Quick Guide: Types of Elements Found in Stainless Steel
- Nickel and chromium. Chromium is what ensures stainless steel remains stainless. ...
- Molybdenum. Molybdenum when combined with chromium will stabilize the passive film when in the presence of chlorides.
- Niobium and Titanium. These two are used to reduce sensitization of the stainless steel. ...
- Aluminum and Copper. ...
- Selenium and Sulphur. ...
Full Answer
What other metals are in stainless steel?
- AISI 440C contains 0.95 to 1.2 % carbon and 16 to 18 % chromium.
- AISI 304 has 8 % nickel and 18 % chromium.
- Aluminum AA 7075-T6 and AA 2024-T3 both contain almost no nickel.
- AISI 4130 alloy steel has 0.75 to 1.20 % chromium.
What element is added to steel to make it stainless?
Manganese, like nickel, is an Austenite forming element and has been used as a substitute for nickel in the AISI200 Series of Austenitic Stainless Steels, e.g. AISI 202 as a substitute for AISI 304. Chromium (Cr): Chromium is added to steel to increase resistance to oxidation. This resistance increases as more chromium is added.
What are the useful properties 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. ...
- Mechanical properties. As the term stainless steel encompasses a wide range of materials, the mechanical properties, of course, are quite diverse.
- Electric & Magnetic properties. Stainless steel is a relatively poor conductor of electricity. ...
What are the qualities of stainless steel?
Stainless Steel Characteristics Stainless steel is the name of a family of iron-based alloys known for their corrosion and heat resistance. One of the main characteristics of stainless steel is its minimum chromium content of 10.5%, which gives it its superior resistance to corrosion in comparison to other types of steels.
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.
Where is stainless steel used in buildings?
In vogue during the Art Deco period, the most famous use of stainless steel can be seen in the upper portion of the Chrysler Building . Thanks to its durability, many of these buildings have retained their original appearance.
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.
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.
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.
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 elements are added to stainless steel to make it hard?
Aluminum and copper and titanium when added to stainless steel precipitates its hardening. The three elements when put together form a bard microstructure as the soaking process continues at elevated temperature.
What is stainless steel?
Stainless steel is a type of metal alloy found in a number of forms. It is used to make light wall stainless steel tubing as well as pipes and several other things. It is a practical metal as it does not corrode with chemicals nor rust which causes most of the metallic things we use to get made of stainless steel. Components found in stainless steel include molybdenum, nickel, carbon, chromium, iron and quantities of different other metals.
What is the use of sulfur and selenium in stainless steel?
Selenium and Sulphur when added with Stainless Steel gives it the ability to mold freely. This results in it being used to make a wide range of parts including light wall stainless steel tubing.
What is the relationship between manganese and nickel?
Manganese performs a lot of functions with nickel. It will interact with Sulphur found in the stainless steel in order to form manganese sulfites that increase resistance to corrosion. Substituting manganese for nickel and combining with nitrogen will increase the strength of the stainless steel.
What is the purpose of chromium in stainless steel?
Chromium is what ensures stainless steel remains stainless. It is what creates a passive film to the metal to ensure it does not corrode. Other elements may add to the effectiveness of the film but none of them can really recreate the properties that enable the stainless steel to form fully. As you increase the percentage of chromium to your metal the passive film’s stability increases and the metal is protected better against wear and tear.
Why is stainless steel corrosion?
These two are used to reduce sensitization of the stainless steel. When the stainless steel is sensitized, corrosion can occur caused by precipitation of the chrome carbides as parts are cooled after welding. This depletes the weld area of chromium. Without this, the passive film will not be able to form and this will cause corrosion. Niobium and titanium react with carbon in order to form carbides so a passive film can form in the solution the chromium is left in.
Does chromium help prevent corrosion?
Molybdenum when combined with chromium will stabilize the passive film when in the presence of chlorides. This makes it effectively prevent corrosion and crevice. Molybdenum and chromium provide a large increase in resisting corrosion in stainless steel.
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.
What elements are in stainless steel?
In addition to iron, carbon, and chromium, modern stainless steel may also contain other elements, such as nickel, niobium, molybdenum, and titanium. Nickel, molybdenum, niobium, and chromium enhance the corrosion resistance of stainless steel. It is the addition of a minimum of 12% chromium to the steel that makes it resist rust, ...
Why does stainless steel rust?
The passive film requires oxygen to self-repair, so stainless steels have poor corrosion resistance in low-oxygen and poor circulation environments.
What is martensite steel?
Martensitic steels are low carbon steels built around the Type 410 composition of iron, 12% chromium, and 0.12% carbon. They may be tempered and hardened. Martensite gives steel great hardness, but it also reduces its toughness and makes it brittle, so few steels are fully hardened.
What is the main phase of ferritic steel?
Ferritic: Ferritic steels have ferrite (body-centered cubic crystal) as their main phase. These steels contain iron and chromium, based on the Type 430 composition of 17% chromium. Ferritic steel is less ductile than austenitic steel and is not hardenable by heat treatment.
What is the primary phase of austenitic steel?
Austenitic: Austenitic steels have austenite as their primary phase (face-centered cubic crystal). These are alloys containing chromium and nickel (sometimes manganese and nitrogen), structured around the Type 302 composition of iron, 18% chromium, and 8% nickel. Austenitic steels are not hardenable by heat treatment.
What is the chromium in steel?
It is the addition of a minimum of 12% chromium to the steel that makes it resist rust, or stain 'less' than other types of steel. The chromium in the steel combines with oxygen in the atmosphere to form a thin, invisible layer of chrome-containing oxide, called the passive film. The sizes of chromium atoms and their oxides are similar, ...
What is the name of the metal that Harry Brearley discovered?
In addition to iron, carbon, and chromium, modern stainless steel may also contain ...
Overview
Stainless steel is an alloy of iron that is resistant to rusting and corrosion. 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 relatively poor conductors of electricity, with significantly lower electrical conductivities than copper. In particular, the electrical contact resistance (ECR) of stainless steel arises as a 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, expo…
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…