Heat Treatment, Furnaces & Thermal Processing calculator

Carburizing Cycle Time Calculator

Carburizing cycle time is the total furnace time to case-harden a batch of parts, from charge to quench-ready, including the allowance you add for boost-diffuse soaks, loading, and scheduling slack. Heat treat engineers and gear-shop schedulers use it because carburizing is one of the longest thermal processes on the floor, with deep cases demanding many hours at temperature to reach the required case depth. Getting this number right protects ship dates and prevents a deep-case job from quietly blowing a furnace's weekly capacity. The calculator converts your load count and a realistic completion rate into a committable cycle time.

What this calculator does

  • Estimate carburizing cycle planning time from planned loads, load completion rate, and allowance for boost, diffuse, quench, and handling delays.
  • Use it when carburized gears, shafts, pins, or wear parts need a defensible furnace schedule before release.
  • It computes total carburizing cycle hours by dividing planned loads by the furnace completion rate and applying a cycle allowance factor.

Formula used

  • Base carburizing hours = carburizing loads planned ÷ carburizing completion rate
  • Required carburizing cycle time = base carburizing hours × allowance factor

Inputs explained

  • Carburizing loads planned: Use the planned workload from the traveler, work order, recipe, or test plan.
  • Carburizing completion rate: Use a proven rate from recent thermal processing history, not the best possible rate.
  • Carburizing cycle allowance: Include expected setup, loading, ramp, transfer, inspection, queue, or minor delay allowance.

How to use the result

  • Use it when scheduling case-hardening runs, sizing furnace capacity, or quoting heat treat lead time for carburized gears and shafts.
  • A single completion rate cannot capture how strongly case-depth requirements drive soak time, so deep-case work needs a slower, depth-specific rate.

Current U.S. benchmarks

  • Industrial electricity averages 8.66 cents per kWh across the U.S. (EIA, Apr 2026), up 5.5% from a year earlier. Energy-intensive steps carry this directly into unit cost.

Common questions

  • How do you calculate carburizing cycle time? Divide planned loads by the completion rate for base hours, then multiply by one plus the allowance. With 2 loads at 0.08 loads/hr and a 12% allowance, base time is 25 hr and required cycle time is 28 hr.
  • Why is carburizing so slow? Carbon diffuses into steel slowly. Reaching a deep case can take many hours at 900 to 950 C, which is why a completion rate of 0.08 loads/hr, about one load every 12.5 hours, is realistic for deep-case work.
  • What is a good carburizing completion rate? It scales with required case depth. Shallow cases finish far faster than deep ones; 0.08 loads/hr reflects a long deep-case cycle. Always derive the rate from your own logged soak times at the target depth.
  • Does the cycle time include quench? It should, if your completion rate accounts for it. Quench and any temper handling add real furnace and fixture occupancy, so fold them into loads/hr rather than leaning on the allowance to cover them.
  • Carburizing vs annealing cycle time? Both use the same load-over-rate math, but carburizing is typically far slower because case formation is diffusion-limited. The same two loads might anneal in hours but carburize over a full day.

Last reviewed 2026-05-12.