Martensite Start Temperature Calculator

Inputs

View results
Carbon is the dominant term — every 0.1% C drops Ms about 42°C.
wt%
Weight percent manganese.
wt%
Weight percent nickel.
wt%
Weight percent chromium.
wt%
Weight percent molybdenum.
wt%
Temperature the part is quenched to — room temperature (20°C) for a normal quench, lower for cryogenic/sub-zero treatment.
°C
Koistinen-Marburger athermal rate constant. 0.011 /°C is the widely-used value (strictly low-carbon, applied broadly as an engineering estimate).
/°C

Results

Default result
Edit inputs
Martensite start (Ms)(Ms)
330.2°C
Pass

Andrews 1965 — the temperature where martensite first forms on quenching.

Also computed

Martensite at quench tempPass96.7%

Koistinen-Marburger fraction transformed by the time the part reaches Tq.

Retained austenitePass3.3%

3.3% austenite remains at this quench temperature.

The balance still austenite at Tq — soft, unstable, often the reason for a temper or cryo step.

Method notes 4 notes
  • Ms by the Andrews (1965) linear equation: Ms(°C) = 539 − 423·C − 30.4·Mn − 17.7·Ni − 12.1·Cr − 7.5·Mo, composition in weight percent. It is calibrated for low-alloy steels (roughly ≤0.6% C); Co, Si, W, V and the high-alloy/stainless range fall outside this form.
  • Retained austenite from Koistinen-Marburger: fraction transformed = 1 − exp(−α·(Ms − Tq)), α = 0.011 /°C. Quenching deeper (lower Tq, including sub-zero/cryo) converts more austenite — that is what a cryo step buys.
  • These are screening estimates from composition alone — they do not capture cooling rate, austenitizing temperature, grain size, segregation or prior microstructure. A dilatometer or hardenability test is the measured answer.
  • Pairs with the hardenability and case-depth side of heat treat: see the carburizing case depth and Larson-Miller tempering calculators.

Powered by MachineCalcs ↗