Effect of Autogenous Arc Welding Processes on Tensile and Impact Properties of Ferritic Stainless Steel Joints

 The effect of autogeneous arc welding processes on tensile and impact properties of ferritic stainless steel conformed to AISI 409M grade is studied. Rolled plates of 4 mm thickness have been used as the base material for preparing single pass butt welded joints. Tensile and impact properties, microhardness, microstructure, and fracture surface morphology of continuous current gas tungsten arc welding (CCGTAW), pulsed current gas tungsten arc welding (PCGTAW), and plasma arc welding (PAW) joints are evaluated and the results are compared. It is found that the PAW joints of ferritic stainless steel show superior tensile and impact properties when compared with CCGTAW and PCGTAW joints, and this is mainly due to lower heat input, finer fusion zone grain diameter, and higher fusion zone hardness.     

Evaluation of Microstructure and Mechanical Properties of Laser Beam Welded AISI 409M Grade Ferritic Stainless Steel

 The microstructure analysis and mechanical properties evaluation of laser beam welded AISI 409M ferritic stainless steel joints are investigated. Single pass autogeneous welds free of volumetric defects were produced at a welding speed of 3000 mm/min. The joints were subjected to optical microscope, scanning electron fractographe, microhardness, transverse and longitudinal tensile, bend and charpy impact toughness testing. The coarse ferrite grains in the base metal were changed into dendritic grains as a result of rapid solidification of laser beam welds. Tensile testing indicates overmatching of the weld metal is relative to the base metal. The joints also exhibited acceptable impact toughness and bend strength properties.     

Effect of Welding Processes and Consumables on Tensile and Impact Properties of High Strength Quenched and Tempered Steel Joints

Quenched and tempered steels are prone to hydrogen induced cracking in the heat affected zone after welding. The use of austenitic stainless steel consumables to weld the above steel was the only available remedy because of higher solubility for hydrogen in austenitic phase. In this investigation, an attempt was made to determine a suitable consumable to replace expensive austenitic consumables. Two different consumables, namely, austenitie stain less steel and low hydrogen ferritic steel, were used to fabricate the joints by shielded metal are welding （SMAW） and flux cored arc welding （FCAW） processes. The joints fabricated by using low hydrogen ferritic steel consumables showed superior transverse tensile properties, whereas joints fabricated by using austenitic stainless steel consumables exhibited better impact toughness, irrespective of the welding process used. The SMAW joints exhibited superior mechanical and impact properties, irrespective of the consumables used, than their FCAW counterparts.     

Effect of welding processes on tensile, impact, hardness and microstructure of AISI 409M ferritic stainless joints fabricated using duplex stainless steel filler metal

 The present investigation is aimed at to study the effect of welding processes such as shielded metal arc welding, gas metal arc welding and gas tungsten arc welding on tensile and impact properties of the ferritic stainless steel conforming to AISI 409M grade. Rolled plates of 4 mm thickness were used as the base material for preparing single pass butt welded joints. Tensile and impact properties, micro hardness, microstructure and fracture surface morphology of the welded joints have been evaluated and the results are compared. From this investigation, it is found that gas tungsten arc welded joints of ferritic stainless steel showed superior tensile and impact properties compared with shielded metal arc and gas metal arc welded joints and this is mainly due to the presence of finer grains in fusion zone and heat affected zone.     

Comparison of Friction Stir and Gas Tungsten Arc Weldments of Modified 12 wt.% Cr Ferritic Stainless Steel

This paper presents the comparative evaluation of microstructural features and mechanical properties of a friction stir welded (solid‐state) and gas tungsten arc welded (fusion weld) 409 M grade ferritic stainless steel joints. Optical microscopy, microhardness, transverse tensile and impact tests were performed. The coarser ferrite grains in the base material are changed to very fine grains consisting of a duplex structure of ferrite and martensite due to the rapid cooling rate and high strain induced by severe plastic deformation caused by frictional stirring. On the other hand, grain growth was observed in the fusion zone as well as heat affected zone of the gas tungsten arc welded joint resulting in deterioration of mechanical properties.     

