Heat Treatment Furnace Load Worksheet: Load Weight and Soak Time Planning
A heat treat load sheet decides what goes into the furnace together and for how long. Mistakes cause under-soaked parts, mixed processes and overloaded baskets. This worksheet totals weight and gives a planning soak time that you can edit and export to Excel.
| Part number | Process | Pieces | Unit weight (kg) | Max section (mm) | Soak min per mm | Load weight (kg) | Soak (min) | Set point (C) | |
|---|---|---|---|---|---|---|---|---|---|
248 | 91 | ||||||||
248 | 91 | ||||||||
216 | 29 | ||||||||
362.5 | 144 | ||||||||
330 | 60 |
Group parts in one furnace charge only when process, set point and atmosphere match. Compare total load weight with the furnace rated load and fixture weight. Soak is a planning figure only; the controlling soak comes from the specification and thermocouple data.
Furnace loads linked to ERP operations
Optional: a review of how loads, lots and certificates can be linked in your ERP.
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How to use the worksheet
Add one row per part per process step. Enter piece count, unit weight, the thickest section and a soak rule in minutes per millimetre. The sheet computes load weight and soak for each row, plus total pieces, total weight and the longest soak. Use the longest soak as the minimum for a combined charge, and keep only compatible set points together. Delete the example rows and paste your own, or export to Excel and continue there.
Where the soak rule comes from
Many shops start from one hour per inch of thickness, about 2.4 minutes per millimetre, as a planning guide for through heating of steel. Real soak depends on the specification, alloy, load density and fixture. Aerospace work follows the customer specification and pyrometry rules such as AMS2750, with time starting when the coldest load thermocouple reaches the set point. Carburizing and nitriding time is driven by case depth, not section size, so adjust the rule per process.
- Start soak time when the load thermocouple reaches temperature
- Dense loads need longer heat up than open baskets
- Case depth, not thickness, drives carburizing time
Reading the totals
Compare total load weight to the furnace rated load, including baskets and fixtures, which can be a third of the charge. If the load exceeds the rating, split it and schedule two charges. If one thick part forces a long soak on many thin parts, split the charge by section size to avoid over-soaking, which can increase grain growth, decarburization and distortion. The average weight per piece helps spot a wrong unit weight entry.
Common mistakes and ERP notes
Mixed alloys, different quench media and unrecorded fixture weight are the usual faults. Hardness requirements and load identification must stay traceable to the certificate. In the ERP, heat treat is often an outside process operation or an in-house work centre; capture furnace, load number and cycle recipe on the operation so the certificate can pull the data instead of retyping it.
Frequently Asked Questions
How long should parts soak in the furnace?
The specification controls it. As a planning rule many shops use about one hour per inch of thickness for through heating of steel, starting when the coldest part of the load reaches temperature. Always confirm with the written procedure.
Can I mix different parts in one furnace load?
Yes, if they need the same temperature, atmosphere, quench and a compatible soak time, and if the customer allows mixed loads. Keep records that tie each part and lot to the load number.
Does this include the weight of baskets and fixtures?
Not by default. Add fixtures as rows with their own weight so the total reflects what the furnace and hearth actually carry, and compare with the rated load.
Can I export the load sheet?
Yes. Use the Excel or CSV export to keep the sheet or print it as a PDF traveler. The soak and weight columns are recalculated from the values in the export.
If load sheets live in spreadsheets, we can help connect furnace loads and certificates to the operations and lots in your ERP.
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