Shielded metal arc welding of cemented carbide to carbon steel

Electrode ENiFe-C1 and E4303 were selected to join the cemented carbide WC-20Co and carbon steel 45 by shielded metal arc welding process. Microstructure and bending property of the corresponding joints were analyzed. The results showed that the carbon steel electrode E4303 had no proper metallurgy condition for the arc welding of cemented carbide and carbon steel. The C and Ni content of the cast iron electrode ENiFe-C1 could meet the condition of preventing the formation ofη carbide,which was suit to the arc welding of cemented carbide and carbon steel,but the operation parameters needed to be optimized to minimize the slag inclusion. The alloy WC-20Co which did not fit for cold arc welding,by adopting the measure of being preheated at 723 K for 1 h before welding,and being kept at 723 K for 3 h after welding then followed furnace cooling could avoid the happening of crack in the WC-20Co base metal.

Tensile and Impact Properties of Shielded Metal Arc Welded AISI 409M Ferritic Stainless Steel Joints

The present study is concerned with the effect of filler metals such as austenitic stainless steel, ferritic stainless steel and duplex stainless steel 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, microhardness, microstructure and fracture surface morphology of the joints fabricated by austenitic stainless steel, ferritic stainless steel and duplex stainless steel filler metals were evaluated and the results were reported. From this investigation, it is found that the joints fabricated by duplex stainless steel filler metal showed higher tensile strength and hardness compared to the joints fabricated by austenitic and ferritic stainless steel filler metals. Joints fabricated by austenitic stainless steel filler metal exhibited higher ductility and impact toughness compared with the joints fabricated by ferritic stainless steel and duplex stainless steel filler metals.

Microstructure and pitting corrosion of shielded metal arc welded high nitrogen stainless steel

The present work is aimed at studying the microstructure and pitting corrosion behaviour of shielded metal arc welded high nitrogen steel made of Cromang-N electrode. Basis for selecting this electrode is to increase the solubility of nitrogen in weld metal due to high chromium and manganese content. Microscopic studies were carried out using optical microscopy(OM) and field emission scanning electron microscopy(FESEM). Energy back scattered diffraction(EBSD) method was used to determine the phase analysis, grain size and orientation image mapping. Potentio-dynamic polarization testing was carried out to study the pitting corrosion resistance in aerated 3.5% NaCl environment using a GillAC electrochemical system. The investigation results showed that the selected Cr-Mn-N type electrode resulted in a maximum reduction in delta-ferrite and improvement in pitting corrosion resistance of the weld zone was attributed to the coarse austenite grains owing to the reduction in active sites of the austenite/delta ferrite interface and the decrease in galvanic interaction between austenite and delta-ferrite.

EFFECT OF Fe_2O_3 ON WELDING TECHNOLOGY AND MECHANICAL PROPERTIES OF WELD METAL DEPOSITED BY SELF-SHIELDED FLUX CORED WIRE

Five experimental self-shielded flux cored wires are fabricated withdifferent amount of Fe_2O_3 in the flux. The effect of Fe_2O_3 on welding technology and mechanicalproperties of weld metals deposited by these wires are studied. The results show that with theincrease of Fe_2O_3 in the mix, the melting point of the pretreated mix is increased. LiBaF_3 andBaFe_(12)O_(19), which are very low in inherent moisture, are formed after the pretreatment. Themechanical properties are evaluated to the weld metals. The low temperature notch toughness of theweld metals is increased linearly with the Fe_2O_3 content in the flux due to the balance betweenFe_2O_3 and residual Al in the weld metal. The optimum Fe_2O_3 content in flux is 2.5 percent approx3.5 percent.

Formation Mechanism of Inclusion in Self-Shielded Flux Cored Arc Welds

The formation mechanism of inclusion in welds with different aluminum contents was determined based on thermodynamic equilibrium in self-shielded flux cored arc welds.Inclusions in welds were systematically studied by optical microscopy,scanning microscopy and image analyzer.The results show that the average size and the contamination rate of inclusions in low-aluminum weld are lower than those in high-aluminum weld.Highly faceted AlN inclusions with big size in the high-aluminum weld are more than those in low-aluminum weld.As a result,the low temperature impact toughness of low-aluminum weld is higher than that of high-aluminum weld.Finally,the thermodynamic analysis indicates that thermodynamic result agrees with the experimental data.

