Steel 10B38 Q&T 40-45 HRC
Hardness band
EN 10B38 · UNS G10381
Q&T 40-45 HRC = quenched and low-tempered
For wear-loaded pins, plough shares and studs where hardness matters more than toughness.
Values for the Q&T 40-45 HRC condition
Other 10B38 tempers and conditions
10B38 is listed in 8 conditions; see the grade overview at 10B38.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
spheroidize annealed, cold heading quality | Spheroidized wire for severe cold heading of bolt blanks; the normal starting condition for 8.8/10.9 fastener production. | 270 | 480 | 30 | 140 HB | 10 % IACS |
full anneal (soft) | Softest condition, for maximum cold formability and machining of complex shapes before hardening. | 285 | 515 | 25 | 149 HB | 10 % IACS |
HRDefault Hot rolled | Default stock form for wire rod and bar destined for cold heading or subsequent Q&T. | 320 | 570 | 20 | 163 HB | 10 % IACS |
austenitized and air cooled | Uniform fine-grain structure and predictable response to later quenching; used to reset banded hot-rolled structure. | 335 | 565 | 22 | 163 HB | 10 % IACS |
Cold rolled | Pick for close tolerance, smooth surface and higher as-supplied strength when no further heat treatment is planned. | 540 | 640 | 12 | 190 HB | 10 % IACS |
Quenched and tempered | Standard bolt condition: oil/water quench plus high temper, giving 800–830 MPa class strength with good ductility. | 740 | 900 | 17 | 29 HRC | — |
Quenched and tempered | Higher-strength fastener condition (~1040 MPa class); watch for hydrogen embrittlement risk after plating. | 960 | 1,100 | 13 | 35 HRC | — |
Q&T 40-45 HRCThis page Quenched and low-tempered | For wear-loaded pins, plough shares and studs where hardness matters more than toughness. | 1,180 | 1,350 | 10 | 43 HRC | 9 % IACS |
What is 10B38 Q&T 40-45 HRC?
10B38 Q&T 40-45 HRC is 10B38 heat treated to Q&T 40-45 HRC — for wear-loaded pins, plough shares and studs where hardness matters more than toughness. 10B38 Q&T 40-45 HRC has a yield strength of 1,180 MPa (171 ksi) and a tensile strength of 1,350 MPa (196 ksi) — stronger than 94% of steel grades. Elongation at break is 10% and the elastic modulus is 205 GPa (29.7 Msi). 10B38 Q&T 40-45 HRC 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). HR is the default condition FabDigit quotes; Q&T 40-45 HRC is available on request or by drawing note.
Advantages
- High strength — 1,180 MPa (171 ksi), better than 94% of steel grades
Limitations
- Limited formability — 10/100, worse than 95% of steel grades
- Limited ductility — 10%, worse than 91% of steel grades
- Difficult to machine — 30/100, worse than 89% of steel grades
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
- Difficult to weld — 25/100, worse than 77% of steel grades
10B38 Q&T 40-45 HRC properties
Typical room-temperature values for 10B38 Q&T 40-45 HRC; 22 are specific to this condition. Other listed values are 10B38 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
10B38 Q&T 40-45 HRC 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
10B38 Q&T 40-45 HRC has a yield strength of 1,180 MPa (171 ksi) and a tensile strength of 1,350 MPa (196 ksi) — stronger than 94% of steel grades. Elongation at break is 10% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
10B38 Q&T 40-45 HRC is rated for continuous service to 250°C (482 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
10B38 Q&T 40-45 HRC conducts electricity at 9 % IACS, better than 71% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 10B38 Q&T 40-45 HRC takes about 25 MJ of energy and emits 2 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
10B38 Q&T 40-45 HRC's machinability is poor (30/100, worse than 89% of steel grades); weldability poor (25/100); formability not recommended (10/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 10B38 Q&T 40-45 HRC
Is 10B38 easy to machine?
