Steel 4621 QT28-32
Hardness band
AISI/SAE 4621 · UNS G46210
QT28-32 = q&T 28–32 HRC
Direct-quench-and-temper option for small sections needing uniform medium-strength core without carburizing.
Values for the QT28-32 condition
Other 4621 tempers and conditions
4621 is listed in 7 conditions; see the grade overview at 4621.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Hot rolled | Lowest-cost mill condition for parts that will be heat treated anyway; scale and size tolerance are coarse. | 350 | 570 | 27 | 170 HB | 7.8 % IACS |
ANNDefault Annealed | Softest condition; the usual stock form for bar that will be machined then carburized. | 380 | 530 | 30 | 156 HB | — |
Hardenability-guaranteed (H-band) grade | Order this when Jominy end-quench hardenability limits must be certified for consistent case/core response in gear production. | 380 | 530 | 30 | 156 HB | 7.8 % IACS |
Normalized | Uniform fine grain and better impact toughness before carburizing or for as-supplied structural use. | 385 | 595 | 28 | 179 HB | — |
Cold drawn | Choose for tight size tolerance, straightness and better surface on screw-machine parts before carburizing. | 560 | 650 | 15 | 192 HB | — |
Carburized, quenched and tempered | The service condition for gears and pins: hard wear-resistant case with a strong, ductile Ni-Mo core. | 730 | 980 | 12 | 60 HRC | — |
QT28-32This page Q&T 28–32 HRC | Direct-quench-and-temper option for small sections needing uniform medium-strength core without carburizing. | 790 | 950 | 17 | 30 HRC | — |
What is 4621 QT28-32?
4621 QT28-32 is 4621 heat treated to QT28-32 — direct-quench-and-temper option for small sections needing uniform medium-strength core without carburizing. 4621 QT28-32 has a yield strength of 790 MPa (115 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 86% of steel grades. Elongation at break is 17% and the elastic modulus is 205 GPa (29.7 Msi). 4621 QT28-32 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). ANN is the default condition FabDigit quotes; QT28-32 is available on request or by drawing note.
Advantages
- High strength — 790 MPa (115 ksi), better than 86% of steel grades
4621 QT28-32 properties
Typical room-temperature values for 4621 QT28-32; 10 are specific to this condition. Other listed values are 4621 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
4621 QT28-32 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
4621 QT28-32 has a yield strength of 790 MPa (115 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 86% of steel grades. Elongation at break is 17% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4621 QT28-32 is rated for continuous service to 400°C (752 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
4621 QT28-32 conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 4621 QT28-32 takes about 34 MJ of energy and emits 2.4 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 30%.
Manufacturability6
4621 QT28-32's machinability is fair (42/100, worse than 73% of steel grades); weldability fair (45/100); formability good (60/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 4621 QT28-32
Is 4621 easy to machine?
Machines well in the annealed or cold-drawn state (~65 % of 1212); use sharp carbide or HSS, generous coolant, and finish-machine before carburizing since the case is grind-only.
Can 4621 be welded?
Weldable in the uncarburized state with low-hydrogen consumables, 150–250 °C preheat and post-weld stress relief; do not weld carburized surfaces.
Can 4621 be formed, bent or molded?
Good cold heading and bending in the annealed condition; hot forge 1100–1230 °C and normalize afterwards to restore grain size.
What surface finishes work on 4621?
Case-hardened parts are ground and shot-peened for fatigue strength; bare surfaces rust quickly, so oil, black-oxide, phosphate or zinc/nickel plating (with hydrogen bake) is standard.
4621 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| C | 0.18 – 0.23 | 0.21 |
| Mn | 0.7 – 0.9 | 0.8 |
| Si | 0.15 – 0.35 | 0.25 |
| Ni | 1.65 – 2 | 1.82 |
| Mo | 0.2 – 0.3 | 0.25 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Fe | balance | — |
4621 QT28-32 — frequently asked
What is 4621 QT28-32 used for?
4621 QT28-32 is typically used for gears, pins and carburized shafts. In short: higher-carbon 4620 variant; ni-Mo carburizing gear steel; tough core after case hardening.
What is the yield strength of 4621 QT28-32?
4621 QT28-32 has a typical yield strength of 790 MPa (115 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 86% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 4621 QT28-32 easy to machine?
Not especially — machinability is rated fair (42/100, worse than 73% of steel grades). Machines well in the annealed or cold-drawn state (~65 % of 1212); use sharp carbide or HSS, generous coolant, and finish-machine before carburizing since the case is grind-only.
Can 4621 QT28-32 be welded?
With care — weldability is rated fair (45/100). Weldable in the uncarburized state with low-hydrogen consumables, 150–250 °C preheat and post-weld stress relief; do not weld carburized surfaces.
What surface finishes work on 4621 QT28-32?
Case-hardened parts are ground and shot-peened for fatigue strength; bare surfaces rust quickly, so oil, black-oxide, phosphate or zinc/nickel plating (with hydrogen bake) is standard.
Can 4621 QT28-32 be formed, bent or molded?
Good cold heading and bending in the annealed condition; hot forge 1100–1230 °C and normalize afterwards to restore grain size.
What is the maximum service temperature of 4621 QT28-32?
4621 QT28-32 is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 4621-ANN and 4621 QT28-32?
ANN is the default condition — softest condition; the usual stock form for bar that will be machined then carburized. QT28-32: direct-quench-and-temper option for small sections needing uniform medium-strength core without carburizing. Yield strength is 380 MPa in ANN versus 790 MPa in QT28-32.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- SAE J1268 — Hardenability Bands for Carbon and Alloy H Steels — SAE International (2019)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought, General Requirements — ASTM (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating (Carburizing of 46xx steels) — ASM International (1991)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.