Stainless Steel Metal

Introduction:

Consider how often we use items made of stainless steel. From household tableware to the pipe works of our housing to saving lives and transporting goods, Stainless steel significantly impacts on our everyday lives.

This blog will cover the following topics.

• What is Stainless steel?
• The history of Stainless steel
• How Stainless steel is made
• The different types of Stainless steel
• What Stainless steel is used for
• And much more …

What is Stainless Steel?

Stainless steels is an iron alloy that contains a minimum of 10.5% Chromium and a maximum of 1.2% Carbon. Chromium produces a thin “passive layer” of oxide on the surface of the steel. This creates the formation of a protective layer and prevents any further corrosion to the surface. The passive layer self-repairs when chromium reacts with oxygen and moisture in the environment to reform the oxide layer. Increasing the amount of Chromium in stainless steel will result in greater corrosion resistance.

Stainless steel is a durable, strong, heat resistant long term solution for long life applications. Stainless steel material is becoming more and more popular due to the increased need of long-lasting and sustainable solutions to global critical challenges. In today’s world it is vital we reduce our carbon footprint and become more environmentally friendly. Stainless steel has increased in demand due to economic, social and environmentally sustainability solutions.

The history of Stainless Steel

Sheffield metallurgist Harry Brearley discovered stainless steel in 1913 when  testing different types of steel for weapons. He discovered Stainless steel when he used a 13% Chromium steel that didn’t corrode after a number of months. However there are a number of claims to being the “inventor” of stainless steel; from countries such as Britain, Germany, France, Poland, the U.S.A and Sweden.

The exceptional properties of Stainless steel were gradually discovered over several decades.

1919-1923: Stainless steel was manufactured to make surgical scalpels, tools and cutlery.

1925: Stainless steel tanks were used to store nitric acid.

1928: Hygienic feature was discovered and to this day Stainless steel is used in the pharmaceutical, Bio tech medical and the food processing industry.

1930: First ever stainless steel train.

2010: Global production of stainless steel, 11 billion stainless steel washing machine drums were manufactured in China.

Today, stainless steel is the leading choice material for many applications because it is an economical, social, environmentally friendly solution.

How Stainless steel is made?

Stainless steel is a circular economy as it is 100% recyclable. It is made up with a variety of basic chemical elements, to name just a few; nickel, chromium, iron ore, silicon and molybdenum. Once all the chemical elements are gathered they are then melted together to create a strong sustainable alloy.

Stage 1: The melt shop

The scrap raw material is converted into molten metal when transferred into an electric arc furnace with a melting capacity of up to 160 tones. The molten metal is then transferred by a ladle to the converter. At this stage the alloy elements are added to obtain the exact chemical composition and the correct temperature before the casting process continues. The continued casting process cools and solidifies the liquid steel. The solid steel is then cut into manageable slabs of up to 30 tones in weight, up to 12 m long, 200m thick and up to 2 m wide.

Stage 2: hot rolling mill

The slabs are then brought to the Aperam Chatelet where they are reheated at 1250 degrees. This process reduces the thickness of the slabs from 200mm to 40mm. They are then reduced in thickness even further to 3mm when passed through a series of 7 rolling stands. The metal is then cooled and wound to create “black coils”.

Stage 3: First annealing and pickling

The annealing furnace heats the black coil, while the oxide on the surface is broken down by shot blasting. The pickling process, followed by water cleaning and air drying forms white coils known as the HSAP finish.

Stage 4: cold rolling and final annealing

The cold rolling mill process reduces thickness to a minimum of 0.3mm, while the final annealing tailors the product to meet customer’s exact specifications.

Stage 5: Metal finishing

At the final stage, the product is slit and cut to its required width and length. Meanwhile polishing, brushing and other surface finishes can be made. Below is an image of perf before and after electropolishing.

Stainless Steel materials types

There are 4 different types of stainless steel, ferritic, austenitic, martensitic, and duplex.

Ferritic:

These steels contain mainly chromium and a small amounts of carbon. Ferritic steels are used for white goods such as washing machine goods, filters, catering – 340 grade automotive exhaust, and catalytic. When the steel grade starts with 4 it is usually ferritic.

Austenitic:

Austenitic steel is used for Architectural projects although it is predominantly used for the water and waste industry. If the steel grade starts with 3 it is Austenitic.

Duplex:

Duplex steel is best used for marine environments and chemical processing as it is semi magnetic.

Martensitic:

This steel type is most commonly used for medical tools and surgical instruments. Martensitic and Ferritic are related in some way.

What is Stainless steel used for?

Stainless steel is used for a wide range of products in a variety of industries. The main industries include, pharmaceutical industry, food processing industry and architectural and construction industry.

Products made from stainless steel within the different industries

Food contact:

Stainless steel is used for food contact. Products made from stainless steel in this industry include, kitchenware, food tables and much more.

Medical devices:

In most cases Stainless steel is the only material used for medical devices and implants as it is considered a safe material.

Drinking water:

Stainless steel is listed as a “Metallic material suitable for drinking water under hygiene aspects”. As the steel reaches hygienic expectations.

Graepels stainless steel products within the different industries

Pharmaceutical Industry:

Graepels have over 60 years of industry expertise in manufacturing high quality stainless steel products with capabilities for the pharmaceutical industry. Stainless steel is a highly stable material hence why it is used in the pharmaceutical industry. Stainless 304, 304L, Stainless 316 and 316L grades are non-reactive.

