What is the difference between tool steel and regular steel?

Author: May

Mar. 07, 2024

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Tags: Minerals & Metallurgy

There are six different categories of tooling steel including; cold-work, water-hardened, hot-work, high-speed, shock-resisting, and special purpose tool steels. Below are the classification of tool steel and their application.

1. Cold-Work Tool Steel

This is one of the major types of tool steel. It is tough, hard, and wear-resistant in cold environments with temperatures below 200ºC. However, cold-work tool steel does not perform well when exposed to hot environments.

Besides, cold-work steel has high machinability. This is due to the presence of graphite and the lubrication it provides. What’s more, the most commonly used tool steel grades in this category include; D2, O2, A2, D3, and D6.

These are the different subcategories of cold work tool steel.

1.1 High Carbon Chromium or D Series Grade Tool Steel

This cold-working tool steel is also known as stainless due to its high chromium content and contains 11-13% chromium. Although they have limited corrosion resistance, their 1.4-2.5% carbon content gives them a high abrasion resistance. It also enables them to function at temperatures as high as 425ºC.

Besides, their ability to undergo oil or air quenching with minimal distortion gives this tool steel application in making cutters. It also makes the D series tool steel ideal for making seaming and forming rolls, plastic injection molds, lathe centers, and woodworking knives. Its other applications include making burnishing tools, lamination dies, draw punches as well as cold extrusion dies.

1.2 Air Hardening or A Series Grade Tool Steel

These types of tool steel have a carbon content of 0.05-2.85% and up to 5% chromium content. Furthermore, this grade of tool steel is very tough with high wear resistance. Common applications include coining, embossing, blanking, and blending dies.

1.3 Oil Hardening or O Series Grade Tool Steel

Quenched by oil during production, this series of tool steel has a carbon content ranging between 0.85-2.00%. They are also tough with have high abrasion resistance. The applications of Oil hardening tool steels include making bushings, collets, gauges, master engraving rolls, punches, and chasers for thread cutting.

2. Water-Hardened Tool Steel

This category of tool steel contains heat-treated carbon steel. Produced at low-cost and water-quenched, water-hardened tool steel has a carbon content ranging between 0.5-1-5%. The high carbon content of water-hardened steel makes them brittle and hard. However, it is low on other alloying metals like tungsten, nickel, or molybdenum, usually less than 0.5%.

3. Hot Work Tool Steel

The types of tool steel in this category usually have a carbon content of less than 0.6%. However, they contain a greater percentage of other alloying elements. This enables them to keep their characteristics and work optimally even at extreme temperatures up to 540ºC due to the creation of more carbides.

The high-temperature resistance of hot work tool steel makes it ideal for use in manufacturing materials like metal and glass that require high temperatures for optimal malleability.

Additionally, one benefit engineers derive from using tool steel under this category is their continued functionality, even after exposure to extended heat. The most commonly used tool steel in this category is the H13.

Based on the percentage of alloying elements used, there are three main alloy elements in this category: molybdenum, and chromium.

3.1 Molybdenum-type Tool Steel

This is a hot work tool steel that has a high molybdenum content. Furthermore, this type of tool steel has high wear resistance and heat stability, especially in situations of extreme temperature. What’s more, their ability to handle force and heat gives Molybdenum-type tool steel applications in metal mills as cutters or dies.

3.2 Tungsten-type Tool Steel

This type of tool steel contains 9-18% tungsten and 2-4% chromium. Tungsten hot work tool steel although brittle, it has excellent heat resistance. Furthermore, one way to circumvent the brittleness of this tool steel is preheating it to operating temperature before use.

3.3 Chromium-type Tool Steel

The Chromium type is the most used hot work tool, containing 3-5% chromium. They could also contain below 5% of other alloying elements like molybdenum, tungsten, or vanadium. Common applications of chromium-type tool steel, include hot forging, hot working punches, and plastic injection mold.

4. High-Speed Tool Steel

High-Speed tool steel contains many elements, including 0.6% carbon, 3-5% chromium, and 14-18% tungsten. Furthermore, the invention of this category of tool steel is partly responsible for ushering in the era of modern production. Before the invention of high-speed tool steels, when cutting tools and machines worked for long periods, their efficiency decreased due to friction. However, with this tool steel, cutting tools and edges keep working efficiently, performing at optimal speeds.

Common applications of high-speed tool steel include the production of power-saw blades, milling cutters, router bits, gear cutters, and drill bits. The M2 high-speed tool steel is the most common in this category.

5. Shock Resisting Tool Steel or S Grade Steel

Developed to have high-level impact resistance, shock-resisting tool steels are remarkably strong. Furthermore, this tool steel’s strength is due to its high toughness value and low carbon content. This tool steel category contains alloying elements found in other categories, as well as 0.15-3% silicon.

Although this steel does not have optimal abrasion resistance, it has excellent resistance to shock regardless of temperature. Besides, these properties make S-grade tool steels ideal for producing jackhammer parts, blacksmith chisels, and clutch parts.

In addition, its other applications include hot stamps, pneumatic tools, chipper knives, cold and hot working chisels, hot forming dies, and cold gripper dies. The S7 tool steel is the most popular in this category.

6. Plastic Mold or Special Purpose Tool Steels

These are tool steels like an excellent mix of toughness, corrosion, hardness, and resistance to wear and tear. Furthermore, tool steel under this category also has high impact strength and is easy to polish.

Besides, plastic mold tool steels are ideal for companies that use the processes of extrusion and injection molding to produce plastic. Using this tool steel for making molds ensures tool durability and reliability.

Also, they are tool steels created for special purposes. And Like the water-hardened tool steel, these ones are water quenched. Tool steels in this category contain high-iron steels, while other alloying elements are either absent or present in minute quantities. Adding other alloying elements sparingly helps improve the mechanical properties of this tool steel while ensuring it is not as expensive as other tool steels.

An instance of special-purpose tool steels is the low-carbon mold steels used in thermoplastic molding. This specially crafted mold steel does not require high impact resistance but excellent wear resistance and heat tolerance. In common, the P20 is the most popular used tool steel in this category.

WHAT IS TOOL STEEL?

Tool steel encompasses a wide variety of carbon and alloy steels that have particular mechanical or physical properties, such as strength, hardness, workability, abrasion, corrosion and heat resistance.

This makes them well suited to be made into tools, essentially used in the shaping of other materials, and especially for drilling and cutting as they are able to hold a cutting edge at elevated temperatures.

Tool steels contain differing amounts and combinations of tungsten, molybdenum, cobalt and vanadium.

 

What is the difference between tool steel and regular steel?

TOOL STEEL: A COMPREHENSIVE GUIDE

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