- Carbon: This is the main alloying element of steel. ...
- Chromium: The addition of chromium makes steel become stainless steel. ...
- Nickel: Nickel is added to stainless steel to form or retain an austenitic microstructure at room and low temperatures. ...
- Molybdenum: Molybdenum is added to maintain the high-temperature toughness of stainless steel. ...
Is stainless steel stronger than steel?
Strength of steel and stainless steel: Steel is slightly stronger than stainless steel as it has lower carbon content. Also, it is weaker than steel in terms of hardness. What type of steel is a Grade 8 bolt?
What are the most common types of stainless steel?
Types of Stainless Steel and Stainless Steel Grades
- Ferritic Stainless Steel. The addition of chromium (>17%) to a steel alloy stabilizes the ferritic phase of the alloy, making a material that is highly corrosion-resistant, if not exceptionally strong.
- Martensitic Stainless Steel. ...
- Austenitic Stainless Steel. ...
- Duplex Stainless Steel. ...
- Stainless Steel Grades Summary. ...
What is the property of stainless steel?
What are the properties of stainless steel? Corrosion resistance The corrosion resistance of stainless steel is mostly a result of the chromium content. A stable layer of chromium oxide is formed on the surface of the steel, which prevents chemical reactions with the bulk of the material.
What are properties of stainless steels?
sturdy metallic properties, high resistance to temperature, resultant weld with excellent toughness and ductility, and so forth. The spokesperson further added, “Being a molybdenum-bearing grade, austenitic stainless steel alloy 316/316L has great nickel ...
What are the types of stainless steel?
Though there are more than 100 grades of stainless steel, the majority are classified into five major groups in the family of stainless steels: aus...
Why is chromium used in stainless steel?
When used in steel, chromium imparts remarkable resistance to corrosion and heat. Stainless steel usually contains 10 to 30 percent chromium.
Which type of stainless steel usually has the highest corrosion resistance?
Austenitic steels usually have the highest corrosion resistance. They contain 16 to 26 percent chromium and up to 35 percent nickel, and they are n...
What is stainless steel?
Stainless steel is an iron and chromium alloy. While stainless must contain at least 10.5% chromium, the exact components and ratios will vary based on the grade requested and the intended use of the steel.
How does stainless steel start life?
Most stainless steel starts life in a similar manner before heading off to processing. This processing—along with the exact composition of the steel alloy—determine its many characteristics. So to understand how stainless steel is produced, we must first dive into its composition.
What is the process of finishing stainless steel?
Finishing. Stainless steel is available in a variety of finishes from matte to mirror. Finishing is one of the last steps involved in the manufacturing process. Common techniques include acid or sand etching, sand blasting, belt grinding, belt buffing and belt polishing.
What is the process of molten steel being transferred to another chamber?
The other method used is Vacuum Oxygen Decarburization (VOD). In this method, molten steel is transferred to another chamber where oxygen is injected into the steel while heat is applied. A vacuum then removes vented gases from the chamber, further reducing carbon content.
Why remove scale from stainless steel?
Removing this scale is essential to creating the oxide barrier that gives stainless it’s characteristic corrosion and stain resistance.
Why is the exact composition of an alloy strictly measured and assessed throughout the alloying process?
The exact composition of an alloy is strictly measured and assessed throughout the alloying process to ensure the steel exhibits the required qualities.
Why is carbon important in welding?
Carbon helps to increase the hardness and strength of iron. However, too much carbon can create problems—such as carbide precipitation during welding. Before casting molten stainless steel, calibration and reduction of carbon content to the proper level is essential. There are two ways foundries control carbon content.
When was stainless steel invented?
The invention of stainless steel followed a series of scientific developments, starting in 1798 when chromium was first shown to the French Academy by Louis Vauquelin.
What is the largest family of stainless steels?
Main article: Austenitic stainless steel. Austenitic stainless steel is the largest family of stainless steels, making up about two-thirds of all stainless steel production (see production figures below). They possess an austenitic microstructure, which is a face-centered cubic crystal structure.
What is the solubility of nitrogen in stainless steel?
