Stainless Steel 304
Stainless steel grade 304 is an austenite stainless steel that is the most widely used and versatile of the various grades of stainless steel. It is a part of the T300 series stainless steels with...
Stainless Steel Grades: Uses and Applications
Introduction
This article takes an in-depth look at stainless steel grades.
Read further to learn more about topics such as:
- What are stainless steel grades?
- Categories of stainless steel
- Stainless steel grades
- Applications of different stainless-steel grades
- And much more�
Chapter 1: What Are Stainless Steel Grades?
Stainless steel grades consist of a mix of carbon, iron, 10.5% to 30% chromium, nickel, molybdenum, and other alloying materials. This adaptable metal is extensively used in crafting products, tools, equipment, and infrastructure across a multitude of industrial, commercial, and residential settings.
The superior attribute of stainless steel is its resistance to corrosion, which is largely credited to the presence of chromium. This alloying component interacts with oxygen found in air and water to create a thin, stable layer of chromium oxide that safeguards the metal's surface underneath. Molybdenum enhances its anti-corrosive properties by preventing pit formation on this protective coating. This oxide layer can self-repair after minor damage, although severe exposure to chlorides, strong cleaners, high salt content, humidity, or heavy abrasion may lead to rust development.
Beyond their corrosion resistance, stainless steels boast remarkable mechanical qualities like high strength, toughness, ductility, fatigue resistance, and wear resistance. They are capable of withstanding extreme temperatures, pressures, and cryogenic environments. Their non-reactive nature with most chemicals makes them suitable for use in chemical processing equipment and containers. Additionally, stainless steels are prized for their aesthetic appeal, offering a shiny, bright, and attractive finish.
Chapter 2: Categories of Stainless Steel Grades
Stainless steel grades are classified into five main categories. Each stainless steel type is engineered for specific industrial applications, driven by variations in crystal structure, alloy composition, mechanical properties, and corrosion resistance. Understanding the categories of stainless steel is critical for selecting the best material for manufacturing, construction, industrial processing, chemical equipment, and specialized engineering projects. In this chapter, we present an in-depth overview of each primary stainless steel grade category, highlighting key features and suitable uses.
Austenitic Stainless Steels
Austenitic stainless steel is the most common type of stainless steel, named after English metallurgist Sir William Chandler Roberts-Austen. It constitutes the backbone of the stainless steel industry, encompassing the 200 and 300 series, with popular designations including 304 and 316 stainless steel.
Austenitic stainless steels have a face-centered cubic (FCC) crystal structure, which is stabilized by the addition of nickel, manganese, and nitrogen. This FCC structure is maintained at all temperatures. Austenitic stainless steels typically contain moderate to high levels of nickel, ranging from 8-12%, along with significant amounts of manganese and nitrogen, which stabilize the austenitic structure. However, these additions increase the cost of the material. Carbon is present in only low concentrations.
Austenitic stainless steels cannot be hardened through heat treatment; instead, they are cold worked to enhance their strength, hardness, and surface finish. They are generally non-magnetic but can become slightly magnetic after cold working. These steels offer excellent formability and weldability. With a high chromium content (16-30%), austenitic stainless steels also exhibit superior chemical resistance, making them ideal for food processing, medical equipment, chemical tanks, and marine environments where high corrosion resistance is critical. Industry leaders often choose 304 stainless steel for kitchen appliances, while 316 stainless steel's enhanced molybdenum content allows it to resist chlorides and saline exposure, common in petrochemical and offshore projects.
Ferritic Stainless Steels
Ferritic stainless steels have a body-centered cubic (BCC) crystal structure and feature high chromium content, ranging from 11% to 27%, with only small amounts of nickel. Their low carbon content (about 0.03%) makes them highly ductile and formable. However, like austenitic steels, ferritic stainless steels cannot be hardened through heat treatment.
Ferritic stainless steels are magnetic and have high thermal conductivity, making them suitable for applications like boilers, automotive exhaust systems, and heat exchangers that involve heat transfer. They feature a low coefficient of thermal expansion, which ensures dimensional stability across a wide temperature range. Additionally, their ferritic structure provides excellent resistance to stress corrosion cracking, enabling them to endure exposure to chlorides, high humidity, and elevated temperatures. Common ferritic stainless steel grades include 409 and 430, which are preferred for architectural panels, household appliance parts, and moderately corrosive operating conditions due to their cost-effectiveness.
Martensitic Stainless Steels
Martensitic stainless steels have a body-centered tetragonal crystal structure and contain 11.5-18% chromium along with 0.1-1.2% carbon. The high carbon content contributes to their relatively high strength and brittleness. However, the low nickel content in martensitic stainless steels results in reduced corrosion resistance. They are classified into two types based on carbon content: low carbon martensitic steels (0.05-0.25% carbon), which offer better corrosion resistance, and high carbon martensitic steels (0.61-1.50% carbon), which provide greater strength but are more brittle.
