采用重稀土改善焊缝韧性的研究

用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X 射线能谱仪(EDAX)研究了重稀土元素对低合金钢焊缝金属韧性的影响.结果发现,采用适当的焊条药皮配方和焊接工艺可使重稀土元素微量过渡到焊缝金属中(约10ppm),减少了夹杂物的面密度和面积百分数,显著提高了焊缝金属的低温韧性。夹杂物的减少和低温韧性的提高有很好的对应关系,因此可以认为,重稀土元素对焊缝金属的净化和变质作用是提高焊缝低温韧性的主要原因。此外,还对焊缝金属中夹杂物的类型进行了较深入的鉴别。     

Mechanism of effect of rare earth oxides on high temperature corrosion resistance of weld metal

Through the addition of rare earth oxides into the coming of electrodes, the high temperature oxidation and sulphidation resistance of weld metal were studied. The transfer mechanism of rare earth oxides from coating to the welding pool and the physicochemical reaction during the process were analyzed. With the application of scanning electron microscope and energy spectrometer, the mechanism of weld metal corrosion in air and sulphur environment were studied. The result shows that the addition of rare earth oxides can improve the high temperature resistance of weld metal, especially in sulphidation environment. The electrodes in which La2O3 is added have better performance than the electrodes in which CeO2 is added. The existence form and distribution characteristic of rare earth are defined. It is believed that the marked effect of rare earth oxides in sulphur environment is related to the corrosion mechanism.     

焊缝内夹杂物的热力学分析

采用Ｘ射线能谱仪（ＥＤＡＸ），扫描电镜（ＳＥＭ），电子探针（ＥＰＭＡ）以及微粒分析仪（ＭＰＡ）实验手段和热力学分析方法，研究了轻稀土合金对焊缝金属内夹杂物的冶金作用。结果表明，轻稀土合金过渡到焊缝后，起着净化和变质处理作用。而且，它的脱氧作用比其脱硫作用要强。     

稀土含量对熔敷金属扩散氢逸出特性及性能的影响

通过碱性焊条药皮向焊缝金属过渡稀土元素的方法，并结合酒精法测氢技术、低温冲击试验以及小铁研抗裂性试验，研究了稀土含量对熔敷金属扩散氢逸出特性及性能的影响。研究结果表明，适量的稀土能显著降低熔敷金属的扩散氢含量，提高焊缝的低温韧性，并改善扩散氢的逸出特性，即使熔敷金属开始阶段扩散氢的逸出速率增加，对后期阶段的逸出速率影响较小；稀土的最佳加入量为0．5％，继续增加时，焊缝的韧性及抗裂性开始恶化。     

Improving the toughness of weld metal by adding rare earth elements

Abstract

The effect of heavy rare earth metals (REM) on the toughness of low alloy steel weld metal has been studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and an energy dispersion X-ray spectrometer (EDX). The results show that by adopting an appropriate flux coating and welding procedure, a small amount of heavy REM (about 10ppm) can be transferred to weld metal, thus reducing area density and area percentage of inclusions and improving the low temperature toughness of the weld metal. Since a decrease in inclusion content correlates well with an increase in low temperature toughness, it can be considered that cleaning and modification of weld metal by heavy REM greatly contributes to improving low temperature toughness. In addition, an examination of types of inclusions has been carried out.     

Effect of slag variations on ANSI/AWS A5.1–91 E6013 electrode properties: replacement of TiO2 in electrode coating with MnO,FeO, CaO,MgO, K2O,or Na2O

Abstract

The present work is part of a research programme to study the effect of variation of the coating composition of covered rutile manual electrodes on both operational and deposited weld metal properties. According to previous results obtained for rutile electrodes, an increase of slag basicity, achieved through modifications in the coating, produces an improvement of the impact properties of the deposited weld metal, as well as a decrease in the diffusible hydrogen, along with beneficial changes in the operational properties of the electrode. The aim of the present work is to study the influence of the replacement of titanium oxide with oxides of alkali metals (sodium and potassium), alkaline earth metals (calcium and magnesium), and iron and manganese oxides in the coating of an ANSI/AWS A5.1–91 E6013 type electrode on the operational characteristics of the electrode and the microstructure, mechanical properties, and diffusible hydrogen content of the electrode weld metal. Tensile strength and Charpy V notch impact properties were measured in the all weld metal samples produced using each of the seven electrodes designed for the present study. A cross-section from each coupon was used to determine the chemical composition of the deposit and to carry out a metallographic study using a light microscope. As a result of the addition of different oxides, changes in the operational properties were observed using both direct and alternating current, as well as a decrease in the diffusible hydrogen content in the weld metal. Also, electrodes in which rutile was substituted by sodium oxide in the coating showed an improvement in the impact properties of the deposit.     

