共查询到19条相似文献,搜索用时 140 毫秒
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使用三种热输入对船用高强药芯焊丝进行CO_2气体保护焊,使用光学显微镜(OM)、扫描电子显微镜(SEM)、透射电镜(TEM)以及电子背散射技术(EBSD)等手段研究了热输入对熔敷金属微观组织及低温韧性的影响。结果表明,使用三种热输入的熔敷金属组织主要由针状铁素体(AF)、侧板条铁素体(FSP)和少量残余奥氏体(RA)组成;随着热输入的增加铁素体由针状向板条状转变,其中针状铁素体的含量降低而镐牙状的侧板条铁素体的含量提高,板条间的残余奥氏体由薄膜状向块状转变;同时,随着热输入的增多熔敷金属中尺寸小于1μm的夹杂物含量减少而夹杂物的总含量增多;随着热输入的增加20°~50°的大角度晶界减少,熔敷金属的强度、塑性和低温韧性随之降低,-40℃冲击断口的形貌由韧窝+准解理向解理过渡。 相似文献
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通过药皮过渡添加B,研究了微量B对440MPa级焊条熔敷金属低温冲击韧性的影响。试验发现,冲击韧性对B含量的变化较敏感,同时当焊缝中Ti含量不同时,B含量的影响也不同。当Ti含量为0.01%~0.04%(w)时,B含量在30×10-6(w)左右时韧性最好;当Ti含量为0.04%~0.07%时,B含量在(40~90)×10-6范围内韧性最好。B含量适中时熔敷金属组织几乎全是均匀细小的针状铁素体,B含量过低组织中出现大量的先共析铁素体,B含量过高则会生成沿原奥氏体晶界分布的粒状贝氏体和上贝氏体。 相似文献
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测试5种不同Mo含量的船用高强钢焊条的熔敷金属力学性能,采用光学显微镜和透射电镜进行微观组织观察和分析,并采用Jamtpro软件模拟计算熔敷金属的焊接CCT图。结果表明,随着Mo含量增多,熔敷金属屈服强度和抗拉强度显著提升,但冲击韧性及塑性呈下降趋势;焊接CCT曲线逐渐向右下方移动,熔敷金属的组织由韧性较好的针状铁素体逐渐向硬脆的贝氏体和马氏体转变;当Mo含量高于0.482%时,熔敷金属中会产生对韧性不利的M-A组元,当Mo含量高于0.887%时,熔敷金属中会析出Mo的碳化物,造成严重脆化。 相似文献
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针状铁素体焊缝金属腐蚀行为的研究 总被引:3,自引:0,他引:3
低合金高强钢广泛应用于油气管道钢结构件的焊接生产中.对于其焊缝中包含的大量的针状铁素体组织的腐蚀行为,国内外尚未进行广泛的研究.本文针对多种焊接工艺规范:1.91kJ/mm, 2.70kJ/mm 及 4.78kJ/mm条件下的针状铁素体焊缝金属,分别对其进行了25℃空气中、25℃通N2除氧及50℃通N2除氧3种NACE溶液中腐蚀行为的研究.极化曲线测试结果表明,随着焊缝熔敷金属中针状铁素体比例的增加,阴极电流不断变大,熔敷金属的极化电阻迅速减小,从而影响了焊缝熔敷金属在腐蚀介质中的耐腐蚀性. 相似文献
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《中国材料进展》2019,(12)
690 MPa级以上高强钢的发展和工程应用受限于缺乏与其强韧性相匹配的焊接材料,其根本原因是以针状铁素体为主的690 MPa级以下高强钢熔敷金属的强韧化理论已经不能指导新一代高强钢焊接熔敷金属的设计。因此,解决该问题的关键是寻求最佳的熔敷金属微观组织结构。综述了690 MPa级以上高强钢焊接熔敷金属中出现的联合贝氏体和其它各类微观组织对其强韧性的影响。其中,由不同形貌贝氏体相和针状铁素体相组成的复相分割结构可使焊接熔敷金属实现良好的强韧性匹配;然而,联合贝氏体作为下贝氏体的一种,其大尺寸的特点会显著降低高强钢焊接熔敷金属的强韧性;此外,可以通过物理冶金改善高强钢焊接熔敷金属的性能。 相似文献
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采用金相显微镜、扫描电镜、拉伸试验、弯曲试验和晶间腐蚀试验分析了690镍基合金ENiCrFe-7焊条中各元素对熔敷金属组织、缺陷和力学性能的影响,研制符合核电设备使用要求的焊条.研究表明:焊缝熔敷金属中的沿晶裂纹引起焊缝金属拉伸性能、冲击韧性和弯曲性能的降低;随着焊缝中Nb,Ti元素含量的增加,焊缝析出相(Nb,Ti)(C,N)和NbC的数量增加,焊缝中滑移晶界受到析出相的钉扎,裂纹扩展受到抑制,焊缝熔敷金属的强度、塑性和弯曲性能得到提高;Nb和Ti的加入减小了Cr_(23)C_6析出数量,抑制了晶间腐蚀裂纹的产生.新研制的镍基焊条满足核电设备对焊缝熔敷金属的性能要求. 相似文献
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H. Fu Dr. Y. Miao X. Chen K. Hu Z. Tian 《Materialwissenschaft und Werkstofftechnik》2007,38(3):233-238
The microstructure, tensile and impact behaviour of high‐carbon Si‐Cr cast steel containing rare earth (RE) and titanium have been determined after austempering. The additions of RE and titanium refined the primary austenite grain size resulting in improving toughness. The addition of silicon handicapped the formation of carbide and carbide‐free bainitic ferrite and carbon enriched retained austenite could be obtained in the austempering structures of high‐carbon Si‐Cr cast steel, which had excellent mechanical properties and abrasion resistance. Moreover, the basic tendency of the mechanical properties of high‐carbon Si‐Cr cast steel influenced by the austempering temperature was that the hardness and tensile strength reduced and the impact toughness and fracture toughness increased with increasing temperature. The comprehensive properties were the best while austempering at 330oC. 相似文献
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Furen XIAO Mingchun ZHAO Yiyin SHAN Bo LIAO and Ke YANGKey Laboratory of Metastable Materials Science Technology Yanshan University Qinhuangdao ChinaInstitute of Metai Research Chinese Academy of Sciences Shenyang China 《材料科学技术学报》2004,20(6):779-781
