Steel 50B50
EN 50B50 · UNS G50501
50B50 (UNS G50501) is a medium-carbon chromium steel with a boron addition that raises hardenability without extra alloy content, part of the SAE-AISI 13xx-98xx family.
Reference datasheet — 50B50 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
50B50 tempers and conditions
50B50 is supplied in 13 conditions, soft to hard. A is the default FabDigit quotes; the values on this page are for it.
Compare all 13 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Best condition for cold heading, thread rolling and deep machining of this 0.50 %C grade. | 350 | 640 | 25 | 180 HB | 8 % IACS |
ADefault Solution annealed | Standard stocking condition: softest state for machining, cold forming and subsequent hardening. | 380 | 700 | 21 | 197 HB | — |
Hot rolled | Cheapest mill condition for parts that will be re-heat-treated after forming or machining. | 460 | 800 | 16 | 22 HRC | 8 % IACS |
Normalized | Uniform fine-grain structure before hardening, or a moderate-strength as-supplied condition. | 550 | 900 | 19 | 26 HRC | — |
Cold drawn | Close tolerance, bright finish and higher yield for machined pins and shafts not needing full hardening. | 660 | 790 | 12 | 20 HRC | 8 % IACS |
oil quenched, tempered 650 °C | Softest Q&T condition — best ductility and impact energy for heavily loaded but shock-prone parts. | 760 | 870 | 20 | 27 HRC | — |
oil quenched, tempered 540 °C | Tough machine-part temper (~35 HRC) for shafts, pins and links loaded in shock. | 1,060 | 1,150 | 15 | 35 HRC | — |
hardness-specified quench & temper | Purchase-by-hardness condition for gears, links and moderate-wear components needing residual toughness. | 1,180 | 1,300 | 13 | 40 HRC | — |
oil quenched, tempered 425 °C | Classic leaf-spring / high-strength fastener temper balancing strength and fatigue life. | 1,350 | 1,450 | 11 | 43 HRC | — |
hardness-specified quench & temper | Typical spring and abrasion-service hardness band for 50B50 plate and bar. | 1,420 | 1,570 | 10 | 46 HRC | — |
oil quenched, tempered 315 °C | High-hardness spring/wear condition with slightly improved ductility over 205 °C temper. | 1,570 | 1,740 | 9 | 49 HRC | — |
hardness-specified quench & temper | Maximum-wear condition for plow shares, sweeps, cutting edges and wear strips; avoid impact/notches. | 1,650 | 1,880 | 7 | 52 HRC | — |
oil quenched, tempered 205 °C | Maximum hardness and wear resistance for tillage tools and wear plate; very low toughness. | 1,700 | 1,930 | 6 | 53 HRC | — |
What is 50B50?
50B50 (UNS G50501) is a medium-carbon chromium steel with a boron addition that raises hardenability without extra alloy content, part of the SAE-AISI 13xx-98xx family. It is used for through-hardened springs, fasteners and wear parts, and is available hot rolled, annealed, spheroidized, normalized, cold drawn, and quenched and tempered from 205 °C to 650 °C or to 38-42, 44-48 and 50-55 HRC bands. The reference annealed values are 380 MPa yield, 700 MPa tensile, 21 % elongation and 197 HB (92 HRB), with service to 425 °C. Weldability is poor (CE ≈ 0.75) and there is no corrosion resistance; 50B60 or 5160 is the usual step up in carbon for spring duty. 50B50 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). 50B50 has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 68% of steel grades. Elongation at break is 21% and the elastic modulus is 205 GPa (29.7 Msi).
What is 50B50 used for?
- leaf springs
- high-strength bolts
- wear plates
Limitations
- Difficult to weld — 25/100, worse than 77% of steel grades
50B50 properties
Typical room-temperature values for 50B50-A; bars are the position among steel grades.
Physical3
50B50 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
50B50 has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 68% of steel grades. Elongation at break is 21% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
50B50 is rated for continuous service to 425°C (797 °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
50B50 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 50B50 takes about 30 MJ of energy and emits 2.2 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability6
50B50's machinability is fair (52/100, better than 52% of steel grades); weldability poor (25/100); 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. 50B50 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 50B50
Is 50B50 easy to machine?
Machine in the annealed or spheroidized state (~60 % of 1212) with rigid setups and coated carbide; above 45 HRC switch to CBN/grinding.
Can 50B50 be welded?
Poor weldability — CE ≈ 0.75; use low-hydrogen consumables, 250–350 °C preheat, controlled interpass and immediate PWHT, and expect a hard, crack-prone HAZ.
Can 50B50 be formed, bent or molded?
Cold form or coil only when annealed/spheroidized with generous bend radii; hot work at 1050–1200 °C, austenitize 830–860 °C (do not overheat — boron effect is lost) and quench in oil.
50B50 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 | 0.48 – 0.53 | 0.5 |
| Mn | 0.75 – 1 | 0.88 |
| Si | 0.15 – 0.35 | 0.25 |
| Cr | 0.4 – 0.6 | 0.5 |
| Bboron addition for hardenability; requires fully killed, Ti/Al-treated steel | 5×10⁻⁴ – 0 | 0 |
| P | ≤ 0.04 | |
| S | ≤ 0.04 | |
| Fe | balance |
What surface finishes work on 50B50?
No natural corrosion protection: use phosphate-and-oil, black oxide, paint or zinc; bake plated parts above 40 HRC at 190–220 °C to relieve hydrogen 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 50B50 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- G50501
How much does 50B50 cost?
50B50 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.
50B50 — frequently asked
What is 50B50 used for?
50B50 is typically used for leaf springs, high-strength bolts and wear plates. In short: boron-boosted hardenability; through-hardening spring steel; hardness bands to 55 HRC.
What is the yield strength of 50B50?
50B50 has a typical yield strength of 380 MPa (55.1 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 68% of steel grades. Strength varies by condition: see the 13 listed tempers.
Is 50B50 easy to machine?
Reasonably — machinability is rated fair (52/100, better than 52% of steel grades). Machine in the annealed or spheroidized state (~60 % of 1212) with rigid setups and coated carbide; above 45 HRC switch to CBN/grinding.
Can 50B50 be welded?
Not readily — weldability is rated poor (25/100). Poor weldability — CE ≈ 0.75; use low-hydrogen consumables, 250–350 °C preheat, controlled interpass and immediate PWHT, and expect a hard, crack-prone HAZ.
What surface finishes work on 50B50?
No natural corrosion protection: use phosphate-and-oil, black oxide, paint or zinc; bake plated parts above 40 HRC at 190–220 °C to relieve hydrogen embrittlement.
Can 50B50 be formed, bent or molded?
Cold form or coil only when annealed/spheroidized with generous bend radii; hot work at 1050–1200 °C, austenitize 830–860 °C (do not overheat — boron effect is lost) and quench in oil.
What is the maximum service temperature of 50B50?
50B50 is rated for continuous use to about 425°C (797 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 50B50-A and 50B50-QT205?
A is the default condition — standard stocking condition: softest state for machining, cold forming and subsequent hardening. QT205: maximum hardness and wear resistance for tillage tools and wear plate; very low toughness. Yield strength is 380 MPa in A versus 1,700 MPa in QT205.
How much does 50B50 cost?
50B50 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)
- SAE J1268 — Hardenability Bands for Boron H-Steels — SAE International (2018)
- 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.4A — Steel Heat Treating Fundamentals and Processes — ASM International (2013)
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.