The hardness and strength of martensitic stainless steels can be enhanced through heat treatment processes such as age hardening, annealing, quenching, and tempering. Typical martensitic grades, such as 410 and 420 stainless steel, are popular in the production of surgical instruments, turbine blades, and cutlery, where wear resistance, toughness, and some corrosion protection are necessary. These steels are magnetic and impact-resistant but are challenging to weld and form due to their brittleness.
Ferritic and martensitic stainless steels are classified under the 400 series, which are sought after for products such as shafts, valves, and fasteners subjected to high strength and moderate corrosion exposure.
Duplex Stainless Steels
Duplex stainless steels feature a microstructure that includes both austenitic and ferritic phases in roughly equal proportions. They offer approximately twice the strength of conventional austenitic and ferritic stainless steels. While their toughness, ductility, and formability surpass those of ferritic steels, they do not reach the level of austenitic steels. Duplex stainless steels benefit from good resistance to stress corrosion cracking, a trait inherited from the ferritic phase. Corrosion resistance in duplex stainless steels can vary significantly depending on composition; increased levels of nickel, molybdenum, and nitrogen enhance resistance to pitting and crevice corrosion. Additionally, duplex stainless steels are generally more cost-effective compared to austenitic stainless steels.
Duplex grades such as 2205 and super duplex (e.g., 2507) are extensively used in oil and gas, pulp and paper, and chemical processing industries due to their exceptional combination of mechanical strength and corrosion resistance. Their effective performance in environments with aggressive chemicals, chloride-rich atmospheres, or fluctuating temperatures makes them a top choice for pressure vessels, desalination plants, and marine structures. Duplex stainless steels are increasingly favored for projects seeking low life-cycle costs, improved strength-to-weight ratios, and sustainability.
Precipitation-Hardened Stainless Steels
Precipitation-hardened (PH) stainless steels contain small amounts of copper, aluminum, titanium, and molybdenum. After alloying these elements, the stainless steel undergoes age hardening treatment, which causes these elements to precipitate as hard intermetallic compounds. This precipitate phase obstructs the movement of dislocations defects in the crystal lattice structure thereby enhancing the steel's strength and hardness. PH stainless steels offer corrosion resistance comparable to that of austenitic stainless steels.
PH stainless steels are categorized into three types: martensitic, austenitic, and semi-austenitic. Austenitic PH steels maintain their crystal structure at all temperatures. Semi-austenitic PH steels retain their austenitic structure after solution treatment and quenching, but this structure can be converted to martensitic through cryogenic treatment or cold working. The most well-known grade in this group is 17-4 PH, which delivers exceptional mechanical properties while maintaining moderate corrosion resistance, and is widely used for aerospace components, high-performance shafts, and precision hardware.
When choosing among stainless steel grades, consider factors such as corrosion resistance required by the application, the strength or hardness specifications, weldability, formability, and economic considerations. Consulting with leading stainless steel manufacturers or certified suppliers can help narrow material options, source mill test reports, and ensure that fabrication meets specific project parameters. For more detailed guidance, reference our stainless steel grades comparison chart or speak directly with an expert to match grade specifications to your industry requirements.
Leading Manufacturers and Suppliers
Chapter 3: Stainless-Steel Grades
There are over 150 stainless steel grades, but only about 15 are commonly used. The most widely recognized grading system was developed by the Society of Automotive Engineers (SAE). Other systems, such as the Universal Numbering System (UNS) for Metals and Alloys, also exist and can vary by region.
The stainless-steel grades and their properties are the following:
Austenitic Chromium-Nickel-Manganese Alloys (Grade 200 series)
Grade 201 Stainless Steel
Grade 201 stainless steel is an austenitic stainless steel with 16-18% chromium and 3.5-5.5% nickel. It serves as a cost-effective substitute for grade 304 stainless steel and high nickel alloys. Although its lower nickel content provides less corrosion resistance compared to other grades, it is more affordable. The addition of manganese and nitrogen can enhance its yield strength. Grade 201 is valued for its good formability and weldability, making it a versatile material.
Grade 202 Stainless Steel
Grade 202 stainless steel is an austenitic stainless steel that contains 17-19% chromium, 4-6% nickel, and 7.5-10% manganese. It is widely used for applications requiring precipitation hardening and offers good corrosion resistance, high hardness, toughness (even at lower temperatures), strength, and weldability. Although it has properties similar to grade 302, grade 202 has a lower yield strength. It can be machined in an annealed condition and, like grade 201, is also cost-effective.
