CEMP-E
TI 809-26
1 March 2000
(8) Vanadium (V) is an alloying element used for increasing strength and hardenability. Weldability
may be reduced by vanadium. When vanadium is reported as a part of steel composition, vanadium is
generally limited to a maximum value between 0.06% and 0.15%.
(9) Molybdenum (Mo) is an alloying element which greatly increases hardenability and helps
maintain strength and minimize creep at higher temperature. When molybdenum is reported as a part of
steel composition, it is generally limited to a maximum value between 0.07% and 0.10%.
(10) So-called "tramp" elements such as tin (Sn), lead (Pb), and zinc (Zn), may be present in steel
from the scrap material melted for steel-making. They have a low melting point, and may adversely
affect weldability and cause "hot" cracking. Other low-melting point elements that create a risk of hot
cracking include sulfur, phosphorous, and copper. When welding with high levels of these elements, it
may be necessary to use low heat input welding procedures to minimize dilution effects.
b. Carbon Equivalency. The weldability of a steel can be estimated from its composition, using a
calculation system termed the carbon equivalent (CE). The most significant element affecting weldability
is carbon. The effects of other elements can be estimated by equating them to an additional amount of
carbon. The total alloy content has the same effect on weldability as an equivalent amount of carbon.
There are numerous carbon equivalent equations available and in use.
(1) The following equation is used in AWS D1.1 Annex XI.
CE = C + Mn/6 + Cr/5 + Mo/5 +V/5 + Ni/15 + Cu/15 + Si/6
Where
C = carbon content (%)
Mn = manganese content (%)
Cr = chromium content (%)
Mo = molybdenum content (%)
V = vanadium content (%)
Ni = nickel content (%)
Cu = copper content (%)
Si = silicon content (%)
A carbon equivalent of less than 0.48 generally assures good weldability.
(2) Another common carbon equivalent equation is:
CE = C + Mn/6 + Cr/10 + Ni/20 + Cu/40 - V/10 - Mo/50.
If the CE from this equation is below 0.40, the material is considered readily weldable, and AWS D1.1
Table 3.2 guidance for the given steel strength should be adequate. For values between 0.40 and 0.55,
the use of preheat and low-hydrogen electrodes is generally necessary, regardless of thickness. Carbon
equivalent values above 0.55 indicate a high risk that cracks may develop unless special precautions are
implemented.
(3) The Dearden and O'Neill equation, applicable for steels with C greater than 0.12%, is similar:
CE = C + Cr/5 + Mo/5 + V/5 + Mn/6 + Ni/15 + Cu/15
A CE of 0.35% or lower is considered a steel with good weldability
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