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1.
焊接热输入对X80焊管焊缝组织与性能的影响 总被引:2,自引:0,他引:2
针对双面螺旋埋弧焊管所具有的先内焊后外焊的焊接顺序特点,以实际焊缝为研究对象,采用焊接热循环理论,利用焊接热模拟技术、现代材料力学性能检测技术和显微分析方法,对X80管线钢内焊缝在不同热输入下的韧性分布规律以及组织特征进行了研究.结果表明:当焊接线能量为17~35kJ/cm时,X80管线钢焊缝粗晶热影响区(WCGHAZ)可获得较好的韧性水平,其中线能量为20kJ/cm时,WCGHAZ可获得最佳韧性水平.当焊接线能量小于17kJ/cm和大于35kJ/cm时,X80管线钢WCGHAZ的韧性水平都有所下降.因此可将17~35kJ/cm的线能量作为X80管线钢外焊缝的推荐焊接工艺规范. 相似文献
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采用手工焊条电弧焊和熔化极活性气体保护焊对超细晶Q460钢进行了焊接,分析表征了焊接接头的组织结构、显微硬度和冲击韧性的变化规律。研究结果表明,采用E5515焊条焊接,焊缝金属主要为先共析铁素体、多边形铁素体与少量珠光体。采用ER55-G焊丝,熔化极活性气体保护焊,焊缝金属主要由针状铁素体和少量多边形铁素体组成,焊丝中Ti元素的添加有利于获得针状铁素体组织。采用较小的焊接线能量,超细晶Q460钢热影响区粗晶区组织为粒状贝氏体组织。焊缝金属的显微硬度高于热影响区和母材的显微硬度,热影响区未出现软化现象。冲击试验表明,焊缝金属和热影响区均具有较高的冲击韧性,而且热影响区的韧性高于焊缝金属的韧性。 相似文献
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采用10 kJ/cm和15 kJ/cm两种焊接热输入对Q1100超高强钢进行熔化极气体保护焊,研究焊接接头的组织性能及局部腐蚀行为。结果表明:两种热输入焊接接头的焊缝组织主要为针状铁素体和少量的粒状贝氏体,粗晶区组织均为板条贝氏体,细晶区组织均为板条贝氏体和粒状贝氏体,临界相变区组织为多边形铁素体、马奥岛和碳化物的混合组织。两种热输入焊接接头中电荷转移电阻均为母材>热影响区>焊缝区,母材耐蚀性最好,热影响区次之,焊缝区耐蚀性最差。在腐蚀过程中,焊缝区作为阳极最先被腐蚀,当腐蚀一定时间后,腐蚀位置发生改变,阳极腐蚀区域转移到母材区,而焊缝区作为阴极得到保护。热输入为10 kJ/cm时,焊接接头具有更好的低温韧性和耐蚀性,其焊缝和热影响区-40℃冲击功分别为46.5 J和30.2 J。 相似文献
4.
通过调整焊接线能量研究了X100管线钢CO2气体保护药芯焊焊接接头的组织及其对维氏显微硬度和断裂韧性(CTOD)的影响规律.结果表明:和15kJ/cm焊接线能量相比,30kJ/cm线能量下焊接接头的显微硬度较低,粗晶区的断裂韧性也较低,其主要原因是30kJ/cmm焊接线能量下组织中的贝氏体含量减小使得材料强度降低. 相似文献
5.
为制定合理的焊接工艺,保证焊接质量,设置不同焊接热输入进行了10CrNi3MoV钢MAG焊接。采用微观组织分析、断口观察、力学测试等手段研究了焊接热输入对接头组织及性能的影响。结果表明,热输入较小时(E=11.0 kJ·cm-1、E=14.4 kJ·cm-1),焊缝组织以针状铁素体为主,并含有部分粒状贝氏体、先共析铁素体等;热输入较大时(E=18.1 kJ·cm-1),针状铁素体占比降低,粒状贝氏体、先共析铁素体等增多,组织粗化。随热输入的增大,粗晶区晶粒粗化,组织由板条马氏体逐步转变为板条贝氏体,板条界限模糊,并有粒状贝氏体出现;焊缝金属强度降低,冲击韧性先略有升高后显著降低,断裂形式由微孔聚缩型韧断变为准解理/韧性混合断裂。热输入E=14.4 kJ·cm-1时,焊缝组织以细密的针状铁素体为主,具有最佳强韧性匹配。 相似文献
6.
