Gas Tungsten Arc Welding of 316L Austenitic Stainless Steel with UNS S32205 Duplex Stainless Steel

In the present work, dissimilar welding between UNS S32205 duplex stainless steel (DSS) and 316L austenitic stainless steel (ASS) was performed by using gas tungsten arc welding and ER2209 filler at two different heat inputs (0.52 and 0.98 kJ/mm). Microstructures were characterized using reflected light optical microscope and scanning electron microscope. Micro-hardness and tensile properties were measured across the weld for both the heat inputs. The microstructure of the welded region was primarily austenitic (for both heat inputs) with Widmanstätten morphology. The grain size of the heat affected zone on DSS side was very large (~200 µm) for the high heat input sample with the presence of partially transformed austenite and acicular austenite. The precipitation of intermetallic phases and carbides was not observed for both the heat inputs. The proportion of ferrite in the weld metal (as measured by feritscope) was higher for the high heat input sample than the low heat input sample. During the tensile test, fracture occurred in 316L ASS base metal (because of its lower strength) in ductile manner. For high heat input welds, the impact tested sample showed the presence of fine spherical precipitates rich in Cr, Mn and Fe in the fracture surface of weld metal.     

Microstructure and Texture Development during Cold Rolling in UNS S32205 and UNS S32760 Duplex Stainless Steels

Metallurgical and Materials Transactions A - In the present study, microstructure and texture evolution during cold rolling in UNS S32205 and UNS S32760 duplex stainless steel was investigated....     

Corrosion Study of Super Ferritic Stainless Steel UNS S44660 (26Cr-3Ni-3Mo) and Several Other Stainless Steel Grades (UNS S31603, S32101, and S32205) in Caustic Solution Containing Sodium Sulfide

Electrochemical techniques, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were used in this study to show how the corrosion mechanism of several commercial grades of stainless steel in hot caustic solution is strongly influenced by the presence of sodium sulfide. Experimental results from super ferritic stainless steel UNS S44660 (26Cr-3Ni-3Mo) were compared to austenitic stainless steel UNS S31603, lean duplex stainless steel (DSS) UNS S32101, and standard DSS UNS S32205 in caustic solution, with and without sodium sulfide, at 443 K (170 °C). Weight loss measurements indicated that corrosion rates of UNS44660 were much lower than the other grades of stainless steel in the presence of the sodium sulfide. Potentiodynamic polarization and linear polarization resistance measurements showed that the electrochemical behavior was altered by the adhesion of sulfur species, which reduced the polarization resistances and increased the anodic current densities. SEM and XPS results imply that the surface films that formed in caustic solution containing sodium sulfide were defective due to the adsorption of sulfide, which destabilized the passive film and led to the formation of insoluble metal sulfide compounds.     

S32205双相不锈钢中σ相的析出及其对力学性能的影响

对S32205双相不锈钢在850℃进行时效处理,采用光镜、扫描电镜、能谱仪、硬度和拉伸测试等手段研究了σ相的析出规律及其对力学性能的影响。结果表明:时效15 min后σ相开始沿γ/α或α/α晶界析出,并向铁素体一侧长大,其析出反应为铁素体发生转变形成σ相和γ2相;时效时间延长,σ相的析出量增加,时效240 min后σ相的含量达到18%,并导致双相不锈钢的硬度明显增加、强度略有提高,而塑性显著下降;拉伸断口的断裂类型由典型的韧性断裂向以准解理断裂为特征的脆性断裂转变。     

Effects of Cu Content on Inclusions and Pitting Corrosion in S32205 Duplex Stainless Steel

Cu is an austenite-forming element in duplex stainless steel, and the precipitation of Cu-rich phase can improve the strength of the alloy. However, the role of Cu element in the corrosion resistance of stainless steel is widely controversial. Herein, the effects of different Cu content on the formation of inclusions and the pitting resistance of duplex stainless steel are studied by using potentiodynamic anodic polarization test, immersion corrosion, scanning electron microscope, and electron probe microanalysis. The results show that the pitting potential decreases significantly with the increase of Cu content, which greatly reduces its ability to resist Cl⁻ corrosion. The reason is that Cu increases the driving force for the formation of Al-containing oxides, which increases the number and size of Al-containing inclusions formed in the process of melting and solidification. At the same time, Cu promotes the formation of Cr-depleted zone, which promotes the formation of microcracks and pitting corrosion between steel matrix and inclusions in duplex stainless steel.     

