Stainless steel is resilient and versatile. It is exceptionally strong and durable, scratch resistant, and does not easily rust, corrode, or stain. It is also easy to clean and sterilize.
Steel is an alloy from iron and carbon, with a carbon content of 2.1% maximum possible. Stainless steel is a type of steel that is resistant to corrosion with the addition of alloying elements. Stainless steel is part of a family of about 200 alloys of steel with high heat and corrosion resistance. The carbon percentage of stainless steel can range from 0.03% to 1.2%. A wide number of industries use stainless steel in manufacturing products. Therefore, its demand is increasing at 5% each year. Stainless steel is also 100% recyclable and made from scrap. This makes it an eco-friendly material. Industries that use stainless steel are:
- Food and catering
- Medical equipment
- Home appliances
- Chemicals and pharmaceuticals
- Offshore and shipbuilding
- Automotive manufacturing
- Energy and industry
- Architecture and construction
Stainless steel alloys get many of their properties from the fact that they are protected by a passivation layer of chromium oxide. This protective layer makes the stainless steel resistant to oxidation, a damaging reaction that occurs between oxygen and iron molecules in the air. If the chromium oxide layer is scratched, it can easily reform, as well as resist pores or cracking, giving the stainless steel that exceptional amount of durability we mentioned earlier.
Manufacturers and end-users rely on stainless steel to make a wide variety of products. In addition to a multitude of products, the use of stainless steel spans a wide range of industries, including engineering and construction, and can be used in smaller items such as elevator doors, gutters, to larger-scale applications such as skyscrapers.
History of Stainless Steel
Stainless steel was officially developed around the turn of the 20th century. However, scientists began inching towards its development about 80 years before then. French metallurgist Pierre Berthier kicked things off in 1821, when we observed that iron alloyed with chromium does not corrode. After observing this, he recommended that manufacturers use chromium-iron alloys to make cutlery. Unfortunately, at this time, manufacturers had neither the knowledge nor the equipment to make a good stainless steel. All of the alloys they managed to make were highly brittle.
In 1872, British metallurgists Clark and Woods finally managed to create a good stainless steel alloy. Then, around 20 years later, when Hans Goldschmidt invented a thermite process that allowed chemists to make carbon-free chromium. Later, chemists used this process to manufacture higher quality of stainless steel.
Once they were able to make modern stainless steel, researchers wasted no time figuring out ways to improve it and apply it to manufacturing processes. Between the years of 1904 and 1911, researchers like Frenchman Leon Guillet created countless stainless steel varieties. This quickly paid off, and in 1908, a German manufacturing company named Friedrich Krupp Germaniawerft built the first stainless steel-based sailing yacht. The 366-ton yacht featured a chrome-nickel steel hull. Then, in 1912, while trying to find a corrosion resistant steel alloy he could use to make gun barrels, British metallurgist Harry Brearley stumbled across the formula for martensitic stainless steel. Also, in 1912, two Krupp-employed engineers, Eduard Maurer and Benno Strauss patented a version of austenitic stainless steel, which they called Nirosta. Not long after the development of martensitic stainless steel, a British company named Firths Vicker patented martensitic stainless steel and sold it under the name “Staybrite.” Brearley later partnered with American Elmwood Haynes, who had already patented the steel product in the United States, to form the American Stainless Steel Corporation.
After the formation of this company, the use of stainless steel became commonplace, and by 1929, manufacturers in the United States alone had fabricated and sold over 25,000 tons of the metal. Stainless steel went on to play an important role in the creation of countless products, including WWII military equipment, industrial machinery parts and much, much more.
Today, stainless steel is an incredibly popular material that is produced and sold all over the world. Producers today focus heavily on sustainability and lowering costs.
Properties of Stainless Steel
- Stainless steel exhibits high strength and low elongation or low strength and high elongation properties.
- Stainless steel works better at high temperatures due to better resistance properties.
- Stainless steel material has the highest tensile strength.
- The cryogenic properties of stainless steel are high, making it suitable for modern technologies.
- Stainless steel material is highly ductile.
- The electrical conductivity of stainless steel is extremely low.
- Stainless steel material has high oxidation resistance due to chromium metal present in it.
