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Wrap-up

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Lesson 03·Running Forge Dies

Die-temperature management during the run: thermal profiling in plain English

Read a die-surface thermal trace, hold the H13 operating window, and use a contact pyrometer and an IR gun without lying to yourself about what either one is measuring.

7 min readLesson 3 of 13

Tying it together

What this means on the shop floor

For closed-die forge, the working trend point is the back corner of the impression and the parting-line region. Both run hot relative to the rest of the die. Pick the hotter of the two as the shift-log point.

For upsetters and hot-headers, the punch face and the die-cavity floor are the trend points. Punch faces over-temper first because they see contact on every cycle without much radiative relief.

For ring-roll dies, the work-roll face and the mandrel are the trend points. The mandrel sees sustained contact and is the harder of the two to cool.

Across all of these, the absolute temperature on the IR gun is approximate. The shift-to-shift change at the same point with the same tool is real.

Internal pushback questions

  1. What is the last tempering temperature on every active die in the shop, and is that number written on the die itself or only buried in the heat-treat certificate?
  2. When was the IR gun on the floor last gut-checked against a contact pyrometer, and is the emissivity setting recorded somewhere the next shift can find it?
  3. Where on each die is the operator supposed to take the shift-log reading, and is that point the hottest part of the die or just the easiest one to point a gun at?
  4. If the temperature trend at one point drifts 30°C up across a week with no apparent cause, who is supposed to investigate, and what do they look at first?

Common confusions

The IR gun is not a contact pyrometer at a distance. The two tools measure different things and disagree on every reading without explicit emissivity correction.

A "surface temperature" without a moment in the cycle is meaningless. Contact spike, post-lubricant spray, equilibrium between hits, and end-of-shift drift are four different numbers on the same die in the same minute.

The last tempering temperature is not the operating ceiling. The ceiling is roughly 30°C below it. A die running at exactly its temper temperature is over-tempering on every cycle.

An emissivity setting of 0.95 on the gun is correct for blackbody calibration sources and a few high-emissivity surfaces. It is wrong by 100-200°C of read error on most die surfaces in production.

Up next: thermal cycling and heat checking.

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