Steel 8630 · heat-treated state
Steel 8630 Q&T
Properties of the Q&T condition, compared with the other 8630 tempers.
Oil quenched from ~860 °C and tempered ~540–595 °C to about 28–32 HRC — the standard structural/oilfield condition balancing strength and toughness.
What is 8630 Q&T?
8630 Q&T is 8630 heat treated to Q&T — oil quenched from ~860 °C and tempered ~540–595 °C to about 28–32 HRC — the standard structural/oilfield condition balancing strength and toughness. 8630 Q&T has a yield strength of 860 MPa (125 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 89% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi). 8630 Q&T has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). HR is the default condition FabDigit quotes; Q&T is available on request or by drawing note.
Advantages
- High strength — 860 MPa (125 ksi), better than 89% of steel grades
8630 Q&T properties
Typical room-temperature values for 8630 Q&T — 13 properties are specific to this condition; the rest are grade-level values shared by every 8630 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
8630 Q&T has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical13
8630 Q&T has a yield strength of 860 MPa (125 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 89% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
8630 Q&T is rated for continuous service to 400°C (752 °F). It conducts heat at 43 W/m·K (24.8 BTU/hr·ft·°F), better than 51% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
8630 Q&T conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 8630 Q&T takes about 30 MJ of energy and emits 2.2 kg of CO₂ — more than 55% of steel grades. Typical recycled content is 35%.
Manufacturability7
8630 Q&T's machinability is fair (50/100, worse than 53% of steel grades); weldability fair (40/100); formability fair (40/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 8630 tempers and conditions
8630 is also supplied in 7 other conditions. The full side-by-side table is on the 8630 overview.
- HRDefaultMill hot-rolled bar/plate as most commonly stocked; buy when parts will be heat treated after machining.415 MPa yield · 197 HB
- Q&T 40-45HRCTempered ~315–425 °C for high strength shafts, pins and fasteners where toughness demands are moderate.1,280 MPa yield · 43 HRC
- Q&TOil quenched from ~860 °C and tempered ~540–595 °C to about 28–32 HRC — the standard structural/oilfield condition balancing strength and toughness.860 MPa yield · 30 HRC
- CDCold-drawn bar for good size tolerance, straightness and improved machined finish without further heat treatment.655 MPa yield · 223 HB
- Q&T 22HRCHigh-temperature temper limiting hardness to 22 HRC max for H2S-containing (sour) subsea and wellhead components.585 MPa yield · 20 HRC
- NormalizedNormalized ~870 °C air cool: uniform fine grain and good toughness, typical pre-condition for forgings and weldments.430 MPa yield · 187 HB
- AnnealedFully/spheroidize annealed (~845 °C, furnace cool) for maximum softness before heavy machining or cold forming.372 MPa yield · 156 HB
Working with 8630 Q&T
Is 8630 easy to machine?
Machines best annealed or ~200 HB (about 65 % of AISI 1212); use rigid setups, carbide tooling and reduced speeds above 30 HRC.
Can 8630 be welded?
Weldable with low-hydrogen consumables but CE ≈0.75 demands 200–300 °C preheat, controlled interpass and PWHT/re-temper to avoid HAZ cracking.
Can 8630 be formed, bent or molded?
Hot forge 1100–1200 °C and normalize afterwards; cold forming only in the annealed condition with generous bend radii.
What surface finishes work on 8630?
No inherent corrosion resistance — protect by phosphating, zinc/Ni plating, thermal spray or paint; nitriding and induction hardening give good wear surfaces (avoid electroplating >32 HRC without bake-out).
8630 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 | 0.28 – 0.33 | 0.3 |
| 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 |
| Mo | 0.15 – 0.25 | 0.2 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Fe | balance | — |
8630 Q&T — frequently asked
What is 8630 Q&T used for?
8630 Q&T is typically used for shafts, gears and fittings. In short: workhorse Cr-Mo bar.
What is the yield strength of 8630 Q&T?
8630 Q&T has a typical yield strength of 860 MPa (125 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 89% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 8630 Q&T easy to machine?
Reasonably — machinability is rated fair (50/100, worse than 53% of steel grades). Machines best annealed or ~200 HB (about 65 % of AISI 1212); use rigid setups, carbide tooling and reduced speeds above 30 HRC.
Can 8630 Q&T be welded?
With care — weldability is rated fair (40/100). Weldable with low-hydrogen consumables but CE ≈0.75 demands 200–300 °C preheat, controlled interpass and PWHT/re-temper to avoid HAZ cracking.
What surface finishes work on 8630 Q&T?
No inherent corrosion resistance — protect by phosphating, zinc/Ni plating, thermal spray or paint; nitriding and induction hardening give good wear surfaces (avoid electroplating >32 HRC without bake-out).
Can 8630 Q&T be formed, bent or molded?
Hot forge 1100–1200 °C and normalize afterwards; cold forming only in the annealed condition with generous bend radii.
What is the maximum service temperature of 8630 Q&T?
8630 Q&T 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 8630-HR and 8630-CD?
HR is the default condition — mill hot-rolled bar/plate as most commonly stocked; buy when parts will be heat treated after machining. CD: cold-drawn bar for good size tolerance, straightness and improved machined finish without further heat treatment. Yield strength is 415 MPa in HR versus 655 MPa in CD.
Can FabDigit make parts in 8630 Q&T?
Yes — 8630 Q&T is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- ASTM A322 — Alloy Steel Bars, Standard Grades — ASTM (2019)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- NACE MR0175 / ISO 15156 — Materials for H2S-containing environments — NACE/ISO (2015)
- Machinery's Handbook, 31st ed. — Industrial Press (2020)
- Mysteel / SMM (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.