The limited solubility of nitrogen is increased by the pressure electroslag refining (PESR) process, in which melting is carried out under high nitrogen pressure. Steel containing up to 0.4% nitrogen has been achieved, leading to higher hardness and strength and higher corrosion resistance. As PESR is expensive, lower but significant nitrogen contents have been achieved using the standard argon oxygen decarburization (AOD) process.
Why are stainless steels used in pulp and paper?
Stainless steels are used extensively in the pulp and paper industry to avoid iron contamination of the product and because of their corrosion resistance to the various chemicals used in the papermaking process. For example, duplex stainless steels are used in digesters to convert wood chips into wood pulp. 6% Mo superaustenitics are used in the bleach plant and Type 316 is used extensively in the paper machine .
Why use stainless steel for kitchen sink?
Stainless steel is often preferred for kitchen sinks because of its ruggedness, durability, heat resistance, and ease of cleaning. In better models, acoustic noise is controlled by applying resilient undercoating to dampen vibrations. The material is also used for cladding of surfaces such as appliances and backsplashes.
How many grades of stainless steel are there?
See also: Steel grades and SAE steel grades. There are over 150 grades of stainless steel, of which 15 are most commonly used. There are several systems for grading stainless and other steels, including US SAE steel grades. The Unified Numbering System for Metals and Alloys (UNS) was developed by the ASTM in 1970.
What are the materials that are made of iron?
Other iron-based materials. Cast iron. Gray iron. White iron. Ductile iron. Malleable iron. Wrought iron. Stainless steel is a group of ferrous alloys that contain a minimum of approximately 11% chromium, a composition that prevents the iron from rusting and also provides heat-resistant properties.
What is the main element in stainless steel?
Pure iron (Fe), mixed with carbon to produce ‘steel’, is the main element of stainless steel. Chromium is added to steel to make it resistant to rust. Pure iron is prone to rusting, which is due to its reaction with oxygen in the presence of water (moisture), whereas iron’s reaction with oxygen is corrosive and eats away at the iron, chromium reacts with oxygen in such a way that only the outer surfaces become oxidized and further oxidation is prevented. Chromium forms a passive layer of chromium oxide, which prevents mechanical and chemical damage, over steel.
What is the most common material used in stainless steel?
Approximately, 16-20% chromium and about 10% nickel are the typical contents of this steel. This is the most widely used steel, with over 70% of the total stainless steel produced being austenitic. Applications of this type of steel can be found in: Petrochemical industries. Food processing industries.
What is precipitation hardening steel?
Precipitation Hardening Steel. It is made from heat-treated martensitic or austenitic stainless steel and is stronger than either. It also has a higher resistance to rust. Chromium and nickel are the primary components of this type of steel. Because of its strength, this type of steel is used in: Gears.
What is duplex steel?
Duplex Steel. This type of steel is used in chloride and sulfide environment and is the least corrosive. It is a mixture of ferritic and austenitic steels (hence the name), usually in 50-50 or 60/40 ratio. Primary constituents are chromium and molybdenum. Nickel may be present in a small quantity or may be absent.
Why is steel called austenitic?
Austenitic Steel. This steel is called austenitic because it is made from austenitizing elements. Austenitization changes the crystal structure of iron or iron-based material, such as steel, from ferric to austenitic. Since the basic iron-based structure is changed, austenitic steel is not magnetic.
What are the elements that make up steel?
The other minor constituents of steel are nickel, nitrogen, molybdenum and aluminum. Small contents of nickel increase the corrosion resistance further, and protect it from rough usage and harsh environmental conditions.
Why is stainless steel called stainless steel?
It is called stainless as it is highly resistant to stains, i.e., rusting.
What is stainless steel?
Stainless steel, any one of a family of alloy steels usually containing 10 to 30 percent chromium. In conjunction with low carbon content, chromium imparts remarkable resistance to corrosion and heat.
What are the different types of stainless steel?
What are the types of stainless steel? Though there are more than 100 grades of stainless steel, the majority are classified into five major groups in the family of stainless steels: austenitic, ferritic, martensitic, duplex, and precipitation-hardening .
What is the difference between martensitic steel and duplex steel?
Martensitic steels typically contain 11.5 to 18 percent chromium and up to 1.2 percent carbon with nickel sometimes added. They are hardenable by heat treatment, have modest corrosion resistance, and are employed in cutlery, surgical instruments, wrenches, and turbines. Duplex stainless steels are a combination of austenitic ...
