A8 mod. / Chipper Knife Steel - ~1.2360 - ~X48CrMoV8-1-1

Where can A8 mod. be used?

A8 modified chipper knives are often chosen for the combination of its wear resistance and toughness of the steel. Workpieces are exposed to forces like shock and impact as well as wear when e.g., chipping trees.

Here are a few applications A8 mod. steel is used for:

Punches, Dies and Forming Tools: Breaking and chipping while using the A8 mod. is prevented due to its good wear resistance and excellent toughness. At room temperature A8 mod. is easily formed / shaped as done for cold heading. The toughness of A8 mod. prevents punches and dies from splitting or cracking as well as deformation under pressure.

Knives, Blades and Cutting Tools: Shearing, slitting or cutting knives and blades need to have a good edge retention but have to handle some impact too. Again the wear resistance and toughness of A8 mod. lends itself for cutting tools, shear blades and slitter knives.

Is A8 mod. stainless steel / corrosion resistant?

Classic stainless steel has a minimum mass fraction 10.5% chromium, A8 mod. has a mass fraction of 7.8%. Therefore A8 mod. is not a classic stainless steel. 

To protect the A8 mod. from corrosion, parts should be covered in a protective coating.

Is  A8 mod. steel magnetizable?

In general, A8 is a ferromagnetic steel and can therefore be magnetized.

AISI A8 mod. Heat treatment

Following are the A8 modified tool steel heat treating steps.

A8 mod. Steel annealing

After hot work and before re-hardening, the material should be annealed.

Heat parts to no more than 400°F (222°C) per hour until a temperature of 1625°F (885°C) has been reached. Then hold the temperature for 1 hour per inch (25.4 mm) of thickness but no less than 2 hours minimum.

Finish the process by cooling the material down slowly in the furnace in steps of 20°F (10°C) per hour to 1200°F (649°C). Continue to room temperature in the furnace or air.

Normalizing A8 mod.steel

Normalizing is in general a process to refine the microstructure of the material. The result of the finer microstructure is an improved grain structure and improved mechanical properties.

The process of normalizing is not usually done for this material grade.

A8 mod. Steel stress relieving

To relieve stress, after rough machining, heat the workpiece to a temperature of 1200°F (650°C) and hold this temperature for 2 hours. Finishing the process with a slow cooling in the furnace.

A8 mod. Steel hardening

Preheat A8 mod slowly. In the first step to 752°F (400°C), then to 1202°F (650°C) and further to 1562°C (850°C). Continue to the austenitizing temperature of 1886-1958 (1030-1070°C) in a furnace or in salt and soak for 30 minutes for the first inch (25.4 mm) of thickness and 15 minutes for any further inch (25.4 mm) of thickness.

A8 mod. Steel quenching

Size alterations and / or distortion can be avoided by using the softest quenching medium possible. Quench immediately after hardening. When quenching in oil make sure to preheat the oil to a temperature of approx. 125 - 150°F (50 - 65°C).

• Hot bath (workpiece cooled down to approx. 1022°F (550°C))
• Air
• Pressure gas
• Oil, quench until black at approx. 900°F (482°C), then cool to 150-125°F (66-51°C) in still air

A8 mod. Steel tempering

A8 mod. workpieces should be tempered immediately after quenching at a temperature range of 300-600°F (149-316°C).

Hold for 1 hour per inch (25.4 mm) of thickness, but a minimum of 2 hours and cool in air to room temperature.

To double temper any workpieces use a temperature of 900°F (483°C) and over.

For material used for EDM or with a greater cross section of 6 inches (152.4 mm) a soaking time of 4-6 hours is strongly recommended.

A8 mod. Steel dimensional changes

Heat treatments, machining or forging may result in size changes but also phase transformation when quenching. Dimensional changes during high heat from creep as well as decarburization may occur. As a cold work tool steel care has to be taken during heat treatment to avoid overheating and the right quenching medium as well as the quenching method should be considered. To lessen inner stresses pre- and post heating the material is advised.

A8 mod. steel sub-zero treatment

Sub-zero treatment can increase the wear resistance of the A8 mod. as well as improve the dimensional stability and toughness. 

