共查询到20条相似文献,搜索用时 40 毫秒
1.
Her-Yueh Huang 《Metallurgical and Materials Transactions A》2010,41(11):2829-2835
Using activating flux for gas tungsten arc welding (GTAW) to improve penetration capability is a well-established technique.
Argon is an inert gas and the one most widely used as a shielding gas for GTAW. For the most austenitic stainless steels,
pure argon does not provide adequate weld penetration. Argon–hydrogen mixtures give a more even heat input to the workpiece,
increasing the arc voltage, which tends to increase the volume of molten material in the weld pool as well as the weld depth-to-width
ratio. Great interest has been shown in the interaction between activating flux and the hydrogen concentration in an argon-based
shielding gas. In this study, the weld morphology, the arc profile, the retained delta ferrite content, the angular distortion,
and the microstructures were examined. The application of an activating flux combining argon and hydrogen for GTAW is important
in the industry. The results of this study are presented here. 相似文献
2.
In this study, the effects of heat input variation in gas tungsten arc welding (GTAW), on structure and mechanical properties of commercially C86300 (containing addition of 0.6 wt% silicon) weld joint were investigated. Following microstructural characterization of Base metal, GTAW has been performed at welding currents 50 and 60 A and flow rates of argon shielding gas (10, 14 and 18 l/min) using the same filler metal composition. Therefore six GTAW samples were performed with various welding specifications. By structural investigations and hardness profiles, effects of increasing heat input on increasing average grain size in weld zone, heat affected zone width, penetration depth and alloying element losses were indicated. However increasing heat input increases penetration depth and has a positive effect on hardness and strength of the joint. In considering wear application of this alloy castings and probable GTAW for them, pin-on-disc wear test was performed and revealed better wear resistance of weld metal in comparison with base metal. Hence the optimum values of welding current and argon flow rates (in GTAW with the same composition filler) was determined for this alloy. 相似文献
3.
R. T. C. Choo J. Szekely R. C. Westhoff 《Metallurgical and Materials Transactions B》1992,23(3):357-369
A mathematical formulation has been developed and computed results are presented describing the temperature profiles in gas
tungsten arc welding (GTAW) arcs and, hence, the net heat flux from the welding arc to the weld pool. The formulation consists
of the statement of Maxwell's equations, coupled to the Navier-Stokes equations and the differential thermal energy balance
equation. The theoretical predictions for the heat flux to the workpiece are in good agreement with experimental measurements
— for long arcs. The results of this work provide a fundamental basis for predicting the behavior of arc welding systems from
first principles. 相似文献
4.
Mechanism and optimization of oxide fluxes for deep penetration in gas tungsten arc welding 总被引:1,自引:0,他引:1
Shanping Lu Hidetoshi Fujii Hiroyuki Sugiyama Kiyoshi Nogi 《Metallurgical and Materials Transactions A》2003,34(9):1901-1907
Five single oxide fluxes—Cu2O, NiO, SiO2, CaO, and Al2O3—were used to investigate the effect of active flux on the depth/width ratio in SUS304 stainless steel. The flux quantity,
stability, and particlesize effect on the weld-pool shape and oxygen content in the weld after welding was studied systematically.
The results showed that the weld depth/width ratio initially increased, followed by a decrease with the increasing flux quantity
of the Cu2O, NiO, and SiO2 fluxes. The depth/width ratio is not sensitive to the CaO flux when the quantity is over 80×10−5 mol on the 5×0.1×50 mm slot. The Al2O3 flux has no effect on the penetration. The oxygen content dissolved in the weld plays an important role in altering the liquid-pool
surface-tension gradient and the weld penetration. The effective range of oxygen in the weld is between 70 and 300 ppm. A
too-high or too-low oxygen content in the weld pool does not increase the depth/width ratio. The decomposition of the flux
significantly depends on the flux stability and the particle size. Cu2O has a narrow effective flux-quantity range for the deep penetration, while the Al2O3 flux has no effect. The SiO2 flux with a small particle size (0.8 or 4 μm) is a highly recommended active flux for deep penetration in actual gas tungsten arc welding (GTAW) applications. 相似文献
5.
