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低碳低合金钢焊缝金属的显微组织及其影响因素 总被引:8,自引:0,他引:8
低碳低合金钢焊缝金属的显微组织基本上包括先共析铁素体、针状铁素体、侧板条铁体、少量的粒状贝氏体和马氏体。分析了这些组织的形成条件及特点,焊缝金属化学成分和冷却速度是影响焊缝金属组织的主要因素,阐述了各种组织的形核位置。低碳低合金钢焊缝金属最理想的组织是获得大于65%的针状铁素体,其平均板条尺寸约为1μm。 相似文献
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电弧增材制造是成形高性能HSLA钢构件的重要新方法。为了明晰HSLA钢在电弧增材制造时的组织演变行为,研究了构件在堆积成形时的温度场、热循环、热影响区分区及其组织转变。结果表明,电弧增材制造过程中,HSLA钢堆积金属包含凝固区与热影响区,热影响区可分为粗晶区、正火区和回火区。凝固区在热循环作用下先后转变为粗晶区、正火区,最终成为回火区;同时,堆积金属中的残留铁素体晶核、夹杂物附近的高密度位错、铁素体感生形核、第二相质点钉扎晶界和连续动态再结晶共同促进组织细化,使粗大的柱状晶、块状铁素体、侧板条铁素体以及少量针状铁素体、珠光体演变为细小的等轴铁素体和珠光体,有利于提高构件强韧性并抑制力学性能各向异性。构件垂直与水平抗拉强度分别为519.6、520.8 MPa,-20 ℃冲击功分别为124.7、122.1 J。 相似文献
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据《制铁研究》第327号(1987)报道,新日铁中央研究本部的大北茂等研制了一种利用 Ti 的氧化物提高 HSLA 钢 HAZ 韧性的新工艺。过去,一般认为氧化物对钢板材质有害。但研究表明,在某一淬透性范围内,Ti 氧化物可以作为针状铁素体的形核点,有利于获得微细的显微组织。特别是在焊缝金属中,Ti 系氧化物的存在对生成针状铁素体至关重 相似文献
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针状铁素体是一种具有大角度晶界、高位错密度的板条状中温转变组织,该组织能有效细化晶粒并具有良好的强韧性匹配.因此,通常在低合金高强度钢焊缝和粗晶区中,利用细小的夹杂物来诱导针状铁素体形成,形成有效晶粒尺寸细小的针状铁素体联锁组织或者针状铁素体和贝氏体的复合组织,使其具有良好的韧性.然而,相关研究对针状铁素体组织的形成机理和控制原理的解释并不十分清楚,对于针状铁素体的定义和理解也存在差异.总结了针状铁素体的本质、相变、形核、形态、晶体学取向关系、长大行为、细化机理和力学性能等方面的特征,归纳了奥氏体晶粒尺寸、转变温度、冷却速度、夹杂物类型和尺寸等对针状铁素体形成的影响,提出了针状铁素体组织形态和转变机理方面几个仍需深入研究的问题和方向. 相似文献
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冷却条件对42CrMo钢的组织和性能的影响 总被引:1,自引:0,他引:1
研究了冷却条件对42CrMo钢的组织和性能的影响。研究表明:随着冷却速度的增加,42CrMo钢组织变化依次是多边形铁素体组织、针状铁素体组织、上贝氏体和板条马氏体的混合组织。其中,针状铁素体使钢的组织细化、韧性提高。热温度过高,冷却速度快会形成网状铁素体组织,在高温区冷却速度慢会形成块状铁素体组织。这两种组织使钢的力学机械性能降低。 相似文献
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为了研究EH36海洋平台用钢焊接工艺,对100 mm厚的EH36海洋平台大线能量用钢进行了大线能量埋弧焊焊接试验。焊后对焊接接头进行了综合性能测试和微观组织分析。结果表明,焊缝表面及中心部位组织由大量针状铁素体、少量先共析铁素体和少量M-A组元组成,焊缝接头具有良好的韧性。接头硬度测试表明,EH36大线能量用钢在100 k J/cm热输入条件下,焊缝及热影响区具备较好的硬度,满足热输入条件下焊接施工条件。 相似文献
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对比研究成分为20MnSiV和16MnVNb的HRB400钢筋的屈服行为,在同一轧制工艺条件下,与含钒钢筋相比,含铌钢筋应力-应变曲线没有明显的屈服平台。对试验钢的化学成分、显微硬度进行测试分析,利用光学显微镜、扫描电镜和透射电镜对试验钢的微观组织进行观察。结果表明,20MnSiV试验钢组织主要为铁素体+珠光体组织,16MnVNb的组织为等轴状铁素体+珠光体+针状铁素体,其中针状铁素体周围珠光体退化明显。针状铁素体的显微硬度介于珠光体与铁素体之间,其内部存在高密度位错。针状铁素体组织的大量存在是导致含铌HRB400钢筋无屈服平台的原因。 相似文献
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Submerged arc welding(SAW)and gas metal arc welding(GMAW)experiments of Nb-bearing X80 steel were conducted with high-toughness wires.The inclusions in weld metals were analyzed in terms of their types and sizes.In GMAW,the inclusions are primarily Ti,Ca,Si,Al,and Mg compounds with no Nb and are generally less than 0.8 pm in size,whereas,in SAW weld,the inclusions are larger,mostly approximately 2-5 μm in size,and are cored with Ca and Ti,exhibiting obvious oxidation metallurgical features.The SAW joint was hot-deformed,and Nb-bearing nano precipitates were newly found in the weld metal through transmission electron microscopy,and Nb-free core-shell inclusion was found through scanning electron microscopy.The inclusions and precipitates were dispersed in or on the boundaries of acicular ferrite,contributing to acicular ferrite nucleation and grain refinement. 相似文献
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Lower acicular ferrite 总被引:3,自引:0,他引:3