- This material is biologically inert, making it best for kitchen appliances and cutlery.
- This material is resistant to acids, bases, and other organic compounds.
- Stainless steel material is recyclable, easy to work with, and can be cleaned easily.
Stainless Steel Production Process
The stainless steel fabricating process allows stainless steel manufacturers to produce it in a variety of parts and forms. Let’s go over the steps of that process now.
The first step involves melting raw materials together for 8-12 hours in an electric furnace.
Once the molten material reaches a recrystallization temperature, it continues to the next step, where it is cast into a certain form. Depending on their shape, these forms may be known as slabs, rods, blooms, billets, or tube rounds.
3. Hot Rolling
The unfinished forms are put through a hot rolling process. Slabs are formed into foil, strips, plates, and sheets, while blooms and billets are formed into coil, bars, and wire.
4. Heat Treatment and Air Hardening
In the next step, the steel is put through heat treatment and cooled through air hardening. The level of hardness of the steel depends on how long the steel is allowed to cool.
Once cooled, the steel is cleaned of buildup by way of electro cleaning or pickling.
In the final step, the steel is cut to the desired shape.
7. Secondary Processing
The steel can undergo further processes such as hot rolling, cold rolling, or annealing in order to achieve a matte or shiny finish.
Stainless steel is available in 150 different grades. The grade of stainless steel is determined by strength, alloy, resistance to temperature, and the application.
There are many different types of grades of stainless steel, and each belongs to one of the principal types of steel. Each one has different properties and is used in different industries.
These grades can then be classified into 4 different groups, depending on their mechanical properties and their resistance to corrosion.
Stainless steels 200 series types are a combination of manganese, chromium, and nickel, and are non-magnetic, making it the most attack-resistant series.
The 300-level series are very similar, but contain more chromium and nickel. The most corrosion-resistant type is the 316-stainless steel type, due to its high ratio of nickel.
Grade 304 Stainless Steel
- SS304 is commonly known as 18-8 stainless steel.
- It contains 18-20% Cr and 8-10.5% nickel in it.
- SS304 is non-magnetic under annealing conditions but can be made weakly magnetic by cold treatments.
- It cannot be hardened by heat treatments, but can be hardened by cold treatments.
- It has excellent corrosion resistance to mild atmosphere and freshwater, but halides can make them corrode easily.
- 18-8 stainless steel does not require preheating for welding purposes and has excellent welding properties.
- It is the most widely used austenitic steel in industries such as food, electronics, medical equipment, hardware tools, water treatment plants, and the petrochemical industry.
Grade 310 Stainless Steel
- SS310 is commonly known as 18-10 stainless steel.
- It is a high chromium-nickel austenitic steel that also has high carbon content.
- This grade shows high oxidation, creep, and heat resistance.
- SS310 is widely used in the petrochemical industry in carburizing conditions.
- It is commonly used in cryogenic applications because of its stiffness and lower magnetic permeability.
- It cannot be toughened by heat processing but with cold processes.
- This grade is easily weldable and can be found in different forms such as mesh, wires, strips, foil, plate, and sheets.
- 18-10stainless steel is used in industries for heat and chemical processes.
The 400 series contain a high amount of chromium, and a low amount of manganese, giving it a poor corrosion resistance. One example from within this series is 420-stainless steel.
Grade 430 Stainless Steel
- SS430 is commonly referred to as 18-0 stainless steel.
- It contains 18% of chromium, and the amount of nickel is negligible in it.
- It is less costly than the 300 series because of the absence of nickel elements.
- It is a low-carbon and non-hardenable steel.
- It cannot be hardened by heat processes, but cold forging methods can be applied to it.
- This grade can be welded, but to a very limited level; therefore, it should not be used for load-bearing applications.
- This grade has high oxidation and temperature resistance and can withstand many chemicals.
- The 18-0 grade is not suitable for low temperatures because they turn brittle when cooled down from elevated temperatures.
- It has a high elastic modulus meaning that it cannot bend and is stiff and stronger than other series.
- It is widely used in manufacturing dishwasher linings, automotive trim, formed parts, industrial roofing, wall cladding, utensils, mining equipment, and heat-resisting applications.
