终轧温度和轧后冷却对含Nb-V微合金钢性能的影响

通过模拟实验,研究了终轧温度和轧后冷却对含Nb-V微合金性能的影响.适当降低终轧温度,增加冷却速度,降低终冷温度,以控制Nb(CN)、V(CN)析出行为,从而改善钢的性能.     

含铌微合金钢碳氮化物析出行为研究的现状及发展

综述了含铌微合金钢中铌的固溶与析出行为.着重阐述了控轧控冷过程中各工艺参数对含铌微合金钢中铌的碳氮化物析出行为的影响,涉及形变、温度、冷却速率及合金元素等对铌碳氮化物析出的作用;总结了含Nb微合金钢中碳氮化物的研究现状,并展望了其未来的发展.     

含钒钛微合金钢连铸板坯的热塑性模拟研究

含钒钛微合金钢连铸板坯因表面裂纹严重影响铸坯质量,这与其在连铸过程中的热塑性密切相关。以攀钢目前生产的含钒钛微合金钢为研究对象,研究了从熔点到550℃温度范围内热塑性的变化规律。采用数理分析方法,首次建立了含钒钛微合金钢的流变模型。用此模型预测含钒钛微合金钢在连铸条件下的热塑性,并作为改进连铸工艺的依据之一。在研究含钒钛微合金钢连铸板坯的表面裂纹与热塑性的关系时,发现连铸板坯表面横裂纹往往在振痕谷部产生。据此开创性地用高温下的非连续模型热拉伸实验模拟铸坯表面横裂纹的产生过程。结果表明,振痕产生的应力集中降低了含钒钛微合金钢的热塑性。论文把高温时应力集中导致材料热塑性变化称为材料的高温应力集中敏感性,并用高温应力集中敏感参数τ=(RA-RA′)/RA×100％来描述(RA是连续模型断面收缩率;RA′是非连续模型断面收缩率)。根据这一定义。采用数理分析方法定量研究了含钒钛微合金钢从熔点到700℃温度范围内高温应力集中敏感性的变化规律,并建立了高温应力集中敏感性模型。通过此模型,可预测含钒钛微合金钢在连铸过程中的高温应力集中敏感性,并对由流变模型得到的连铸工艺参数进行调整。采用理论计算和实验手段研究了钒钛在钢中的存在状态及其对热塑性和高温应力集中敏感     

脉冲电流对低碳微合金钢力学性能的影响

研究了脉冲电流对一种低碳微合金钢的组织和力学性能的影响，结果表明，脉冲电流处理可以使该钢的晶粒显著细化，从而使其力学性能提高，细化后的组织热稳定性好，在400℃长时间保温不会出现晶粒长大，脉冲电流加热速度快，作用时间短和降低相变势垒的作用是晶粒细化的原因。     

含铌、钒、钛微合金钢连铸坯角部横裂纹研究现状

在微合金钢连铸生产过程中,角部横裂纹一直未得到有效解决,裂纹的存在减少了铸坯热送量,严重影响生产顺行。综述了微合金连铸坯角部横裂纹的形成机理,重点分析了铌、钒、钛等微合金元素对角部横裂纹的影响,分析了防止横裂纹产生的措施,认为消除微合金钢连铸坯角部横裂纹的最有效方法是控制铸坯表层微观组织,使其具有较低的裂纹敏感性,克服连铸弯曲与矫直过程中产生的应力,而不产生裂纹。     

外加微米ZrC颗粒对低碳微合金钢组织及性能的影响

本文研究了ZrC颗粒加入量对低碳微合金钢组织和力学性能的影响。对试验钢进行了各种力学性能的测试,并用金相显微镜和TEM观察了试验钢的微观组织,用SEM观察了ZrC颗粒的分布状态及拉伸断口形貌。结果表明,加入ZrC颗粒后,试验钢的晶粒都得到了一定程度的细化,当加入ZrC颗粒体积含量为1.1%时,晶粒被细化到5.5μm,此时试验钢的抗拉强度、屈服强度、伸长率、冲击韧性和维氏硬度分别达到635MPa、517.5MPa、20.66%、215.0J/cm2和214 Hv5,获得了最佳综合力学性能;添加ZrC颗粒后,试验钢的组织仍为铁素体,拉伸断口仍为韧窝状;轧制态试验钢中ZrC颗粒分布较为均匀。     

厚壁合金钢焊接及热处理技术

宁波禾元化学项目LORU单元中的高温高压蒸汽管道,材质为12Cr1MoVG,壁厚最大达到40mm。焊接性能较差,厚壁管热处理对工艺要求较高。现场施工多为高空作业,焊接条件差。通过分析,选用TIG-R31焊丝和R317焊条进行焊接。根据现场不同规格的管道,设置不同的焊前预热以及焊后热处理条件进行试验,最终确定了合理的焊接工艺及热处理工艺,并成功地应用到工程上,取得了很好的效果。     

海洋大气环境下稀土及铌微合金钢的腐蚀行为研究

为给微合金钢的设计开发理论提供数据支撑,通过显微组织表征、干湿交替循环试验、中性盐雾试验和电化学分析等测试手段研究了稀土微合金钢和铌微合金钢在海洋大气环境中的腐蚀行为,对比分析了其耐腐蚀性能.结果表明:微合金钢的显微组织由铁素体和珠光体组成,并且铌微合金化有助于细化晶粒并能阻碍珠光体组织的形成.在腐蚀初期锈层的主要成分...     

