductile fracture. 相似文献
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采用焊接热模拟的方法,研究一种980 MPa级低碳贝氏体高强钢焊接接头HAZ不同区域,通过对各个区域的组织及相的分析,以及相应的拉伸及冲击试验研究了此类高强钢的组织和性能.结果表明,粗晶区的冲击性能最好,细晶区的冲击性能最低,为热影响区的薄弱环节.粗晶区组织为均匀粗细相间的板条贝氏体组织;在板条贝氏体上弥散析出碳化物;板条贝氏体界面上的奥氏体薄膜的存在是粗晶区韧性提高的原因.细晶区为孪晶马氏体+少量的板条马氏体,孪晶马氏体是导致细晶区性能下降的主要原因.Abstract: Microstructure and mechanical properties of HAZ of 980 MPa low carbon bainite high strength steel joints were studied . The different regions of welded joint HAZ were simulated by welding thermal simulation technique. Microstructure observation, phase analysis, and corresponding tensile and impact test for different regions of welded joint HAZ were taken. The results indicate: the impact property of coarse grain zone is the best, while the impact property of fine grain zone is the worst. So the fine grain zone is the weakest part of the welded joint. Microstructure of coarse grain zone is uniform interweaved coarse and fine lath martensites, and precipitation acicular ferrite are distributed between the lath martensites. Toughness of coarse grain zone is increased owing to the austenite thin film adherent lath martensite interface. Microstructure of fine grain zone are twin martensite and a small number of lath maarten-site, only minor acicular ferrite are distributed in the twin martensite . Toughness of fine-grained zone was decreased owing to twin martensite. 相似文献
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摘要: 采用等离子弧焊对3 mm厚的Q345低合金钢与430不锈钢进行异种钢焊接,并对接头微观组织、力学性能及耐腐蚀性能进行了研究。结果表明,当转弧电流为100 A时,等离子弧焊Q345B/430异种钢接头的焊缝组织为均匀分布的马氏体及针状铁素体,焊接接头综合性能优良。随着电流的增大,焊缝组织转变为粗大板条马氏体及铁素体。两侧热影响区组织均发生一定程度的粗化,且Q345B侧热影响区出现魏氏组织。焊接接头于焊缝处显微硬度最大,不同转弧电流条件下异种钢显微硬度分布趋势大致相同。不同转弧电流下,焊接接头抗拉强度均与430不锈钢相近,且均断裂在靠近焊缝的430母材侧,转弧电流为100 A时接头抗拉强度最大值427 MPa。焊接接头的耐腐蚀性能与焊接电流呈负相关趋势。
创新点: 试验结果为铁素体低合金钢与铁素体不锈钢异种钢接头的应用提供了工艺数据与支撑。 相似文献
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与传统电弧焊相比,激光焊接厚板优势明显。采用纯激光焊和激光电弧复合焊等多道焊接技术实现了28 mm厚10Ni3CrMoV钢的高效焊接,采用光学显微镜分析焊缝、热影响区和焊缝重叠区的组织,激光复合焊缝组织主要为针状铁素体,纯激光焊缝、粗晶区和细晶区组织主要为板条马氏体,激光复合焊缝重叠区组织为粒状贝氏体+马氏体,纯激光焊缝和激光复合焊缝重叠区组织为马氏体+少量粒状贝氏体。测试了焊接接头的力学性能,结果表明,激光复合焊缝金属的冲击韧性较高,焊接接头的抗拉强度和屈服强度与母材相当,延伸率略小于母材,焊接接头的最大硬度小于360 HV,弯曲性能合格。 相似文献
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针对6 mm厚的921A钢板,采用激光-MAG复合焊接工艺进行对接焊试验,并对焊接接头的显微组织、硬度、拉伸性能、耐腐蚀性能等进行了分析。结果表明,采用激光-MAG复合焊工艺可获得成形连续美观的焊接接头,无未熔合、裂纹、气孔等缺陷;焊缝组织为针状铁素体、少量沿晶界析出的先共析铁素体及长条状贝氏体,热影响区组织为马氏体;焊接接头的拉伸性能和冲击性能均符合国家标准要求,焊缝强度高于母材,但塑韧性低于母材。峰值硬度在热影响区,为315 HV,焊缝硬度约为280 HV,符合最高硬度不得超过410 HV的规定。焊缝耐电化学腐蚀性能最强,母材次之,热影响区最低;激光和MAG电弧2种热源共同作用区域的组织分布更加均匀,硬度及耐腐蚀性能较激光单独作用区域有了明显改善。
创新点: 采用激光-MAG复合焊实现了6 mm厚度921A钢板无缺陷对接焊的一次焊接成形。焊缝晶粒更加细化,分布更加均匀;焊缝抗拉强度、硬度、电化学腐蚀性能均高于母材,冲击吸收能量满足船级社要求。 相似文献
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对聚变堆用CLAM钢进行了激光焊接试验,并对接头进行740℃/1 h焊后回火处理,分别对热处理前、后接头的显微组织及性能进行了研究.结果表明,获得了成形良好、无缺陷的焊接接头;焊态下,焊缝由淬硬的板条马氏体和大量的δ铁素体组织组成.完全淬火区由板条马氏体和极少量的δ铁素体组成,其硬度高达545 HV;焊后热处理使焊缝及完全淬火区的板条马氏体分别转变为碳化物弥散分布的回火马氏体和回火索氏体组织.显著降低了接头的淬硬程度,最大硬度仅比母材高约15%;焊后回火热处理前、后接头的抗拉强度均高于基体母材,虽然焊后热处理使接头强度有所降低,但仍达到原始母材的98%以上. 相似文献
