Tool steel is a vital material used in the manufacturing of high-performance tools and machinery parts that must withstand extreme conditions such as high temperatures, abrasion, and wear. Known for its hardness, toughness, and heat resistance, tool steel is used in applications ranging from cutting tools and dies to molds and industrial machinery. This blog explores the various types of tool steel, their properties, and their significance in industrial manufacturing processes.

If you are looking for more details, kindly visit Youngson.

What is Tool Steel?

Tool steel is a type of carbon and alloy steel that is specifically designed to produce tools that are used for cutting, shaping, and forming materials. Its composition includes a combination of elements like tungsten, molybdenum, chromium, vanadium, and cobalt, which give the steel unique properties such as high hardness, wear resistance, and the ability to retain shape under high temperatures.

Types of Tool Steel:

1. Water-Hardening Tool Steel (W-Grades):

• This is the most basic form of tool steel and is known for its low cost and high wear resistance.
• Used in applications such as cutting tools, chisels, and punches that require hardness but operate at low temperatures.

2. Cold-Work Tool Steel (O, A, D-Grades):

• Designed for cutting and shaping at room temperature, cold-work tool steels are extremely hard and wear-resistant.
• Commonly used in dies, shear blades, and cutting tools for industrial applications.

3. Hot-Work Tool Steel (H-Grades):

• These steels are designed to retain their strength and hardness at high temperatures, making them ideal for hot-forging, die-casting, and extrusion tools.
• Known for excellent toughness, hot-work tool steels are used in molds for casting and forging.

4. High-Speed Tool Steel (T, M-Grades):

• High-speed tool steel is designed for high-performance tools that need to operate at high speeds without losing their hardness.
• Used in the production of drills, milling cutters, and other cutting tools that experience extreme heat and wear during operation.

5. Shock-Resistant Tool Steel (S-Grades):

• Specifically engineered to absorb impact and resist shock, this type of tool steel is used in tools like hammers, chisels, and punches.
• It is designed to handle sudden impacts without breaking or chipping.

Key Benefits of Tool Steel:

1. Hardness and Wear Resistance:

Tool steel is known for its exceptional hardness, which allows it to cut and shape other materials effectively. This hardness also ensures excellent wear resistance, meaning that tools made from tool steel last longer and maintain their sharpness even after extensive use.

2. Heat Resistance:

Tool steel can withstand high temperatures without losing its structural integrity, making it ideal for applications where heat exposure is constant, such as in forging and die-casting tools.

3. Toughness and Impact Resistance:

Many types of tool steel are designed to be tough, allowing them to absorb impact and resist chipping or breaking during heavy-duty applications. This toughness is critical in tools like punches and hammers that experience sudden force.

4. Dimensional Stability:

Tool steel retains its shape and size even after repeated exposure to high temperatures and stress. This stability is crucial for precision tools used in manufacturing, where maintaining exact dimensions is essential for product quality.

Applications of Tool Steel:

1. Cutting Tools:

Tool steel is extensively used in the manufacturing of cutting tools such as drills, saw blades, milling cutters, and lathe tools. High-speed steel (HSS) is particularly valuable in this application due to its ability to maintain hardness at high cutting speeds.

2. Molds and Dies:

Hot-work tool steels are commonly used to manufacture molds and dies for casting, forging, and extrusion processes. These tools need to endure high temperatures and wear while maintaining dimensional accuracy, making tool steel the ideal material.

3. Punches and Chisels:

Shock-resistant tool steel is used to produce punches, chisels, and other tools that need to absorb impact without breaking or deforming. This property is especially important in heavy-duty applications like metal forming and fabrication.

4. Industrial Machinery:

Tool steel is also used in various components of industrial machinery that require high strength, toughness, and resistance to wear. This includes machine parts, gears, and fixtures that are subject to extreme conditions during manufacturing operations.

5. Automotive and Aerospace Industries:

In both the automotive and aerospace sectors, tool steel is used in the production of components that must withstand high temperatures and stresses, such as engine parts, turbines, and transmission components.

