Steel 15B37
EN 15B37 · UNS G15371
15B37 is a boron-treated medium-carbon manganese steel (UNS G15371) in the SAE-AISI 15xx series, where a small boron addition raises hardenability so the grade can replace higher-alloy steels in quenched-and-tempered parts.
Reference datasheet — 15B37 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 QT32-38 condition
15B37 tempers and conditions
15B37 is supplied in 8 conditions, soft to hard. QT32-38 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 |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition — chosen for cold-heading wire and for machining before quench and temper. | 340 | 570 | 28 | 163 HB | — |
Hot rolled | Cheapest stocking condition for bar to be re-heat-treated by the user. | 400 | 640 | 22 | 187 HB | — |
Normalized | Uniform fine pearlitic structure for forgings prior to machining or hardening. | 430 | 700 | 20 | 14 HRC | 9 % IACS |
Cold drawn | Straight, close-tolerance bar with raised yield strength for as-supplied machined parts. | 620 | 730 | 12 | 217 HB | — |
Q&T 26–32 HRC | Tough, ductile fastener/machine-part condition equivalent to SAE J429 Grade 5 / property class 8.8. | 800 | 930 | 17 | 29 HRC | — |
QT32-38Default Q&T 32–38 HRC | Standard high-strength fastener condition (SAE J429 Grade 8 / ASTM A354 BD / class 10.9) — the usual reason 15B37 is specified. | 980 | 1,100 | 14 | 35 HRC | — |
Q&T 38–44 HRC | Maximum practical strength for socket screws and high-load pins; hydrogen-embrittlement risk rises sharply — avoid acid pickling / electroplating without baking. | 1,200 | 1,350 | 11 | 41 HRC | — |
Quenched, untempered | Reference condition only — boron gives near-full martensite in sections up to ~25 mm; must be tempered before use. | 1,450 | 1,900 | 2 | 53 HRC | 6.5 % IACS |
What is 15B37?
15B37 is a boron-treated medium-carbon manganese steel (UNS G15371) in the SAE-AISI 15xx series, where a small boron addition raises hardenability so the grade can replace higher-alloy steels in quenched-and-tempered parts. It is stocked hot-rolled, annealed, normalized, cold-drawn, as-quenched and in QT bands of 26–32, 32–38 and 38–44 HRC; the reference condition gives 980 MPa yield, 1100 MPa tensile, 14 % elongation and 331 HB (35 HRC). Machinability is 45, weldability is poor, service is limited to about 300 °C and there is no corrosion resistance. 4140 is the alternative when section sizes exceed the boron hardenability benefit. 15B37 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). 15B37 has a yield strength of 980 MPa (142 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 91% of steel grades. Elongation at break is 14% and the elastic modulus is 205 GPa (29.7 Msi).
What is 15B37 used for?
- bolts
- fasteners
- agricultural parts
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High strength — 980 MPa (142 ksi), better than 91% of steel grades
Limitations
- Limited service temperature — 300°C (572 °F), worse than 78% of steel grades
- Limited ductility — 14%, worse than 75% of steel grades
15B37 properties
Typical room-temperature values for 15B37-QT32-38; bars are the position among steel grades.
Physical3
15B37 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).
Mechanical15
15B37 has a yield strength of 980 MPa (142 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 91% of steel grades. Elongation at break is 14% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
15B37 is rated for continuous service to 300°C (572 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
15B37 conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 15B37 takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability6
15B37's machinability is fair (45/100, worse than 65% 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. 15B37 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 15B37
Is 15B37 easy to machine?
Machine in the spheroidize-annealed or cold-drawn condition (~50–70 % of 1212); above 35 HRC use coated carbide with rigid setups, and expect grinding for finish work.
Can 15B37 be welded?
Poor weldability — carbon equivalent ≈0.6; if welding is unavoidable use low-hydrogen consumables, 200–300 °C preheat and post-weld temper, and never weld heat-treated fasteners.
Can 15B37 be formed, bent or molded?
Excellent cold-heading behaviour after spheroidize anneal plus phosphate/lubricant coating; hot forge 1100–1200 °C, then normalize before quench-and-temper (austenitize ~860–880 °C, oil or polymer quench, temper 400–600 °C to hardness).
15B37 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 | 0.34 – 0.41 | 0.37 |
| Mn | 1.3 – 1.65 | 1.45 |
| Sikilled steel silicon range | 0.15 – 0.35 | 0.22 |
| Beffective (soluble) boron; Ti/Al used to fix N | 5×10⁻⁴ – 0 | 0 |
| P | ≤ 0.03 | |
| S | ≤ 0.05 | |
| Fe | balance |
What surface finishes work on 15B37?
No inherent corrosion resistance — zinc electroplate (bake 190–220 °C within 4 h to relieve hydrogen at ≥32 HRC), zinc-flake dip-spin, phosphate-and-oil or hot-dip galvanizing are standard.
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 15B37 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- G15371
How much does 15B37 cost?
15B37 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.
15B37 — frequently asked
What is 15B37 used for?
15B37 is typically used for bolts, fasteners and agricultural parts. In short: low-cost 4140 substitute; boron-boosted hardenability; strong cold-heading grade.
What is the yield strength of 15B37?
15B37 has a typical yield strength of 980 MPa (142 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 91% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 15B37 easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine in the spheroidize-annealed or cold-drawn condition (~50–70 % of 1212); above 35 HRC use coated carbide with rigid setups, and expect grinding for finish work.
Can 15B37 be welded?
With care — weldability is rated fair (35/100). Poor weldability — carbon equivalent ≈0.6; if welding is unavoidable use low-hydrogen consumables, 200–300 °C preheat and post-weld temper, and never weld heat-treated fasteners.
What surface finishes work on 15B37?
No inherent corrosion resistance — zinc electroplate (bake 190–220 °C within 4 h to relieve hydrogen at ≥32 HRC), zinc-flake dip-spin, phosphate-and-oil or hot-dip galvanizing are standard.
Can 15B37 be formed, bent or molded?
Excellent cold-heading behaviour after spheroidize anneal plus phosphate/lubricant coating; hot forge 1100–1200 °C, then normalize before quench-and-temper (austenitize ~860–880 °C, oil or polymer quench, temper 400–600 °C to hardness).
What is the maximum service temperature of 15B37?
15B37 is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 15B37 QT32-38 and 15B37-A?
QT32-38 is the default condition — standard high-strength fastener condition (SAE J429 Grade 8 / ASTM A354 BD / class 10.9) — the usual reason 15B37 is specified. A: softest condition — chosen for cold-heading wire and for machining before quench and temper. Yield strength is 980 MPa in QT32-38 versus 340 MPa in A.
How much does 15B37 cost?
15B37 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 J403 / J404 — Chemical Compositions of SAE Carbon and Alloy Steels — SAE International (2014)
- SAE J429 — Mechanical and Material Requirements for Externally Threaded Fasteners — SAE International (2014)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought, General Requirements — ASTM (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating (boron hardenability) — ASM International (1991)
- GB/T 6478 / GB/T 3077 (ML35B ) — SAC (2015)
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.