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.
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.
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.
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.
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.
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%.
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.
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.
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.
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.
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.
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.
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.
Alloy steel is a steel type containing more than one alloying element. Whenever you add each element often introduces new characteristics or improves certain material properties. Generally, all basic steel has iron content and a small percentage of carbon. Chromium is a common alloying element that manufacturers add to other elements to enhance corrosion-resistance properties.
Other common elements suitable with alloy steel are vanadium, nickel, manganese, molybdenum, titanium, and tungsten. The specific elements added to the alloy steel often determine its properties. For instance, manganese improves ductility, wear resistance, and alloy steel’s hardenability. On the other hand, chromium enhances alloy steel’s toughness, hardness, and resistance to wear.
Here are the categories under which alloy steel types are classified:
These alloy steels usually contain a high amount (more than 5% of the total composition) of one or more alloying elements for excellent toughness, hardness, and strength. Common alloying elements for this alloy steel category include manganese, chromium, vanadium, nickel, and molybdenum. Stainless steel is a perfect example of high-alloy steel, containing a minimum of 12% chromium, depending on its grade.
Low-alloy steels contain a lower portion of one or more alloying elements (maximum of 5% of the total composition), offering improved toughness, strength, hardness, or other qualities. Typical examples of alloying elements in this category include tungsten, molybdenum, copper, chromium, manganese, boron, and nickel. Further, typical applications for low-alloy steels include mining and construction equipment due to their high requirement for good strength-to-weight ratios properties.
These steels are famous for their superior toughness and strength. Manufacturers find a use for these steels in applications that require high-strength properties, including military and aerospace applications.
Tool steels are commonly known as highly alloyed steel suitable for tool and die applications in particular. Tool steels can resist wear and hardness even when exposed to high temperatures.
Alloy steels offer certain benefits over stainless steel, making it a material worth considering for various applications. Here are some of these advantages:
Stainless steel is an alloyed steel with a minimum of 10.5% chromium. The chromium element offers stainless steel greater corrosion resistance, making it compatible with extensive applications ranging from medical equipment to cookware. In addition, it is a common choice for consumers and businesses due to its unique features. However, it would help to note that stainless steel has different grades with varying sets of qualities.
Although there are thousands of stainless steel grades, they can be successfully grouped into the following categories:
The austenitic steels usually contain 8-20% nickel and 17-25% chromium at minimal (the basic stainless 304 contains 18% chromium and 8% nickel). These steel grades are usually non-magnetic, and manufacturers use them in food processing equipment and chemical plants due to their high resistance to rust, stain, and corrosion after exposure to water.
Austenitic grades offer excellent corrosion resistance, toughness, ductility, weldability, and high formability. This group’s good examples of stainless steel include 253, 304/304L, and 316/316L.
This category of stainless steel contains between 14 -18% chromium and balanced levels of carbon within the 0.2 and 2% range. You can temper and harden martensitic stainless steel like carbon steel. Likewise, they offer reduced ductility and low weldability. Typical examples are 431, 420C, and 431 stainless steel grades.
The ferritic group contains a portion of chromium, typically between 11- 27% and less or no nickel. This group’s steel is less corrosion-resistant than austenitic stainless steel due to its high amount of chromium. They share certain qualities with iron and show improved mechanical properties at high temperatures, and you can strengthen these steels through annealing.
However, ferritic stainless steels lack toughness which reduces their structural applications. They are only available in coil and sheet. Stainless steel 430 and 409 are apt examples.
Duplex stainless steels have chromium between 18 and 28% and nickel alloying elements between 3.5 and 5.5%. Stainless steel in this grade possesses equal parts of ferrite and austenite and greatly resists pitting and chloride stress. They are weldable, easy to fabricate, magnetic, and offer better corrosion resistance than the austenitic grades. Examples are S32750 and 2205 stainless steel grades.
They contain about 12-16% chromium, 3-8% nickel, and a small proportion of other alloying elements such as copper, aluminum, and titanium capable of forming a precipitate. They are usually very strong, ductile, and heat-treatable. They are machined in the annealed condition and then heat treated.
