Carbon equivalent calculator
The carbon equivalent tells whether a carbon or low-alloy steel needs preheat for welding. Pick the steel from the catalog or enter the composition from the certificate.
1You enter (wt. %)
Typical composition = middle of the standard's ranges; for residuals with only a maximum (Cr, Ni, Cu in A105), half the maximum. Use the certificate composition for the actual value.
Carbon equivalent of the catalog steels
| Steel | Worst-case CE | Typical CE | Typical Pcm | Note |
|---|---|---|---|---|
| ASTM A182 F1 | 0.56 | 0.37 | 0.222 | Good weldability |
| ASTM A694 F65 – High-yield steel forging | 0.57 | 0.28 | 0.198 | Good weldability |
| ASTM A105 – Forged carbon steel for piping | 0.68 | 0.39 | 0.253 | With supplementary S4: heat CE ≤ 0.47 (section up to 2 in) · Good weldability |
| ASTM A182 F11 Class 2 | 0.76 | 0.60 | 0.301 | High preheat and post-weld heat treatment |
| SAE 9315 – AMS 6263 | 0.83 | 0.73 | 0.313 | High preheat and post-weld heat treatment |
| SAE 4140 | 0.87 | 0.78 | 0.518 | High preheat and post-weld heat treatment |
| ASTM A522 Type I – 9% Ni steel | 0.91 | 0.74 | 0.245 | Outside IIW CE validity: preheat per code (P-No.) |
| SAE 4340 | 0.94 | 0.85 | 0.535 | High preheat and post-weld heat treatment |
| 8550 steel – 34CrAlNi7-10 (W.Nr. 1.8550) | 0.97 | 0.86 | 0.482 | High preheat and post-weld heat treatment |
| ASTM A182 F22 / P22 (2¼Cr-1Mo) | 0.98 | 0.83 | 0.310 | High preheat and post-weld heat treatment |
| 300M steel (modified 4340) | 1.05 | 0.93 | 0.612 | High preheat and post-weld heat treatment |
| ASTM A182 F5 | 1.61 | 1.28 | 0.396 | Outside IIW CE validity: preheat per code (P-No.) |
| ASTM A182 F91 Type 1 | 2.41 | 2.17 | 0.660 | Outside IIW CE validity: preheat per code (P-No.) |
| ASTM A182 F9 | 2.47 | 2.15 | 0.639 | Outside IIW CE validity: preheat per code (P-No.) |
| Maraging 250 | 2.49 | 2.27 | 0.671 | Outside IIW CE validity: preheat per code (P-No.) |
* Values to be confirmed in the current edition of the standard or of the applicable welding code.
Worst-case CE = all elements at the standard maximum at the same time (in practice the heat is well below); typical = middle of the ranges. Stainless, duplex, nickel alloys, titanium and copper do not use carbon equivalent: for them see the PREN calculator.
How to interpret
| CE | Weldability | Precaution |
|---|---|---|
| up to 0.40 | Good | Usually no preheat needed |
| 0.40 to 0.45 | Fair | Preheat depending on thickness |
| 0.45 to 0.60 | Needs control | Preheat, low-hydrogen electrode |
| above 0.60 | Difficult | High preheat and post-weld heat treatment |
Reference ranges. The preheat temperature also depends on thickness, consumable hydrogen and joint restraint (AWS D1.1 Annex H, EN 1011-2).
Frequently asked questions
What is carbon equivalent?
It is a weldability index for carbon and low-alloy steel: it adds up the effect of carbon and alloying elements on hardening of the heat-affected zone. IIW formula: CE = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15. Up to 0.40 welding usually needs no preheat; above 0.45 preheat and hydrogen control are required.
Which materials use carbon equivalent?
Carbon steel (A105, A350 LF2), hardenable low-alloy steels (4140, 4340, 9315) and low-chromium Cr-Mo (F1, F11, F22). For 5Cr, 9Cr, F91 and 9 % Ni steels the IIW CE falls outside its validity range: preheat follows the code (ASME B31.3 and Section VIII) by P-Number. Stainless, duplex and nickel alloys do not use CE.
Does A105 have a carbon equivalent limit?
When the purchaser orders supplementary requirement S4 (Carbon Equivalent) of ASTM A105 / ASME SA-105, the heat analysis CE, by the IIW formula, is limited to 0.47 for sections up to 2 in (50.8 mm) and to 0.48 above that. A lower limit, such as 0.43, may be agreed between purchaser and supplier (S4.3). Without S4 in the order, the standard does not limit CE.
When to use Pcm instead of CE?
For steels with carbon up to about 0.12 %, such as modern pipeline and structural steels. Pcm (Ito-Bessyo) gives more weight to carbon and boron. Usual limit: up to 0.20 to 0.25*.
