Avesta filler metals for similar welding
Avesta filler metals for dissimilar welding
Similar welding
When welding two identical stainless steels to each other, the choice of filler metal is generally determined by the parent metal. To ensure that the weld has the optimum corrosion performance and mechanical properties, the chemical composition of the filler metal must be related to the properties of the steel being welded. Thus, to compensate for losses in the arc, and for segregation of alloying elements in the weld during cooling, the filler metal’s content of alloying elements (Cr, Ni, Mo and Mn) is normally higher than that of the workpiece.
There are, however, some exceptions to this latter generalisation. For example, in nitric acid or citric acid environments, the resistance of molybdenum free steels is better than that of molybdenum alloyed steels. Consequently, filler metals may here have a lower alloy content than the workpiece.
Hence, whilst there are standard recommendations, every case must be considered on its merits. Using a filler metal that is more highly alloyed than the parent metal is not normally a problem. However, the higher the alloy content, the higher the price.
Avesta filler metals for similar welding lists the recommended filler metals for use with most common stainless steels. Provided the chemical composition is the same, other consumables (those with 2D,3D, 4D designations, etc.) can also be used.
In some specific instances, for example cryogenic applications with severe demands as regards toughness at low temperatures, alow/zero ferrite filler might be necessary. Avesta Welding produces different types of low or non-ferritic consumables such as MMA 308L-LF and SKR-NF.
For use in very corrosive environments, e.g. urea plants, specially designed consumables can also be requested. Avesta Welding produces a wide range of consumables for specific applications. For details, see Product data sheets.
Dissimilar welding
When welding two different stainless steels to each other, the choice of filler metal is normally determined by the more highly alloyed of the two parent metals. For example, when welding1.4307/ASTM 304L to 1.4404/ASTM 316L, a 316Ltype filler should be used. However, as shown in table 12.2, there are exceptions. To obtain a crack-resistant weld metal when welding stainless steel to mild steel, an over-alloyed and high ferrite electrode, e.g. P5 (309LMo) or 309L, should be used. If the ferrite content is too low (below 3%), the risk of hot cracking increases (see also chapter 1,“Stainless steels; Ferrite and its importance”).
When welding stainless steel to unalloyedor low-alloy steels, it is generally advisable toreduce weld dilution as much as possible.Thus, heat input must be limited (max 1.5kJ/mm) and an appropriate bevel angle hasto be selected for the joint. The interpass temperature must not exceed 150°C.
As always, due to the significant risk of pore formation, welding to a C-Mn steel that has a coating of prefabrication primer shouldbe avoided. Where it is unavoidable, the paint must be removed from the surfaces in a radius of up to 20 – 30 mm of any part of the proposed weld.
Avesta filler metals for dissimilar welding lists filler metals for the dissimilar welding of many different combinations of stainless, low-alloy and nickel base steels. If two filler metals are suitable, the upper one should be considered as the first choice. Provided the chemical composition is the same, other consumables (those with 2D, 3D,4D designations, etc.) can also be used. If you need further information, please contact your nearest Avesta Welding representative for advice, or send an enquiry direct to our experts in Avesta.
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