STAINLESS STEEL:
The Definitive Guide

What is stainless steel? What are its advantages? Why should I choose stainless steel? Which type of stainless steel is right for me?

If you have been thinking of any of these questions while exploring the latest addition to your equipment or spare parts, I’ve brought you the answer. In this ultimate guide to stainless steel, we cover everything you should consider while buying, in addition to five of the top-selling collections on the market.

Contents

Basic Introduction to Stainless Steel

Chapter 1

Basic introduction to Stainless Steel

Stainless Steel Families, Series, Grades

Chapter 2

Stainless Steel families And Grades

Properties of Stainless Steel

Chapter 3

Properties of Stainless Steel

Stainless Steel Composition Elements and Effect

Chapter 4

Composition Elements and Effect

Stainless Steel Characteristics And Advantages

Chapter 5

Characteristics And Advantages

How Stainless Steel is Made

Chapter 6

How Stainless Steel Is Made?

Stainless Steel Common Applications

Chapter 7

Market and Applications

How to Select Stainless Steel

Chapter 8

How to Select Stainless Steel?

CHAPTER 1:

Basic Introduction to Stainless Steel

Basic Introduction to Stainless Steel

What Is Stainless Steel?

Stainless steel: is a group of iron-grounded alloys that consists of a minimum of nearly 11% chromium, a formulation that stops the iron from rusting, along with offering heat-resistant estates.

Different kinds of stainless steel embrace nitrogen, carbon (from 0.03% to greater than 1.00%), aluminum, sulfur, silicon, copper, titanium, nickel, selenium, molybdenum, and niobium.

Particular kinds of stainless steel are commonly appointed by a three-digit number, e.g., 304 stainless.

The resistance of stainless steel to ferric oxide creation results from the chromium present in the alloy, which creates a passive film that saves the underlying substance from corrosion stroke and can self-heal in the existence of oxygen. the resistance of corrosion can be risen further by:

  • Enhancing the chromium substance to levels over 11%
  • Addition of over 8% quantities of nickel and supplement of molybdenum (which develops resistance to “pitting corrosion”).
  • The addition of nitrogen also develops resistance to pitting corrosion and raises mechanical toughness. Therefore, there are different stainless steel levels with changing molybdenum and chromium contents to fit the atmosphere the alloy must bear.

Resistance to staining and corrosion, familiar luster, and low maintenance make stainless steel an excellent substance for many applications where corrosion resistance and steel strength are needed.

Furthermore, stainless steel can be rolled into plates, sheets, tubing, bars, and wire. These can be used in surgical instruments, cookware, significant appliances, cutlery, construction material in large buildings, storage tanks and tankers for food and chemical products, and industrial equipment (e.g., in chemical plants, paper mills, water treatment).

The substances resistance to corrosion, the lighten with which it can be sterilized and steam-cleaned, and the lack of the want for surface covering have induced the stainless steel used in food and kitchens processing plants.

History of Stainless Steel

The creation of stainless steel following a series of scientific progress, beginning in 1798, where Louis Vauquelin first displayed chromium to the French Academy.

In the first 1800s, Robert Mallet, James Stoddart, and Michael Faraday marked oxidizing agents’ resistance by chromium-iron alloys (“chromium steels”). Robert Bunsen found out chromium’s resistance to keen acids.

The iron-chromium alloys’ corrosion resistance may have been primarily admitted by Pierre Berthier in 1821, who noted the iron-chromium opposition over onslaught by some acids and suggested their cutlery use.

In the 1840s, both Krupp and Sheffield steelmakers built chromium steel, applying it in the 1850s for cannons.

In 1861, Robert Forester Mushet extracted a chromium steel’s patent.

These events resulted in the first creation of chromium-embodying steel by J. Baur of Brooklyn’s Chrome Steel Works to build bridges.

A U.S. product’s Patent was granted in 1869. This was tracked with recognition of the chromium alloys’ corrosion resistance by Englishmen John Clark and John T. Woods, who observed chromium ranges from 5–30%, with added medium carbon tungsten. They followed up the commercial worth of the innovation via a British “Weather-Resistant Alloys” patent.

In the late 1890s, German chemist “Hans Goldschmidt” improved an aluminothermic (thermite) method for manufacturing carbon-free chromium.

Between 1904 and 1911, many researchers, including Leon Guillet of France, developed alloys that would be examined for stainless steel today.

Friedrich Krupp Germaniawerft, in 1908, produced the 366-ton sailing yacht Germania presenting a chrome-nickel steel structure in Germany.

Philip Monnartz, in 1911, described the relationship between corrosion resistance and chromium content.

On 17 October 1912, Eduard Maurer and Krupp engineers Benno Strauss certified austenitic stainless steel as Nirosta.

The same developments in the United States were taking place. Frederick Becket and Christian Dantsizen were mechanizing ferritic stainless steel. Elwood Haynes, in 1912, asked for a US patent on “a martensitic stainless steel alloy,” which was not awarded until 1919.

While asking for a corrosion-resistant alloy for weapon muzzles in 1912, Harry Brearley of the Brown-Firth research laboratory in Sheffield, England, subsequently industrialized and discovered a martensitic stainless steel alloy.

Two years, the discovery was announced in a newspaper article in January 1915 in The New York Times.

The metal was later sold under the “Staybrite” brand in England, by Firth Vickers and was used for the new entry sunshade in 1929 for the Savoy Hotel in London.

During 1915, Brearley requested a US patent only to discover that Haynes had already registered one. Haynes and Brearley combined their funding and created the American Stainless Steel Corporation, with Pittsburgh, Pennsylvania.

At first, stainless steel was marketed in the US under various brand names like “Nirosta steel” and “Allegheny metal.” Even inside the metallurgy field, the name stayed unsettled; one trade journal called it “unstainable steel” in 1921. Before the Great Depression, in 1929, over 25,000 tons of stainless steel were produced and marketed in the US annually.

Significant technological progressions in the 1950s and 1960s permitted the production of vast tonnages at a low-priced cost:

  • AOD procedure(argon oxygen decarburization), for the removal of sulfur and carbon
  • Ongoing casting and hot strip rolling
  • The Z-Mill, or Sendzimir cold rolling mill
CHAPTER 2:

Stainless Steel: Families, Series, Grades

Stainless Steel Families, Series, Grades

5 Main Different Families of Stainless Steel

To meet the vast diversity of applications for which stainless steel grades are used, there are over 100 types of them. These several grades and types are made by inserting in alloys like nickel, silicon, nitrogen, manganese, and carbon in addition to chromium to grant properties such as strength, ductility, heat resistance, and flexibility.