微合金钢的研究现状及发展趋势

微合金钢是近年来迅速发展起来的具有高性能的钢材品种之一,被广泛用于各个工业部门,是现代钢铁工业中的主力产品.简要介绍了微合金钢的属性,综述了国外微合金钢的研究现状,着重讨论了国内微合金钢的研究现状,总结了宝钢、鞍钢、攀钢和国内科研机构微合金钢的发展现状,并论述了国内外微合金钢未来的发展趋势.     

组合焊缝对中碳合金钢焊接裂纹的影响

采用Ｙ形坡口裂纹试验和显微分析方法，研究了三种不同的组织焊缝对中碳合金钢焊接裂纹的影响，结果表明，底层焊道熔俣区裂纹为氢致延迟裂纹；底层焊条的合金系统对该裂纹的生成有一定的影响，底层焊道熔合区的马氏体和氢的富集以及大的拘束应力，是裂纹生成的必要和充分条件；提出了防止裂纹产生的用工艺。     

Influence of RPC Parameters on the Precipitation of Nb in Microalloyed Steel

Thermo-simulation test, metallographic analysis, measurement of hardness, TEM(including diffraction contrast technique and nano-beam anylasis)along with calculating software of Metlab, etc. were used to study the influence of RPC parameters(relaxation time, aging time)on the precipitation of Nb in microalloyed steel. Following work was undertaken in this study:Strain-induced precipitation in Nb-bearing multi-microalloyed steel was monitered and analyzed. The interaction between dislocation evolution and precipitates in deformed austenite was directly observed(an Fe-Ni-Nb alloy was employed to simulate austenite in steel). The(a low carbon microalloyed steel only by Nb was adopted)effect of relaxation of deformed austenite on aging behavior occurring in bainite was investigated. Finally, the thermal stability and variation of composition of carbonitride precipitates during dissolving process in Nb-Ti microalloyed steel were alsodetected. These results indicate:(1)During the stress relaxation, the process of precipitation happened in deformed austenite of multi-microalloyed steel can be divided into three stages, i. e. nucleation, growth and coarsening. In the final stage of relaxation, Mo atoms would enter the lattice of(Nb,Ti)(C,N)precipitates and its concentration in the precipitates increases with the relaxation time.(2)In the earlier stage of relaxation, the dislocations in deformed austenite demonstrate twisted and distribute randomly. The precipitates have the tendency to occur along those dispersed dislocations. The dilocation cells would form gradually with the relaxing time prolonged and would become more stable by the subsequent precipitates formed on them in the later relaxation period. The paralleled dislocations in dislocation cells exhibit the same Burgers vector. The dislocations get rid of pinning by the bypassing mechanism.(3)When the samples are reheated to hold isothermally at 525℃,which are relaxed for different time in deformed austenite followed by accelerated cooling, their microstructures evolve very slowly with the aging time but two hardness peaks can be found one each hardness-time curves. The position of hardness peaks nearly raimains unchanged while their height varies obviously with the relaxation time. In no relaxtion samples, only one hardness peak could be observed. During the process of aging at 525℃, The growth and coarsening of as-existed strain-induced precipitates formed in deformed austenite contribute to formation of the first hardness peaks. While the second hardness peaks result from the further precipitates which nucleate in a phase after γ→α transformation(after aging for about 10 hours).(4)It was found that the precipitates formed during solidification are monophase(Ti,Nb)(C.N)rather than TiN enclosed with NbC. With addition of Ti to the steel, the thermal stability of the carbonitrides would enhance remarkably.     

铌硼微合金钢高温应变诱导析出行为

用应力弛豫方法研究了超低碳铌硼微合金钢在８００℃，８５０℃、９００℃和９５０℃下，经过２０％预变形目的等温应变诱导析出行为。样品的透射电镜观察表明：应变诱导析出只在位错线上形核并阻碍位错运动，而位错一旦摆脱钉扎，这种运动位错可以是样品中进一步析出的优先形核位置，从而导致析出分阶段进行。     

贝氏体型冷作强化非调质钢的氢致延迟断裂行为

采用电化学充氢和慢拉伸应变速率实验(SSRT)研究了形变和时效处理对一种低碳-Mn-B-Ti系贝氏体型冷作强化非调质钢氢致延迟断裂行为的影响规律。结果表明,无论热轧态还是拉拔态试样,充氢后试样的耐延迟断裂性能显著降低。在拉拔变形初期,减面率γ<20%时,耐延迟断裂性能降低的幅度较大;而随着拉拔量的继续增加,耐延迟断裂性能降低的趋势变缓。实验料拉拔后进行时效处理有助于其耐延迟断裂性能的改善,当时效温度提高到200℃以上时这种改善作用比较明显。     

Materials Behavior in Laser Welding of Hardmetals to Steel

Tool manufacturing industry faces the problem of permanently joining hardmetals to steel holders with high shear strength. The mostly used welding process still is brazing. However, brazed joints have poor lifetimes, mostly when high temperatures are achieved and often break in operation. In a previous study about the ability of CO₂ and Nd:YAG lasers to weld hardmetals to steels, it was found that Nd:YAG lasers, working in continuous wave mode, could be used especially for welding hardmetals with Co content around 12%. This article discusses the materials behavior under laser radiation and analyzes the microstructural features observed.     