A. A. B. Sugden H. K. D. H. Bhadeshia 《Metallurgical and Materials Transactions A》1989,20(9):1811-1818
An experiment has been designed to confirm that the mechanism of growth of acicular ferrite in steel welds is similar to that
of bainite in ordinary steels. On the hypothesis that the growth mechanisms are identical, it was expected that if the carbon
concentration of a weld is increased sufficiently, then for similar welding conditions, the microstructure should undergo
a transition from acicular ferrite tolower acicular ferrite, in which the plates of acicular ferrite should contain cementite particles of the sort normally associated
with lower bainite in wrought steels. An experimental weld of unusually high carbon concentration was prepared, and metallography
confirmed the existence of lower acicular ferrite, supporting the conclusion that acicular ferrite is simply an intragranularly
nucleated bainite. 相似文献
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Inrecentyears ,thedemandofhigherweldingqualityisincreasingwiththedevelopmentofhighstrengthsteel.Thestrengthandtoughnessofweldmetalsareimportantforuseperformanceofweldingstructure ,especiallyforlowalloyhighstrengthsteelwhosetensilestrengthσb ≥ 10 0 0MPa ,and… 相似文献
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��С����������� 《钢铁研究学报》2013,25(9):52-57
Electro-slag welding with heat input of 530kJ/cm was applied to 60mm thick shipbuilding plate EH40, and microstructure and mechanical properties of the weld joint were characterized. Different regions such as heat affected zone, fusion zone, weld metal and base metal are found across the weld joint by microstructure analysis. A narrow coarse grain heat affected zone consisting of acicular ferrite, polygonal ferrite and grain boundary ferrite is found, width of which is less than 1mm. Acicular ferrite (?? 10??m) and grain boundary ferrite is observed at weld metal, while fusion zone have a complex structure of acicular ferrite, grain boundary ferrite and ferrite side plate. Mechanical property tests show that the absorbed energy of WM, FL and CGHAZ at -20?? during Charpy impact test is more than 60J, no evident softening phenomenon occurred at heat affected zone, and other properties met the requirement. 相似文献
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Inclusion phases and the nucleation of acicular ferrite in submerged arc welds in high strength low alloy steels 总被引:1,自引:0,他引:1
J. M. Dowling J. M. Corbett H. W. Kerr 《Metallurgical and Materials Transactions A》1986,17(9):1611-1623
Series of submerged arc welds of HSLA steel made with three different fluxes and metallic additions of Ti, Mo, and Cr have
been examined to study the inclusions and their role in the nucleation of acicular ferrite. Inclusion phases and compositions
have been analyzed by electron diffraction and X-ray microanalysis. These analyses have shown that the inclusions contained
many different compounds, the proportions of each depending upon both the flux and metallic additions. Six inclusion phases
have been identified: galaxite (Al2O3 ⋅ MnO), a titanium-rich compound (probably TiO), a copper sulfide, a manganese sulfide, a silica, and an aluminum-rich phase.