There are 5 prominent families, mainly categorized by their crystalline structure: Austenitic, Ferritic, Martensitic, Precipitation hardening, and Duplex.

Austenitic stainless steel

Austenitic stainless steel is the most fantastic stainless steel family, making up about 2\3 of all stainless steel productivity. They obtain an austenitic microstructure, which is a cubic face-centered crystal design. This microstructure is accomplished by alloying steel with competent nitrogen and manganese and nickel to still an austenitic microstructure, starting from the cryogenic area to the melting region. Thus, because austenitic stainless steels, at all temperatures, have the same microstructure, they are not hardened at all the various temperatures.

Austenitic stainless steels are divided into two main subcategories, 300 series and 200 series:

200 series are nickel-manganese-chromium alloys that increase nitrogen and manganese use to reduce the use of nickel. As a result of their nitrogen addition, they obtain nearly 50% yield strength higher than 300 series stainless plates of steel.

  • Type 201 is hardenable by cold working.
  • Type 202 is used for general purposes. Reducing nickel content and enhancing manganese causes weak corrosion resistance.

As 300 series is nickel-chromium alloys that reach their austenitic microstructure approximately only by nickel alloying; some very vastly-alloyed grades contain some nitrogen to decrease nickel needs. 300 series is the most widely used and biggest group.

Type 304: The best-common grade is Type 304, also recognized as 18/10 and 18/8 for its composition of  8%/10% nickel and 18% chromium, respectively.

Type 316: The next most known austenitic stainless steel is Type 316. The supplement of 2% molybdenum offers more excellent acid resistance and localized corrosion owed to chloride ions. Minimal-carbon versions, such as 304L or 316L, have below 0.03% carbon ratios and are used to resist corrosion problems owed to welding.

Ferritic stainless steels

Ferritic stainless steels obtain a ferrite microstructure the same as carbon steel, a cubic face-centered crystal design, containing 10.5% to 27% chromium with little or no nickel. This microstructure exists at all temperatures because of the chromium supplement, so it cannot be hardened by heat treatment.

Cold work cannot strengthen them as austenitic stainless steel to the same degree. They are magnetic.

Additions of zirconium (Zr), titanium (Ti), and niobium (Nb) to Type 430 offer good weldability.

Because of the near-absence of nickel, they are not as expensive as austenitic steels and are exist in many products, which include:

  • Automobile exhaust pipes (In North America, type 409Cb and 409 are used; in Europe, stabilized grades Type 441 and 439 are used)
  • Structural and architectural and applications (Grade 430, which consists of 17% Cr)
  • Building elements, such as chimney ducts, roofing, and slate hooks
  • In solid oxide fuel cells, power plates operating at temperatures about 1,292 °F (700 °C) (high-chromium ferritic including 22% Cr)

Martensitic stainless steels

Martensitic stainless steels provide a massive range of characteristics. They are used as stainless tool steels, creep-resistant steels, and stainless engineering steels.  Martensitic stainless steels are magnetic and not corrosion-resistant like austenitic and ferritic stainless steel because they contain low chromium content. They are divided into four types (with some overlap)

  1. Fe-Cr-C grades. The first grades that were used and remain widely used in wear-resistant and engineering applications.
  2. Fe-Cr-Ni-C grades. Nickel is a replacement for some carbon. They maintain higher corrosion resistance and higher toughness. Type EN 1.4303 (CA6NM is its Casting grade) with 4% Ni and 13% Cr is used for most Kaplan, Francis, and Pelton turbines in hydroelectric power plants due to its good casting characteristics, resistance to cavitation erosion, and good weldability.
  3. Precipitation hardening types. Type EN 1.4542 (also recognized as 17/4PH), the best-recognized grade, merges precipitation hardening and martensitic hardening. It achieves good toughness and high strength, and they use it in aerospace amid other applications.
  4. Creep-resisting grades. The tiny additions of vanadium, cobalt, boron, and niobium enhance the creep resistance and strength up to 650 °C (1,202 °F).

Precipitation hardening stainless steels

Precipitation hardening stainless steels obtain similar resistance of corrosion as austenitic varieties. Still, they can be rush hardened to higher strengths than other grades of martensitic. There are three kinds of precipitation hardening stainless steels:

  1. Martensitic 17-4 PH[49] (AISI 630 EN 1.4542) contains about 17% Cr, 4% Ni, 4% Cu, and 0.3% Nb.
  2. Semi-austenitic 17-7PH[49] (AISI 631 EN 1.4568) contains about 17% Cr, 7.2% Ni, and 1.2% Al.
  3. Austenitic A286[50](ASTM 660 EN 1.4980) contains about Cr 15%, Ni 25%, Ti 2.1%, Mo 1.2%, V 1.3%, and B 0.005%.

Duplex stainless steels

Duplex stainless steels obtain a compound microstructure of ferrite and austenite, and the ideal rate is a 50:50 mixture. However, commercial alloys might have 40:60 ratios. 

It has molybdenum (up to 5%), higher chromium (19-32%), and less nickel content than austenitic stainless steels. 

Double-sided stainless steel has twice the yield strength of austenitic stainless steel. 

Its mixed microstructure offers improved chloride stress corrosion cracking resistance compared to 304 and 316 austenitic stainless steel.

The grades of Duplex are usually shared into three subgroups depending on their corrosion resistance: super duplex, standard duplex, and lean duplex.

The characteristics of duplex stainless steels are reached with an overall less alloy content than high-performance super-austenitic grades, which makes their cost-effective use for many applications. 

The paper and pulp industry was one of the first industries to use duplex stainless steel widely. 

Today, the gas and oil industry is the primary user and has pushed towards more corrosion resistance degrees, resulting in the improvement of super duplex and hyper duplex grades. 

More recently, cheaper (and a little less corrosion-resistant) duplexes have been developed, mainly for structural applications in construction and building (concrete reinforcing bars, coastal works, bridge slabs) and the water industry.

Stainless Steel Grades

Stainless steel has many different series and grades, such as 100, 200, 300, 400, 500, 600, and 900 series. In detail this article is going to discuss them.

Type 100 Series

Type 102—austenitic stainless steel used for general purposes.