6.
对钽钢复合板的钽覆层采用敷设盖板的方式焊接,研究了直流氩弧焊与交流脉冲氩弧焊两种焊接工艺对钽钢复合板焊接质量的影响。结果表明,直流氩弧焊的焊接热影响区较宽,焊接熔深为1~1.5mm,在钢与过渡金属层之间形成了中间夹层;交流脉冲氩弧焊的焊接热影响区较窄,焊接熔深为0.5~1mm,复合板焊接质量较好。与直流氩弧焊相比,交流脉冲氩弧焊焊接参数范围较宽,对焊工技能的要求相对较低,可实现连续化生产,因此更适合用于钽钢复合板钽覆层的焊接。 相似文献
7.
In this article, Welding of AA2219 aluminium alloy using Gas tungsten arc welding process (GTAW) and evaluation of metallurgical, mechanical and corrosion properties of the joints are discussed. The weld samples were subjected to ageing process at the temperature range of 195°C for a period of 5 h to improve the properties. AA2219 aluminium plates of thickness of 25 mm were welded using gas tungsten arc welding (GTAW) process in double V butt joint configuration. The input parameters considered in this work are welding current, voltage and welding speed. Tensile strength and hardness were measured as performance characteristics. The variation in the properties were justified with the help of microstructures. The same procedures were repeated for post weld heat treated samples and a comparison was made between as weld condition and age treated conditions. The post weld heat samples had better tensile strength and hardness values on comparing with the as weld samples. Fracture surface obtained from the tensile tested specimen revealed ductile mode of failure. 相似文献
8.
对Q235A碳钢A—TIG点焊进行了工艺性的研究,讨论了活性剂对焊点成形。结果表明,使用活性剂后能显著增加焊点熔深。焊点表面成形良好,提高了焊接接头力学性能。焊接电流、点焊时间和弧长均对焊接熔深的增加产生影响。 相似文献
9.
针对穿孔深熔氩弧焊(K-TIG)工艺焊接8 mm厚Q235低碳钢板时焊接过程不稳定、焊接工艺窗口小等突出问题,首次提出在焊接工件背部铺加保护焊剂的方法改善焊接过程。采用对接焊的方式,在不开坡口、焊接过程不添加焊丝的情况下,达到单面焊双面成形的效果。最终成功的采用430~480 A范围内的直流电流对8 mm厚的Q235低碳钢进行了焊接,将焊接电流窗口扩大到50 A同时也显著的提高了焊接过程的稳定性。同时,在扩大焊接电流窗口之后,系统研究了不同焊接电流下焊接接头的组织性能。研究结果表明:在不同焊接电流下得到的焊接接头中,组织分布以及力学性能分布呈现出相同的状态。焊缝区的组织均由铁素体+珠光体+魏氏组织组成;熔合区由魏氏组织组成;热影响区由铁素体+少量的珠光体组成;此外随着焊接电流的增加,焊接接头背部的熔宽有略微增加;在焊接接头中,熔合区处硬度值最高,其次是焊缝区,之后是热影响区,母材的硬度值最低;焊接接头最终的拉伸断裂位置是在热影响区处。 相似文献
10.