What is the percentage of chromium in stainless steel?
It is comparable to austenitic stainless steel with respect to its corrosion resistance, and it contains 15 to 17.5 percent chromium, 3 to 5 percent nickel, and 3 to 5 percent copper. Precipitation-hardening stainless steel is used in the construction of long shafts. stainless steel.
How many grades of stainless steel are there?
There are more than 100 grades of stainless steel. The majority are classified into five major groups in the family of stainless steels: austenitic, ferritic, martensitic, duplex, and precipitation-hardening. Austenitic steels, which contain 16 to 26 percent chromium and up to 35 percent nickel, usually have the highest corrosion resistance.
What is the chromium content of stainless steel?
stainless steel, any one of a family of alloysteels usually containing 10 to 30 percent chromium. In conjunction with low carboncontent, chromium imparts remarkable resistance to corrosionand heat. Other elements, such as nickel, molybdenum, titanium, aluminum, niobium, copper, nitrogen, sulfur, phosphorus, or selenium, may be added to increase corrosion resistance to specific environments, enhanceoxidationresistance, and impart special characteristics.
Why is stainless steel refined?
Most stainless steels are first meltedin electric-arc or basic oxygenfurnaces and subsequently refined in another steelmaking vessel, mainly to lower the carbon content. In the argon-oxygen decarburizationprocess, a mixture of oxygenand argongas is injected into the liquid steel. By varying the ratio of oxygen and argon, it is possible to remove carbon to controlled levels by oxidizing it to carbon monoxidewithout also oxidizing and losing expensive chromium. Thus, cheaper raw materials, such as high-carbon ferrochromium, may be used in the initial melting operation.
What are the elements that make stainless steel?
Different proportions of stainless steel elements—iron, nickel, chromium, molybdenum, and carbon (among others)—determine the type of stainless steel. The ratio of iron to other materials affects how strong ...
How is Stainless Steel Made?
First, when making stainless steel, the manufacturer has to determine exactly which type of stainless steel they want to make. This is important because the grade of stainless steel they want to make will affect the ratio of stainless steel materials that will be present in the mixture, such as iron, carbon, nickel, etc. These ratios aren’t always exact—sometimes, they’re on a range because of the inevitable risk of variance in the purity of each element in the mix.
Why is stainless steel stirred?
To help fine-tune the quality of the final product, the molten steel may be stirred to help distribute and/or remove specific stainless steel components from the mixture. This helps to ensure that the stainless steel is of uniform quality and will meet the specifications required by end users (like Marlin Steel).
What happens after annealing stainless steel?
Cutting and Shaping. After the annealing process, stainless steel is put through a variety of cutting and shaping processes to create an ideal final product for the application.
What is the process of removing carbon from a material?
Removal of Excess Carbon. The molten material placed into a vacuum oxygen decarburization (VOD) or argon oxygen decarburization (AOD) system to remove excess carbon. Depending on how much carbon is removed, this process could result in a standard or a low-carbon variant of the alloy—for example, 304 versus 304L stainless steel. This can affect the tensile strength and hardness of the final product.
Why is stainless steel called "stainless"?
These stainless steel elements, such as nickel, chromium, and other additives, give it a passive oxide layer that resists the formation of rust and creates a shiny, reflective surface . The shiny surface of stainless steel is very difficult to tarnish compared to plain steel, hence why it is called “stainless” steel.
What is Marlin Steel?
Marlin Steel is a leading manufacturer of custom‐engineered products from steel wire and sheet metal. Its industrial material handling containers serve many industries including aerospace, defense, medical and automotive.
What is the chemical composition of stainless steel?
Classification, type and chemical composition of stainless steel. Stainless steel is divided into martensite and austenite, ferrite and duplex. 1. Martensitic chromium stainless steel is mainly low-carbon or high-carbon steel with chromium content in the range of 11.5%-18%.
What are the elements in steel?
Some steels also contain alloying elements such as Mo, Cu, Si, Nb, Ti, and N. This type of steel has the characteristics of austenitic and ferritic stainless steel.
What is ferritic stainless steel?
