2 This
formula is valid when the percentages are within this range:
% carbon less than 0.50
% manganese less than 1.60
% nickel less than 3.50
% molybdenum less than 0.60
% chromium less than 1.00
% copper less than 1.00
The table below gives the suggested
preheat treatment for different values of carbon equivalent.
Carbon Equivalent (%) Recommended Treatment
Up to 0.30 Preheat
optional 0.30
to 0.45 Preheat at 200 to 400o F
Above 0.45 Preheat
at 400 to 700o F Some
steels, particularly those having carbon equivalent greater than 0.45%, may require
postheat as well as
preheat. This is particularly true in welding heavy sections. However, for most
plain carbon and alloy steels,
only preheat is needed if any treatment is required at all.
Preheating from 250-300 degrees F is
also generally used when multipass welding sections greater than 1
inch thick to reduce weld cracking
susceptibility.
Carbon = %C + %Mn
+ %Ni
+ %Mo + %Cr + %Cu
Equivalent 6
15 4
5
13
