T91/P91钢配套焊条CHH717的研制

讨论了影响所研制焊条熔敷金属理化性能的主要因素,尽可能低的S、P、Al等有害杂质含量及合理的合金含量可以得到良好的综合力学性能.经过试验确定了热处理工艺,并通过相变点Ac1的测试得到了印证.试验结果表明,焊条的焊接工艺性良好.熔敷金属的化学成分及力学性能均满足有关标准要求.微观组织观察表明,经760 ℃×2 h回火后其熔敷金属显微组织为回火索氏体.对所研制焊条的熔敷金属进行了625 ℃外推105 h高温持久强度试验,证明此焊条可广泛应用于超(超)临界发电设备用相应耐热钢的焊接.     

T/P92钢镍对熔敷金属组织和性能的影响

研究了焊丝中添加不同含量镍对熔敷金属组织和性能的影响.通过TEM电镜观察、扫描电镜以及XRD衍射试验说明熔敷金属中存在析出相Cr23C6和MX,熔敷金属中不存在Laves相.通过光学电镜以及高温力学性能试验对熔敷金属组织和性能进行研究.结果表明,伴随熔敷金属中镍含量的提高,强度增加;当镍含量〈1.0%时,其室温下的韧度值随镍含量的提高而增加,当镍含量≥1.0%时,韧度开始下降.     

镀液合金元素对钢镀铝界面组织的影响

研究了钢铁热浸镀镀液中添加不同元素对合金层生长的影响,检测了镀层的形貌和结构并分析了合金层形成和生长的机理.结果表明,镀层由表面的浸铝层和内层的合金层构成;合金层由Fe2Al5和FeAl3等Fe-Al金属间化合物组成;Si的添加能有效抑制合金层的生长,Mn与Mg的作用不明显,Zn则加剧了合金层的生长;合金层的生长随时间近似遵循抛物线关系.     

合金元素对高强管线钢埋弧焊缝组织性能的影响

通过对X80管线钢进行埋弧焊接试验,分析了合金元素Mn、Ni对高强度管线钢埋弧焊缝的显微组织和力学性能的影响.试验结果表明,当Mn元素含量过高时,焊缝金属的冷裂纹敏感指数提高,细化原奥氏体晶粒尺寸,对针状铁素体形核不利湘比较而言,Ni元素对焊缝的冷裂纹敏感指数影响较小,且使焊缝金属易于产生交滑移,更易保证焊缝针状铁素体含量,从而提高焊缝金属的韧性;另外,随着Mn、Ni元素含量的增加,焊缝金属中先共析铁素体受到抑制.     

元素V对奥氏体焊缝金属晶间腐蚀敏感性的影响

采用透射电镜(TEM)分析技术研究了1Cr19Ni23N焊条熔敷金属中钒含量对组织及对熔敷金属抗晶间腐蚀性能的影响.结果表明,低钒含量焊条熔敷金属组织中沿奥氏体晶界析出M23C6型富铬碳化物,在晶界附近形成贫铬层,导致晶间腐蚀的发生;高钒含量焊条熔敷金属组织中,V优先于Cr与C形成细小弥散的碳化钒分布在晶粒内部,使得该焊条在保持原较高碳含量的基础上,通过改变碳化物形态和分布达到了保持高强度和改善晶间腐蚀敏感性的目的.     

降熔元素对T91钢TLP连接组织和性能的影响

T91钢TLP连接的关键在于降熔元素MPD的选择.在1230℃～1260℃,3～5 MPa下,采用氩气保护,以自制中间层对T91钢管进行了瞬时液相扩散连接(TLP).运用正交试验分析了中闻层成分、温度和压力时接头显微组织和力学性能的影响.结果表明:在合适的工艺参数下,T91钢TLP连接接头可获得良好的组织和性能;当中间层中的降熔元素含量差别较小时得到的接头组织仍然差别较大.指出中间层中的降熔元素对中间层的润湿、快速扩散和均匀化均有重要作用;以母材为基体加适量MPD(其中以B元素为最佳)可制出合适的中间层.     

合金元素对Fe-2.5B组织和耐锌蚀性能的影响

针对热镀锌行业中的熔融锌液对材料产生的腐蚀问题,通过向Fe-2.5B合金材料中分别添加1wt%的C、Si、Mn等微量合金元素,研究两相的微观形貌、腐蚀性能和力学性能的变化.结果表明:加1%C的影响较为明显,耐锌液腐蚀性能提高9倍左右,抗弯强度下降一半.加1%Si和1%Mn后α相略有减少,共晶组织骨架粗大致密,耐熔锌腐蚀性能和抗弯性能都有不同程度的提高.     

合金元素对AZ91镁合金组织和性能影响的研究进展

综述了国内外对AZ91镁合金的研究现状,介绍了稀土、碱土和第Ⅳ、Ⅴ族元素三类不同合金化元素对AZ91镁合金组织和性能的影响,并展望了未来提高AZ91镁合金耐热性的发展方向.     

