SKS3 Tool Steel

SKS3 Tool Steel Product Introduction

SKS3 tool steel is a high carbon, low alloy tool steel according to the Japanese JIS G4404 standard, with carbon, manganese, chromium and tungsten as its main components, supplemented by traces of molybdenum and silicon. The steel is vacuum refined to ensure purity and ball annealed to optimise the organisation (ex-factory hardness of approx. 230 HBS), which significantly improves machinability.
SKS3 takes high hardness (HRC ≥ 60 after quenching) and dimensional stability as its core advantages, and quenching requires a staged preheating (550°C-650°C) followed by heating to 800°C-850°C oil cooling and tempering at 150°C-200°C to stabilise the organisation and reduce deformation. Its high carbon content to support excellent wear resistance, but need to strictly control the heat treatment parameters (such as avoiding overheating) to balance the toughness, to adapt to the needs of precision machining.

SKS3 Tool Steel Types and Options

The table below shows the size range, surface condition and tolerance details for SKS3 mould Steel:

Shape	Pocess	Size range	Surface	Tolerance
Flat Bar	Hot Rolled	Thickness: 10-400mm Width: 200-800mm Length: 3000-5800mm	Black; Sandblasted	Thickness :0-+2MM Width:0-+5MM/0-+10MM
	Hot Forged	Thickness: 50-500mm Width: 50-1500mm Length: 3000-5800mm	Black	Thickness:+2-+5MM Width:0-+5MM/0-+10MM
			Turned/Machined/Milled/Bright	Thickness :0-+2MM Width:0-+5MM/0-+10MM
Round Bar	Hot Rolled	Diameter:10-65mm Length:3000-5800mm	Black	0-+2MM
			Turned/Machined	0-+2MM
	Hot Forged	Diameter:70-700mm Length:3000-5800mm	Grinded	0-+5MM/+2-+5MM
			Turned/Machined/Milled/Bright	0-+2MM

SKS3 Tool Steel Customized Options

1. Customized chemical composition: GB, DIN, ASTM, JIS and other standard grades can be produced. Chemical composition can be customized individually.
2. Customized specifications: round steel (diameter), plate (thickness, width) can be customized production.
3. Specialized packaging for long term storage or extreme transportation conditions: includes spraying black paint all around, wrapping plastic film, spraying anti-rust oil, and shipping in wooden crates.
4. Customized production based on samples or technical agreements.
5. SKS3 Tool Steel Electroslag Remelting (ESR): premium option with higher purity and isotropic properties for critical applications.

SKS3 Tool Steel Chemical Composition

Standard/Steel Grade		Chemical Composition(%)
		C	Si	Mn	Cr	V	W
ASTM	O1	0.85~1.00	0.10~0.50	1.00~1.40	0.40~0.60	≤0.30	0.40~0.60
DIN/W-Nr.	100MnCrW4/1.2510	0.90~1.05	0.15~0.35	1.00~1.20	0.50~0.70	0.05~0.15	0.50~0.70
JIS	SKS3	0.90~1.00	≤0.35	0.90~1.20	0.50~1.00	-	0.50~1.00

SKS3 Tool Steel Heat Treatment Process

1.Annealing

Purpose: to eliminate internal stresses generated during forging or rolling, reduce hardness, improve cutting performance, and prepare for subsequent processing and heat treatment.
Process parameters:
Heating temperature: 800-850 ℃, holding time 2-4 hours, with the furnace cooling to below 500 ℃, and then air-cooled.
Hardness after annealing: ≤230 HBS.

2.Quenching

Purpose: to make the tool steel to obtain martensitic organization, improve hardness and wear resistance.
Process parameters:
Heating temperature: 1000-1050 ℃ (commonly used 1020-1040 ℃), holding time according to the size of the workpiece to determine, generally 30-60 minutes.
Cooling: oil cooling or air cooling (for small size or simple shape of the workpiece), large workpieces can be graded quenching (in the 260-300 ℃ salt bath cooling for a period of time and then air-cooled), in order to reduce the quenching stress, to prevent deformation and cracking.

3.Tempering

Purpose: to eliminate quenching stress, adjust the hardness and toughness, stable organization and size.
Process parameters:
low-temperature tempering: 150-250 ℃, insulation 2-3 hours, air-cooled, tempered hardness of 58-62HRC, for molds requiring high hardness and wear resistance.
Medium temperature tempering: 300-500 ℃, insulation 2-3 hours, air-cooled, tempered hardness of 50-58HRC, can improve the toughness, suitable for molds subject to impact load.
High-temperature tempering: 500 ℃ or more, insulation 2-3 hours, air-cooled, tempered hardness 45-50HRC, mainly for the need for higher toughness of the occasion.

4.Precautions

Heating process should control the rate of heating to avoid too rapid a rise in temperature leading to workpiece surface oxidation and decarburization. Protective atmosphere heating can be used or placed in the furnace charcoal and other anti-decarburization agent.
When quenching and cooling, choose the appropriate cooling medium and cooling method according to the shape and size of the workpiece to ensure the quenching effect while reducing the risk of deformation and cracking.
Tempering must be sufficient to ensure the elimination of internal stresses to avoid mold failure due to stress release during use. For large molds or workpieces with complex shapes, multiple tempering can be used.

