5115 Case Hardening Steel - 1.7131 - 16MnCr5 - SAE 5115

What is 5115 steel used for?

The 5115 case hardening steel is often used in the automotive industry but also for bearings, gears, machine parts, fasteners and many more. It can withstand stress and wear due to the hard surface and tough core.

Is the AISI 5115 a stainless steel?

Stainless steel has a mass fraction of 10.5% of chromium which makes it a corrosion resistant steel. The 5115 has a mass fraction of 0.8 - 1.1% and is therefore not a corrosion resistant steel. The chromium content in this grade enhances the hardenability and wear resistance of this material grade. When corrosion resistance is a high priority it would be advisable to use a steel grade with a higher chromium content like a stainless steel.

Is  the SAE 5115 magnetizable?

As a ferromagnetic steel the 5115 can be magnetized.

Heat treatment for the 5115 steel

Annealing 5115 steel

Heat the material uniformly to a temperature of 1202 - 1292°F (650 - 700°C) and soak for 2 - 5 hours. Cool slowly in the furnace followed by further cooling in air.

Normalizing 5115 steel

Heat the parts uniformly to a temperature of 1562 - 1616°F (850 - 880°C), then cool in air.

Cooling the material fast will refine the grain structure and give it a more even and fine pearlitic structure. This improved structure improves the AISI 5115 steel's mechanical properties. 

Intermediate thermal treatment for 5115 steel

Heat to a temperature of 1202 - 1292°F (650 - 700°C) for about 2 - 4 hours with a slow cooling in the furnace.

The intermedial heat treatment promotes an amalgamation of micro structures e.g., a softer ferrite making the steel more formable coexisting with a harder martensite for strength.

Hardening 5115 steel (core hardening)

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).

Hardening 5115 steel (case hardening)

Heat to a curing temperature of 1436-1508°F (780-820°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). After this process the material/parts have a hard, wear resistant surface layer with a relatively tough core which is able to absorb impact stresses without breaking.

Quenching 5115 steel

Quenching, the 5115 case hardening steel, achieves the desired properties for this grade. Typically oil is used as the quenching medium, it provides a cooling rate that may help to reduce cracking and warping.

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

Tempering 5115 steel

Temper parts for 1 hour per 25/32 inch (20 mm) of thickness but a minimum of 2 hours at a temperature of 302-392°F (150-200°C). The tempering temperature depends on the desired strength. The higher the tempering temperature the softer hardened steel turns. To avoid cracking, tempering should be done as soon as possible after hardening.

Dimensional changes 5115 steel

Based on the thermal coefficient expansion during heating and cooling phases are predictable. As this is a physical change the material will revert back to its former state.

Carburization, stress relief distortion, decarburization and phase changes may also lead to dimensional changes. To minimize or prevent these changes pre heating or post heating treatments should be considered as well as a controlled atmosphere during heat treatment.

5115 Steel sub-zero treatment

The 5115 can be treated in sub-zero temperatures. This will increase the hardness and wear resistance by transforming left austenite to martensite. This treatment might increase the risk of cracking and embrittlement if it is not done correctly and therefore the procedure should be done with the necessary care and consideration. 

5115 Steel 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.

Even if the 5115 is surface hardened EDM can be used on this material and gives the 5115 a smooth surface finish.

5115 Steel surface treatment

Nitriding 5115 steel

Nitriding introduces nitrogen into the surface of the material, this will give parts a harder surface but they will maintain a tough and ductile center.

As the 5115 will lose hardness, it is not usually nitrided in its hardened condition.

Carburizing

The material is heated to a temperature range of 1616-1796°F (880-980°C). To choose the right temperature it is important to consider the temperature, time, medium and equipment as well as the intended process and required microstructure. In general, carburizing takes place below 1742°F (950°C) during direct hardening. In special cases, carburizing temperatures up to 1832°F (1000°C) are used.

Carbonitriding 5115 steel

The parts are heated to the austenitic range and then the carbon and nitrogen diffused into the material. Carbonitriding will achieve a deeper case hardening depth compared to nitrocarburizing. This process increases the wear resistance and fatigue strength.

Nitrocarburizing 5115 steel

Nitrocarburizing also introduces carbon and nitrogen into the surface though in this process there is more nitrogen introduced than when carbonitriding. The case hardening depth is not as deep as for carbonitriding but it decreases corrosion and enhances appearance. Where carbonitriding may take a few hours to a few days, nitrocarburizing only takes a few hours.

5115 Steel machinability

Forging 5115 steel

Forging should be done at a temperature range of 2102-1562°F (1150-850°C). Overheating can result in grain growth and reduce mechanical properties. Do not let the forging temperature drop below 1562°F (850°C). Slowly cool the parts down to avoid possible stresses and unwanted microstructures.

Welding 5115 steel

5115 has limited weldability and should only 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 metal.

5115 Steel tensile strength

5115 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.

5115 Steel yield strength

The yield strength for this steel alloy is approx. at 50 - 70 KSI (345 - 490MPa).

5115 Steel working hardness

The working hardness for the SAE 5115 is 601 - 627 BHN (58 - 60 HRC) on the surface.

5115 Steel specific heat capacity

The specific heat conductivity for this steel grade is 0.470J/g-°C (0.112BTU/lb-°F). This value shows how much heat is needed to heat 1lb of material by 1 Fahrenheit.

5115 Steel continuous TTT-diagram

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.

5115 Steel isothermal TTT-diagram

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.

5115 Steel properties

5115 Steel hot work

5115 case hardening steel can be hot worked at a temperature range of 2012-1562°F (1100-850°C).

5115 Steel density

Typically the density of 5115 is 0.284 lb/in3 (7.85g/cm3) at room temperature.

5115 Steel thermal conductivity

The heat conductivity for 5115 is at 44 W/(m*K) (25440 BTU/(h-ft*°F)) at room temperature.

5115 Steel modulus of elasticity (Young’s Modulus)

The stress and strain modulus or modulus of elasticity (Young’s modulus) for 5115 is at 29000 KSI (200 GPa).

Conclusion on the AISI 5115 steel

AISI 5115, also known as the 16MnCr5 or 1.7131 steel, has a balance of strength, toughness and machinability making it a good choice in many industries. A wide range of properties can be achieved by heat treating the 5115.

Its wear resistance makes it useful in applications with a lot of friction like for shafts, gears or joints. The AISI 5115 has the strength and toughness to withstand shock and impact as needed for axles, bearings, or gears. It is easily machinable, weldable and formable so makes it a good choice when the 5115 steel hardness is needed and the application demands a good toughness at the same time.

5115 Steel Datasheet

As a steel supplier we provide you with the datasheet for 5115 steel in PDF format.

5115 Steel alternatives and eqivalents

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