420 Stainless Steel: Uses, Composition, Properties
Stainless steel is a versatile and widely used material, offering a range of alloys with distinct properties and applications. Among these, 420 stainless steel stands out as a popular choice due to its unique combination of properties and suitability for specific uses. From cutlery and surgical instruments to industrial components, 420 stainless steel finds its place in a diverse array of applications requiring wear resistance, strength, corrosion resistance, and ductility.
This article will discuss 420 stainless steel, its composition, key properties, and the wide range of applications in which it excels.
What Is 420 Stainless Steel?
420 stainless steel is a martensitic stainless steel that is recognized for its unique combination of strength, corrosion resistance, and impressive wear resistance. This stainless steel composition is designed to deliver its key properties at an affordable price: a relatively high carbon level (0.15 to 0.4%) provides hardness and strength, while the 12% chromium provides sufficient corrosion resistance for environments. Manganese enhances strength and hardenability, while silicon aids in deoxidization and enhances strength. Phosphorus and sulfur may be present but are trace impurities.
420 stainless steel finds application in areas that require high strength, moderate corrosion resistance, and good hardness. It is commonly used in the manufacture of knives, surgical instruments, scissors, blades, and various cutting tools. While it offers good corrosion resistance in mild environments, it may not be suitable for highly corrosive or extreme conditions where stainless steels with higher chromium and nickel content, such as 316 or 304 stainless steel, are typically preferred. Common trade names for stainless 420 include: AISI 420, Alloy 420, 420 stainless steel, UNS S42000, and Ruetom Special 420 SS. For more information, see our guide on What is Carbon Steel.
What Is 420 Stainless Steel Used For?
Typical applications of 420 steel include:
- Shear Blades
- Cutlery
- Surgical Equipment
- Bearings
- Needle Valves
- Bushings
- Knife Blades
- Screens
- Fasteners
- Pump Shafts
- Ladder Rungs
- Valve Components
- Steam/Gas Applications
- Turbines
- Hand tools
How Is 420 Stainless Steel Made?
420 stainless steel is made through the processes of melting and refining the raw materials in a furnace and then processing the resulting ingots or continuous-cast billets into basic forms that manufacturers can use to make final products. The production of 420 stainless steel involves several steps:
- The primary raw materials for stainless steel production, including iron ore, chromium, and other alloying elements, are melted together in an electric arc furnace or an induction furnace. The furnace heats the materials to high temperatures above 1,500 °C.
- During the refining process, the molten metal is carefully treated to remove impurities and adjust the composition to achieve the desired properties. The refining can involve processes like degassing, desulfurization and alloying additions.
- Once the molten metal has been refined, it is cast into discrete solid forms such as ingots, or it may be continuously cast into billets or slabs, depending on the intended final product. In continuous casting, the molten metal is continuously poured into a water-cooled mold to create long, solid strands. In ingot casting, the molten metal is poured into molds to form solid blocks or ingots.
- After casting, the stainless steel is subjected to hot working processes such as forging, rolling, or extrusion.
- The steel is then annealed by heating it to a specific temperature and then cooling slowly in a controlled manner.
- The steel is heated to a high temperature and rapidly cooled (quenched) to harden it, followed by tempering at a lower temperature to achieve the desired balance of hardness and toughness.
- Once the desired properties are achieved, the 420 stainless steel may undergo surface finishing processes such as grinding, coating or polishing to improve its appearance or provide additional protection against corrosion.
What Is the Chemical Composition of 420 Stainless Steel?
The chemical composition of 420 stainless steel is given in Table 1:
| Fe | C | Mn | Si | Cr | Ni* | Mo* | P | S | Cu* | Al* | Sn* |
|---|---|---|---|---|---|---|---|---|---|---|---|
Fe Balance | C 0.15-0.40% | Mn 1.00% max | Si 1.00% max | Cr 12.00-14% | Ni* 0.50% max | Mo* 0.50% max | P 0.04% max | S 0.03% max | Cu* 0.50% max | Al* 0.15% max | Sn* 0.05% max |
* Potential optional additions by some manufacturers
What Is the Carbon Content of 420 Stainless Steel?