SKS3 Tool Steel Quality Inspection

1.Surface Condition Inspection

FCS factory has a very strict quality inspection team, we will carefully check the surface condition of each piece of tool steel to ensure that the steel surface is free from cracks, folds, knots, oxidized skin, pitting, scratches and other defects.

2.Chemical Composition Testing

To verify whether the content of alloying elements meets the standard requirements and to safeguard the basis of the mechanical properties of the material. We will let the staff use full-spectrum direct reading spectrometer to analyze multiple elements at the same time. Sampling needs to remove the surface oxidation layer, using a block specimen to stimulate the test.

3.Dimension and Tolerance Inspection

FCS factory will use professional measuring tools to inspect the dimensions and tolerances of the steel to ensure compliance with the customer's contract requirements. Corresponding gauges will be selected according to the dimensional accuracy requirements, including tape measure, high-precision vernier calipers (0.02mm), micrometers (0.001mm), and special inspection gauges. Inspection items cover: diameter, thickness, width, length, hole diameter, chamfering dimensions, etc., to ensure that the tolerances and dimensions meet the contract requirements.

4.Hardness test

Our FCS factory will use professional hardness tester to test the hardness of steel to ensure that it meets the customer's contract requirements.

5.Ultrasonic Testing

Ultrasonic Testing Standard (UT Test Standard) is: Sep 1921-84 Class3 D/d,E/e.
FCS factory uses ultrasonic testing equipment to detect macro defects inside the material (such as cracks, shrinkage holes, inclusions, white spots, etc.), and every piece of round steel and plate will be examined by a second flaw detection test before shipment to ensure that the quality is qualified before shipment.

6.Microstructure Inspection

(1) Metallographic Analysis

FCS factory will use metallographic analysis instrument to detect the microstructure state after heat treatment, including carbide distribution, martensite morphology, residual austenite content, etc.

 (2) Grain size rating

FCS factory will use the comparative method to determine the austenite grain size by comparing the microstructure of the specimen with the standard rating chart, to ensure that it meets the customer's requirements.

SKS3 Tool Steel Technical Specifications

Property	Specification	Test Method
Density	7.85 g/cm³	ASTM A773
Annealed Hardness	≤ 230 HB	ASTM E10
Hardness (After Hardening)	58-62 HRC	ASTM E18
Elastic Modulus	210 GPa	ASTM E111
Thermal Conductivity	41.5 W/m·K	ASTM E1461
Coefficient of Thermal Expansion	11.5×10⁻⁶/K	ASTM E228
Electrical Resistivity	0.17 μΩ·m	ASTM B193

SKS3 Tool Steel Product Applications

Key Application Scenarios

Stamping and drop moulds

SKS3 excels in high-volume precision metal stamping (dimensional accuracy and wear resistance are key). Feedback from customers in the automotive parts industry: switching to SKS3 with proper heat treatment has increased tool life by 40%. The dimensional stability of the heat treatment ensures consistent part production and minimal mould maintenance.

Plastic injection moulded components

For moulding plastics containing abrasive compounds or glass fibres, SKS3 combines surface wear resistance with polishability. High hardness (up to 62 HRC) + excellent thermal conductivity supports consistent cycle times and low maintenance at high throughput.

Shear blades and industrial knives

SKS3 is the best performer in the twin critical scenarios of edge retention and toughness. Industrial cutting involving sheet metal, rubber, plastics and composites benefit from its balanced performance, with sharper cuts and less blade changes.

Industry-Specific Applications

1. Automotive: body panels and precision component stamping dies.
2. Electronics: leadframe stamping tools and connector moulding dies.
3. Aerospace: precision gauging and moulding dies for sheet metal components.
4. Medical: surgical instrument components requiring precise dimensions.
5. Consumer Goods: long lead time production tools for metal/plastic components.

SKS3 Tool Steel Competitive Advantage Comparison

Performance Attributes	FCS Factory's SKS3 Tool Steel	High Carbon Tool Steel
Wear Resistance	Excellent	Moderate
Dimensional Stability	Excellent	Fair
Machinability (Annealed)	70%	80%
Heat Treatment Complexity	Moderate	Low
Through-Hardening Capability	Yes	No
Cost Efficiency	High	Very High
Ideal Application	Precision dies requiring a balance of wear resistance and toughness	Low-stress applications

SKS3 Tool Steel Customer Success Stories

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SKS3 Tool Steel Pricing Structure Information

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SKS3 Tool Steel Frequently Asked Questions

SKS3 vs D2 for stamping applications?
SKS3 toughness and machinability is better than D2, D2 wear resistance is better. SKS3 is suitable for wear + impact resistance scenarios, D2 is more suitable for high abrasion (brittle insensitive) scenarios.

Is SKS3 suitable for vacuum heat treatment?
Yes, it is! Vacuum heat treating optimises surface quality and reduces decarburisation, but oil quenching is still required and vacuum furnace capability is required.

What are the storage precautions for SKS3?
Store in a dry environment with a rust inhibitor; precision ground materials require additional protection against mechanical damage; storage at a constant temperature is optimal (protection against condensation).

What are the processing recommendations for SKS3?
In the annealed state, standard tool steel processes (carbide tools, reasonable cooling, medium speeds) can be used; after hardening, grinding, EDM or hard machining is recommended.