Machines like 1038 (≈60% of 1212); best in normalized or Q&T-to-~30 HRC condition, use rigid setups and carbide at moderate speed — boron slightly raises tool wear.
Can 10B38 be welded?
Weldable by SMAW/GMAW/resistance methods but 0.39% C plus boron gives high hardenability: preheat 150–250 °C, low-hydrogen consumables and post-weld temper to avoid HAZ cracking.
Can 10B38 be formed, bent or molded?
In spheroidize-annealed CHQ wire it cold-heads and thread-rolls readily; hot forge 1100–1250 °C, then normalize before quench-hardening for consistent boron effect.
What surface finishes work on 10B38?
No inherent corrosion resistance — use zinc or zinc-nickel electroplate (bake to relieve hydrogen at >32 HRC), hot-dip galvanizing, phosphate+oil, or zinc-flake coatings; polishes to a fair finish only.
10B38 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 |
|---|---|---|
| CSAE J403 10B38 | 0.35 – 0.43 | 0.39 |
| Mn | 0.6 – 0.9 | 0.75 |
| Sibar/rod; may be 0.10 min for CHQ wire | 0.15 – 0.35 | 0.25 |
| Bboron addition for hardenability | 5×10⁻⁴ – 0 | 0 |
| P | ≤ 0.03 | |
| Smax (0.050 in some bar specs) | ≤ 0.04 | |
| Fe | balance |
10B38 Q&T 40-45 HRC — frequently asked
What is 10B38 Q&T 40-45 HRC used for?
10B38 Q&T 40-45 HRC is typically used for fasteners, bolts and threaded studs. In short: boron cold-heading wire.
What is the yield strength of 10B38 Q&T 40-45 HRC?
10B38 Q&T 40-45 HRC has a typical yield strength of 1,180 MPa (171 ksi) and a tensile strength of 1,350 MPa (196 ksi) — stronger than 94% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 10B38 Q&T 40-45 HRC easy to machine?
Not especially — machinability is rated poor (30/100, worse than 89% of steel grades). Machines like 1038 (≈60% of 1212); best in normalized or Q&T-to-~30 HRC condition, use rigid setups and carbide at moderate speed — boron slightly raises tool wear.
Can 10B38 Q&T 40-45 HRC be welded?
Not readily — weldability is rated poor (25/100). Weldable by SMAW/GMAW/resistance methods but 0.39% C plus boron gives high hardenability: preheat 150–250 °C, low-hydrogen consumables and post-weld temper to avoid HAZ cracking.
What surface finishes work on 10B38 Q&T 40-45 HRC?
No inherent corrosion resistance — use zinc or zinc-nickel electroplate (bake to relieve hydrogen at >32 HRC), hot-dip galvanizing, phosphate+oil, or zinc-flake coatings; polishes to a fair finish only.
Can 10B38 Q&T 40-45 HRC be formed, bent or molded?
In spheroidize-annealed CHQ wire it cold-heads and thread-rolls readily; hot forge 1100–1250 °C, then normalize before quench-hardening for consistent boron effect.
What is the maximum service temperature of 10B38 Q&T 40-45 HRC?
10B38 Q&T 40-45 HRC 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 10B38-HR and 10B38-CR?
HR is the default condition — default stock form for wire rod and bar destined for cold heading or subsequent Q&T. CR: pick for close tolerance, smooth surface and higher as-supplied strength when no further heat treatment is planned. Yield strength is 320 MPa in HR versus 540 MPa in CR.
Can FabDigit make parts in 10B38 Q&T 40-45 HRC?
Yes — 10B38 Q&T 40-45 HRC is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- SAE J403 — Chemical Compositions of SAE Carbon Steels — SAE International (2014)
- SAE J404 / J1268 — Hardenability of boron-treated carbon steels — SAE International (2013)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought, General Requirements — ASTM (2020)
- ISO 898-1 — Mechanical properties of fasteners, property classes 8.8/10.9 — ISO (2013)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Handbook Vol.16 — Machining — ASM International (1989)
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.