HeatTreat: Steel Calculator

HeatTreat computes the numbers you need to heat treat steel, and shows you where every one of them came from. Pick a grade or enter your own composition, and get critical temperatures, retained austenite, tempering equivalence and carbon equivalents, each with the equation that produced it, the paper it was published in, and a plain statement of where it stops being reliable.

Built for knife makers and blacksmiths first, then heat treat shops, students and engineers.

Every number shows its work

The equation, written out
The full citation: author, journal, year, pages
A check against the range the correlation was actually fitted on
A refusal when your chemistry sits outside what the correlation can honestly cover
That last one is the point. Ac3 is withheld for hypereutectoid steels rather than guessed. Tool steel and stainless chemistry is refused by the low-alloy correlations rather than extrapolated into nonsense. A withheld number is honest. A silently wrong one is not.

32 steels, each with its basis stated Carbon, alloy, tool and martensitic stainless grades, searchable across AISI, EN/DIN, JIS and old British designations. Every record says whether its chemistry is a standard range or producer-typical values, and lists its sources. Included: 1018, 1045, 1060, 1075, 1080, 1084, 1095, 15N20, 26C3, 4130, 4140, 4340, 5160, 6150, 8620, 9260, 9310, 52100, 80CrV2, 300M, W1, O1, A2, D2, S7, H13, M2, 420, 440C, AEB-L, 154CM and CPM MagnaCut.

Each grade page carries chemistry, cross-references with equivalence quality marks, typical published practice (austenitizing band drawn on the glow scale, quench medium, temper range, expected hardness), and a one-tap jump into the calculator.

What it calculates

Ac1 and Ac3, the lower and upper critical temperatures (Andrews 1965)
Ms, martensite start, with Steven and Haynes 1956 and Payson and Savage 1944 shown next to Andrews as a visible spread, because three published fits disagree and pretending otherwise would be dishonest
Bs, bainite start (Steven and Haynes 1956)
Retained austenite after quenching (Koistinen and Marburger 1959), with room, freezer, dry ice and liquid nitrogen quench-finish presets
Tempering equivalence (Hollomon and Jaffe 1945): two hours at 200 C is about eighteen minutes at 220 C, with the embrittlement-window caveat shown in the working
CE(IIW), Pcm and CET carbon equivalents, with weldability context
Reference, always to hand

Forge glow colors, from black heat to white, with the honest caveat that eye-judged color shifts with ambient light
Temper oxide colors
Grossmann quench severity for common media
Celsius or Fahrenheit throughout
The eight papers every number in the app comes from, cited in full
Private by design

No account, no sign-up
No ads, no tracking, no analytics, no data collection
No internet permission at all. The app cannot make a network call, even by accident.
Works on the shop floor, at the forge, or in a basement lab with no signal
Please note: HeatTreat gives engineering estimates from published empirical correlations, not specifications. Correlations carry scatter, and your steel, your furnace and your quench are not the ones the equations were fitted on. Verify against the applicable standard, your supplier's data, and your own test coupons before committing work.