微合金化元素对离心铸造炉管焊接接头组织和性能影响

针对添加Ti,W等微合金化元素的离心铸造炉管焊接接头,研究了微合金元素对焊接接头组织和力学性能影响规律及作用机理.结果表明.在1 050℃、14~25 MPa条件下,使用Ti和W元素微合金化的25Cr35NiNb和35Cr45NiNb炉管焊接接头高温性能显著高于未微合金化焊接接头.微合金元素Ti显著影响炉管焊接接头组织,Ti元素含量高的焊接接头原始焊态组织中含NbTiC,经过高温时效后,组织中含铌相主要为NbTiC,在蠕变空洞周围局部转变为G相（Ni16Nb6Si7）;Ti元素含量低的焊接接头原始焊态组织中含NbTiC和NbC,经过高温时效后全部转变为G相.微合金元素W主要通过固溶强化的方式,提高炉管焊接接头的高温性能.     

微合金元素对Q345E棒材低温韧性的影响

在未控轧控冷的轧制工艺条件下,研究了Nb/V复合微合金化、Nb微合金化、V微合金化对Q345E棒材热轧态-40℃低温韧性的影响.结果表明,Nb/V复合微合金化钢和Nb微合金化钢强度高于V微合金化钢,V微合金化钢-40℃的低温韧性满足标准要求,Nb/V复合微合金化钢和Nb微合金化钢均不能满足标准要求.在未控轧控冷的工艺条件下,采用V微合金化Q345E钢是可行的.     

Nb-Ti微合金化钢板的工业试制

用热模拟试验方法研究了Nb-Ti微合金钢的再结晶规律，在此基础上制定了合理的炼钢、控轧控冷工艺，进行Nb-Ti微合金钢的工业试制。分析了Nb、Ti等微合金元素对钢材组织、性能的影响。研究结果表明：对Q345钢进行Nb、Ti微合金处理并采用合理的控轧控冷工艺后，板材铁素体晶粒度提高1．5～2．0级，力学性能达到了Q390D的要求。     

热循环对高铌管线钢焊接热影响区冲击韧性的影响

采用Gleeble-3500型热模拟试验机,研究了焊接热循环对Mn-Mo-Nb和高铌 HTP X80管线钢焊接热影响区(HAZ)冲击韧性的影响.结果表明,随焊接热输入量的增加,两种X80管线钢粗晶HAZ的冲击韧性均降低,但在相同的焊接热输入条件下,高Nb钢粗晶HAZ的冲击韧性均高于Mn-Mo-Nb管线钢.其原因是高Nb钢中由于未溶Nb(CN)状的存在,抑制奥氏体晶粒长大,在高的线能量条件下,能够保证奥氏体晶粒的细小均匀.     

Nb元素对低合金耐磨钢组织性能的影响

对含Nb和不含Nb两种成分低合金耐磨钢板NM400热轧和热处理态的组织性能进行了研究,并对比分析了微量Nb元素对其组织性能的影响规律。研究结果表明:在低合金耐磨钢中添加质量分数为0.02%的Nb,在相同的控轧控冷和离线热处理工艺条件下,钢板强度和硬度增加,低温冲击韧性提高。在相同的工艺条件下,微量Nb元素的添加对钢板组织中原始奥氏体晶粒的细化是其低温韧性提高和硬度增加的主要原因。     

Ti-Nb微合金化高强钢的焊接接头组织和性能

采用混合气体(80%Ar+20%CO2)保护焊,对一种Ti-Nb微合金化控轧控冷高强钢板进行了焊接强度实验研究。通过微观组织特征分析,阐述了焊接接头热影响区(HAZ)的软化行为,综合分析了回火态HAZ的脆化机理。结果表明,随焊接热输入增加,粗晶热影响区(CGHAZ)晶粒长大,内部析出相粒子发生回溶现象,接头强度降低;焊接接头回火态强度有所提高,但随回火温度上升,CGHAZ的冲击韧性严重降低,其原因主要与原始组织遗传及碳化物沿晶界析出有关。     