合金元素对耐候熔敷金属力学及耐蚀性能的影响

采用周浸加速腐蚀试验,模拟工业大气腐蚀环境,通过组织分析、锈层微观成分及形貌分析、电化学分析等手段,研究了Ni,Cr,Cu元素对耐候熔敷金属耐蚀性能及力学性能的影响规律. 结果表明,Ni元素有利于增加组织中针状铁素体含量,提高熔敷金属−40 ℃冲击韧性,Cr元素增加,熔敷金属−40 ℃冲击韧性降低. 合金元素有利于提高腐蚀锈层中的α-FeOOH的含量,增加锈层致密度,提高锈层阻抗,降低自腐蚀电流密度. Cu元素有利于提高熔敷金属腐蚀初期和后期的耐蚀性能;腐蚀初期,Cr元素提高耐蚀性能的作用不如Cu和Ni,但是腐蚀后期Cr提高锈层耐蚀性能的作用明显.     

δ-铁素体对GX8CrNi12钢用焊条熔敷金属冲击韧性的影响

为了研究GX8CrNi12钢用焊条熔敷金属中δ-铁素体对冲击韧性的影响,采用Balmforth相组分图对焊条熔敷金属相组织体积分数的预测,制备了5种不同化学成分的焊条。采用多功能X射线衍射仪和金相显微镜定性定量的确定了5种焊条熔敷金属的金相组织及体积分数;采用冲击试验机测定焊条熔敷金属的冲击韧性。结果表明：GX8CrNi12钢用焊条熔敷金属的冲击韧性主要取决于δ-铁素体的含量,随着δ-铁素体含量的增加,冲击韧性降低。     

合金元素对SiC/Al双连通复合材料力学性能的影响

采用真空压力浸渗方法制备SiC3D/ZL201A双连通复合材料,借助电子显微镜(SEM)、能谱(EDS)等分析手段,研究合金元素对SiC/Al双连通复合材料组织结构及力学性能的影响。结果表明:SiC3D/ZL201A界面存在Cu、Mg等元素的偏聚,界面组织结构得到改善;合金元素导致SiC3D/ZL201A压缩强度高于SiC3D/纯铝,弯曲强度低于SiC3D/纯铝;SiC3D/ZL201A失效形式主要表现为界面断裂,SiC骨架呈现脆性断裂,铝合金基体呈现韧性撕裂断裂;合金元素产物通过钝化裂纹,改变裂纹扩展方向,桥联等作用提高复合材料的力学性能。     

合金元素对铸铁共析转变的影响

介绍了铸铁共析转变的概念、特点和转变产物;说明了没有其他合金的铸铁共析转变时,奥氏体中富余碳的去向问题;阐明了合金元素对铸铁共析转变温度、转变产物的影响情况和珠光体形成与生长机理;提出了降低铸件断面敏感性的途径.     

合金化和热处理对难熔金属硅化物基合金组织和性能影响的研究现状

综述了合金化和热处理对硅化物基合金组织和性能的影响。在铌硅化物基合金中添加Mo，W或Al后，电弧熔炼态组织中的硅化物相为βNb5Si3；添加Cr或者V后，硅化物相为αNb5Si3：加入Ti后，硅化物相是Nb3Si。添加Ti，Hf和B可提高铌硅化物基合金的室温断裂韧性，添加W或Mo后合金的高温强度显著提高，而添加Cr，Al和Ti明显改善其高温抗氧化性能。在MoSi2中加入W，Nb和Ge等合金化元素后分别形成（Mo，W）Si2，（Mo，Nb）Si2或Mo（Si，Ge）2等硅化物，但在钼硅化物基合金中添加B后生成α—Mo，Mo3Si和T2相（MoSiB2），并且T2相所占的体积百分比与B的含量成正比。α-Mo相的含量对合金的断裂韧性和抗氧化性有重要影响。Nb或Mo的硅化物基合金的热处理温度都比较高，经过再结晶退火后合金中的组成相及其所占的体积百分比均发生变化，并且组织粗化，但分布更加均匀，从而对力学性能有显著的影响。     

合金元素对镁及镁合金力学性能强化的研究

总结了近年来镁合金中加入合金元素来改善镁合金力学性能的研究现状。论述了镁的合金化原理。介绍了在一些常用镁合金中分别加入Sn、Sb、Bi、Pb、Y、Nd、La、Sr、Sc、B、Ca、Si、Zr、Ag、Cd等合金元素对镁合金力学性能的强化效果以及强化机理。认为固溶强化和第二相强化是加入合金元素强化镁合金的主要方式。     

Microstructure and Mechanical Properties of B-Bearing Austenitic Stainless Steel Fabricated by Laser Metal Deposition In-Situ Alloying

In the field repair application of laser metal deposition (LMD), the kinds of powder materials that can be used are limited, while the equipment components are made of various materials. Hence many components have to be repaired with heterogeneous materials. However, it is difficult to match the mechanical properties between the repaired layer and the substrate due to the different materials. Based on the high flexibility of raw materials and processes in LMD, an in-situ alloying method is proposed herein for tailoring the mechanical properties of LMDed alloy. Using different mixing ratios of Fe314 and 316L stainless steel powders as the control parameter, the microstructure and mechanical properties of B-bearing austenitic stainless steel fabricated by LMD in-situ alloying with different proportions of Fe314 and 316L particles were studied. With the increase in the concentration of 316L steel, the volume fraction of the eutectic phase in deposited B-bearing austenitic stainless steel reduced, the size of the austenite dendrite increased, the yield strength and ultimate tensile strength decreased monotonically, while the elongation increased monotonically. Moreover, the fracture mode changed from quasi-cleavage fracture to ductile fracture. By adding 316L powder, the yield strength, tensile strength, and elongation of deposited B-bearing austenitic stainless steel could be adjusted within the range of 712 MPa-257 MPa, 1325 MPa-509 MPa, and 8.7%-59.3%, respectively. Therefore, this work provides a new method and idea for solving the performance matching problem of equipment components in the field repair.     