Acicular ferrite microstructure was achieved for an ultralow carbon pipeline steel through the improved thermome chanical control process (TMCP), which was based on the transformation process of deformed austenite of steel. Compared with commercial pipeline steels, the experimental ultralow carbon pipeline steel possessed the satisfied strength and toughness behaviors under the current improved TMCP, although it contained only approximately 0.025% C, vvhich should mainly be attributed to the microstructural characteristics of acicular ferrite. 相似文献
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XiaohuaiXUE LuhaiWU BainianQIAN JingliLI SongnianLOU 《材料科学技术学报》2003,19(6):580-582
X80 pipeline steel produced by TMCP has high strength and high toughness with ultrafine grain microstructure. The microstructure coarsens and the toughness worsens at the coarse grained (CG) HAZ apparently after weld simulation. The experimental results indicated that the bainitic ferrite and the second phases formed at cooling are differently as the variation of carbon in base metal. In low carbon steels, the bainitic ferrite laths are long and narrow, the second phases are complex including residual austenite, martensite, the M-A constituent and the Fe3C carbide. The formation of Fe3C carbide is the main reason of the poor toughness in CG HAZ. The ultralow carbon in base metal, however, can improve the CG HAZ toughness through restraining the formation of carbides, decreasing the M-A constituent, increasing the residual austenite content, which are beneficial to the CG HAZ toughness. 相似文献
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The effects of Si,Mn and Al on the microstructure and mechanical properties of ADl weld have been studied.The microstructure of ADl weld metal mainly consists of bainitic ferrite and retained austenite.Mechanical properties of Adl weld increase with increasing Si content,but an excess of Si(3.79%) results in decreasing the austemperability owing to decreasing the carbon content of the matrix austenite.Mn increases the retained austenite volume fractio,but the ductility and impact toughness of weld obviously decrease with increasing Mn content because of increased amount of martenite and twin martenite.In the range of 0.13%-0.64%Al ,increasing Al content favours improving the mechanical properties of ADl weld.Therefore,it is very important to select suitable Si,Mn and Al contents to improve mechanical properties of ADl weld . 相似文献
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Studies of an industrial low-carbon steel (B450NbRE) suggest that the impact toughness is unexpectedly low under its practical service, probably resulting from the unstable recovery of rare earths (RE) in steelmaking. The purpose of this work is to investigate the effect of RE on the impact toughness in low-carbon steel. The B450NbRE steels with content of 0.0012–0.0180 wt.% RE were produced by vacuum induction furnace. The impact toughness and microstructure were investigated after hot rolled. The Gleeble-1500 thermal simulator was used to validate the effect of RE on the microstructure. The results indicate that the microstructure of hot-rolled steels is characterized by polygonal ferrite, quasi-polygonal ferrite, bainite and pearlite. The impact toughness increases with RE contents reaching the peak with content of 0.0047 wt.% RE, such a change exhibits the same rule as the case of the ferrite amount. However, this improvement in impact toughness is not only due to an increase in ferrite amount, but also the fine grained structure and the cleaner grain boundaries. And content of 0.0180 wt.% RE is excessive. Such an addition of the RE resulted in the martensite precipitates at the grain boundaries, which are extremely detrimental to impact toughness. 相似文献