Type 200 series

Nickel type 200 is one of the strongest metals, that consists of 99.9% mere nickel. Nickel 200’s features embrace perfect characteristics, a low vapor- pressure, low gas content, magnetic components, high electrical, and thermal conductivity. These features and its chemical formulation make nickel 200 highly corrosion resistant and fabricate.

Nickel 200 is helpful in any atmosphere below 600º F. It is highly corrosion resistant by alkaline and neutral salt solutions.  Nickel 200 has low corrosion ratios in distilled and tepid water.

The metal can be formed cold by all techniques and hot-formed to any form.

Common applications of type 200 series stainless steel:

  • Salt production
  • Food processing equipment
  • Caustic handling equipment
  • Offshore and marine engineering
  • Vessels and reactors in which fluorine is produced and responded to hydrocarbons

Handling and manufacture of sodium hydroxide, specifically at temperatures over 300° F

Type 300 series

Class 300 stainless steel is categorized as austenitic, and cold-working techniques can only harden it. These stainless steel types contain chromium (about 18 to 30%) and nickel (about 6 to 20%) as significant additives in alloying.

Type 304 is the most commonly used alloy among various kinds of stainless steel. Series 300 stainless steel alloy is corrosion-resistant, sustains its strength at high temperatures, and is easy to maintain.

Grade 301

Highly flexible, formulated products. It also hardens quickly during mechanical work—better wear resistance, Good weldability, and fatigue strength than 304.

Grade 302

Same wear resistance as 304, with a little higher strength because of the additional carbon.

Grade 303

A robotic version of 304 by adding phosphorus and sulfur. Also named as “A1” based on ISO 3506.

Grade 304

The most known grade; Classical stainless steel 18/8 (8% nickel, 18% chrome). It is known outside the US as “A2 stainless steel,” according to ISO 3506 (not to be mixed-up with A2 tool steels). The Japanese grade equivalent for this material is SUS304.

Grade 304L

Same as grade 304 but reduced carbon content to enhance weldability. A Little is weaker than 304.

Grade 304LN

Like 304L, but nitrogen is also added to get much higher tensile and yield strength than 304L.

Grade 305

Similar to 304, but with extra nickel to reduce work hardening.

Grade 308

Usually used when welding 304, as filler metal.

Grade 309

Better resistance of temperature than 304, in some cases used as filler metal when welding various grades of steels, alongside Inconel.

Grade 310, 310S

It is a stainless high-alloy austenitic steel used for high temperatures. The high content of chromium and nickel gives the steel excellent resistance to oxidation in addition to high strength at high temperatures. This Type is very ductile and has excellent weldability allowing it to be widely used in many applications.

Grade 316

The second most common class (after 304); For surgical and food stainless steel uses; Adding molybdenum alloys prevents specific corrosion forms. It is also recognized as marine grade stainless steel because of its increased chloride corrosion resistance compared to Grade 304. 316 is usually used to build nuclear reprocessing plants.

Grade 316L

Deficient carbon type of 316, generally used in stainless steel marine applications and watches, as well as exclusively in the manufacture of reactor pressure containers for boiling water reactors, because of its high corrosion resistance. Also known as “A4,” according to ISO 3506.

Grade 316Ti

Variant of grade 316 incorporating titanium for the resistance of heat. It is used in elastic chimney liners.

Grade 321

Similar to 304 but less dangerous than weld decay because of the addition of titanium. See 347 with the addition of niobium for desensitization while welding.

Type 400 series

The 400 series stainless steel contains 11% more chromium and 1% manganese, higher than the 300 series group. The 400 series is subject to rust and corrosion in some conditions. Heat treatment will harden the 400 chains. The 400 series stainless steel has a high carbon content, which gives it a martensitic crystal structure. This offers high strength and high corrosion resistance. Martensitic stainless steels are not as resistant to corrosion as the austenitic types.

Grade 405

From iron for welding applications

Grade 408

Heat resistant; Weak corrosion resistance; 8% nickel, 11% chrome.

Grade 409

The cheapest type; Used for car exhaust. From iron (chromium/iron only).

Grade 410

Martensite (high-strength chromium/iron). Wear-resistant, but lower resistant to corrosion.

Grade 416

Easy to manufacture because of additional sulfur

Grade 420

Silverware type martensitic; Similar to Brearley’s original stainless steel. Excellent polishing ability.

Grade 430

Decorative, for example, for car decoration; ferritic. Good formability, but with low corrosion and temperature resistance.

Grade 439

Iron grade, higher type version 409, is used for catalyzed transformer exhaust areas. Increased chromium to improve high temperature oxidation/corrosion resistance.

Grade 440

Grade 440 is a higher grade of cutlery steel, with extra carbon, permitting more good edge retention when heat treated appropriately. It can be hardened to almost Rockwell’s 58, devising it as one of the most hardened stainless steels. Because of its toughness and relatively lower price, most show-only and replica knives or swords are made of 440 stainless steel. Available in four types:

  1. Grade 440A – Contains the lower amount of carbon, which makes it the most stain-resistant.
  2. Grade 440B – a bit more carbon than 440A.
  3. Grade 440C – contains the most massive amount of carbon than the Type 440 variants. The strongest and most popular type in knifemaking than 440A variants, excluding diving or other saltwater applications. This alternative is also more readily available than the other 440 options.
  4. Type 440F – variable autorun. It has the same elevated content of carbon as the 440C type.

Grade 446

For high-temperature service

Type 500 series - heat-resisting chromium alloys

The 500 series is made of heat resistant chrome alloy and is not very commonly used or large.

Type 600 series - initially created for proprietary alloys (which are no longer given SAE grade numbers)

600 series stainless steel alloys are commonly used for applications requiring high temperatures and corrosion resistance, and series alloys have excellent mechanical characteristics and provide the desired combination of good workability and high strength.

Another benefit of the 600 is that its higher nickel content offers less corrosion stress cracking in the annealed situation.

  • 601 via 604: low-alloy martensitic steels.
  • 610 via 613: Martensitic hardened secondary steels.
  • 614 via 619: chromium martensitic steels.
  • 630 via 635: stainless steel that hardens semi-austenitic and martensitic precipitation.
  • 650 via 653: Hot / cold work strengthened austenitic steels.

660 via 665: Austenitic superalloys; All types except for alloy 661 are hardened by second stage precipitation.

