Alloy 420 is a hardenable, martensitic stainless steel that is a modification of Alloy 410. Similar to 410, it contains a minimum of 12% chromium, just sufficient enough to give corrosion resistant properties. Alloy 420 has higher carbon content than Alloy 410 which is designed to optimize strength and hardness characteristics. It has good ductility it the annealed condition but is capable of being hardened to a minimum Rockwell hardness of 50 HRC, the highest hardness of the 12% chromium grades. Due to its hardening properties, Alloy 420 is not often welded, although it is possible. Martensitic stainless steels are designed for high hardness and sometimes other properties are to some degree compromised. Corrosion resistance is lower than the common austenitic grades and their useful operating range is limited by their loss of ductility at sub-zero temperatures and loss of strength by over-tempering at elevated temperatures. Its best corrosion resistance is achieved when the metal is hardened and surface ground or polished.

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.

APPLICATIONS:

Alloy 420 is used for a variety of applications where good corrosion and outstanding hardness is necessary. It is not usually used at temperatures exceeding 800oF (427oC) due to quick hardening and loss of corrosion resistance. Examples of applications that use alloy 420 include:

• Cuttery
• Knife blades
• Surgical instruments
• Needle valves
• Shear blades
• Scissors
• Hand tools

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:

1. It may be susceptible to corrosion in highly corrosive environments, such as those containing acids or chlorides.
2. It can be susceptible to staining and surface discoloration when exposed to certain chemicals or environments.
3. 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.
4. 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.