Steel 15B37-A (Solution annealed)
Temper
EN 15B37 · UNS G15371
Softest condition — chosen for cold-heading wire and for machining before quench and temper.
Values for the A condition
Other 15B37 tempers and conditions
15B37 is listed in 8 conditions; see the grade overview at 15B37.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AThis page 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-A?
15B37-A is 15B37 in the A temper — softest condition — chosen for cold-heading wire and for machining before quench and temper. 15B37-A has a yield strength of 340 MPa (49.3 ksi) and a tensile strength of 570 MPa (82.7 ksi) — weaker than 76% of steel grades. Elongation at break is 28% and the elastic modulus is 205 GPa (29.7 Msi). 15B37-A 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). QT32-38 is the default condition FabDigit quotes; A is available on request or by drawing note.
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- Ductile — tolerates forming and impact — 28%, better than 89% of steel grades
- Easy to machine — 62/100, better than 89% of steel grades
- Forms and bends easily — 70/100, better than 86% of steel grades
Limitations
- Limited service temperature — 300°C (572 °F), worse than 78% of steel grades
- Low strength — 340 MPa (49.3 ksi), worse than 76% of steel grades
15B37-A properties
Typical room-temperature values for 15B37-A; 10 are specific to this condition. Other listed values are 15B37 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
15B37-A 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-A has a yield strength of 340 MPa (49.3 ksi) and a tensile strength of 570 MPa (82.7 ksi) — weaker than 76% of steel grades. Elongation at break is 28% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
15B37-A 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-A 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-A 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-A's machinability is good (62/100, better than 89% of steel grades); weldability fair (35/100); formability very good (70/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 15B37-A
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).
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.
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 | — |
15B37-A — frequently asked
What is 15B37-A used for?
15B37-A 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-A?
15B37-A has a typical yield strength of 340 MPa (49.3 ksi) and a tensile strength of 570 MPa (82.7 ksi) — weaker than 76% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 15B37-A easy to machine?
Reasonably — machinability is rated good (62/100, better than 89% 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-A 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-A?
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-A 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-A?
15B37-A 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.