This research article examines the metallurgical and mechanical behavior of twenty-first-century nickel-based superalloy 686. The weld joints were produced with ERNiCrMo-4 and ERNiCrMo-14 filler wires by continuous current gas tungsten arc welding (GTAW) and pulsed current gas tungsten arc welding (PCGTAW) mode. Optical and scanning electron microscope (SEM) analyses were performed to evaluate the microstructure of welded joints. PCGTAW weldments showed refined microstructure, narrower weld bead and minimum heat-affected zone compared to GTAW. SEM analysis revealed the presence of secondary phases in the interdendritic regions of GTA and PCGTA weldments made of ERNiCrMo-4 and GTA ERNiCrMo-14 fillers. Energy-dispersive X-ray spectroscopy examination was also performed to assess the microsegregation of alloying elements in the weldments. The results proved nonexistence of microsegregation in the case of PCGTA weldments made by ERNiCrMo-14 filler. However, segregation of alloying element Mo was noticed in other weldments. Strength and toughness of the weld joints were evaluated by conducting tensile and Charpy impact tests. The refined microstructure with the absence of microsegregation obtained in the PCGTA welding made with ERNiCrMo-14 filler wire resulted in the higher strength and toughness than other weldments. 相似文献
11.
Theoretical calculations of gas tungsten arc transport properties have revealed that small amounts of low ionization potential
elements such as aluminum or calcium do not have as great an effect on the electrical and thermal conductivities as has been
previously reported, if the presence of other metal vapors such as iron or manganese is also considered. It is therefore concluded
that the effects of minor elements on arc properties may be less important than has previously been believed in explaining
the variable penetration often associated with minor element additions to the base metal, and that weld pool convection effects
such as surface tension modifications are probably more important. However, the effects of vapors emitted by the tungsten
electrode may have a great effect on arc properties, as the shielding gas is otherwise free of contaminants in the upper regions
of the arc. 相似文献
12.
P. Bala Srinivasan 《国际钢铁研究》2008,79(10):806-808
Laser welding of AISI 410 martensitic stainless steel was attempted in a diffusion cooled RF excited CO2 slab laser under Gaussian mode with argon and nitrogen as shielding gas. The effect of shielding gas and energy density on the resultant weld bead geometry, microstructure and hardness were assessed and discussed. It has been observed that welds obtained under nitrogen shielding conditions had higher and uniform hardness across the weld metal on account of reduced ferrite content. 相似文献
13.
G. Chandrasekar C. Kailasanathan Dhanesh Kant Verma K. Nandagopal 《Transactions of the Indian Institute of Metals》2017,70(3):671-684
This research investigation articulates the joining of AISI 316 L austenitic stainless steel plates of thickness 5 mm by activated tungsten inert gas (A-TIG) welding. Prior to the welding, the optimization of process parameters and the selection of suitable flux have been carried out to join the plates in a single pass welding. The experimental results show that the complete weld penetration can be achieved by using activating flux. The microscopic study divulges the presence of delta ferrite, sigma phase and various forms of austenite in the weld zone. Fischer Feritscope result indicates that the delta ferrite content in the weld is higher (7.8 FN) than the base metal (1.3 FN) which results in superior mechanical properties of the weld. Field Emission-Scanning Electron Microscope (FE-SEM) fractography reveals that the failure of weldments occurs in ductile mode. 180° bend test study reveals the good ductility of the joint. 相似文献
14.
As a new type of high manganese steel, the twinning induced plasticity (TWIP) steels have attracted a growing interest in the automotive industry due to their good performance. Thin plates of TWIP steel were welded by laser beam welding (LBW) and gas tungsten arc welding (GTAW). The microstructure result shows that GTAW joint has obvious heat-affected zone (HAZ), while the HAZ of LBW joint is almost invisible. The X-ray diffraction result shows that the phase compositions of both joints are austenitic and no phase transition occurs. Energy disper- sive spectrometry result shows that there is violent evaporation of Mn element in LBW joint, while the proportion of Mn element in GTAW joint is almost unchanged. Tensile tests and micro-hardness measurements were performed to take into account the mechanical properties of joints manufactured by the two different processes. The micro-hard- ness profiles of both joints present a typical saddle distribution, and the hardness of GTAW seam is lower than that of LBW seam. The failure positions of LBW joints are all located in base metal while the GTAW joints are all at the weld toe due to the softening of HAZ. By means of scanning electron microscopy, a typical ductile fracture is observed in LBW joint, while a brittle fracture with quasi-cleavage fracture characteristic is observed in GTAW joint. 相似文献
15.
