Carburizing Case Depth Calculator

Inputs

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The classic Harris rate constants. 1700 °F (927 °C) is the most common gas-carburizing setpoint.
Carburizing (boost+diffuse) time at the set temperature, hours.
h
Desired total case depth; the calculator returns the furnace time it costs.
mm

Results

Default result
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Total case depth(d)
1.796mm
Pass

d = K·√t — the total (visual) case.

Also computed

Effective case (est.)(d_eff)1.257mm

Effective case (to 50 HRC) runs roughly 2/3-3/4 of total; confirm by microhardness traverse, not by this screen.

Customary screening estimate ≈ 0.7 × total; the 50 HRC effective case is what drawings usually specify.

Time for target depth(t_req)2.48h

(d_t / K)² — note the square: doubling depth quadruples time.

Rate constant used(K)0.635mm/√h

Method notes 4 notes
  • Harris √t screening for gas carburizing of plain-carbon and low-alloy steels at carbon-saturation atmosphere. Boost/diffuse cycles, carbon potential control, alloy content (Cr, Mo raise hardenability but slow diffusion little; Ni dilutes), and quench practice all move real results.
  • Total case = depth to base-carbon; effective case = depth to 50 HRC after quench. Drawings usually call the effective case — quote the heat treater the drawing value and the steel grade.
  • The √t law means the last tenth of a millimeter is the expensive one: doubling depth quadruples furnace time.
  • Vacuum/low-pressure carburizing and carbonitriding follow different kinetics; use supplier data there.

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