The carbon content of 420 stainless steel typically ranges from 0.15% to 0.40%. The carbon content contributes to the steel's hardness and strength. The exact carbon content may vary slightly depending on the specific manufacturing process and the desired properties of the steel. However, it generally falls within the specified range. The carbon content of stainless steel can significantly affect its performance characteristics, such as wear resistance, machinability, and corrosion resistance.
What Are the Properties of 420 Stainless Steel?
The physical and mechanical properties of annealed 420 stainless steel are outlined in Table 2 below:
| Property | Metric |
|---|---|
Property Density | Metric 7.74 g/cm3 |
Property Elastic Modulus | Metric 200 GPa |
Property Electrical Resistivity | Metric 0.55 x 10-7 .m |
Property Tensile Strength | Metric 655 MPa |
Property Yield strength (Temper: Annealed) Minimum 0.2% offset | Metric 40,000 psi |
Property Yield Strength (Temper: Hardened + 350°F) Typical 2% offset | Metric 195,000 psi |
Property Elongation (% in 50 mm) | Metric 25 |
Property Brinell Hardness (HB) | Metric 241 max |
Table Credit: https://www.azom.com/article.aspx?ArticleID=972
Is 420 Stainless Steel Magnetic?
Yes, 420 stainless steel is magnetic. The magnetic properties of stainless steel are primarily influenced by its microstructure, which is affected by the composition and processing methods. 420 stainless steel belongs to the martensitic stainless steel family, which is known for its magnetic properties. Martensitic stainless steels can be hardened by heat treatment, resulting in a crystalline structure that is ferromagnetic.
Machinability Rating of 420 Stainless Steel
AISI 420 is generally considered to have moderate machinability, with a machinability of 36-56%. Stainless steel 420 exhibits high toughness and excellent malleability due to its medium carbon content. However, machining this stainless steel alloy poses a particular challenge, mainly related to chip breaking. To overcome this challenge, it is advisable to use cutting tools with sharp edges and tight chip breakers.
What Are the Thermal Properties of 420 Stainless Steel?
The thermal properties of 420 stainless steel are listed in Table 3 below:
| Property | Value | Unit |
|---|---|---|
Property Melting Point | Value 1495 | Unit °C |
Property Thermal Conductivity (@ 100 °C) | Value 24.9 | Unit W/m·K |
Property Thermal Conductivity (@ 500 °C) | Value 28.7 | Unit W/m·K |
Property Specific Heat (0-100°C) | Value 0.46 | Unit kJ/kg·K |
Property Mean Coefficient of Thermal Expansion (0-100 °C) | Value 10.2 | Unit µm/m·K |
Property Mean Coefficient of Thermal Expansion (0-649 °C) | Value 12.1 | Unit µm/m·K |
Table Credit: https://www.ulbrich.com/alloys/420-stainless-steel-uns-s42000/
How To Heat Treat 420 Stainless Steel
Heat treating 420 stainless steel can be done by annealing and hardening. In annealing, the steel is heated to a temperature of around 840-900 °C. It is important to ensure the material is uniformly heated throughout, typically achieved by holding it at this temperature for one to two hours per inch of thickness. After annealing, the steel is slowly cooled in a furnace at 600 °C. This slow cooling process, known as furnace cooling helps relieve internal stresses and softens the steel for further processing. This is then followed by air-cooling.
In hardening, the annealed 420 stainless steel is heated to a temperature range of 980-1035 °C. Once the material reaches the desired temperature, it is rapidly quenched in a quenching medium such as oil or air. The rapid cooling during quenching transforms the austenite phase into martensite, which is a hard and brittle phase.
