Steel 10B21 · supply condition · default condition
Steel 10B21-HR
Properties of the HR condition, compared with the other 10B21 tempers.
Standard mill supply form for wire rod and bar destined for drawing, cold heading or heat treatment.
What is 10B21-HR?
10B21-HR is 10B21 supplied in the HR condition — standard mill supply form for wire rod and bar destined for drawing, cold heading or heat treatment. 10B21-HR has a yield strength of 290 MPa (42.1 ksi) and a tensile strength of 430 MPa (62.4 ksi) — weaker than 88% of steel grades. Elongation at break is 30% and the elastic modulus is 205 GPa (29.7 Msi). 10B21-HR has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,465°C (2,669 °F).
Advantages
- Conducts heat well — 51.9 W/m·K (30 BTU/hr·ft·°F), better than 96% of steel grades
- High electrical conductivity — 10.8 % IACS, better than 94% of steel grades
- Forms and bends easily — 82/100, better than 94% of steel grades
- Ductile — tolerates forming and impact — 30%, better than 92% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
Limitations
- Low strength — 290 MPa (42.1 ksi), worse than 88% of steel grades
- Hard to polish — 45/100, worse than 84% of steel grades
10B21-HR properties
Typical room-temperature values for 10B21-HR — 14 properties are specific to this condition; the rest are grade-level values shared by every 10B21 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
10B21-HR has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,465°C (2,669 °F).
Mechanical14
10B21-HR has a yield strength of 290 MPa (42.1 ksi) and a tensile strength of 430 MPa (62.4 ksi) — weaker than 88% of steel grades. Elongation at break is 30% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
10B21-HR is rated for continuous service to 400°C (752 °F). It conducts heat at 51.9 W/m·K (30 BTU/hr·ft·°F), better than 96% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
10B21-HR conducts electricity at 10.8 % IACS, better than 94% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 87% of steel grades.
Sustainability4
Producing a kilogram of 10B21-HR takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
10B21-HR's machinability is good (62/100, better than 89% of steel grades); weldability excellent (85/100); formability very good (82/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 10B21 tempers and conditions
10B21 is also supplied in 8 other conditions. The full side-by-side table is on the 10B21 overview.
- HRDefaultStandard mill supply form for wire rod and bar destined for drawing, cold heading or heat treatment.290 MPa yield · 126 HB
- QT-3239Highest common strength level for 10B21 fasteners; mind hydrogen embrittlement and delayed fracture risk above ~ 34 HRC when electroplated.990 MPa yield · 35 HRC
- QT-2832Narrow-band Q&T ordered when a tight hardness window is specified for threaded parts or self-tapping screw cores.810 MPa yield · 30 HRC
- QT-2534Standard fastener condition for class 8.8 / SAE Grade 5 bolts up to about M16 where boron gives full through-hardening.760 MPa yield · 30 HRC
- CarburizedUsed for self-drilling/self-tapping screws and case-hardened bolts needing a hard thread-forming surface over a ductile core.620 MPa yield · 57 HRC
- CRPick for close size tolerance, bright finish and higher as-supplied strength when no further heat treatment is planned.470 MPa yield · 163 HB
- NormalizedUse to refine grain and homogenize after hot working, giving uniform strength and good toughness prior to hardening.320 MPa yield · 135 HB
- SAThe condition wire is actually shipped in for multi-station cold heading of bolts and screws — lowest work-hardening, best die life.260 MPa yield · 110 HB
- AnnealedChoose for maximum ductility before severe cold forming or for stress-free machining of preforms.250 MPa yield · 111 HB
Working with 10B21-HR
Is 10B21 easy to machine?
Machines like plain 1020 — soft and gummy, so use sharp positive-rake tools, high speed and generous coolant; hardened Q&T 32–39 HRC states cut best with coated carbide at reduced feed.
Can 10B21 be welded?
Readily weldable by MIG/TIG/resistance (CE ≈ 0.35); no preheat needed below ~25 mm, but welding after quench-and-temper destroys the fastener strength locally.
Can 10B21 be formed, bent or molded?
Excellent cold headability in the spheroidize-annealed CHQ condition — designed for multi-station bolt heading and thread rolling; hot forge 1100–1200 °C.
What surface finishes work on 10B21?
Not anodizable; standard finishes are zinc or zinc-nickel electroplating, hot-dip galvanizing, zinc-flake (Dacromet/Geomet) and phosphate + oil — bake plated parts above 32 HRC to prevent hydrogen embrittlement.
10B21 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 boron steel | 0.18 – 0.23 | 0.2 |
| Mn | 0.6 – 0.9 | 0.75 |
| Sinot specified in J403 for bar; typical for killed CHQ wire | 0.15 – 0.35 | 0.25 |
| P | ≤ 0.03 | 0.02 |
| Smax; fastener quality often ≤0.035 | ≤ 0.05 | 0.02 |
| Bhardenability agent; requires Ti/Al to fix N | 5×10⁻⁴ – 0 | 0 |
| Tiproducer addition to protect boron from nitrogen | ≤ 0.05 | 0.03 |
| Fe | balance | — |
10B21-HR — frequently asked
What is 10B21-HR used for?
10B21-HR is typically used for fasteners, bolts and studs. In short: hot-stamping boron steel.
What is the yield strength of 10B21-HR?
10B21-HR has a typical yield strength of 290 MPa (42.1 ksi) and a tensile strength of 430 MPa (62.4 ksi) — weaker than 88% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 10B21-HR easy to machine?
Reasonably — machinability is rated good (62/100, better than 89% of steel grades). Machines like plain 1020 — soft and gummy, so use sharp positive-rake tools, high speed and generous coolant; hardened Q&T 32–39 HRC states cut best with coated carbide at reduced feed.
Can 10B21-HR be welded?
Yes — weldability is rated excellent (85/100). Readily weldable by MIG/TIG/resistance (CE ≈ 0.35); no preheat needed below ~25 mm, but welding after quench-and-temper destroys the fastener strength locally.
What surface finishes work on 10B21-HR?
Not anodizable; standard finishes are zinc or zinc-nickel electroplating, hot-dip galvanizing, zinc-flake (Dacromet/Geomet) and phosphate + oil — bake plated parts above 32 HRC to prevent hydrogen embrittlement.
Can 10B21-HR be formed, bent or molded?
Excellent cold headability in the spheroidize-annealed CHQ condition — designed for multi-station bolt heading and thread rolling; hot forge 1100–1200 °C.
What is the maximum service temperature of 10B21-HR?
10B21-HR 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 10B21-HR and 10B21 QT-3239?
HR is the default condition — standard mill supply form for wire rod and bar destined for drawing, cold heading or heat treatment. QT-3239: highest common strength level for 10B21 fasteners; mind hydrogen embrittlement and delayed fracture risk above ~ 34 HRC when electroplated. Yield strength is 290 MPa in HR versus 990 MPa in QT-3239.
Can FabDigit make parts in 10B21-HR?
Yes — 10B21-HR is available for CNC machining and sheet metal with instant online pricing. 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 J1268 — Hardenability Bands for Carbon and Alloy H Steels — SAE International (2019)
- SAE J429 — Mechanical and Material Requirements for Externally Threaded Fasteners — SAE International (2014)
- ISO 898-1 — Mechanical properties of fasteners, carbon and alloy steel bolts, screws and studs — ISO (2013)
- ASTM A510 / A29 — General requirements for wire rods and carbon steel bars — ASTM (2018)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol. 4A — Steel Heat Treating Fundamentals (boron hardenability) — ASM International (2013)
- GB/T 6478 / GB/T 5953 — (10B21 equivalent grades) — 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.