实际焊接过程中焊接参数会影响焊接热输入,进而影响焊接接头的显微组织和性能.为此,研究了一系列焊接热输入条件下Q345R钢焊接接头的显微组织及其在湿硫化氢环境中的应力腐蚀敏感性.结果表明:当焊接热输入从44.2 kJ/cm增加到49.7 kJ/cm时,铁素体晶粒增大;当焊接热输入达到55.3 kJ/cm时,焊缝区组织出现了针状铁素体;在湿硫化氢环境下慢应变速率拉伸,所有焊接热输入下的焊接接头均出现明显的应力腐蚀开裂,同时发现在相同浓度的湿硫化氢环境下,当焊接热输入从44.2 kJ/cm增加到49.7 kJ/cm时,焊接接头的应力腐蚀敏感性指数随之增大,当焊接热输入增大到55.3 kJ/cm时,由于焊缝区出现了针状铁素体,使其应力腐蚀敏感性得到缓解. 相似文献
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为探讨在役焊接这种严酷的焊接条件下管线钢焊接热影响区显微组织的变化,采用焊接热模拟技术、金相分析及透射电镜对比研究了X70管线钢在役焊接热影响区和常规焊接热影响区的金相组织和精细结构.结果表明,在役焊接的快速冷却只对粗晶区的金相组织产生了较大影响,而对过渡区、细晶区和类母材区的金相组织几乎没有影响.金相显微镜下两者粗晶区的组织均为贝氏体铁素体和粒状贝氏体,但各组织的形态和数量不同.在透射电镜下观察,两者粗晶区的精细结构有较大差异,在役焊接粗晶区生成了少量细小的横穿贝氏体铁素体板条的板条马氏体,常规焊接粗晶区生成了少量的块状铁素体组织. 相似文献
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G. Huang X. L. Wan O. Isayev O. Hress I. Rodionova 《Materials Science & Technology》2017,33(5):602-614
The effects of Cu content on microstructure and impact toughness in the simulated coarse-grained heat-affected zone (CGHAZ) of high-strength low-alloy steels were investigated. It has been observed that the microstructure in the simulated CGHAZ of Cu-free steel is dominated by a small proportion of acicular ferrite and predominantly bainite with martensite–austenite constituent. Whereas, in the 0.45 and 1.01% Cu-containing steels, the acicular ferrite increased significantly due to the effective nucleation on intragranular inclusions with outer layer of MnS and CuS. The formation of acicular ferrite is attributed to superior high heat-affected zone impact toughness in the 0.45% Cu-containing steel. Furthermore, the increasing martensite–austenite constituent and ε-Cu precipitates in the simulated CGHAZ of 1.01% Cu-containing steel caused degradation in impact toughness. 相似文献
12.
用热模拟方法研究了氮含量对钒微合金钢粗晶热影响区(CGHAZ)的组织和性能的影响。结果表明,氮含量为0.0031%或0.021%时,CGHAZ的韧性较差。氮含量0.0031%时CGHAZ中有少量的Ti(C,N),晶界铁素体(GBF)较少,晶内有大量尺寸较大的侧板条铁素体(FSP),解理裂纹沿FSP的直线扩展使其韧性较差。氮含量0.021%时在CGHAZ中生成了较为粗大的(Ti, V)(C, N)和GBF,解理裂纹沿GBF扩展使其韧性较差。氮含量为0.012%时低温韧性较好,在CGHAZ中生成了大量细小的(Ti, V)(C, N)粒子,且GBF尺寸相对较小,晶内有大量的针状铁素体(AF)。这些因素都有利于阻止裂纹扩展,使其低温韧性显著提高。 相似文献
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Sanghoon KimDonghwan Kang Tae-Won KimJongkwan Lee Changhee Lee 《Materials Science and Engineering: A》2011,528(6):2331-2338
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. 相似文献
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Jae-il Jang Jang-Bog Ju Baik-Woo Lee Dongil Kwon Woo-Sik Kim 《Materials Science and Engineering: A》2003,340(1-2):68-79
This study investigates the correlation between the microstructural change and fracture characteristics in the coarse-grained heat-affected zones (CGHAZs) of the newly developed quenching, lamellarizing and tempering (QLT)-processed 9% Ni steel. The microscopic fracture behaviors of the various sub-zones within the HAZs including local brittle zone (LBZ) were estimated using simulated HAZ specimens. Both results of Charpy impact tests and in situ scanning electron microscopy (SEM) observations on simulated CGHAZ specimens show that the inter-critically reheated coarse-grained HAZ (IC CGHAZ) is a primary LBZ of this steel at cryogenic temperature, but not at room temperature. Microstructural analysis suggests that, unlike in other studies, the cryogenic LBZ phenomenon of the IC CGHAZs cannot be explained simply by the amount of martensite–austenite (M–A) constituents, but is mainly associated with the carbon contents in them. From all results obtained, a mechanism for microscopic toughness change among the CGHAZs is proposed and discussed. 相似文献
15.