Finally, the 600 series can be resistant to chloride and water if given the right amount of heat treatment. Stainless steels of the 600 series are also known as precipitation hardening stainless steel.
Types of Stainless Steel
These series of stainless steels can be categorized under the umbrella of three main types—austenitic, ferritic, and martensitic. Each of these stainless steel types combine varying proportions of nickel, carbon and molybdenum.
Austenitic Stainless Steel
The first type, austenitic stainless steel, accounts for roughly 70% of fabricated stainless steel. It contains the highest ratio of the three main stainless steel types. Primarily, these are 200 series and 300 series stainless steels. Austenitic stainless steels contain a minimum of 16% chromium, a maximum of .15% carbon and enough manganese and/or nickel to maintain their structure.
The most common grade of austenitic stainless steel is 18/10. This alloy is highly corrosion resistant, impact resistant, durable, and they are resistant to extreme temperatures. Because of this, customers with cryogenic applications use this alloy extensively.
- Austenitic steel is produced by adding 8-20 % nickel to chromium-iron alloy.
- It is a face-centered cubic structure that offers corrosion resistance and a soft magnetic field.
- These steels have relatively low carbon content, which means they are weldable.
- These steels are used in applications where corrosion resistance is needed.
The best and most economical type of stainless steel is austenitic. These steels are widely used in the cutlery industry because of their corrosion resistance and welding properties.
Ferritic Stainless Steel
Ferritic type stainless steels contain anywhere between 10.5% and 25% chromium and a very small amount of nickel. Other common elements include: titanium, aluminum, lead and/or molybdenum. Ferritic stainless steels are known for their superior engineering qualities and their relatively low cost. While they have high corrosion resistance, theirs is not as strong as that of austenitic type stainless steel, due to ferritic stainless steel’s higher carbon content and lower nickel content.
- The ferritic phase of alloy stabilizes by the addition of chromium (>17%).
- This makes the material highly corrosion resistant but not exceptionally strong.
- Heat treatments cannot help in the hardening of the material.
- Cold treatments can be done to increase the hardness of a material.
- Ferritic is an inexpensive grade of stainless steel and therefore is used for kitchen equipment and ornamental applications.
Martensitic Stainless Steel
Martensitic stainless steel has a lower corrosion resistance than austenitic and ferritic stainless steels, but its higher levels of carbon and molybdenum make it exceptionally durable and tough. In addition, it is highly machinable. Martensitic stainless steel contains 12% to 14% chromium, .2% to 1% molybdenum, .1% to 1% nickel and less than 2% carbon. If a martensite stainless steel is of a certain type, it can be transformed into austenitic stainless steel with the addition of chromium and heat treatment.
- An addition of chromium-iron alloy of up to 2% increases its hardenability.
- The hardened martensitic can be sufficiently hardened to produce rust-resistant cutlery, surgical instruments, ball valves, and seats.
- The martensitic stainless steel is magnetic and has a carbon content that makes it difficult to weld.
Duplex Stainless Steel
A less common stainless steel grouping are duplex stainless steels. These stainless steels are designed to have be about half austenitic and half ferritic. However, many commercial alloys are closer to 40% austenite and 60% ferrite. Either way, duplex stainless steels are exceptionally strong and resistant to: stress corrosion cracking, localized corrosion, crevice corrosion and pitting.
- Duplex steel is a combination of both ferritic and austenitic phases.
- The strength of these steels is twice the strength of austenitic varieties.
- Duplex steel offers good corrosion resistance and weldability.
- These steels are used for special applications where strength is the main concern, such as in pressure vessels.
Products Produced from Stainless Steel
A wide assortment of stainless steel products and shapes of stainless steel can be found at a steel service center. Some of the shapes stainless steel suppliers provide include: stainless steel foil, stainless steel wire, stainless steel strip, stainless steel bars, stainless steel plate, stainless steel coil, stainless steel tube, stainless steel pipe (seamless pipe), stainless steel sheets, and stainless steel rods.
Using these shapes, manufacturers can make a variety of products, including: kitchen supplies, tableware, electronic appliances flatware, laundry equipment, sinks, kegs and, vats, silos, and large kitchen equipment.
