Steel 55SiMnVB
GB 55SiMnVB
55SiMnVB is a silicon-manganese spring steel micro-alloyed with vanadium and boron, formulated as a low-cost, high-hardenability substitute for chromium-vanadium spring steels in heavy leaf springs.
Reference datasheet — 55SiMnVB 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 QT460 condition
55SiMnVB tempers and conditions
55SiMnVB is supplied in 7 conditions, soft to hard. QT460 is the default FabDigit quotes; the values on this page are for it.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Choose when the bar must be cold-sheared, punched, straightened or machined before heat treatment. | 430 | 720 | 18 | 215 HB | — |
Hot rolled | Mill delivery condition for spring flats and rounds that the spring maker will hot-form, quench and temper in-house. | 550 | 900 | 13 | 27 HRC | — |
Normalized | Grain-refining pre-treatment after forging or hot forming, before final quench and temper. | 600 | 950 | 12 | 30 HRC | 7 % IACS |
Cold drawn | Small-diameter rod and wire supplied cold drawn to size for wound springs that are hardened and tempered after coiling. | 780 | 950 | 9 | 30 HRC | 7 % IACS |
Oil quenched 860 °C, tempered ~520 °C | Pick when impact toughness and crack tolerance in thick leaf sections matter more than peak spring load capacity. | 1,130 | 1,280 | 11 | 40 HRC | — |
QT460Default Oil quenched 860 °C, tempered 460 °C | Standard spring service condition and the basis of the GB/T 1222 property minima; best strength–toughness balance for heavy leaf springs. | 1,320 | 1,500 | 8 | 45 HRC | — |
Oil quenched 860 °C, tempered ~400 °C | Highest strength/relaxation resistance for coil springs and torsion bars where toughness demand is moderate. | 1,550 | 1,750 | 6 | 50 HRC | — |
What is 55SiMnVB?
55SiMnVB is a silicon-manganese spring steel micro-alloyed with vanadium and boron, formulated as a low-cost, high-hardenability substitute for chromium-vanadium spring steels in heavy leaf springs. Quenched and tempered it reaches about 1320 MPa yield, 1500 MPa tensile, 8 % elongation and 425 HB (45 HRC), suiting thick leaf sections that must through-harden. Limits are a service temperature of about 250 °C, poor machinability (score 25), very low cold formability (score 10) and poor weldability (score 20), plus no corrosion resistance. 51CrV4 or 60CrMnA are the nearest alternatives when higher toughness or established fatigue data is required. 55SiMnVB 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). 55SiMnVB has a yield strength of 1,320 MPa (191 ksi) and a tensile strength of 1,500 MPa (218 ksi) — stronger than 95% of steel grades. Elongation at break is 8% and the elastic modulus is 206 GPa (29.9 Msi).
What is 55SiMnVB used for?
- Truck leaf springs
- Heavy vehicle suspension springs
- Parabolic trailer springs
- Off-highway and agricultural machinery springs
- Heavy coil springs
- Spring plates and clamp bands
Advantages
- High strength — 1,320 MPa (191 ksi), better than 95% of steel grades
Limitations
- Limited ductility — 8%, worse than 95% of steel grades
- Limited formability — 10/100, worse than 95% of steel grades
- Difficult to machine — 25/100, worse than 93% 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
55SiMnVB properties
Typical room-temperature values for 55SiMnVB-QT460; bars are the position among steel grades.
Physical3
55SiMnVB 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
55SiMnVB has a yield strength of 1,320 MPa (191 ksi) and a tensile strength of 1,500 MPa (218 ksi) — stronger than 95% of steel grades. Elongation at break is 8% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
55SiMnVB is rated for continuous service to 250°C (482 °F). It conducts heat at 40 W/m·K (23.1 BTU/hr·ft·°F), worse than 64% of steel grades. Thermal expansion is 12.5 µm/m·K (6.94 µin/in·°F).
Electrical3
55SiMnVB conducts electricity at 6.4 % IACS, worse than 77% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of 55SiMnVB takes about 27 MJ of energy and emits 2.1 kg of CO₂ — less than 59% of steel grades. Typical recycled content is 30%.
