Steel 1055-QT205
Heat-treated state
AISI/SAE 1055 · UNS G10550
QT205 = q&T 205 °C
Maximum wear resistance for knives, chisels and cutting edges in thin sections.
Values for the QT205 condition
Other 1055 tempers and conditions
1055 is listed in 11 conditions; see the grade overview at 1055.
Compare all 11 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Use when severe cold heading, bending or deep drawing of the 0.55 % C steel is required. | 320 | 590 | 28 | 174 HB | 9.8 % IACS |
Solution annealed | Softest condition for heavy machining or cold forming before hardening. | 330 | 640 | 23 | 187 HB | — |
HRDefault Hot rolled | Standard as-rolled bar/plate/coil for parts that will be machined and then heat treated. | 370 | 660 | 12 | 192 HB | — |
Normalized | Refines grain and homogenizes forgings/hot-rolled stock before machining or hardening. | 420 | 725 | 19 | 217 HB | — |
Cold drawn | Pick for close-tolerance, bright, straight bar with higher yield strength and better surface finish than hot rolled. | 565 | 660 | 11 | 197 HB | — |
Q&T 540 °C | General quenched-and-tempered structural condition where toughness outweighs hardness. | 630 | 820 | 19 | 24 HRC | — |
Q&T 425 °C | Spring-temper style balance of strength and toughness for leaf springs and shafts. | 740 | 965 | 15 | 37 HRC | — |
Q&T 315 °C | High hardness with a little more toughness — hand tools, wear plates, cutters. | 800 | 1,090 | 11 | 46 HRC | — |
QT205This page Q&T 205 °C | Maximum wear resistance for knives, chisels and cutting edges in thin sections. | 880 | 1,240 | 8 | 52 HRC | 46 W/m·K |
Hardened and blue tempered spring strip | Ready-to-use spring temper coil/strip for flat springs, clips, saw blades and shim stock. | 1,300 | 1,500 | 3 | 46 HRC | — |
As-quenched | Intermediate condition only — maximum hardness but brittle and crack-prone; temper immediately. | 1,600 | 2,000 | 1 | 63 HRC | 7.5 % IACS |
What is 1055-QT205?
1055-QT205 is 1055 heat treated to QT205 — maximum wear resistance for knives, chisels and cutting edges in thin sections. 1055-QT205 has a yield strength of 880 MPa (128 ksi) and a tensile strength of 1,240 MPa (180 ksi) — stronger than 89% of steel grades. Elongation at break is 8% and the elastic modulus is 205 GPa (29.7 Msi). 1055-QT205 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). HR is the default condition FabDigit quotes; QT205 is available on request or by drawing note.
Advantages
- High strength — 880 MPa (128 ksi), better than 89% of steel grades
- High electrical conductivity — 9.5 % IACS, better than 75% of steel grades
Limitations
- Limited service temperature — 150°C (302 °F), worse than 99% of steel grades
- Difficult to weld — 10/100, worse than 99% of steel grades
- Difficult to machine — 15/100, worse than 98% of steel grades
- Low fracture toughness — 30 MPa·√m (27.3 ksi·√in), worse than 96% of steel grades
- Limited ductility — 8%, worse than 95% of steel grades
1055-QT205 properties
Typical room-temperature values for 1055-QT205; 15 are specific to this condition. Other listed values are 1055 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
1055-QT205 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
1055-QT205 has a yield strength of 880 MPa (128 ksi) and a tensile strength of 1,240 MPa (180 ksi) — stronger than 89% of steel grades. Elongation at break is 8% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
1055-QT205 is rated for continuous service to 150°C (302 °F). It conducts heat at 46 W/m·K (26.6 BTU/hr·ft·°F), better than 71% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
1055-QT205 conducts electricity at 9.5 % IACS, better than 75% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 1055-QT205 takes about 26 MJ of energy and emits 2 kg of CO₂ — less than 64% of steel grades. Typical recycled content is 30%.
Manufacturability8
1055-QT205's machinability is poor (15/100, worse than 98% of steel grades); weldability not recommended (10/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 1055-QT205
Is 1055 easy to machine?
Machine in the annealed/spheroidized or hot-rolled state at ~55 % of 1212 speed with rigid setups and carbide tooling; hardened parts above 45 HRC need grinding.
Can 1055 be welded?
Poor weldability at 0.55 % C — use low-hydrogen consumables, 200–300 °C preheat, interpass control and immediate post-weld temper; avoid welding on hardened parts.
Can 1055 be formed, bent or molded?
Cold form only from annealed/spheroidized stock with generous bend radii; otherwise hot form at 850–1100 °C and normalize afterwards.
What surface finishes work on 1055?
No corrosion resistance bare — protect with black oxide, phosphate + oil, zinc plating (bake to avoid hydrogen embrittlement above 40 HRC) or paint; polishes well when hardened.
1055 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 / ASTM A29 heat analysis | 0.5 – 0.6 | 0.55 |
| Mn | 0.6 – 0.9 | 0.75 |
| Sitypical for killed bar; not specified for all product forms | 0.15 – 0.35 | 0.25 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.05 | 0.03 |
| Fe | balance | — |
1055-QT205 — frequently asked
What is 1055-QT205 used for?
1055-QT205 is typically used for hand tools, blades, springs, agricultural parts and wear plates. In short: spring and blade carbon steel; harder than 1045; low weldability rating.
What is the yield strength of 1055-QT205?
1055-QT205 has a typical yield strength of 880 MPa (128 ksi) and a tensile strength of 1,240 MPa (180 ksi) — stronger than 89% of steel grades. Strength varies by condition: see the 11 listed tempers.
Is 1055-QT205 easy to machine?
Not especially — machinability is rated poor (15/100, worse than 98% of steel grades). Machine in the annealed/spheroidized or hot-rolled state at ~55 % of 1212 speed with rigid setups and carbide tooling; hardened parts above 45 HRC need grinding.
Can 1055-QT205 be welded?
Not readily — weldability is rated not recommended (10/100). Poor weldability at 0.55 % C — use low-hydrogen consumables, 200–300 °C preheat, interpass control and immediate post-weld temper; avoid welding on hardened parts.
What surface finishes work on 1055-QT205?
No corrosion resistance bare — protect with black oxide, phosphate + oil, zinc plating (bake to avoid hydrogen embrittlement above 40 HRC) or paint; polishes well when hardened.
Can 1055-QT205 be formed, bent or molded?
Cold form only from annealed/spheroidized stock with generous bend radii; otherwise hot form at 850–1100 °C and normalize afterwards.
What is the maximum service temperature of 1055-QT205?
1055-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 1055-HR and 1055-AQ?
HR is the default condition — standard as-rolled bar/plate/coil for parts that will be machined and then heat treated. AQ: intermediate condition only — maximum hardness but brittle and crack-prone; temper immediately. Yield strength is 370 MPa in HR versus 1,600 MPa in AQ.
Sources
- SAE J403 – Chemical Compositions of SAE Carbon Steels — SAE International (2014)
- ASTM A29/A29M – Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- ASTM A682/A682M – Steel, Strip, High-Carbon, Cold-Rolled, Spring Quality — ASTM (2018)
- 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)
- EN 10083-2 / DIN 17200 – C55 (1.0535) — CEN (2006)
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.