Type 900 series - austenitic chromium-molybdenum alloys

Type 904 – Similar to 316 but with improved content of molybdenum  and chromium for more corrosion resistance

CHAPTER 3:

Properties of Stainless Steel

Properties of Stainless Steel

Stainless Steel Mechanical Properties

Needed mechanical characteristics are usually given in purchase standards for stainless steel. Minimal automatic features are also provided by the different specifications related to the product and material form. 

Meeting these model mechanical characteristics shows that the substance has been appropriately manufactured to a proper quality system. Engineers can then trustingly utilize the importance of facilities that meet safe working pressures and loads.

Mechanical characteristics defined for flat-rolled products ordinarily yield stress (or proof stress), tensile strength, Brinell and elongation, or Rockwell hardness. Characteristic needs for tube, bar, pipe, and fittings typically state yield stress and tensile strength.

Yield Strength of Stainless Steel

Unlike mild steels, annealed austenitic stainless steel’s yield strength is a deficient proportion of the tensile strength. Mild steel yield strength is typically 65-70% of the tensile strength. This figure tends only to be 40-45% in the austenitic stainless family.

Cold working rapidly and dramatically increases the yield strength. Some forms of stainless steel, like spring tempered wire, can be cold to lift the yield strength to 80-95% of the tensile strength.

Ductility of Stainless Steel

The compounding of high work hardening ratios and high ductility\elongation makes stainless steel extremely easy to fabricate. With this characteristic compounding, stainless steel can be seriously deformed in processes like deep drawing.

Ductility is usually calculated as the % stretching before the break during tensile testing. Annealed austenitic stainless steels have extraordinarily high elongations. Usual figures are 60-70%.

The Hardness of Stainless Steel

Hardness is the penetration resistance of the substance surface. Hardness testers evaluate the depth that a hard indenter can be pressed into the surface of a material. Brinell, Vickers and Vickers machines are used. Each one of these has a various shaped indenter and technique of applying the familiar force. Transformations between the different scales are thus only approximate.

Precipitation and martensitic hardening types can be hardened by heat treatment. Other types can be hardened via cold working.

Tensile Strength of Stainless Steel

In general tensile strength is the only mechanical characteristic needed to define wire and bar and products. Similar substance types may be used at different tensile strengths for entirely different applications. The provided tensile strength of wire and bar products directly connects to the last use after fabrication.

Spring wire manages to have the top tensile strength after fabrication. The severe strength is offered by cold working into rolled up springs. The wire would not work correctly as a spring, without this intense strength.

These severe tensile strengths are not demanded wire to be used in weaving or forming processes. Bar or wire used as the raw substance for fasteners, such as screws and bolts, should be smooth enough for a thread or head to be shaped but still strong enough to carry out adequately in service.

The various families of stainless steel attend to have various yield and tensile strengths. These conventional strengths for annealed material are defined in the table.

Types Tensile Strenght Yield Strength
Austenitic 600 250
Duplex 700 450
Ferritic 500 280
Martensitic 650 350
Precipitation Hardening 1100 1000

Strength at High Temperatures

Stainless steel works somewhat better than other carbon steels at high temperatures. It expresses stronger fire resistance because of its high strength keeping element at high temperatures (over 500°C). It has a higher stiffness retention element than carbon steel over 300°C.

Cryogenic resistance

Some stainless steel types are highly adept at dealing with a more extensive range of temperatures. Austenitic steels raise tensile strength and exhibit exceptional toughness at sub-zero temperatures. This extends the scope of their usage, significantly opening up new paths for modern applications.

On the other hand, cryogenic temperatures are better than precipitation, martensitic, and ferrite hardening levels, as their toughness dips with falling temperatures.

Higher work hardening rate

This characteristic refers to a metal’s capacity to raise its strength while cold working processes. Stainless steels can be cold worked and annealed to maneuver its strength to the wanted level.

This implies that the same type can be used in many different applications by changing its strength. For instance, the same level may be used as a bendable or spring wire by cold working and annealing.

Electric conductivity and magnetism

Stainless steel conducts electricity, like all metals. Though, this conductivity is much low as in the instance of all steels.

In businesses where hygiene standards are elevated, or the electrical apparatus may be subjected to humid or corrosive environments, stainless steel enclosures are used for protection.

Austenitic stainless steels are non-magnetic; thus, cold working can generate magnetic characteristics in some types. All the other types of present magnetic properties.

Stainless Steel Chemical Properties

What makes this material unique and special is chemical properties, here are the Chemical properties of stainless steel.

High oxidation resistance

This distinguishing characteristic of stainless steel is accountable for its many unique applications in the industry. The severe resistance of oxidation is because of chromium in stainless steel. The ratio of chromium can rise to 26% in some types.

Other metals may be guarded with anti-corrosion and coatings paints, but the corrosion starts once it fades away. When it comes to stainless steel, any withdrawal of the natural covering of chromium oxide because of surface harm is followed by shaping a new coat on the visible surface that resists corrosion deterioration.

Biologically inert

Stainless steel is biologically inactive, making it the best choice for medical tools like trauma screws, plates, and surgical instruments. This characteristic also makes it a perfect metal for kitchen appliances and cutlery products.

Resistance to acids, bases, and organic materials

Stainless steel is resistant to a significant number of formulations. It is resistant to organic compounds, acids as well as bases. The resistance to acids differs for different types. Some types can resist highly focussed acids, whereas others may just be resistant to minimal concentrations.

Similar non-reactivity is discovered with organic compounds and basic compounds. This results in making stainless steel an ideal material for handling, storage, and other chemical processes.

Stainless steel also resists salt, moisture, sulphur, chloride compounds, and carbon dioxide with ease. This serves it to survive in many harsh atmospheres for a longer time than most other metals.

Other Properties (In addition to physical and chemical properties)

The essential characteristics are not just limited to chemical and mechanical only. There are others named below that come in practical for many applications.

Recyclability

As mentioned before, it is possible to recycle stainless steel for manufacturing new products. This lessens the strain on the atmosphere for our steel demands by lowering waste formation, as well as demanding fewer raw materials.

Its non-biodegradable characteristic also stops it from polluting resources. It does not seep and break down into water or soil reservoirs.

Easy to work with

Stainless steel is highly workable and machinable, permitting a designer to produce complex products and shapes. Stainless steel bending, CNC machining services, laser cutting, etc. are all accessible without any peculiar equipment.

