Steel SK95-QT400
Heat-treated state
JIS SK95 · GB T9A
QT400 = quenched + tempered 400 °C
Pick the 400 °C temper at 45–49 HRC for spring leaves, retaining clips and thin parts that must flex elastically, accepting lower hardness in exchange for 6% elongation.
Values for the QT400 condition
Other SK95 tempers and conditions
SK95 is listed in 10 conditions; see the grade overview at SK95.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Cold Rolled, annealed strip | Choose bright cold-rolled strip in the soft annealed state (185 HB, 20% elongation) for blanking and forming blades, shims and spring leaves that are hardened after forming. | 390 | 650 | 20 | 185 HB | 9.5 % IACS |
ADefault Solution annealed | Order this spheroidize-annealed state as the standard supply condition for machining and press blanking at minimum hardness (192 HB), then quench and temper in-house to working hardness. | 400 | 670 | 22 | 192 HB | — |
Hot rolled | Pick the unannealed as-rolled bar for lowest stock cost, and budget a spheroidizing anneal before machining because 240 HB and 12% elongation cut and form poorly. | 460 | 800 | 12 | 22 HRC | 9.5 % IACS |
Normalized | Use after forging or rough machining to refine grain and break up carbide networks at 270 HB; it is a preparation step for spheroidize annealing or hardening, not a service condition. | 520 | 900 | 10 | 27 HRC | 9.4 % IACS |
Cold Rolled hard strip | Pick work-hardened cold-rolled strip when thin parts need spring action and flatness straight from coil at 32 HRC; elongation of 3% limits any further forming or machining. | 900 | 1,050 | 3 | 32 HRC | 9 % IACS |
Quenched + tempered 500 °C | Use the 500 °C temper (38–43 HRC) for structural tool parts that must absorb impact rather than resist wear; toughness peaks at 9% elongation with 1280 MPa tensile strength. | 1,100 | 1,280 | 9 | 41 HRC | 9 % IACS |
QT400This page Quenched + tempered 400 °C | Pick the 400 °C temper at 45–49 HRC for spring leaves, retaining clips and thin parts that must flex elastically, accepting lower hardness in exchange for 6% elongation. | 1,300 | 1,500 | 6 | 47 HRC | 8.8 % IACS |
Quenched + tempered 300 °C | Choose the 300 °C temper (52–56 HRC) when chisels, punches and shear blades carry heavy impact loads, giving up wear resistance for 3% elongation and 250 °C service. | 1,550 | 1,800 | 3 | 54 HRC | 8.5 % IACS |
Quenched + tempered 200 °C | Use quenching with a 200 °C temper at 58–61 HRC as the normal working hardness for cutting edges and punches, trading a little hardness for usable toughness. | 1,750 | 2,050 | 1 | 60 HRC | — |
Quenched (water) + tempered 150–180 °C | Specify water quenching plus a 150–180 °C temper to 62–64 HRC for razors, carving tools and wood chisels needing maximum edge retention; 0.5% elongation tolerates no impact. | 1,900 | 2,250 | 0.5 | 63 HRC | — |
What is SK95-QT400?
SK95-QT400 is SK95 heat treated to QT400 — pick the 400 °C temper at 45–49 HRC for spring leaves, retaining clips and thin parts that must flex elastically, accepting lower hardness in exchange for 6% elongation. SK95-QT400 has a yield strength of 1,300 MPa (189 ksi) and a tensile strength of 1,500 MPa (218 ksi) — stronger than 95% of steel grades. Elongation at break is 6% and the elastic modulus is 205 GPa (29.7 Msi). SK95-QT400 has a density of 7.83 g/cm³ (0.283 lb/in³), lighter than 80% of steel grades. It melts at 1,420°C (2,588 °F). A is the default condition FabDigit quotes; QT400 is available on request or by drawing note.
