Martemper
Through-hardening · Through-hardening
Martempering is an interrupted quench that equalizes austenitized steel just above its martensite-start temperature before cooling through martensite formation.
Reference page — Martemper is not in the instant-quote configurator. Upload the part, name the treatment in the notes with the call-out below, and an engineer quotes it with the part.
Martemper at a glance
Four scores, each 0–100 against every heat treatment in this catalog. Hardness is derived from the HRC target (20 HRC = 0, 70 HRC = 100) — treatments without a hardness target (anneals, stress relief, HIP, cryo) are not rated. Toughness, dimensional stability and cost are FabDigit's engineering assessment.
What is Martemper?
Martempering is an interrupted quench that equalizes austenitized steel just above its martensite-start temperature before cooling through martensite formation. A subsequent temper develops the final hardness and toughness with reduced cracking and distortion.
How it works
After austenitizing, the part is quenched into hot oil or molten salt held above the grade's martensite-start temperature. The bath cools the surface rapidly past the pearlite nose while the hold allows the core and surface temperatures to approach one another without intentionally forming bainite. The part is then air cooled through the martensitic transformation more uniformly, reducing differential transformation strain. Tempering follows immediately to relieve martensitic stress and set hardness. The hold must end before bainite begins, making time-temperature-transformation data and section size essential.
Why specify it
- Reduces quench cracking and movement compared with a direct cold quench
- Retains a tempered-martensite property target
- Useful for tools and gears with asymmetric sections
Where it falls short
- Requires precise bath temperature and transfer control
- Section must have enough hardenability to bypass pearlite
- Still requires tempering after martensite forms
The Martemper cycle
Typical furnace parameters from the governing specifications and shop practice; the heat treater sets the exact recipe from the alloy, section size and required result.
| Temperature | 790–900 °C (1,454–1,652 °F) — Austenitizing range; interrupted bath is commonly 150–300 °C and above Ms. |
|---|---|
| Soak | 0.1–1 h — Bath equalization without allowing bainite formation. |
| Cooling | Interrupted quench |
| Atmosphere | Salt bath |
| Door to door | 4–9 h — Includes interrupted quench and one temper. |
Stages
- 1Austenitize at the grade-specific temperature
- 2Quench to a 150–300 °C bath above Ms and equalize
- 3Air cool through Ms, then temper to target hardness
What Martemper does to the part
| Hardness | 35–62 HRC — Final hardness is set by alloy and tempering, not by the interrupted quench alone. |
|---|---|
| Section affected | The whole section transforms. |
| Toughness | Final toughness follows the temper condition; lower quench stress reduces cracking but does not make untempered martensite tough. |
| Distortion | Medium risk. Lower than a direct cold quench when equalization is effective, but geometry and support remain important. |
| Surface after treatment | Salt or hot-oil residue requires cleaning; controlled austenitizing atmosphere limits decarburization. |
| Machining sequence | Rough machine before treatment and finish grind precision surfaces after tempering. |
Specifications for Martemper
The documents a drawing cites to define this treatment. Each links to a page explaining the standard, its classes and the tests it invokes.
| Standard | Role | Classes used | Status |
|---|---|---|---|
Heat Treatment of Steel Parts, General Requirements | Governing | — | Active |
Heat Treatment of Carbon and Low-Alloy Steel Parts, Minimum Tensile Strength Below 220 ksi (1517 MPa) | Governing | — | Active |
Automated Gaseous Nitriding Controlled by Nitriding Potential | Governing | — | Active |
Heat Treatment of Low-Alloy Steel Parts, Minimum Tensile Strength 220 ksi (1517 MPa) and Higher | Governing | — | Active |
Test and related methods: ASTM E18 (Standard Test Methods for Rockwell Hardness of Metallic Materials), ASTM A1033 (Standard Practice for Quantitative Measurement and Reporting of Hypoeutectoid Carbon and Low-Alloy Steel Phase Transformations), ISO 683-1 (Heat-treatable steels, alloy steels and free-cutting steels — Part 1: Non-alloy steels for quenching and tempering), ISO 683-3 (Heat-treatable steels, alloy steels and free-cutting steels — Part 3: Case-hardening steels).
Drawing call-out
MARTEMPER AISI 52100 PER AMS 2759/10 TO 58–62 HRC; TEMPER IMMEDIATELY; TEST PER ASTM E18 ON RACEWAYWhich alloys take Martemper?