含Nb微合金钢应变诱导析出的研究现状

简述了微合金钢中微量元素Nb的主要作用,回顾了应变诱导析出的研究方法及优缺点,阐明了变形奥氏体应变诱导析出相的种类,晶体结构,析出相的形成顺序、形貌和分布,分析了影响析出动力学的主要因素并简要介绍了应变诱导析出动力学模型的最新发展.     

Static Recrystallization and Precipitation Behavior of a Weathering Steel Microalloyed with Vanadium

The static recrystallization （SRX） and precipitation behavior of a weathering steel microalloyed with vanadium were investigated through double-pass compression tests under controfled conditions using the MMS-300 thermal-mechanical simulator. The deformation temperatures ranged from 800 °C to 1000 °C, and the inter- pass time from 1 s to 500 s. The simulation results showed that SRX occurred after 5-10 s at the first compression deformation. The softening fraction of SRX was found to increase with increasing the deformation temperature and the pre-strain. However, the softening fraction scarcely changed during the process of strain-induced precipitation. In addition, the kinetics of SRX was described by the Avrami equation, and the Avrami exponent appeared to be closely associated with the deformation temperature. The microstructure evolution was investigated at the initiation and completion of recrystallization. The amount and distribution of the precipitates were analyzed. The relationship between the driving force of SRX and the pinning force of precipitation was discussed. Besides, the recrystallization inhibition was detected at the early stage of precipitation, and the pinning forces were found to be of a magnitude comparable to the driving force. Moreover, the pinning forces were found to increase with the degree of precipitation and reach a peak at the intermediate stage of precipitation, and finally reduce as the particles coarsened.     

微合金钢回温变形时的组织转变和铁素体动态再结晶行为

采用GLEEBLE 3800热模拟机进行回温变形热压缩实验,研究回温温度对微合金钢组织转变和铁素体动态再结晶行为的影响。利用金相显微镜、扫描电镜、透射电镜和背散射电子衍射观察实验钢的微观组织和晶粒取向,并对形变时的应力-应变曲线进行分析。结果表明:实验钢回温变形可获得超细晶组织,晶粒平均等效直径约2μm;在回温过程中变形发生动态回复形成亚晶组织,峰值温度变形发生铁素体动态再结晶形成超细晶粒;动态再结晶机制包括晶界迁移和亚晶的转动生长,回温到700℃和750℃时以前者为主,再结晶不充分,保留了条带状变形铁素体,800℃变形时,两者共同作用,形成均匀的等轴状超细晶组织;通过线性回归计算得到实验钢峰值温度变形时铁素体动态再结晶激活能Qd=250.18kJ/mol。     

Ti-Nb微合金钢焊接粗晶热影响区组织及韧性

利用碳萃取复型技术研究了Ti-Nb微合金钢及其模拟粗晶区(CGHAZ)中的第二相粒子,并利用OM、TEM及系列冲击试验对Ti-Nb微合金钢焊接粗晶区的组织及韧性进行了研究.研究结果表明,Ti-Nb微合金钢中含有大量的、尺寸细小的TixNb1-x(CyN1-y)粒子,粒子中Nb的相对含量在0.25～0.82之间,形状接近球形.这些粒子具有很高的稳定性,在焊接过程中这些粒子能有效地阻止奥氏体晶粒长大、抑制粗大贝氏体的形成、促进针状铁素体析出及M-A组元的分解,从而显著善低合金高强钢焊接粗晶热影响区的韧性,t8/5越大,这种改善作用越明显.     

焊接对304SS钢腐蚀行为的影响规律

采用304SS制作水浴式汽化器时需对304SS进行焊接加工,但此步骤会影响其耐蚀性能,并且距离焊点不同的位置,焊接对材料的影响不同。为了进一步确定焊接对304SS腐蚀影响规律,采用电化学阻抗和电化学噪声等技术研究了304SS钢的大管径盘管与小管径插管的承插焊接对其耐蚀性能的影响规律。结果表明:较高的焊接热可引起304SS钢中的γ相向α相的转变,而适度的(热处理)温度则可提高304SS钢中γ相的相对含量;在承插过程的形变应力和焊接高温热的共同作用下,304SS钢的初期点蚀作用增强,盘管的耐蚀性能按紧邻焊接点区域、未热处理区域、次邻焊接点区域的顺序依次增大,而插管的耐蚀性能按紧邻焊接点区域、次邻焊接点区域、未热处理区域的顺序依次升高。