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AGA CW Handbook A4_32130-UK
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14 the effect of
shielding
gas
on productivity contents 4.1 general 4.2 welding
process 4.3 shielding gas 4.3.1 ar/co 2 gas mixtures or co 2 4.3.2 welding speed and deposition rate 4.3.3 spatter, post-weld cleaning 4.3.4 mig soldering 4.3.5 adding helium or hydrogen 4.4 filler material and shielding gas 4.5. high-productivity mig/mag welding 4.5.1 example of a forced short arc application 4.5.2 example of a rotating spray arc application 4.1 general the total costs of welding per produced unit comprise several different factors. the chart beside illustrates the factors of which the costs are formed and how they are divided. shielding gas, filler material, main- tenance and electrical power form a relatively small part of the total costs. the majority of costs in both manual and mechanised welding are formed of work and capital costs. in order to reduce unit cost s, the ef ficient utilisation of produc tion machiner y plays a central role. the higher the achieved deposition rate and operating fac tor, the higher the profitabilit y and the lower these significant cost fac tors and hencefor th the overall cost s. in tig and mig/mag welding, the choice of shielding gas has a signi- ficant effect on both the deposition rate and the operating factor. when a shielding gas enabling a high welding speed is used, the depo- sition rate can be increased, while a shielding gas providing a smooth weld and low-spatter welding improves the operating factor as the amount of post-weld finishing work is reduced. the shielding gas also affects the attained level of quality, which is naturally one of the basic factors when making choices. compared to the achievable cost savings, the price differences of different shielding gases are marginal. investing in the gas that produces the best results with regard to profitability brings savings many times over in the total costs. 4.2 welding process the most common welding process currently used is mig/mag welding. the share of mig/mag welding has more than doubled since 1975. the growth has been at the expense of mma welding an example of the division of welding costs per product unit (unalloyed steel). an efficient method of reducing costs is to select a shielding gas providing a high welding speed and low-spatter welding. one of the reasons for the popularity of mig/mag welding is its high deposition rate, as is evident from the table on the next page. the deposition rate can be further increased by using cored wire in some applications or by using high-productivity welding (rapid processing ® ), to which we will return in section 4.5. the suitability of mig/mag welding for mechanised and robot welding has also affected in its growth. the effect of shielding gas on productivity. capital 12% work 22% energy+others 4% gas 4% gas 4% capital 60% maintenance 3% maintenance 3% filler material 7% filler material 7% work 70% energy+others 4% manual welding mechanised welding
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