4140 / 4142 Heat-Treatable Steel - 1.7225 - 42CrMo4 - ~SCM 440

What is the difference between 4140 and 4142 steel?

4140 and 4142 are nearly identical but for a slightly higher carbon content for the 4142. Where the steel composition of the 4140 has a carbon content of 0.38 to 0.43%, 4142 has carbon content of 0.4 to 0.45%. 

What is 4140 / 4142 steel used for?

Applications for this 4140 / 4142 flat stock steel include: arbors, flanges, collets, bending dies, crankshafts, clutch parts, forming rolls, and short run stamping dies.

Is 4140 / 4142 steel stainless?

4140 / 4142 is, even with a chromium and molybdenum content, not a classic 10.5% chromium stainless steel. It belongs to the group of high grade structural steels.

Is 4140 / 4142 corrosion resistant?

On a scale where 1 is low and 6 is high, the corrosion resistance for 4140/4142 stands at 2.
4140 / 4142 has some corrosion resistance due to the chromium and molybdenum content but will rust when corrosion has set in.

Is 4140 magnetizable? 

4140 / 4142 steel is magnetizable.

4140 / 4142 Heat treating

4140 / 4142 can be heated to 1580°F (860°C) and quenched in oil. The material can be normalized and tempering can achieve a good range of properties.

4140 / 4142 Annealing

Uniformly heat the work pieces to 1256-1328°F (680-720°C), followed by a slow cooling in the furnace to reach the annealed hardness of approx. 217 BHN. 

Stress relieving

4140 / 4142 should be heated to 1100-1300°F (593-705°C), held at that temperature for 2 hours and then the work pieces are cooled in air. 

Normalizing

This steel grade can be normalized before hardening. Heat to 1544-1616°F (840-880°C), followed by air cooling.

4140 / 4142 Hardening

To harden 4140 the material should be heated slowly and uniformly to 1508-1580°F (820-860°C) followed by water or oil quenching, depending on  the size and complexity of the work pieces. After hardening the material can achieve a working hardness between 262 and 456 BHN (27 - 48 HRC).

4140 / 4142 Quenching

4140/4142 can be quenched in oil to room temperature and then should be tempered  immediately.

4140 / 4142 Tempering temperature

4140 / 4142 can be tempered at 1004 - 1256°F (540 - 680°C), the higher the tempering temperature the softer and more ductile it gets. In general hardness and ductility are determined by tempering the material, the higher the ductility the lower the hardness which is true for the reverse as well. Apart from the advantage to give the steel the wanted and needed properties the material can be stress relieved, is less likely to crack and has a better deformation behavior by tempering it. 

4140 / 4142 Tempering

Alloy 4140 / 4142 can be tempered at 1004-1256°F (540-680°C) subject to hardness and according to the properties required. Cool in air after the treatment. 

4140 / 4142 Machining allowance / Dimensional changes

4140 / 4142 has a creep resistance up to a temperature of 1004°F (540°C) and is able to sustain its properties  when exposed to relatively high working temperatures over a longer time.

4140 / 4142 Electrical Discharge Machining (EDM)

It is possible to EDM this steel grade in the annealed and hardened condition. As for all EDM work the recast layer has to be removed thoroughly by stoning and polishing.

Can 4140 / 4142 be nitrided?

4140 / 4142 can be nitrided to give this steel grade a harder surface layer.

4140 / 4142 Machinability

This grade is easily machinable after it has been heat treated to produce the microstructure required for the best machinability.

Can 4140 / 4142 be forged?

4140 / 4142 can be forged in a temperature range of 1652 - 1832°F (900 - 1000°C) followed by a very slow cooling in still air or sand.

42CrMo4 weldability?

Welding may only be done in the annealed or normalized condition, which can then be done by all the conventional techniques. In order to prevent cracking, preheat to 350-650°F (177-350°C). Due to the level of carbon in this steel, pre- and post-heat is recommended. Cool slowly to prevent/reduce embrittlement. If welded in the heat-treated condition, which is normally only done for repairs, mechanical properties are affected and a post-weld heat treatment should be performed. Welding pre-heated parts, it is recommended to stress relieve the parts before at a temperature 60°F (15°C) below the original tempering temperature in order to prevent cracking.

4140 / 4142 Wear resistance

On a scale where 1 is low and 6 ist high, 4140 / 4142 comes in at a score of 3.

4140 / 4142 Tensile strength

4140 / 4142 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.

4140 / 4142 Yield strength

The yield strength of 4140 / 4142 is at approx. 95 KSI. This shows when the material starts to show  plastic deformation.

4140 / 4142 Working hardness

The working hardness for this material grade is in a range of 262 - 456 BHN (27 - 48 HRC (Rockwell hardness))

4140 / 4142 Specific heat capacit

This value shows how much heat is needed  to heat 1lb of 4140 / 4142 by 1 Fahrenheit.

4140 / 4142 Continuous time-temperature-transformation-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.

4140 / 4142  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.

4140 / 4142 Steel Properties

Hot working

This steel can be hot worked at 1500-1900°F (816-1038°C), it maintains its properties even after long exposure at the high working temperatures.

Cold work

In its annealed condition, this steel can be cold worked with all the conventional methods.

4140 / 4142  Steel density

The density of 4140 / 4142 at room temperature (~68°F) is 0.284lb/in3 (7.85g/cm3).

Thermal conductivity of 4140 / 4142 Steel

The heat conductivity for 4140 / 4142 at room temperature is at 42.6 W/(m*K) (313 BTU/(h-ft2*°F))

Heat conductivity teable

Value	By temperature
42.6 W/(m⋅K)	68 °F

 
4140 / 4142 Thermal expansion coefficient

This diagram shows how much 4140 / 4142 might expand or contract when the temperatures change which can be very important when working with high temperatures or strong temperature changes.

4140 / 4142 Specific electrical resistivity

You can find the temperature dependent material constant (Resistivity) in the following table. The electrical conductivity is the reciprocal value of the specific resistance.

(*) 1 Ω m = 0,0254 Ω inch

4140 / 4142 Modulus of elasticity (Young's Modulus)

The relationship between stress and strain of steel is described in the modulus of elasticity (Young’s Modulus) and can be found in the table below with the according values and temperatures.

Is 4140 / 4142 a knife steel?

When choosing to make a knife or blade from 4140 / 4142 the hardness and corrosion resistance as well as wear resistance should be considered. Though possible this steel grade is not commonly used to make knives with. 

4140 / 4142  Datasheet

As a steel supplier we provide you with the datasheet for 4140 / 4142 in PDF format.

4140 / 4142 Steel alternatives

With our patented ABRAMS Steel Guide, you are able to find an equivalent or an alternative to the  4140 / 4142 or a compatible steel and its properties in no time. 

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