Steel 5155
AISI/SAE 5155 · UNS G51550
5155 (UNS G51550) is a higher-carbon chromium spring steel in the SAE 51xx family, hardened by oil quenching and tempering to spring temper for fatigue-loaded parts.
Reference datasheet — 5155 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 QT 44-48 HRC condition
5155 tempers and conditions
5155 is supplied in 8 conditions, soft to hard. QT 44-48 HRC is the default FabDigit quotes; the values on this page are for it.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
full anneal ~815 °C, slow cool | Softest condition for machining, cold forming or coiling before hardening. | 410 | 720 | 22 | 205 HB | — |
Hot rolled | Cheapest mill condition for parts that will be hot formed and then quenched and tempered. | 530 | 900 | 17 | 25 HRC | 8 % IACS |
~870 °C, air cool | Uniform pearlitic structure for stock removal and pre-hardening machining of larger sections. | 600 | 960 | 18 | 27 HRC | — |
Cold drawn | Close-tolerance bright bar and spring wire feedstock; work-hardened, needs stress relief or full hardening. | 760 | 900 | 11 | 27 HRC | 8 % IACS |
oil quenched, tempered ~650 °C | High-toughness, readily machinable temper when spring action is not required. | 820 | 950 | 20 | 30 HRC | — |
oil quenched, tempered ~540 °C | Tougher, lower-strength temper for shafts, torsion bars and shock-loaded machine parts. | 1,090 | 1,210 | 15 | 38 HRC | — |
QT 44-48 HRCDefault oil quenched ~855 °C, tempered ~425 °C (spring temper) | Standard delivered condition for coil, leaf and torsion springs — best balance of fatigue strength and toughness. | 1,420 | 1,600 | 10 | 46 HRC | — |
oil quenched, tempered 205–315 °C | Maximum strength for highly loaded small springs and wear parts; low toughness, notch sensitive. | 1,700 | 1,930 | 8 | 52 HRC | — |
What is 5155?
5155 (UNS G51550) is a higher-carbon chromium spring steel in the SAE 51xx family, hardened by oil quenching and tempering to spring temper for fatigue-loaded parts. It is supplied annealed, normalized, hot rolled, cold drawn and in quench-and-temper bands from 28–32 up to 50–55 HRC; the default 46 HRC condition gives 1420 MPa yield, 1600 MPa tensile, 10 % elongation and about 435 HB, with service to roughly 250 °C. Formability (score 15) and machinability (score 30) are both low at hardness, and weldability is poor because of the 0.55 % C content. 5160 is the closest and more widely stocked spring-steel alternative. 5155 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). 5155 has a yield strength of 1,420 MPa (206 ksi) and a tensile strength of 1,600 MPa (232 ksi) — stronger than 96% of steel grades. Elongation at break is 10% and the elastic modulus is 205 GPa (29.7 Msi).
What is 5155 used for?
- coil springs
- leaf springs
- clutch parts
Advantages
- High strength — 1,420 MPa (206 ksi), better than 96% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Limited ductility — 10%, worse than 91% of steel grades
- Difficult to machine — 30/100, worse than 89% of steel grades
- Limited formability — 15/100, worse than 87% of steel grades
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
5155 properties
Typical room-temperature values for 5155-QT 44-48 HRC; bars are the position among steel grades.
Physical3
5155 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
5155 has a yield strength of 1,420 MPa (206 ksi) and a tensile strength of 1,600 MPa (232 ksi) — stronger than 96% of steel grades. Elongation at break is 10% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
5155 is rated for continuous service to 250°C (482 °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
5155 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 5155 takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability7
5155's machinability is poor (30/100, worse than 89% of steel grades); weldability poor (20/100); formability poor (15/100).
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. 5155 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 5155
Is 5155 easy to machine?
Machine in the annealed or ≤32 HRC tempered condition with carbide tooling and rigid setups; above 45 HRC use grinding, CBN or hard-turning.
Can 5155 be welded?
Poor weldability — 0.55 %C plus Cr gives martensitic HAZ; if unavoidable use low-hydrogen consumables, 250–350 °C preheat and immediate post-weld temper, and never weld a finished spring.
Can 5155 be formed, bent or molded?
Cold coil only from annealed/drawn wire with generous bend radii; hot form at 900–1050 °C, then oil quench from 830–870 °C and temper 380–480 °C for spring properties.
5155 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 | 0.51 – 0.59 | 0.55 |
| Mn | 0.7 – 0.9 | 0.8 |
| Si | 0.15 – 0.35 | 0.25 |
| Cr | 0.7 – 0.9 | 0.8 |
| Pmax, bar/billet | ≤ 0.04 | |
| Smax, bar/billet | ≤ 0.04 | |
| Fe | balance |
What surface finishes work on 5155?
Shot peen highly stressed springs for fatigue life, then phosphate + oil, powder coat, or zinc plate with a 190–220 °C hydrogen-relief bake to avoid embrittlement.
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 5155 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- G51550
How much does 5155 cost?
5155 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.
5155 — frequently asked
What is 5155 used for?
5155 is typically used for coil springs, leaf springs and clutch parts. In short: high-fatigue spring steel; 1600 MPa tempered strength; not weldable as finished spring.
What is the yield strength of 5155?
5155 has a typical yield strength of 1,420 MPa (206 ksi) and a tensile strength of 1,600 MPa (232 ksi) — stronger than 96% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 5155 easy to machine?
Not especially — machinability is rated poor (30/100, worse than 89% of steel grades). Machine in the annealed or ≤32 HRC tempered condition with carbide tooling and rigid setups; above 45 HRC use grinding, CBN or hard-turning.
Can 5155 be welded?
Not readily — weldability is rated poor (20/100). Poor weldability — 0.55 %C plus Cr gives martensitic HAZ; if unavoidable use low-hydrogen consumables, 250–350 °C preheat and immediate post-weld temper, and never weld a finished spring.
What surface finishes work on 5155?
Shot peen highly stressed springs for fatigue life, then phosphate + oil, powder coat, or zinc plate with a 190–220 °C hydrogen-relief bake to avoid embrittlement.
Can 5155 be formed, bent or molded?
Cold coil only from annealed/drawn wire with generous bend radii; hot form at 900–1050 °C, then oil quench from 830–870 °C and temper 380–480 °C for spring properties.
What is the maximum service temperature of 5155?
5155 is rated for continuous use to about 250°C (482 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 5155 QT 44-48 HRC and 5155-HR?
QT 44-48 HRC is the default condition — standard delivered condition for coil, leaf and torsion springs — best balance of fatigue strength and toughness. HR: cheapest mill condition for parts that will be hot formed and then quenched and tempered. Yield strength is 1,420 MPa in QT 44-48 HRC versus 530 MPa in HR.
How much does 5155 cost?
5155 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 A689 — Carbon and Alloy Steel Bars for Springs — ASTM (2021)
- GB/T 1222 — (55CrMnA) — SAC (2016)
- EN 10089 — Hot rolled steels for quenched and tempered springs (55Cr3) — CEN (2002)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
- Machinery's Handbook, 31st ed. — Industrial Press (2020)
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.