稀土对钢轨耐磨堆焊层金属组织及韧性的影响

对不同稀土含量的自保护药芯焊丝堆焊层金属进行了室温冲击试验和金相组织观察;并对冲击断口形貌进行了扫描电镜(SEM)分析和夹杂物的能谱(EDS)分析,同时对夹杂物生成自由能进行了计算。结果表明,随稀土的增加,焊缝冲击韧性先增加后降低,加入4%的稀土,具有良好的晶粒尺寸和分布,冲击韧性最高;加入量超过8%时,形成的稀土硫化物、稀土氧化物残存于焊缝中形成夹杂,焊缝冲击韧性降低。热力学计算得到了几种夹杂物的生成先后顺序,从另一个角度解释了稀土的净化除杂作用。     

低合金高强钢焊缝熔敷金属强韧化机理

向焊缝熔敷金属过渡微量的Ti-B和稀土元素,可以有效地抑制先共析铁素体的析出,使焊缝获得细小、均匀的针状铁素体组织.从而提高了焊缝的低温冲击韧性.通过透射电镜观察,发现焊缝中合金元素能形成细小、难溶的非金属夹杂物,成为针状铁素体的形核核心;Ti能形成细小、难溶而弥散分布的化合物(TiO)质点,对针状铁素体的形核更为有利.针状铁素体由许多亚结构组成,这相当于进一步细化了晶粒,是提高焊缝熔敷金属低温韧性微观原因.     

J807RH高强度高韧性超低氢电焊条的研制

通过向焊缝金属过渡微量的Ti-B和稀土元素,可以有效地抑制先共析铁素体的析出,使焊缝获得细小、均匀的针状铁素体组织。从而提高了焊缝的低温冲击韧性。     

2090Ce铝锂合金的焊缝热裂纹敏感性及接头力学性能

采用焊缝合金化手段，通过设计新型焊丝向焊缝中添加Ｌｉ、Ｚｒ和Ｃｅ等合金化元素，研究了２０９０Ｃｅ稀土铝锂合金焊缝金属的热裂纹敏感性；探讨了合金元素对接头力学性能的影响及作用规律；进而研究了适用于焊接２０９０Ｃｅ合金的焊丝合金成分。试验结果表明，向焊缝金属中添加适量的合金元素Ｌｉ、Ｚｒ和Ｃｅ，能够细化晶粒；增加焊缝中的共晶数量并改善其分布形态，从而有助于降低焊缝金属的热裂纹敏感性。另外，适量的Ｌｉ、Ｚｒ和Ｃｅ等合金元素还能够在不降低接头塑性的同时，明显改善接头的强度；但Ｌｉ和Ｃｅ含量过多则会对接头性能，特别是塑性造成损害。所设计的焊丝材料能够适用于焊接２０９０Ｃｅ稀土铝锂合金。     

影响自保护药芯焊丝焊缝韧性及离散性的因素

介绍了自保护药芯焊丝焊缝金属的韧化机理,分析了合金元素、夹杂物及稀土元素对焊缝韧性的影响,总结得出焊缝组织中粗大的马氏体与奥氏体组元(M-A组元)是造成韧性离散的主要原因。通过选择合适成分的焊丝,并配合恰当的热输入,可以减少并细化组织中的M-A组元,使韧性稳定。     

闪光焊FeCrAl合金管材的接头组织及性能

采用闪光焊对FeCrAl合金进行对接接头焊接,通过扫描电子显微镜及能谱仪等手段研究了焊接接头的显微组织特征、不同区域氧化物颗粒的分布情况及力学性能. 结果表明,闪光焊焊接FeCrAl合金所得焊接接头显微组织主要为等轴晶,在焊缝和热影响区氧化物未出现明显聚集及向晶界偏聚的现象,且在晶内和晶界都可以呈现弥散分布的特征;焊接接头抗拉强度值达到594 MPa,为母材强度的90.5%;接头断裂在焊缝区,整体呈现脆性断裂模式;焊缝晶粒的粗化导致焊缝区硬度降低,最终引起焊接接头出现软化.     

Effect of Ti on the microstructure and mechanical properties of MAG multipass weld metal

Metal active gas (MAG)welding has been carried out on microalloy controlled rolling steel (S355J2W)by two kinds of welding wires with different Ti content.The mechanical tests have been carried out on the welded joint.The optical microscope and scanning electron microscope (SEM)observations have been performed to investigate the effect of microalloy element Ti on the microstructure of weld metal and impact fracture,respectively.The microstructure of the MAG multipass weld metal includes the columnar grain zone (CGZ)consisting of primary ferrite (PF),ferrite with second phase (FS)and acicular ferrite (AF),and the fine grain zone (FGZ)consisting of polygonal ferrite due to the heat effect of subsequent welding pass.It has been found that the small amount of Ti can significantly increase the impact energy of the weld metal at low temperature and weakly affect tensile strength of welded joint.By adding small amount of Ti,the inclusions have changed from Mn-Si-O inclusions to Ti-bearing inclusions,which causes the Mn-depleted zones (MDZs)much larger and is beneficial to the impact energy by promoting the AF formation,refining the PF and pinning the austenite grain boundary during the subsequent transformation process.     