12%Cr铁素体不锈钢不同化学成分对接头韧性的影响

利用光学显微镜和扫描电镜,对两种成分的超低碳氮12%Cr铁素体不锈钢焊接热影响组织及冲击断口形貌进行观察与分析,提出提高焊接接头冲击韧性的措施,即必须控制其高温热影响区组织的晶粒尺寸;利用分布在晶界上的第二相组织抑制基体晶粒的长大;降低基体组织中的C、N等间隙原子的含量;采用合适的焊接工艺参数控制接头粗晶区的宽度等,综合优化工艺下可使焊接接头最薄弱区的冲击功在-40℃下提高92%。     

铌、钛对445M铁素体不锈钢韧性的影响

 通过真空冶炼、锻造、热轧和不同固溶处理温度试验制备出含有不同微合金元素含量的445M铁素体不锈钢，结合其冲击试验，运用金相显微镜、扫描电子显微镜及能谱仪等分析方法，探讨了微合金化对其韧性的影响。结果表明：化学元素铌和钛的加入，在晶粒内部和晶界上形成了TiN、NbC和(Nb，Ti)(C，N)析出相，稳定了钢中的碳、氮元素，防止由铬的碳氮化物析出而引起的晶间腐蚀，但对钢的冲击韧性有一定影响。采用单铌作为稳定化元素钢的冲击韧性优于单钛稳定钢；添加少量的钛，采用Nb+Ti双稳定钢，也可获得优异的冲击韧性，并且能够降低生产成本。     

Influence of FCA Welding Process Parameters on Distortion of 409M Stainless Steel for Rail Coach Building

The influence of flux cored arc welding (FCAW) process parameters such as welding current, travel speed, voltage and CO2 shielding gas flow rate on bowing distortion of 409M ferritic stainless steel sheets of 2 mm in thickness was discussed. The bowing distortions of the welded plates were measured using a simple device called profile tracer. An experimental regression equation was developed to predict the bowing distortion and with this equation, it is easy to select optimized process parameters to achieve minimum bowing distortion. It is revealed that the FCAW process parameters have significant influence on bead profile and the bowing distortion.     

钒对18Cr-2Mo铁素体不锈钢性能的影响

 利用Thermo-Calc热力学软件、扫描电子显微镜、X射线衍射仪及透射电镜等分析方法,研究了不同钒含量对单铌稳定18Cr-2Mo铁素体不锈钢微观组织、力学性能和点腐蚀性能的影响规律。结果表明：添加钒后的析出相主要是NbC和VN,弥散分布于晶内和晶界,其中NbC的尺寸为100~250nm;随着钒含量的增加,试验钢的晶粒尺寸及屈服强度变化不明显,而冲击韧性及点腐蚀性能逐步得到改善和提高,当wV=0.36%时,钢的韧脆?湮露扔稍嫉?10℃下降至-30℃,点腐蚀电位由0.38V提高至0.42V。     

钛元素的添加对超纯铁素体不锈钢焊缝区等轴晶组织的影响

等轴晶组织对于铁素体不锈钢焊缝区的力学性能,特别是韧性、延伸率等影响很大。总结了在铁素体不锈钢焊缝中等轴晶的形核机理。对于439超纯铁素体,加入钛元素可以在焊缝凝固前的熔融状态析出TiN的析出相,有利于钨极氩弧焊(TIG)的焊缝等轴晶的形成。在短暂的焊接过程中,可以通过控制铁素体不锈钢Ti和N的浓度积以及N的含量等来控制母材TiN最初的析出形态、析出数量;同时,通过Ti和N的合适匹配以及合适的焊接工艺参数保证焊缝区的温度梯度,这些都是焊缝区等轴晶比例的必要控制因素。     

Nb对0Cr11铁素体不锈钢组织和性能的影响

 铁素体不锈钢与奥氏体不锈钢相比具有成本低、热膨胀系数低和耐应力腐蚀等优点,所以被广泛应用到汽车排气系统、家用电器和建筑等领域。研究了不同的Nb含量对铁素体不锈钢显微组织和力学性能的影响。研究结果表明：Nb有细化晶粒的作用,随着Nb含量的增加,晶粒的平均尺寸减小;由于合金元素Nb和Ti的加入,形成了TiN、NbC 和 Fe2Nb析出相,其透射电镜观察结果与Thermal calc计算结果一致;材料的抗拉强度和显微硬度随着Nb含量的增加而增加,这是由于Nb的固溶强化和析出强化共同作用的结果。     

Evaluation of Zero and Sub-zero Temperature Tensile and Impact Properties of Quenched and Tempered Steel Weldments