Manufacturability6
55SiMnVB's machinability is poor (25/100, worse than 93% of steel grades); weldability poor (20/100); formability not recommended (10/100).
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. 55SiMnVB is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 55SiMnVB
Is 55SiMnVB easy to machine?
Machine in the annealed condition (carbide, 80–120 m/min); after quench and temper at 45 HRC expect grinding or CBN turning only, and keep decarburised skin off finished spring surfaces.
Can 55SiMnVB be welded?
Not recommended for load-bearing joints — 0.55 %C plus boron gives high hardenability and cold cracking; if unavoidable, preheat 250–350 °C, low-hydrogen consumables and immediate post-weld temper.
Can 55SiMnVB be formed, bent or molded?
Hot form/roll leaf ends and coil at 900–1000 °C, then oil quench from 850–870 °C and temper 400–520 °C; cold bending is only feasible in the annealed state.
55SiMnVB 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 | 0.52 – 0.6 | 0.56 |
| Si | 0.7 – 1 | 0.85 |
| Mn | 1 – 1.3 | 1.15 |
| Vgrain refinement, temper resistance | 0.08 – 0.16 | 0.12 |
| Bhardenability booster; requires low free N | 5×10⁻⁴ – 0 | 0 |
| Crresidual | ≤ 0.35 | |
| Niresidual | ≤ 0.35 | |
| Curesidual | ≤ 0.25 | |
| P | ≤ 0.03 | |
| S | ≤ 0.02 | |
| Fe | balance |
What surface finishes work on 55SiMnVB?
Shot peen springs after tempering for fatigue life, then phosphate + epoxy/powder paint or zinc-rich primer; avoid acid pickling and electroplating on the hardened part unless followed by a 200 °C hydrogen bake-out.
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
How much does 55SiMnVB cost?
55SiMnVB 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.
55SiMnVB — frequently asked
What is 55SiMnVB used for?
55SiMnVB is typically used for truck leaf springs, heavy vehicle suspension springs, parabolic trailer springs, off-highway and agricultural machinery springs, heavy coil springs and spring plates and clamp bands. In short: low-cost Cr-V spring substitute; high hardenability from boron; highest hardness of the spring pair.
What is the yield strength of 55SiMnVB?
55SiMnVB has a typical yield strength of 1,320 MPa (191 ksi) and a tensile strength of 1,500 MPa (218 ksi) — stronger than 95% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 55SiMnVB easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% of steel grades). Machine in the annealed condition (carbide, 80–120 m/min); after quench and temper at 45 HRC expect grinding or CBN turning only, and keep decarburised skin off finished spring surfaces.
Can 55SiMnVB be welded?
Not readily — weldability is rated poor (20/100). Not recommended for load-bearing joints — 0.55 %C plus boron gives high hardenability and cold cracking; if unavoidable, preheat 250–350 °C, low-hydrogen consumables and immediate post-weld temper.
What surface finishes work on 55SiMnVB?
Shot peen springs after tempering for fatigue life, then phosphate + epoxy/powder paint or zinc-rich primer; avoid acid pickling and electroplating on the hardened part unless followed by a 200 °C hydrogen bake-out.
Can 55SiMnVB be formed, bent or molded?
Hot form/roll leaf ends and coil at 900–1000 °C, then oil quench from 850–870 °C and temper 400–520 °C; cold bending is only feasible in the annealed state.
What is the maximum service temperature of 55SiMnVB?
55SiMnVB 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 55SiMnVB-QT460 and 55SiMnVB-A?
QT460 is the default condition — standard spring service condition and the basis of the GB/T 1222 property minima; best strength–toughness balance for heavy leaf springs. A: choose when the bar must be cold-sheared, punched, straightened or machined before heat treatment. Yield strength is 1,320 MPa in QT460 versus 430 MPa in A.
How much does 55SiMnVB cost?
55SiMnVB 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
- GB/T 1222 (Spring steels) (2016)
- (Handbook of Iron and Steel Materials) (2009)
- ASM Handbook Vol. 1: Properties and Selection — Irons, Steels and High-Performance Alloys — ASM International (1990)
- (Spring Design Handbook) (2008)
- Hardness conversion tables for metals — ASTM E140 (2019)
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.