Stainless Steel Materials 101: A Basic Knowledge Guide
The History of Stainless Steel
The origins of stainless steel came about in 1913 when Harry Brearley came across a steel that was rustless in Sheffield, UK. While many attempts had been made in the past, only Brearley was able to create the original stainless steel that we see and use today. With chromium added while in a molten state, he was able to develop a steel that was unable to rust. With chromium added, it is able to resist corrosion. After stainless steel made it to the market, the city of Sheffield became known for the origin of stainless steel.
The discovery of stainless steel was not on purpose because Brearley was actually working to figure out how to eliminate gun barrel erosion prior to the onset of World War 1. Once discovered, many refinements were made quickly. These refinements began to be seen starting in 1919 by Elwood Haynes, who discovered martensitic stainless steel. Ten years later, precipitation-hardening stainless steel was discovered by William Kroll. Then, a year later in 1930, a duplex stainless steel was developed through Avesta Ironworks, in Sweden.
What is stainless steel?
Known as an alloy, stainless steel is a combination of iron and chromium and sometimes it has some nickel thrown in.
The makeup of stainless steel is completely recyclable and is totally “green” Not only that, but in the field of construction the total amount of stainless steel can be nearly recovered. Also, stainless steel is inert and neutral within the environment. Additionally, the stainless steel properties do not separate so there will not be any changes in composition when other elements come in contact with it.
Besides the benefits environmentally, stainless steel also looks good, is maintainable, hygienic, strong, and has many uses. Because of this, stainless steel is used in many products.
In addition to these environmental benefits, stainless steel is also aesthetically appealing, extremely hygienic, easy to maintain, highly durable and offers a wide variety of aspects. As a result, stainless steel can be found in many everyday objects. Besides the construction industry, stainless steel can be found within many other industries such as transportation, medicine, logistics, research, and energy.
The Process of Making Stainless Steel
Making stainless steel is a process that involves a mixture of chromium, iron ore, silicon, nickel, and molybdenum after being melted down.The resulting stainless steel will then become a strong alloy.
The type of stainless steel that you make will also be determined by the elements that are used, such as chromium, nickel, iron, carbon, or molybdenum. The amount of strength, its resistance to corrosion, and other properties will be determined by the iron ratio.
With the different stainless steel ratios, there are many types of stainless steel that can be produced. Each stainless steel variation is known as “grades” and includes grade 304, 316, and 420 grade.
At the beginning, in order to manufacture stainless steel the type of stainless steel grade needs to be known first. Once the type is known, it will know how the stainless steel will be affected by the materials that are mixed in. However, the mix is not exact and is only on a scale due to the difference in stainless steel purity.
After gathering all of the materials, the manufacturing of stainless steel can be initiated.
Below is the process of making stainless steel.
Step 1: Raw Elements are Melted
The raw elements are melted using a furnace that is heated to the melting point. The melting can take as long as 12 hours and once in a molten state, any excess carbon will be separated.
Step 2: Extra Carbon is Removed
The molten material is then placed in a decarburization to have any extra carbon removed. The amount of carbon removed could affect which variant is made, such as either a 304 grade or 304L grade. With a difference, the strength of the stainless steel can also be affected.
Step 3: The Molten is Stirred
In order for the quality of the molten to be enhanced, it needs to be stirred. The stirring will assist in the distribution of the materials within the molten steel. This will also ensure the quality of the stainless steel is uniform and is created at the standards set by the users of the steel once it is created.
Step 4: Creating the Stainless Steel
Once cooling of the stainless steel begins, it is formed by using many different actions. The first action is known as hot rolling before the metal begins to crystalize. Hot rolling is able to produce a general shape for the stainless steel, and involves the creation of metal blooms or billets. In order for these blooms and billets to come about, there needs to be a cold rolling conducted.
Step 5: Annealing the Stainless Steel
Annealing will be conducted so that stresses within can be relieved and have its properties altered. When annealing is conducted, descaling may be required so that the oxide is able to keep the stainless steel protected.
Step 6: Cutting the Stainless Steel
The stainless steel is now cut in order for the product to be finalized. The cutting of the stainless steel will be depending upon the final need of the product and its size. An example of this is seen when mechanical cutting is conducted using shears to produce plates. Also, a machine that can laser cut the metal can be used to produce sheets of stainless steel. Cutouts can also be obtained by using a laser cutter or a punch machine.
