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微合金钢焊接粗晶区晶粒长大的热模拟研究 总被引:2,自引:0,他引:2
采用焊接热模拟方法,研究了不同的焊接热循环参数Tmax和tmax/8对Ti、Nb和N复合加入的两种成分系更的微合金钢昌区奥氏体晶粒尺寸长大的影响。结果表明,奥氏体晶粒尺寸随Tmax增大而增大;并且Tmax恒定时,随着时间延长,长大倾向不岑i低的Ti-Nb-N钢的(BB503)长大倾向严重。tmax/8增大时,两种成分系列钢奥氏体晶粒尺寸变化平缓,但含Ti低的Ti-N钢(1^#)和Ti-Nb-N钢( 相似文献
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采用热模拟方法研究了焊接热循环对Nb-V-Ti微合金钢组织和韧性的影响。研究结果表明,焊接热影响区组织和韧性与t8/5和热循环类型有关。Nb-V-Ti微合金钢母材组织为P+F。经1320℃焊接热循环,t8/5冷速较小时,组织为B+F+P;冷速较大时,组织为B;冷速继续增大,组织为B+M。冷速过大或过小都会降低韧性。经1320℃、1320℃+1320℃和1320℃+780℃三种热循环后,韧性均有较大下降,以1320℃+780℃热循环韧性最低。 相似文献
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微合金钢焊接热影响区奥氏体晶粒长大的研究 总被引:2,自引:0,他引:2
采用焊接热模拟的方法,研究了不同峰温和停留时间条件下,Ti-N和Ti-Nb-N两种成分系列的微合金钢焊接热影响区奥氏体晶粒长大的特点,试验结果表明,微合金钢抗奥氏体晶粒长大的能力,不仅和Ti含量有关,也和Nb含量及N含量有关。 相似文献
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不同成分系列微合金负抗奥氏体晶粒长大能力研究 总被引:3,自引:0,他引:3
研究了Nb-V,Nb-Ti,Nb-V-Ti三种成分系列微合金钢的抗奥氏体晶粒生大能力,以及含氮量对Nb-V-Ti微合金钢抗奥氏体晶粒长大能力的影响。试验结果表明,微合金钢中加入微量钛可大大提高钢抗奥氏体晶粒长大能力,Nb-V-Ti微合金钢中含氮量增多抗奥氏体晶粒长大能力增强,但含氮量过高会影响焊接热影响区韧性。 相似文献
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通过模拟焊接热循环,在GLeeb-1500装置上模拟了v-Ti-N和V-N钢焊接热影响区粗晶区(GC-HAZ)的组织,并用示波冲击法测定了不同△(从800℃到500℃的冷却时间)试样的Akv值、解理裂纹形核功(Ei)和扩展功(Ep)。用光学显微镜、SEM和TEM对这两种钢高温奥氏体的晶粒尺寸、过冷奥氏体转变产物和各△条件下的冲击断口进行了定量分析和观察,探讨了加微量钛对焊接GC-HAZ的组织和韧性的影响。试验结果表明,与V-N钢相比,V-Ti-N钢由于含有适量的钛,使奥氏体晶粒及其转变产物显著细化,并且奥氏体转变产物的形态和分布也得到改善,这使V-Ti-N钢GC-HAZ的韧性显著高于V-N钢。 相似文献
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利用萃取复型和焊接热模拟技术,对0.14C-1.34Mn-0.017Ti-0.023Nb微合金钢及模拟焊接粗晶热影响区中第二相粒子的形态、数量及物相进行了研究。结果表明,母材中第二相粒子形状不规则,Nb的相对含量(Nb/(Nb Ti))在25%~82%之间的粒子平均直径为14.2am,尺寸较大的粒子(~50nm)含Ti较高,呈方形,尺寸较小的粒子中Nb含量较高,呈球形。焊接热循环后,第二相粒子数量显著减小,平均尺寸增大,呈方形。800℃至500℃冷却时间t8/5从16s增加至60s时,粒子中Nb的相对含量为20%~50%,粒子平均尺寸由31.4nm增大至37.2nm,粒子数量由1.95/μm^2减少至1.20/μm^2。但t8/5从60s增至120s时,因冷速慢,析出温度低,粒子平均尺寸减小至26.3nm,粒子数量增加至3.56/μm^2,又重新出现一些含Nb量较高的球形粒子。 相似文献
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采用萃取复型技术,对经受焊接热循环不同阶段的试样进行研究,分析TiN粒子在焊接热循环不同阶段的溶解、粗化及再析出行为。结果表明,在焊接热循环加热过程的低温阶段(1200℃以下),粒子的溶解以粒子的尺寸减小为主要特征,粒子数量变化不大。在焊接热循环加热过程的高温阶段(1200-1350℃),大量小尺寸粒子消失,粒子平均尺寸显著增大。研究发现,TiN粒子的溶解存在很大的滞后效应,在冷却过程的高温阶段(1350-1300℃),粒子仍继续溶解,在冷却过程的低温阶段(1300℃以下),固溶状态的Ti与N结合并沉淀到残留的TiN粒子上,使粒子粗化。在焊接热循环过程中,Ti微合金钢原始奥氏体晶粒长大主要发生在冷却阶段。 相似文献
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This study aims to investigate the influence of Ti addition on microstructure and toughness in the simulated coarse-grained heated-affected zone (CGHAZ) of high-strength low-alloy steels. The steels with low and high Ti content respectively were subjected to 100?kJ/cm heat input welding thermal cycle. The results indicated that the second-phase particles were mainly oxide covered with MnS and fine (Ti,Nb)N precipitate in low-Ti steel, which were modified to the oxide surrounded by TiN and coarse (Ti,Nb)N precipitate in high-Ti steel. Compared with low-Ti steels, the coarser precipitates induced larger austenite grain in CGHAZ of high-Ti steel. Moreover, the wrapping of TiN decreases the ability of inclusion to promote the nucleation of acicular ferrite, resulting in lower fraction of acicular ferrite in CGHAZ of high-Ti steel. Content of martensite-austenite constituent increased in CGHAZ of high-Ti steel. They were all responsible for the degeneration in toughness in CGHAZ of high-Ti steel. 相似文献
