ThePipingMart Blog Grades A4 Tool Steel – Composition, Properties and Uses

A4 Tool Steel – Composition, Properties and Uses

Tool Steel A4

Tool Steel A4 is a high-carbon, air-hardening tool steel that is widely used for industrial applications. It has excellent wear, heat, and corrosion resistance, making it an ideal choice for many manufacturing and machining processes. A4 Tool Steel is a high-carbon, high-chromium steel with excellent wear resistance and toughness. The composition of the SAE-AISI A4 steel includes high levels of carbon and chromium, which give it its exceptional properties. This steel is commonly used for cutting, punching, and shearing applications where resistance to wear and deformation is crucial. Due to its high hardness and ability to maintain an edge, A4 Tool Steel is preferred for making knives and industrial cutting tools. Additionally, UNS T30104 has good machining properties and can be hardened through heat treatment, making it versatile for various engineering applications. In this blog post, we’ll discuss the uses of Tool Steel A4 and its properties, such as corrosion resistance, heat resistance, heat treatment, and machining.

What Forms of A4 Tool Steel is Available at Piping Mart?

  • Nut
  • Bar
  • Bolt
  • Pipe
  • Screw
  • Tubing
  • Valves
  • Washers
  • Flanges
  • Fasteners
  • Electrodes
  • Stud Bolts
  • Sheet Plates
  • Pipe Fittings
  • Forged Fitting
  • Instrumentation Fittings

A4 Tool Steel Composition

Element Content (%)
C 0.95-1.05
Mn 1.80-2.20
Si 0.50
Cr 0.90-2.20
Ni 0.30
Mo 0.90-1.40
Cu 0.25
P 0.03
S 0.03

A4 Tool Steel Physical Properties

Properties Metric Imperial
Density 8.03 g/cm3 0.290 lb/in3

A4 Tool Steel Mechanical Properties

Properties Metric Imperial
Hardness, Rockwell C (as air quenched from 845°C, 61 HRC at 150°C temper, 60 HRC at 205°C temper, 59 HRC at 260°C temper, 58 HRC at 315°C temper, 57 HRC at 370°C temper, 56 HRC at 425°C temper, 54 HRC at 480°C temper, 53 HRC at 540°C temper, 50 HRC at 595°C temper, 40 HRC at 650°C temper.) 63 63
Bulk modulus (typical for steels) 140 GPa 20300 ksi
Machinability (based on carbon tool steel) 65% 65%
Shear modulus (typical for steels) 80.0 GPa 11600 ksi
Poisson’s ratio 0.27-0.30 0.27-0.30
Elastic modulus 190-210 GPa 27557-30457 ksi

A4 Tool Steel Equivalents

  • ASTM A681
  • FED QQ-T-570
  • UNS T30104

A4 Tool Steel Uses

Tool Steel A4 can be used in a variety of industrial applications, including cutting tools, dies, punches and forming tools. It is also often used in the production of knives and other sharp implements. It is typically used in applications where high wear resistance or toughness is required due to its combination of hardness and toughness.

A4 Tool Steel Uses in Industries

Automotive Industry

A4 tool steel is commonly used in the automotive industry for various applications such as engine components, transmission parts, and suspension systems. The high strength and wear resistance of A4 tool steel make it ideal for these demanding applications.

Aerospace Industry

The aerospace industry also utilizes A4 tool steel for its high strength and durability. It is commonly used in aircraft engines, landing gear components, and other critical parts that require excellent performance under extreme conditions.

Manufacturing Industry

In the manufacturing industry, A4 tool steel is used in a wide range of applications, such as moulds, dies, and cutting tools. Its hardness and wear resistance make it suitable for shaping and forming metal, plastic, and wood.

Oil and Gas Industry

Due to its corrosion resistance properties, A4 tool steel is often used in the oil and gas industry for components exposed to harsh environments. This includes drill bits, valves, pumps, and other equipment for drilling or extracting oil and gas.

Medical Industry

A4 tool steel is also commonly used in the medical industry for surgical instruments due to its high strength and ability to maintain sharp edges. It is also used in medical implants, such as joint replacements, due to its biocompatibility with the human body.

A4 Tool Steel Corrosion Resistance

Tool Steel A4 offers excellent corrosion resistance due to its high chromium content. This means that it can be used in applications with exposure to saltwater or other corrosive environments without fear of rusting or corroding quickly.

A4 Tool Steel Heat Resistance

Tool Steel A4 also has excellent heat resistance due to its high chromium content. This means that it can be exposed to extremely hot temperatures without losing strength or becoming brittle. This makes it ideal for applications that require exposure to extreme temperatures, such as welding or drilling processes.

A4 Tool Steel Heat Treatment

Heat treatment is an important part of using Tool Steel A4 properly. To achieve optimal performance from the steel, it should be hardened by heating it to temperature and then quenching it in oil or water before tempering it at a low temperature until desired hardness is achieved. Different levels of hardness can be achieved depending on the tempering temperature used, which affects the amount of retained austenite present within the steel structure.

A4 Tool Steel Machining

Machining Tool Steel A4 requires special techniques due to its hard nature, so it may not be suitable for all types of operations. For example, when drilling holes larger than 12mm in diameter, carbide drills should be used instead of conventional HSS drills as they will provide longer life when drilling through hard materials like tool steel. When turning parts from tool steel, extra slow speeds and feeds should be employed along with sharp cutting tools, as these will help increase tool life and reduce stress on the machine being used during the production process.


In conclusion, Tool Steel A4 is an excellent choice for many industrial applications due to its combination of properties such as wear resistance, heat resistance, corrosion resistance, and machinability. While it does require special techniques when machining compared to softer steels such as carbon steel, these techniques are well worth learning if you frequently use this type of steel in your work. With proper care and maintenance, Tool Steel A4 can offer years of reliable service while providing superior results compared to other materials. Understanding how best to use this material can maximize its potential benefits for your projects.    Intended Audience: Engineers & Manufacturers looking for information about tool steel a4 – potential uses & benefits, tips & tricks for machining & heat treating this type of material.

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