Experimental and Computational Investigation of Structural Integrity of Dissimilar Metal Weld Between Ferritic and Austenitic Steel

The structural integrity of dissimilar metal welded (DMW) joint consisting of low-alloy steel and 304LN austenitic stainless steel was examined by evaluating mechanical properties and metallurgical characteristics. INCONEL 82 and 182 were used as buttering and filler materials, respectively. Experimental findings were substantiated through thermomechanical simulation of the weld. During simulation, the effect of thermal state and stress distribution was pondered based on the real-time nuclear power plant environment. The simulation results were co-related with mechanical and microstructural characteristics. Material properties were varied significantly at different fusion boundaries across the weld line and associated with complex microstructure. During in-situ deformation testing in a scanning electron microscope, failure occurred through the buttering material. This indicated that microstructure and material properties synergistically contributed to altering the strength of DMW joints. Simulation results also depicted that the stress was maximum within the buttering material and made its weakest zone across the welded joint during service exposure. Various factors for the failure of dissimilar metal weld were analyzed. It was found that the use of IN 82 alloy as the buttering material provided a significant improvement in the joint strength and became a promising material for the fabrication of DMW joint.     

Effect of Microstructure and Surficial Oxidation on the Wear Behavior of an UNS S41003 Stainless Steel

The UNS S41003 ferritic stainless steel is a low-carbon alloy that has great corrosion and oxidation performances in wet and aqueous environments, as well as it has high mechanical strength and ductility when compared to the most ordinary low-carbon steels. These great characteristics, allied to its relatively low manufacturing cost, have made it a potential option to replace structural steels in many applications. Although it is a current trend, there are still few published studies that relate this steel manufacturing process with microstructural evolution and mechanical behavior, mainly regarding its wear behavior, which is a substantial and sometimes limiting characteristic for its applications. In this context, this article presents a pioneering study about the use of biphasic microstructures (ferrite–martensite) and controlled surficial oxidation to enrich the wear behavior of a UNS S41003 steel type. This study concludes that, if well planned, both the increase of martensite fraction and the controlled growth of an adherent and compact oxide layer on the steel surface significantly improve its wear performance, decreasing its wear rate up to 93%.     

The Effect of Surface Preparation on the Precipitation of Sigma During High Temperature Exposure of S32205 Duplex Stainless Steel

Although the formation of sigma phase in duplex stainless steels is reasonably well documented, the effect of surface finish on its formation rate in surface regions has not been previously noted. The growth of the sigma phase precipitated in the subsurface region (to a maximum depth of 120 μm) has been quantified after heat treatment of S32205 duplex stainless steel at 1073 K (800 °C) and 1173 K (900 °C) after preparation to two surface finishes. Here, results are presented that show that there is a change in the rate of sigma phase formation in the surface region of the material, with a coarser surface finish leading to a greater depth of precipitation at a given time and temperature of heat treatment. The growth rate and morphology of the precipitated sigma has been examined and explored in conjunction with thermodynamic equilibrium phase calculations.