Grades of Tool Steel:

• W-Grades (Water-Hardening): Cost-effective with high hardness but limited to low-temperature applications.
• O, A, D-Grades (Cold-Work): Superior wear resistance for tools used in cold environments.
• H-Grades (Hot-Work): Excellent for tools exposed to high temperatures and thermal cycling.
• T, M-Grades (High-Speed): Ideal for tools that operate at high cutting speeds, offering hardness retention at elevated temperatures.
• S-Grades (Shock-Resistant): Built to absorb impact and prevent breaking under sudden forces.

Global Demand for Tool Steel:

The demand for tool steel is growing globally due to its wide range of applications in industries such as manufacturing, automotive, aerospace, and construction. As industries continue to innovate and develop new technologies, the need for durable, heat-resistant, and wear-resistant materials like tool steel is becoming more prominent. Additionally, the growing trend toward automation in manufacturing processes has further driven the demand for precision tools made from high-quality tool steel.

Sustainability and Recyclability

If you are looking for more details, kindly visit High-Performance Alloy Tool Steel.

Tool steel is a highly recyclable material, making it a sustainable choice for manufacturers looking to reduce waste and environmental impact. The durability and long service life of tools made from tool steel also contribute to sustainability by reducing the need for frequent replacements.

Conclusion

Tool and high-speed steels

Tool steels are used for working, cutting, and forming metal components, moulding plastics, and casting dies for metals with lower melting points than steel. Accordingly, tool steels need high hardness and strength combined with good toughness over a broad temperature range.

The microstructure of all tool steels is based on a martensitic matrix. Molybdenum additions in tool steels increase both their hardness and wear resistance. By reducing the critical cooling rate for martensite transformation, molybdenum promotes the formation of an optimal martensitic matrix, even in massive and intricate moulds that cannot be cooled rapidly without distorting or cracking. Molybdenum also acts in conjunction with elements like chromium to produce substantial volumes of extremely hard and abrasion resistant carbides. Increasing physical demands on tool steels result in an increasing molybdenum content. Depending on their application, tool steels are classified into:

• Cold-work tool steels (Mo ≤1.8%)
• Hot-work tool steels (Mo ≤3.0%)
• Plastic mould steels (Mo ≤1.3%)
• High-speed tool steels (Mo ≥7%)

AISI-SAE tool steel grades Defining property AISI-SAE grade Significant characteristics Water-quenched W Molybdenum alloying optional Cold-working O Oil-hardening, O6-0.3% molybdenum, cold-work steel used for gauges, cutting tools, woodworking tools and knives A Air-hardening, low distortion during heat treatment, balance of wear resistance and toughness, all molybdenum alloyed - 0.15-1.8% D High carbon, high chromium, 0.9% molybdenum, very high wear resistance but not as tough as lower alloyed steels Hot-working H H1-H19 - chromium base
H20-H39 - tungsten base
H40-H59 - molybdenum base Plastic moulding P Low segregation: reduced alloying of silicon, manganese and chromium
Through hardenability: increased molybdenum and vanadium High-speed T Tungsten base (today mostly replaced by M22) M Molybdenum base Shock resisting S Chromium-tungsten, silicon-molybdenum, silicon-manganese alloying, very high impact toughness and relatively low abrasion resistance Special purpose L Low alloy, high toughness F Carbon-tungsten alloying, substantially more wear resistant than W-type tool steel Typical alloying elements in tool steels and their effects Alloying element Advantages Disadvantages Chrome (Cr) Hardenability, corrosion resistance, wear resistance Lower toughness, poorer weldability Cobalt (Co) Heat resistance, temper embrittlement - Manganese (Mn) Hardenability, strength Thermal expansion Molybdenum (Mo) Hardenability, tempering resistance, temper embrittlement, strength, heat resistance, wear resistance - Nickel (Ni) Yield strength, toughness, thermal expansion - Nitrogen (N) Stress corrosion cracking resistance, work hardening, strength Blue brittleness, aging sensitivity Vanadium (V) Wear resistance, tempering resistance -

Cold-work steels

Cold-work tool steels are tool steels used for forming materials at room temperature or at slightly raised temperatures (~ 200°C). Specifically, tools for blanking metallic and non-metallic materials, including cold-forming tools, are manufactured from these steels.

