Stainless Steel 420C +QT650
Heat-treated state
AISI/SAE 420C · UNS S42000 · EN 1.4034, X46Cr13 · GB 4Cr13
+QT650 = quenched and tempered, 650–850 MPa class
High-temperature-tempered condition for shafts and structural parts needing ductility rather than wear resistance.
Values for the +QT650 condition
Other 420C tempers and conditions
420C is listed in 7 conditions; see the grade overview at 420C.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
+ADefault Annealed | Stock condition for machining, blanking and subsequent hardening; lowest hardness and best machinability. | 460 | 760 | 17 | 20 HRC | — |
+QT650This page Quenched and tempered, 650–850 MPa class | High-temperature-tempered condition for shafts and structural parts needing ductility rather than wear resistance. | 500 | 750 | 14 | 21 HRC | 3.1 % IACS |
Cold drawn, annealed bar/wire | Choose for close-tolerance bright bar or wire that will be machined and then hardened. | 650 | 860 | 10 | 25 HRC | 3.1 % IACS |
Quenched and tempered, 800–1000 MPa class | Medium-strength Q&T condition where some impact toughness must be retained alongside higher strength. | 650 | 900 | 11 | 28 HRC | 3.1 % IACS |
hardened and tempered (moderate hardness) | Best hardness/toughness compromise for shear blades, valve components and moulds. | 1,300 | 1,550 | 6 | 48 HRC | — |
hardened and low-temperature tempered | Standard cutlery/surgical-blade condition: maximum wear resistance and edge retention with acceptable corrosion resistance. | 1,550 | 1,800 | 3 | 54 HRC | — |
Hardened | As-quenched martensite for maximum hardness; must normally be tempered/stress-relieved before service to avoid cracking. | 1,600 | 1,950 | 1 | 57 HRC | 2.5 % IACS |
What is 420C +QT650?
420C +QT650 is 420C heat treated to +QT650 — high-temperature-tempered condition for shafts and structural parts needing ductility rather than wear resistance. 420C +QT650 has a yield strength of 500 MPa (72.5 ksi) and a tensile strength of 750 MPa (109 ksi) — stronger than 77% of stainless steel grades. Elongation at break is 14% and the elastic modulus is 215 GPa (31.2 Msi). 420C +QT650 has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 83% of stainless steel grades. It melts at 1,425°C (2,597 °F). +A is the default condition FabDigit quotes; +QT650 is available on request or by drawing note.
Advantages
- Conducts heat well — 30 W/m·K (17.3 BTU/hr·ft·°F), better than 99% of stainless steel grades
- High electrical conductivity — 3.1 % IACS, better than 99% of stainless steel grades
- Low embodied carbon — 3.4 kg CO₂/kg, better than 91% of stainless steel grades
- High strength — 500 MPa (72.5 ksi), better than 77% of stainless steel grades
Limitations
- Difficult to weld — 20/100, worse than 95% of stainless steel grades
- Limited ductility — 14%, worse than 91% of stainless steel grades
- Low fracture toughness — 60 MPa·√m (54.6 ksi·√in), worse than 88% of stainless steel grades
- Needs corrosion protection — 46/100, worse than 82% of stainless steel grades
- Limited service temperature — 400°C (752 °F), worse than 78% of stainless steel grades
420C +QT650 properties
Typical room-temperature values for 420C +QT650; 23 are specific to this condition. Other listed values are 420C reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
420C +QT650 has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 83% of stainless steel grades. It melts at 1,425°C (2,597 °F).
Mechanical17
420C +QT650 has a yield strength of 500 MPa (72.5 ksi) and a tensile strength of 750 MPa (109 ksi) — stronger than 77% of stainless steel grades. Elongation at break is 14% and the elastic modulus is 215 GPa (31.2 Msi).
Thermal6
420C +QT650 is rated for continuous service to 400°C (752 °F). It conducts heat at 30 W/m·K (17.3 BTU/hr·ft·°F), better than 99% of stainless steel grades. Thermal expansion is 10.5 µm/m·K (5.83 µin/in·°F).
Electrical3
420C +QT650 conducts electricity at 3.1 % IACS, better than 99% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (46/100), worse than 82% of stainless steel grades.
