Steel 8645 Annealed
Temper · default condition
AISI/SAE 8645 · UNS G86450
Softest condition for machining, deep drilling or cold forming before final quench and temper.
Values for the Annealed condition
Other 8645 tempers and conditions
8645 is listed in 11 conditions; see the grade overview at 8645.
Compare all 11 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefaultThis page full anneal ~815 °C, slow cool | Softest condition for machining, deep drilling or cold forming before final quench and temper. | 425 | 715 | 20 | 197 HB | — |
Hot rolled | Lowest-cost mill condition for parts that will be fully heat treated after rough machining. | 500 | 830 | 17 | 22 HRC | 7.8 % IACS |
Cold drawn | Cold-drawn bar with tight size tolerance, bright finish and raised yield strength; best chip control for screw-machine work. | 680 | 800 | 12 | 229 HB | — |
Normalized | Uniform fine-grain structure and higher strength than annealed; used as a pre-machining or as-supplied condition for moderately loaded parts. | 690 | 1,090 | 18 | 33 HRC | — |
Q&T to 28–32 HRC | Common stock hardness band for shafting and gear blanks that must still be machinable. | 830 | 965 | 20 | 30 HRC | — |
Q&T 650 °C | Toughest quenched-and-tempered condition; choose for impact-loaded or notch-sensitive parts. | 860 | 1,000 | 21 | 31 HRC | — |
Q&T to 34–38 HRC | Higher hardness band where wear and load capacity outrank machining ease. | 1,040 | 1,170 | 17 | 36 HRC | — |
Q&T 540 °C | Balanced strength/toughness workhorse temper for machinery shafting and connecting rods. | 1,160 | 1,275 | 17 | 39 HRC | — |
Q&T 425 °C | High strength with usable ductility for heavily loaded shafts, gears and fasteners. | 1,380 | 1,550 | 13 | 45 HRC | — |
Q&T 315 °C | Very high strength; avoid this temper range if impact toughness matters (tempered-martensite embrittlement). | 1,515 | 1,795 | 11 | 51 HRC | — |
Q&T 205 °C | Maximum hardness and strength for wear parts; very low ductility and notch toughness. | 1,720 | 2,000 | 10 | 55 HRC | — |
What is 8645 Annealed?
8645 Annealed is 8645 in the Annealed temper — softest condition for machining, deep drilling or cold forming before final quench and temper. 8645 Annealed has a yield strength of 425 MPa (61.6 ksi) and a tensile strength of 715 MPa (104 ksi) — weaker than 52% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi). 8645 Annealed 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).
8645 Annealed properties
Typical room-temperature values for 8645 Annealed; 14 are specific to this condition. Other listed values are 8645 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
8645 Annealed 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
8645 Annealed has a yield strength of 425 MPa (61.6 ksi) and a tensile strength of 715 MPa (104 ksi) — weaker than 52% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
8645 Annealed is rated for continuous service to 400°C (752 °F). It conducts heat at 45 W/m·K (26 BTU/hr·ft·°F), better than 66% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
8645 Annealed 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 8645 Annealed 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
8645 Annealed's machinability is good (55/100, better than 62% of steel grades); weldability poor (30/100); formability fair (35/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 8645 Annealed
Is 8645 easy to machine?
Machine in the annealed or ≤32 HRC condition with rigid setups and coated carbide; above 40 HRC switch to CBN/ceramic or grinding.
Can 8645 be welded?
Poor weldability at 0.45 %C — preheat 250–350 °C, low-hydrogen consumables, and temper/stress relieve immediately after welding.
Can 8645 be formed, bent or molded?
Cold forming limited to mild bending in the annealed state; hot forge 1100–1200 °C and cool slowly to avoid quench cracks.
What surface finishes work on 8645?
Not anodizable; protect with zinc/manganese phosphate, black oxide, electroless nickel or Cr plating — bake plated parts >40 HRC to relieve hydrogen.
8645 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 heat analysis | 0.43 – 0.48 | 0.46 |
| Mn | 0.75 – 1 | 0.88 |
| 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 | — |
8645 Annealed — frequently asked
What is 8645 Annealed used for?
8645 Annealed is typically used for heavy-duty shafts, high-strength fasteners, gears and structural machine components. In short: highest-strength 86xx bar; poor weldability at 0.45 % C; quench-and-temper only.
What is the yield strength of 8645 Annealed?
8645 Annealed has a typical yield strength of 425 MPa (61.6 ksi) and a tensile strength of 715 MPa (104 ksi) — weaker than 52% of steel grades. Strength varies by condition: see the 11 listed tempers.
Is 8645 Annealed easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machine in the annealed or ≤32 HRC condition with rigid setups and coated carbide; above 40 HRC switch to CBN/ceramic or grinding.
Can 8645 Annealed be welded?
Not readily — weldability is rated poor (30/100). Poor weldability at 0.45 %C — preheat 250–350 °C, low-hydrogen consumables, and temper/stress relieve immediately after welding.
What surface finishes work on 8645 Annealed?
Not anodizable; protect with zinc/manganese phosphate, black oxide, electroless nickel or Cr plating — bake plated parts >40 HRC to relieve hydrogen.
Can 8645 Annealed be formed, bent or molded?
Cold forming limited to mild bending in the annealed state; hot forge 1100–1200 °C and cool slowly to avoid quench cracks.
What is the maximum service temperature of 8645 Annealed?
8645 Annealed 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 8645 Annealed and 8645-QT205?
Annealed is the default condition — softest condition for machining, deep drilling or cold forming before final quench and temper. QT205: maximum hardness and strength for wear parts; very low ductility and notch toughness. Yield strength is 425 MPa in Annealed versus 1,720 MPa in QT205.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating — ASM International (1991)
- Low-alloy steel property tables (8600-series Q&T data) — ASM/MMPDS-derived compilations (2022)
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.