Austenitic Chromium-Nickel Alloys (Grade 300 series)
Grade 301 Stainless Steel
Grade 301 stainless steel is an austenitic stainless steel that provides similar corrosion resistance to grade 304 in mildly corrosive environments at ambient temperatures. However, its corrosion resistance is lower in extremely corrosive and high-temperature environments due to its lower chromium content (16-18%).
Grade 301 stainless steel is known for its high strength and is available in both annealed and cold-worked conditions. The annealed version offers excellent formability, while the cold-worked version provides increased strength. When cold worked, grade 301 becomes magnetic. It is suitable for welding, but welded components require annealing to dissolve precipitated chromium carbides and prevent intergranular attack.
Grade 301L stainless steel is a variant of grade 301 that offers enhanced ductility and weldability. It does not require annealing to achieve optimal corrosion resistance. Another variant, grade 301LN, contains higher nitrogen levels and has a higher work hardening rate. Both grade 301L and 301LN do not require annealing.
Grade 302 Stainless Steel
Grade 302 stainless steel is an austenitic stainless steel with approximately 18% chromium and 8% nickel. Its chemical composition closely resembles that of grade 304, with a slightly higher carbon content. Grade 302 is known for its high toughness, tensile strength, yield strength, and corrosion resistance. To address its tendency to work harden, it is processed at low speeds and high feed rates. Due to the formation of gummy chips, chip breakers should be used on all tooling. Recommended welding methods for grade 302 include resistance welding and shielded fusion welding, with post-weld annealing necessary to ensure optimal properties.
Grade 304 Stainless Steel
Grade 304 stainless steel is the most widely used austenitic stainless steel, known for its excellent chemical, oxidation, and corrosion resistance across a broad range of temperatures. It contains 18% chromium and 8% nickel, which is reflected in its old designation, 18/8. Despite its many advantages, grade 304 can be susceptible to pitting corrosion and stress corrosion cracking when exposed to chlorides. Variants of grade 304 include grade 304L, which has lower carbon content, and grade 304H, which has higher carbon content.
In addition to its excellent corrosion resistance, grade 304 stainless steel boasts high ductility, allowing it to be easily formed and machined into a variety of products. It can be severely deep-drawn and offers greater formability compared to grade 316. However, grade 304 requires annealing after cold working to reduce work hardening.
Grade 305 Stainless Steel
Grade 305 stainless steel is an austenitic stainless steel with 18% chromium, at least 10% nickel, and a higher carbon content. It offers good chemical and corrosion resistance along with high strength. Its elevated nickel content results in a low rate of work hardening, making it well-suited for deep drawing applications. While grade 305 can be welded using resistance and fusion methods, oxyacetylene welding is not recommended.
Grade 309 Stainless Steel
Grade 309 stainless steel is an austenitic stainless steel that contains at least 22% chromium and 12% nickel, with a low carbon content. It offers excellent corrosion and oxidation resistance, along with high tensile and creep strengths at elevated temperatures. Grade 309 is well-suited for saline environments. It can be rolled, formed, stamped, and deep-drawn with ease, but requires annealing after cold working to prevent work hardening and preserve its ductility.
Grade 316 Stainless Steel
Grade 316 stainless steel is the second most popular stainless steel grade after grade 304. This austenitic stainless steel contains elevated levels of molybdenum as well as high amounts of silicon, manganese, carbon, chromium, and nickel. The increased molybdenum content enhances its resistance to pitting and crevice corrosion, especially in saline environments, compared to grade 304. Grade 316 also has excellent forming and welding characteristics, and annealing is typically not necessary after welding thin sections.
Grade 316 stainless steel has two variants: grade 316L and grade 316H. Grade 316L features lower carbon content, which makes it resistant to chromium carbide precipitation and ideal for projects requiring extensive welding. On the other hand, grade 316H has higher carbon content, resulting in increased tensile and yield strength, making it more suitable for high-temperature applications.
Grade 321 Stainless Steel
Grade 321 stainless steel is a titanium-stabilized austenitic stainless steel known for its good corrosion resistance and excellent resistance to chromium carbide precipitation at high temperatures. It offers superior creep and stress rupture properties compared to grade 304, maintaining these properties effectively even at elevated temperatures.
Grade 321H is a modified version of grade 321 stainless steel. It features increased creep resistance and higher carbon content, which enhances its strength at elevated temperatures.
Grade 347 Stainless Steel
Grade 347 stainless steel is a niobium-stabilized austenitic stainless steel. Similar to grade 321, it is resistant to chromium carbide precipitation and provides excellent intergranular corrosion resistance. Grade 347 offers superior creep and stress rupture properties compared to grade 304 and has slightly better oxidation resistance than grade 321, while maintaining good overall corrosion resistance.