长期热暴露对304H耐热钢焊接接头组织和硬度的影响

使用Inconel 625合金焊丝对超(超)临界电站锅炉高温部件用304H奥氏体耐热钢进行焊接,对焊态焊接接头在650℃下进行5000 h的热暴露,研究了焊接接头组织和硬度随热暴露时间的演化规律。结果表明:焊后焊缝中Mo、Ti、Nb元素在枝晶间偏析,熔合线处未发生外延式生长,焊缝金属和热影响区(HAZ)的主要合金元素含量在熔合线处的浓度梯度明显。热影响区晶粒发生长大;经过3000 h热暴露后热影响区硬度达到母材的水平;随着热暴露时间的延长,母材和焊接接头均发生硬化,焊接接头微观组织无明显变化,组织稳定性较好。     

控轧微合金钢显微组织的选择

含碳量低于0.1％并加入微量Nb、Ti、V等合金元素的微合金钢,经过控制轧制,赋予优良的强韧性。本文分析了控制轧制工艺及微合金化对钢显微组织的影响,指出:必须从控制显微组织的角度,优化钢的微合金化及选择最佳的控制轧制工艺,控制轧后的冷却速度,方能达到提高钢性能的预期效果。     

微合金化在正火态管线用无缝钢管中的应用

研究了微合金元素Nb、V、Ti在正火态管线用无缝钢管成分体系中的不同作用及其机理,并分析了C、N等元素对微合金化效果的影响。结果表明:Nb、V、Ti在正火态管线用无缝钢管成分体系中,可有效细化晶粒,并产生析出强化效果,从而提高钢的强韧性;提高氮元素含量可有效提高V的析出强化和细晶强化效果;降低碳含量可有效提高冲击韧性,但在碳当量同等的情况下,会降低强度。     

低碳微合金Ti-Nb可焊钢中的N及其第二相粒子

研究了系列低碳微合金Ti-Nb可焊钢中的N含量对模拟焊接热影响区(HAZ)高温奥氏体晶粒尺寸和冲击韧度的影响及其第二相粒子的作用.对试样进行了大热输入焊接热模拟,测定了高温奥氏体晶粒尺寸和焊后试样中的冲击韧度值,并用透射电子显微镜萃取复型法观察了典型试样中第二相粒子(Ti,Nb)N的形态及分布特征.结果表明,钢中Ti、N含量及第二相粒子的尺寸和数目与高温奥氏体晶粒尺寸及冲击韧度值具有很好的对应关系;钢中的N由于生成了细小弥散分布的第二相粒子(Ti,Nb)N而细化了高温奥氏体晶粒,改善了焊后韧性.低碳微合金Ti-Nb钢中适宜的含氮量有一个范围.     

Analysis on Internal Oxidation Technology of Al in Cu—Al Pre--Alloyed Powders

通过在铁素体和奥氏体不锈钢中添加适量Cu，经过特殊的抗菌处理，使不锈钢具有了优良的抗菌特性．探索了含Cu不锈钢经过抗菌处理后抗菌析出相的分布和形貌，抗菌检测结果表明，含有一定量Cu的铁素体和奥氏体不锈钢显示出了很强的广谱抗菌性能．在生物电镜下观察到抗菌钢表面细菌形态的改变与组织液溢出现象．     

Evaluation of Microstructure and Mechanical Properties in Dissimilar Austenitic/Super Duplex Stainless Steel Joint

To study the effect of chemical composition on microstructural features and mechanical properties of dissimilar joints between super duplex and austenitic stainless steels, welding was attempted by gas tungsten arc welding process with a super duplex (ER2594) and an austenitic (ER309LMo) stainless steel filler metal. While the austenitic weld metal had vermicular delta ferrite within austenitic matrix, super duplex stainless steel was mainly comprised of allotriomorphic grain boundary and Widmanstätten side plate austenite morphologies in the ferrite matrix. Also the heat-affected zone of austenitic base metal comprised of large austenite grains with little amounts of ferrite, whereas a coarse-grained ferritic region was observed in the heat-affected zone of super duplex base metal. Although both welded joints showed acceptable mechanical properties, the hardness and impact strength of the weld metal produced using super duplex filler metal were found to be better than that obtained by austenitic filler metal.     