An increase of nitrogen content in a 0.02 wt% Ti-containing carbon-manganese steel resulted in a low coarsening rate of TiN particles in the heat-affected zone (HAZ), which led to an accelerated ferrite transformation instead of ferrite side plates during weld cooling cycle. The mixed microstructure of ferrite side plate, acicular ferrite and grain boundary polygonal ferrite in the simulated HAZ produced higher toughness. However, the increase of nitrogen content gradually increased the free nitrogen content in the HAZ and deteriorated HAZ toughness. Impact energy of the simulated HAZ (with Δt8/5 ∼60 s) at –20 °C deteriorated by about 97 J per 0.001 wt% free nitrogen, in the free nitrogen range from 0.0009 wt% to 0.0034 wt%, even though the HAZ has the tough mixed microstructure. Cooling time after welding influenced the HAZ microstructure and toughness as well, and maximum toughness was obtained when cooling produced the tough mixed microstructure. Therefore, for a high HAZ toughness, both nitrogen content and cooling time should be controlled to obtain the tough mixed microstructure and to keep the free nitrogen content low. The optimal nitrogen content and cooling time from 800 °C to 500 °C were 0.006 wt% and between 60 s and 100 s, respectively, in this experiment. 相似文献
16.
Weihua Sun )? Guodong Wang ) Jiming Zhang ) Dianxiu Xia ) Hao Sun ) ) State Key Laboratory of Rolling Automation Northeastern University Shenyang China ) R & D Center Jinan Iron Steel Group Co. Ltd. Jinan China 《材料科学技术学报》2009,(6)
In this paper, microstructure and mechanical properties of welding metals in 610 MPa high strength low alloy (HSLA) were studied after high-heat-input welding. Both the base material and the weld joint proved excellent strength and toughness by vibratory electrogas arc (VEGA) welding under 90 to 100 kJ/cm heat-input. The heat-affected zone (HAZ) was comprised of fine-grain zone (FGZ) and coarse-grain zone (CGZ), which characterizes fine granular structure and lathing-bainite substructure. It has found that ... 相似文献
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In this work,the stress corrosion cracking(SCC)behavior of E690 steel base metal(BM)and different heat-affected zone(HAZ)microstructures,i.e.,coarse grain HAZ(CGHAZ),fine grain HAZ(FGHAZ),and intercritical HAZ(ICHAZ),was investigated at different cathodic potentials in artificial seawater by slow strain rate tensile tests,scanning electron microscopy and electron back-scattered diffraction measurements.The results show that the HAZ microstructures and BM exhibit different SCC susceptibilities:FGHAZ相似文献
18.
The microstructures and mechanical properties of coarse grain heat-affected zone (CGHAZ) of domestic X70 pipeline were investigated.
The weld CGHAZ thermal cycles having different cooling time Δt
8/5 were simulated with the Gleeble-1500 thermal/mechanical simulator. The Charpy impact absorbed energy for toughness was measured,
and the corresponding fractographs, optical micrographs, and electron micrographs were systematically investigated to study
the effect of cooling time on microstructure, impact toughness, and fracture morphology in the CGHAZ of domestic X70 pipeline
steel during in-service welding. The results of simulated experiment show that the microstructure of CGHAZ of domestic X70
pipeline steel during in-service welding mainly consists of granular bainite and lath bainite. Martensite–austenite (M–A)
constituents are observed at the lath boundaries. With increase in cooling time, the M–A constituents change from elongated
shape to massive shape. The reduction of toughness may be affected by not only the M–A constituents but also the coarse bainite
sheaves. Accelerating cooling with cooling time Δt
8/5 of 8 s can be chosen in the field in-service welding X70 pipeline to control microstructures and improve toughness. 相似文献
19.
Yu Liu Guangqiang Li Honghong Wang Kaiming Wu R. D. K. Misra 《Materials Science & Technology》2017,33(15):1750-1764
The effects of Cu and Al addition on the microstructure and fracture in the coarse-grained heat-affected zone (CGHAZ) of high-strength low-alloy steels with superior toughness were studied and compared with the X70 pipeline base steel counterpart. The microstructure in base steel was dominated by a small fraction of acicular ferrite and predominantly bainite. However, acicular ferrite microstructure was obtained in Cu-bearing steel, which nucleated on complex oxide with outer layer of MnS and CuS because of Cu addition. The microstructure in Al-bearing steel consisted of bainite with ultrafine martensite–austenite constituent, which was refined by Al addition. CGHAZ in Cu-bearing and Al-bearing steels had superior impact toughness and ductile fracture, which were attributed to acicular ferrite and ultrafine martensite–austenite constituent, respectively. 相似文献
20.
Hang Yuan Jingshe Li Hao Guo Wei Liu Tiantian Wang 《Materials Science & Technology》2020,36(14):1574-1586
The effect of adding MgO nanoparticles to ship plate steel at welding heat-affected zones (HAZs) was experimentally studied. The results showed that the added nanoparticles obviously optimised the inclusions; the average size of the inclusions was significantly reduced, and the distribution was relatively uniform. The toughness of the base metal and HAZ increased by 20–60 J, apart from a slight decrease in the strength of the fine-grained heat-affected zone and a nearly unchanged strength in the coarse-grained heat-affected zone, and approximately ~2?μm (Mg–Al–Ti)O-containing inclusions induced acicular ferrite effectively, thereby simultaneously enhancing the strength and toughness of the inter-critical heat-affected zone. In conclusion, these performance improvements in both the base metal and HAZ could be attributed to grain refinement and inclusion optimisation. 相似文献