420 ESR Tool Steel - 1.2083 ESU - X40Cr14 - SAE 51420

Why use ESR steel?

Electro-Slag-Remelted or ESR also known as electro-flux remelting is a process where steel is remelted and passes through slag which removes debris and impurities from the steel. What is left is steel with a higher cleanliness and a finer, more homogeneous microstructure. Reducing the impurities from steel gives the steel an overall integrity as there are fewer weak spots. ESR steel can exhibit better mechanical properties like higher tensile strength, yield strength, toughness, wear resistance, better surface finishes, longer tool life.

Specifically for the 420 ESR as an already corrosion resistant steel, the ESR process improves the corrosion resistance due to the reduction of inclusions and other impurities. 

Where can tool steel 420 ESR be used?

Applications with corrosion or staining resistance, e.g., for molding of corrosive materials like PVC, acetates, for molds subjected to humid working conditions as well as surgical and dental instruments and tools.

Applications with wear resistance, e.g., for molding abrasive materials.

Applications with high surface finish, e.g., for the production of optical parts, such as lenses, for cameras and sunglasses, and for medical containers.

Is 420 ESR a stainless steel?

Yes, the 420 ESR is stainless steel. To be classed as stainless steel the material has to have at least 10.5% chromium, the 420 ESR has 12.5 - 14.5% of chromium.  

Is tool steel 420 ESR corrosion resistant?

With a mass fraction of 12.5 - 14.5% of chromium tool steel 420 ESR is corrosion resistant. 

General corrosion for tool steel 420 ESR

420 ESR is corrosion resistant in water, steam, mild organic acids, diluted solutions of nitrates, carbonates, and other salts.

Is  tool steel 420 ESR magnetizable?

Yes, the 420 ESR is generally magnetic and in its hardened condition even more so than in its annealed condition. This metal is suitable for magnetic clamping.

Heat treatment for tool steel 420 ESR

Annealing tool steel 420 ESR

Heat the material thoroughly to 1630°F (890°C). Then furnace cool slowly to 1290°F (650°C) and then air cool to room temperature.

Stress relieving tool steel 420 ESR

After machining 420 ESR, heat the part through to 1200°F (650°C) and hold for 2 hours. Cool down to 930°F (500°C) and then cool further in air.

Hardening tool steel 420 ESR

Preheat the part to 1110 - 1560°F (600 - 850°C).

To austenitize the material heat to 1850 - 1952°F (1010 - 1067°C).

Quenching tool steel 420 ESR

Cool quickly to obtain the best properties for the tool, but care should be taken that the rate of cooling is not as fast as to distort or crack the material. It is recommended when heat treating in a vacuum furnace to use a minimum of 4 - 5 bars of overpressure.

Then temper immediately when the parts reach the temperature of 120 - 160°F (50 - 70°C).

• Fluidized bed or salt bath at 480 - 1020°F (250 - 550°C), then cool in air blast
• Vacuum with sufficient positive pressure
• Warm oil, approx. 176°F (80°C)

Tempering tool steel 420 ESR

Choose the tempering temperature that needs to be achieved, temper twice and cool between tempering to room temperature.

Do not let the tempering temperature drop below 480°F (250°C) and hold at the chosen temperature for a minimum of 2 hours. The temperature of 480°F (250°F) is recommended to achieve the best blend of hardness, toughness as well as corrosion resistance.

Dimensional changes of the 420 ESR tool steel

Depending on temperature, type of equipment and cooling media used during hardening and tempering, dimensional changes may vary.

Sub-Zero treatment for tool steel 420 ESR

Cryogenic treatment for the 420 ESR can transform retained austenite to martensite and can enhance properties like dimensional stability for this material. 

Electrical Discharge Machining (EDM) of the 420 ESR tool steel

As a hard material, conventional machining methods might be challenging and can cause excessive tool wear. As there is no direct contact to the material during EDM tool wear is not an issue as such, though electrodes have to be replaced periodically. EDM is often used for hard materials, for intricate and complex shapes, and when tight tolerances are needed as well as when parts need a good surface finish.

420 ESR tool steel surface treatment

420 ESR tool steel passivation

Passivation removes free iron from the surface by treating the surface with an acid solution that promotes a protective oxide layer to enhance the corrosion resistance. 

Polishing 420 ESR tool steel

420 ESR tool steel can be polished to an excellent finish as ESR material is cleaner and more homogeneous. Polishing reduces friction, improves a surface finish and enhances the aesthetic appeal.  