THE EFFECT OF W ON THE REPASSIVATION BEHAVIOR OF Ni-ADDED STAINLESS STEELS

The effect of W on the repassivation behavior of Ni-added stainless steels was investigated with respect to the repassivation rate and the SCC susceptibility. It was found that more stable passive film was formed on the W-modified stainless steels than that of steels without W-modification, and the repassivation rate was faster for W-modified stainless steels in acidic chloride solution （0.5M H2SO4＋3.5% Cl^-）. In neutral chloride solution （1M MgCl2）, there were no significant differences on both passivation properties and the repassivation rates for duplex stainless steels, while W-modified austenite stainless steel showed faster repassivation rate. The SCC tests verified that W-modified Ni-added stainless steels exhibited better SCC resistance than steels without W in chloride solution. Moreover, W-modification in higher Ni-added stainless steels exhibited more remarkable SCC resistance than steels with lower Ni content in chloride solution.     

节约型双相不锈钢2101高温变形过程中微观组织演化

采用电子背散射衍射技术(EBSD)和TEM研究了节约型双相不锈钢2101在温度为1000℃和应变速率为5 s~(-1)的高温变形过程中的微观组织演化.结果表明,铁素体和奥氏体都发生以小角度晶界不断向大角度晶界转变为特征的连续动态再结晶(CDRX).固溶退火后双相不锈钢奥氏体内出现大量退火孪晶.随变形量增加,奥氏体中具有∑3位向关系的晶界逐渐消失.高温变形过程中双相微观组织演化机制的耦合作用共同决定了流变曲线特征.     

自蔓延—离心法制备的不锈钢内衬复合钢管的力学性能

研究了自蔓延－离心法制备的不锈钢内衬（Ｃｒ１３－１４,Ｎｉ１４－１６）复合钢管不锈钢层的力学性能及热膨胀性能。用扫描电研究了拉伸试样的断口形貌,用透射电镜研究了不锈钢层的组织结构。研究表明,不锈钢内衬与基体碳钢之间热膨胀系数相差较大。不锈钢内衬主要由柱状晶组成,柱状晶为奥氏体,柱状晶间有一薄层铁素体,铁素体区有ＡｌＮｉ金属间化合物析出相,在奥氏体和铁素体有相界有α相析出。     

固溶处理对2205双相不锈钢FCAW接头组织及力学性能的影响

利用气体保护药芯焊丝焊接2205双相不锈钢, 并对焊接接头进行固溶处理。采用金相显微镜、扫描电子显微镜和能谱仪对焊接接头的显微组织和断口形貌进行了观察与分析,并测试了焊接接头的冲击韧性和显微硬度。结果表明,未经处理的焊接接头熔合区较宽,主要为基体铁素体组织,并且晶粒粗大。热影响区的铁素体和奥氏体边界有少量析出相χ相,铁素体内部有颗粒物析出;焊缝区铁素体内部有σ相和γ2相析出。1 050 ℃固溶处理后焊接接头析出相和颗粒物消失,奥氏体组织含量提高,冲击断口等轴韧窝增多,韧性增加,硬度值降低。     

Phase Transformations of an Fe-0.85 C-17.9 Mn-7.1 Al Austenitic Steel After Quenching and Annealing

