Steel 5155-HR (Hot rolled)
Supply condition
AISI/SAE 5155 · UNS G51550
Cheapest mill condition for parts that will be hot formed and then quenched and tempered.
Values for the HR condition
Other 5155 tempers and conditions
5155 is listed in 8 conditions; see the grade overview at 5155.
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 | — |
HRThis page 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-HR?
5155-HR is 5155 supplied in the HR condition — cheapest mill condition for parts that will be hot formed and then quenched and tempered. 5155-HR has a yield strength of 530 MPa (76.9 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 69% of steel grades. Elongation at break is 17% and the elastic modulus is 205 GPa (29.7 Msi). 5155-HR 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). QT 44-48 HRC is the default condition FabDigit quotes; HR is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Difficult to weld — 25/100, worse than 77% of steel grades
5155-HR properties
Typical room-temperature values for 5155-HR; 23 are specific to this condition. Other listed values are 5155 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
5155-HR 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-HR has a yield strength of 530 MPa (76.9 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 69% of steel grades. Elongation at break is 17% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
5155-HR 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 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
5155-HR 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 5155-HR 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-HR's machinability is fair (45/100, worse than 65% of steel grades); weldability poor (25/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 5155-HR
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.
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.
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 | — |
5155-HR — frequently asked
What is 5155-HR used for?
5155-HR 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-HR?
5155-HR has a typical yield strength of 530 MPa (76.9 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 69% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 5155-HR easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% 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-HR be welded?
Not readily — weldability is rated poor (25/100). 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-HR?
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-HR 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-HR?
5155-HR 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 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.