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added silicon has the effect of making the weld pool more fluid and making it easier to weld . There is even one grade of duplex stainless steel ( 2209 ) that has added silicon for exactly the same reason , 22.8.3 . LSi . Over-alloying the weld filler metal grade for stainless steel can provide several benefits in certain welding applications . This process involves increasing the concentration of alloying elements , such as chromium and nickel , beyond the levels present in the base metal . Here are some advantages of overalloying the weld filler metal : 1 . Enhanced corrosion resistance : Stainless steel is known for its corrosion-resistant properties , and over-alloying the filler metal can further enhance this characteristic . By increasing the chromium content , the passive oxide layer formed on the weld surface becomes thicker and more protective . This offers superior resistance to various corrosive environments , including high-temperature and highly corrosive applications .
2 . Improved mechanical properties : Over-alloying the weld filler metal can also lead to improved mechanical properties of the weld joint . By increasing the concentration of nickel and other alloying elements , the weld can exhibit higher tensile strength , toughness , and resistance to deformation . This is particularly beneficial in structural applications where strength and durability are crucial .
3 . Matching or exceeding base metal properties : In some cases , the base metal used in a welding application may have higher alloying element content than the standard filler metal grade . In such situations , over-alloying the weld filler metal ensures that the weld joint matches or exceeds the properties of the base metal . This helps maintain consistency and integrity throughout the welded structure .
4 . Compensation for dilution : During the welding process , the base metal and filler metal mix together , leading to dilution of the alloying elements . Over-alloying the filler metal compensates for this dilution , ensuring that the resulting weld joint maintains the desired composition and properties . It is worth noting that over-alloying the weld filler metal should be done with careful consideration of the specific welding application and the requirements of the final product . Balancing the alloying element concentrations is crucial to avoid potential issues such as hot cracking , reduced weld ductility , or increased sensitivity to intergranular corrosion . It cannot be emphasised enough that following the correct procedure with the correct filler metals and shielding gas as described in the weld qualification is important . Further , operators need to train as if they were welding on the job , working with the exact base materials , filler metals , equipment and weld procedure specification ( asking your operators to train on anything less is like expecting an F1 driver to train on a lorry ). Operators have to develop welding techniques that produce successful results , practice them until they become second nature and then trust in those techniques in the field — which we ’ ll discuss in the next article !
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