Shanping Lu Hidetoshi Fujii Kiyoshi Nogi 《Metallurgical and Materials Transactions A》2004,35(9):2861-2867
Small CO2 additions of 0.092 to 10 vol pct to the Ar shielding gas dramatically change the weld shape and penetration from a shallow
flat-bottomed shape, to a deep cylindrical shape, to a shallow concave-bottomed shape, and back to the shallow flat-bottomed
shape again with increasing CO2 additions in gas thermal arc (GTA) welding of a SUS304 plate. Oxygen from the decomposition of CO2 transfers and becomes an active solute element in the weld pool and reverses the Marangoni convection mode. An inward Marangoni
convection in the weld pool occurs when the oxygen content in the weld pool is over 80 ppm. Lower than 80 ppm, flow will change
to the outward direction. An oxide layer forms on the weld pool in the welding process. The heavy oxide layer on the liquid-pool
surface will inhibit the inward fluid flow under it and also affects the oxygen transfer to the liquid pool. A model is proposed
to illustrate the interaction between the CO2 gas and the molten pool in the welding process. 相似文献
16.
O. Grong T. A. Siewert G. P. Martins D. L. Olson 《Metallurgical and Materials Transactions A》1986,17(10):1797-1807
From an analytical and theoretical study of flat and out-of-position gas metal arc (GMA) C-Mn steel welds containing varying
additions of silicon and manganese, we conclude that the buoyancy effect (flotation obeying Stokes’ law) does not play a significant
role in the separation of oxide inclusions during weld metal deoxidation. Consequently, the separation rate of the particles
is controlled solely by the fluid flow pattern in the weld pool. A proposed two-step model for the weld metal deoxidation
reactions suggests that inclusions formed in the hot, turbulent-flow region of the weld pool are rapidly brought to the upper
surface behind the arc because of the high-velocity flow fields set up within the liquid metal. In contrast, those formed
in the cooler, less-turbulent flow regions of the weld pool are to a large extent trapped in the weld metal as finely dispersed
particles as a result of inadequate melt stirring. The boundary between “hot” and “cold” parts for possible inclusion removal
is not well defined, but depends on the applied welding parameters, flux, and shielding gas composition. As a result of the
intricate mechanism of inclusion separation, the final weld metal oxygen content depends on complex interactions among the
following three main factors: (1) the operational conditions applied, (2) the total amount of silicon and manganese present,
and (3) the resulting manganeseto-silicon ratio. The combined effect of the latter two contributions has been included in
a new deoxidation parameter, ([pct Si][pct Mn])−0.25. The small, negative exponent in the deoxidation parameter indicates that control of the weld metal oxygen concentrations
through additions of silicon and manganese is limited and that choice of operational conditions in many instances is the primary
factor in determining the final degree of deoxidation to be achieved. 相似文献
17.
This article describes a theoretical investigation on the arc parameters and metal transfer in gas metal arc welding (GMAW)
of mild steel using argon and helium shielding gases. Major differences in the predicted arc parameters were determined to
be due to large differences in thermophysical properties. Various findings from the study include that an arc cannot be struck
in a pure helium atmosphere without the assistance of metal vapor, that a strong electromagnetic cathode force affects the
fluid flow and heat transfer in the helium arc, providing a possible explanation for the experimentally observed globular
transfer mode and that the tapering of the electrode in an argon arc is caused by electron condensation on the side of the
electrode.
Formerly Graduate Student, Massachusetts Institute of Technology 相似文献
18.
