10B21 (SAE J403) is a low-carbon steel with 0.18–0.23% carbon, 0.60–0.90% manganese and a small boron addition of 0.0005–0.003%. The boron raises hardenability, so a cold-forged part can be quenched and tempered to Class 8.8 or 10.9 strength from a low-carbon, easily cold-headed steel. Typical uses are bolts, screws, structural bolts, automotive fasteners and self-tapping screws.
OneKaizen supplies 10B21 as wire rods (Ø 5.5–40 mm), bright wires (Ø 1.5–37 mm), rolled round bars (Ø 16–500 mm) and bright bars (round Ø 8–160 mm), sourced from Indian and international mills. Delivery condition is hot rolled wire rod, spheroidise annealed (cold-heading quality), drawn or hot rolled bars. Every consignment ships with a mill test certificate.
EQUIVALENT GRADES
10B21 Equivalents
Direct means the same grade under another name. Close means the same alloy concept with slightly different limits, commonly substituted. Approximate means similar use with real differences: check with us before substituting.
| Standard | Designation | Match |
|---|---|---|
| AISI/SAE | 10B21 | Direct |
| UNS | G10211 | Direct |
| JIS | SWRCHB223 | Approximate |
| KS | SWRCHB223 | Approximate |
10B21 Chemical Composition
Per SAE J403 (SAE 10B21) - C, Mn, B per totalmateria summary; P/S per base grade
| Element | Range, wt % | Range chart |
|---|---|---|
| C | 0.18 – 0.23 | |
| Mn | 0.6 – 0.9 | |
| B | 0.0005 – 0.003 |
Delivery Condition and Heat Treatment
10B21 is bought for cold heading and cold forging, so it is usually supplied hot rolled or spheroidise annealed. Spheroidise annealing softens the steel and lets it be cold headed without cracking.
After forming, the fasteners are hardened and tempered. Boron gives the steel enough hardenability to reach Class 8.8 and 10.9 properties. The tempering temperature sets the final strength.
Boron is easily lost in melting, so the level and its control matter for consistent hardening. Ask for a mill test certificate that shows the boron content. Welding is not the usual route for this grade.
What We Supply 10B21 In
Where 10B21 Is Used
Industries: Fasteners, Automotive, Construction hardware, Agricultural equipment, Cold forging
Compare 10B21 with Similar Grades
10B21 Questions
Is 10B21 the same as SWRCHB223?
No. JIS SWRCHB223 is only an approximate match. There is no exact EN equivalent; EN 10263-4 boron grades such as 20B2 are comparable. Tell us if your specification names a particular standard.
What is the difference between 10B21 and SAE 1018?
SAE 1018 has similar carbon but no boron, so it has lower hardenability. 10B21 hardens through in fastener sizes and reaches Class 8.8 and 10.9 after quench and temper.
What is the difference between 10B21 and 10B33 or 10B35?
10B33 and 10B35 have higher carbon, so they reach higher strength. 10B21 is easier to cold head and is the usual choice for Class 8.8 and 10.9 fasteners.
How is 10B21 heat treated?
It is cold headed or cold forged from spheroidise annealed wire, then quenched and tempered to the fastener class. Boron gives the hardenability.
What is 10B21 used for?
Class 8.8 and 10.9 bolts and screws, cold-forged fasteners, structural bolts, automotive fasteners and self-tapping screws.
What is the minimum order for 10B21?
3 tonnes, flexible depending on size and your situation. Send us your size, condition and quantity and we confirm availability and delivery.
What is 10B21 equivalent to?
10B21 is the same grade as AISI/SAE 10B21, UNS G10211.
In which forms do you supply 10B21?
OneKaizen supplies 10B21 as Wire Rods, Bright Wires, Round Bars, Bright Bars, delivered across India and exported to buyers abroad.
Do you supply 10B21 with a mill test certificate?
Yes. Every lot ships with an EN 10204 3.1 mill test certificate showing chemistry and mechanical properties, traceable to the heat number.
Data compiled by the OneKaizen metallurgy team from the standards named above. Updated 27 October 2026. Equivalents are nearest matches; confirm critical substitutions against the governing standard and mill certificate.