5120 Tool Steel - ~1.2162 / 1.7147 - ~21MnCr5 / 20MnCr5

Where can tool steel 5120 be used?

5120 is a case hardening steel, which is often used for medium to highly stressed parts, for example gears, gear shafts and connecting rods, in the automotive and general engineering industry. It also finds its uses as mold plates due to its surface hardness or resin press molds to process thermoplastics as well as gauges, other measuring tools and auxiliary tools such as clamping tools. This case hardening mold steel can reach a core strength of approx. 145-189 KSI (1000 - 1300 MPa).

Is tool steel 5120 a stainless steel?

Stainless steel has to have a mass fraction of a minimum of 10.5% of chromium. With a chromium content of 1 - 1.3% the 5120 is not a stainless steel.

Is the 5120 tool steel corrosion resistant? 

To be classed corrosion resistant the steel grade has to have a chromium content of at least 10.5%, the 5120 has a maximum content of 1.3% and is therefore not a classic corrosion resistant steel.

Is tool steel 5120 magnetizable?

As a ferromagnetic steel the 5120 can be magnetized and is suitable for magnetic clamping.

Heat treatment for tool steel 5120

Annealing AISI 5120

Heat the work pieces uniformly to a temperature of 1238 - 1310°F (670 - 710°C) and finish the process with a slow furnace cooling. This process can reduce the hardness of the steel or increase the toughness of it as well as relieve internal stresses.

Normalizing tool steel 5120

To normalize tool steel 5120, heat it to a temperature of 1652 - 1706°F (900 - 930°C), then cool the parts slowly down to room temperature in air. This process is done to refine grain structure as well as to improve the materials toughness, strength and machinability.

Carburizing tool steel 5120

Heat the material to a temperature range of 1652 - 1742°F (900 - 950°C). With intended process and required microstructure in mind choosing the right temperature, time, medium and equipment is important. Carburizing introduces carbon into the surface of the material to give it a harder shell and to retain a tough core, this will give the material the ability to withstand wear and at the same time being tough enough to withstand high impact.

Intermediate annealing tool steel 5120

Heat 5120 case hardening steel to a temperature of 1166 - 1202°F (630 - 650°C) for about 2-4 hours then slowly cool it in the furnace.

Hardening (core hardening) tool steel 5120

Heat to a curing temperature of 1562 - 1616°F (850 - 880°C) and quench the material in oil or water (water is being used for simple shaped large components only) to a temperature of 320 - 482°F (160 - 250°C).

Hardening (case hardening) tool steel 5120

Heat to a curing temperature of 1490 - 1544°F (810 - 840°C) and quench the material in oil or water (water is being used for simple shaped large components only) to a temperature of 320 - 482°F (160 - 250°C).

Quenching tool steel 5120

Quenching the 5120 quickly after carburizing will lock the added carbons into the surface. 

• Oil
• Water (for simple shaped large components)
• Salt bath

Tempering case hardening steel AISI 5120

Temper parts 1 hour per 25/32 inch (20 mm) thickness but a minimum of 2 hours at a temperature of 338 - 410°F (170 - 210°C). Tempering can relieve internal stresses that have been introduced during quenching the 5120.

Dimensional changes for case hardening steel 5120

Like any steel the 5120 will expand and contract during the heating and cooling processes. As carburizing steel involves high temperatures care has to be taken that the material does not distort during that process. 

Electrical Discharge Machining (EDM)

EDM is used for parts made from one individual piece, for cutting dies or when making intricate shapes. There are various methods to erode various materials, some of them are for example wire erosion, spark erosion or die sink erosion.

Surface treatment of tool steel 5120

Surface treatments can enhance wear resistance, corrosion resistance and surface hardness to extend tool and component lifes. Below is a selection of surface treatments for the 5120.

Carburizing tool steel 5120

Carburizing introduces a layer of carbon onto the surface, enhancing the wear resistance. The carbon should be distributed evenly to avoid weak spots in components or tools.

Hard chrome plating tool steel 5120

To increase results for wear and corrosion resistance this steel grade can be hard chrome plated.

Nitriding tool steel 5120

It is not usual to nitride 5120 in its hardened condition as it will result in a loss of hardness.

Machinability for tool steel 5120

5120 should be machined in its normalized condition and before it is case hardened.

Forging tool steel 5120

Forging should be done at a temperature range of 1922 - 1562°F (1050 - 850°C), then the material should be cooled slowly in the furnace.

Welding case hardening steel 5120

The 5120 has limited weldability. Welding should be done before the heat treatment. Preheat the part to 482 - 662°F (250 - 350°C), post heat treatment is based on the heat treatment of the base material.

Wear resistance of tool steel 5120

The wear resistance for tool steel 5120 is a 5 on a scale where 1 is low and 6 is high. 

Tensile strength for tool steel 5120

Tool steel 5120 has a tensile strength of approx. 104.4 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.

Working hardness for tool steel 5120

The working hardness for tool steel 5120 is at 601 - 627 BHN (58 - 60 HRC). 

Specific heat capacity of AISI 5120 tool steel

The specific heat conductivity for this steel grade is 0.475J/g-°C (0.113 BTU/lb-°F). This value shows how much heat is needed to heat 1lb of material by 1 Fahrenheit.

Continuous TTT-diagram of tool steel 5120

This diagram shows micro changes over time at different temperatures. Those are important during heat treatment as they show information about the optimum conditions for processes such as hardening, annealing and normalizing.

Isothermal TTT-diagram of tool steel 5120

This diagram shows the structural changes at micro level over time at a constant temperature. It shows at what temperature and after what time different phases, e.g., perlite, martensite or bainite start to build.

Steel Properties

Steel Density of tool steel 5120

Typically the density of tool steel 5120 is 0.284 lb/in3 (7.85g/cm3) at room temperature.

Thermal conductivity for tool steel 5120

The heat conductivity for tool steel 5120 is at 39.5 W/(m*K) (274 BTU/(h-ft*°F)) at room temperature.

Specific electrical resistivity for tool steel 5120

The following table shows the electrical resistivity of tool steel 5120.

Is tool steel 5120 a knife steel?

After proper heat treatment the 5120 has a good balance of hardness and strength to keep an edge and resist chipping. As the 5120 is not corrosion resistant it has to undergo thorough maintenance like regular cleaning, keeping it dry and maybe oiling the blade to prevent it from rusting. With that in mind the 5120 can be used for outdoor knives, cutlery knives or general purpose knives.

Conclusion

5120 has a good combination of strength, hardness and toughness. Due to those properties it is a great choice for applications with high stress and for applications that need good wear resistance. To give this tool steel even better wear resistance and/or enhance its corrosion resistance it can be surface treated to enhance tool service life. This steel grade can be hardened trough or case hardened which can both be useful for several different applications. 

Tool steel 5120 Datasheet

As a steel supplier we provide you with the datasheet for tool steel 5120 in PDF format.

Tool Steel alternatives or equivalent

Search for an alternative Tool Steel with the ABRAMS STEEL GUIDE®

It is possible with just one click to find an alternative or an equivalent steel grade!

We have the solution! (Registration is not needed).

Try it now - find an alternative steel grade and its properties in no time.