Steel 5145
AISI/SAE 5145 · UNS G51450
5145 (UNS G51450) is a medium-carbon chromium through-hardening steel from the SAE 51xx family, strengthened by quenching and tempering rather than by carbide-forming alloy content.
Reference datasheet — 5145 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the A condition
5145 tempers and conditions
5145 is supplied in 14 conditions, soft to hard. A is the default FabDigit quotes; the values on this page are for it.
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 | — |
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?
5145 (UNS G51450) is a medium-carbon chromium through-hardening steel from the SAE 51xx family, strengthened by quenching and tempering rather than by carbide-forming alloy content. It is stocked hot rolled, annealed, spheroidize annealed, normalized and cold drawn, and is supplied in quench-and-temper conditions from 205 to 650 °C or to specified 28–32, 34–38 and 40–45 HRC bands for medium-duty gears, shafts and bushings. In the annealed default condition it shows 340 MPa yield, 620 MPa tensile, 25 % elongation and 180 HB, with service limited to about 400 °C. At 0.45 % C weldability is poor and the steel has no corrosion resistance, so it needs a coating; 4140 is the more widely stocked alternative. 5145 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). 5145 has a yield strength of 340 MPa (49.3 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 76% of steel grades. Elongation at break is 25% and the elastic modulus is 205 GPa (29.7 Msi).
What is 5145 used for?
- gears
- shafts
- bushings
- hand tools
Advantages
- Ductile — tolerates forming and impact — 25%, better than 77% of steel grades
Limitations
- Low strength — 340 MPa (49.3 ksi), worse than 76% of steel grades
5145 properties
Typical room-temperature values for 5145-A; bars are the position among steel grades.
Physical3
5145 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 has a yield strength of 340 MPa (49.3 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 76% of steel grades. Elongation at break is 25% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
5145 is rated for continuous service to 400°C (752 °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 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 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's machinability is good (58/100, better than 75% of steel grades); weldability fair (35/100); formability fair (45/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. 5145 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 5145
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.
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 |
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.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel 5145 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- G51450
How much does 5145 cost?
5145 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
5145 — frequently asked
What is 5145 used for?
5145 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?
5145 has a typical yield strength of 340 MPa (49.3 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 76% of steel grades. Strength varies by condition: see the 14 listed tempers.
Is 5145 easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% 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 be welded?
With care — weldability is rated fair (35/100). 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?
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 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?
5145 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 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.
How much does 5145 cost?
5145 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.