Title of Invention

AN APPARATUS AND A PROCESS FOR ALTERNATING SUPPLY OF TWO SHIELDING GASES TO A GAS METAL ARC WELDING (GMAW) TORCH AT A PRE-SET ALTERNATING/ PULSING FREQUENCY

Abstract

Accordingly, there is provided an apparatus and process for alternate supply of shielding gas to the GMAW torch. The proposed method delivers two different shielding gases alternatively to the GMAW torch directly without any pre-mixing. The pulsing frequency is adjustable from 20 to 120 cycles/min. The welding parameters and the alternate shielding gas supply frequency for improved weld quality is also established.

Full Text

-2- FIELD OF INVENTION The invention relates to an apparatus and process for alternating the shielding gas supply to the arc in GMAW process to achieve improved weld quality including reduction in shielding gas consumption. More particularly, the invention relates to an apparatus to alternate the shielding gas supply to the GMAW torch and optimization of gas pulsing frequency for improved weld quality. BACKGROUND OF THE INVENTION: GMAW is one of the important arc welding processes widely used in the fabrication industries all over the world. This is an electric arc welding process, which produces coalescence of metals by heating them with an arc established between a continuous filler metal (consumable) electrode and the work. Shielding of the arc and molten weld pool is obtained by an externally supplied gas, which may be inert, reactive or a mixture of inert and reactive gases. The GMAW process is known as Metal Inert Gas (MIG) welding, when the shielding gas used is inert, and also known as Metal Active Gas -3- (MAG) welding when the shielding gas contains reactive gases, such as 02 or CO. sub.2 or mixtures of inert and reactive gases. Each shielding gas has its own properties, including ionization potential, and produces unique arc characteristics. For instance, 100%CO2 shielding in mild steel application produces somewhat harsh arc with associated spatter but gives better weld penetration. On the other hand, 100% argon shielding for mild steel application produces very stable arc but results in very poor bead wetting. In order to achieve stable arc and also good bead wetting characteristics in ferrous applications, a shielding gas mixture containing argon+CO2 or argon+02 of different proportions is used in the industries for over two decades. Though GMAW with argon+CO2 and argon+02 mixed gas is successful in welding of ferrous metals, there are some limitations. The mixed gases used in industries are generally rich in argon (argon > 80%) resulting higher shielding gas cost. Variation in the mixing ratio particularly with gas mixing units Leads to poor weld quality due to changes in arcing characteristics. -4- In conventional GMAW for welding of ferrous metals, it is standard practice to use 100%CO2 or argon+CO2 gas mixture depending on the quality requirement and application. The use of 100%CO2 or argon+CO2 gas mixture produces a constant arc dynamics. The arc pressure and weld pool fluidity remain constant. OBJECTS OF THE INVENTION It is therefore an object of the invention to propose an apparatus and process for alternate supply of shielding gas to the GMAW torch. Another object of the invention is to propose an apparatus and process for alternate supply of shielding gas to the GMAW torch in which the shielding gas can be directly supplied to the GMAW torch to avoid mixing of the gas before entering the torch. A further object of the invention is to propose an apparatus and process for alternate supply of shielding gas to the GMAW torch in which due to optimization of pulsing frequency of the gas supply achieves improved weld quality. -5- A still further object of the invention is to propose an apparatus and process for alternate supply of shielding gas to the GMAW torch in which shielding gas can be alternatingly supplied at different frequencies. These and other objects and advantages of the invention will be apparent from the ensuing description. At the outset of the description, which follows, it is to be understood that the ensuing description only illustrates a particular form of this invention. However, such a particular form is only an exemplary embodiment and the teachings of the invention are not intended to be taken restrictively. SUMMARY OF THE INVENTION Accordingly, there is provided an apparatus and process for alternate supply of shielding gas to the GMAW torch. The proposed method delivers two different shielding gases alternatively to the GMAW torch directly without any pre-mixing. The pulsing frequency is adjustable from 20 to 120 cycles/min. The welding parameters and the alternate shielding gas supply frequency for improved weld quality is also established. -6- BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Figure 1 (Schematic)- Shows an embodiment of the apparatus according to the invention. Figure 2- shows the diagram of the shielding gas alternator. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION Referring now to the drawings. Wherein like reference numerals designate identical or corresponding parts throughout the several views. Figl shows the schematic of the alternate gas supply system. At least two hoses (3,4) carrying argon and CO2 gases from two individual gas cylinders (1,2) are connected to the respective input terminals (5,6) provided in a gas supply alternator (9). The duration of flow for each individual gas is controlled through two timer knobs (7,8) provided in the front panel of the shielding gas alternator (9). Two gas outlets (10,11) provided on the front panel of the shielding gas alternator (9) is connected to a plurality of nipples (14,15) -7- provided in a GMAW torch nozzle directly through two individual hoses (12,13) for each gas. The hose (12,13) length from the shielding gas alternator (9) to the torch is kept to a minimum to make it dynamically more responsive. Adjusting the timer control (7,8) varies the shielding gas alternating/pulsing frequency. As shown in Fig. 2 SI and S2 are the two solenoid valves and Tl and T2 are the timers used for controlling the flow duration. The alternate shielding gas supply process overcomes the limitations of mixed gas method. The technology of alternate supply of shielding gas has influence on every aspect of the arc welding. The alternate supply of shielding gas causes a dynamic action on the molten weld pool, which results in improved weld quality both in terms of fusion characteristics and bead appearance. The alternate shielding gas supply technology causes multiple impacts to weld pool resulting in much improved weld quality. -8- WE CLAIM: 1. An apparatus for alternatingly supply two different shielding gases to a GMAW torch at a preset alternating / pulsing frequency, comprising: -two different gas hoses (3,4) for carrying two different gases from two individual gas cylinders (1,2), the hoses (3,4) being connected to the respective input terminals (5,6) provided in a shielding gas alternator (9); and - the shielding gas alternator (9) having at least two timer knobs (7,8), and two gas outlets (10,11), the gas outlets (10,11) connected to a GMAW torch via two individual hoses (12,13), characterized in that the length of the hoses (12,13), is selected such that the alternating and/or pulsing frequency of the supplied shielding gas is optimized to improve the weld quality. 2. The apparatus as claimed in claim 1, wherein two different shielding gases is selected from a combination of argon and carbon dioxide; argon and helium; and argon and oxygen. -9- 3. The apparatus as claimed in claim 1, wherein the shielding gas supply is alternated at a frequency range of 20 to 120 cycles/minute through a solenoid valve control (S1,S2); 4. The apparatus as claimed in claim 1, wherein the gas pulsing frequency is controlled through timer circuit (7,8) for controlling the duration of flow of individual gases. 5. An apparatus for alternatingly supply two different shielding gases to a GMAW torch at a present alternating / pulsing frequency as substantially described and illustrated herein with reference to the accompanying drawings. 6. A new version of GMAW process wherein the welding is carried out with alternating supply of shielding gases for carbon steel, stainless steel and aluminum. Dated this 5th day of FEBRUARY 2007 Accordingly, there is provided an apparatus and process for alternate supply of shielding gas to the GMAW torch. The proposed method delivers two different shielding gases alternatively to the GMAW torch directly without any pre-mixing. The pulsing frequency is adjustable from 20 to 120 cycles/min. The welding parameters and the alternate shielding gas supply frequency for improved weld quality is also established.