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Nb-Ti微合金钢大线能量焊接粗晶区组织和韧性的研究 总被引:1,自引:0,他引:1
利用热模拟技术,研究了两种Nb-Ti微合金钢的粗晶区韧性.通过金相和电镜,观察了焊接热循环后的组织及第二相粒子分布.试验结果表明,在Nb-Ti复合加入时,最佳Ti/N约为2.73.根据该数值计算了不同Ti、N含量下的TiN含量和固溶N含量.试验数据表明,生产大线能量焊接用钢以保持较高的Ti、N含量为佳. 相似文献
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含钛钢奥氏体中第二相析出的热力学分析和实验研究 总被引:1,自引:0,他引:1
基于含钛钢中各析出相之间的相互溶解现象,建立热力学模型,研究了低碳含钛钢中的TiN、TiC、TiS、Ti4c2s2及MnS等第二相在奥氏体中的平衡析出规律,对20CrMnTi钢种成分的计算结果表明:该类含钛钢中的析出相主要为TiCyN1-y、Ti4C2S2及MnS,且钛和硫含量在规格范围内的波动可导致它们析出的次序和数量发生明显的变化,对该钢种的实验研究表明,高温冷却过程中,脱溶析出的细小的沿晶Ti4C2S2等粒子是钢在奥氏体高温塑性恶化的原因之一。 相似文献
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The thermodynamics of TiN precipitation in liquid steel of 430 ferrite stainless steel has been calculated to find out the condition of TiN precipitation during the initial solidification stage. The difference in the solidification structure of 430 ferrite stainless steel has been discussed through comparative tests of vacuum induction furnace melting with different contents of Ti. It has been found that the equiaxed grain proportion can be increased from 20% to 69% as the content of Ti from 0.1% up to 0. 4%. The size of the TiN particles precipitated is 1-3 μm and the number of TiN particles is about (200- 300)/μm^2. It is found that the effect of using TiN to refine the solidification structure has been confirmed under the strict process condition used for 430 ferrite stainless steel. 相似文献
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为了研究硼铬微合金钢的脆性断裂失效机理,以工厂履带拖拉机支重轮的中心轴脆性断裂为研究背景,通过对中心轴断口的观察以及不同位置的组织和晶粒度的对比,得出了硼铬微合金钢的断裂失效机理。利用FactSage和Thermo- Calc软件对TiN夹杂物的析出机理和控制进行理论计算。结果表明,钛合金的不完全溶解和钛、氮元素质量分数的不合理控制,导致大量的大尺寸硬质TiN夹杂物在凝固过程中析出,使得钛元素的加入没有起到很好地细化晶粒的效果,中心区域的铁素体+奥氏体组织的晶粒度过于粗大。大尺寸TiN夹杂物作为裂纹源和心部粗大的晶粒导致了硼铬微合金钢的脆性断裂失效。热力学计算表明,TiN夹杂物在凝固过程中形成,低钛低氮和钛、氮质量分数的合理搭配可以有效推迟TiN夹杂物的析出,降低其尺寸。较小的夹杂物尺寸和细小的晶粒均可以有效增强材料抵抗裂纹扩展的能力。 相似文献
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HRB500E抗震钢筋中钛化物析出热力学分析 总被引:1,自引:0,他引:1
钢液凝固过程中钛化物在液相、固相的存在形态对固相组织的性能有着重要的影响,其第二相析出起到细化晶粒的作用。为分析HRB500E抗震钢筋钢中TiN、TiC、Ti(C,N)析出物的析出规律,对TiN、TiC、Ti(C,N)析出物进行热力学计算。结果表明,TiN、TiC在钢液成分均质状态下难以析出,TiC0.19N0.81在温度为1 843 K时析出;在凝固过程中,由于Ti、N在凝固前沿富集,TiN在凝固过程中具备析出的热力学条件,析出温度为1 745 K;在固相奥氏体中,TiN和TiC粒子具备析出热力学条件,TiC析出温度比TiN的低,铁素体中有TiC的析出。 相似文献
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Heavy thickness steel plates with a good combination of strength,toughness and weldability have been demanded for building of large container ships.High strength steel plates with heavy gauge of EH36,EH40 and EH47 grades were developed by optimizing chemical compositions and TMCP process parameters.Micro alloying elements of Ti and Nb were added to the three steel grades for enhancing the strength and toughness of base plates.The strength of base plates of the EH47 grade was further enhanced with the help of the increased amount of substitutional solid solutes,such as manganese,copper,nickel,or chromium.EH36 steel plates for high heat input over 550 kJ/cm were manufactured by improving thermal stability of TiN particles for better weld heat-affected zone toughness.Thermally stabilized TiN particles effectively suppress grain growth at weld heat-affected zone,leading to better toughness.These steel plates showed excellent mechanical properties of base plates and welded joints. 相似文献