Advantages
- High strength — 1,300 MPa (189 ksi), better than 95% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
Limitations
- Difficult to weld — 6/100, worse than 100% of steel grades
- Limited ductility — 6%, worse than 97% of steel grades
- Difficult to machine — 20/100, worse than 97% of steel grades
- Limited formability — 8/100, worse than 97% of steel grades
SK95-QT400 properties
Typical room-temperature values for SK95-QT400; 22 are specific to this condition. Other listed values are SK95 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SK95-QT400 has a density of 7.83 g/cm³ (0.283 lb/in³), lighter than 80% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical15
SK95-QT400 has a yield strength of 1,300 MPa (189 ksi) and a tensile strength of 1,500 MPa (218 ksi) — stronger than 95% of steel grades. Elongation at break is 6% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
SK95-QT400 is rated for continuous service to 320°C (608 °F). It conducts heat at 43 W/m·K (24.8 BTU/hr·ft·°F), better than 51% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
SK95-QT400 conducts electricity at 8.8 % IACS, better than 69% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of SK95-QT400 takes about 32 MJ of energy and emits 2.3 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 30%.
Manufacturability8
SK95-QT400's machinability is poor (20/100, worse than 97% of steel grades); weldability not recommended (6/100); formability not recommended (8/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SK95-QT400
Is SK95 easy to machine?
In the spheroidize-annealed condition (≤207 HB) it turns, mills and drills normally with HSS or carbide. After hardening, only grinding or EDM is practical.
Can SK95 be welded?
At about 0.95 %C welding readily produces cracks and a hard, brittle heat-affected zone. If welding is required, preheat 250–350 °C, use low-hydrogen filler and temper immediately.
Can SK95 be formed, bent or molded?
Annealed sheet and strip can be blanked, bent and coiled. Quench from 760–800 °C in water or brine — hardenability is shallow and distortion and cracking risk is high — then temper immediately.
What surface finishes work on SK95?
After hardening it can be finish ground and polished to a mirror surface. It has no corrosion resistance, so bluing, phosphating, oiling or nickel/chrome plating is required.
SK95 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 |
|---|---|---|
| CJIS G4401 SK95 (formerly SK4) | 0.9 – 1 | 0.95 |
| Si | 0.1 – 0.35 | 0.25 |
| Mn | 0.1 – 0.5 | 0.3 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Curesidual element | ≤ 0.25 | — |
| Niresidual element | ≤ 0.25 | — |
| Crresidual element | ≤ 0.3 | — |
| Fe | balance | — |
SK95-QT400 — frequently asked
What is SK95-QT400 used for?
SK95-QT400 is typically used for hand tools, blades and small dies. In short: JIS equivalent of T9A; low-cost blade steel; water-hardening, shallow depth.
What is the yield strength of SK95-QT400?
SK95-QT400 has a typical yield strength of 1,300 MPa (189 ksi) and a tensile strength of 1,500 MPa (218 ksi) — stronger than 95% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is SK95-QT400 easy to machine?
Not especially — machinability is rated poor (20/100, worse than 97% of steel grades). In the spheroidize-annealed condition (≤207 HB) it turns, mills and drills normally with HSS or carbide. After hardening, only grinding or EDM is practical.
Can SK95-QT400 be welded?
Not readily — weldability is rated not recommended (6/100). At about 0.95 %C welding readily produces cracks and a hard, brittle heat-affected zone. If welding is required, preheat 250–350 °C, use low-hydrogen filler and temper immediately.
What surface finishes work on SK95-QT400?
After hardening it can be finish ground and polished to a mirror surface. It has no corrosion resistance, so bluing, phosphating, oiling or nickel/chrome plating is required.
Can SK95-QT400 be formed, bent or molded?
Annealed sheet and strip can be blanked, bent and coiled. Quench from 760–800 °C in water or brine — hardenability is shallow and distortion and cracking risk is high — then temper immediately.
What is the maximum service temperature of SK95-QT400?
SK95-QT400 is rated for continuous use to about 320°C (608 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SK95-A and SK95-QT160?
A is the default condition — order this spheroidize-annealed state as the standard supply condition for machining and press blanking at minimum hardness (192 HB), then quench and temper in-house to working hardness. QT160: specify water quenching plus a 150–180 °C temper to 62–64 HRC for razors, carving tools and wood chisels needing maximum edge retention; 0.5% elongation tolerates no impact. Yield strength is 400 MPa in A versus 1,900 MPa in QT160.
Sources
- JIS G4401 Carbon tool steels — JISC (2009)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Handbook Vol.16 — Machining — ASM International (1989)
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.