P20模具钢表面合金化组织与性能

在P20模具钢表面进行激光合金化,利用金相显微镜、维氏硬度计等设备检测了合金化层的组织和性能。试验表明,激光合金化可在材料表面获得组织致密,晶粒细化,深度大,与基体结合牢固的强化层。合金化区的硬度范围为635～699HV0.2,热影响区硬度范围为441～474HV0.2。激光合金化试样的耐磨损性能比预硬化的P20钢提高了35%。采用激光合金化对模具表面进行强化,将大大提高模具的使用寿命。     

Laves Phase Formation and Its Effect on Mechanical Properties in P91 Steel

Effect of Laves phase formation on mechanical properties in a pressurized T-junction of P91 steel pipe at849 K for 58,000 h with 25.65 MPa vapor pressure was studied. Thermodynamic calculations had been performed by using the software Thermo-Calc to study the phase at equilibrium state. Counter plot of von Mises stress in the pipe during service life was calculated by finite element analysis to study the effect of the operated stress distribution on the evolution of Laves phase. The change in the microstructure and mechanical properties in the sites with different stress was also studied. The results indicated that the formation of Laves phase in P91 steel was a thermodynamically possible process due to enrichment of Mo and depletion of C adjacent to M23C6 particles or along martensite lath and packet boundaries. The formation of Laves phase had a detrimental influence on the mechanical properties in P91 steel. The mean size of Laves phase would be significantly increased with increasing operated stress, leading to a reduction in tensile properties and impact energy. In particular, crack initiation energy and crack growth energy during impact test rapidly decreased with increasing the mean size and volume fraction of Laves phase.     

T91/P91窄间隙热丝TIG焊接工艺对接头力学性能的影响

通过对T91/P91窄间隙热丝TIG焊试验,对比研究了焊接接头各区包括焊缝、热影响区、母材的显微组织,以及各项力学性能比如常温拉伸、高温拉伸、硬度及冲击性能,从而探究窄间隙热丝TIG焊对T91/P91钢焊接性的影响.试验结果表明,焊接接头组织均匀,主要为回火马氏体;抗拉强度达到了母材水平甚至比母材更强;焊缝区域硬度分布比较均匀,硬度值高于热影响区和母材;焊缝的冲击韧性也与母材相当.研究结果表明,窄间隙热丝TIG焊可以改进T91/P91焊接接头的焊接质量,焊接接头各项力学性能均满足使用需求,从而获得了较高质量的焊接接头.     

合金化对AZ91D镁合金组织与力学性能的影响

利用光学显微镜（OM）和X射线衍射（XRD）分析了分别加入合金化元素Ce，Si和Ca后AZ91D合金的铸态组织和相组成，测试了合金室温拉伸性能和硬度。结果表明：加入Ce和Si后合金组织中分别生成杆状Al4Ce和汉字状Mg2Si相，而加入Ca后无新相生成，加入的Ca主要固溶于β相中；Al4Ce和Mg2Si相在合金凝固过程中被推移到生长界面，Ca原子偏聚在生长界面前沿，从而阻碍枝晶的自由生长，细化合金铸态组织：Ce和Ca的加入可提高合金室温综合力学性能，且前者提高程度要高于后者提高程度，而Si的加入却降低合金室温综合力学性能。     

A Study of Microstructure and Mechanical Properties of Grade 91 Steel A-TIG Weld Joint

In the present study, A-TIG welding was carried out on grade 91 steel plates of size 220 × 110 × 10 mm using the in-house developed activated flux to produce butt-joints. The room-temperature impact toughness of the A-TIG as-welded joint was low due to the presence of untempered martensite matrix despite the low microinclusion density caused by activated flux and also low δ-ferrite (<0.5 %) content. Toughness after postweld heat treatment (PWHT) at 760 °C-2 h was 20 J as against the required value of 47 J as per the specification EN: 1557:1997. However, there was a significant improvement in impact toughness after PWHT at 760 °C for 3 h. The improvement in toughness was attributed to softening of martensite matrix caused by precipitation of carbides due to tempering reactions. The precipitates are of type M₂₃C₆, and they are observed at grain boundary as well as within the grains. The A-TIG-processed grade 91 steel weld joint was found to meet the toughness requirements after PWHT at 760 °C-3 h. Observations of fracture surfaces using SEM revealed that the as-welded joint failed by brittle fracture, whereas post-weld heat-treated weld joints failed by decohesive rupture mode.