No correlation was found between the amount of acicular ferrite in the weld metal and either average inclusion composition
or individual inclusion phases. No epitaxial relationships between inclusions and adjacent ferrite grains could be identified.
It has been concluded that inclusions nucleate acicular ferrite by acting as inert substrates according to the classical theory
of heterogeneous nucleation. Because most inclusions are multi-phase and are touched by several ferrite grains, it has also
been concluded that each inclusion can nucleate several ferrite grains, due to local regions of high surface energy on the
inclusion. 相似文献
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Yongjoon Kang Gitae Park Seonghoon Jeong Changhee Lee 《Metallurgical and Materials Transactions A》2018,49(1):177-186
A large fraction of reheated weld metal is formed during multi-pass welding, which significantly affects the mechanical properties (especially toughness) of welded structures. In this study, the low-temperature toughness of the simulated reheated zone in multi-pass weld metal was evaluated and compared to that of the as-deposited zone using microstructural analyses. Two kinds of high-strength steel welds with different hardenabilities were produced by single-pass, bead-in-groove welding, and both welds were thermally cycled to peak temperatures above Ac3 using a Gleeble simulator. When the weld metals were reheated, their toughness deteriorated in response to the increase in the fraction of detrimental microstructural components, i.e., grain boundary ferrite and coalesced bainite in the weld metals with low and high hardenabilities, respectively. In addition, toughness deterioration occurred in conjunction with an increase in the effective grain size, which was attributed to the decrease in nucleation probability of acicular ferrite; the main cause for this decrease changed depending on the hardenability of the weld metal. 相似文献
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采用CO2焊接方法焊接X100管线钢,分析了不同焊接工艺下焊接接头组织和性能的变化特征。随着焊接热输入的增加,焊接接头的屈服强度和抗拉强度降低,焊缝和热影响区处的冲击吸收功呈现先增大后减小的变化趋势,而焊缝组织均以针状铁素体(AF)为主。焊接热输入为1.17 kJ/mm时,粗晶区的显微组织主要是贝氏体铁素体(BF),强韧匹配性最为优异;当热输入增加至1.91 kJ/mm时,粗晶区的组织除了BF外,还出现了粒状贝氏体(GB),强韧水平明显降低。综合考虑,可将1.17 kJ/mm作为X100管线钢CO2焊接时的最佳热输入。 相似文献
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《钢铁研究学报(英文版)》2016,(9):955-962
E32 grade corrosion resistant steel was welded with welding wires with three different S contents.The mi-crostructure,mechanical properties,inclusions,and corrosion behavior of welded joint were investigated.The joint coupon corrosion test and potentiodynamic polarization test were carried out under the simulated corrosion environ-ment of the inner bottom plates of cargo oil tanks.The pitting initiation and propagation mechanism of the weld metal were studied by scanning electron microscopy and infinite focus.The results indicated that the microstructures of three kinds of weld metals are all composed of acicular ferrite,ferrite side-plate and proeutectoid ferrite.The micro-structure of heat-affected zone is composed predominantly of bainite.Joint welded with low S filler wire has good me-chanical properties.S can decrease free corrosion potential and increase the corrosion tendency.The pitting initiation is oxide inclusion or sulfide-oxide inclusion complex.S can induce the formation of occluded area and promote the corrosion propagation.The chemical compositions of weld metal is similar to base metal,which can limit the galvanic corrosion between weld metal and base metal,and avoid formation of corrosion step. 相似文献