filler metal selection 1

[fazel1]

when welding 2 different pNo. metals such as PNo=1 & PNo=4
how can we choose filler metal. in AWS D1.1 there is a subject about undermatchig and overmatching filler metals.
is there such this subject in ASME code? please guide me.

 

[metengr]

There is no specific recommendation in ASME code for optimum filler metal selection. The designer is on their own. In your case you have several options for filler metals based on the alloy content and strength of the lower of the two P-No's (P-No1) or the higher strength and alloy content of the two P-No's (P-No 4). Most people tend to use the higher alloy and strength P-No material in a weld joint for selection of the filler metal.

 

[fazel1]

thank you dear metenger . but what is the reason for choosing higher alloy? if you consider the load , there's no need to have the weld metal which has more strengh than one of the base metals. and also welding the high grade filler metals are more difficult and needs more consideration.

 

[ijzer]

I noticed that most of our USA sub-vendors use the higher alloyed of the two and most of the European sub-vendors use the lower alloyed.

 

[metengr]

Actually, your second comment is not entirely correct. The preheat and PWHT requirements for the weld joint really have more to do with the base metal composition versus the weld metal composition. I really do not see any disadvantage with matching the strength level of the higher base metal.

 

[cpands]

In many piping requests I see the term EFW welds and SAW welds. In many cases the specification request will be EFW to API5LB/42 or SAW to A672 but my understanding is the correct requirement should be SAW to API and EFW to A672.
My question, are these 2 weld procedures considered the same or essentially produced on the same equipment with very similar procedures.

 

[fazel1]

thank you metenger , you are exactly right and the consideration for pwht are related to base metal , not weld metal , but the chance for martensitic structure is more for the more hardenable materials.