Steel 20B46 QT30-34
Hardness band · default condition
EN 20B46 · UNS G20461
QT30-34 = q&T 30–34 HRC
Most commonly stocked/ordered condition for boron-steel axles, shafts and tie rods.
Values for the QT30-34 condition
Other 20B46 tempers and conditions
20B46 is listed in 13 conditions; see the grade overview at 20B46.
Compare all 13 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition — pick for deep machining, cold heading or before a subsequent hardening cycle. | 375 | 620 | 25 | 179 HB | 48 W/m·K |
Hot rolled | Standard mill delivery form for bar that will be machined and heat treated by the user. | 420 | 720 | 20 | 207 HB | — |
Normalized | Uniform fine-grain structure for consistent machining and predictable response to later quenching. | 470 | 760 | 20 | 217 HB | — |
Cold drawn | Choose for close size tolerance, bright finish and higher as-supplied yield on parts used without heat treatment. | 670 | 790 | 12 | 229 HB | — |
Q&T 22–26 HRC | Toughest Q&T band — for shock-loaded links and shafts where impact energy outranks strength. | 700 | 840 | 20 | 24 HRC | — |
Q&T 28–32 HRC | General machine-shaft band with a good strength/toughness balance and still easy to machine. | 830 | 970 | 18 | 30 HRC | — |
QT30-34DefaultThis page Q&T 30–34 HRC | Most commonly stocked/ordered condition for boron-steel axles, shafts and tie rods. | 880 | 1,030 | 16 | 32 HRC | — |
Induction hardened | Use where a wear-resistant, compressively stressed skin is needed on a tough shaft (journals, splines, axle shafts). | 880 | 1,030 | 15 | 57 HRC | 7.5 % IACS |
Q&T 33–37 HRC | Higher-strength band for drive shafts and highly loaded links where machining is mostly finished. | 1,000 | 1,120 | 15 | 35 HRC | — |
Q&T 38–42 HRC | High-strength band for grade 8-class fasteners and wear-loaded pins; notch sensitivity rises noticeably. | 1,170 | 1,300 | 13 | 40 HRC | — |
Q&T 45–50 HRC | Wear-oriented low-temper band for plough shares, tines and cutting edges; low ductility, avoid impact-notched designs. | 1,400 | 1,580 | 10 | 48 HRC | — |
Hardened | Order the H version when the part is designed to a Jominy end-quench band rather than to as-delivered mechanical properties. | 1,500 | 1,900 | 8 | 55 HRC | 7.5 % IACS |
As-quenched | Intermediate process state only — maximum hardness but brittle; must be tempered before service. | 1,520 | 1,950 | 2 | 55 HRC | 7 % IACS |
What is 20B46 QT30-34?
20B46 QT30-34 is 20B46 heat treated to QT30-34 — most commonly stocked/ordered condition for boron-steel axles, shafts and tie rods. 20B46 QT30-34 has a yield strength of 880 MPa (128 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 89% of steel grades. Elongation at break is 16% and the elastic modulus is 205 GPa (29.7 Msi). 20B46 QT30-34 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).
Advantages
- High strength — 880 MPa (128 ksi), better than 89% of steel grades
20B46 QT30-34 properties
Typical room-temperature values for 20B46 QT30-34; 13 are specific to this condition. Other listed values are 20B46 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
20B46 QT30-34 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).
Mechanical16
20B46 QT30-34 has a yield strength of 880 MPa (128 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 89% of steel grades. Elongation at break is 16% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
20B46 QT30-34 is rated for continuous service to 400°C (752 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
20B46 QT30-34 conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 20B46 QT30-34 takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability6
20B46 QT30-34's machinability is fair (45/100, worse than 65% of steel grades); weldability poor (30/100); formability poor (30/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 20B46 QT30-34
Is 20B46 easy to machine?
Machine in the annealed/normalized or ≤32 HRC Q&T state with coated carbide, ~120–170 m/min; above 38 HRC switch to rigid setups, negative-rake carbide or CBN and expect much lower tool life.
