Steel 4047-QT205
Heat-treated state
AISI/SAE 4047 · UNS G40470
QT205 = q&T 205 °C
Maximum hardness/wear condition for small sections; very low toughness, avoid where impact or notches exist.
Values for the QT205 condition
Other 4047 tempers and conditions
4047 is listed in 11 conditions; see the grade overview at 4047.
Compare all 11 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Pick for cold-headed fastener blanks where maximum ductility at this carbon level is needed. | 360 | 570 | 26 | 170 HB | 8 % IACS |
ADefault Solution annealed | Choose for rough machining, cold sawing and stock that will be heat treated after fabrication. | 400 | 620 | 22 | 185 HB | — |
Hot rolled | Cheapest mill condition for stock that will be normalized or quenched and tempered later. | 430 | 730 | 19 | 17 HRC | 7.8 % IACS |
Normalized | Use to refine grain and homogenize forgings before hardening, or as a moderate-strength as-supplied condition. | 510 | 810 | 19 | 21 HRC | 7.8 % IACS |
Cold drawn | Choose for close-tolerance bright bar with higher yield strength and better surface finish than hot rolled. | 650 | 760 | 12 | 19 HRC | 7.8 % IACS |
Q&T 650 °C | Softest Q&T condition — pick when toughness, machinability or sour-service hardness caps (<22–25 HRC) matter more than strength. | 740 | 860 | 22 | 24 HRC | — |
Induction hardened & tempered surface | Use when a wear-resistant 55+ HRC case with a tough core is needed on shafts, pins or gear journals. | 900 | 1,050 | 14 | 56 HRC | 7.2 % IACS |
Q&T 540 °C | General-purpose quenched-and-tempered condition: good strength with usable toughness and machinability. | 950 | 1,050 | 18 | 33 HRC | — |
Q&T 425 °C | Balanced high-strength condition for shafts, studs and Grade 8-class fasteners. | 1,170 | 1,290 | 14 | 41 HRC | — |
Q&T 315 °C | High-hardness spring/tool-like condition; keep out of the 260–370 °C blue-brittleness zone for impact-loaded parts. | 1,330 | 1,580 | 11 | 47 HRC | — |
QT205This page Q&T 205 °C | Maximum hardness/wear condition for small sections; very low toughness, avoid where impact or notches exist. | 1,450 | 1,830 | 9 | 51 HRC | — |
What is 4047-QT205?
4047-QT205 is 4047 heat treated to QT205 — maximum hardness/wear condition for small sections; very low toughness, avoid where impact or notches exist. 4047-QT205 has a yield strength of 1,450 MPa (210 ksi) and a tensile strength of 1,830 MPa (265 ksi) — stronger than 97% of steel grades. Elongation at break is 9% and the elastic modulus is 205 GPa (29.7 Msi). 4047-QT205 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). A is the default condition FabDigit quotes; QT205 is available on request or by drawing note.
Advantages
- High strength — 1,450 MPa (210 ksi), better than 97% of steel grades
Limitations
- Limited service temperature — 150°C (302 °F), worse than 99% of steel grades
- Difficult to machine — 18/100, worse than 97% of steel grades
- Difficult to weld — 12/100, worse than 96% of steel grades
- Low fracture toughness — 35 MPa·√m (31.9 ksi·√in), worse than 94% of steel grades
- Limited ductility — 9%, worse than 93% of steel grades
4047-QT205 properties
Typical room-temperature values for 4047-QT205; 15 are specific to this condition. Other listed values are 4047 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
4047-QT205 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
4047-QT205 has a yield strength of 1,450 MPa (210 ksi) and a tensile strength of 1,830 MPa (265 ksi) — stronger than 97% of steel grades. Elongation at break is 9% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4047-QT205 is rated for continuous service to 150°C (302 °F). It conducts heat at 43 W/m·K (24.8 BTU/hr·ft·°F), better than 51% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
4047-QT205 conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of 4047-QT205 takes about 29 MJ of energy and emits 2 kg of CO₂ — less than 53% of steel grades. Typical recycled content is 30%.
