Steel 15B48-Q (As-quenched, untempered)
Heat-treated state
EN 15B48 · UNS G15481
Intermediate state only — full martensitic hardness but brittle; must be tempered before service.
Values for the Q condition
Other 15B48 tempers and conditions
15B48 is listed in 10 conditions; see the grade overview at 15B48.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefault Solution annealed | Standard stocked condition: softest, most ductile structure for cold heading, upsetting and thread rolling before quench-and-temper. | 385 | 585 | 22 | 170 HB | — |
Hot rolled | Cheapest mill condition for parts that will be hot forged or fully re-heat-treated later. | 420 | 700 | 15 | 201 HB | — |
Normalized | Use to homogenize forgings and refine grain before final hardening or machining. | 450 | 760 | 18 | 17 HRC | 9.5 % IACS |
Cold drawn | Pick for straight, close-tolerance bar where moderate strength without heat treatment is enough. | 670 | 780 | 10 | 20 HRC | 9.5 % IACS |
quenched and tempered (~540 °C) | Toughest quench-and-temper level; used when impact loading or later machining matters more than peak strength. | 830 | 965 | 16 | 30 HRC | — |
quenched and tempered (~480 °C) | Balanced strength/toughness for grade 8-class cold-headed fasteners and shafting. | 1,050 | 1,170 | 13 | 36 HRC | — |
Induction hardened | Choose when only a wear-resistant surface layer is needed on a tough, previously Q&T or normalized core. | 1,250 | 1,550 | 6 | 55 HRC | 8.5 % IACS |
quenched and tempered (~400 °C) | High-strength condition for chain, socket screws and hand tools needing wear resistance with some ductility. | 1,280 | 1,400 | 10 | 43 HRC | — |
quenched and low tempered (~205 °C) | Maximum strength and wear resistance for track links, cutting edges and tools where toughness is secondary. | 1,500 | 1,720 | 7 | 50 HRC | — |
QThis page As-quenched, untempered | Intermediate state only — full martensitic hardness but brittle; must be tempered before service. | 1,650 | 2,050 | 2 | 57 HRC | 7.5 % IACS |
What is 15B48-Q?
15B48-Q is 15B48 heat treated to Q — intermediate state only — full martensitic hardness but brittle; must be tempered before service. 15B48-Q has a yield strength of 1,650 MPa (239 ksi) and a tensile strength of 2,050 MPa (297 ksi) — stronger than 99% of steel grades. Elongation at break is 2% and the elastic modulus is 200 GPa (29 Msi). 15B48-Q 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). A is the default condition FabDigit quotes; Q is available on request or by drawing note.
Advantages
- High strength — 1,650 MPa (239 ksi), better than 99% of steel grades
Limitations
- Difficult to weld — 5/100, worse than 100% of steel grades
- Limited formability — 2/100, worse than 100% of steel grades
- Limited ductility — 2%, worse than 99% of steel grades
- Limited service temperature — 150°C (302 °F), worse than 99% of steel grades
- Difficult to machine — 10/100, worse than 99% of steel grades
15B48-Q properties
Typical room-temperature values for 15B48-Q; 22 are specific to this condition. Other listed values are 15B48 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
15B48-Q 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).
Mechanical13
15B48-Q has a yield strength of 1,650 MPa (239 ksi) and a tensile strength of 2,050 MPa (297 ksi) — stronger than 99% of steel grades. Elongation at break is 2% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
15B48-Q is rated for continuous service to 150°C (302 °F). It conducts heat at 43 W/m·K (24.8 BTU/hr·ft·°F), better than 51% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
15B48-Q conducts electricity at 7.5 % IACS, worse than 67% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (8/100), worse than 99% of steel grades.
Sustainability4
Producing a kilogram of 15B48-Q takes about 27 MJ of energy and emits 2 kg of CO₂ — less than 59% of steel grades. Typical recycled content is 30%.