基于Simufact.Welding的空间框架结构单层单道焊和两层三道焊数值模拟

使用焊接专用软件Simufact.Welding模拟了Q345空间框架结构的二氧化碳气体保护焊的单层单道和两层三道过程,得到了框架结构的等效应力和总变形量。结果表明：这两种焊接方法的等效应力和总变形分布极为相似,但单层单道焊缝的等效应力和总变形比两层三道焊缝小,两层三道焊的应力和变形分布区域更大。

Welding of nickel free high nitrogen stainless steel: Microstructure and mechanical properties

High nitrogen stainless steel(HNS) is a nickel free austenitic stainless steel that is used as a structural component in defence applications for manufacturing battle tanks as a replacement of the existing armour grade steel owing to its low cost, excellent mechanical properties and better corrosion resistance.Conventional fusion welding causes problems like nitrogen desorption, solidification cracking in weld zone, liquation cracking in heat affected zone, nitrogen induced porosity and poor mechanical properties.The above problems can be overcome by proper selection and procedure of joining process. In the present work, an attempt has been made to correlate the microstructural changes with mechanical properties of fusion and solid state welds of high nitrogen steel. Shielded metal arc welding(SMAW), gas tungsten arc welding(GTAW), electron beam welding(EBW) and friction stir welding(FSW) processes were used in the present work. Optical microscopy, scanning electron microscopy and electron backscatter diffraction were used to characterize microstructural changes. Hardness, tensile and bend tests were performed to evaluate the mechanical properties of welds. The results of the present investigation established that fully austenitic dendritic structure was found in welds of SMAW. Reverted austenite pools in the martensite matrix in weld zone and unmixed zones near the fusion boundary were observed in GTA welds. Discontinuous ferrite network in austenite matrix was observed in electron beam welds.Fine recrystallized austenite grain structure was observed in the nugget zone of friction stir welds.Improved mechanical properties are obtained in friction stir welds when compared to fusion welds. This is attributed to the refined microstructure consisting of equiaxed and homogenous austenite grains.

Effect of welding processes on mechanical and microstructural characteristics of high strength low alloy naval grade steel joints

Naval grade high strength low alloy(HSLA) steels can be easily welded by all types of fusion welding processes. However, fusion welding of these steels leads to the problems such as cold cracking, residual stress, distortion and fatigue damage. These problems can be eliminated by solid state welding process such as friction stir welding(FSW). In this investigation, a comparative evaluation of mechanical(tensile, impact,hardness) properties and microstructural features of shielded metal arc(SMA), gas metal arc(GMA) and friction stir welded(FSW) naval grade HSLA steel joints was carried out. It was found that the use of FSW process eliminated the problems related to fusion welding processes and also resulted in the superior mechanical properties compared to GMA and SMA welded joints.

Influence of shielding gas on the mechanical and metallurgical properties of DP-GMA-welded 5083-H321 aluminum alloy

In the present research, 6-mm-thick 5083-H321 aluminum alloy was joined by the double-pulsed gas metal arc welding （DP-GMAW） process. The objective was to investigate the influence of the shielding gas composition on the microstructure and properties of GMA welds. A macrostructural study indicated that the addition of nitrogen and oxygen to the argon shielding gas resulted in better weld penetration. Furthermore, the tensile strength and bending strength of the welds were improved when oxygen and nitrogen （at concentrations as high as approximately 0. 1vol%） were added to the shielding gas; however, these properties were adversely affected when the oxygen and nitrogen contents were increased further. This behavior was attributed to the formation of excessive brown and black oxide films on the bead surface, the formation of intermetallic compounds in the weld metal, and the formation of thicker oxide layers on the bead surface with increasing nitrogen and oxygen contents in the argon-based shielding gas. Analysis by energy-dispersive X-ray spectroscopy revealed that most of these compounds are nitrides or oxides.

Studies on Effects of Welding Parameters on the Mechanical Properties of Welded Low-Carbon Steel

In this work, the effect of heat input on the mechanical properties of low-carbon steel was studied using two welding processes: Oxy-Acetylene Welding (OAW) and Shielded Metal Arc Welding (SMAW). Two different edge preparations on a specific size, 10-mm thick low-carbon steel, with the following welding parameters: dual welding voltage of 100 V and 220 V, various welding currents at 100, 120, and 150 Amperes and different mild steel electrode gauges of 10 and 12 were investigated. The tensile strength, hardness and impact strength of the welded joint were carried out and it was discovered that the tensile strength and hardness reduce with the increase in heat input into the weld. However, the impact strength of the weldment increases with the increase in heat input. Besides it was also discovered that V-grooved edge preparation has better mechanical properties as compared with straight edge preparation under the same conditions. Microstructural examinations conducted revealed that the cooling rate in different media has significant effect on the microstructure of the weldment. Pearlite and ferrite were observed in the microstructure, but the proportion of ferrite to pearlite varied under different conditions.