Ferritic and Martensitic Chromium Alloys (Grade 400 series)
Grade 409 Stainless Steel
Grade 409 stainless steel is a ferritic stainless steel stabilized with titanium and/or niobium. It offers good mechanical properties and corrosion resistance at high temperatures, along with excellent formability and welding characteristics. It can be welded using methods such as arc, resistance spot, and seam welding, but requires preheating to 150-260°C and post-weld annealing to enhance ductility. Grade 409 is not ideal for aesthetic applications due to its tendency to develop light surface rusting.
Grade 410 Stainless Steel
Grade 410 stainless steel is a heat-treatable, general-purpose martensitic stainless steel with 11.5% chromium. Hardening, tempering, and polishing processes are used to enhance its wear resistance, corrosion resistance, and overall mechanical properties. It is compatible with water, air, hot gases, food products, and most chemicals, including mild acids, nitric acid, concentrated sulfuric acid, dilute acetic acid, and naphtha. However, due to its lower nickel content, grade 410 is best suited for mildly to moderately corrosive environments.
Grade 410 stainless steel can be welded using most conventional welding methods. To reduce the risk of cracking, it should be preheated to between 150°C and 260°C, and post-weld annealing should be carried out. This grade retains its machinability after tempering and annealing. Grade 410 is commonly used in refinery equipment, turbines, pumps, valves, and for machine elements such as bolts, screws, nuts, and bushings.
Grade 420 Stainless Steels
Grade 420 stainless steel is a martensitic stainless steel with a high carbon content ranging from 0.15% to 0.45% and a minimum chromium content of 12%. It represents an upgrade from grade 410, with its strength increasing significantly by about 1000 MPa when hardened and stress-relieved. Although its corrosion resistance is lower compared to austenitic and ferritic stainless steels, it is still adequate for applications involving mild acids, alkalis, freshwater, normal atmospheric conditions, and food products. While it has good ductility in its annealed state, it is generally used in a fully hardened, surface-ground, or polished condition due to its relatively poor corrosion resistance.
Grade 420 stainless steel is relatively easy to machine, though its machinability decreases as hardness increases. Steels with a hardness greater than 30 HRC are particularly challenging to machine. This grade is commonly used for manufacturing cutting tools (such as knives and dies), cutlery, needles, surgical tools, and bushings.
Grade 420HC
Stainless steel grade 420HC has a higher carbon content than grade 420, which contributes to its increased hardness. Despite being softer compared to some other steel types, grade 420HC is considered a mid-range steel. Its higher carbon content enhances its hardness, making it well-suited for manufacturing cutting tools due to its excellent edge retention and ease of sharpening. Edge retention refers to the steel's ability to maintain a sharp edge over time. While grade 420HC is more expensive than grade 420, it offers lower corrosion resistance.
Knives made from grade 420HC are favored by hunters and fishermen due to their durability in harsh weather conditions. Being less expensive than other steels, 420HC is commonly used for making cost-effective knives available through large retailers. While 420HC sharpens easily, it does not maintain its edge as well as some other steels, necessitating more frequent sharpening.
Grade 420J2
Stainless steel grade 420J2 is an affordable option with good corrosion resistance in mild environments, including domestic and industrial settings. It also offers resistance to dilute nitric acid, carbonic acid, ammonia, crude oil, detergent solutions, vinegar, food acids, several petroleum products, and steam.
What sets stainless steel grade 420J2 apart from other steels is its strength and impact resistance, particularly after hardening and tempering. It is machinable, meaning it can be turned, drilled, and bent. Additionally, grade 420J2 can be annealed at temperatures ranging from 730°C to 790°C (1346°F to 1451°F).
Stainless steel grade 420J2 is commonly used to manufacture surgical instruments, daggers, swords, budget knives, diving knives, domestic scissors, and hair cutting scissors.
Grade 430 Stainless Steel
Grade 430 stainless steel is a ferritic stainless steel primarily composed of chromium and iron, with very low levels of carbon, nickel, and other alloying elements, making it more cost-effective. It offers good heat and corrosion resistance, handling organic and nitric acids well. As a ferritic stainless steel, it boasts excellent resistance to stress corrosion cracking. Grade 430 also has good machinability and formability, with a low work hardening rate. However, it has lower ductility and is prone to galling.
Grade 434 Stainless Steel
Grade 434 stainless steel is a widely used non-hardenable ferritic stainless steel, notable for its high molybdenum content, which enhances its corrosion and heat resistance. Its performance is comparable to that of grade 430.
Grade 434 stainless steel is a widely used ferritic stainless steel that can withstand temperatures up to 1500°F. Due to its exceptional high-temperature resistance, it cannot be hardened by heat treatment and is cold-formed like low carbon steel. Its primary application is in automotive trim.
