Stainless Steel 420C · heat-treated state
Stainless Steel 420C +QT800
Properties of the +QT800 condition, compared with the other 420C tempers.
Medium-strength Q&T condition where some impact toughness must be retained alongside higher strength.
What is 420C +QT800?
420C +QT800 is 420C heat treated to +QT800 — medium-strength Q&T condition where some impact toughness must be retained alongside higher strength. 420C +QT800 has a yield strength of 650 MPa (94.3 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 90% of stainless steel grades. Elongation at break is 11% and the elastic modulus is 215 GPa (31.2 Msi). 420C +QT800 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; +QT800 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 — 650 MPa (94.3 ksi), better than 90% of stainless steel grades
Limitations
- Limited ductility — 11%, worse than 96% of stainless steel grades
- Difficult to weld — 20/100, worse than 96% of stainless steel grades
- Low fracture toughness — 55 MPa·√m (50.1 ksi·√in), worse than 94% of stainless steel grades
- Needs corrosion protection — 42/100, worse than 90% of stainless steel grades
- Limited service temperature — 400°C (752 °F), worse than 78% of stainless steel grades
420C +QT800 properties
Typical room-temperature values for 420C +QT800 — 8 properties are specific to this condition; the rest are grade-level values shared by every 420C temper. Each bar shows where the value sits among the stainless steel grades in FabDigit's library — further right is higher.
Physical3
420C +QT800 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 +QT800 has a yield strength of 650 MPa (94.3 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 90% of stainless steel grades. Elongation at break is 11% and the elastic modulus is 215 GPa (31.2 Msi).
Thermal6
420C +QT800 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 +QT800 conducts electricity at 3.1 % IACS, better than 99% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (42/100), worse than 90% of stainless steel grades.
Sustainability4
Producing a kilogram of 420C +QT800 takes about 50 MJ of energy and emits 3.4 kg of CO₂ — less than 81% of stainless steel grades. Typical recycled content is 45%.
Manufacturability8
420C +QT800's machinability is fair (35/100, better than 51% of stainless steel grades); weldability poor (20/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 420C tempers and conditions
420C is also supplied in 7 other conditions. The full side-by-side table is on the 420C overview.
- +ADefaultStock condition for machining, blanking and subsequent hardening; lowest hardness and best machinability.460 MPa yield · 20 HRC
- CR+HT stripPrecision-rolled, continuously hardened-and-tempered thin strip supplied ready to blank and grind into blades.1,850 MPa tensile
- QT 50-55 HRCStandard cutlery/surgical-blade condition: maximum wear resistance and edge retention with acceptable corrosion resistance.1,550 MPa yield · 54 HRC
- QT 45-50 HRCBest hardness/toughness compromise for shear blades, valve components and moulds.1,300 MPa yield · 48 HRC
- +QT800Medium-strength Q&T condition where some impact toughness must be retained alongside higher strength.650 MPa yield · 28 HRC
- +QT650High-temperature-tempered condition for shafts and structural parts needing ductility rather than wear resistance.500 MPa yield · 21 HRC
Working with 420C +QT800
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 +QT800 — frequently asked
What is 420C +QT800 used for?
420C +QT800 is typically used for cutlery & blades, surgical instruments and bearings. In short: high-carbon cutlery stainless.
What is the yield strength of 420C +QT800?
420C +QT800 has a typical yield strength of 650 MPa (94.3 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 90% of stainless steel grades. Strength varies by condition: see the 8 listed tempers.
Is 420C +QT800 easy to machine?
Not especially — machinability is rated fair (35/100, better than 51% 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 +QT800 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 +QT800?
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 +QT800 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 +QT800?
420C +QT800 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.
Can FabDigit make parts in 420C +QT800?
Yes — 420C +QT800 is available for CNC machining with instant online pricing. 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.