The hardened 420 stainless steel is reheated to a temperature range of 150-370 °C, depending on the desired hardness and mechanical properties desired. The material is held at this temperature for a specific time, typically ranging from one to four hours, which allows for the formation of small carbides within the martensite structure. Finally, the material can be cooled naturally or through forced air cooling. Take note that 420 stainless steel should not be tempered at a temperature range of 425 and 600 °C.
What Are the Common Forms of 420 Stainless Steel Material?
AISI 420 stainless steel is available in various forms to suit different applications. The common forms of 420 stainless steel material include:
Sheet
420 stainless steel sheet consists of flat, thin material (between 0.5 mm and 3 mm thick) that is often used in applications requiring corrosion and wear resistance and strength. It can be further processed or cut to specific dimensions.
Bar
Bar are solid cylindrical or rectangular pieces of material. Stainless steel bar can be further processed through machining, forging, or other fabrication methods.
Plate
420 stainless steel plates are larger, thicker (up to 200 mm) pieces of material that are often used in structural applications or as a base for machining components. Plates are used when the load-carrying capacity of sheet 420 is not sufficient.
Hot Rolled
Hot-rolled 420 stainless steel refers to a product form that is heated above its recrystallization temperature and then rolled into the desired shape or form. This process leaves the material in a softer condition so that it can be used to create various products such as sheets, bars, and plates.
Annealed
Annealed 420 stainless steel is provided in its soft condition, with a ferrite + carbide microstructure after being heated in the temperature range of 840-900 °C. After reaching this temperature, the stainless steel should undergo a gradual cooling process by placing them in a furnace and allowing them to cool slowly at approximately 600 °C. It is then air-cooled to complete the heat treatment procedure. This process relieves internal stresses, improves ductility, and refines the microstructure, making the material easier to machine or work with.
Cold Drawn
Cold drawn refers to the pulling of the material through a die at room temperature. This process enhances the material's dimensional accuracy, surface finish, and mechanical properties. However, 420 stainless steel exhibits limited tolerance to cold working and is not well-suited for radical forming operations as they can lead to cracking of the material.
What Are Equivalents of 420 Stainless Steel?
Some of the equivalents of 420 stainless steel are outlined in Table 4 below:
| Grade | UNS No. | Old British BS | Old British En | Euronorm No | Euronorm Name | Swedish SS | Japanese JIS |
|---|---|---|---|---|---|---|---|
Grade 420 | UNS No. S42000 | Old British BS 420S37 | Old British En 56C | Euronorm No 1.4021 | Euronorm Name X20Cr13 | Swedish SS 2303 | Japanese JIS SUS 420J1 |
Table Credit: https://www.azom.com/article.aspx?ArticleID=972
What Are the Advantages of Using 420 Stainless Steel?
The use of 420 stainless steel offers several advantages, making it a popular choice in certain applications. Here are some key merits of using 420 stainless steel:
- It has high strength and hardness, making it suitable for applications that require robust and durable materials.
- It is known for its excellent wear resistance. It can withstand abrasion, friction, and contact with hard materials without significant loss of surface integrity.
- It can be hardened through heat treatment. This allows for the adjustment of its hardness, strength, and toughness according to specific application requirements.
- Compared to some other stainless steel grades, 420 stainless steel is relatively more cost-effective. It provides a balance between desirable mechanical properties and affordability. It is an attractive option for applications that require strength and wear resistance without the higher costs associated with certain specialty stainless steel.
What Are the Disadvantages of Using 420 Stainless Steel?
While 420 stainless steel offers many benefits, it also has a few limitations r. Here are some of the potential drawbacks to consider before choosing 420 stainless steel:
- It may be susceptible to corrosion in highly corrosive environments, such as those containing acids or chlorides.
- It can be susceptible to staining and surface discoloration when exposed to certain chemicals or environments.
- It requires careful control of the welding parameters and the use of suitable filler materials to minimize the risk of cracking and maintain the desired properties.
