Performance of activated TIG process in austenitic stainless steel welds

Wire and arc additive manufacturing : Opportunities and challenges to control the quality and accuracy of manufactured parts

Study of the characteristics of duplex stainless steel activated tungsten inert gas welds

At present aluminium-magnesium alloys are widely used in various engineering applications due to its light weight and superior properties. Joining is considered as one of the most complex phenomenon in various precision industries like aerospace, railway, automotive and marine structures because inflexible tolerances are required during different product assembly. The friction stir welding (FSW) of aluminium-magnesium of various grade has incited substantial scientific and industrial importance since it has a potency to transform the product with a good quality joint. The fabrication of such alloys is a challenging task through conventional fusion welding due to its various metallurgical concerns. Therefore, the present work is intended to summarize the recent progress in FSW of aluminium-magnesium alloys. Particular attention has been paid to microstructural evolution, phase transformation, recrystallization mechanism, material flow behaviour and how the process parameters influence the various mechanical properties and associated defects during FSW. Various experimental and numerical simulation results have been mentioned for weld property comparison. Finally, this work not only points out the prominent conclusions of the preceding research but also recommends the upcoming guidance concerning to fabrication of aluminium-magnesium alloys through FSW.

Recent research progress in solid state friction-stir welding of aluminium–magnesium alloys: a critical review

The paper critically assesses the research progress towards aluminium–magnesium dissimilar friction stir welding (FSW). First, the theoretical requirements are explored through the understanding of joining mechanism and heat generation in aluminium–magnesium FSW. Next, the observed trends in microstructural characterisation and mechanical properties are analysed. Finally, the effects of welding parameters and how it influences process variables and materials responses are discussed in detail, and several suggestions are made based on these discussions.

Review of research progress on aluminium–magnesium dissimilar friction stir welding

A new type of tungsten inert gas (TIG) welding has been developed, in which an ultra-deep penetration is obtained. In order to control the Marangoni convection induced by the surface tension gradient on the molten pool, He gas containing a small amount of oxidizing gas was used. The effect of the concentration Of O-2 and CO2 in the shielding gas on the weld shape was studied for the bead-on-plate TIG welding of SUS304 stainless under He-O-2 and He-CO2 mixed shielding gases. Because oxygen is a surface active element for stainless steel, the addition of oxygen to the molten pool can control the Marangoni convection from the outward to inward direction on the liquid pool surface. When the oxygen content in the liquid pool is over a critical value, around 70ppm, the weld shape suddenly changes from a wide shallow shape to a deep narrow shape due to the change in the direction of the Marangoni convection. Also, for He-based shielding gas, a high welding current will strengthen both the inward Marangoni convection on the pool surface and the inward electromagnetic convection in the liquid pool. Accordingly, at a welding speed of 0.75 mm/s, the welding current of 160 A and the electrode gap of I mm under the He-0.4%O-2 shielding, the depth/width ratio reaches 1.8, which is much larger for Ar-O-2 shielding gas (0.7). The effects of the welding parameters, such as welding speed and welding current were also systematically investigated. In addition. a double shielding gas method has been developed to prevent any consumption of the tungsten electrode. (c) 2008 Elsevier B.V. All rights reserved.

http://www.jwri.osaka-u.ac.jp/~dpt9/MSE(2008)HeAA-TIG.pdf

Development of an advanced A-TIG (AA-TIG) welding method by control of Marangoni convection

Tungsten inert gas (TIG) and metal inert gas (MIG) welding are the most popular gas-shielded arc-welding processes used in many industrial fields. MIG welding is a high-efficiency process compared to TIG welding. However, improvements are needed to reduce spatter and improve weld metal toughness. Although pure argon shielding gas is desirable for weld metal toughness, MIG arcs are unstable in pure Ar to the extent that executing welding is difficult. We have found that MIG arcs become stable even using pure argon by simply using a hybrid TIG and MIG system. This process has the possibility of becoming a new welding process giving high quality and efficiency. In this study, we investigate the influence of the balance of current between the TIG and MIG arcs, which is most important in determining arc stability and arc penetration. We have confirmed the suitable range of conditions both experimentally and through numerical simulation and have applied this process for butt and fillet joints. We show that the welding time can be reduced to 17 ~ 44 % of the time required using a conventional TIG process.

Study for TIG–MIG hybrid welding process

On TIG-MIG hybrid welding process (TIG: DCEN and MIG: DCEP), the stability of MIG arc can be kept even in pure inert shielding gas by the effect of hybridization with TIG arc, and it becomes possible to achieve the new welding method which has both merits of high quality as TIG welding process and high efficiency as MIG welding process. In this report, we performed two experiments mainly as follows to solve two problems: (1) Analysis of output from TIG power source in hybrid welding state to prove experimentally the existence of direct current path which flows between TIG cathode and MIG anode via in hybrid arc plasma. (2) Measurement of actual heat input based on evaporation amount of liquid nitrogen to investigate detailed heat source property of this process. As results, it was shown that output of TIG power source in hybrid welding condition is lower than it in single TIG welding, and the heat efficiency in hybrid welding condition decreases about 10 % rather than it in single heat source of TIG or MIG arc. Moreover, in specific condition that value of TIG current is lower than value of MIG current, output of TIG power source becomes entirely zero even though TIG arc shape is observed clearly, and thus, the stability of MIG arc is lost then. It can be said that these findings reveal the existence of direct current and explain one of mechanisms that TIG arc can control the arc stability and heat input of MIG arc.

Study for the mechanism of TIG-MIG hybrid welding process

PROBLEM TO BE SOLVED: To provide a reactor with a resin mold object excellent in both crack resistance and heat dissipation nature, in which the resin mold object is formed around a reactor core housed in a case, and a manufacturing method thereof. SOLUTION: A reactor 10 comprises a case 3, a heat dissipation board 2 provided on the lower surface of the case 3, and a reactor core 4 equipped with a coil 5 and placed on the heat dissipation board 2 in the case 3. The upper surface of the coil 5 is positioned lower than the upper end of the sidewall of the case 3. In the case 3, a first resin mold object 61 having relatively high hardness and high heat dissipation nature is formed from the heat dissipation board 2 to a portion of the coil 5 at least and a second resin mold object 62 having relatively low hardness is formed from a portion of the coil 5 to the upper end of the sidewall of the case 3 or the vicinity thereof. COPYRIGHT: (C)2009,JPO&INPIT

Toyoyuki Sato

Papers

Development of an advanced A-TIG (AA-TIG) welding method by control of Marangoni convection

Study for TIG–MIG hybrid welding process

Study for the mechanism of TIG-MIG hybrid welding process

Reactor and its manufacturing method

Basic Study on TIG-MIG Hybrid Welding Process