Grade 440 Stainless Steel
Grade 440C stainless steel is a high carbon steel known for its high hardness, wear resistance, and strength after heat treatment. This makes it suitable for applications like valve components and ball bearings. Grades 440A and 440B, while similar to 440C, contain lower percentages of carbon and offer somewhat reduced hardness and strength compared to 440C.
All grades of 440 stainless steel are commonly used with grade 440C being more readily available. Grade 440F is a machining type of grade 440 stainless steel with a carbon content that is similar to grade 440C.
Grade 440 stainless steels are not suitable for high-temperature applications due to the risk of over-tempering. All sub-grades of grade 440 share similar properties, with grade 440C offering corrosion resistance comparable to that of stainless steel grade 304.
Chapter 4: Forms of Stainless Steel
Stainless steel is shaped and formed to suit various manufacturing and production needs. Suppliers and manufacturers produce raw stainless steel in forms that match the intended applications. Coils are commonly used in products like kitchen appliances, automotive parts, and medical instruments, while stainless steel bars are utilized to create cutlery, plumbing components, and construction materials.
Coils
Stainless steel coils are flat strips rolled from stainless steel sheets, with thicknesses ranging from 0.02 mm to 6 mm (0.0008 inch to 0.23 inch). The production begins with stainless steel slabs, which are processed through a Z mill a series of rollers to produce these coils. The Z mill process creates wide coils known as mill edge coils.
The wide coils are further processed through a slitting operation, which cuts them into narrower strips, resulting in coils known as strip coils, slit coils, banding, or simply strips. The winding method of these coils determines their type, which can be pancake, ribbon, or bobbin. Typically, coils are wound with even edges on a strip, and their outer diameter (OD) is limited to ensure safe handling.
Stainless steel coils are incredibly versatile and find application across numerous industries. In the automotive industry, stainless steel is used extensively for vehicle structures due to its strength and resistance to corrosion. In the food production sector, stainless steel coils are essential for manufacturing equipment such as countertops and processing machines, ensuring hygiene and durability. Beyond these major applications, stainless steel coils are also utilized in aerospace, defense, pipelines and fittings, and construction, highlighting their broad utility and importance in modern manufacturing and infrastructure.
Bars
Stainless steel bars are available in various forms, including rods, rounds, and round bars. They are produced from different grades of stainless steel, with grades 304 and 316 being the most common. Stainless steel bars can come in flat, round, hexagonal, octagonal, or square shapes, depending on the manufacturer. While they can be used in their original form, they are often melted down and reworked into channels, tubing, or extruded angles for further applications.
Among the various forms of stainless steel, bars are the most economical due to their greater volume compared to other forms. They are also easier to ship and process with predictability. The different shapes of stainless steel bars indicate their intended applications and the processes they will undergo. For instance, round bars might be used in machining and manufacturing parts, while flat bars could be utilized in construction and structural applications. The choice of shape and grade ensures that the stainless steel meets specific requirements for strength, durability, and functionality.
The manufacturing process of stainless steel begins with melting the raw materials, a process that typically takes eight to twelve hours. Once melted, the stainless steel is cast into bars, which are then hot rolled into various shapes. After rolling, the bars are annealed, which involves heating them to a high temperature and then cooling them through quenching or air hardening to achieve the desired properties. Following cooling, the stainless steel undergoes a descaling or pickling process to remove the oxide film that forms during hot forming. This ensures a clean surface and prepares the stainless steel for further processing or finishing.
Foil
Stainless steel foil consists of thin strips with a thickness of 0.2 mm (0.008 inch) and a width of 300 mm (12 inches) or less. It retains all the properties of stainless steel and is utilized in a variety of applications including the production of heat exchangers, capacitors, and fuel cells. A significant application of stainless steel foil is in the manufacture of sensitive medical instruments and food processing equipment due to its durability, corrosion resistance, and ability to maintain cleanliness.
Several grades of stainless steel are used in the fabrication of stainless steel foil, including grades 301, 304, 316, 409, 430, and duplex 2205. These grades are chosen based on the specific requirements of the application, such as corrosion resistance, strength, or temperature tolerance. Stainless steel foil can come in different forms, including full hard, half hard, and quarter hard, which refer to the degree of hardness and flexibility of the foil. Full hard foil is the most rigid and least flexible, while half hard and quarter hard foils offer progressively more flexibility, making them suitable for different manufacturing and industrial uses.
Among the various grades of stainless steel foil, grade 304 is the most commonly used due to its adaptability, versatility, and availability. It offers high performance at a relatively low cost. The qualities of grade 304 that make it ideal for foil production include its low thermal and electrical conductivity, non-magnetic properties, and excellent corrosion resistance. Additionally, grade 304 is easily formable, allowing it to be shaped into various configurations with ease. These attributes make it a preferred choice for applications requiring high-quality performance in demanding environments.
