What is the carbon equivalent of API 5L X52?

There are generally two common ways to express the carbon equivalent of API 5L X52 steel and the range of values:
The calculated value of the carbon equivalent formula of the International Institute of Welding (IIW): For API 5L X52, its carbon equivalent CE (IIW) usually does not exceed 0.43%. The calculation formula of carbon equivalent is that carbon equivalent (CE (IIW)) is equal to the carbon (C) content plus one-sixth of the manganese (Mn) content, plus one-fifth of the total content of chromium (Cr), molybdenum (Mo), and vanadium (V), and one-fifteenth of the total content of nickel (Ni) and copper (Cu). The carbon equivalent value calculated by this formula can be used to evaluate the hardening tendency and cold crack sensitivity of steel during welding. For example, when the carbon equivalent is high, the heat-affected zone of the steel is more likely to have hardened structure during welding, thereby increasing the possibility of cold cracking.
Calculated value of the carbon equivalent formula of the Japanese Industrial Standard (JIS): The carbon equivalent (Ceq) calculated according to the carbon equivalent formula of the JIS standard is equal to the carbon (C) content plus one-sixth of the manganese (Mn) content, plus one-twenty-fourth of the silicon (Si) content, plus one-fortieth of the nickel (Ni) content, plus one-fifth of the chromium (Cr) content, plus one-fourth of the molybdenum (Mo) content, and one-fourteenth of the vanadium (V) content. The carbon equivalent of API 5L X52 generally does not exceed 0.25%. This carbon equivalent value is of great reference significance for judging the performance changes of steel after welding, especially in terms of toughness and crack resistance. For example, if the carbon equivalent is too high, the toughness of the heat-affected zone after welding may be significantly reduced, which may easily lead to problems such as brittle fracture of the welded joint during use.