Cleanability

It is easy to clean stainless steel products with non-toxic household goods such as cleaning liquids, detergent, or soaps. This helps to keep them looking new for an extended period raising the service life.

This ultimately lowers wastage and makes the initial quite expensive purchase deserve it in the long run.

Aesthetic appeal

The high luster in stainless steel products is making it a perfect choice for visible surfaces. It comes in a significant diversity of finishes from bright to matt. It may be engraved, brushed, tinted, and embossed for effect.

CHAPTER 4:

Stainless Steel: Composition Elements and Effect

Stainless Steel Composition Elements and Effect

Composition: Main Elements in Stainless Steel and Their Effect

Stainless steels consist of different alloying components that are in line with the specific grade and composition. The following parts outline the alloying creations and the reasons they exist, and a table to summarise each alloying element.

Carbon

Iron and carbon are put together to form steel. This process improves iron hardness and strength. Heat treatment is not sufficient to harden and strengthen pure iron. Still, a wide range of hardness and strength is accomplished when adding carbon.

A high carbon substance is not desirable in Austenitic and Ferritic stainless steels, particularly for welding purposes, because of the risk of carbide precipitation.

Manganese

Adding manganese to steel enhances hot working characteristics and boosts hardenability, toughness, and strength. 

The same as nickel, manganese is an Austenite forming component and has been commonly used as an alternative for nickel in the AISI200 series of Austenitic stainless steels, for instance, AISI 202 as an alternative for AISI 304.

Chromium

Chromium is united with steel to enhance its oxidation resistance. When more chromium is included, the resistance is enhanced further.

Stainless steels contain no less than 10.5% chromium (often 11 or 12%), which creates a massive corrosion resistance level compared to steels with a moderately lower chromium percentage.

The corrosion resistance is the formation of a self-repairing, passive layer of chromium oxide on the stainless steel surface.

Nickel

Vast amounts of nickel – almost more than 8% – are included in high chromium stainless steels to build a sufficient group of steels that are both heat and corrosion-resistant.

These contain the Austenitic stainless steel featured by 18-8 (304/1.4301). The tendency of nickel to create Austenite causes excellent toughness and high strength or impact strength high and low temperatures. Nickel also significantly enhances resistance to oxidation and corrosion.

Molybdenum

When mixed with nickel-chromium austenitic steels, molybdenum improves resistance to pitting corrosion and crevice, especially in chlorides-containing and sulfur environments.

Nitrogen

Same to nickel, nitrogen is an Austenite forming component and raises the Austenite constant of stainless steel. When nitrogen is blended with stainless steel, yield strength is significantly improved and increased resistance to pitting corrosion.

Copper

Copper is usually present as a residual component in stainless steel. This component is added to different alloys to produce precipitation hardening features or enhance corrosion resistance, predominantly in seawater and sulphuric acid conditions.

Titanium

Titanium is usually included to stabilize carbide, especially when the material should be welded. Titanium mixes with carbon to create titanium carbides that are somewhat stable and cannot be smoothly melted in steel, which is likely to diminish the phenomenon of intergranular corrosion.

When adding around 0.25 / 0.60% titanium, it merges the carbon with titanium as contrary to chromium, preventing a tie-up of corrosion-resistant chromium as intergranular carbides the related loss of corrosion resistance at the grain borders.

In the past different years, titanium has diminished because of steelmakers’ capacity to provide stainless steel with deficient carbon substances. Such steels can be readily welded with no need for stabilization.

Phosphorus

Phosphorus is usually added with sulfur to enhance machinability. While phosphorus in Austenitic stainless steel raises strength, it harms corrosion resistance. It extends the material’s propensity to break during welding.

Sulfur

Adding it in small quantities, sulfur enhances machinability, but just like phosphorus, it has a detrimental effect on the subsequent weldability and corrosion resistance.

Selenium

Selenium was formerly used as an addition to increase machinability.

Niobium/Colombium

Carbon stabilization is accomplished by adding niobium to steel and acts in the same role as titanium. Moreover, niobium strengthens steels and alloys for enhanced temperature service.

Silicon

Silicon is typically used as a deoxidizing (killing) element in the steel melting procedure. A small quantity of silicon is employed in most steels.

Cobalt

When exposed to strong nuclear reactors’ radiation, cobalt turns highly radioactive. Therefore, all stainless steels assigned in nuclear service will have specific cobalt limitations, usually 0.2% at the most.

This issue is significant as some left cobalt amount will be presented in the nickel used to create Austenitic stainless steel.

Calcium

Calcium is added in small quantities to improve machinability without adverse effects on other characteristics induced by sulfur, selenium, and phosphorus.

Summary Table

The following table explains the effect of alloying components on the characteristics of stainless steel.

Property C Cr Ni S Mn Si P Cu Mo Se Ti or Nb
Corrosion Resistance - X - - - - -
Mechanical Properties - - -
High-Temperature Resistance - X - - - - -
Machinability X X - - - - - -
Weldability X X - X - X - -
Cold Workability X X X - - - - - -

Key: √ = Beneficial; X = Detrimental

CHAPTER 5:

Stainless Steel: Characteristics And Advantages

Stainless Steel Characteristics And Advantages

Stainless Steel Characteristics

Stainless steel is characterized by many desirable features that help vastly to its broad application in the manufacturing of components and parts through many industrial fields. Most importantly, because it contains chromium, it’s resistant to corrosion. The 10.5% minimum content makes the steel resistant to corrosion roughly 200 times more than those without chromium. Other desirable features for customers are its high durability and strength, low and high-temperature resistance, easy fabrication and increased formability, long-lasting, low maintenance, attractive appearance, recyclable, and environmentally friendly. As soon as stainless steel is placed into duty, it doesn’t need to be coated, treated, or painted; there are stainless steel characteristics in points.

Top 12 Benefits When Using Stainless Steel

Using stainless steel in many applications has many benefits; some are related to corrosion resistance. Others are related to strength, ease of fabrication, Etc. Here are the benefits of using stainless steel.

Excellent oxidation resistance

Let’s start with the most apparent advantage of stainless steel: it’s resistant to corrosion\rust. Chromium is the alloying item that offers Stainless Steel its corrosion-resistant characteristics.

Lower alloyed types resist corrosion in pure and atmospheric water atmospheres; high-alloyed types that can avoid corrosion in most acid are stainless steel’s, chlorine-bearing environments, and alkaline solutions, making their characteristics useful in process plants.