Manufacturability6
4047-QT205's machinability is poor (18/100, worse than 97% of steel grades); weldability not recommended (12/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 4047-QT205
Is 4047 easy to machine?
Machine in the annealed or ≤32 HRC condition with carbide tooling and rigid setups; above 40 HRC switch to CBN/ceramic or grind, and expect roughly half the tool life of 1045.
Can 4047 be welded?
Difficult — CE ≈ 0.65–0.70; preheat 300–400 °C, use low-hydrogen consumables, keep interpass temperature and temper immediately after welding to avoid hydrogen and quench cracking.
Can 4047 be formed, bent or molded?
Cold form only in the spheroidize-annealed condition (upsetting of fastener blanks); otherwise hot forge at 1050–1200 °C and normalize afterwards.
What surface finishes work on 4047?
No corrosion resistance of its own: use black oxide, phosphate + oil, zinc/zinc-nickel plating (bake at 190–200 °C within 4 h if above ~1000 MPa) or paint; hardened surfaces polish and hard-chrome plate well.
4047 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 |
|---|---|---|
| Chighest carbon of the 40xx series | 0.45 – 0.5 | 0.47 |
| Mn | 0.7 – 0.9 | 0.8 |
| Sifor fine-grain killed steel | 0.15 – 0.35 | 0.25 |
| Mohardenability + temper-embrittlement resistance | 0.2 – 0.3 | 0.25 |
| P | ≤ 0.04 | — |
| Smax (H-grades / resulfurized variants differ) | ≤ 0.04 | — |
| Fe | balance | — |
4047-QT205 — frequently asked
What is 4047-QT205 used for?
4047-QT205 is typically used for high-strength bolts, springs and fasteners. In short: highest-carbon 40xx grade; fastener-oriented alloy steel; difficult to weld.
What is the yield strength of 4047-QT205?
4047-QT205 has a typical yield strength of 1,450 MPa (210 ksi) and a tensile strength of 1,830 MPa (265 ksi) — stronger than 97% of steel grades. Strength varies by condition: see the 11 listed tempers.
Is 4047-QT205 easy to machine?
Not especially — machinability is rated poor (18/100, worse than 97% of steel grades). Machine in the annealed or ≤32 HRC condition with carbide tooling and rigid setups; above 40 HRC switch to CBN/ceramic or grind, and expect roughly half the tool life of 1045.
Can 4047-QT205 be welded?
Not readily — weldability is rated not recommended (12/100). Difficult — CE ≈ 0.65–0.70; preheat 300–400 °C, use low-hydrogen consumables, keep interpass temperature and temper immediately after welding to avoid hydrogen and quench cracking.
What surface finishes work on 4047-QT205?
No corrosion resistance of its own: use black oxide, phosphate + oil, zinc/zinc-nickel plating (bake at 190–200 °C within 4 h if above ~1000 MPa) or paint; hardened surfaces polish and hard-chrome plate well.
Can 4047-QT205 be formed, bent or molded?
Cold form only in the spheroidize-annealed condition (upsetting of fastener blanks); otherwise hot forge at 1050–1200 °C and normalize afterwards.
What is the maximum service temperature of 4047-QT205?
4047-QT205 is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 4047-A and 4047-QT205?
A is the default condition — choose for rough machining, cold sawing and stock that will be heat treated after fabrication. QT205: maximum hardness/wear condition for small sections; very low toughness, avoid where impact or notches exist. Yield strength is 400 MPa in A versus 1,450 MPa in QT205.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- ASTM A29/A29M — General Requirements for Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM International (2020)
- SAE J1268 — Hardenability Bands for Carbon and Alloy H Steels — SAE International (2019)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating — ASM International (1991)
- Machinery's Handbook, 31st ed. — Industrial Press (2020)
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.