Quench & Temper
Through-hardening · Through-hardening
Quench and temper transforms hardenable steel to martensite and then tempers it to the required balance of strength and toughness.
Q&T 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 Q&T?
Quench and temper transforms hardenable steel to martensite and then tempers it to the required balance of strength and toughness. It is the standard through-hardening route for shafts, fasteners, gears, and structural steel parts.
How it works
Austenitizing dissolves carbon and converts the starting structure to austenite. Rapid oil, water, polymer, or gas cooling suppresses diffusional ferrite and pearlite formation so martensite forms through the section permitted by the steel hardenability. As-quenched martensite is hard and highly stressed; tempering precipitates transition carbides, reduces tetragonality, and restores toughness. Higher temper temperature generally lowers hardness and raises ductility. Section size, agitation, transfer time, and quenchant severity determine whether the center reaches the required cooling rate and whether the part cracks or distorts.
Why specify it
- Provides approximately 28–55 HRC across common engineering-steel temper conditions
- Develops roughly 900–1900 MPa tensile strength in common low-alloy steels
- Balances wear resistance with impact toughness through temper selection
Where it falls short
- Liquid quenching creates medium-to-high distortion risk
- Section size is limited by alloy hardenability
- Poor atmosphere control causes scale and decarburization
The Q&T 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 | 815–900 °C (1,499–1,652 °F) — Austenitize; 4140 is commonly treated near 845 °C. |
|---|---|
| Soak | 0.5–2 h — Section-dependent after equalization. |
| Cooling | Oil quench |
| Atmosphere | Endothermic gas / vacuum |
| Door to door | 4–10 h — One temper; some grades require two. |
Stages
- 1Austenitize at the grade-specific temperature
- 2Quench to below the martensite finish range
- 3Temper 2 h to the specified hardness
What Q&T does to the part
| Hardness | 28–55 HRC (270–550 HB) — Set by alloy and temper temperature. |
|---|---|
| Section affected | The whole section transforms. |
| Tensile strength | 900–1,900 MPa — Representative 4140/4340 range across temper conditions. |
| Toughness | Toughness rises as temper temperature rises; alloy-specific temper-embrittlement ranges must be avoided. |
| Distortion | Medium risk. Quench movement depends on geometry, section change, hardenability, and quenchant. |
| Surface after treatment | Protective atmosphere or vacuum controls scale and decarburization; oil residue is cleaned after quench. |
| Machining sequence | Rough machine before treatment and finish grind precision datums, bores, and bearing seats afterward. |
Specifications for Q&T
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 |
Heat Treatment of Low-Alloy Steel Parts, Minimum Tensile Strength 220 ksi (1517 MPa) and Higher | Governing | — | Active |
Heat Treatment, Martensitic Corrosion-Resistant Steel Parts | Governing | — | Active |
Test and related methods: ASTM E10 (Standard Test Method for Brinell Hardness of Metallic Materials), 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 683-2 (Heat-treatable steels, alloy steels and free-cutting steels — Part 2: Alloy steels for quenching and tempering), MIL-H-6875 (Heat Treatment of Steel Raw Materials).
Drawing call-out
HEAT TREAT AISI 4140 PER AMS 2759/1 TO 40–45 HRC; TEST PER ASTM E18 AT MID-LENGTH LOCATION SHOWNWhich alloys take Q&T?
Verdict per material family, with the grades that behave differently. Each family links to its datasheets in the material library. Typical grades: 1045, 4140, 4340, 300M, S7, O1.
| 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 hardenable steel can be quenched and tempered after alloy and density qualification.
| |
| With care | Martensitic stainless grades can be hardened and tempered under AMS 2759/5.
| |
| 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 Q&T
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 3–7 working days beyond machining.Furnace scheduling, controlled cooling, hardness testing, and certification extend beyond the soak time.
- Use generous fillets and avoid abrupt section changes greater than 2:1.Quench cooling and transformation strains concentrate at geometric transitions and promote cracking.
Q&T versus the alternatives
Treatments engineers weigh against Q&T, and when each wins.
| Treatment | Hardness | Toughness | Stability | Cost | Choose it when |
|---|---|---|---|---|---|
Q&T this page | 38 | 55 | 45 | $$ | — |
| 34 | 75 | 75 | $$$ | when bainitic toughness and lower distortion suit the steel and section | |
| 53 | 55 | 70 | $$$ | when quench-stress reduction is needed but tempered martensite remains the target | |
| 67 | 50 | 60 | $$ | when only a local wear surface needs hardening |
Cost, lead time and applications
Relative cost
Quench & Temper is a standard-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 | 3–7 working days |
|---|---|
| Furnace time | 4–10 h |
What Q&T is used for
- Power-transmission shafts
- High-strength fasteners
- Gears and pinions
- Tooling and impact components
Q&T — frequently asked
What temperature is used for Q&T?
The representative process window is 815–900 °C, but the exact setpoint follows the alloy and governing specification. The listed soak is 0.5–2 h after the load reaches temperature.
What hardness does Q&T produce?
The catalog result is 28–55 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 Q&T take?
The thermal cycle is typically 4–10 h door to door. Commercial lead time is normally 3–7 additional working days because loading, certification, and inspection are separate from furnace time.
Will Q&T 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 Q&T 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.