Whether you plan to use it outdoors or indoors, the corrosion-resistant properties of stainless steel are sure to prove useful. Moisture is everywhere around us in the shape of humidity; this humidity can cause rusting and tarnishing in different kinds of metals, but not stainless steel.

Fire and Heat Resistance

The special high nickel and chromium-alloyed types avoid scaling and maintain high durability at high temperatures. Stainless Steel is used vastly in heat boilers, mainstream lines, exchangers, feedwater heaters, valves, superheaters, and aerospace and aircraft applications.

Hygiene

cleaning stainless steel

Another advantage of stainless steel is its soften of cleaning. There are many cleaning items created, particularly for stainless steel, making cleaning easy. And because of its corrosion resistance by nature, you don’t have to concern about the harmful effects of humidity left behind. Just get your favorite product and wipe down the surface to clean and get its shiny look back.

The effortless cleaning power of stainless results makes it the first option for strict hygiene conditions, like, kitchens, hospitals, and food processing plants.

Aesthetic Appearance

The bright surface of stainless steel offers an attractive and modern appearance.

Strength-to-Weight Benefit

The work-hardening feature of austenitic types that results in a vast strengthening of the substance from cold-working alone, and the sharp strength duplex levels, allow decreased material thickness over traditional styles yielding substantial cost savings.

Ease of Fabrication

Fresh steel-making methods mean that stainless can be bent, cut, welded, machined, formed, fabricated, and assembled as quickly as traditional steels.

Impact Resistance

The austenitic micropattern of the 300 series offers high strength at below-freezing temperatures, making these steels especially suited to cryogenic applications.

Long-Term Value

When considering total cost, it is good to assess production and material cost AND the life cycle expenses. When the entire life cycle expenses are considered, stainless is usually the least expensive material choice—the cost-saving advantage of a preservation free product having a long life expectancy.

100 % Recyclable

Over 50% of fresh stainless comes from old redesigned stainless steel trash, therefore completing the full life cycle.

A wide selection of Finishes

Stainless steel is available in different finishes, providing an even broader level of adaptation for your project. Once the steel is formed to the required shape, thickness, and size, a mill finishing can be implemented to make it more visually attractive. Some of the various mill finishes include No. 0, No. 1, No.2D, No. 2B, No. 2BA, No. 3, No. 4, No. 5, No. 6, No. 7, No. 8, No. 9, and No. 10.

Self-Healing

No, this isn’t a typing error. Stainless steel can heal itself. The chromium existence inside this metal enables creating a small layer of chromium oxide roll over the surface. If stainless steel is harmed and exposed to oxygen, the chromium oxide layer will begin to repair it. This doesn’t certainly mean that the significant damage will, by some miracle, go away. Still, little surface scrapes will probably heal because of the film of chromium oxide.

Durability

Stainless steel is solid. Even thin stainless steel won’t warp under high weight to make it the most sustainable metals on the market. It can resist weight, cold and hot temperatures, and weather extremes.

CHAPTER 6:

How Stainless Steel is Made?

How Stainless Steel is Made

How stainless steel is made?

The right process of stainless steel grade will vary in the next stages. How the type of steel is formed, worked with, and finished plays an essential role in determining its shape and performance.

Before you can build a deliverable steel product, you must first make a melted alloy.

Due to this, most steel types share known initiation steps.

Step 1: Melting

Stainless steel manufacturing begins with the smelting of scrap metals and additions in an Electric Arc Furnace (EAF). Using high-powered electrodes, an electric arc furnace heats metals over a period of several hours to form a molten, liquid mixture.

Stainless steel is 100% recyclable; many stainless steel orders hold up to 60% recycled steel. This not only helps control costs but reduces the environmental impact.

The exact temperatures will change according to the type of steel being constructed.

Step 2: Removing Carbon Content

Carbon helps increase iron’s hardness and strength. However, too much carbon can cause problems – such as carbide precipitation while welding.

Before molding molten stainless steel, it is necessary to calibrate and reduce the carbon content appropriately.

There are two methods foundries control the content of carbon.

The first is via Argon Oxygen Decarburization (AOD). Injection of the argon gas mixture into the molten steel lessens the carbon content with the least loss of other essential elements.

The second used method is vacuum oxygenation (VOD). In this way, the molten steel is forwarded to another hall, injecting Oxygen into the steel while heat is valid. The vacuum then erases vented gases from the chamber, which further reduces the carbon content.

Both methods provide precise control of carbon content to assure proper mixture and fine properties in stainless steel’s final product.

Step 3: Tuning

After carbon reduction, the final equilibrium and homogeneity of chemistry and temperature occur. This assures that the metal meets the intended grade requirements and that the steel composition is coherent throughout the batch.

Samples are tested and evaluated. Then adaptations are made until the combination meets the needed standard.

Step 4: Forming or Casting

With the formation of the molten steel, the forge must now create the primitive form used to cool and run the steel. The exact dimensions and shape rely on the final product.

Common forms include:

  • Rods
  • Blooms
  • Slabs
  • Billets
  • Tubes

The forms are then marked with an ID to trail the batch through the different processes that must be followed.

From here, the stages will vary according to the intended degree and the final product or job. Panels become sheets, strips, and plates. Billets and Blooms become wires and bars.

Depending on the desired grade or shape, the steel may go through some of these stages multiple times to make the desired look or properties.

The following stages are the most used.

Hot rolling

This step is performed at higher temperatures than the steel’s recrystallization temperature. This level helps to adjust the coarse physical dimensions of the steel. Precise temperature control during the process keeps the steel smooth enough to work without changing the structure.

The process uses constant passes to adjust the dimensions of the steel slowly. In most instances, this will include rolling through multiple grinders overtime to get the desired thickness.

Cold rolling

Usually used when precision is needed, cold rolling exists below the steel recrystallization temperature. Multiple backed rollers are used to form steel. This process creates a more uniform and attractive finish.

Nevertheless, it can also deform the steel structure and often needs heat treatment to recrystallize the steel to its initial microstructure.

Annealing

After rolling, most of the steels undergo an annealing procedure. This includes cooling cycles and controlled heating. These cycles soften the steel and ease internal stress.

Exact times and temperatures will depend on the type of steel, cooling, and heating rates affecting the final product.