Pharmaceutical stainless steel products,

• Stainless steel table:

  Easily cleaned and protected from contamination. A good choice of material for industries where hygiene is paramount.

• Perforated pharmaceutical tube holder:

  High chemical resistant to hostile compounds.

• Auto clave (steam sterilizer):

  Heat resistant.

Food Processing Industry:

Graepels manufacture Stainless steel products to the food processing industry since 1959. Stainless steel obtains many useful qualities needed in the food processing industry, making it the top material choice.

• Malting process screens:

  Stainless steel offers good thermal capabilities, making it easier for cleaning screens to remove unwanted materials from agricultural crops.

• Malting, perforated sheet:

  Stainless steel is a self-protecting material and has the capabilities to last in high temperature environments.

• Perforated drain on bar:

  Sustainable choice as fabrication and maintenance is substantially low.

Architectural & Construction Industry:

When choosing outdoor applications from balustrade infills to public art sculptures, Stainless steel offers many significant advantages over other materials. It is highly durable and has great rigidity. Meanwhile it is corrosion resistant and will last in tough conditions where corrosion is likely to occur.

• Balustrade infill panels:

  Stainless steel perforated and woven balustrade infill panels are ideal for outdoor areas, they are low maintenance, aesthetically pleasing and will stand the test of time.

• Stainless steel perforated sheets:

  Stainless steel can be easily perforated into a verity of hole sizes and shapes, fabricated, folded and machined to customer specification creating aesthetically pleasing public art sculptures, signage and much more. Graepels manufactured a perforated metal landmark for Dublin’s newly refurbished Diving Bell at the Dublin Docklands. Graepels opted to use Stainless steel on this project primarily because of its long lifespan while keeping mindful of all the other outstanding properties that come with Stainless steel material.

Stainless steel woven wire:

Stainless steel is easily weaved into a range of patterns for a variety of industrial and architectural applications, including stainless steel woven wire balustrade infills panels, quarry screens, cladding, facades, fencing, balconies, filters, fly and vermin meshes and much more. Graepels manufactured a stainless steel wire mesh balustrade infill panel for the Booterstown Dart Station. The location was considered when choosing stainless steel as the high salt content in the water would be likely to erode metal and therefore a high strength steel such as stainless steel was required.

• Stainless steel can also be used in architectural, Building and construction industries as; cladding, sun shades, decorative screens, stairs, flooring, bridges, ventilation panels, filters, drainage and water systems.

Advantages of Stainless steel

Long lasting sustainable solution!

Corrosion resistant:

Stainless steel is the perfect material choice where corrosion is likely to occur. The material self-repairs, keeping the surface appearance clean and new, it is guaranteed to last several decades, standing the test of time! Many customers choose stainless steel for outside balustrade infills panels where the environment and location of the application is considered.

High quality material:

Stainless steel is a premium metal that is highly durable and strong, higher strength again can be obtained from martensitic, duplex and austenitic steels.

Non-reactive, heat resistant:

Stainless 304, 304L, Stainless 316 and 316L grades are non-reactive, making them a safe choice. The steel is resistant to hostile chemical compounds and the protection from contamination. It is also heat resistant and can withstand elevated pressures and temperatures.

Environmentally friendly:

As mentioned previously, stainless steel has a long life span however like most things stainless steel comes to an end. Did you know Stainless steel is 100% recyclable? Making it extremely environmentally friendly, a great choice of metal to reduce our carbon footprint.

No need for painting:

Stainless steel is corrosion resistant, it is a self-protecting, self-repairing material. Stainless steel needs oxygen to carry out these properties and therefore painting Stainless steel is not required. In conclusion, stainless steel is a convenient low maintenance material that remains aseptically pleasing for decades.

Some of our favorite jobs around the word

• Empire state building:

  Stainless steel is the main component in many famous buildings like the Empire State building . It has only ever been cleaned twice in its lifetime and still looks fantastic. This is a testimony to the longevity of stainless steel.

• UK stainless steel Pooley Bridge:

The Stainless Steel Pooley Bridge replaced the 250 year old stone bridge previously located there. Stainless steel was chosen with the location and environment surroundings considered.                  For more information click here https://www.ice.org.uk/eventarchive/pooley-bridge-replacement-bridge-project-webinar

• Kelpies Horse Head:

  The Kelpies in Falkirk, the two 30-metre-high horse heads were laser cut and manufactured in stainless steel. This sculpture has transformed the area into a five-star tourist destinations.

References

• https://bssa.org.uk/bssa_articles/the-discovery-of-stainless-steel/
• https://www.azom.com/article.aspx?ArticleID=8307#:~:text=In%201913%2C%20Harry%20Brearley%20of,metal%20that%20did%20not%20rust.
• https://www.marlinwire.com/blog/how-is-stainless-steel-made#:~:text=Stainless%20steel%20metal%20is%20formed,together%2C%20create%20a%20powerful%20alloy.
• https://www.aperam.com/sites/default/files/documents/Manufacturing%20Process%20Gobal_en.pdf
• https://www.ice.org.uk/eventarchive/pooley-bridge-replacement-bridge-project-webinar
• www.ouokumpu.com