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Calcimator

Preheat Temperature Calculator

Determine preheat and interpass temperatures based on carbon equivalent (CE) and material thickness using the IIW formula.

Inputs

%
%
%
%
%
in

Results

Carbon Equivalent (CE)

0.33

Preheat Temperature

0 °F

Preheat Temperature-18 °C
Max Interpass Temperature200 °F
Weldability Rating1 (1=Good, 2=Fair, 3=Difficult)
How to Use This Calculator
  1. Enter the steel chemistry percentages: carbon (C), manganese (Mn), chromium (Cr), molybdenum (Mo), and nickel (Ni).
  2. Enter the material thickness at the joint in inches.
  3. Read Carbon Equivalent (CE) — values above 0.42 indicate higher preheat requirements.
  4. The required preheat temperature is calculated from CE and thickness; apply this temperature to the joint before welding.
  5. Maintain the preheat temperature as the interpass temperature throughout the weld to prevent cracking.
  6. If CE is very high (>0.70) or thickness is large, consider using the PWHT Calculator for post-weld heat treatment requirements.

How the result changes with Carbon (C) %

Carbon (C) %Carbon Equivalent (CE)Preheat Temperature
0.10.230 °F
0.350.48258 °F
0.650.78600 °F
0.91.03600 °F

What each input means

Carbon (C) %
Carbon content of the base metal as a decimal percent.
Manganese (Mn) %
Manganese content of the base metal.
Chromium (Cr) %
Chromium content of the base metal.
Molybdenum (Mo) %
Molybdenum content of the base metal.
Nickel (Ni) %
Nickel content of the base metal.
Material Thickness
Thickness of the base metal being welded.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Carbon (C) % = 0.2, Manganese (Mn) % = 0.8, Chromium (Cr) % = 0, Molybdenum (Mo) % = 0 = 6 input(s) provided
  2. Calculate Carbon Equivalent
    Carbon Equivalent
    0.333 = 0.333
  3. Calculate Preheat Temperature
    Preheat Temperature
    0 = 0
  4. Calculate Preheat Temperature
    Preheat Temperature
    -18 = -18
  5. Calculate Max Interpass Temperature
    Max Interpass Temperature
    200 = 200

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