Descaling or Pickling

Since steel is made through different steps, it often piles up on the surface.

This buildup is not merely unattractive. It can also affect the stain resistance, weldability, and durability of the steel. Erasing this scale is essential to generating the oxide barrier that provides stainless steel with its stain resistance and characteristic corrosion.

Picking or descaling erases this scale by either controlling cooling and heating in an oxygen-free environment or using acid baths (recognized as acid pickling).

Depending on the final product, the metal may return to extrusion or roll for further handling. Constant annealing phases follow this until the desired properties are achieved.

Cutting

Once the steel is ready and working, the batch is cut to suit the order’s demands.

The most known methods are mechanical, like cutting with circular knives, guillotine knives, die punching, or high-speed blades.

Yet, for complex shapes, plasma jet cutting or flame cutting may be used as well.

The best choice will depend on the steel required grade and the wanted shape of the provided product.

Finishing

Stainless steel is accessible in a diversity of finishes from flat to mirror. Finishing is one of the final steps implicated in the production process. Usual techniques contain acid or sandblasting, sandblasting, belt grinding, belt polishing, and belt polishing.

At this stage, the steel is collected in its final form and ready for shipment to the customer. Coils and rollers and coils are standard methods of storing and shipping large stainless steel quantities for other producing processes. Nevertheless, the final shape will depend on the required type of steel and other factors specific to the demand.

CHAPTER 7:

Stainless Steel: Common Applications

Stainless Steel Common Applications

Applications of Stainless Steel

With its adorable properties, stainless steel products almost cover all walks of life, including furniture, kitchen supplies, electrical appliances, equipment, electronic products, construction parts, medical parts, aviation parts, automobile parts, bicycles, sports equipment, etc. Let’s see some.

  • Retractor springs
  • Rapid transit buses, cars, cargo containers, and aircraft
  • Hose clamps
  • Bottling machinery
  • Conveyors
  • Still tubes
  • Jewelry
  • Expand metal parts
  • Cryogenic components and vessels
  • Dryers
  • Mixing bowls
  • Papermill equipment
  • Furnace parts
  • Oil refining equipment
  • Heat exchangers
  • Dyeing equipment
  • Textile industry
  • Jet engine parts
  • Recuperators
  • Dairy industry
  • Fasteners
  • Pipes, tubes
  • Welded storage tanks, used for organic chemicals
  • Emission and burner control components
  • Combustion chambers
  • Skewers
  • Furnace arch support
  • Bank vaults
  • Kiln linings
  • Glass molds
  • Smoke control ductwork
  • Fish hooks
  • Coal chutes
  • Cutlery
  • Gauge parts

Almost every day you can see many kinds of stainless steel products, stainless steel is omnipresent.

CHAPTER 8:

How to Select Stainless Steel?

How to Select Stainless Steel

How to Select Stainless Steel?

The most common question is How to know what grade I have to choose. Here is the

answer. the answer depends on many questions

Despite stainless steel is widely used in different industries, thanks to its strength, hygiene, and high corrosion resistance with more than 150 grades available, it becomes complicated to choose the right type while selecting.

Due to the fact that stainless steel is an excellent metal that provides a diversity of alloys, choosing the right type can go a long way to ensuring that your work gets done smoothly. There are many factors that you can consider when selecting a stainless steel grade.

The amount and type of corrosion resistance desired

Generally, stainless steel is selected for its corrosion-resistant characteristics. But you need to take into account the type and amount of corrosion resistance required. Different varieties come in various quantities of wear resistance.

For example, Austenitic stainless steel can provide you with maximum corrosion resistance due to large chromium amounts. Hence, you can choose grade 304 when wear resistance is vital. Grade 304 and Grade 316 are comparable, but because Grade 316 contains molybdenum as part of its chemical formula, its corrosion resistance is more.

If you are searching for a more economical grade, you can settle for martensitic and ferritic stainless steels. However, its corrosion resistance is low due to less nickel and occasionally less chromium.

To resist stress corrosion cracking of Austenitic stainless, you can choose double-sided stainless steel.

Consider your operating environment

You will have to think about your working atmosphere before investment in a stainless steel grade. Take into consideration the environment in which you will apply your final product. While it is acceptable to use stainless steel to manufacture a door frame in your office or home, ordinary stainless steel cannot withstand too high temperatures, low pH,  crevice corrosion, and high stresses.

Go for stainless steels in the austenitic T3XX series, such as 316 and 304 alloys

It can retain its toughness, corrosion resistance, and strength properties over a wide range of temperatures. Type 316 can resist chloride ions that you get in chemical and marine processing applications.

Point out that you cannot weld all grades of stainless steel types. Stainless steels subject to stress corrosion cracking and hot cracking cannot be used for welding. For example, martensitic stainless steel has a high carbon content, making any kind of change difficult. Hence, this type of stainless steel is terrible for welding.

You can choose grades like 304 or 304L as they come with less carbon than other stainless steel grades. In general, Austenitic stainless steel types are best for forming and welding, although stress cracking can exist.

A little ferrite is recommended to save the material from cracking. This is the precise reason why duplex steels have outstanding formability and weldability characteristics. As long as you select the right grade, like Grade 407 and 430, Ferritic stainless steels can also be welded. But bear in mind the fact that many grades of ferritic steel are low for welding due to the hardness of HAZ (heat affected zone). It can crack in the incorrect temperature range.

Give importance to mechanical qualities

Toughness, strength, and ductility are the three most critical mechanical qualities to be given importance. Stainless steel attaches to 10-30% of chromium as the alloying component. It is this component that makes it resist corrosion.

In Austenitic grades, nickel’s presence enhances the highest ductility and toughness among different properties display stainless steel grades. The most corrosion-resistant grades of stainless steels are those rich in molybdenum, chromium, and nickel.

Furthermore, make sure not to nickel’s focus solely on the alloy content when selecting a stainless steel grade. The way the material is treated will also impact its mechanical response.

The time in which the steel is held at various temperatures as a portion of the cooling process and the overall speed at which it is cooled will impact its overall quality. It is real that heat treatment can enhance the carbon steels’ hardness. Still, austenitic stainless steels are hardened by cold processes, including rolling, bending, drawing, or swaging at temperatures less than the temperature recrystallization.

Note that when cold processes improve hardness, it will reduce other characteristics such as impact resistance and elongation.

