Welding processing escort, inert gas is introduced.
Release time:
2022-08-29
【Summary Description】 Inert gas is introduced. Although inert gas can provide protection to the weld pool, it is not suitable for flux-cored welding of iron-based metals (such as low carbon steel, low alloy steel, stainless steel, etc.). For example, if stainless steel is welded using only Ar as a shielding gas, the weldability becomes poor. This is because inert gas protection will lead to longer arc length and premature melting of the outer steel skin of the electrode. The arc range is large and difficult to control, resulting in weld accumulation. Therefore, in the case of welding an iron-based metal using a flux-cored wire GMAW, a mixed gas of an inert gas and an active gas is generally used. Introduction of CO2/Ar gas mixtures. In North America, the welding of stainless steel flux-cored wire gas shielded arc welding often uses Ar/CO2 mixed gas as the shielding gas, of which Ar accounts for 75% and CO2 accounts for 25%. Sometimes 80% Ar and 20% CO2 are mixed, but this mixing ratio is not commonly used. Some gas-shielded flux-cored wires require the use of a mixture of 90% Ar and 10% CO2 for shielding. However, if the Ar content in the mixed protective gas is less than 75%, the arc performance will be affected, so the proportion of Ar in the mixed protective gas must be ensured. In addition, tanks containing non-standard percentage Ar/CO2 mixtures tend to be more difficult to obtain than tanks containing standard percentage mixtures (e. g., 75% Ar and 25% CO2 or 80%). Ars and 20% CO2). Alloy retention and mechanical properties. Due to the active nature of CO2, when using Ar/CO2 mixed gas shielding for flux-cored wire welding, the degree of electrode alloy deposition in the weld metal is higher than when using pure CO2 gas shielding. This is because CO2 reacts with the alloy to form oxides, which together with the oxides in the flux form slag. The flux core of the electrode must contain some active elements, such as manganese (Mn) and silicon (Si), and can be used as a deoxidizer, among other uses. Some of these alloys react with free oxygen obtained by CO2 ionization to form oxides, which remain in the slag rather than in the weld metal. Therefore, the content of Mn and Si in the deposited metal using Ar/CO2 mixed gas is higher than that using CO2 gas. The higher the content of Mn and Si in the weld deposited metal, the greater the weld strength, the lower the weld elongation, and the impact toughness of the sharp V-shaped notch will also change. Simply changing the shielding gas from CO2 to Ar/CO2 mixture will increase the tensile strength and yield strength by 7 to 10 ksi, and reduce the elongation by 2%, as shown in Figure 2. It is important to understand that as the Ar content in the shielding gas increases, the weld strength increases and the toughness decreases. Since the shielding gas will affect the final performance of the weld, AWS D1.1/D1.1 M:2008 "Steel Structure Welding Specification" stipulates a series of specific requirements to ensure the performance of the weld. For all welds, the selection of shielding gas must be consistent with the AWS A5.32/A5.32M Standard AWS FCAW-G Welding Consumables Classification (A5.20/A 5.2 M and A5.29M) which specifies the maximum strength of the weld deposit. The welding shielding gas selected must ensure that the welding result does not exceed these specified strength limits, which also depends on the electrode design and welding process. For unmodified welding procedures, D1.1:2008 requires specific filling and shielding gas compositions to support the test data. D1.1:2008 Item 3.7.3 specifies two forms of support: one is the use of shielding gas for electrode classification. One is that the data of the filler metal manufacturer meets the requirements of AWS A5 and meets the shielding gas specified by WPS. If neither of these conditions is met, D1.1:2008 requires an evaluation of the protective gas mixture.
Inert gas is introduced.
Although inert gas can provide protection to the weld pool, it is not suitable for flux-cored welding of iron-based metals (such as low carbon steel, low alloy steel, stainless steel, etc.). For example, if stainless steel is welded using only Ar as a shielding gas, the weldability becomes poor. This is because inert gas protection will lead to longer arc length and premature melting of the outer steel skin of the electrode. The arc range is large and difficult to control, resulting in weld accumulation. Therefore, in the case of welding an iron-based metal using a flux-cored wire GMAW, a mixed gas of an inert gas and an active gas is generally used.
Introduction of CO2/Ar gas mixtures.
In North America, the welding of stainless steel flux-cored wire gas shielded arc welding often uses Ar/CO2 mixed gas as the shielding gas, of which Ar accounts for 75% and CO2 accounts for 25%. Sometimes 80% Ar and 20% CO2 are mixed, but this mixing ratio is not commonly used. Some gas-shielded flux-cored wires require the use of a mixture of 90% Ar and 10% CO2 for shielding. However, if the Ar content in the mixed protective gas is less than 75%, the arc performance will be affected, so the proportion of Ar in the mixed protective gas must be ensured. In addition, tanks containing non-standard percentage Ar/CO2 mixtures tend to be more difficult to obtain than tanks containing standard percentage mixtures (e. g., 75% Ar and 25% CO2 or 80%). Ars and 20% CO2). Alloy retention and mechanical properties.
Due to the active nature of CO2, when using Ar/CO2 mixed gas shielding for flux-cored wire welding, the degree of electrode alloy deposition in the weld metal is higher than when using pure CO2 gas shielding. This is because CO2 reacts with the alloy to form oxides, which together with the oxides in the flux form slag. The flux core of the electrode must contain some active elements, such as manganese (Mn) and silicon (Si), and can be used as a deoxidizer, among other uses. Some of these alloys react with free oxygen obtained by CO2 ionization to form oxides, which remain in the slag rather than in the weld metal. Therefore, the content of Mn and Si in the deposited metal using Ar/CO2 mixed gas is higher than that using CO2 gas.
The higher the content of Mn and Si in the weld deposited metal, the greater the weld strength, the lower the weld elongation, and the impact toughness of the sharp V-shaped notch will also change. Simply changing the shielding gas from CO2 to Ar/CO2 mixture will increase the tensile strength and yield strength by 7 to 10 ksi, and reduce the elongation by 2%, as shown in Figure 2. It is important to understand that as the Ar content in the shielding gas increases, the weld strength increases and the toughness decreases.
Since the shielding gas will affect the final performance of the weld, AWS D1.1/D1.1 M:2008 "Steel Structure Welding Specification" stipulates a series of specific requirements to ensure the performance of the weld. For all welds, the selection of shielding gas must be consistent with the AWS A5.32/A5.32M Standard AWS FCAW-G Welding Consumables Classification (A5.20/A 5.2 M and A5.29M) which specifies the maximum strength of the weld deposit. The welding shielding gas selected must ensure that the welding result does not exceed these specified strength limits, which also depends on the electrode design and welding process. For unmodified welding procedures, D1.1:2008 requires specific filling and shielding gas compositions to support the test data.
D1.1:2008 Item 3.7.3 specifies two forms of support: one is the use of shielding gas for electrode classification. One is that the data of the filler metal manufacturer meets the requirements of AWS A5 and meets the shielding gas specified by WPS. If neither of these conditions is met, D1.1:2008 requires an evaluation of the protective gas mixture.
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