Effect of welding processes and consumables on fatigue crack growth behaviour of armour grade quenched and tempered steel joints

Quenched and Tempered(Q&T) steels are widely used in the construction of military vehicles due to its high strength to weight ratio and high hardness. These steels are prone to hydrogen induced cracking(HIC) in the heat affected zone(HAZ) after welding. The use of austenitic stainless steel(ASS) consumables to weld the above steel was the only available remedy because of higher solubility for hydrogen in austenitic phase. The use of stainless steel consumables for a non-stainless steel base metal is not economical. Hence, alternate consumables for welding Q&T steels and their vulnerability to HIC need to be explored. Recent studies proved that low hydrogen ferritic steel(LHF) consumables can be used to weld Q&T steels, which can give very low hydrogen levels in the weld deposits. The use of ASS and LHF consumables will lead to distinct microstructures in their respective welds. This microstructural heterogeneity will have a drastic influence in the fatigue crack growth resistance of armour grade Q&T steel welds. Hence, in this investigation an attempt has been made to study the influence of welding consumables and welding processes on fatigue crack growth behaviour of armour grade Q&T Steel joints. Shielded metal arc welding(SMAW) and Flux cored arc welding(FCAW) were used for fabrication of joints using ASS and LHF consumables. The joints fabricated by SMAW process using LHF consumable exhibited superior fatigue crack growth resistance than all other joints.

焊丝成分对超高强装甲钢焊接接头组织与性能的影响

利用气体保护电弧焊工艺完成了4.5 mm和9.0 mm超高强装甲钢的焊接,研究了焊丝(MG70S-6和ER307Si焊丝)成分对接头组织与性能的影响,通过光学显微镜(OM)、扫描电子显微镜(SEM)、能谱分析(EDS)、X射线衍射(XRD)等表征方法对焊接接头各区域进行微观组织和物相结构的分析,并测试了接头的硬度分布、拉伸性能和冲击韧性。结果表明,焊接接头成形质量良好,无明显未熔合、气孔、裂纹等缺陷,焊缝区组织为片状马氏体、针状铁素体和少量粒状贝氏体,完全淬火区组织为马氏体和贝氏体,不完全淬火区组织为马氏体和铁素体,回火区析出网状渗碳体。焊接接头的热影响区软化现象较为明显,接头难以达到与母材等强,断裂主要发生在焊缝区,呈现出脆性断裂特征。采用ER307Si焊丝焊接的9.0 mm装甲钢接头的焊缝室温冲击功达到94 J,完全满足使用要求。

基于电弧光谱的核电堵管TIG焊接质量在线监测

为了实现受操作空间限制和辐射环境下,高温气冷堆蒸汽发生器传热管道堵管钨极惰性气体保护电弧焊(tungsten inert gas welding, TIG)的质量监测,搭建了一套基于光纤光谱仪的TIG焊接过程实时监测系统,用于核电传热管道堵管TIG焊接熔深监测.试验研究采用该系统采集电弧光谱,利用主成分分析法获取不同焊缝熔深的光谱主成分特征,创新性提出了一种ATT-L2R-BiLSTM深度学习模型,实现了堵管TIG焊接过程中焊缝熔深的分类识别.结果表明,实验室条件下模型准确率可达92.61%,比Bi-LSTM网络准确率提高5.11%,该模型在核电蒸汽发生器堵管验证平台进行了测试和验证,准确率达到99.26%,最终,实现了光谱信息不完备下TIG焊接质量特征深度挖掘,以及TIG焊接熔深的精准评估.

钢结构制作工艺流程及焊接技术

针对钢结构制作工艺流程及焊接技术,结合工程实践,分析了钢结构的特点,并深入研究了钢结构制作工艺,包括钢结构的一般制作流程、H型钢以及圆管钢构件的加工工艺,同时还探讨了钢结构焊接技术,包括焊条电弧焊、埋弧焊、气体保护焊以及特殊的焊接工艺。

焊丝成分对5454-H32铝合金焊缝组织与性能的影响

以使用脉冲弧熔化极气体保护焊焊接的3.2 mm厚5454-H32铝合金对接接头为研究对象,使用光学显微镜、SEM、EDS和显微硬度计,分析2种接头的显微组织、析出相形态、分布和成分及显微硬度,测试接头的力学性能。分析结果表明,使用ER5356焊丝焊接的接头各项性能均优于使用ER4043焊丝焊接的接头性能。

Weld Shape Variation and Electrode Oxidation Behavior under Ar-(Ar-CO_2) Double Shielded GTA Welding

