shielding-gas-mison-25.html
AGA CW Handbook A4_32130-UK
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shielding
gas
es for unalloyed ans low-alloy steels contents 6.1 general selection table 6.1 general unalloyed and low-alloy steels can be divided into types based on their properties, purpose of use and heat treatment according to the following table. with regard to the selection of the shielding gas, they all belong to the same group. when a shielding gas is selected for unalloyed and low-alloy steels, the following factors are more important than the type of the base material: → welding
process: tig or mig/mag welding → manual or mechanical welding → type of filler material: solid wire, flux-cored wire or metal-cored wire → short arc, spray arc, pulse or high-productivity welding (rapid processing ® ) mison ® ar shielding gas is recommended for the tig welding of unallo- yed and low-alloy steels. if the goal is higher productivity, the mison ® h2 shielding gas can be used in the tig welding of unalloyed steels, when welding thin materi- als with low internal stresses. steels discription regular steels hot rolled or normalised/normalisation rolled for example carbon and carbon-manganese steels. yield en 10025-2: s235 jr strength up to around 300 mpa. din 17100: rst 37-2 raex laser 250 c high-strength steels thermomechanically rolled or normalised/ for example normalisation rolled. yield strength around en 10025-2: s 355 jo 300–400 mpa. can be welded as regular steels. din 17100: st 52-3 u preheating may be required with thicker sheets. raex multisteel more information is available from the steel manufacturer. ultra-high-strength steels thermomechanically rolled or normalised/ for example normalisation rolled yield strength around en 10149-2: s 500 mc 400 mpa and above. can be welded as regular din sew 092: qste 500 tm steels. preheating may be required with thicker raex optim 500 mc sheets. more information is available from the steel manufacturer. high quality and economical benefits can be achieved through the utilisa- tion of the different properties. solid wire or cored wire can be used in the mag welding of unalloyed and low-alloy steels. the cored wire can be either metal-cored or powder-cored. most filler materials are designed and approved for welding with specific shielding gases, or more commonly, specific type of shielding gas. the selection of possible shielding gases is usually large, allowing the utilisation of the differences in the properties of the different shielding gases on a case-by-case basis. for example, solid wires for unalloyed and low-alloy steels allow a greater freedom with regard to the carbon dioxide content of the shielding gas compared to, let’s say, flux-cored wires designed for high-alloy steels. flux-cored wires are returned to later in this handbook. mison ® 8 shielding gas is especially recommended for robot welding and mechanised welding, and high-productivity welding (rapid processing ® ). with it, a high welding speed and low-spatter welding can be achieved. the weld bead is low and there is very little surface slag. the shielding gas is suited to short arc, spray arc and pulse welding. it is also suited to manual welding where a spatter-free and low-slag weld is desirable. mison ® 18 shielding gas can be considered as a general gas which is suited to both mechanised and manual welding. the shielding gas has good short and spray arc properties, and it can also be used as the shielding gas for pulse welding. the shielding gas provides low-spatter welding producing a low weld bead. mison ® 25 provides a fluid and highly manageable molten pool when short arc is used. the shielding gas has an excellent tolerance to impurities in spray arc welding, and it produces a tight weld even in unfavourable conditions. compared to carbon dioxide, spatter formation is reduced and the weld fusion with the base material and welding speed are significantly better. it is the most oxidising of the gas mixtures, due to which slag formation is also highest. mison ® 25 is the most used shielding gas, which is especially recom- mended for short arc welding (small machines) and spray arc welding when the weld has tightness requirements or the welding conditions are unfavourable. shielding gases for unalloyed and low-alloy steels. the mison ® 8, mison ® 18 and mison ® 25 shielding gases have significant welding- technical differences.
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