Manufacturability7
15B48-Q's machinability is not recommended (10/100, worse than 99% of steel grades); weldability not recommended (5/100); formability not recommended (2/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 15B48-Q
Is 15B48 easy to machine?
Machine in the spheroidize-annealed or ≤32 HRC condition with rigid setups and coated carbide; above 40 HRC expect grinding or CBN finishing only.
Can 15B48 be welded?
Poor weldability (Ceq ≈ 0.7): preheat 200–300 °C, low-hydrogen consumables and immediate post-weld temper, otherwise expect HAZ martensite cracking.
Can 15B48 be formed, bent or molded?
Excellent for cold heading/upsetting and thread rolling as CHQ spheroidized wire; hot forge 1100–1200 °C and normalize before hardening.
What surface finishes work on 15B48?
Not anodizable — protect with zinc or zinc-nickel plate, zinc-flake, or phosphate-and-oil; bake within 4 h after plating on parts above ~1000 MPa to avoid hydrogen embrittlement.
15B48 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 |
|---|---|---|
| Cboron-treated medium-carbon base | 0.44 – 0.53 | 0.48 |
| Mn | 1 – 1.3 | 1.15 |
| Sihot-rolled/CHQ deoxidation range | 0.15 – 0.35 | 0.25 |
| Bsoluble boron; Ti/Al used to tie up nitrogen | 5×10⁻⁴ – 0 | 0 |
| P | ≤ 0.03 | — |
| Smax; lower for CHQ wire | ≤ 0.05 | — |
| Fe | balance | — |
15B48-Q — frequently asked
What is 15B48-Q used for?
15B48-Q is typically used for high-tensile bolts, automotive fasteners, cold-headed studs and pins, induction-hardened shafts, track and linkage components and hardened washers and sleeves. In short: deep-hardening CHQ wire; hardens to 48–52 HRC; effectively non-weldable.
What is the yield strength of 15B48-Q?
15B48-Q has a typical yield strength of 1,650 MPa (239 ksi) and a tensile strength of 2,050 MPa (297 ksi) — stronger than 99% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 15B48-Q easy to machine?
Not especially — machinability is rated not recommended (10/100, worse than 99% of steel grades). Machine in the spheroidize-annealed or ≤32 HRC condition with rigid setups and coated carbide; above 40 HRC expect grinding or CBN finishing only.
Can 15B48-Q be welded?
Not readily — weldability is rated not recommended (5/100). Poor weldability (Ceq ≈ 0.7): preheat 200–300 °C, low-hydrogen consumables and immediate post-weld temper, otherwise expect HAZ martensite cracking.
What surface finishes work on 15B48-Q?
Not anodizable — protect with zinc or zinc-nickel plate, zinc-flake, or phosphate-and-oil; bake within 4 h after plating on parts above ~1000 MPa to avoid hydrogen embrittlement.
Can 15B48-Q be formed, bent or molded?
Excellent for cold heading/upsetting and thread rolling as CHQ spheroidized wire; hot forge 1100–1200 °C and normalize before hardening.
What is the maximum service temperature of 15B48-Q?
15B48-Q is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 15B48-A and 15B48-Q?
A is the default condition — standard stocked condition: softest, most ductile structure for cold heading, upsetting and thread rolling before quench-and-temper. Q: intermediate state only — full martensitic hardness but brittle; must be tempered before service. Yield strength is 385 MPa in A versus 1,650 MPa in Q.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- SAE J1268 — Hardenability Bands for Alloy H Steels — SAE International (2019)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought, General Requirements — ASTM (2020)
- ASTM A510/A510M — General Requirements for Wire Rods and Coarse Round Wire, Carbon Steel and Alloy Steel — ASTM (2018)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating (boron steels, hardenability) — ASM International (1991)
- ASM Handbook Vol.16 — Machining — ASM International (1989)
- GB/T 6478 / GB/T 3077 — / (ML45MnB comparison) — 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.