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The Role of Alloy Composition on the Stability of Nitrides in Ti-Microalloyed Steels during Weld Thermal Cycles 总被引:1,自引:0,他引:1
B. Loberg A. Nordgren J. Strid K. E. Easterling 《Metallurgical and Materials Transactions A》1984,15(1):33-41
The effect of weld thermal cycling on titanium nitride stability in a range of normalized Timicroalloyed steels containing various alloying additions of V, Al, and N has been investigated. Nitride dispersions and the chemical analysis of individual particles are studied using transmission electron microscopy and a quantitative 200 kV STEM-EDX-EELS microanalysis system. It is found that whereas the normalized material contains various nitrides of mixed compositions, only nitrides based on TiN survive high energy simulated weld cycles. Grain growth in weld cycled material is highly dependent upon the stability of nitrides during the weld cycle, and this stability depends on the original composition of the nitrides and hence of the steel itself. The presence of aluminum in the particles is particularly detrimental in this respect. The best grain growth control and highest toughness are found in steels based on optimum ratios of Ti/V/N and on low Al levels. The possible way in which the steel’s composition affects particle stability and hence grain growth during weld thermal cycles is discussed. 相似文献
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W. Yan Ph.D. Student Y. Y. Shan K. Yang 《Metallurgical and Materials Transactions A》2006,37(7):2147-2158
Microalloying with various elements, including titanium, coupled with thermomechanically controlled processing, has become
a major technology for the manufacture of high-quality steel plate. In this research, the influence of TiN inclusions on the
impact toughness of low-carbon plate steels microalloyed with titanium, vanadium, and boron was investigated. The three experimental
steels had Ti/N ratios of 2.44, 3.5, and 4.2, and all three had a granular bainite microstructure. However, Charpy V-notch
testing showed that steel A had very high toughness at both room temperature and −20 °C, whereas steels B and C showed very
low toughness at −20 °C and moderate toughness at room temperature. Scanning electron microscope fractography revealed that
coarse TiN inclusions had acted as cleavage fracture initiation sites in steels B and C. The effect of Ti and N levels on
TiN formation and growth is analyzed using alloy thermodynamics. It is shown that not only is the Ti/N ratio important, but
also the product of total Ti and N plays a most important role in TiN formation and growth. It is concluded that the product
of the total Ti and N contents should not be greater than the solubility product of TiN at the solidus temperature to prevent
the precipitation of TiN particles before solidification. Furthermore, the ratio of Ti to N should also be maintained lower
than the stoichiometric ratio of 3.42 to ensure a low coarsening rate for the TiN inclusions during soaking before rolling. 相似文献