SKT4 tool steel
SKT4 Tool Steel - Image 2
SKT4 Tool Steel - Image 3
Tool Steel Warehouse
Tool Steel Warehouse
SKT4 Tool Steel - Image 6
Turning
Factory

SKT4 Tool Steel

SKT4 tool steel is a premium grade hot work mould steel designed to meet the challenges of high temperature forming operations. Where conventional tool steels fail under extreme thermal and mechanical stresses, SKT4 retains its structural integrity and performance properties.The Japanese standard JIS SKT4 tool steel corresponds to the American standard L6, and the German standard ASTM is 55NiCrMoV6/1.2713 tool steel.
SKT4 solves the problem of premature tool failure in hot work applications through its optimised chemistry and specialised heat treatment process, providing excellent resistance to thermal fatigue and longer service life. The result is significantly lower tooling costs, reduced production interruptions and consistent end product quality over longer production runs.

SKU: N/A Categories: , Tags: , ,
Get Factory Price

SKT4 Tool Steel Product Introduction

SKT4 Tool Steel

SKT4 tool steel is a medium-alloyed hot work tool steel conforming to the Japanese Industrial Standard (JIS G4404) and is classified as a special tool steel for forging dies. Its chemical composition is based on medium carbon as the core, supplemented by chromium, molybdenum, manganese and other elements, and strict control of phosphorus and sulfur impurities. It has excellent high-temperature stability (hardness remains about 300 HB at 500°C) and uniform hardenability, and the hardness distribution remains highly consistent even after heat treatment of large sections.
By oil quenching and hardening (oil cooling at 830-860°C) and tempering in a wide temperature zone (150-600°C), SKT4 can be optimised to a hardness of 46-52 HRC (for conventional applications) or 53-58 HRC (for high wear resistance requirements), forming a tempered martensitic organisation. The nature of the design relies on molybdenum to suppress temper brittleness (only a small reduction in impact toughness after cooling at 600°C) and a vacuum refining process to reduce grain boundary impurity bias, balancing thermal strength and thermal fatigue resistance while maintaining high toughness, especially for repeated thermal cycling conditions.

SKT4 Tool Steel Types and Options

SKT4 Tool Steel Types and Options

The table below shows the size range, surface condition and tolerance details for SKT4 Mould Steel:SKT4 Tool Steel Types and Options

SKT4 Tool Steel Customized Options

SKT4 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. SKT4 Tool Steel Electroslag Remelting (ESR): premium option with higher purity and isotropic properties for critical applications.

SKT4 Tool Steel Chemical Composition

SKT4 Tool Steel Chemical Composition

SKT4 Tool Steel Heat Treatment Process

SKT4 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.

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.

SKT4 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.

SKT4 Tool Steel Technical Specifications

SKT4 Tool Steel Technical Specifications

SKT4 Tool Steel Product Applications

SKT4 Tool Steel Factory

Main application scenarios

Extrusion tooling

For aluminium extrusion tooling with operating temperatures up to 550°C, SKT4 provides the critical combination of wear resistance and thermal stability required to maintain precise profiles over long production runs. The steel's excellent thermal hardness prevents premature wear of bearing surfaces, while its resistance to thermal fatigue prevents corner and thin section cracking. Extrusion companies report up to 40% longer die life and improved surface finish of extruded products when using SKT4 dies compared to conventional hot work steels.

Hot shear applications

In hot shear and dressing operations, SKT4 maintains a sharp cutting edge at high temperatures where other steels soften and deform. The combination of high thermal hardness and good toughness prevents both premature passivation and catastrophic failure due to chipping. Steel processors using SKT4 for hot dressing operations report up to 50 per cent longer insert life and less downtime for insert replacement and maintenance.

Pressure die casting tools

For pressure die casting tools that handle copper and brass alloys, SKT4 offers excellent resistance to thermal fatigue cracking and thermal splitting. The steel's ability to maintain dimensional stability and resist plastic deformation under a combination of thermal and mechanical loads ensures consistent part quality and longer tool life. Die casting operations report significant reductions in maintenance costs and increases in productivity when using SKT4 for cores, ejectors and inserts.

Industry-specific applications

  1. Automotive: transmission housings, engine blocks, wheel components.
  2. Aerospace: turbine components, structural parts, landing gear components.
  3. Consumer products: appliances, power tools, electronics housings.
  4. Construction equipment: hydraulic component moulds, structural parts.

SKT4 Tool Steel Competitive Advantage Comparison

SKT4 Tool Steel Competitive Advantage Comparison

SKT4 Tool Steel Customer Success Stories

Skip the middleman link, source factory purchasing, reduce purchasing cost and improve market competitiveness.

SKT4 Tool Steel Pricing Structure Information

Serving the world, whole cabinet sales, factory wholesale price.

SKT4 Tool Steel Frequently Asked Questions

Q: How does SKT4 compare to standard H13 in die casting applications?
A. SKT4 typically lasts 35-45% longer than H13 tool steel in aluminium die casting applications due to superior thermal fatigue resistance and better retention of thermal hardness. This reduces thermal cracking and reduces plastic deformation during long production runs.

Q: What are the key factors affecting the performance of SKT4 in service?
A. The key factors are proper heat treatment, operating temperature, cooling conditions, surface finish quality, and loading conditions. Our application engineers can help you optimise these factors for your specific application.

Q: How does the typical cost of SKT4 compare to standard H13 over the life of the tool?
A. Although the initial cost of SKT4 is 15-25 per cent higher than H13, the total life cycle cost is typically 25-35 per cent lower due to extended service life, reduced downtime, fewer replacement tools and lower maintenance requirements.

Reviews

There are no reviews yet.

Be the first to review “SKT4 Tool Steel”

Your email address will not be published. Required fields are marked *

Related products