Ferritic stainless steel has a chromium content of 11% to 30%, and has a body-centered cubic crystal structure. Generally does not contain nickel, sometimes contains a small amount of Mo, Ti, Nb and other elements, large thermal conductivity, small expansion coefficient, good oxidation resistance, excellent stress corrosion resistance ...
Is stainless steel non-magnetic?
2. Austenitic stainless steel has stable austenite structure when Cr contains about 18%, Ni 8%~10%, and C about 0.1%. Non-magnetic and has high toughness and plasticity, but the strength is low, it is impossible to strengthen it by phase transformation, it can only be strengthened by cold working.
Is duplex stainless steel nickel saving?
Compared with austenitic stainless steel, the strength is high and the resistance to intergranular corrosion and chloride stress corrosion is significantly improved. Duplex stainless steel has excellent pitting corrosion resistance and is also a nickel-saving stainless steel.
What is stainless steel made of?
Corrosion resistance is achieved by creating a thin film of metal oxides that acts as protection against corrosive materials. A popular grade of stainless steel is stainless steel 316. Stainless steel 316 is generally composed of 16 – 18% chromium, 10 – 14% nickel, 2 – 3% molybdenum, and about 0.0 8% carbon. The added molybdenum makes this grade more corrosion resistant than the other types. Aside from those mentioned, other elements can be added to modify certain properties of the alloy. Stainless steel 316 is widely used in highly corrosive environments such as chemical plants, refineries, and marine equipment.
Why is nitrogen added to stainless steel?
Alloying nitrogen produces effects similar to carbon but with additional benefits. Nitrogen has a lesser tendency to react with chromium. Thus, its amounts can be increased to improve the strength of the stainless steel with lesser suscepti bility to sensitization. This, in turn, increases its resistance to intergranular corrosion. Moreover, when alloyed with molybdenum, it increases the stainless steel‘s resistance to pitting corrosion.
What is martensitic stainless steel?
Martensitic Unit Cell: These stainless steels have higher amounts of carbon that promotes a martensitic microstructure. Martensitic stainless steels are hardenable by heat treatment. When heated above its curie temperature, they have an austenitic microstructure. From an austenitic state, cooling rapidly results in martensite while cooling slowly promotes the formation of ferrites and cementite. Varying the carbon content results in a wide range of mechanical properties which makes them suitable for engineering steels and tool steels. Increasing the carbon content makes the stainless steel harder and stronger while decreasing it makes the alloy more ductile and formable. However, adding more carbon results in lower chromium to maintain a martensitic microstructure. Thus, higher strength is attained at the expense of corrosion resistance. They generally have lower corrosion resistance than ferritic and austenitic stainless steels.
What is 316L stainless steel?
Stainless steel 316L has a lower carbon content and is used in applications that subject the metal to risks of sensitization. The higher carbon variant is stainless steel 316H which offers greater thermal stability and creep resistance. Another widely used grade of stainless steel 316 is the stabilized 316Ti. Stainless steel 316Ti offers better resistance to intergranular corrosion.
Why do you need molybdenum in stainless steel?
This phenomenon is known as temperature embrittlement. Aside from maintaining toughness, adding molybdenum increases the stainless steel‘s resistance to pitting corrosion.
How does stainless steel passivate?
Passivation is done by allowing the stainless steel to be exposed to air where it builds chromium oxides on its surface. To enhance the formation of the passive film, the alloy is introduced to a chemical treatment process where it is thoroughly cleaned by submerging it in acidic passivation baths of nitric acid. Contaminants such as exogenous iron or free iron compounds are removed to prevent them from interfering in creating the passive layer. After cleaning with an acidic bath, the metal is then neutralized in a bath of aqueous sodium hydroxide. Descaling is also done to remove other oxide films formed by high-temperature milling operations such as hot-forming, welding, and heat treatment.
Why is ferritic stainless steel not heat treated?
Its ferritic microstructure is present at all temperatures due to the addition of chromium with little or no austenite forming elements such as nickel. Because of this constant microstructure, like the austenitic stainless steel, they do not respond to heat treatment.
How is stainless steel made?
Stainless steel is an alloy that is produced by combining a variety of different base metals to create a new material . Like with other alloys, the final product is considerably stronger than each of the source materials would be on their own.
When was stainless steel invented?
