What Is Carbon Equivalent?
Carbon equivalent (CE) is a single number that summarizes how a steel's alloy chemistry affects its weldability and its tendency to harden after welding. The more carbon and alloying elements a steel contains, the higher its CE and the more likely the heat-affected zone is to form hard, crack-prone microstructures.
The AWS D1.1 formula gives the most weight to carbon and adds smaller contributions from manganese, silicon, chromium, molybdenum, vanadium, copper, and nickel. Structural steels with a CE below about 0.40 are generally considered readily weldable without special preheat, while higher values call for preheat and carefully controlled welding procedures.
Formula
CE = C + (Mn + Si) ÷ 6 + (Cr + Mo + V) ÷ 5 + (Cu + Ni) ÷ 15
Applications
- Assessing whether a steel plate needs preheat before welding
- Reviewing mill certificates for weldability
- Qualifying welding procedure specifications for structural steel
- Comparing steels when a substitute material is proposed
- Troubleshooting hard-zone cracking in fabrication shops
Sources
- American Welding Society (AWS). AWS D1.1/D1.1M — Structural Welding Code — Steel.
- Lincoln Electric. Carbon Equivalent and Weldability guidance.