Double shielded gas tungsten arc welding （GTAW, also known as tungsten inert gas （TIG） welding） of an SUS304 stainless steel with pure inert argon as the inner layer shielding and the At-CO2 or CO2 active gas as the out layer shielding was proposed in this study to investigate its effect on the tungsten electrode protection and the weld shape variation. The experimental results showed that the inner inert argon gas can successfully prevent the outer layer active gas from contacting and oxidizing the tungsten electrode during the welding process. Active gas, carbon dioxide, in the outer layer shielding is decomposed in the arc and dissolves in the liquid pool, which effectively adjusts the active element, oxygen, content in the weld metal. When the weld metal oxygen content is over 70×10-6, the surface-tension induced Marangoni convection changes from outward into inward, and the weld shape varies from a wide shallow one to a narrow deep one. The effect of the inner layer gas flow rate on the weld bead morphology and the weld shape was investigated systematically. The results show that when the flow rate of the inner argon shielding gas is too low, the weld bead is easily oxidized and the weld shape is wide and shallow. A heavy continuous oxide layer on the liquid pool is a barrier to the liquid pool movement.

Comparative Study on Processing Property Between CWW CO_2 Gas Shielded Welding and SAW

Cable welding wire（CWW）CO2gas shielded welding is an innovative process arc welding with high efficiency,high quality and low consumption,in which cable wire is used as consumable electrode.CWW CO2gas shielded welding and submerged arc welding（SAW）are used for contrast studies on processing property of high strength steel A36used in ship structure.The results show that the shapes of weld seam,using CWW CO2gas shielded welding and SAW,are good and no weld defect such as air hole,flaw,slag inclusion,incomplete fusion,lack of penetration and so on are found in the weld seam.Because the rotating of arc during CWW CO2gas shielded welding process has a strong stirring effect on molten pool,the grain in the heat affected zone（HAZ）of the joints,using CWW CO2 gas shielded welding,is small.Tensile failure positions of joints by CWW CO2gas shielded welding and SAW are all in the base metal,but tensile strength of CWW CO2gas shielded welding joint is higher than that of SAW joint by an average of 2.3%.The average impact energy of HAZ,using CWW CO2gas shielded welding and SAW,is almost equal,but the average impact energy of the weld seam using CWW CO2gas shielded welding is increased by 6%,and the average impact energy of the fusion line is increased by 7%.The 180°bending tests for the joints of CWW CO2 gas shielded welding and SAW are all qualified,and the joints hardness is all less than HV 355,but hardness of CWW CO2gas shielded welding wire welding joint near the fusion line is obviously lower.It can be concluded that the properties of CWW CO2gas shielded welding are better than those of the SAW joint,and CWW CO2gas shielded welding is suitable for welding high strength steel A36used in ship structure.

Metallurgical characteristics of armour steel welded joints used for combat vehicle construction

Austenitic stainless steel(ASS) and High nickel steel(HNS) welding consumables are being used for welding Q&T steels, as they have higher solubility for hydrogen in austenitic phase, to avoid hydrogen induced cracking(HIC) but they are very expensive. In recent years, the developments of low hydrogen ferritic steel(LHF) consumables that contain no hygroscopic compounds are utilized for welding Q&T steels. Heat affected zone(HAZ) softening is another critical issue during welding of armour grade Q&T steels and it depends on the welding process employed and the weld thermal cycle. In this investigation an attempt has been made to study the influence of welding consumables and welding processes on metallurgical characteristics of armour grade Q&T steel joints by various metallurgical characterization procedures. Shielded metal arc welding(SMAW) and flux cored arc welding(FCAW) processes were used for making welds using ASS, LHF and HNS welding consumables. The joints fabricated by using LHF consumables offered lower degree of HAZ softening and there is no evidence of HIC in the joints fabricated using LHF consumables.

Effect of Notch Location on Fatigue Life Prediction of Strength Mismatched HSLA Steel Weldments

Welding of high strength low alloy steels (HSLA) involves usage of low, even and high strength filler materials (electrodes) than the parent material depending on the application of the welded structures and the availability of the filler material. In the present investigation, the fatigue crack growth behaviour of weld metal (WM) and heat affected zone (HAZ) regions of under matched (UM), equal matched (EM) and over matched (OM) joints has been studied. The base material used in this investigation is HSLA-80 steel of weldable grade. Shielded metal arc welding (SMAW) process has been used to fabricate the butt joints. Centre cracked tension (CCT) specimen has been used to evaluate the fatigue crack growth behaviour of the welded joints. Fatigue crack growth experiments have been conducted using servo hydraulic controlled fatigue testing machine at constant amplitude loading (R=0).A method has been proposed to predict the fatigue life of HSLA steel welds using fracture mechanics approach by incorporating influences of mismatch ratio (MMR) and notch location.