Steel 8720
AISI/SAE 8720 · UNS G87200
8720 is a nickel-chromium-molybdenum carburizing steel (UNS G87200) with slightly more molybdenum than 8620, which gives deeper hardenability in larger carburized cross-sections.
Reference datasheet — 8720 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
8720 tempers and conditions
8720 is supplied in 9 conditions, soft to hard. ANN is the default FabDigit quotes; the values on this page are for it.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize Annealed | Pick when the blank must be cold headed, extruded or deep formed before carburizing. | 340 | 500 | 34 | 143 HB | 8 % IACS |
Hot rolled | Cheapest mill condition for parts that will be normalized or carburized after machining. | 380 | 620 | 25 | 179 HB | 8 % IACS |
ANNDefault Annealed | Standard as-supplied bar condition for rough and finish machining before carburizing. | 385 | 540 | 31 | 149 HB | — |
Normalized | Use to homogenize forgings and refine grain for uniform response to carburizing. | 390 | 635 | 26 | 190 HB | — |
H-band hardenability grade | Order this when Jominy hardenability must be guaranteed for consistent case/core response in production heat treating. | 390 | 560 | 28 | 160 HB | 8 % IACS |
Cold drawn | Choose for tight tolerance, good surface bar where only light machining precedes carburizing. | 600 | 700 | 15 | 207 HB | — |
quenched and tempered core condition | Through-hardened low-carbon core condition for shafts and fasteners not needing a carburized case. | 800 | 960 | 17 | 30 HRC | — |
quenched and tempered, higher core strength | Use where a stronger core is needed under a carburized case or for heavier loaded shafts. | 950 | 1,120 | 15 | 35 HRC | — |
Carburized, quenched & tempered | The service condition: hard wear-resistant case over a tough core for gears, splines and races. | 980 | 1,240 | 12 | 60 HRC | — |
What is 8720?
8720 is a nickel-chromium-molybdenum carburizing steel (UNS G87200) with slightly more molybdenum than 8620, which gives deeper hardenability in larger carburized cross-sections. It is chosen for gears, shafts and bearing races that need a 58-62 HRC case over a tough core quenched and tempered to 28-32 or 33-38 HRC, and is stocked as hot-rolled, annealed, normalized, cold-drawn and spheroidize-annealed bar plus 8720H hardenability-controlled stock. Default properties are 385 MPa yield, 540 MPa tensile, 31% elongation and 149 HB (80 HRB). It has no corrosion resistance and must be welded before carburizing; 8620 remains cheaper for lighter sections. 8720 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F). 8720 has a yield strength of 385 MPa (55.8 ksi) and a tensile strength of 540 MPa (78.3 ksi) — weaker than 65% of steel grades. Elongation at break is 31% and the elastic modulus is 205 GPa (29.7 Msi).
What is 8720 used for?
- large gears
- shafts
- bearing races
Advantages
- Ductile — tolerates forming and impact — 31%, better than 94% of steel grades
- Easy to machine — 65/100, better than 93% of steel grades
- Forms and bends easily — 62/100, better than 78% of steel grades
8720 properties
Typical room-temperature values for 8720-ANN; bars are the position among steel grades.
Physical3
8720 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F).
Mechanical14
8720 has a yield strength of 385 MPa (55.8 ksi) and a tensile strength of 540 MPa (78.3 ksi) — weaker than 65% of steel grades. Elongation at break is 31% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
8720 is rated for continuous service to 350°C (662 °F). It conducts heat at 45 W/m·K (26 BTU/hr·ft·°F), better than 66% of steel grades. Thermal expansion is 11.6 µm/m·K (6.44 µin/in·°F).
Electrical3
8720 conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental2
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of 8720 takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 35%.
Manufacturability7
8720's machinability is good (65/100, better than 93% of steel grades); weldability good (65/100); formability good (62/100).
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. 8720 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 8720
Is 8720 easy to machine?
Machines well in the annealed/normalized state (~60–65 % of AISI 1212); use rigid setups and carbide tooling, and finish-grind gear teeth after carburizing since the 58–62 HRC case is not turnable.
Can 8720 be welded?
Weldable in the pre-carburized low-carbon condition with low-hydrogen consumables, 150–250 °C preheat and post-weld stress relief; do not weld after case hardening.
Can 8720 be formed, bent or molded?
Hot forge at 1100–1200 °C then normalize; cold heading and light bending are practical only in the annealed or spheroidize-annealed condition.
8720 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 |
|---|---|---|
| CSAE J404 / ASTM A29 | 0.18 – 0.23 | 0.2 |
| Mn | 0.7 – 0.9 | 0.8 |
| Si | 0.15 – 0.35 | 0.25 |
| Ni | 0.4 – 0.7 | 0.55 |
| Cr | 0.4 – 0.6 | 0.5 |
| Mohigher than 8620 (0.15–0.25) for deeper hardenability | 0.2 – 0.3 | 0.25 |
| P | ≤ 0.04 | |
| S | ≤ 0.04 | |
| Fe | balance |
What surface finishes work on 8720?
No anodizing (ferrous): protect with oil, black oxide, manganese phosphate or zinc/nickel plating; bake plated case-hardened parts to avoid hydrogen embrittlement, and shot-peen gear roots to raise fatigue life.
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 8720 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- G87200
How much does 8720 cost?
8720 is a budget-cost steel ($), cheaper than about 90% 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.
8720 — frequently asked
What is 8720 used for?
8720 is typically used for large gears, shafts and bearing races. In short: deeper hardenability than 8620; ni-Cr-Mo gear steel; 8720H hardenability option.
What is the yield strength of 8720?
8720 has a typical yield strength of 385 MPa (55.8 ksi) and a tensile strength of 540 MPa (78.3 ksi) — weaker than 65% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 8720 easy to machine?
Reasonably — machinability is rated good (65/100, better than 93% of steel grades). Machines well in the annealed/normalized state (~60–65 % of AISI 1212); use rigid setups and carbide tooling, and finish-grind gear teeth after carburizing since the 58–62 HRC case is not turnable.
Can 8720 be welded?
Yes — weldability is rated good (65/100). Weldable in the pre-carburized low-carbon condition with low-hydrogen consumables, 150–250 °C preheat and post-weld stress relief; do not weld after case hardening.
What surface finishes work on 8720?
No anodizing (ferrous): protect with oil, black oxide, manganese phosphate or zinc/nickel plating; bake plated case-hardened parts to avoid hydrogen embrittlement, and shot-peen gear roots to raise fatigue life.
Can 8720 be formed, bent or molded?
Hot forge at 1100–1200 °C then normalize; cold heading and light bending are practical only in the annealed or spheroidize-annealed condition.
What is the maximum service temperature of 8720?
8720 is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 8720-ANN and 8720-CD?
ANN is the default condition — standard as-supplied bar condition for rough and finish machining before carburizing. CD: choose for tight tolerance, good surface bar where only light machining precedes carburizing. Yield strength is 385 MPa in ANN versus 600 MPa in CD.
How much does 8720 cost?
8720 is a budget-cost steel ($), cheaper than about 90% 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)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- SAE J1268 — Hardenability of Carbon and Low-Alloy H Steels — SAE International (2018)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4A — Steel Heat Treating Fundamentals (carburizing) — ASM International (2013)
- ASM Handbook Vol.16 — Machining — ASM International (1989)
- (SMM / Mysteel / 1688 ) (2025)
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.