Documents:

00172-kol-2007-correspondence.pdf

00172-kol-2007-form-18.pdf

0172-kol-2007 abstract.pdf

0172-kol-2007 assignment.pdf

0172-kol-2007 claims.pdf

0172-kol-2007 correspondence others.pdf

0172-kol-2007 description(complete).pdf

0172-kol-2007 drawings.pdf

0172-kol-2007 form-1.pdf

0172-kol-2007 form-2.pdf

0172-kol-2007 form-3.pdf

172-KOL-2007-(23-01-2012)-ABSTRACT.pdf

172-KOL-2007-(23-01-2012)-AMANDED CLAIMS.pdf

172-KOL-2007-(23-01-2012)-DESCRIPTION (COMPLETE).pdf

172-KOL-2007-(23-01-2012)-DRAWINGS.pdf

172-KOL-2007-(23-01-2012)-EXAMINATION REPORT REPLY RECIEVED.PDF

172-KOL-2007-(23-01-2012)-FORM 1.pdf

172-KOL-2007-(23-01-2012)-FORM 2.pdf

172-KOL-2007-(23-01-2012)-FORM 3.pdf

172-KOL-2007-(23-01-2012)-OTHERS.pdf

172-KOL-2007-(24-07-2012)-CORRESPONDENCE.pdf

172-KOL-2007-CORRESPONDENCE.pdf

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