Steel 10B38
EN 10B38 · UNS G10381
10B38 is a boron-treated medium-carbon steel: 1038 with about 0.0005–0.003% B, which sharply raises hardenability while leaving annealed hardness and cold formability nearly unchanged.
Values for the HR condition
10B38 tempers and conditions
10B38 is supplied in 8 conditions, soft to hard. HR 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 |
|---|---|---|---|---|---|---|
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 | — |
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?
10B38 is a boron-treated medium-carbon steel: 1038 with about 0.0005–0.003% B, which sharply raises hardenability while leaving annealed hardness and cold formability nearly unchanged. It is chosen for parts that are cold-headed and then quenched and tempered — property class 8.8/10.9 bolts, nuts, studs and pins — and is supplied as spheroidize-annealed CHQ wire plus hot-rolled and cold-drawn bar. Limits are no corrosion resistance (zinc or zinc-flake coating required), preheat needed for welding, and hardenability that is sensitive to boron level and rolling/normalizing practice. 10B38 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). 10B38 has a yield strength of 320 MPa (46.4 ksi) and a tensile strength of 570 MPa (82.7 ksi) — weaker than 81% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
What is 10B38 used for?
- Fasteners
- Bolts
- Threaded studs
Advantages
- Conducts heat well — 49 W/m·K (28.3 BTU/hr·ft·°F), better than 83% of steel grades
- High electrical conductivity — 10 % IACS, better than 83% of steel grades
Limitations
- Low strength — 320 MPa (46.4 ksi), worse than 81% of steel grades
10B38 properties
Typical room-temperature values for 10B38-HR; bars are the position among steel grades.
Physical3
10B38 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 has a yield strength of 320 MPa (46.4 ksi) and a tensile strength of 570 MPa (82.7 ksi) — weaker than 81% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
10B38 is rated for continuous service to 400°C (752 °F). It conducts heat at 49 W/m·K (28.3 BTU/hr·ft·°F), better than 83% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
10B38 conducts electricity at 10 % IACS, better than 83% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 10B38 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's machinability is good (58/100, better than 75% of steel grades); weldability good (55/100); formability good (60/100).
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. 10B38 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 10B38
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.
Manufacturability
The process limits FabDigit applies to 10B38. Every 10B38 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Better58 / 100 |
|---|---|
| ISO material group | P.1 |
| Cutting speed (rough / finish) | 220 / 260 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 5× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Better60 / 100 |
|---|---|
| Weldability | Better55 / 100 |
| Bendable | Yes |
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 |
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.
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).
Plating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel 10B38 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- G10381
How much does 10B38 cost?
10B38 is a standard-cost steel ($$), cheaper than about 71% 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.
10B38 — frequently asked
What is 10B38 used for?
10B38 is typically used for fasteners, bolts and threaded studs. In short: boron cold-heading wire.
What is the yield strength of 10B38?
10B38 has a typical yield strength of 320 MPa (46.4 ksi) and a tensile strength of 570 MPa (82.7 ksi) — weaker than 81% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 10B38 easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% 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 be welded?
Yes — weldability is rated good (55/100). 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?
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 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?
10B38 is rated for continuous use to about 400°C (752 °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.
How much does 10B38 cost?
10B38 is a standard-cost steel ($$), cheaper than about 71% 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.
Can FabDigit make parts in 10B38?
Yes — 10B38 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; 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.