     

调质高强度压力容器钢板A517GrB的研制

介绍了济钢采用微合金化设计、控轧、调质等工艺开发的高强度压力容器钢A517GrB。通过光学显微镜、透射电镜观察分析等实验手段,研究了回火温度对力学性能和组织的影响,结果表明:随回火温度的升高,组织发生相变、回复、再结晶、碳化物析出等过程,钢板的强度降低,韧性提高。最佳回火温度为670℃。     

低碳贝氏体钢的摩擦焊接性

试验研究了低碳贝菌体钢０．１７℃－１，１．７２Ｍｎ－１。１２Ｃｒ－０．５２Ｍｏ的焊接工艺参数及热处理对组织和性能的影响。结果表明，摩擦变形量为１．０ｍｍ，焊接接头采用９１０℃正火。３５０℃回火，可得到良好的组织和性能。     

Fatigue Strength of Trolley Bridge Stringers Made of ASTM A7 Steel

Nineteen S15×42 (in U.S. units) stringers from a trolley bridge made of ASTM A7 carbon steel were tested in constant-amplitude fatigue. The bridge was built in 1900 and was abandoned in 1958. In 1985, the stringers were removed from the bridge and were tested in the laboratory. The test results showed that uniform corrosion and pitting reduced the fatigue strength of the stringers from Category A to Category D. The fatigue strength was reduced more by pitting than by uniform corrosion.     

Parametric Optimization of Pulsed Current Gas Arc Welding of Dissimilar Welding Between UNS32750 and AISI 321 Based on Taguchi Method

In this research, Taguchi method (DOE technique) was used to optimize welding parameters in a dissimilar joint between the duplex stainless steel UNS32750 and the austenite stainless steel AISI 321 for the corrosion resistance. For joining, pulsed current gas arc welding with the ER2594 electrode was used. Pulse current, background current, % on time and current frequency were considered in three levels. Welding conditions were based on the L₉ Taguchi’s orthogonal array design of experiment. Signal-to-noise ratio was used to estimate the optimal conditions. The parameters and levels were considered as the optimal conditions in which the higher pitting potential could be obtained. Analysis of variance was carried out to determine the influential effect of each parameter. The pitting potential was evaluated by the potentiodynamic polarization test in the 3.5% NaCl solution at room temperature. Microstructural characterization and mechanical properties of the optimal joint were determined by optical microscopy and Vickers microhardness, respectively. According to the results of Taguchi method, the pulse current of 130 A, the Background current of 60 A, the % on time of 90% and the current frequency of 3 Hz were obtained as the optimal conditions. Pitting potential under optimal conditions (1.03 V) was close to Taguchi prediction (0.99 V). Analysis of Variance also indicated that the most effective parameter on the pitting corrosion was Background current. The percentage contributions of pulse current, background current, current frequency and % on time were 38.01, 32.48, 22.85 and 6.6%, respectively. The results showed that adjusting heat input led to the equal austenite-ferrite proportion.     

油井管用ASTM4137钢的冶炼工艺及质量

对ＡＳＴＭ４１３７钢生产和试验数据的分析研究得出影响ＡＳＴＭ４１３７钢材横向低温冲击韧性的因素为硫、铝、钛等杂质元素,硫含量偏高是导致横向低温冲击韧性的主要原因。     

铝硅焊片对异种铝合金电子束焊接焊缝组织性能的影响

采用电子束焊接技术,研究厚度为20 mm的AlCu0.5,AlSiCu,AlSi1三种高纯铝合金分别与6061铝合金的焊接效果。通过添加铝硅焊片来改善异种铝合金焊接的组织性能。对焊缝区域组织的分析表明,不同焊片添加量改变铝合金焊缝中的Si含量,从而对焊接的裂纹敏感性有显著的影响。当焊缝中Si含量在1%左右时容易产生裂纹缺陷,随着焊缝中Si含量的增高,焊缝中的裂纹逐渐减小,直至没有裂纹缺陷的产生。焊缝的硬度也随焊缝中Si含量的增高而变大。针对不同的高纯铝合金与6061的焊接,通过添加合适的铝硅焊片,能获取组织性能优异的焊缝。     

