MachineCalcs

Carbon Equivalent Calculator

Calculate steel weld carbon equivalent, Pcm and CET from chemistry, then compare CE and Pcm against user-entered procedure limits for weld preheat screening.

Fasteners 11 inputs 7 results
Common paths weld preheat by carbon equivalent to Check heat input carbon equivalent welding setup to Set amperage weld filler takeoff to Estimate deposited metal

Calculator

Inputs

View results
Carbon content by mass percent from the mill test report.
%
Manganese content by mass percent.
%
%
%
%
%
%
Silicon is used by Pcm. It is not part of the IIW CE formula.
%
Boron is small but heavily weighted in Pcm. Enter mass percent, not ppm.
%
Procedure, project or shop screening limit to compare against CE/CEV. This is user-entered because code and WPS rules differ.
%
Procedure, project or shop screening limit to compare against Pcm. This is not a built-in code limit.
%

Results

Default result
Edit inputs
CE / CEV(CE)
0.336%
Pass

within entered CE limit

C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15.

Also computed

Pcm(Pcm)Pass0.2265%

within entered Pcm limit

CET(CET)0.2608%

CE limit margin(CE_lim - CE)0.064%

Pcm limit margin(Pcm_lim - Pcm)0.0235%

Controlling ratio(max(r))0.906x

Preheat attentionPass0band

within entered limits

0 within entered limits; higher bands need procedure review.

Method notes 3 notes
  • Inputs are chemistry mass percentages from an MTR or verified material specification.
  • The CE and Pcm limits are user-entered comparison limits; the calculator does not embed code, WPS or customer preheat tables.
  • Higher carbon equivalent means higher hardenability risk, but real preheat also depends on thickness, hydrogen level, heat input, restraint, joint detail, ambient temperature and procedure qualification.

Carbon equivalent condenses steel chemistry into weldability screens. This calculator reports IIW CE/CEV = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15, Pcm = C + Si/30 + (Mn+Cu+Cr)/20 + Ni/60 + Mo/15 + V/10 + 5B, and CET = C + (Mn+Mo)/10 + (Cr+Cu)/20 + Ni/40, then compares CE and Pcm against user-entered procedure limits for preheat attention.

Continue workflow

All Fasteners
Next 1 Check heat input Carry chemistry risk into procedure variables by checking voltage, current, travel speed and efficiency. Next 2 Set welding amps Choose starting current and process setup separately from base-metal chemistry. Next 3 Estimate groove area Estimate groove volume after chemistry and preheat screening are separated from filler quantity. Chart Use reference data Weld symbol reference

How to use this calculator

  1. Enter chemistry. Use mass-percent values from the mill test report or verified material specification.
  2. Enter comparison limits. Use the CE and Pcm limits required by your WPS, project rule or shop screening practice.
  3. Read the margins. Positive margins are within the entered limits; negative margins need procedure review.
  4. Treat preheat as procedure-controlled. Use the attention band as a screen, then check the actual WPS/code preheat requirements.

How it works

Carbon-equivalent formulas condense steel chemistry into a weldability screen. The common IIW/CEV expression is:

CE = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15

The calculator also reports Pcm and CET:

Pcm = C + Si/30 + (Mn + Cu + Cr)/20 + Ni/60 + Mo/15 + V/10 + 5B

CET = C + (Mn + Mo)/10 + (Cr + Cu)/20 + Ni/40

The entered CE and Pcm limits are comparison values from your procedure basis. The preheat attention band is derived from the worse ratio of calculated value to entered limit.

Worked example

Verified against the live calculator

For C = 0.16%, Mn = 0.90%, Cr = 0.05%, Mo = 0.02%, V = 0.01%, Ni = 0.05% and Cu = 0.10%, the IIW carbon equivalent is 0.16 + 0.90/6 + (0.05 + 0.02 + 0.01)/5 + (0.05 + 0.10)/15, or 0.336%. Against an entered 0.40% CE limit, the margin is 0.064%.

Frequently asked questions

How do you calculate carbon equivalent for welding?

A common IIW/CEV screen is CE = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15, with all chemistry entered as mass percent. This calculator also reports Pcm and CET because different procedure bases may use different carbon-equivalent formulas.

Can carbon equivalent tell me the exact preheat temperature?

No. Carbon equivalent is a weldability and hardenability screen. Exact preheat depends on the governing WPS, code, base metal, thickness, hydrogen level, restraint, heat input, ambient temperature and customer requirements.

Why are there entered CE and Pcm limits?

Limits vary by procedure basis and project rules, so the calculator compares against the limits you enter instead of hard-coding a code table.

What is Pcm used for?

Pcm is often used for low-carbon and microalloyed steels where small alloy additions, silicon and boron matter. Use the formula required by your WPS, material specification or project requirement.

Method & assumptions

  • All chemistry inputs are mass percent, not decimal fractions. Enter 0.16 for 0.16% carbon.
  • CE/CEV, Pcm and CET are screening formulas. Use the formula named by the governing WPS, customer rule or material requirement.
  • The CE and Pcm limits are user-entered. This page does not publish preheat tables, acceptance limits or code requirements.
  • Production welding still depends on thickness, hydrogen control, consumables, heat input, interpass temperature, restraint, joint detail, qualification, inspection and the adopted code.
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