因瓦合金4J36等离子焊接工艺及接头性能

试验采用等离子弧焊设备对4J36因瓦合金板材进行焊接工艺试验,借助光学显微镜(OM)、扫描电镜(SEM)、能谱分析仪(EDS)、X射线衍射仪(XRD)和洛氏硬度计等手段分析接头的微观组织和力学性能.结果表明,合理的等离子工艺参数下焊接接头成形良好,抗拉强度可达到母材的93.6%;接头基体为γ相,同时存在γ'(Ni₃(Al,Ti))强化相;母材为细小的等轴晶,焊缝处呈树枝状结晶且晶粒粗大,热影响区靠近熔池部分的晶粒过热长大,靠近母材部分为均匀细小的等轴晶;焊接接头拉伸断口表现为韧性断裂,硬度最低值出现在热影响区.     

稀土对20MnCrNi2Mo耐磨铸钢过冷奥氏体转变的影响机理

采用L78 RITA淬火热膨胀仪、QUANTA400扫描电镜和JEM-2100透射电镜等设备研究镧铈混合稀土对20MnCrNi2Mo耐磨铸钢过冷奥氏体连续转变动力学及显微组织的影响,采用ICP-MS电感耦合等离子质谱仪测定稀土的固溶量,通过透射电镜观察探索固溶稀土在钢中的存在状态,结合对La的界面扩散系数的测定计算,综合分析镧铈混合稀土的作用机理。结果表明,镧铈混合稀土使20MnCrNi2Mo耐磨铸钢CCT曲线整体向右下方移动,促进了连续冷却过程中下贝氏体的形成,提高了淬透性,使得板条马氏体组织中孪晶亚结构增加。分析认为,固溶于钢中的稀土原子富集于晶界等晶体缺陷处,降低晶界能、阻塞扩散通道,推迟新相的形核-长大过程,进而影响组织转变。     

稀土元素改善高锰钢焊条的组织性能

在高锰钢焊条药皮中加入一定比例的稀土元素,具有细化晶粒,提高塑性,韧性及强度,改善组织形态,净化焊缝金属的作用,从而有效地降低了高锰钢焊接时在熔合区产生热裂的敏感性,对于高锰钢的修补,堆焊及构件之间的强度焊接均优于不含稀土元素的同类焊接材料。     

Synergism between rare earth cerium(IV) ion and vanillin on the corrosion of cold rolled steel in 1.0 M HCl solution

The synergism between rare earth cerium(IV) ion and vanillin on the corrosion of cold rolled steel (CRS) in 1.0 M HCl solution was first investigated by weight loss, potentiodynamic polarization, ultraviolet and visible spectrophotometer (UV–vis), X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). The results revealed that vanillin had a moderate inhibitive effect, and the adsorption of vanillin obeyed the Temkin adsorption isotherm. For rare earth Ce⁴⁺, it had a negligible effect. However, incorporation of Ce⁴⁺ with vanillin significantly improved the inhibition performance, and produced strong synergistic inhibition effect. Depending on the results, the synergism mechanism was proposed.     

INFLUENCES OF NEODYMIUM ON MAGNETIC CHARACTERISTICS OF ELECTROPLATING CoNdNiMnP FILMS

In order to improve the performances of electroplating permanent magnetic films, ncodymium is introduced into the electroplating CoNiMnP permanent magnetic films. The influences of the neodymium content are also investigated by varying NdCl3 plating bath concentration. The neodymium-doped films are analyzed by energy dispersive spectrum (EDS), vibrating sample magnetometer (VSM) and magnetic force microscope (MFM). The experimental results show that high magnetic performances of CoNdNiMnP permanent magnetic films with vertical anisotropy could be fabricated with current density 5mA/crne at room temperature. With the increasing of neodymium contents, the magnetic properties of films were improved. However when neodymium contents exceeded 3.5wt%, the magnetic properties of films are not improved any more. The increase of film magnetic properties results from the ferromagnetic-coupling between light rare earth element-neodymium and transition metal element-cobalt.     

Rare Earth Compounds in Cemented Carbides with Trace Rare Earth Additions

The morphology,structure and distribution of the rare earth compounds in the YG8R.YT5R and YT14Rcemented carbides with additions of trace light rare earths were studied with an analytical electron microscope.The particles of the rare earth compounds in these alloys are all spherical and distribute at interfaces betweenthe Co-cement phase and WC hard phase or(TiW)C solid solution,and in the(TiW)C solid solution.In theYG8R and YTI4R alloys,the rare earth compound is RE_2O_3 with a bcc structure,while in the YT5R alloy.the rare earth compound is RE_2O_2S with a hcp structure.     

一种针对低匹配焊接接头的"等承载"设计方法

为提高高强钢低匹配接头承载能力,提出了低匹配接头与母材具有相等的静载承载能力和疲劳抗力的"等承载能力"(ELCC)概念.从安全性角度出发,焊接结构必须同时具有足够的强度和应力松弛能力,而强度失配接头的断裂模式类型能够同时反映接头的强度、塑性变形能力以及焊缝与母材之间塑性变形的非均匀程度.母材先于焊缝发生塑性变形的全面屈...