Benefits of Stainless Steel
There are so many reasons to choose stainless steel. First, stainless steel is sustainable, as it is both recyclable and reusable. This is good for the environment, and it also translates to monetary savings for all parties involved. Another great thing about stainless steel is its versatility. Available in 150 different standard iterations, there’s a stainless steel for every application. Next, stainless steel is incredibly durable and strong. Finally, unlike many lesser metals, stainless steel doesn’t need a special coating or finish is order to resist attacks from corrosion, abrasion and the like.
Why is High-Quality Steel the Preferred Choice?
High-quality steel is a material that stays true to its intended properties. Whether you’re buying steel for a home project or industrial construction, high-quality steel is critical in engineering and safety.
The fundamental truth about steel quality is that low-quality steel is not suitable for various uses. A steel of the highest caliber is a highly durable element. It can effectively perform against measured stresses and be processed with micrometer accuracy.
Most of the time, low-quality steel cannot be appropriately engineered. A steel of lower quality may break during use, and it has proven to be more hazardous than commercially valuable.
Even though high-quality steel is unquestionably superior, ascertaining its true quality may require various methods. The steel may be tested for its:
All of those tests require one to be aware of the technicalities and properties of steel. The best way to learn about those is through the updated ISO standards.
Things to Consider Regarding Stainless Steel Manufacturers
When looking for a stainless steel contract manufacturer, there are a few points you need to consider, such as:
1. Does the manufacturer offer the services you need?
2. Can they meet your specifications and requirements?
3. Is the manufacturer willing to create a high quality stainless steel product while working within your budget?
4. Can they produce quality work within your timeframe?
5. Is the manufacturer certified by ISO or a comparable standards institute? If not, can they create certified products?
6. Do their products meet the rigorous safety and quality requirements set by the ASTM (American Society for Testing and Materials)?
7. Do they do custom manufacturing?
To find a high-quality company that you can trust, check out the stainless steel company profiles that we have peppered throughout this page.
What are the ISO Standards for Steel?
The International Organization for Standardization standards can guarantee steel quality. An ISO certification verifies that a manufacturing process meets all of those requirements. For example, ISO divides metal materials into six groups according to machinability. Steel is included in group “P,” which covers:
- Technical specifications of steel
- General characteristics
- Supply conditions
- Characterization methods
- The most common standard is ISO 9001:2015. The number 9001 classifies the standard. All standards within the ISO 9000 family refer to quality management. ISO 9001 is among ISO’s best-known standards, and it defines the criteria for meeting several quality management principles. Organizations are required by ISO 9001 to establish and adhere to a suitable and efficient quality management system, recognize areas for improvement, and take steps to make those improvements.
- ISO 377 specifies requirements for the identification, location, and preparation of samples and test pieces intended for mechanical tests on steel.
- ISO 404 specifies the general technical delivery requirements for all steel products covered by ISO 6929, except for steel castings and powder metallurgical products.
- ISO 10474 defines the different types of inspection documents supplied to the purchaser, following the order’s requirements to deliver steel products.
- ISO 4948-1 lays down the classification of steels into unalloyed and alloy steels based on chemical composition.
- ISO 6929 defines terms for steel products according to:
- stage of manufacture
- shape and dimensions
Stainless Steel Overseas Market
Stainless steel is both produced and traded in the United States and internationally. Many American steel service centers not only produce products for domestic patrons, but foreign ones as well. Likewise, many American companies import their stainless steel materials from international stainless steel fabricators. In 2015, North America registered as only the third largest producer of steel. They trailed behind Asia and Oceania, and the EU.
Because of the competition throughout the world, domestic steel prices have risen, making it more appealing to American customers to opt for steel imports. Despite the fact that you can get stainless steel cheaper by importing it, there are many reasons to work with domestic suppliers. First, you may find that communication is not always as easy when working with an overseas company. If you and your supplier do manage to sustain a miscommunication and you receive a product that does not meet your specifications, you will have more trouble getting a replacement. At the very least, it will take longer to return the product and receive a new one. In addition, when you work with an American company, you can feel more comfortable that they will adhere to U.S. safety and quality standards.
Stainless Steel Informational Video