Measured standard-probe cooling curves
Describes the medium response for the stated probe and test conditions. It is not the surface or core curve of a production workpiece.
Ideal Critical Diameter (DI) Calculator
Assess hardenability potential as a starting point for cooling selection.
Enter heat chemistry and austenite grain size under the quenching heating conditions to estimate DI with this non-boron steel model. DI is the critical round-bar diameter giving 50% martensite at the centre under ideal quenching—not the maximum permissible production size in an actual bath.
DI
=
DIc
×
FMn
×
FSi
×
FCr
×
FNi
×
FMo
×
FCu
×
FV
Geometry
Ideal infinitely long round bar
Microstructural criterion
50% martensite at center
Method status
Empirical multiplying model with validity limits
Input Parameters
Composition (wt%)
Example composition:
Presets only demonstrate data entry; engineering calculations should use the material certificate or measured heat chemistry.
ASTM grain size:
C
0.10 – 0.70
Mn
0.50 – 1.65
Si
0.15 – 0.60
Cr
0 – 1.35
Ni
0 – 1.50
Mo
0 – 0.55
Cu
0 – 0.35
V
0 – 0.20
Calculation Results
Inputs are within the published validity ranges. The result uses the empirical multiplying model for non-boron steel.
Ideal Critical Diameter DI
--
mm
C × grain-size base value = -- in (-- mm)
Alloy Multiplying Factors
| Element | wt% | Multiplying factor FX | Leave-one-out sensitivity |
|---|
Leave-one-out sensitivity (mm, non-additive)
Empirical calculation model · not measured data
Formula: GB/T 5216-2014 Annex A relationship for ideal critical diameter of non-boron steel.
Input limits: Uses the officially published ASTM A255-20a composition ranges; no calculation is made outside them.
Criterion:50% martensite at the center of an ideal round bar; DI is not the hardenable diameter of a production workpiece in an actual quenchant.
How to use the tool and get product support
Inputs
Enter composition in mass percent. Example grades illustrate the inputs; engineering assessment requires actual heat data. Grain size must correspond to the austenitic condition, not simply room-temperature metallographic grain size.
Current range: C 0.10–0.70%, Mn 0.50–1.65%, Si 0.15–0.60%, Cr≤1.35%, Ni≤1.50%, Mo≤0.55%, Cu≤0.35%, V≤0.20%. No extrapolation outside this range.
Using the result
First assess DI, then combine it with the H value for the actual quenching conditions to estimate round-bar critical diameter. Even at the same DI, medium, bath temperature, relative motion and loading can change actual cooling.
What help do you need after calculating?
- Insufficient cooling with your current medium: discuss AR-UHS or a suitable AR-series product.
- Large Cr–Mo steel liners: discuss AR-SAG and internal temperature measurement.
- Conventional water-based quenching: explore AR-GP.
- High-chromium cast iron: visit AR-HCCI directly; this steel DI formula does not apply.
From preliminary calculation to workpiece-specific advice
Use the preliminary analysis or ask directly about quenchant or test equipment. If your process is established and you only need product supply, contact us without completing a full simulation.
Sharing calculations and documents is your choice.
Data classification
Three data types must remain separate
Every curve and conclusion on this site is identified by how the data was obtained.
Software-predicted curve
Calculated from a stated model and inputs. It is a prediction, not measured production data.
Measured internal workpiece cooling curves
Comes from internal points in the actual workpiece and is used to assess the real cooling process against post-quench hardness, microstructure and properties.
Unless explicitly identified and validated, one data type cannot be converted into or substituted for another.Read the technical method
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