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4.4.0.1The letter-number designations for low alloy electrode classifications mean muchthe same as with mild steel electrodes, except that the major alloy composition is indicated bya letter-number suffix.  For example, E7018-A1 indicates an electrode (letter E); with a mini-mum of 70,000 psi tensile strength (70); is weldable in all positions (1); is iron powder lowhydrogen (8); and contains nominally 1/2% molybdenum (A1).  The full list of nominal alloycompositions for this specification is contained in Table 1.

A1  1/2% Molybdenum

B1  1/2% Chromium, 1/2% Molybdenum

B2  1-1/4% Chromium, 1/2% Molybdenum

B2L  Low Carbon version of B2 type.  Carbon content is 0.05% or less

B3  2-1/4% Chromium, 1% Molybdenum

B3L  Low Carbon version of B3 type.  Carbon content is 0.05% or less

B4L  2% Chromium, 1/2% Molybdenum, low carbon (0.05% or less)

B5  1/2% Chromium, 1.1% Molybdenum

C3  1% Nickel

C1  2% Nickel

C2  3% Nickel

D1  1-1/2% Manganese, 1/3% Molybdenum

D2  1-3/4% Manganese, 1/3% Molybdenum

M Conforms to compositions covered by Military specifications.

G  Needs only a minimum of one of the elements listed in the AWS A5.5 Tablefor Chemical Requirements.

4.4.1Effect of Alloying Elements

4.4.1.1Molybdenum - When mild steel weld metal is stress relieved, the yield point islowered 3,000 psi or more and the tensile strength is also lowered 3,000 psi or more.  When1/2% of molybdenum is added to the weld, both the yield point and the tensile strength remainconstant from the as-welded to the stress relieved condition.  The presence of molybdenumalso increases the tensile strength of the weld metal.