Combat vehicles using armour grade quenched and tempered(QT)steel are needed to be operated under different climatic conditions.However,the properties meeting the room temperature test conditions may not necessarily be required to meet the low temperature operating conditions.The influences of shielded metal arc welding(SMAW)process,flux cored arc welding(FCAW)processes and test temperatures below room temperature up to-60 ℃ on tensile and impact toughness properties of armour grade QT steel welds were reported.The tensile and impact properties of the joints showed incremental trend with respect to the decrement in test temperature up to-40℃irrespective of the welding processes used.The increment in tensile and impact properties of SMAW and FCAW joints subjected to the low temperature environment is due to plastic strain-induced phase transformation of retained austenite into martensite phase.Among the two processes,SMAW process welded joint showed better tensile and impact properties than its FCAW counterpart joints.     

12%Cr铁素体不锈钢焊接接头组织及韧性研究

对四种不同成分的12%Cr铁素体不锈钢做了焊接性试验。分析焊接接头的组织,测量了焊接接头的低温冲击功。试验结果表明,随着碳含量的增加,焊接粗晶区组织由单相铁素体逐渐转变成以马氏体为主,粗晶区宽度变窄,晶粒尺寸变小。细晶区组织以马氏体为主,组织细小均匀。熔合线处和热影响区的低温冲击功相比母材均显著降低。断裂路径分析结果表明,窄的粗晶区宽度和小的晶粒尺寸使断裂路径经过更多的奥氏体焊缝区,提高了整体的冲击韧性。     

TCS不锈钢焊接HAZ特征及其力学性能研究

 TCS不锈钢是一种低铬的经济型铁素体不锈钢,因为热循环的影响焊接HAZ性能成为制约其广泛应用的关键。对其焊接HAZ的组织演化以及各区域热循环特征参数进行了详细研究,并根据测定的参数利用热模拟技术对焊接HAZ的力学性能进行了研究。结果表明：焊接HAZ的组织由单一铁素体基体变成铁素体加马氏体组织,其强度比母材有所提高,屈强比增大。与母材相比,细晶区韧性变化较小,可以保持在较高的水平;虽然混合晶区的韧性保持在较高水平,但不稳定;而粗晶区韧性却急剧下降。     

终轧温度对超纯铁素体不锈钢组织、织构及成形性能的影响

研究了终轧温度对铌、钛双稳定化超纯Cr17铁素体不锈钢的组织演变、织构演变及成形性能的影响。研究结果表明,降低终轧温度能有效细化、均匀化热轧及退火组织。降低终轧温度能增强冷轧退火板的γ纤维再结晶织构、减轻偏离{111}121组分的程度。降低终轧温度是提高r值、降低Δr值、改善冷轧退火板成形性能的有效手段。     

Microstructure,Tensile and Impact Toughness Properties of Friction Stir Welded Mild Steel

 Microstructure, tensile and impact toughness properties and fracture location of friction stir welded AISI 1018 mild steel are revealed in this paper. The 5 mm thick AISI 1018 mild steel plates were friction stir welded with tool rotational speed of 1000 rpm and welding speed of 50 mm/min with tungsten base alloy tool. Tensile strength of stir zone is higher (8%) when compared to the base metal. This may be due to the formation of finer grains in the weld nugget region under the stirring action of the rotating tool. The ductility and impact toughness of the joints are decreased compared to the base metal and this is due to the inclusion of tungsten particles in the weld region.     

热处理工艺对12%Cr铁素体不锈钢组织性能的影响

以12%Cr铁素体不锈钢为研究对象,研究了不同退火方式、退火工艺对12%Cr铁素体不锈钢热轧板和冷轧板组织、力学性能、耐腐蚀性能、成形性能的影响。结果显示,12%Cr铁素体不锈钢高温下存在铁素体—奥氏体相变过程,在双相区退火快冷后有马氏体组织生成。通过在热退过程中引入奥氏体相变和马氏体相变,可以显著细化最终产品晶粒,提高最终冷轧产品的强度、硬度,同时保持材料耐腐蚀性能不变。该工艺生产的产品可以适用于高强度的应用场合,打破了传统12%Cr铁素体不锈钢热轧后只能采用罩式炉退火的束缚,针对产品的最终用途可以采用不同的退火方式和退火工艺进行生产。