- It has limited heat resistance compared to some other stainless steel grades. It may experience dimensional changes, loss of strength, or even deformation when exposed to high temperatures. It is not recommended for applications involving prolonged exposure to elevated temperatures( temperatures above 500-550°C).
What Is the Difference Between 420 Stainless Steel and 2Cr13 Stainless Steel?
420 stainless steel and 2Cr13 stainless steel are similar martensitic stainless steel grades but exhibit distinct differences. In terms of chemical composition, 420 stainless steel typically contains around 0.15-0.40% carbon, 12.0-14.0% chromium, and small amounts of other elements. On the other hand, 2Cr13 stainless steel consists of approximately 0.16-0.25% carbon, 12.0-14.0% chromium, a small amount of nickel (0.6%), and other elements. In terms of properties, both grades can be hardened through heat treatment, but 420 stainless steel generally has slightly higher hardness. While both offer moderate corrosion resistance, 420 stainless steel tends to exhibit better corrosion resistance. Additionally, 2Cr13 stainless steel is generally considered to have higher toughness compared to 420 stainless steel. Both grades are magnetic due to their martensitic structure. Applications for 420 stainless steel include knives, surgical instruments, and cutting tools, while 2Cr13 stainless steel finds use in knife blades, culinary tools, and general-purpose tools.
What Is the Difference Between 420 Stainless Steel and 416 Stainless Steel?
420 stainless steel and 416 stainless steel are popular martensitic stainless steel grades that have distinct differences. In terms of chemical composition, 420 stainless steel contains approximately 12-14% chromium and a higher carbon content ranging from 0.15% to 0.40%. This higher carbon content contributes to its hardness and wear resistance. On the other hand, 416 stainless steel has a similar chromium content of about 11-14% but a lower carbon content of around 0.15%, which enhances its machinability. 416 is the free-machining version of 420. Grade 416 stainless steel stands out as free-machining stainless steel with an exceptional machinability rating of 85%, making it the most machinable among all stainless steel grades.
In terms of properties, 416 stainless steel is well-known for its outstanding machinability, making it ideal for extensive machining operations. In comparison, while 420 stainless steel is also machinable, it is not as readily machinable as 416 stainless steel. Corrosion resistance-wise, 420 stainless steel generally offers better corrosion resistance. Additionally, 420 stainless steel can achieve higher hardness levels through heat treatment than 416 stainless steel. Both grades are magnetic due to their martensitic structure. Applications for 420 stainless steel include knives, surgical instruments, and cutting tools, while 416 stainless steel finds use in gears, studs, bolts, and valves that require excellent machinability.
What Is the Difference Between 420 Stainless Steel and 316 Stainless Steel?
420 and 316 belong to two different families of stainless steel and have notably different compositions and properties. 420 is martensitic stainless steel. As such, its major alloying elements are chromium and carbon, with small amounts of manganese, silicon, and sometimes molybdenum and nickel. 316 is an austenitic stainless steel alloy that contains a substantial amount of nickel along with more chromium than 416 and has a small amount of molybdenum. Its carbon level is much lower than that of 420.
One significant difference lies in their corrosion resistance. 316 stainless steel is highly resistant to corrosion, particularly in environments with chlorides, acids, or marine conditions, and is known for its resistance to pitting and crevice corrosion. On the other hand, while 420 stainless steel offers good corrosion resistance in mild environments, it is not as resistant as 316 stainless steel, especially in highly corrosive conditions. In terms of strength and hardness, 420 stainless steel excels. 316 stainless steel provides better ductility and toughness, but it is not as hard or strong as 420 stainless steel.
420 stainless steel finds applications in cutlery, surgical instruments, blades, and various cutting tools that require high hardness and wear resistance. 316 stainless steel, in contrast, is widely used in chemical processing, marine environments, pharmaceuticals, and food processing equipment.
Summary
This article presented 420 stainless steel, explained it, and discussed its composition and properties. To learn more about 420 stainless steel, contact a Xometry representative.
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