shielding-weld-gas-21.html
AGA CW Handbook A4_32130-UK
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shielding
gas
and quality by reducing the co 2 or o 2 content of the shielding gas, the burning loss of alloy materials in the filler material is reduced, increasing the yield strength and tensile strength. the differences between mechanical cha- racteristics in argon-carbon dioxide mixtures in the range of 8–25% are so small that they usually do not have a practical significance. however, when pure carbon dioxide is used, the difference may be significant compared to the above. extensive research has shown that the small no addition in the mison ® shielding gases does not affect the mechanical characteristics of the weld
. the fatigue resistance of the welded joint strongly depends on the geometry of the welded joint. in mig/mag welding, the weld shape ´can be affected by the selection of a shielding gas. with gas mixtures, a smoother fusion between the weld and the base material is achieved than with carbon dioxide. the peak stresses in the structure (notch effect) are smaller and the fatigue resistance of the welded structure is better. in structures with fatigue-inducing loads, certain requirements are set for the fatigue resistance and the weld fusion with the base material. if the fusion is poor, grinding or tig treatment is required on the welded joint, increasing costs. oxide inclusions in the weld affect the fatigue resistance even if the weld is grinded or polished. oxide inclusions can act as the nucleation of the crack. the higher the carbon dioxide or oxygen content of the shielding gas, the larger the number of oxide inclusions in the weld deposit. the large amount of hydrogen dissolved into the weld can cause brittleness and porosity, in particular with unalloyed, low-alloy and non-austenitic high-alloy steels. in certain conditions, adding hydrogen to the shielding gas is beneficial. in the tig welding of unalloyed and low-alloy steels, productivity can be improved and surface oxidation reduced by using the mison ® h2 shielding gas, which contains 2% hydrogen. this requires that the base material is not very thick and the internal stresses do not rise very high. better fatigue resistance with argon mixtures by using argon mixtures, a better fusion between the weld and the base material can be achieved, while also improving the fatigue resi- stance of the weld. weld toughness with different shielding gases and filler materials pz 6103 metal-cored wire (aws a5.20: e71t-g) pz 6104 nickel-alloy metal-cored wire (aws a5.29 : e71tg-ni1) pz 6111 rutile cored wire (aws a5.20: e71t-1) ar + 20% co 2 welding speed 47 cm/min co 2 welding speed 40 cm/min when unalloyed and low-alloy steels are tig welded with mison ® h2 used as the shielding gas, the hydrogen content of the weld is comparable with rutile cored wire welding. 1 2 ml h 2 /100 g weld deposit hydrogen content of weld very low low average high rutile electrodes cored wires submerged arc alkaline electrodes solid wires tig welding with mison ® h2 as shielding gas 1 3 5 2 4 6 3 4 5 6 0 5 10 15 20 25 30 35 2 1 3 4 5 6
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