Physical Vapor Deposition (PVD), Chemical Vapor Deposition(CVD) coating the 420 ESR

PVD and CVD apply a hard coating, for example TiN (titanium nitride), to improve wear resistance and hardness of the material.

Electroplating the 420 ESR

This process deposits a metal layer, for example nickel or chrome, onto the metal surface to make it more corrosion resistant, reduce friction or just give the parts a more decorative appeal.

Laser or mechanical texturing the 420 ESR

Texturing creates a pattern on the material surface which might be for aesthetic purposes but can as well be functional for lubricant retention or to improve the grip to the part.

Tool steel 420 ESR machinability

Welding 420 ESR tool steel

Welding should be avoided, if possible, due to the high risk of cracking.

Should welding be essential, heat material through to 392 - 482°F (200 - 250°C) and hold at that temperature to prevent cracking. After welding, temper hardened material at 50 - 70°F (10 - 20°C) below the original tempering temperature. For soft annealed material heat through to 1630°F (890°C) in a protected atmosphere. Then furnace cool at 40°F (20°C) per hour to 1560°F (850°C) and then at 20°F (10°C) per hour to 1290°F (700°C). From there it can be cooled further in air. 

Fillers with the same composition as the base metal should be used.

Photo-etching 420 ESR tool steel

Due to the ESR process, 420 ESR has a very low inclusion content and makes it therefore suitable for photo-etching.

420 ESR tool steel wear resistance

The wear resistance for tool steel 420 ESR is 4 on a scale where 1 is low and 6 is high.

Tensile strength for tool steel 420 ESR

Tool steel 420 ESR has a tensile strength of approx. 118.2 KSI on delivery (0.145 KSI = 1MPa). In order to reach this value, a tensile test is performed to show how much force is needed to stretch or elongate a sample before it breaks.

420 ESR tool steel yield strength

The yield strength shows how much stress can be applied to a material before it plastically deforms. Beyond this point it does not return to its original form when stresses are removed. The material deforms permanently or breaks past that point. 

The range for the tool steel 420 ESR is 232 KSI (1600 MPa).

Working hardness for the AISI 420 ESR

The working hardness for the AISI 420 ESR tool steel is in a range of 469 - 552 BHN (50 - 55 HRC).

Specific heat capacity for tool steel 420 ESR

The specific heat capacity of tool steel 420 ESR is at room temperature at 0.46 J/g-°C (0.109 BTU/lb-°F). This value shows how much heat is needed  to heat 1lb of material by 1 Fahrenheit.

Continuous TTT-diagram for tool steel 420 ESR

This diagram shows the micro changes at different temperatures which are important during heat treatment. They show the optimum condition for the hardening, annealing and normalizing process.

Steel Properties for 420 ESR tool steel

Cold working 420 ESR tool steel

Careful management is required to cold work the 420 ESR to prevent cracking and dimensional accuracy. Cold working this material can enhance its hardness and strength.

Steel Density for the 420 ESR tool steel

Typically the density of 420 ESR tool steel is 0.282 lb/in3 (7.8 g/cm3) at room temperature.

Thermal conductivity of tool steel 420 ESR

The heat conductivity for tool steel 420 ESR is at 22.6 W/(m*K) (157 BTU/(h-ft*°F)) at room temperature.

Thermal expansion coefficient for tool steel 420 ESR

This diagram shows how much tool steel 420 ESR might expand or contract when the temperatures change which can be very important when working with high temperatures or strong temperature changes.

Specific electrical resistivity for the 420 ESR

The following table shows the electrical resistivity of tool steel 420 ESR. 

Is AISI 420 ESR a knife steel?

Yes, 420 ESR can be used for knife making. Due to its purity, toughness, corrosion resistance and edge retention the 420 ESR lends itself to knife making. Though the 420 ESR has good corrosion resistance, regular maintenance, cleaning and drying will prolong tool life and performance.

Conclusion

420 ESR is a cleaner and more homogeneous material with good corrosion resistance, hardness and toughness and is easy to machine, responds well to heat treatment which makes it ideal for a wide variety of applications from industrial tools to medical instruments. High polished it even finds its way into our homes as cutlery.

Datasheet for the 420 ESR tool steel

As a 420 ESR steel supplier we provide you with the datasheet for tool steel 420 ESR in PDF format.

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