Sustainability4
Producing a kilogram of 420C +QT650 takes about 50 MJ of energy and emits 3.4 kg of CO₂ — less than 80% of stainless steel grades. Typical recycled content is 45%.
Manufacturability8
420C +QT650's machinability is fair (42/100, better than 79% of stainless steel grades); weldability poor (20/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 420C +QT650
Is 420C easy to machine?
Machine in the annealed condition with sharp, rigid carbide or HSS-Co tooling, moderate speed and heavy flood coolant; above ~45 HRC switch to CBN/ceramic turning or grinding/EDM.
Can 420C be welded?
Poor weldability — high carbon promotes hard, crack-prone martensite; if unavoidable, preheat 200–300 °C, use 410NiMo/309 filler, and temper immediately after welding.
Can 420C be formed, bent or molded?
Only light cold forming and blanking in the annealed state (generous bend radii, R ≥ 2t); hot work 1100–850 °C followed by slow cooling and full anneal to avoid quench cracks.
What surface finishes work on 420C?
Takes a mirror polish; harden, temper and then passivate (ASTM A967 nitric/citric) for best corrosion resistance — hard chrome, nitriding or PVD coatings are common for wear parts.
420C 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 |
|---|---|---|
| CGB/T 1220 4Cr13 typically 0.36–0.45 %C | 0.43 – 0.5 | 0.46 |
| Si | ≤ 1 | 0.4 |
| Mn | ≤ 1 | 0.5 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.03 | 0.01 |
| Cr | 12.5 – 14.5 | 13.5 |
| Niresidual, not specified in all standards | ≤ 0.5 | 0.2 |
| Moresidual | ≤ 0.3 | |
| Fe | balance |
420C +QT650 — frequently asked
What is 420C +QT650 used for?
420C +QT650 is typically used for cutlery & blades, surgical instruments and bearings. In short: high-carbon cutlery stainless.
What is the yield strength of 420C +QT650?
420C +QT650 has a typical yield strength of 500 MPa (72.5 ksi) and a tensile strength of 750 MPa (109 ksi) — stronger than 77% of stainless steel grades. Strength varies by condition: see the 7 listed tempers.
Is 420C +QT650 easy to machine?
Not especially — machinability is rated fair (42/100, better than 79% of stainless steel grades). Machine in the annealed condition with sharp, rigid carbide or HSS-Co tooling, moderate speed and heavy flood coolant; above ~45 HRC switch to CBN/ceramic turning or grinding/EDM.
Can 420C +QT650 be welded?
Not readily — weldability is rated poor (20/100). Poor weldability — high carbon promotes hard, crack-prone martensite; if unavoidable, preheat 200–300 °C, use 410NiMo/309 filler, and temper immediately after welding.
What surface finishes work on 420C +QT650?
Takes a mirror polish; harden, temper and then passivate (ASTM A967 nitric/citric) for best corrosion resistance — hard chrome, nitriding or PVD coatings are common for wear parts.
Can 420C +QT650 be formed, bent or molded?
Only light cold forming and blanking in the annealed state (generous bend radii, R ≥ 2t); hot work 1100–850 °C followed by slow cooling and full anneal to avoid quench cracks.
What is the maximum service temperature of 420C +QT650?
420C +QT650 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 420C +A and 420C-H?
+A is the default condition — stock condition for machining, blanking and subsequent hardening; lowest hardness and best machinability. H: as-quenched martensite for maximum hardness; must normally be tempered/stress-relieved before service to avoid cracking. Yield strength is 460 MPa in +A versus 1,600 MPa in H.
Can FabDigit make parts in 420C +QT650?
Yes — 420C +QT650 is available for CNC machining; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- EN 10088-1/-2/-3 (X46Cr13, 1.4034) — CEN (2014)
- GB/T 1220 (4Cr13) — SAC (2007)
- ASTM A276/A582 (Type 420) — ASTM (2017)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Handbook Vol.13B / Vol.16 — Corrosion and Machining — ASM International (2005)
- Martensitic knife/blade strip datasheets (1.4034-class) — Alleima/Sandvik, Böhler (2023)
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.