Consider the magnetic response

You will find various families of stainless steel with different physical characteristics. The magnetic characteristics of stainless steel are resolute by the components added to the alloy.

Primary stainless steel exhibits a “ferritic” structure that is magnetic due to the addition of chromium. By adding carbon, you can harden it, thus making it a “martensite.”

In contrast, the most widespread stainless steels are Austenitic because they occur with higher chromium content. You will also meet nickel, which changes the steel’s physical structure to make it non-magnetic.

Austenitic degrees have “relative magnetic permeability” or less magnetic interaction. Grades of stainless steel rich in nickel content such as 310 or 316 grades are non-magnetic in any condition.

Hence, you can use it in applications where you need a metal that is not magnetic. If you are research stainless steel grades with high magnetic response, choose the martensitic and ferritic stainless steel grades (400 series). It is classified as “ferromagnetic” and comes with high permeability. Also, keep in mind dual degrees like 2205 and  2101 when looking for magnetic grades of stainless steel.

Filtering Since there are many stainless steel grades to select from, you must decide which stainless steel type you need based on its application with different properties displayed. Going to the right class of stainless steel will help you complete your project smoothly while also saving money.

CHAPTER 9:

Frequently Asked Questions

In this chapter, we have prepared some common questions and answers about stainless steel, so that you can understand stainless steel more clearly.

Frequently Asked Questions​ of Stainless steel

F.A.Q

Stainless steel can not rust, as you think of ordinary steel rust on the surface with a red oxide that flakes off. In general, corrosion often happens because of the contaminants settling on stainless steel surfaces.

Although stainless steel is more resistant to corrosion than alloy or ordinary carbon steels, it can corrode in some cases. It is "stain-less" and not "impossible to stain.” In everyday water-based or atmospheric environments, stainless steel will not rust, as evidenced by cutlery, domestic sink units, work-surfaces, and saucepans.

Plain stainless steels may be corroded in more energetic conditions, and high-alloy stainless steels may be used.

The most known forms of corrosion in stainless steel are:

  • Corrosion pitting - Particular chemical species can assault the inactive layer on stainless steel. The chloride ion Cl- is the most known and exists in everyday items such as bleach and salt. Corrosion pitting is avoided by ensuring that the stainless steel is not in contact for a prolonged period with harmful chemicals or by choosing a steel grade that is more attack resistant. The corrosion pitting resistance can be assessed using the equivalent number of pitting resistance calculated from the alloy content.
  • Crack corrosion - stainless steel needs an oxygen supply to ensure an inactive layer can shape on the surface. In very narrow cracks, oxygen is not always possible to reach stainless steel’s surface, making it vulnerable to attack. The cracks’ abrasion is avoided by sealing the cracks with a flexible sealant or using an abrasion-resistant grade.
  • General Corrosion - Usually, stainless steel does not corrode uniformly like ordinary carbon and alloy steel. With some chemicals, particularly acids, the inactive layer can be attacked uniformly based on the temperature and concentration. The metal loss is scattered over the entire steel surface. Sulphuric acid and hydrochloric acid at some attention are particularly aggressive towards stainless steel.
  • Stress Corrosion Cracking (SCC) - This is a somewhat unique corrosion form that demands a concrete mixture of tensile stress, corrosive species, and temperature, often a chloride ion, to occur. Standard applications where SCCs can occur are swimming pools and hot water tanks. Another pattern known as sulfide stress corrosion cracking (SSCC) is hydrogen sulfide in gas and oil exploration and production.
  • Intergranular corrosion - This is now a short corrosion form. If the carbon level is too high in the steel, chromium can merge with carbon to form chromium carbide. This happens in temperatures between about 450-850 ° C. This operation is also called sensitization and usually occurs during welding. The chromium existing to form the inactive layer is effectively decreased, and corrosion can exist. It is avoided by selecting a low carbon grade, so-called "L’ grades, or using steel with niobium or titanium, which preferentially binds to carbon.
  • Galvanic Corrosion - If two different metals come in contact with each other and with an electrolyte, e.g., water or another solution, it is possible to create a galvanic cell. This is somewhat similar to a battery and can accelerate the wear of less "noble" metal. It can be avoided by separating the metals with a non-metallic insulator like rubber.

There are various "types" of stainless steel. Series 300 (which includes nickel) is NOT magnetic. Series 400 (which contains only chromium and does not contain nickel) ARE magnetic.

Stainless steel is somewhat a good conductor of electricity, just like all metals.

Stainless steel is enabled to be welded with stick welding, gas tungsten arc welding (TIG), and shielded metal arc welding (MIG). Each of these procedures will yield a little different result.

Steel is the most recycled material on Earth. ... When stainless steel is melted down and recycled, these precious alloys can be reused and extracted with no deterioration in performance from one product to another. Indeed, the vast most of stainless steel is produced using formerly recycled materials.

Austenitic stainless steels are widely used for service, even as low as liquid helium (-269 ° C). Steels with martensitic or ferritic structures exhibit a sudden transformation from a ductile (safe) fracture to a brittle (unsafe) fracture over a slight temperature difference.

With at least 18% chromium content, most Austenitic steels can be used at up to 870 ° C temperatures and grades 310, 309, and 2111 HTR (UNS S30815). Most ferritic and martensitic steels have less oxidation resistance and thus lower useful temperatures operating.

There are various types of surface stainless steel finishes. Some of these create from the mill, but many are applicable later. Simultaneously, processing, for instance, brushed, polished, etched, blasted, and colored finishes.

Grades such as 347 or 304L must be used, When welding austenitic stainless steel. Grade 304L is low in carbon, while niobium stabilizers are added to347 which helps prevent intergranular corrosion. Ferritic stainless steel like grade 439 or 430 is easily weldable, like double-sided stainless steel.

Summary

Stainless steel brings along heat and corrosion resistance besides the conventional characteristics of steel. It offers all the benefits of steel along with a little of its own. It does not corrode readily, has a longer service life, and endures rough atmospheres better.

But it is not entirely true that it is stain resistant. First, the wear resistance depends on the type. Yet, abnormal ambient conditions such as poor circulation, high salinity, and low oxygen may stain it irreversibly.

These data are indicative only and should not be considered a substitute for the full specifications drawn from them. In particular, requirements for mechanical properties vary widely with product, temper, and product dimensions. The information is based on our current knowledge and is provided in good faith.

If you like this guide, please share it with your friends, thanks in advance.

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