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O1 1.2510 SKS3 Cold Work Tool Steel

O1 Cold Work Tool Steel offers excellent wear resistance, toughness, and dimensional stability. With good hardenability and machinability, it is ideal for punches, dies, gauges, and cutting tools.

Standard: AISI O1, DIN 1.2510, JIS SKS3, GB 9CrWMn
Technique: EAF + LF + VD or ESR, forged, multi-directional forging ratio ≥4, spheroidized annealed
Shape: Round, Flat, Plates, Blocks
Heat treatment: Supplied in annealed condition, hardness ≤229 HBW; pre-hardened to 58–62 HRC (quenched and tempered) available on request
Surface Treatment: Black (hot-rolled / forged surface), turned, milled / ground, sawn ends
Tolerance: flat bars & plates thickness: +0.5/-0.0 mm (turned); forged blocks: ±0.2 mm
MOQ: 1 Ton

We supply AISI O1 in various custom sizes

Chemical Composition (%)

Grade	C	Si	Mn	P (≤)	S (≤)	Cr	W	V	(Other Elements, ≤)
1.2510 (100MnCrW4)	0.90–1.05	0.15–0.35	1.00–1.20	0.030	0.030	0.50–0.70	0.50–0.70	0.05–0.15	Ni 0.25, Cu 0.25
O1	0.85–1.00	0.10–0.50	1.00–1.40	0.030	0.030	0.40–0.70	0.40–0.60	≤0.30	Ni 0.25, Cu 0.25
SKS3	0.90–1.00	≤0.35	0.90–1.20	0.030	0.030	0.50–1.00	0.50–1.00	—	Ni 0.25, Cu 0.25
9CrWMn	0.85–0.95	≤0.40	0.90–1.20	0.030	0.030	0.50–0.80	0.50–0.80	—	Ni 0.25, Cu 0.25

Main characteristics of O1 tool steel

O1| 1.2510 | SKS3 tool steel applications

O1 steel for Precision Blanking Die

Low distortion after oil quenching and good edge-holding ability make 1.2510 ideal for precision blanking of thin to medium-gauge sheet metal

O1 steel for Cold Forming & Bending Die

Excellent machinability and balanced toughness allow reliable performance in complex cold forming and bending dies, minimizing cracking risks

O1 steel for Gauge & Precision Tool

High attainable hardness and minimal heat treatment deformation ensure lasting dimensional stability in gauges, master tools, and precision instruments.

Our Production Technology For 1.2510 (O1 / SKS3 / 9CrWMn) Cold Work Tool Steel

Ultrasonic testing (UT) 100% as per SEP 1921, ASTM A388, or EN 10228-3 (upon request)
Micro Cleanliness as per ASTM E45 or DIN 50602
Spheroidized microstructure as per relevant tool steel standards
Macrostructure, microstructure, grain size, and mechanical properties shall meet the standards specified in GB/T 1299 for Tool and Die Steels
Delivery condition: Soft annealed, hardness max. 230 HB (approx. 21 HRC)

mechanical properties & heat treatment of O1 steel

Heat temperature	Start forging temperature	Finish forging temperature	Cooling method
1050 – 1100 °C	1000 – 1050 °C	≥ 850 °C	Pit, sand, or furnace cooling

Annealing

Heat slowly and uniformly to 740 – 770°C (or 750–780°C, 720–750°C by some sources) and soak thoroughly
Hold at temperature for 2 – 5 hours, depending on section thickness
Cool slowly in the furnace at a controlled rate down to approximately 600°C
Then air cool to room temperature
Hardness after annealing: max. 230 HB (approx. 21 HRC)
Annealing in a protective atmosphere is recommended to reduce decarburization

Hardening

1.2510 (O1) is an oil-hardening cold work tool steel. It is a low-alloy steel containing manganese, chromium, and tungsten, characterized by giving high surface hardness after heat treatment, good dimensional stability in hardening, and good machining characteristics. Hardening by oil quench minimizes distortion and cracking
Pre-heating (recommended): Where possible, pre-heat at 300 – 500°C (572 – 932°F) before austenitizing
Austenitizing temperature: 780 – 820°C (1436 – 1508°F).
Salt bath: 780–820°C.
Controlled atmosphere furnace: 780–820°C
Holding time: After temperature equalization, hold for 30 minutes per 25mm (1 inch) of ruling section
Quenching media:
Oil (preferred for most sections, quench immediately after holding)
Warm bath at 180–220°C (martempering) as an alternative hardening procedure when suitable salt bath equipment is available
Hardness after quenching: 64 – 65 HRC

Stress relieving

Perform after rough machining or heavy stock removal, especially for tools with unbalanced cross-sections, to reduce the risk of distortion during final heat treatment
Heat carefully to approx. 650°C (1202°F)
Hold at temperature for 1 – 2 hours (or 2 hours per 25mm of section thickness)
Cool slowly in the furnace, or air cool after holding

Tempering

Temper immediately after the workpiece cools to hand-warm temperature (approx. 50–70°C). Delayed tempering may cause cracking
Number of tempers: Minimum 2 times. Double tempering is recommended to improve toughness and ensure complete transformation
Holding time: Soak for at least 1 hour per 25mm (1 inch) of total thickness (minimum 2 hours per cycle)
Cooling method: Air cool after each tempering cycle (must cool to room temperature before the next tempering)

Why Choose NSPM as Your O1 Tool Steel Supplier

Source Direct

Direct mill cooperation ensures stable supply, competitive pricing, and consistent quality. Global resource integration and strong supply chain management guarantee reliable material sourcing and long-term availability.

Stock Ready

50,000+ tons inventory across 11 warehouses enables fast delivery. Flexible cutting, short lead times, and ready stock support urgent demands and improve customers’ production efficiency.

Expert Team

600+ professionals, including R&D specialists and technical engineers, provide application-driven support. Fast response and deep tooling knowledge ensure accurate solutions for diverse industrial needs.

Fully Inspected

Strict quality control system with full traceability, UT testing, and heat treatment records. Certified standards (ISO, CE) ensure every material meets high-performance and reliability requirements.

Full-Chain Machining

From steel supply to precision machining, heat treatment, and equipment manufacturing, NSPM offers integrated solutions that enhance accuracy, efficiency, and overall tooling performance.