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The use of dual phase (DP) steels in the automobile industry unavoidably involves welding and dynamic loading. The aim of this investigation was to evaluate the microstructural change and mechanical properties of laser welded dissimilar DP600/DP980 steel joints. The dissimilar joints showed a significant microstructural change from nearly full martensite in the fusion zone (FZ) to the unchanged ferrite-martensite dual-phase microstructure in the base metal. The welding resulted in a significant hardness increase in the FZ but the formation of a soft zone in the heat-affected zone (HAZ). The dissimilar welded joints were observed to exhibit a distinctive unsymmetrical hardness profile, yield-point-like phenomenon, and single-stage work hardening characteristic, with yield strength and work hardening rate lying in-between those of DP600 and DP980 base metals, and ultimate tensile strength equivalent to that of DP600 base metal. Although the welded joints showed a lower fatigue limit than the base metals, the fatigue life of the welded joints at higher stress amplitudes was almost the same as that of the DP600 base metal. The welded joints failed in the soft zone at the DP600 side under tensile loading and fatigue loading at the higher stress amplitudes. Fatigue crack initiation occurred from the specimen surface and crack propagation was characterized by typical fatigue striation together with secondary cracks. 相似文献
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为解决超高强钢焊接冷裂纹问题,采用强度低于母材的高氮奥氏体丝材进行GMAW工艺试验,研究在不同坡口角度下超高强钢焊接接头组织性能. 结果表明,采用该焊丝获得的接头焊缝成形良好,焊缝截面未见裂纹缺陷. 熔合线附近组织主要为针状和板条状马氏体,焊缝组织主要为奥氏体及被奥氏体基体所包围的铁素体树枝晶. 熔合线附近马氏体区硬度平均值为530 HV;焊缝区硬度平均值为275 HV. 相对于60°坡口接头,90°坡口接头熔合线附近马氏体组织硬度更高. 90°坡口接头的抗拉强度平均达到850 MPa,最高达887 MPa,而60°坡口接头抗拉强度平均仅为690 MPa. 相似文献
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Study on the microstructure and hardness of in-service welded joint of X70 pipeline steel 总被引:1,自引:0,他引:1
Hydrogen induced cracking (HIC) is one of the main problems of in-service welding onto active pipeline. Microstructure and hardness of welded joint have a vital effect on hydrogen induced cracking. The microstructure and hardness of welded joint of XTO pipeline steel were studied using simulation in-service welding device. The results show that the main microstructures of in-service welded seam are grain boundary ferrite , intracrystalline acicular ferrite , as well as small amount of widmanztatten structure. The main microstructures of coarse grain heat-affected zone (CGHAZ) are coarse granular bainite, lath ferrite and martensite. Metastable phases such as martensite and lath ferrite are found in CGHAZ because of the too quick cooling velocity a'nd the hardness of the CGHAZ is high. 相似文献
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对Ti-22Al-27Nb合金进行了线性摩擦焊及热处理试验,并对热处理前后焊接接头的微观组织和显微硬度进行测量分析. 结果表明,利用线性摩擦焊方法焊接Ti-22Al-27Nb合金得到的接头无焊接缺陷. 焊态下,焊缝区形成了B2单相区组织. 热力影响区为B2 + O + α2相三相区,出现等轴α2相,针状O相几乎消失. 热处理后在焊缝区析出板条状O相和针状O相,热力影响区为O相均匀分布的两相区. 母材处的显微硬度值最低约为300 HV,随着向焊缝靠近,显微硬度值逐渐增加,焊缝中心达到最大值354 HV. 热处理后,由于板条O相和针状O相的沉淀析出,使焊缝中心显微硬度急剧增加. 相似文献