Steel SCr445-QT (Quenched and tempered)
Heat-treated state · default condition
JIS SCr445 · AISI/SAE 5145
Standard supply/heat-treat condition: ≥980 MPa tensile with usable toughness for shafts and gears.
Values for the QT condition
Other SCr445 tempers and conditions
SCr445 is listed in 10 conditions; see the grade overview at SCr445.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition — pick for heavy machining, cold forming or deep-hole drilling before hardening. | 400 | 700 | 22 | 197 HB | — |
Hot rolled | Cheapest mill condition for stock that will be re-heat-treated after machining. | 480 | 800 | 18 | 21 HRC | — |
Normalized | Uniform fine pearlitic structure for forgings before final machining or hardening. | 540 | 870 | 17 | 25 HRC | — |
Cold drawn | Bright, close-tolerance bar for shafts machined without further heat treatment. | 750 | 900 | 10 | 26 HRC | 8 % IACS |
high-temper condition | Toughness-biased temper (≈600 °C) for large shafts and impact-loaded parts. | 810 | 980 | 16 | 30 HRC | 8 % IACS |
QTDefaultThis page Quenched and tempered | Standard supply/heat-treat condition: ≥980 MPa tensile with usable toughness for shafts and gears. | 860 | 1,030 | 14 | 32 HRC | — |
Induction hardened | Choose for journals, splines and gear teeth needing 55+ HRC wear surface with a tough 30 HRC core. | 860 | 1,030 | 12 | 57 HRC | 8 % IACS |
medium temper | Balanced strength/toughness temper for gears, couplings and high-strength fasteners. | 960 | 1,120 | 14 | 34 HRC | 8 % IACS |
low temper, high strength | Maximum through-hardened strength for wear-loaded shafts and pins; reduced toughness, grind after heat treat. | 1,150 | 1,300 | 11 | 40 HRC | — |
As-quenched | Intermediate state only — must be tempered promptly; maximum hardness but brittle and crack-prone. | 1,600 | 2,000 | 2 | 58 HRC | 6 % IACS |
What is SCr445-QT?
SCr445-QT is SCr445 heat treated to QT — standard supply/heat-treat condition: ≥980 MPa tensile with usable toughness for shafts and gears. SCr445-QT has a yield strength of 860 MPa (125 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 89% of steel grades. Elongation at break is 14% and the elastic modulus is 207 GPa (30 Msi). SCr445-QT has a density of 7.83 g/cm³ (0.283 lb/in³), lighter than 80% of steel grades. It melts at 1,425°C (2,597 °F).
Advantages
- High strength — 860 MPa (125 ksi), better than 89% of steel grades
Limitations
- Limited formability — 20/100, worse than 80% of steel grades
- Low fracture toughness — 60 MPa·√m (54.6 ksi·√in), worse than 78% of steel grades
- Difficult to weld — 25/100, worse than 77% of steel grades
- Limited ductility — 14%, worse than 75% of steel grades
SCr445-QT properties
Typical room-temperature values for SCr445-QT; 12 are specific to this condition. Other listed values are SCr445 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SCr445-QT has a density of 7.83 g/cm³ (0.283 lb/in³), lighter than 80% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
SCr445-QT has a yield strength of 860 MPa (125 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 89% of steel grades. Elongation at break is 14% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
SCr445-QT is rated for continuous service to 350°C (662 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
SCr445-QT 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 SCr445-QT takes about 30 MJ of energy and emits 2.1 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability6
SCr445-QT's machinability is fair (42/100, worse than 73% of steel grades); weldability poor (25/100); formability poor (20/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SCr445-QT
Is SCr445 easy to machine?
Machine in the annealed or normalized state (≤229 HB) with carbide tooling; above 32 HRC expect reduced speeds and finish by grinding.
Can SCr445 be welded?
Poor weldability at 0.45 % C — preheat 250–350 °C, low-hydrogen consumables and immediate post-weld temper are mandatory to avoid HAZ cracking.
Can SCr445 be formed, bent or molded?
Hot forge 1100–1200 °C then normalize; cold forming is limited to mild straightening — bend only in the annealed condition with generous radii.
What surface finishes work on SCr445?
No natural corrosion resistance: use black oxide, phosphate + oil, zinc/Zn-Ni plating (bake against hydrogen embrittlement above 1000 MPa) or paint; grinds and polishes well after hardening.
SCr445 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 |
|---|---|---|
| CJIS G 4053 SCr445 | 0.43 – 0.48 | 0.45 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.6 – 0.9 | 0.75 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Cr | 0.9 – 1.2 | 1.05 |
| Niresidual | ≤ 0.25 | — |
| Curesidual | ≤ 0.3 | — |
| Fe | balance | — |
SCr445-QT — frequently asked
What is SCr445-QT used for?
SCr445-QT is typically used for shafts, gears, spring collars and high-strength bolts. In short: higher-strength SCr440 upgrade; through-hardening chromium steel; strength before weldability.
What is the yield strength of SCr445-QT?
SCr445-QT has a typical yield strength of 860 MPa (125 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 89% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is SCr445-QT easy to machine?
Not especially — machinability is rated fair (42/100, worse than 73% of steel grades). Machine in the annealed or normalized state (≤229 HB) with carbide tooling; above 32 HRC expect reduced speeds and finish by grinding.
Can SCr445-QT be welded?
Not readily — weldability is rated poor (25/100). Poor weldability at 0.45 % C — preheat 250–350 °C, low-hydrogen consumables and immediate post-weld temper are mandatory to avoid HAZ cracking.
What surface finishes work on SCr445-QT?
No natural corrosion resistance: use black oxide, phosphate + oil, zinc/Zn-Ni plating (bake against hydrogen embrittlement above 1000 MPa) or paint; grinds and polishes well after hardening.
Can SCr445-QT be formed, bent or molded?
Hot forge 1100–1200 °C then normalize; cold forming is limited to mild straightening — bend only in the annealed condition with generous radii.
What is the maximum service temperature of SCr445-QT?
SCr445-QT 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 SCr445-QT and SCr445-Q?
QT is the default condition — standard supply/heat-treat condition: ≥980 MPa tensile with usable toughness for shafts and gears. Q: intermediate state only — must be tempered promptly; maximum hardness but brittle and crack-prone. Yield strength is 860 MPa in QT versus 1,600 MPa in Q.
Sources
- JIS G 4053 — Low-alloyed steels for machine structural use — JSA (2016)
- GB/T 3077 — Alloy structural steels (45Cr) — SAC (2015)
- ASTM A29/A29M — Steel bars, carbon and alloy (5145/5147) — ASTM (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Machinery's Handbook (machinability ratings, heat treatment of Cr steels) — Industrial Press (2020)
- Mysteel / 1688 alloy round bar spot quotations (45Cr) — Mysteel (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.