Verdict per material family, with the grades that behave differently. Each family links to its datasheets in the material library. Typical grades: 4140, 4340, 52100, O1, A2, D2.
| Material family | Verdict | Notes |
|---|---|---|
| Yes | The cycle is established for carbon, alloy, and tool steels within grade-specific temperature limits.
| |
| With care | Sintered steel can be treated after density and residual porosity are qualified.
| |
| With care | Printed steel may use the cycle after density, chemistry, and build-orientation effects are qualified.
| |
| With care | Selected martensitic stainless grades can use interrupted quenching under a qualified grade-specific procedure. | |
| No | Aluminum does not use this ferrous transformation cycle. | |
| No | Brass requires lower-temperature stress relief or recrystallization annealing. | |
| No | Bronze requires composition-specific annealing or precipitation treatment. | |
| No | Cobalt-chrome requires alloy-specific solution or aging practice. | |
| No | Copper alloys require alloy-specific annealing or precipitation-hardening cycles. | |
| No | Magnesium requires tightly controlled alloy-specific cycles. | |
| No | Nickel alloys require alloy-specific solution, anneal, or age cycles. | |
| No | Precious metals require alloy-specific annealing or age-hardening practice. | |
| No | Refractory metals require material-specific vacuum annealing practice. | |
| No | Titanium requires alloy-specific annealing or solution-and-age cycles. | |
| No | Tungsten heavy alloys require supplier-specific sintering and stress-relief practice. | |
| No | Zinc alloys melt or lose properties at temperatures used by this process. |
Design rules for Martemper
What to decide on the drawing before the part goes to the heat treater.
- Identify the alloy designation and incoming condition on the purchase order.A temperature that is correct for one grade can overtemper, sensitize, or fail to transform another grade.
- Place hardness test locations at least 3 mm from an edge where geometry permits.Edge decarburization, local cooling, and indentation spacing can bias the reported result.
- Leave 0.2–0.5 mm finish stock on critical ground surfaces when a quench or scale-producing atmosphere is used.Final grinding removes oxide, decarburization, and dimensional movement after the thermal cycle.
- Allow 4–8 working days beyond machining.Furnace scheduling, controlled cooling, hardness testing, and certification extend beyond the soak time.
- Set the bath above the measured or published Ms for the ordered heat.Cooling below Ms before equalization starts martensite at the surface and defeats the stress-reduction mechanism.
Martemper versus the alternatives
Treatments engineers weigh against Martemper, and when each wins.
| Treatment | Hardness | Toughness | Stability | Cost | Choose it when |
|---|---|---|---|---|---|
Martemper this page | 53 | 55 | 70 | $$$ | — |
| 38 | 55 | 45 | $$ | when conventional quenching meets distortion and cracking limits at lower cost | |
| 34 | 75 | 75 | $$$ | when bainite and greater isothermal transformation toughness are desired |
Cost, lead time and applications
Relative cost
Martemper is a premium-cost treatment ($$$) relative to the other heat treatments in this catalog.
Heat treatment is priced per lot with a furnace minimum. The exact figure appears on the instant quote once the part is uploaded.
Lead time
| Added lead time | 4–8 working days |
|---|---|
| Furnace time | 4–9 h |
What Martemper is used for
- Bearing rings
- Precision gears
- Tool-steel dies
- High-strength shafts with section changes
Martemper — frequently asked
What temperature is used for Martemper?
The representative process window is 790–900 °C, but the exact setpoint follows the alloy and governing specification. The listed soak is 0.1–1 h after the load reaches temperature.
What hardness does Martemper produce?
The catalog result is 35–62 HRC. Hardness must be verified on the part or a qualified witness coupon using the test method called out on the drawing.
How long does Martemper take?
The thermal cycle is typically 4–9 h door to door. Commercial lead time is normally 4–8 additional working days because loading, certification, and inspection are separate from furnace time.
Will Martemper distort the part?
The catalog rates distortion risk as medium. Reserve machining stock and verify critical datums after treatment when tolerances are tighter than 0.05 mm.
How should Martemper be specified on a drawing?
State the governing process specification, alloy condition, required result, and inspection location. Report hardness to ASTM E18 or ASTM E10 as applicable, and do not substitute a furnace recipe for an acceptance requirement.