Minimum preheat temperature Tp

to EN 1011-2, Annex C.3 (Method B)

Input

Alloying element content in percent by weight.

%
%
%
%
%
%
ml/100 g
mm
kJ/mm

Result

Minimum preheat temperature
61 °C

This is also the minimum interpass temperature — the weld must not fall below it while welding.

Calculated carbon equivalent CET
0.280 %
Plate thickness
30.00 mm
Hydrogen content HD
HD 5.00
Heat input
1.50 kJ/mm

Single-run fillet welds carry lower internal stress; the standard puts the difference at around 60 °C, so about 1 °C here. Whether to make use of this is for the manufacturer to decide.

How the value is made up
Carbon equivalent 195.2 °C
Plate thickness 111.2 °C
Hydrogen content 108.9 °C
Heat input -25.7 °C
Constant term −328,0 °C
Total 61.5 °C

Arithmetic breakdown of equation C.8. Not to be confused with the partial equations C.3 to C.6, which carry constant terms of their own.

Method

This calculator determines the minimum preheat temperature for avoiding hydrogen-assisted cold cracking to Method B of EN 1011-2. Four influences enter: the composition of the parent metal through the carbon equivalent, the plate thickness, the hydrogen content of the weld metal and the heat input. Higher alloying, thicker plate and more hydrogen raise the preheat required; more heat input lowers it.

Tp = 697 · CET + 160 · tanh(d / 35) + 62 · HD0,35 + (53 · CET − 32) · Q − 328

Equation C.8, temperatures in °C, d in mm, HD in ml/100 g, Q in kJ/mm.

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

Equation C.2, contents in percent by weight.

Range of validity

The standard states the equation only within these limits. Outside them this calculator deliberately stops.

Yield strength of the parent metal ≤ 1000 N/mm²
CET 0,20 – 0,50 %
d 10 – 90 mm
HD 1 – 20 ml/100 g
Q 0,5 – 4,0 kJ/mm

It further applies only to steels within the concentration ranges given at the input fields.

Silicon (0.8 % max.), niobium (0.06 %), titanium (0.12 %), vanadium (0.18 %) and boron (0.005 %) do not enter the carbon equivalent but also bound its validity.

Notes for use

Fillet welds. Single-run fillet welds carry lower internal stress than butt welds; the temperature derived for butt welds can be around 60 °C too high for them. This does not hold for multi-run fillet welds, whose stress conditions resemble those of butt welds.

Unequal plate thicknesses. The thicker of the two plates governs.

Carbon equivalent of the weld metal. The calculation assumes the CET of the parent metal exceeds that of the weld metal by at least 0.03 %. Otherwise base the calculation on the CET of the weld metal plus 0.03 %.

Hydrogen content. HD is the diffusible hydrogen in the weld metal in ml per 100 g, determined to ISO 3690. The former calculator referred to DIN 8572, which has been withdrawn.

What has changed against the previous calculator
  • Results that call for no preheating are stated as such. Previously a negative temperature appeared — about “−45 °C” on the old page’s own default values.
  • The constants of the standard are used (697 and 328) rather than rounded ones (700 and 330). Results are 0.5 to 1.4 °C higher.
  • Heat input is accepted from 0.5 kJ/mm; previously only from 1.0. The standard gives 0.5 to 4.0.
  • The CET range is 0.20 to 0.50 instead of 0.18 to 0.45, as the standard states it.
  • If the analysis yields a CET outside the range of validity this is reported, even where every single value is permissible on its own.
  • Faulty entries are named field by field; empty fields no longer break the page.

EN 1011-2:2001+A1:2003, Annex C.3 · CET to equation C.2 · hydrogen content to ISO 3690