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《Composites》1990,21(3):205-215
The addition of small amounts of short carbon fibres to cement causes a great increase in the composite material toughness and tensile, flexural, and impact strength. In order to understand how cement properties are improved by carbon fibres and to understand the level of adhesion and interfacial failure mode which are necessary to obtain optimum carbon fibre reinforced cement (CFRC) properties, various admixtures were included in cement and CFRC. Their effects on the carbon fibre-cement adhesion and the composite material properties were determined using fibre pull-out and composite material flexural tests. The addition of latex to CFRC, and hot water curing of CFRC dramatically increase fibre-matrix adhesion. Both latex (with an anti-foam agent) and hot water curing increase flexural strength by 40% over adhesion changes the failure mode from fibre pull-out to fibre rupture. Optimum strength and toughness of CFRC result from an intermediate level of fibre-matrix adhesion. 相似文献
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M. Fattahi N. NabhaniM.R. Vaezi E. Rahimi 《Materials Science and Engineering: A》2011,528(27):8031-8039
The effect of TiO2 nanoparticles in the electrode coating on the impact toughness of three weld metals prepared by the shielded metal arc welding process was investigated and the main factors affecting the impact toughness were discussed. The microstructure, mechanical properties and fracture surface morphology of the weld metals have been evaluated and the results are compared. When the content of TiO2 nanoparticles in the composition of electrode coating is increased, the morphology of ferrite in the microstructure of columnar zone will change from Widmanstätten ferrite to acicular ferrite. This finally changes to allotriomorphic ferrite when the amount of TiO2 nanoparticles in the electrode coating goes relatively high. Furthermore, the addition of TiO2 nanoparticles is effective in refining the ferrite grain size of the reheated microstructures of weld metals. This effect is attributed to the increased number of nucleation sites on the oxide nanoparticles. The impact toughness of the weld metal was improved by adding TiO2 nanoparticles, especially when a medium TiO2 nanoparticle content was used in the electrode coating. A significant increase in the impact toughness of weld metal was shown to be due to the increased percentage of acicular ferrite and refinement of microstructure. 相似文献
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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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Ultra-fine grained steel bars were recently developed by thermo-mechanical controlled rolling with rapid cooling for increasing the strength of low carbon and low alloy steels. The developed steels are characterized by fine ferrite grains of less than 1 m and high strength as a result of grain refinement. However, their correlations between tensile properties and impact behavior are not well understood. In this paper, impact absorbed energy (E
p) and dynamic fracture toughness (J
Id) were used to evaluate the dynamic fracture behavior of the ultra-fine grained steels, and the fracture mechanisms were also investigated. For the ultra-fine grained steels, tensile stress-strain curve was shown to be correlated with the impact curve of load vs. time, and to be related to the dynamic fracture toughness. The steel with large ferrite grains, small ferrite grain colony and martensite was found to have a good combination of strength and toughness. 相似文献