Effect of oxygen-containing additives on weld penetration in self-shielded flux cored arc welding

The effect of Fe203 and Liz CO3 additives in flux core on the weld metal oxygen content and weld penetration in self-shielded flux cored arc welding were studied schematically. The result shows that the oxygen content in the weld metal and weld penetration both increased with the Fe203 addition increased in the range of 5 wt. % to 20 wt. %. The oxygen content in the weld metal was increased with the Li2CO3 addition increased in the range of 1 wt. % to 8 wt. %. However, the weld penetration decreased when Li2CO3 addition exceeding 4 wt. %. High-speed photographic images show that when Fe2O3 addition influx core exceeding 15 wt. %, droplet became excessively large, so that spatters were frequently generated in large numbers. In this study, Fe203 and Li2 CO3 in the amount of 11 wt. % and 4 wt. %, respectively, jointly added in the flux core can achieve a deeper weld penetration with sound usability characteristics.

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.

Research on the Mechanism of Penetration Increase by Flux in A-TIG Welding

The mechanism of penetration depth increased by activating flux in activating tungsten inert gas (A-TIG) weldingwas studied by measuring the distribution of trace element Bi in the weld and monitoring the change of arc voltageduring A-TIG welding of stainless steel 0Crl8Ni9 with fluxes SiO2 and TiO2. The results show that the mechanismof penetration depth in A-TIG welding depends on the sort of flux used. The weld pool convection after coating theflux SiO2 and flux TiO2 is changed inversely compared with convectional TIG welding without flux. The arc voltageis increased by flux SiO2 whilst flux TiO2 does not have effect on the arc voltage. The reason of penetration depthincrease for SiO2 is due to the constriction of arc plasma and the change of surface tension gradient. The increaseof weld penetration depth with TiO2 only ascribes to the change of surface tension gradient.

Effect of Submerged Arc Welding Flux Component on Softening Temperature

Based on simplex algorithm of optimal design, the multicomponent mixture regression model was used to investigate physical properties of submerged arc welding flux. The effect of complex interaction of seven components in agglomerated flux on softening temperature was analyzed. The results indicate that the interaction of MgO-TiO2-CaCOa-AI20a increases the softening temperature of flux, but the additions of CaF2 and ZrO2 can decrease the softening temperature.

Experimental Investigation on the Performance of Armour Grade Q&T Steel Joints Fabricated by Flux Cored Arc Welding with Low Hydrogen Ferritic Consumables

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） and softening 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 to avoid HIC because of higher solubility for hydrogen in austenitic phase. Recent studies revealed that low hydrogen ferritic （LHF） steel consumables can also be used to weld Q＆T steels, which can give very low hydrogen levels in the weld deposits and required resistance against cold cracking. Hence, in this investigation an attempt has been made to study the performance of armour grade Q＆T steel joints fabricated by flux cored arc welding with LHF steel consumables. Two different consumables namely （i） austenitic stainless steel and （ii） low hydrogen ferritic steel have been used to fabricate the joints by flux cored arc welding （FCAW） process. The joints fabricated by LHF consumable exhibited superior transverse tensile properties due to the presence of ferrite microstructure in weld metal. The joints fabricated by ASS consumable showed higher impact toughness due to the presence of austenitic phase in weld metal microstructure. The HAZ softening in coarse grain heat affected zone （CGHAZ） is less in the joints fabricated using LHF consumable due to the lower heat input involved during fabrication compared to the joints fabricated using ASS consumables.

Effect of activating flux on arc shape and arc voltage in tungsten inert gas welding

The effects of activating fluxes on welding arc were investigated. A special set of water-cooling system and stainless steel were used as parent material. During welding process, high-speed camera system and oscillograph were used for capturing instantaneous arc shape and arc voltage respectively. The experimental results indicate that the SiO2 flux can increase the arc voltage, while TiO2 has no this effect on arc voltage. Compared with conventional tungsten inert gas welding (C-TIG), it is found that the arc shape of A-TIG welding used with the SiO2 flux has changed obviously.