People have been experimenting with metal alloys for thousands of years. While examples of iron smelting can be found as far back as 1800 B.C . , the introduction of crucible steel goes as far back as 300 B.C. Stainless steel is a very versatile material.
What is the percentage of nickel in stainless steel?
These numbers identify the percentage of chromium and nickel that are present in a particular alloy. For example, 18/8 stainless steel is 18% chromium and 8% nickel; 18/0 stainless steel is 18% chromium and contains roughly .75% nickel, and so on.
What is 2507 stainless steel?
Duplex 2507 stainless steel is another form of super duplex steel . This material is made with 25% chromium, 4% molybdenum, and 7% nickel. This type of stainless steel is known for its resistance to chloride stress corrosion cracking, high thermal conductivity, and a low coefficient of thermal expansion.
Why is stainless steel duplex used?
Duplex stainless steels are very commonly used in more demanding applications due to their corrosion resistance properties, high mechanical properties, and how strong the material is. This makes the material very popular in a wide variety of industries.
What are the different grades of stainless steel?
Within the austenitic steel types, there are two main grades – grade 304 and grade 316. Grade 304 is known for its high tensile strength of roughly 621 MPa (90 ksi).
What is the best material for stainless steel?
This type of stainless steel is popular for the production of food-grade utensils and cooking implements. Chromium . Stainless steel made with chromium is much more resistant to corrosion, stains, and tarnishing.
Overview
Stainless steel is an alloy of iron that is resistant to rusting. It contains at least 11% chromium and may contain elements such as carbon, other nonmetals and metals to obtain other desired properties. Stainless steel's resistance to corrosion results from the chromium, which forms a passive film that can protect the material and self-heal in the presence of oxygen.
Properties
Like steel, stainless steels are a relatively poor conductor of electricity, with significantly lower electrical conductivity than copper. In particular, the electrical contact resistance (ECR) of stainless steel arises as to the result of the dense protective oxide layer and limits its functionality in applications as electrical connectors. Copper alloys and nickel coated connectors tend to exhibit lower ECR values, and are preferred materials for such applications. Nevertheless, stainless stee…
History
The invention of stainless steel followed a series of scientific developments, starting in 1798 when chromium was first shown to the French Academy by Louis Vauquelin. In the early 1800s, British scientists James Stoddart, Michael Faraday, and Robert Mallet observed the resistance of chromium-iron alloys ("chromium steels") to oxidizing agents. Robert Bunsen discovered chromium's resistance t…
Types
There are five main families, which are primarily classified by their crystalline structure: austenitic, ferritic, martensitic, duplex, and precipitation hardening.
Austenitic stainless steel is the largest family of stainless steels, making up about two-thirds of all stainless steel production. They possess an austenitic microstructure, which is a face-centered cubic crystal structure. This microstructure is achieved by alloying steel with sufficient nickel an…
Corrosion resistance
Unlike carbon steel, stainless steels do not suffer uniform corrosion when exposed to wet environments. Unprotected carbon steel rusts readily when exposed to a combination of air and moisture. The resulting iron oxide surface layer is porous and fragile. In addition, as iron oxide occupies a larger volume than the original steel, this layer expands and tends to flake and fall away, exp…
Standard finishes
Standard mill finishes can be applied to flat rolled stainless steel directly by the rollers and by mechanical abrasives. Steel is first rolled to size and thickness and then annealed to change the properties of the final material. Any oxidation that forms on the surface (mill scale) is removed by pickling, and a passivation layer is created on the surface. A final finish can then be applied to achieve th…
Joining
A wide range of joining processes are available for stainless steels, though welding is by far the most common.
The ease of welding largely depends on the type of stainless steel used. Austenitic stainless steels are the easiest to weld by electric arc, with weld properties similar to those of the base metal (not cold-worked). Martensitic stainless steels can also be welded by electric-arc but, as t…
Production
Most of the world's stainless steel production is produced by the following processes:
• Electric arc furnace (EAF): stainless steel scrap, other ferrous scrap, and ferrous alloys (Fe Cr, Fe Ni, Fe Mo, Fe Si) are melted together. The molten metal is then poured into a ladle and transferred into the AOD process (see below).
• Argon oxygen decarburization (AOD): carbon in the molten steel is removed (by turning it into carbon monoxide gas) and other compositional adjustments are ma…