Stainless steel foil is a thin, flexible material that can be layered and wrapped around equipment, objects, and other items to provide protection. Its flexibility and durability make it ideal for a wide range of applications, from shielding sensitive components to providing a protective layer in various environments. Readily available from manufacturers and online, stainless steel foil is valued for its strength and longevity, making it a popular choice for both industrial and consumer uses.
Plate
Stainless steel plates are available in various sizes and thicknesses, typically starting from slabs that are 4 inches thick or more. To achieve the desired dimensions, these slabs undergo cold or hot rolling processes. Hot rolling involves passing the slabs through rollers at high temperatures to reduce their thickness, while cold rolling is used for applications requiring enhanced strength or precise thickness. Stainless steel plates can be made from various grades, with grades 304 and 316 being among the most commonly used due to their versatile properties.
The primary distinction between stainless steel plate and stainless steel sheet lies in their thickness. Stainless steel is classified as a plate if its thickness is 6 mm (0.25 inch) or greater. In contrast, stainless steel sheet has a thickness less than 6 mm and is typically measured in gauges. Both plates and sheets can be measured in millimeters as well, but their thicknesses and the units of measurement used (inches for plates and gauges for sheets) help differentiate them. This classification impacts their applications, with plates often used in structural and heavy-duty applications, while sheets are commonly used for lighter, more precise uses.
Stainless steel plate is widely used in the production of various products because of its durability, ease of maintenance, and attractive appearance. The application of stainless steel plate depends on its specific grade. Among the most common grades are 304 and 316, with grade 304 further categorized into 304, 304H, and 304L.
Rod
Stainless steel rods are available in various shapes and are utilized in support structures, appliances, and machinery. Their sizes vary based on metal content and intended application, with diameters ranging from 1.5 mm to 152.4 mm (0.0625 in to 6 in). In construction, they serve as reinforcement for masonry and fence posts.
A distinctive feature of stainless steel rods is their alloy composition, which differs from that of stainless steel bars. Rods typically have lower carbon content and higher manganese content, enhancing their wear resistance. While high carbon content increases hardness and brittleness, making the material prone to cracking, the higher manganese content in stainless steel rods improves their durability.
Stainless steel rods are produced through an extrusion process involving a stainless steel billet. This process starts by heating the billet until it becomes malleable but not molten. The heated metal is then pushed through a hardened steel die by hydraulic force, shaping it into the final rod form. Once extruded, the rods are directed to the drawing area, where they undergo further processing, including pointing, drawing, straightening, or cold rolling.
The shapes of stainless steel rods include:
- Square
- Hollow
- Solid
- Round
- Hexagonal
- Flat
- Rectangular
- Octagonal
Sheets
Stainless steel sheets are thin, flat pieces of stainless steel with a thickness of less than 6 mm (0.25 in). These sheets are created by passing stainless steel slabs through a Z mill, which compresses them to the desired thickness. Typically, stainless steel slabs are at least four inches thick, necessitating the use of multiple rollers in the Z mill to achieve the final sheet thickness.
The rolling process can be either hot or cold. In hot rolling, stainless steel slabs are heated above their recrystallization temperature, allowing them to be reduced to a thickness of 0.28 mm (0.011 in) more quickly than in cold rolling. Cold rolling, on the other hand, involves passing the metal through the rollers of a Z mill multiple times at room temperature to achieve precise thicknesses and dimensions.
Stainless steel plates and sheets are produced through the same process but differ in thickness. Sheets are less than 6 mm (0.25 in) thick, whereas plates exceed 6 mm (0.25 in) in thickness. In addition to their measurements in millimeters or inches, stainless steel sheets are also measured in gauges, which use a different scale compared to gauges for other metals.
Strips
Stainless steel strips are thin, long, and narrow extensions of stainless steel sheets, often referred to as stainless steel coils. They come in various widths and standard lengths, though custom lengths are available to suit specific applications or customer preferences. Their popularity stems from their exceptional strength and smooth, lustrous finish.
Stainless steel strips are produced using either cold rolling or hot rolling processes. Cold rolled stainless steel strips have thicknesses ranging from 0.1 mm to 3 mm (0.004 in to 0.12 in) and widths between 100 mm and 2000 mm (4 in to 79 in). These strips are known for their smooth, flat surfaces, precise measurements, and excellent mechanical properties. They can also be further processed into coated plates.
Hot rolled stainless steel strips are available in thicknesses from 1.8 mm to 6 mm (0.07 in to 0.23 in) and widths ranging from 50 mm to 1200 mm (2 in to 47 in). These strips have lower hardness, making them easier to process and stretch compared to cold rolled strips. However, hot rolled stainless steel strips typically have a dark, rough surface due to the scale that forms during the heating process.