Study on arc characteristics and behavior of metal transfer in pulse current flux-cored arc welding of mild steel

The variation in arc characteristics and behavior of metal transfer with the change in pulse parameters has been studied by high speed video camera during pulse current flux-cored arc weld deposition.A comparative study of similar nature has also been carried out during flux-cored arc weld deposition in globular and spray transfer modes.The effect of pulse parameters has been studied by considering their mean current and arc voltage.The arc characteristics studied by its root diameter,projected diameter and length,and the behavior of metal transfer noted by the metal transfer model and the droplet diameter have been found to vary significantly with the pulse parameters.The observation may help in understanding the arc characteristics with respect to the variation in pulse parameters which may be beneficial in using pulse current FCAW to produce desired weld quality.

Arc Characteristic and Metal Transfer of Pulse Current Horizontal Flux-Cored Arc Welding

In this work, we utilized high-speed video photography to investigate the arc characteristics, metal transfer behavior, and welding spatter of the pulse-current flux-cored arc welding(P-FCAW) process in the horizontal position. The results indicate the presence of a stable ‘‘flux pole'' during both the pulse-on and pulse-off periods when the mean current ranged from 140 to 170 A. The existence of this ‘‘flux pole'' was beneficial for droplet transfer in the‘‘axial droplet transfer'' mode. With respect to welding spatter, with an increase in the welding current, we observed three kinds of spatter—explosive spatter,rebounded droplet spatter, and scattering spatter. With an increase in the pulse current from 310.6 to 345.6 A, the deflection of the arc reduced from 30.4° to 16.6°, which positively influenced the arc rigidity, particularly in the horizontal position.

Cold Cracking of Flux Cored Arc Welded Armour Grade High Strength Steel Weldments

In this investigation, an attempt has been made to study the influence of welding consumables on the factors that influence cold cracking of armour grade quenched and tempered （Q＆.T） steel welds. Flux cored arc welding （FCAW） process were used making welds using austenitic stainless steel （ASS） and low hydrogen ferritic steel （LHF） consumables. The diffusible hydrogen levels in the weld metal of the ASS and LHF consumables were determined by mercury method. Residual stresses were evaluated using X-ray stress analyzer and implant test was carried out to study the cold cracking of the welds. Results indicate that ASS welds offer a greater resistance to cold cracking of armour grade Q＆T steel welds.

Weld formation and heating mechanism in ultra-narrow gap withconstricted arc by ultra-fine granular flux

Ultra-narrow gap welding （UNGW） process with high stabilization, reliability and without spatter can be achieved with constricted arc by molten slag wall, which is made from melted flux. The experiments are carried out by changing voltage under different currents. The results indicate voltage range being fit for UNGW is about 22 -31 V under the current range of 200 -320 A. With the increasing of voltage, weld formation of UNGW has the law of lack of fusion on sidewall, good weld and undercut in turn under a certain current. In addition, the action relationships among arc, molten slag wall and sidewalls can be improved by properly adjusting voltage and current of arc, which makes cathode spot properly distribute in ultra-narrow gap. Therefore, the effective control of weld formation of UNGW has been achieved.

Simulation of Weld Depth in A-TIG Welding with Unified Arc-electrode model

Calculations have been made for weld depths occurring for TIG welding activated by a flux over the surface of the weld pool. In this case, the flux introduces an electrically insulating layer over the outer regions of the weld pool surface. There is then an increase in the current density at the surface of the centre of the weld pool with a consequent increase in the J×B forces, which drive a strong convective flow of the molten metal downwards, tending to make a deep weld. For a flux which produces an insulating layer for all but a central region of radius 2 mm, the calculated weld depth is 7 mm, and an arc spot is predicted at the centre of the weld pool surface. As yet we have not resolved the reason for significant differences that exist between our measurements of weld depth and the theoretical predictions.

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.

Development of underwater wet welding experimental and divers training system

Compared to traditional welding methods, the underwater wet welding is special with many different characteristics due to the unique aqueous environment. It is conducted completely under water by divers and unique welding technology is required in the special operation environment. The operating levels of the divers are the key factor to acquire high quality welded joints. In this paper, an underwater wet welding experimental and divers training system is developed to serve divers training and conducting welding experiments. The system consists of life support system, signals real-time monitoring system and communicating system, etc. An underwater butt welding experiment based on welding electrodes is conducted, and the system works well. It proves that the system can guarantee divers welding safely and successfully and high quality weld seam is expected to be acquired.