Low-density Mn-Al steels could potentially be substitutes for commercial Ni-Cr stainless steels. However, the development of the Mn-Al stainless steels requires knowledge of the phase transformations that occur during the steel making processes. Phase transformations of an Fe-0.85 C-17.9 Mn-7.1 Al (wt.%) austenitic steel, which include spinodal decomposition, precipitation transformations, and cellular transformations, have been studied after quenching and annealing. The results show that spinodal decomposition occurs prior to the precipitation transformation in the steel after quenching and annealing at temperatures below 1023 K and that coherent fine particles of L1₂-type carbide precipitate homogeneously in the austenite. The cellular transformation occurs during the transformation of high-temperature austenite into lamellae of austenite, ferrite, and kappa carbide at temperatures below 1048 K. During annealing at temperatures below 923 K, the austenite decomposes into lamellar austenite, ferrite, κ-carbide, and M₂₃C₆ carbide grains for another cellular transformation. Last, when annealing at temperatures below 873 K, lamellae of ferrite and κ-carbide appear in the austenite.     

MICROSTRUCTURE EVOLUTION OF HYPEREUTECTOID STEELS DURING WARM DEFORMATION I. Formation of Equiaxial Ferrite and Effects of Al

利用Gleeble 1500热模拟试验机进行单轴热压缩实验, 结合SEM, TEM和EBSD等方法研究了过共析钢温变形过程中的组织演变规律, 重点讨论了铁素体的等轴化演变过程, 同时考察了合金元素Al的影响. 结果表明: 过共析钢温变形经历片层渗碳体的熔断球化、铁素体的等轴化以及渗碳体的溶解再析出等过程. 温变形初期, 片层状渗碳体缺陷处局部熔断的同时其近邻铁素体内产生大量位错, 并通过动态回复过程形成亚晶; 继续变形过程中, 由于渗碳体粒子钉扎, 亚晶发生转动, 导致大角度晶界的形成, 即铁素体通过连续动态再结晶过程实现等轴化.Al的加入细化了铁素体晶粒尺寸, 提高了等轴状铁素体晶粒大角度晶界的比例.     

Detailed Microstructural Characterization and Restoration Mechanisms of Duplex and Superduplex Stainless Steel Friction-Stir-Welded Joints

Duplex stainless steels are successfully used in a wide variety of applications in areas such as the food industry, petrochemical installations, and sea water desalination plants, where high corrosion resistance and high mechanical strength are required. However, during fusion welding operations, there can be changes to the favorable microstructure of these materials that compromise their performance. Friction stir welding with a non-consumable pin enables welded joints to be obtained in the solid state, which avoids typical problems associated with solidification of the molten pool, such as segregation of alloying elements and the formation of solidification and liquefaction cracks. In the case of superduplex stainless steels, use of the technique can avoid unbalanced proportions of ferrite and austenite, formation of deleterious second phases, or growth of ferritic grains in the heat-affected zone. Consolidated joints with full penetration were obtained for 6-mm-thick plates of UNS S32101 and S32205 duplex stainless steels, and S32750 and S32760 superduplex steels. The welding heat cycles employed avoided the conditions required for formation of deleterious phases, except in the case of the welded joint of the S32760 steel, where SEM images indicated the formation of secondary phases, as corroborated by decreased mechanical performance. Analysis using EBSD and transmission electron microscopy revealed continuous dynamic recrystallization by the formation of cellular arrays of dislocations in the ferrite and discontinuous dynamic recrystallization in the austenite. Microtexture evaluation indicated the presence of fibers typical of shear in the thermomechanically affected zone. These fibers were not obviously present in the stir zone, probably due to the intensity of microstructural reformulation to which this region was subjected.     

UNS S32304双相不锈钢等离子弧焊接头的组织及其耐点蚀性能

采用恒电位临界点蚀温度(CPT)法,利用OM,SEM,EDX和恒电位极化技术等研究了等离子弧焊接对双相不锈钢UNSS32304焊接接头微观组织及其耐点蚀性能的影响.结果表明,焊接接头热影响区和熔合区微观组织较母材相比发生了显著变化,两相比例严重失衡,铁素体所占比例均大于70%;两区域微观组织形态发生明显变化.且在铁素体晶粒内及两相相界处析出大量氮化物;焊接接头的耐点蚀性能明显下降,点蚀优先发生在高温热影响区所在的铁素体晶粒内.