A8 mod. Electrical Discharge Machining (EDM)

EDM can be used for A8 mod. even though the material can be extremely hard at times. As for other material grades EDM can be used for intricate shapes and as there is no physical contact with the material there are no more mechanical forces applied. EDM is a good choice for parts needing a tighter tolerance or better surface finish. The recast layer has to be removed, if this is not done it might affect the lifespan and performance of the parts.

A8 mod. Steel surface treatment

A8 mod. Steel nitriding

By introducing nitrogen into the surface, the hardness and wear resistance is improved and the length of time part can be used is expanded.

A8 mod. Steel carburizing

This process introduces additional carbon into the surface. By quenching and tempering the material after carburizing the surface layer will be hard and the core stays tough.

A8 mod. steel carbonitriding

Carbonitriding A8 mod. introduces carbon and nitrogen into the surface which in turn gives the material a harder surface, better wear resistance and longer service for workpieces.

A8 mod. Black oxide coating

Most often done as a decorative finish, coating the material in a black oxide layer provides a measure of corrosion resistance too.

A8 mod. PVC and CVD coating

To reduce friction and improve the wear resistance, A8 mod. is coated by PVC (Physical Vapor Deposition) or CVD (Chemical Vapor Deposition). Both processes introduce a thin film of material onto the surface of the workpieces.

A8 mod. Steel machinability

Care should be taken when machining A8 mod. tool steel. As an air hardening steel removing material should be done swiftly. Machining can produce significant heat and consequently material might harden while being worked.

As A8 mod. is a very hard material that may need specialized tools to machine it. The high wear resistance means that tools might need to be changed or sharpened more often.

Forging A8 mod. steel

Slowly heat the parts to a temperature of 1202-1256°F (650-680°C) and then increase the temperature uniformly to 1922-2120°F (1050-1100°C). Forging should be done above the temperature of 1832°F (1000°C) but should never be dropped below 1652°F (900°C). Work pieces should be cooled slowly to avoid possible cracking.

Welding A8 mod. steel

A8 modified chipper steel is generally not suitable for welding.

A8mod. Steel wear resistance

The steel composition of A8 mod. contains alloys such as chromium, molybdenum and vanadium which all enhance the wear resistance of this steel grade. Apart from the aforementioned alloys, A8 mod. contains a high carbon content giving it a high hardness. 

A8 mod. Steel tensile strength

A8 mod. has a tensile strength of approx. 123.2 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.

A8 mod. Steel yield strength

The yield strength shows how much stress can be applied to a material before it plastically deforms. Before this point it will return to its original form as soon as the stresses have been taken off the material. When the point has been passed it will be deformed permanently or even break.

A8 mod. Steel working hardness

The working hardness for the A8 mod. is in the range of 469 - 627 BHN (50 - 60 HRC).

A8 mod. Steel specific heat capacity

The specific heat capacity of A8 mod. at room temperature is 0.460J/g-°C (0.110BTU/lb-°F). This value shows how much heat is needed to heat 1lb of material by 1 Fahrenheit.

A8 mod. Steel continuous TTT-diagram

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.

A8 mod. Steel Properties

Cold work Steel A8 mod.

The working temperature of the A8 mod. steel allows a working temperature in the range of 68 - 932°F (20 - 500°C).

A8 mod. Steel Density

Typically the density of A8 mod. is 0.282 lb/in3 (7.8g/cm3) at room temperature. 

A8 mod. Thermal conductivity

The heat conductivity for A8 mod. is at 26.1 W/(m*K) (15090 BTU/(h-ft*°F)) at room temperature.

A8 mod. Steel thermal expansion coefficient

The following table shows expansion or contraction at various temperatures, which may be very important for high temperature works or when working with high temperature changes.

A8 mod. Steel specific elasticity 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.

A8 mod. Steel modulus of elasticity (Young’s Modulus)

The stress and strain modulus or modulus of elasticity (Young’s modulus) for A8 mod. is at 30457 KSI (210 GPa).

A8 mod. / Chipper knife steel

This steel grade is the best steel for wood chipper knives. To chip wood and other fibrous materials the knives and blades require toughness and wear resistance, both properties of the A8 mod. A knife or blade from A8 mod. steel is not used for everyday kitchen knives but used as industrial and heavy duty knives.

A8 mod. Datasheet

As a steel supplier we provide you with the datasheet for A8 modified steel in PDF format.

A8 mod. Steel Equivalent / Alternatives

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