Steel 5145-QT205
Heat-treated state
AISI/SAE 5145 · UNS G51450
QT205 = oQ&T 205 °C
Maximum hardness and wear resistance for pins, wear plates and tooling where toughness is secondary.
Values for the QT205 condition
Other 5145 tempers and conditions
5145 is listed in 14 conditions; see the grade overview at 5145.
Compare all 14 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Choose for maximum machinability or cold heading/upsetting of this higher-carbon Cr grade. | 320 | 585 | 28 | 170 HB | 8 % IACS |
ADefault Solution annealed | Standard stock condition: softest, most machinable state before quench-and-temper. | 340 | 620 | 25 | 180 HB | — |
Hot rolled | Cheapest mill condition for parts that will be fully heat treated after rough machining. | 440 | 730 | 18 | 212 HB | — |
Normalized | Uniform fine pearlitic structure with medium strength; used as a pre-machining or as-supplied condition for lightly loaded parts. | 500 | 830 | 20 | 22 HRC | — |
Cold drawn | Pick for close-tolerance bright bar with raised yield strength when no further heat treatment is planned. | 660 | 760 | 12 | 225 HB | — |
quenched and tempered to hardness band | Common commercial purchase band for shafts and machined components needing good toughness and easy finishing. | 840 | 960 | 18 | 30 HRC | — |
OQ&T 650 °C | Toughest quench-and-temper condition; use where shock loading or later machining dominates. | 860 | 965 | 19 | 30 HRC | — |
Induction hardened | Use when a hard wear surface (55–60 HRC) is needed over a tough Q&T core, e.g. journals and gear teeth. | 870 | 1,000 | 14 | 57 HRC | 7.4 % IACS |
quenched and tempered to hardness band | Higher-strength commercial band for gears, cams and wear-loaded shafts still machinable with carbide tooling. | 1,030 | 1,140 | 15 | 36 HRC | — |
OQ&T 540 °C | Good general-purpose temper: high yield with usable impact toughness for machine components. | 1,050 | 1,140 | 16 | 36 HRC | — |
quenched and tempered to hardness band | Specify when wear resistance matters more than impact toughness; grind rather than mill to finish. | 1,260 | 1,390 | 13 | 42 HRC | — |
OQ&T 425 °C | Balanced high strength and wear resistance for gears, spindles and heavy-duty shafts. | 1,275 | 1,400 | 13 | 42 HRC | — |
OQ&T 315 °C | Very high strength with slightly better ductility than the 205 °C temper. | 1,550 | 1,720 | 11 | 48 HRC | — |
QT205This page OQ&T 205 °C | Maximum hardness and wear resistance for pins, wear plates and tooling where toughness is secondary. | 1,660 | 1,930 | 9 | 52 HRC | — |
What is 5145-QT205?
5145-QT205 is 5145 heat treated to QT205 — maximum hardness and wear resistance for pins, wear plates and tooling where toughness is secondary. 5145-QT205 has a yield strength of 1,660 MPa (241 ksi) and a tensile strength of 1,930 MPa (280 ksi) — stronger than 99% of steel grades. Elongation at break is 9% and the elastic modulus is 205 GPa (29.7 Msi). 5145-QT205 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). A is the default condition FabDigit quotes; QT205 is available on request or by drawing note.
Advantages
- High strength — 1,660 MPa (241 ksi), better than 99% of steel grades
Limitations
- Limited service temperature — 160°C (320 °F), worse than 99% of steel grades
- Difficult to machine — 22/100, worse than 95% of steel grades
- Limited ductility — 9%, worse than 93% of steel grades
- Low fracture toughness — 40 MPa·√m (36.4 ksi·√in), worse than 92% of steel grades
- Difficult to weld — 15/100, worse than 91% of steel grades
5145-QT205 properties
Typical room-temperature values for 5145-QT205; 16 are specific to this condition. Other listed values are 5145 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
5145-QT205 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
5145-QT205 has a yield strength of 1,660 MPa (241 ksi) and a tensile strength of 1,930 MPa (280 ksi) — stronger than 99% of steel grades. Elongation at break is 9% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
5145-QT205 is rated for continuous service to 160°C (320 °F). It conducts heat at 46 W/m·K (26.6 BTU/hr·ft·°F), better than 71% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
5145-QT205 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 5145-QT205 takes about 34 MJ of energy and emits 2.3 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
5145-QT205's machinability is poor (22/100, worse than 95% of steel grades); weldability poor (15/100); formability fair (45/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 5145-QT205
Is 5145 easy to machine?
Machine in the annealed or ≤32 HRC condition with carbide tooling and rigid setups; above 40 HRC switch to grinding or CBN turning.
Can 5145 be welded?
Poor weldability at 0.45 % C — preheat 250–350 °C, low-hydrogen consumables, and temper immediately after welding to avoid martensitic cracking.
Can 5145 be formed, bent or molded?
Cold form only when spheroidize annealed and in gentle bends; hot work at 1050–1180 °C and always cool slowly or normalize after forging.
What surface finishes work on 5145?
Not corrosion-resistant: use black oxide, phosphate + oil, zinc or hard-chrome plating; bake after plating to relieve hydrogen embrittlement at high hardness.
5145 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 |
|---|---|---|
| Cheat analysis per SAE J404 | 0.43 – 0.48 | 0.46 |
| Mn | 0.7 – 0.9 | 0.8 |
| Si | 0.15 – 0.35 | 0.25 |
| Cr | 0.7 – 0.9 | 0.8 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Fe | balance | — |
5145-QT205 — frequently asked
What is 5145-QT205 used for?
5145-QT205 is typically used for gears, shafts, bushings and hand tools. In short: deep-hardening chromium steel; lower-cost 4140 alternative; poor weldability above 0.4 %C.
What is the yield strength of 5145-QT205?
5145-QT205 has a typical yield strength of 1,660 MPa (241 ksi) and a tensile strength of 1,930 MPa (280 ksi) — stronger than 99% of steel grades. Strength varies by condition: see the 14 listed tempers.
Is 5145-QT205 easy to machine?
Not especially — machinability is rated poor (22/100, worse than 95% of steel grades). Machine in the annealed or ≤32 HRC condition with carbide tooling and rigid setups; above 40 HRC switch to grinding or CBN turning.
Can 5145-QT205 be welded?
Not readily — weldability is rated poor (15/100). Poor weldability at 0.45 % C — preheat 250–350 °C, low-hydrogen consumables, and temper immediately after welding to avoid martensitic cracking.
What surface finishes work on 5145-QT205?
Not corrosion-resistant: use black oxide, phosphate + oil, zinc or hard-chrome plating; bake after plating to relieve hydrogen embrittlement at high hardness.
Can 5145-QT205 be formed, bent or molded?
Cold form only when spheroidize annealed and in gentle bends; hot work at 1050–1180 °C and always cool slowly or normalize after forging.
What is the maximum service temperature of 5145-QT205?
5145-QT205 is rated for continuous use to about 160°C (320 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 5145-A and 5145-QT205?
A is the default condition — standard stock condition: softest, most machinable state before quench-and-temper. QT205: maximum hardness and wear resistance for pins, wear plates and tooling where toughness is secondary. Yield strength is 340 MPa in A versus 1,660 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)
- Machinery's Handbook, 31st ed. (machinability ratings) — Industrial Press (2020)
- GB/T 3077 — (45Cr equivalent) — SAC (2015)
- (alloy round bar) — 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.