FILARC flux - Esab

FILARC flux- andmetal- coredwelding wiresFILARC metal-cored wires fordissimilar and armour steelsContents page 4Previous pageNext pageWhen stainless steel must be welded tomild or low-alloyed steels, for instance astainless steel container with mild steelreinforcement strips, the filler weld metalmust be carefully selected.As a general rule, the chemical compositionof the weld must avoid, as far as possible,martensite formation or a fullyaustenitic structure. The accompanyingSchaeffler diagram is very useful forselecting a suitable filler metal. Followingis a typical example of its use.Example:Consider a V-joint between two plates;one type AISI 318 (no official type butcommonly used), the other mild steel Fe410, with chemical compositions shown.The composition of the weld pool is governedby the chemical composition of thefiller material and the amount of the parentmetal is calculated by taking a linebetween point C and the filler material'sSchaeffler equivalent and moving the latter30% of the line length towards C, indicatedby points D and D 1 on the diagram.If PZ 6410 (308 type) is selected as thefiller material, resulting point D indicates ahigh chance of martensite formation.Use of PZ 6414 (309L type) as filler material,with resulting point D 1 , will produce theideal weld metal structure: an austeniticmatrix containing some 6% ferrite.Primarily developed for welding armoursteels, PZ 6470 is also a good option forwelding dissimilar steels. Strictly speaking,the Schaeffler diagram is not valid for highmanganese weld metal compositions,although it will rightly indicate a fullyaustenitic weld. Normally, a fully austeniticweld entails a risk of hot cracking.Steel type Chemical composition, % Schaeffler EquivalentC Mn Si Cr Ni Nb Nb Cr eq Ni eqAISI 318 0.062 1.21 0.62 18.2 11.8 2.8 0.64 21.75 14.2Fe 410 0.11 0.4 0.3 – – – 0.45 3.5The Cr and Ni equivalents are plotted on the Schaeffler diagram, next page; AISI 318point A, Fe 410 point B.Cr equiv. = Cr% + Mo% + 1,5 Si% + 0,5 Nb%Ni equiv. = Ni% + 30 C% + 0,5 Mn%metals melted from the two plates.Assuming equal contribution of both parentmetals, the point C midway between Aand B indicates their combined contribution.Under normal welding conditions the parentmetal will dilute the filler material by30%. The final composition of the weldIn the case of FILARC PZ 6470, however,5.5-7.0%Mn alloying protects the weldsufficiently against hot cracking.88