©
COPYRIGHT 2000 THE ESAB GROUP, INC. LESSON
IV ments and stress
relieved condition, the chemical requirements, and the weld metal sound-
ness requirements. Electrodes
are classified under this specification according to the me-
chanical properties and chemical composition
of the weld metal, the type of covering, and the welding
position of the electrode. The classification of the electrode is designated
by the manufacturer
according to the results of his own tests. The manufacturer, thereby, guarantees
his electrode to meet the requirements
of the AWS specification. 4.4.0.1
The letter-number designations for
low alloy electrode classifications mean much the
same as with mild steel electrodes, except that the major alloy composition is
indicated by a
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 low hydrogen
(8); and contains nominally 1/2% molybdenum (A1). The full list of nominal
alloy compositions
for this specification is contained in Table 1. 4.4.1
Effect
of Alloying
Elements 4.4.1.1
Molybdenum - When
mild steel weld metal is stress relieved, the yield point is
lowered 3,000 psi or more and the tensile
strength is also lowered 3,000 psi or more. When 1/2%
of molybdenum is added to the weld, both the yield point and the tensile strength
remain constant
from the as-welded to the stress relieved condition. The presence of molybdenum
also increases the tensile strength
of the weld metal. TABLE
1. Nominal Alloy Designations for AWS A5.5 Specification
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 Table for
Chemical Requirements.
