Steel 8720-HR (Hot rolled)
Supply condition
AISI/SAE 8720 · UNS G87200
Cheapest mill condition for parts that will be normalized or carburized after machining.
Values for the HR condition
Other 8720 tempers and conditions
8720 is listed in 9 conditions; see the grade overview at 8720.
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 |
HRThis page 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-HR?
8720-HR is 8720 supplied in the HR condition — cheapest mill condition for parts that will be normalized or carburized after machining. 8720-HR has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 68% of steel grades. Elongation at break is 25% and the elastic modulus is 205 GPa (29.7 Msi). 8720-HR 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). ANN is the default condition FabDigit quotes; HR is available on request or by drawing note.
Advantages
- Ductile — tolerates forming and impact — 25%, better than 77% of steel grades
8720-HR properties
Typical room-temperature values for 8720-HR; 21 are specific to this condition. Other listed values are 8720 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
8720-HR 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-HR has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 68% of steel grades. Elongation at break is 25% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
8720-HR 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-HR conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental2
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 8720-HR 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-HR's machinability is good (60/100, better than 83% of steel grades); weldability good (65/100); formability fair (48/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 8720-HR
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.
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.
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 | — |
8720-HR — frequently asked
What is 8720-HR used for?
8720-HR 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-HR?
8720-HR has a typical yield strength of 380 MPa (55.1 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 68% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 8720-HR easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% 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-HR 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-HR?
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-HR 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-HR?
8720-HR 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.