The chemistry of the weld differs from that of the electrode wire. The flux covering plays an important role in determining the final chemistry and mechanical properties of the weld. The same core electrode wire is used for many electrode classifications. The actual chemistry of the flux covering is tweaked slightly to compensate for variations in chemistry of the different heats of bare wire that are drawn down to form the electrode. The flux covering contains the components needed to form the slag blanket, the arc stabilizers, the alloy constituents that affect the chemistry and mechanical properties, and deoxidizers to minimize or prevent the formation of porosity. The flux covering can contain iron, manganese, molybdenum, chrome, or nickel to produce a weld with the required composition. The metal alloys added to the flux covering are indicated by the suffix letters and numbers, i.e., -A1, -B2, -C2, etc. As such, the chemistry listed in A5.5 is the chemistry of the weld deposit. That has not changed since AWS published the first A5.5 specification. As a matter of fact, if you read the specification, you will note that the chemistry is that of the last weld layer. Several weld layers are deposited to ensure the weld isn't contaminated (as the result of dilution with the base metal) by the base metal substrate.
This is very different from a bare electrode where the solid wire must contain all the components required to deposit a weld with the required chemistry, mechanical properties, as well as deoxidizes needed to prevent porosity. When welding with bare wire using the oxy-fuel welding, gas tungsten arc or gas metal arc welding processes, a shielding gas is used to displace and exclude air from the area surrounding molten weld pool to eliminate a major source of porosity.
I hope find this explanation useful.
Best regards - Al
Topic American Welding Society Services / Technical Standards & Publications / Hello, and I am Looking for AWS A5.5 Advice