Stainless steel strips are produced from series 200, 300, and 400 stainless steels and are categorized into several grades: austenitic, ferritic, martensitic, duplex, PH (precipitation-hardening), and super austenitic. These diverse grades are tailored to meet the requirements of various applications, ranging from aerospace and automotive manufacturing to home appliances and electronics.
Wire
Stainless steel wire serves a variety of applications, including spring wire, cutting wire, cold heating wire, and roping wire. Each type is designed with specific properties to suit its intended use. Stainless steel wire gauges range from 14 AWG to 44 AWG, with additional gauges available to meet custom requirements. The gauges are also distinguished by the grade of stainless steel used in their manufacture.
Spring wire is the most commonly used type of stainless steel wire, manufactured from 300 series and 400 series stainless steels. The choice of grade depends on the desired properties, spring design, and fabrication method. A key feature of stainless steel spring wire is its capacity to endure different levels of heat.
Cutting stainless steel wire is prized for its rigidity and surface hardness. It exhibits excellent machinability and maintains consistent dimensional tolerances. This type of wire earned its name due to its ability to retain its roundness during cutting. Its exceptional machinability allows for rapid cutting, which extends the lifespan of cutting tools.
Cold heating stainless steel wire is utilized in the production of bolts, nuts, nails, and screws. It is manufactured to stringent industrial standards to ensure the reliability of these connectors. Key characteristics of cold heating stainless steel wire include its high tensile strength and a stable microstructure that maintains its properties over time.
Roping stainless steel wire is specifically designed for assembling wire rope and comes in various sizes and diameters. Unlike other types of stainless steel wire, roping wire is used together with other wires, whether they are similar or different. The key factors for roping stainless steel wire include its diameter, which affects the overall diameter of the wire rope, and its tensile strength. Additionally, it must be exceptionally flexible to effectively integrate with other wires in the rope assembly.
Chapter 5: Application of Stainless-Steel Grades
Thanks to its exceptional mechanical properties and corrosion resistance, stainless steel is used in a wide range of products, equipment, and structures. Applications of various stainless steel grades include, but are not limited to:
Grade 201 Stainless Steel Applications
Grade 201 stainless steel is utilized in a variety of applications, including structural components, decorative materials, household items, cooking utensils, windows, doors, automotive parts, railroad cars, and trailers.
Grade 202 Stainless Steel Applications
Grade 202 stainless steel is processed into sheets, coils, and plates for use in manufacturing household items, kitchenware, structural components, automotive trim, hose clamps, and railway cars.
Grade 301 Stainless Steel Applications
Grades 301 and 301LN stainless steels are utilized in a variety of applications, including aircraft components, structural parts for railcars, automobiles, trucks, and trailers, as well as in appliances, cooking utensils, kitchenware, wiper blade clips and holders, screen frames, and curtain walls.
Grade 301L stainless steel is employed in the production of pressure vessels, door and drainage components, utensils and appliance parts, as well as structural elements for railcars.
Grade 302 Stainless Steel Applications
Grade 302 stainless steel is frequently used in food handling equipment, cooking utensils, kitchenware, pressure vessels, and medical tools. It is commonly available in various forms, including springs (such as conical compression springs), screens, cables, and wires.
Grade 304 Stainless Steel Applications
Grade 304 stainless steel is widely used in the manufacture of deep-drawn sinks, pans, pots, and troughs. It is also employed in mechanical fasteners (such as nuts, bolts, and screws), industrial plant equipment (including pressure and storage vessels, and tubing), kitchenware, cutlery, cooking utensils, decorative items, and architectural paneling.
Grade 305 Stainless Steel Applications
Grade 305 stainless steel is commonly used to manufacture deep-drawn parts, including cups, pans, bowls, eyelets, rivets, and screws.
Grade 309 Stainless Steel Applications
Grade 309 stainless steel is utilized in the construction of boilers, furnaces, ovens, heat exchangers, kilns, aircraft engines, and automotive exhaust components.
Grade 316 Stainless Steel Applications
Grade 316 stainless steel is widely used in the construction of chemical storage tanks, heat exchangers, reactors, furnaces, and other process equipment. It is especially favored for marine environments and the refinery industry due to its superior corrosion resistance. Additionally, Grade 316 is employed in architectural panels and railings.
Grade 321 and 347 Stainless Steel Applications
Grade 321 and Grade 347 stainless steels are utilized in a range of applications including aircraft and aerospace components, expansion joints, bellows, furnace parts, heat exchangers, heating element tubing, and chemical process equipment.