Stainless steel is one of the prominent materials with high use. It offers extensive advantages over alloy steel, such as:
Manufacturers across industries improve carbon steel’s mechanical properties with the help of more than 20 alloying elements. Each of these alloying elements offers distinct properties. Here are the top five (5) common alloying elements:
This section compares the different aspects of alloy steel and stainless steel:
Alloy steel is famous for its high strength-to-weight ratio, strength, and durability. Also, it maintains hardness at high temperatures and offers good wear and corrosion resistance. On the other hand, stainless steel is easy to clean and highly resistant to corrosion and stain. It is non-magnetic, durable, electrically conductive, and highly resistant to higher temperatures.
The alloying elements of alloy steel include a high amount of chromium, molybdenum, and other alloying elements. Using higher alloying elements helps heat-treat alloys to a wide range of hardness levels.
In contrast, stainless steel is highly resistant to acid, bases, and other organic solutions. Its primary constituents include chromium, carbon, and iron. However, certain varieties often contain nickel, manganese, silicon, and other elements.
Manufacturers often use alloy steels in the construction, automotive, oil and gas, aerospace, and manufacturing fields. On the other hand, typical applications for stainless steel include Kitchenware, medical equipment, the chemical and petrochemical industry, and the food and beverage industry.
Tensile strength describes a material’s ability to withstand tensile strength before it breaks. However, the alloy and the employed heat treatment often determine this property. Alloy steel is very durable, and its tensile strength is about 960 Mpa, while stainless steel is less durable and with a tensile strength of 621 Mpa.
Fatigue stress defines a material’s ability to withstand stress for a particular number of cycles. A material’s fatigue stress is the maximum stress it can withstand. For instance, 146.45 Mpa is the fatigue stress of the stainless 316L.
Generally, stainless steels have lower fatigue strength than alloy steel—nonetheless, stainless steel grades like duplex stainless steel exhibit high fatigue strength due to their microstructure.
Stainless Steel CNC Machined PartsBesides stainless steel, other alternatives to using alloy steel include:
Combining vanadium atoms with chromium forms lattice structures with excellent strength-to-weight ratios. This makes chromium-vanadium ideal for various applications that need a strong and lightweight material. However, due to its strength, most manufacturers use chromium-vanadium to create cutting tools.
Aluminum is a typical material widely utilized in the automobile manufacturing industry. Aluminum products resist corrosion when exposed to water like iron-based metals do. Also, aluminum is perfect for making body panels and other structural components of vehicles because it is very strong and lightweight.
Here are other similar materials that stainless steel is compared against besides alloy steel:
Carbon Steel is one of the famous steel types. It is commonly used because of the durability and high strength it offers. Manufacturers generally use carbon steel for several applications because it costs less than stainless steel. High carbon steel provides excellent strength and resistance to wear, which many cutting tools need. Meanwhile, low-alloy steel offers versatility and malleability for machinery parts, cookware, and pipes.
This is a carbon steel type commonly used for making tools. It exhibits remarkable hardness and wear resistance. As a result, manufacturers utilize these features in manufacturing products such as drill bits, knives, and saws.
Considering the tips below, you should be able to determine the right steel for your application.
The functional requirement of a product will always determine the steel type suited for such application. For instance, if a part is required to function in a marine environment, its corrosion resistance property is a primary factor. Hence, a stainless steel grade material is a perfect choice. Also, alloy steel would be ideal for structural applications such as construction.
Stainless steel is better than alloy steel when considering maintenance and lifespan. Stainless steel grades need little to no maintenance and exhibit longer lifespans because of their self-repairing properties. More importantly, stainless steel is recyclable.
Stainless steel is quite famous for its aesthetic appeal. Hence, product designers and manufacturers in the architecture and interior designing sectors commonly use stainless steel for most parts. Its highly reflective surface makes it shiny and modern. Additionally, it is available in various shapes offering manufacturers extensive products.
The limitations of your budget determine the ideal steel type for your project. As far as cost goes, alloy steel is less expensive than stainless steel. However, it is advisable not to compromise quality for cost.
This article has detailed an explanation of alloy steel vs. stainless steel, discussing their distinct properties. Although both materials offer impressive mechanical properties and are critical to modern manufacturing, it would be best to determine the one that fits your machining project best, considering all variables.
Metal CNC Machining ServiceHowever, if you need the help of professionals determining the suitable material between alloy steel and stainless steel, contact AT-Machining. We provide extensive manufacturing capabilities and value-added services for your prototyping and manufacturing needs. Our team of expert engineers has in-depth knowledge and experience in CNC machining, sheet metal fabrication, and other manufacturing solutions you seek. Contact us today; let’s discuss the details of your next project.
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