How it Works: Why Buttering on Dissimilar steels is often suggested?

Why Buttering on Dissimilar steels is often suggested?

Used when the mixture of one or both parent material(s) and filler create an undesirable microstructure for the application.

Buttering is used to create a transition of composition and properties across the joint such that the resulting connection has properties suitable for the application.  It is also used when a composition transition in overlay applications is needed to produce a final layer of required performance.

One material is covered with one or more layers of a compatible alloy to create a composition on the transition face which is compatible with the main filler alloy or the adjoining parent material

Pick up (mixing) of one or other parent materials can create undesirable connection performance such as;

• Loss of strength

• Loss of toughness

• Loss of ductility

• Loss of hot cracking resistance

• loss of corrosion resistance

• loss of heat resistance

• loss of abrasion resistance

A classic example is welding a Carbon-Manganese steel to an Austenitic Stainless steel. (Eg. A516 to 304L) If welded with a mild steel electrode, the weld would be composed of a hard martensitic structure.  If the A516 were “buttered” with 309 (an alloy tolerant of some dilution by carbon-manganese steel) it may be possible for the remaining weld to be made with a lower cost 308L filler.  The 308L filler being compatible with both 309 and 304L compositions.