Can 20B46 be welded?
Weldable only with care — CE ≈ 0.6–0.7 means 200–300 °C preheat, low-hydrogen consumables, controlled interpass and immediate stress relief/temper at 550–650 °C; the HAZ hardens fully because of the boron.
Can 20B46 be formed, bent or molded?
Hot forge at 1100–1200 °C and finish above 900 °C, then normalize; cold heading is practical only in the annealed spheroidized condition, and press-hardened stampings are quenched directly in the die.
What surface finishes work on 20B46?
Requires a coating — phosphate + oil, zinc or zinc-nickel plating, mechanical galvanizing or paint; bake at 200 °C within 4 h of electroplating parts above ~1000 MPa to avoid hydrogen embrittlement.
20B46 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 |
|---|---|---|
| Cmedium-carbon; sets attainable as-quenched hardness ~55 HRC | 0.44 – 0.49 | 0.46 |
| Mnsources differ slightly on the band; confirm against the mill certificate | 0.75 – 1 | 0.88 |
| Sideoxidation | 0.15 – 0.35 | 0.25 |
| P | ≤ 0.04 | — |
| Smax; resulphurised variants are ordered separately for machining | ≤ 0.04 | — |
| Beffective (acid-soluble) boron; requires Ti/Al to fix N | 5×10⁻⁴ – 0 | 0 |
| Fe | balance | — |
20B46 QT30-34 — frequently asked
What is 20B46 QT30-34 used for?
20B46 QT30-34 is typically used for axle shafts, structural bolts and gears. In short: cr-Mo hardenability, less alloy; boron-hardened shaft steel; Q&T to 50 HRC.
What is the yield strength of 20B46 QT30-34?
20B46 QT30-34 has a typical yield strength of 880 MPa (128 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 89% of steel grades. Strength varies by condition: see the 13 listed tempers.
Is 20B46 QT30-34 easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine in the annealed/normalized or ≤32 HRC Q&T state with coated carbide, ~120–170 m/min; above 38 HRC switch to rigid setups, negative-rake carbide or CBN and expect much lower tool life.
Can 20B46 QT30-34 be welded?
Not readily — weldability is rated poor (30/100). Weldable only with care — CE ≈ 0.6–0.7 means 200–300 °C preheat, low-hydrogen consumables, controlled interpass and immediate stress relief/temper at 550–650 °C; the HAZ hardens fully because of the boron.
What surface finishes work on 20B46 QT30-34?
Requires a coating — phosphate + oil, zinc or zinc-nickel plating, mechanical galvanizing or paint; bake at 200 °C within 4 h of electroplating parts above ~1000 MPa to avoid hydrogen embrittlement.
Can 20B46 QT30-34 be formed, bent or molded?
Hot forge at 1100–1200 °C and finish above 900 °C, then normalize; cold heading is practical only in the annealed spheroidized condition, and press-hardened stampings are quenched directly in the die.
What is the maximum service temperature of 20B46 QT30-34?
20B46 QT30-34 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 20B46 QT30-34 and 20B46-AQ?
QT30-34 is the default condition — most commonly stocked/ordered condition for boron-steel axles, shafts and tie rods. AQ: intermediate process state only — maximum hardness but brittle; must be tempered before service. Yield strength is 880 MPa in QT30-34 versus 1,520 MPa in AQ.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- SAE J1268 — Hardenability Bands for Carbon and Alloy H Steels — SAE International (2019)
- ASTM A29/A29M — General Requirements for Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM International (2020)
- ASTM A370 / E140 — Mechanical Testing and Hardness Conversions for Steel — ASTM International (2021)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating (boron hardenability, tempering response) — ASM International (1991)
- Machinery's Handbook (machinability ratings, Q&T bar data) — Industrial Press (2020)
- UNS G20461 alloy record — SAE/ASTM Unified Numbering System (2017)
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.