Selection of shielding gas for co2 flux core gas shielded welding, introduction of inert gas

【Summary Description】 When selecting GMAW shielding gas, factors such as welding cost, welder preference and welding quality should be considered. Flux-cored wire gas shielded welding is a widely used welding technology. It is widely used in the welding of low carbon steel, low alloy steel and other alloy materials in heavy manufacturing, construction, shipbuilding, marine facilities and other industries. The FCAW-G welding process often uses 100% pure CO2 or 75% ~ 80% Ar and 20% ~ 25% CO2 mixed gas as the protective gas. So in the implementation of flux-cored wire gas welding, which shielding gas should be selected, CO2 or Ar/CO2 mixed gas? Each shielding gas has its own advantages and disadvantages. When selecting a welding shielding gas, it is important to consider factors such as cost, quality, and productivity. Sometimes the choice of protective gas and these factors are contradictory. The advantages and disadvantages of FCAW-G in the selection of two basic shielding gases for welding steel are introduced. Before discussing the advantages and disadvantages of protective gas in detail, it is best to review some basic knowledge. It should be noted that only a few shielding gases are discussed in this article. For a more comprehensive introduction, please refer to ANSI/AWSA5.32/A5.32M. The welding shielding gas specification specifies the technical requirements for shielding gas, including testing, packaging, marking, acceptance, etc. In addition, it also includes some useful information, such as ventilation during welding, and full consideration of safety requirements. Working principle of protective gas. One of the main functions of all shielding gases is to isolate oxygen, nitrogen and water vapor from the air, and to protect the weld pool and electrodes. The shielding gas enters through the welding torch, is sprayed from the nozzle and surrounds the electrode, displaces the air around the electrode, and forms a temporary shielding gas around the molten pool and the arc. Both CO2 gas and Ar/CO2 mixed gas can achieve this goal. These shielding gases promote the formation of the arc plasma region, which is the current path for the welding arc. The type of shielding gas also affects the heat transfer of the arc and the arc force exerted on the molten bath. CO2 and Ar/CO2 mixtures exhibit different behavior on these issues. Characteristics of the shielding gas. The reaction of CO2 and Ar in arc heat is different. Analyzing these differences can help understand how the properties of each gas affect the welding process and weld deposit. ionization potential. The ionization potential is the energy required to ionize a gas (e. g., convert the gas to a charged ionic state), making the gas conductive. The lower the ionization potential, the easier it is for the arc to ignite and remain stable. The ionization potential of CO2 is 14.4 eV The electron volt of argon is 15.7 eV. Therefore, CO2 shielding gas is easier to arc than Ar shielding gas. Heat conduction. The heat transfer of gas refers to the ability of gas to conduct heat energy, which will affect the transfer mode of molten droplets (such as jet transfer and large droplet transfer), arc shape, weld penetration and arc temperature distribution. The CO2 gas has a higher thermal conductivity than the Ar gas and the Ar/CO2 mixed gas. Reactive. The reactivity of the gas refers to whether the gas reacts with the molten bath. Gases can be broadly divided into two categories: inert gases and reactive gases. An inert gas that does not react with other elements in the bath. Ar is an inert gas. The reactive gas combines or reacts with other elements in the bath to form new compounds. At room temperature, CO2 is an inert gas, but in the arc plasma region CO2 is decomposed into carbon monoxide (CO), oxygen (O2) and some independent oxygen atoms (O). Therefore, CO2 becomes an active gas under the arc and can be oxidized with other metals. The Ar/CO2 mixture is also a reactive gas, but is less reactive than CO2. When the parameters of other welding specifications are consistent, the welding smoke produced by different shielding gases is also different. In particular, Ar/CO2 shielding gas produces less welding dust than CO2 shielding gas because CO2 is oxidizing. In addition, due to the different welding occasions and welding sequence, the amount of welding fume is also different.

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Welding processing escort, inert gas is introduced.

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CO2 gas shielded welding, flat butt welding, single-sided welding, double-sided forming operation process