Step 7: Surface Finish is Applied
With the manufacturing completed, the stainless steel will then have a surface finish applied. This finish will be applied prior to the stainless steel being shipped. The applied finish will be decided upon what the use of the stainless steel will be. However, a finishing technique that is used often is just having it smoothen in order for impurities to be eliminated from the surface.
Properties of Stainless Steel
Many properties exist within stainless steel, which makes it a highly desirable alloy. These properties also contribute to its application of creating components and parts within many industries. Plus, it is highly corrosion resistant due to the amount of chromium. Besides these properties, other properties also exist which makes stainless steel highly desirable.
Properties that are Aesthetic
With many finishes available, stainless steel can easily achieve a unique application. These applications can involve tinting or embossing, which will make stainless steel unique. Stainless steel is frequently incorporated into interior design and building envelopes.
Properties that are Mechanical
When it comes to the material properties, having strong properties for mechanical applications is important. Because of the material being stainless steel, it is able to fuse elasticity, hardness, and ductility, which allows it to be implemented in various modes of forming, such as extrusion, stamping, and bending. Plus, it is able to behave greatly whether the temperature is low or high.
Fire Resistance Properties
When it comes to fire resistance, nothing can compare to stainless steel. This is why stainless steel will often be used for structures. Stainless steel also has a high ranking as compared to other materials and does not emit any fumes that are toxic in nature.
Resistance to Corrosion
Having a chromium amount of 10.5% allows stainless steel to resist corrosion due to
its layer of chromium. This chromium is created naturally as chromium reacts to oxygen. When scratching takes place, it is able to smooth itself out again. This regenerating ability is what enables stainless steel to resist corrosion.
Different types of stainless steel and their physical characteristics and applications
304 Stainless Steel Strong forming capabilities, able to retain properties, and no need for annealing to restore resistance of corrosion Commonly used for kitchen sinks, containers, heat exchangers, fasteners, equipment for food processing, and
316 Stainless Steel Resistant to corrosión, resistance to heat, and ease of fabrication Threaded fasteners, heat exchangers, and boat fittings
316L Stainless Steel Corrosion resistance, heat resistance, cold and hot working, heat treatment, and machinability Pharmaceutical, marine application, pollution control, fasteners, and food prep equipment
420 Stainless Steel Can be cleaned easily, strong, and resistant to corrosion Knife blades, medical equipment, and food processing equipment
430 Stainless Steel Chemical and acid resistance, heat resistance, corrosion resistance, and withstands oxidation Automotive trim, utensils, range hoods, dishwasher linings, and mining equipment
434 Stainless Steel Tempered, corrosión resistance, heat treated, and cold forming Dishwashers, range hoods, roofing and siding, gutters, and gas burners
Common types Stainless Steel Characteristic & Applications
Stainless Steel Types
Physical Characteristics
Applications
201
Acid and alkali resistant, high density
Decorative pipe, industrial pipe and some shallow tensile productsp
304
Good corrosion resistance and heat resistance
Household appliances, tableware, kitchenware
304L
Good corrosion resistance, non-magnetic
Outdoor machines, building materials, heat-resistant parts
316
Corrosion resistance, high temperature resistance, non-magnetic
Seawater equipment, food industry
316L
Corrosion resistance is better than 304 stainless steel
Food, chemical, medical and other industrial equipment
410
High strength, good processability, magnetic
Machinery parts, petroleum refining units
420
High hardness, good corrosion resistance, magnetic
Tableware (knives), turbine blades
430
Low thermal expansion rate, excellent formability and oxidation resistance
Heat resistant appliances, burners, home appliances
Frequently Asked Questions
Q: Will stainless steel rust?
A: Although stainless steel has a high amount of resistance for corrosion, the alloy can still possibly corrode if it is submerged under water for a long time, exposed to high heat, saline, chemicals, or grease.
Q: Is stainless steel magnetic?
A: Although stainless steel is a metal, it may or may not have magnetic properties incorporated into it. These magnetic properties will be determined by the grade of stainless steel.
Q: What is the difference between stainless steel and Iron?
A: Although stainless steel and iron are both metal, they have one difference that separates the two and that is iron being an element and steel is an alloy that can have iron incorporated into its mix. Depending on the steel that is made, it is usually made from iron and carbon and to make stainless steel, chromium will usually get mixed into the batter. Jump to top
Author
Gavin Leo is a technical writer at Aria with 8 years of experience in Engineering, He proficient in machining characteristics and surface finish process of various materials. and participated in the development of more than 100complex injection molding and CNC machining projects. He is passionate about sharing his knowledge and experience.