Grade 409 Stainless Steel Applications
Grade 409 stainless steel was originally developed for automotive exhaust systems. Its applications have since broadened to include catalytic converters, mufflers, fuel filters, heat exchangers, and agricultural machinery.
Grade 410 Stainless Steel Applications
Grade 410 stainless steel is used in the manufacture of cutlery, knives, flatware, cutting tools, bolts, bushings, and nuts. It is also utilized in constructing petroleum fractionating equipment, gas turbines, pumps, shafts, and valves.
Grade 420 Stainless Steel Applications
Grade 420 stainless steel is commonly used in the production of cutlery, surgical and dental instruments, scissors, blades, and other cutting tools. Grade 420HC and Grade 420J2 are specifically employed in more economical knives and cutting tools.
Grade 430 Stainless Steel Applications
Grade 430 stainless steel is used in the manufacture of kitchen utensils, sinks, dishwasher linings, pipes, tubes, and automotive trim.
Grade 434 Stainless Steel Applications
Grade 434 stainless steel is utilized in automotive trim, furnace chambers, range hoods, gas burners, steam iron bases, flatware, and chemical process equipment.
Grade 440 Stainless Steel Applications
Grade 440 stainless steel is used in the manufacture of valves, valve seats, ball bearings, and cutlery.
Stainless Steel Screws
Stainless steel screws offer exceptional mechanical properties and corrosion resistance, making them ideal fasteners for a wide range of environments.
Self-Drilling Screws
Self-drilling screws are designed to create their own hole as they are driven into the material, eliminating the need for a pre-drilled or pre-punched hole. They are typically used with softer and thinner materials.
Self-Tapping Screws
Self-tapping screws are designed to create their own holes as they are driven into the material, making them versatile for use in wood, plastic, and metal substrates.
Thread Cutting Screws
Thread-cutting screws are designed to create threads in pre-drilled holes within a material, enabling a secure fit as they are driven in.
Chapter 6: Top Stainless Steel Manufacturers
Cleveland-Cliffs
Cleveland-Cliffs is a global leader in stainless steel production for the automotive, construction, and power industries. With over 150 years of experience, the company is the largest flat-rolled steel manufacturer in North America. One of its key objectives has been to significantly reduce emissions from steel production, achieving substantial progress over the past decade. Cleveland-Cliffs produces more than 50 grades of stainless steel.
Source 21, Inc.
Source 21 specializes in manufacturing stainless steel coils and strips, offering custom processing for any grade of stainless steel. The company employs rolling techniques to reduce the thickness of stainless steel, achieving precise gauges and thicknesses tailored to customer specifications. This rolling process ensures a consistent gauge, minimizing the risk of weakness or deformation. Using Z milling, Source 21 gradually reduces the thickness of the stainless steel to produce high-quality coils and strips.
North American Stainless (NAS)
NAS is a leading producer of high-quality stainless steel in the United States, specializing in both cold and hot rolled coils, sheets, and plates across a range of grades. The company primarily focuses on grades 201, 301, 304, 309, 310, 316, and 321, which are available in standard stainless steel forms. NAS is also one of the largest steel recyclers, committed to reducing waste and promoting metal reuse.
Metalmen Sales, Inc.
Metalmen Sales is a leading on-demand supplier of stainless steel with over 100 years of industry experience. Their metalworking processes include rolling, slitting, tempering, shearing, and heat treating to produce high-quality stainless steel. The company maintains a vast inventory of stainless steel products, including foil, rods, bars, strips, coils, sheets, and plates, available in a wide range of grades, including PH stainless steel.
Cada Stainless & Alloys
Cada is a distributor specializing in basic stainless steel grades, many of which are annealed or tempered. They offer stainless steel in various finishes, including rough gray, dull, bright silvery, and mirror. To prevent damage during shipping, Cada provides stainless steel with a PVC coating. With 35 years of industry experience, the company serves sectors such as the automotive industry, oil and gas production, appliance manufacturing, and chemical processing.
Conclusion
- Stainless steel is a type of steel containing a minimum of 10.5% chromium, nickel, molybdenum, and other alloying elements. It has excellent mechanical properties and corrosion resistance and can withstand high temperatures, cryogenic environments, and high pressures.
- The categories of stainless steel are austenitic, ferritic, martensitic, duplex, and precipitation-hardened stainless steel.
- There are over 150 stainless steel grades, but only around 15 of them are commonly used. The SAE developed the most widely adapted stainless steel grading system.
- Stainless steel is a popular metal used in a variety of products, tools, equipment, and structures that serve in many industrial, commercial, and domestic applications.
- Stainless steel screws offer excellent corrosion resistance. The most common types of stainless-steel screws are self-drilling, self-tapping, and thread-cutting screws.