X80钢焊缝再热后的组织与性能

针对西气东输二线X80高强度高韧性厚壁管线钢管双面埋弧焊接工艺特点,采用Gleeble1500热模拟试验和实物焊接试验,研究分析了内焊缝(一次焊缝)受到外焊(二次焊接)热循环后组织与性能变化情况。通过SEM、光学显微镜等进行了微观组织分析并做力学性能测试。结果表明,一次焊缝受到二次焊接热循环峰值温度在(α+γ)两相区范围时发生脆化,韧性降低22%;而一次焊缝在外焊二次热输入为20 kJ/cm时,冲击韧性最好;二次焊接在一次焊缝中形成了焊接临界粗晶区(WICHAZ),呈现粗大的条状铁素体,板条间为排列成行M-A组元或渗碳体,硬度由212HV5迅速增加到261HV5,韧性也随之变差。     

Microstructure and Tensile Properties of Dissimilar Weld Joint Between Alloy 800 and Buttered Grade 91

Metallurgical and Materials Transactions A - Microstructure and tensile properties of dissimilar weld joint (DWJ) between Alloy 800 and ‘IN82 buttered’ Grade 91 (Gr. 91), fabricated...     

Mn对2205双相不锈钢耐点蚀性能的影响

研究锰元素对2205双相不锈钢耐点蚀性能的影响,锰质量分数的变化范围为0. 93%～1. 26%.分别采用化学腐蚀法、动电位极化法研究双相不锈钢2205的耐腐蚀性能,采用夹杂物自动分析技术研究锰对钢中夹杂物种类及数量的影响,通过扫描电镜、能谱及夹杂物原位分析法观察化学腐蚀及电化学腐蚀前后钢中夹杂物及其周围钢基体的变化情况.采用电感耦合等离子体发光光谱测定腐蚀产物的成分.研究结果表明,不同类型的夹杂物对耐腐蚀性能的影响不同,(Mn、Si)氧化物以及(Mn、Si、Cr)氧硫化物在腐蚀液中更易溶解进而促进腐蚀,而(Cr、Mn、Al)氧化物却很稳定.锰的加入会促进钢中(Cr、Mn、Al)夹杂的析出,此类夹杂物不仅自身很容易被含Cl离子的溶液腐蚀,而且作为点蚀的起始点,促进了点蚀坑的形成,加快了基体腐蚀,最终导致不锈钢耐点蚀性能的下降.     

微合金钢焊缝金属中夹杂物的研究

通过对微合金钢焊缝金属中夹杂物的研究发现 :夹杂物数量在焊缝中心最多 ,而在熔合线附近最少 ;随着焊接热输入的增加 ,夹杂物平均尺寸增大。约有 6 0 %夹杂物的平均尺寸都小于 0 .6 μm,而大于 1.0 μm的不足 10 %。夹杂物是由多个物相组成的复合物 ,组成夹杂物的物质 :Mn O2 、3Mn O· Al2 O3· Si O2 、Ti N、Ca O· 2 Al2 O3、Si O2 、Ca O· 2 Ti O2 和 θ- Al2 O3等。提供针状铁素体 (AF)形核的夹杂物尺寸约 93 %以上都集中在 0 .2～ 0 .6 μm范围内     

热处理工艺对S355钢焊缝夹杂物晶体结构的影响

采用活性气体保护焊工艺对S355低合金钢板进行焊接,分析了焊后热处理制度对焊缝夹杂物晶体结构的影响.结果表明,焊态条件下焊缝金属内的夹杂物为非晶态结构.经900℃保温2h正火处理后,焊缝金属内的非晶态夹杂物转变为晶态,此晶态夹杂物包含Fe1.1Mn3.9C2,MnS和Mn2.5Fe2.5SiC相.正火温度升高到1000℃时,夹杂物中的Mn2.5Fe2.5SiC相消失,同时非晶相再次出现.正火温度进一步提高到1100℃时,夹杂物中仅剩下MnS和非晶相.