Steel 4621
AISI/SAE 4621 · UNS G46210
4621 is a nickel-molybdenum case-hardening steel (UNS G46210) from the SAE-AISI alloy steel series, similar to 4620 but with slightly higher carbon that gives marginally higher core strength after carburizing.
Reference datasheet — 4621 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the ANN condition
4621 tempers and conditions
4621 is supplied in 7 conditions, soft to hard. ANN is the default FabDigit quotes; the values on this page are for it.
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 | — |
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?
4621 is a nickel-molybdenum case-hardening steel (UNS G46210) from the SAE-AISI alloy steel series, similar to 4620 but with slightly higher carbon that gives marginally higher core strength after carburizing. It is specified for gears, pins and carburized shafts and is stocked as hot-rolled, annealed, normalized, cold-drawn and 4621H hardenability-controlled bar. Annealed material runs about 380 MPa yield, 530 MPa tensile, 30 % elongation and 156 HB. It has no inherent corrosion resistance and the hardened case can only be finished by grinding, so machining must be completed before carburizing; 4620 and 8620 are the nearest alternatives. 4621 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). 4621 has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 530 MPa (76.9 ksi) — weaker than 68% of steel grades. Elongation at break is 30% and the elastic modulus is 205 GPa (29.7 Msi).
What is 4621 used for?
- gears
- pins
- carburized shafts
Advantages
- Ductile — tolerates forming and impact — 30%, better than 93% of steel grades
4621 properties
Typical room-temperature values for 4621-ANN; bars are the position among steel grades.
Physical3
4621 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 has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 530 MPa (76.9 ksi) — weaker than 68% of steel grades. Elongation at break is 30% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4621 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 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 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's machinability is good (58/100, better than 75% of steel grades); weldability fair (45/100); formability good (60/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. 4621 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 4621
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.
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 |
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.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel 4621 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- G46210
How much does 4621 cost?
4621 is a standard-cost steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
4621 — frequently asked
What is 4621 used for?
4621 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?
4621 has a typical yield strength of 380 MPa (55.1 ksi) and a tensile strength of 530 MPa (76.9 ksi) — weaker than 68% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 4621 easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% 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 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?
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 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?
4621 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.
How much does 4621 cost?
4621 is a standard-cost steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.