Impact toughness variations of EH36 weld metal treated by CaF_(2)–SiO_(2)–MnO submerged arc welding flux

Fused ternary CaF_(2)–SiO_(2)–MnO fluxes have been manufactured and applied to join EH36 shipbuilding steel under high heat input submerged arc welding.Five fluxes have been designed to clarify the effect of MnO content in CaF_(2)–SiO_(2)–MnO flux on the impact toughness of the weld metal,with the added amount of MnO from 10 to 50 wt.%at the expense of CaF_(2).With the increase in MnO content,the Charpy impact energy increases first and then decreases,experiencing a maximum value at 30 wt.%MnO.Microstructure of the weld metals has also been studied to account for impact toughness variations.It has been demonstrated that the highest acicular ferrite volume fraction in the weld metal is achieved at 30 wt.%MnO,which is concurrent to the maximum value of Charpy impact energy.It is believed that the Mn and O content variations in the weld metal contribute synergistically to such an interesting phenomenon.

镍铜合金FCAW-G堆焊工艺研究

采用药芯焊丝气体保护焊(FCAW-G)对Q345R钢试板进行了镍铜合金N04400堆焊工艺评定,依照NB/T47014—2011《承压设备焊接工艺评定》要求对堆焊层的弯曲、化学成分及金相组织进行了检测。试验结果表明:采用80%Ar+20%CO_(2)混合保护气体,选用型号为ENiCu7T0-4的药芯焊丝进行过渡层及耐蚀层的堆焊,可以获得性能优良的耐蚀层,其化学成分满足标准要求,为镍铜合金实现高效堆焊提供了一种新的工艺参考。

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.

Research on porosity of underwater wet FCAW duplex stainless steel

To study the influence laws of welding parameters on weld porosity, underwater wet flux-cored arc welding （ FCAW） duplex stainless steel S32101 was carried out in a hyperbaric chamber, and the second-order multiple regression equation was established. The interactive effects of welding parameters on the porosity were analyzed by the three dimensional response surfaces and the contour plots. The results present that the interaction effect between water depth and voltage on the porosity is the most significant. Theoretically, a non-pores weld bead can be gained by reasonably matching these parameters with water depth less than 10 m. Always, the weld porosity reaches its peak value with a 7 mm/s welding speed.

Application of a sintered flux in UOE pipe manufacturing

Submerged arc welding is one of the main processes used in the manufacture of UOE welded pipes. It determines directly the quality of the pipes. In the submerged arc welding process, flux plays a very important role ;it not only affects the performance of the weld seam but also has a significant impact on the generation and prevention of weld defects. It is important to use a sintered flux for UOE pipe production. To meet the high-quality requirements on UOE welded pipes, the flux should be chosen such that it can resist high current and high speed, and help the weld achieve low H and O contents. At the same time, storage and management of a flux also require stringent monitoring. Domestic enterprises generally use sintered fluxes for the production of welded pipes.

焊剂片约束电弧焊接三明治板熔滴过渡与熔池波动研究

针对焊剂片约束电弧(FBCA)焊接高强钢三明治板熔池研究难点,采用侧边贴敷耐高温石英玻璃片方法,采集焊接动态过程信息,实现熔池边缘曲线的提取与特征参数的计算,研究不同参数下熔滴过渡模式及熔池边缘曲线波动情况,分析熔池振荡角与焊接稳定性及焊缝成形之间的关系。结果表明:不同参数下FBCA焊接存在短路过渡、粗滴过渡、排斥过渡、细滴过渡、射滴过渡、弧桥并存过渡六种过渡方式,对芯板内熔池边缘波动的影响依次减弱;随着熔池振荡角变化,熔池边缘曲线形状存在混合U形、深U形及浅U形,电弧燃烧稳定性依次增强;当焊接处于弧桥并存过渡模式、熔池边缘曲线为浅U形时,电弧稳定燃烧,电弧力作用均匀,焊接过程稳定,焊缝质量最好。