Steel SK4-CD (Cold drawn)
Supply condition
JIS SK4
Cold-drawn round or flat bar with tight size and clean surface for pin, punch and shaft blanks.
Values for the CD condition
Other SK4 tempers and conditions
SK4 is listed in 10 conditions; see the grade overview at SK4.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefault Solution annealed | Standard stocked condition for bar and strip: softest state for machining, blanking and forming before hardening. | 400 | 670 | 18 | 190 HB | — |
Hot rolled | As-rolled bar and flats, usually re-annealed before machining; cheapest input form. | 450 | 780 | 12 | 22 HRC | 9.5 % IACS |
Normalized | Air-cooled from ~800–850 °C to break up network carbide and refine grain before hardening. | 500 | 850 | 10 | 25 HRC | 9.5 % IACS |
CDThis page Cold drawn | Cold-drawn round or flat bar with tight size and clean surface for pin, punch and shaft blanks. | 620 | 800 | 9 | 22 HRC | 9.5 % IACS |
CR ½H | Partially cold-rolled strip for parts that still need moderate bending before hardening. | 750 | 900 | 6 | 30 HRC | 9.3 % IACS |
Cold rolled strip, full hard (spring temper) | Fully work-hardened strip supplied ready-to-use for flat springs, clips and shim blades without heat treatment. | 1,100 | 1,250 | 2 | 43 HRC | 9.2 % IACS |
Q&T 44–48 HRC | Toughest heat-treated condition, used for coil and leaf springs and shock-loaded tooling. | 1,320 | 1,500 | 6 | 46 HRC | 9.2 % IACS |
Q&T 50–55 HRC | Impact-tolerant tool condition for cold chisels, striking punches and shear blades. | 1,500 | 1,750 | 3 | 52 HRC | 9 % IACS |
Q&T 56–60 HRC | Slightly tougher edge condition for punches, chisels and woodworking blades that see impact. | 1,650 | 1,950 | 1 | 58 HRC | 8.5 % IACS |
Q&T 60–63 HRC | Maximum-hardness condition for knife edges, razors, files, scrapers and wear inserts in thin sections. | 1,800 | 2,100 | 1 | 61 HRC | — |
What is SK4-CD?
SK4-CD is SK4 supplied in the CD condition — cold-drawn round or flat bar with tight size and clean surface for pin, punch and shaft blanks. SK4-CD has a yield strength of 620 MPa (89.9 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 78% of steel grades. Elongation at break is 9% and the elastic modulus is 205 GPa (29.7 Msi). SK4-CD has a density of 7.83 g/cm³ (0.283 lb/in³), lighter than 80% of steel grades. It melts at 1,400°C (2,552 °F). A is the default condition FabDigit quotes; CD is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 75/100, better than 94% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High strength — 620 MPa (89.9 ksi), better than 78% of steel grades
- High electrical conductivity — 9.5 % IACS, better than 75% of steel grades
Limitations
- Difficult to weld — 12/100, worse than 96% of steel grades
- Limited ductility — 9%, worse than 93% of steel grades
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
SK4-CD properties
Typical room-temperature values for SK4-CD; 23 are specific to this condition. Other listed values are SK4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SK4-CD has a density of 7.83 g/cm³ (0.283 lb/in³), lighter than 80% of steel grades. It melts at 1,400°C (2,552 °F).
Mechanical15
SK4-CD has a yield strength of 620 MPa (89.9 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 78% of steel grades. Elongation at break is 9% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
SK4-CD is rated for continuous service to 200°C (392 °F). It conducts heat at 47 W/m·K (27.2 BTU/hr·ft·°F), better than 75% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
SK4-CD 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 SK4-CD takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 25%.
Manufacturability8
SK4-CD's machinability is fair (48/100, worse than 57% of steel grades); weldability not recommended (12/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SK4-CD
Is SK4 easy to machine?
Machine only in the spheroidize-annealed state (~45 % of AISI 1212) with sharp carbide or HSS tooling and good coolant; after hardening, only grinding and EDM are practical.
Can SK4 be welded?
Effectively non-weldable for structural joints — high carbon gives hard, crack-prone martensite; if unavoidable, preheat 250–350 °C, use low-hydrogen filler and post-weld temper immediately.
Can SK4 be formed, bent or molded?
Anneal before blanking or bending; cold-rolled strip work-hardens rapidly, so use generous bend radii, and hot-forge at 1050–850 °C followed by slow cooling and spheroidize annealing.
What surface finishes work on SK4?
Grinds and laps to a fine, high-polish edge; protect with oil, black oxide, phosphate or thin plating (bake after plating to avoid hydrogen embrittlement) since bare surfaces rust quickly.
SK4 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 G 4401 SK95 (old SK4) | 0.9 – 1 | 0.95 |
| Si | 0.1 – 0.35 | 0.22 |
| Mn | 0.1 – 0.5 | 0.35 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Curesidual | ≤ 0.25 | — |
| Niresidual | ≤ 0.25 | — |
| Crresidual | ≤ 0.3 | — |
| Fe | balance | — |
SK4-CD — frequently asked
What is SK4-CD used for?
SK4-CD is typically used for springs, blades, saws and hand tools. In short: tougher than SK3; spring and blade tool steel; hard strip supplied ready to form.
What is the yield strength of SK4-CD?
SK4-CD has a typical yield strength of 620 MPa (89.9 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 78% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is SK4-CD easy to machine?
Reasonably — machinability is rated fair (48/100, worse than 57% of steel grades). Machine only in the spheroidize-annealed state (~45 % of AISI 1212) with sharp carbide or HSS tooling and good coolant; after hardening, only grinding and EDM are practical.
Can SK4-CD be welded?
Not readily — weldability is rated not recommended (12/100). Effectively non-weldable for structural joints — high carbon gives hard, crack-prone martensite; if unavoidable, preheat 250–350 °C, use low-hydrogen filler and post-weld temper immediately.
What surface finishes work on SK4-CD?
Grinds and laps to a fine, high-polish edge; protect with oil, black oxide, phosphate or thin plating (bake after plating to avoid hydrogen embrittlement) since bare surfaces rust quickly.
Can SK4-CD be formed, bent or molded?
Anneal before blanking or bending; cold-rolled strip work-hardens rapidly, so use generous bend radii, and hot-forge at 1050–850 °C followed by slow cooling and spheroidize annealing.
What is the maximum service temperature of SK4-CD?
SK4-CD is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SK4-A and SK4 QT60-63?
A is the default condition — standard stocked condition for bar and strip: softest state for machining, blanking and forming before hardening. QT60-63: maximum-hardness condition for knife edges, razors, files, scrapers and wear inserts in thin sections. Yield strength is 400 MPa in A versus 1,800 MPa in QT60-63.
Sources
- JIS G 4401 — Carbon tool steels (SK95, formerly SK4) — JSA (2009)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol. 4 — Heat Treating (carbon tool steels W-series) — ASM International (1991)
- ASM Handbook Vol. 16 — Machining (machinability ratings) — ASM International (1989)
- GB/T 1298 — Carbon tool steels (T9A/T10A comparison) — SAC (2008)
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.