V. Maduraimuthu M. Vasudevan V. Muthupandi A. K. Bhaduri T. Jayakumar 《Metallurgical and Materials Transactions B》2012,43(1):123-132
A novel variant of tungsten inert gas (TIG) welding called activated-TIG (A-TIG) welding, which uses a thin layer of activated
flux coating applied on the joint area prior to welding, is known to enhance the depth of penetration during autogenous TIG
welding and overcomes the limitation associated with TIG welding of modified 9Cr-1Mo steels. Therefore, it is necessary to
develop a specific activated flux for enhancing the depth of penetration during autogeneous TIG welding of modified 9Cr-1Mo
steel. In the current work, activated flux composition is optimized to achieve 6 mm depth of penetration in single-pass TIG
welding at minimum heat input possible. Then square butt weld joints are made for 6-mm-thick and 10-mm-thick plates using
the optimized flux. The effect of flux on the microstructure, mechanical properties, and residual stresses of the A-TIG weld
joint is studied by comparing it with that of the weld joints made by conventional multipass TIG welding process using matching
filler wire. Welded microstructure in the A-TIG weld joint is coarser because of the higher peak temperature in A-TIG welding
process compared with that of multipass TIG weld joint made by a conventional TIG welding process. Transverse strength properties
of the modified 9Cr-1Mo steel weld produced by A-TIG welding exceeded the minimum specified strength values of the base materials.
The average toughness values of A-TIG weld joints are lower compared with that of the base metal and multipass weld joints
due to the presence of δ-ferrite and inclusions in the weld metal caused by the flux. Compressive residual stresses are observed in the fusion zone
of A-TIG weld joint, whereas tensile residual stresses are observed in the multipass TIG weld joint. 相似文献
19.
Jalal Kangazian Morteza Shamanian 《Transactions of the Indian Institute of Metals》2018,71(7):1747-1757
This study was carried out to investigate the evaluation of dissimilar welding between Incoloy 825 Ni-based alloy and SAF 2507 super duplex stainless steel. Welding was conducted by pulsed current (PC) and continuous current (CC) gas tungsten arc welding (GTAW) methods using ERNiCrMo-3 filler wire. The microstructure of weld zones and base metal/weld interfaces as well as mechanical properties of weldments were characterized. The results detailed the formation of Nb, and Mo-rich phases in the inter-dendritic regions of weld metals leading to a decrease in impact resistance of weld zones in comparison to parent metals. Presence of more secondary phases at the CCGTA weld metal resulted in higher hardness and lower toughness than that of the PCGTAW sample. During tensile tests, fracture occurred at the Incoloy 825 base metal, and both weldments also underwent ductile mode of fracture. The research addressed the microstructure–property relationship for dissimilar weld joints. 相似文献
20.
Manabu Tanaka Hidenori Terasaki Ph.D. Masao Ushio John J. Lowke 《Metallurgical and Materials Transactions A》2002,33(7):2043-2052
In order to clarify the formative mechanism of weld penetration in an arc welding process, the development of a numerical
model of the process is quite useful for understanding quantitative values of the balances of mass, energy, and force in the
welding phenomena because there is still lack of experimentally understanding of the quantitative values of them because of
the existence of complicated interactive phenomena between the arc plasma and the weld pool. The present article is focused
on a stationary tungsten-inert-gas (TIG) welding process for simplification, but the whole region of TIG arc welding, namely,
tungsten cathode, arc plasma, workpiece, and weld pool is treated in a unified numerical model, taking into account the close
interaction between the arc plasma and the weld pool. Calculations in a steady state are made for stationary TIG welding in
an argon atmosphere at a current of 150 A. The anode is assumed to be a stainless steel, SUS304, with its negative temperature
coefficient of surface tension. The two-dimensional distributions of temperature and velocity in the whole region of TIG welding
process are predicted. The weld-penetration geometry is also predicted. Furthermore, quantitative values of the energy balance
for the various plasma and electrode regions are given. The predicted temperatures of the arc plasma and the tungsten-cathode
surface are in good agreement with the experiments. There is also approximate agreement of the weld shape with experiment,
although there is a difference between the calculated and experimental volumes of the weld. The calculated convective flow
in the weld pool is mainly dominated by the drag force of the cathode jet and the Marangoni force as compared with the other
two driving forces, namely, the buoyancy force and the electromagnetic force. 相似文献