Fundamentally, cold-work tool steels are high carbon steels (0.5-1.5%). The water-quenched W-grades are essentially high carbon plain carbon-manganese steels. Steel grades of the O series (oil-hardening), the A series (air-hardening), and the D series (high carbon-chromium) contain additional alloying elements that provide high hardenability and wear resistance as well as average toughness and heat softening resistance. 

The four major alloying elements in such tool steels are tungsten, chromium, vanadium, and molybdenum. These alloys increase the steels' hardenability and thus require a less severe quenching process with a lower risk of quench cracking and distortion. All four elements are strong carbide formers, also providing secondary hardening and tempering resistance.

Hot-work steels

Hot-work tool steels are tool steels used for the shaping of metals at elevated temperatures. Their principal areas of application include pressure die casting moulds, extrusion press tools for processing light alloys, and bosses and hammers for forging machines. The stresses encountered here are cyclical, often with abrupt temperature changes and recurring mechanical stresses at high temperatures. Hot-work steels must constantly endure tool temperatures above 200°C during use. To achieve optimum performance, hot-work tool steels require the following properties: 

• Good tempering properties
• Sufficient thermal stability
• High hot toughness
• High resistance to wear at elevated temperatures
• Good thermal fatigue resistance

Cycle times applied in plastic injection moulding, pressure die casting or press hardening (hot stamping) can be reduced considerably by increasing the tool steel’s thermal conductivity, which significantly raises productivity. Heat conductivity is influenced by several material parameters such as microstructure, defects, and alloying elements. 

Armco iron is nearly pure iron with a low defect density and high heat conductivity in the order of 70-80 W/mK. Compared to Armco iron, traditional hot-work steel such as H13 (1.) has much lower heat conductivity  in the range of only 20-30 W/mK. This reduced thermal conductivity is due to high lattice distortion and defect density of the (tempered) martensitic microstructure as well as to a substantial content of alloying elements. All these characteristics interact with phonons, electrons, and magnons as the “vehicles” of heat transport.

Since all hot-work steels have a defect-rich martensitic microstructure, the difference in optimizing heat conductivity lies in the alloying composition. When in solid solution, alloying elements can cause local lattice distortion (size misfit vs. iron), modify the electronic structure, and/or have influence on magnetism. Generally, heat conductivity is reduced as the alloy content increases. Looking at individual elements in a solute state, nickel, chromium, and silicon were found to negatively influence heat conductivity. The effects of vanadium and molybdenum appear less detrimental. After tempering, the amount of solute vanadium, chromium, and molybdenum decrease by carbide precipitation, which diminishes their negative effect on heat conductivity.

Effect of alloying element on properties of hot-work steel Property Si Mn Cr Mo Ni V Wear resistance - - + ++ - ++ Hardenability + + ++ ++ + + Toughness - ± - + + + Thermal stability + ± + ++ + ++ Thermal conductivity -- - -- ± - ±

Plastic mould steels

Tools for processing plastics are mainly stressed by pressure and wear. According to the type of plastic, corrosive conditions can prevail in addition to stresses. The type of plastic and processing method define the key requirements in addition to those generally valid to hot-work steels:

• Economic machinability or cold-hobbing ability
• Smallest possible distortion upon heat treatment
• Good polishing behavior
• High compressive strength
• High wear resistance
• Sufficient corrosion resistance

High-speed steels

When tool steels contain a combination of more than 7% molybdenum, tungsten, and vanadium, and more than 0.60% carbon, they are referred to as high-speed steels. This term describes their ability to cut metals at “high speeds”. Until the s, T-1 with 18% tungsten was the preferred machining steel. The development of controlled atmosphere heat treating furnaces then made it practical and cost effective to substitute part or all the tungsten with molybdenum.

Want more information on Hiperco 50A alloy supplier? Feel free to contact us.