How accurate are these calculations?

The calculations are based on peer-reviewed empirical equations and established engineering standards (ASME, EN, ISO, ASTM). Accuracy depends on: (1) accuracy of input data (steel composition from mill certificate, not nominal); (2) applicability of the equation to the specific alloy (most are calibrated for carbon and low-alloy steels); (3) whether equilibrium conditions apply. For design-critical applications, always verify against material certificates and applicable codes.

Are these calculators suitable for design use?

These calculators are suitable for preliminary design, engineering checks, and educational purposes. For final design and qualification of safety-critical pressure equipment, structural connections, or weld procedures, calculations must be performed by a qualified engineer using the exact applicable code (ASME VIII, EN 13480, AWS D1.1, etc.) and verified by approved calculation methods. The calculators do not replace code compliance.

What units does the calculator use?

All calculators use SI units (°C, MPa, mm, kJ/mm, g/cm³) as primary output, with imperial conversions (°F, ksi, inches, J/in) provided where common in industry practice (particularly for ASME and AWS codes used in North America). Input and output units are clearly labelled in each calculator field.

Jominy Hardenability Calculator — Steel

The Jominy end-quench test (ISO 642 / ASTM A255) measures steel hardenability — the ability to harden throughout a section when quenched. A standard bar is austenitised, end-quenched with water, and Vickers or Rockwell hardness is measured at 1.5mm intervals from the quenched end. This calculator predicts Jominy hardness at each position from steel composition using the Grossmann hardenability method and converts Jominy position to equivalent cooling rate and section diameter.

Jominy Hardenability and Section Size Calculator

%C — Carbon

%Mn — Manganese

%Si — Silicon

%Cr — Chromium

%Mo — Molybdenum

%Ni — Nickel

%V — Vanadium

ASTM grain size (prior austenite)

Ideal critical diameter D_I (mm)—

As-quenched hardness at J1.5 (HRC, surface)—

Hardness at J5 (3mm from end)—

Hardness at J10 (typical bar surface — oil quench)—

Hardness at J15 (surface of 25mm bar, water)—

Hardness at J25 (typical large section core)—

Bar size achieving HRC 50 through-section (oil quench)—

Method: Grossmann D_I approach with multiplying factors for each element.
D_I (mm) = D_I_C × f_Mn × f_Si × f_Cr × f_Mo × f_Ni × f_V × f_gs
Jominy hardness profile estimated from D_I using SAE J406 correlation.
Maximum as-quenched hardness = 20 + 60×%C (Koistinen-Marburger approximation)

Figure: Schematic diagram for Jominy Hardenability Calculator — Steel Composition to … — key process, structure, and property relationships. © metallurgyzone.com/

Jominy Position to Cooling Rate and Section Size Reference

Jominy distance J (mm)	Cooling rate at 700°C (°C/s)	Approx. bar surface — oil quench	Approx. bar centre — water quench
J 1.5 (1.5mm)	315	Surface of any size (water or oil)	Surface of 6mm bar (water)
J 5 (5mm)	56	Surface of 25mm bar — oil	Centre of 12mm bar — oil
J 10 (10mm)	14	Surface of 50mm bar — oil	Centre of 25mm bar — oil
J 15 (15mm)	5.6	Surface of 75mm bar — oil	Centre of 50mm bar — oil
J 25 (25mm)	2.2	Surface of 125mm bar — oil	Centre of 100mm bar — oil
J 40 (40mm)	0.7	Core of 150mm bar — oil	Core of 250mm bar — water

Common Steel Hardenability Grades

Steel Grade	D_I (mm) typical	J10 Hardness (HRC)	Max through-hardened bar (oil)
1040 (0.40C, 0.75Mn)	~25 mm	~38	~25 mm
4140 (Cr-Mo alloy)	~75–100 mm	~50	~75 mm
4340 (Ni-Cr-Mo alloy)	~150–200 mm	~55	~150 mm
8620 (Ni-Cr-Mo, low C)	~60–80 mm	~35	Deep hardenability; case hardening grade
H13 (5Cr-1.5Mo-1V hot work)	>200 mm	~52	Air-hardening — very deep hardenability