Today we are taking a deep dive into stainless steel and how it is made. This type of steel is widely used. Chances are you own at least a few appliances that are made of stainless. I know my refrigerator is.

Stainless steel comes in many different types. At Norfolk Iron we supply two main types of stainless-Austenitic and Ferritic.

Austenitic is the most common of the stainless steel types. This includes the 200 and 300 series. The alloy contains a minimum of 16% chromium and is also composed of a significant amount of nickel and manganese (here is a link to a some periodic tables in the off chance you don’t know what I am talking about).

Austenitic stainless has excellent corrosion resistance, good ductility, non-magnetic properties, strength and weldability.

The most common type of austenitic stainless is type 304 due to its corrosion resistance to a wide range of industry exposures. This makes it ideal for foodservice equipment or any application where sanitation is required.

Ferritic alloys have lower corrosion resistance than austenitic alloys due to lower chromium (10.5-27%) content. This includes some of the 400 series of stainless, including 409 and 430. Ferritic stainless has good corrosion resistance, high strength and great workability.

How Stainless Steel is Made

Mining

The process of making stainless steel begins with extracting chromite (an iron chromium oxide) from underground mines. It is then crushed to produce a chromite concentrate. This is what makes stainless steel strong and corrosion resistant.

You wouldn’t want a stainless steel refrigerator that doesn’t hold up and corrodes, right? The product’s ability to hold up is the basically the point of buying stainless-aside from the appealing surface finish, of course.

Melting

The next step is to melt the chromium pellets together in an electric furnace with the other raw materials (iron ore, manganese, nickel, etc.) used for the specific stainless type. After melting, the material is formed into slabs and transferred to a hot rolling mill.

Hot Rolling

Once the slab arrives at the hot rolling mill it is transferred to another furnace and the hot material is then sent through a roughing mill. At the roughing mill it is rolled forwards and backwards to reduce the thickness. As the thickness is decreased it causes the slab to become a long strip that will later be wound up into a coil.

The long strip, or band, is passed through additional rolling mills to reduce the thickness even more. At this point it is coiled then cooled by water and transferred to a cold rolling mill.

Cold Rolling

When the material arrives from the hot rolling mill it is covered in a black scale.

At the cold rolling plant the material is uncoiled and passed through an annealing and pickling line to remove the black scale. The band is then reduced to the thickness specified by the customer and recoiled.

The coiled material is sent through another annealing and pickling process and rinsed with water.

Finishing

Well, the stainless steel material goes through one final finishing step of removing the tension and improving the overall surface finish. The finished stainless is cut to the specified dimensions and shipped to customers around the world via train or barge.

When we receive the material we process it further to ensure our customers are getting the product they need. For more information about our stainless steel product offering, contact your local sales person.

How Aluminum is Made

Aluminum is used for a variety of applications from soda cans to airplanes, signs to automobiles. What you may not know is that these everyday items basically started with dirt.

Mining

The type of dirt I am talking about is bauxite ore. Bauxite is rich in aluminum oxide. This dirt, or bauxite ore, is loaded into trucks and taken to a plant for refining. Essentially a truckload of bauxite ore can be refined into two tons of aluminum.

Refining

The next step is to turn the bauxite ore into alumina (the primary ingredient for making aluminum). This is done by grinding the ore and mixing it with caustic soda (sodium hydroxide).

The mixture, now known as slurry, is pumped into a high-pressure container and heated to approximately 230-520 degrees Fahrenheit. The aluminum oxide is dissolved by the caustic soda and precipitated out of the solution, meaning it is separated from the mixture. It is then washed and heated to get rid of the water.

This leaves us with a white powder called alumina. There are many other uses for alumina, but today our focus is on turning it into sheet metal.

Smelting

The process of turning alumina to aluminum includes an electrolytic reduction, or smelting. Alumina is dissolved in a cryolite bath inside large pots lined with carbon.

Aluminum metal separates from the chemical solution after an electrical current is passed through the bath. It is then separated out.

Fabricating

After smelting, the aluminum goes into a furnace for further mixing to form the various alloys. The metal goes through a purification process and is then poured into molds or cast into ingots.

From here, the aluminum will either undergo further fabricating, including casting, rolling, extruding, etc., or it will be sent directly to customers.

Aluminum has many desirable qualities. It is lightweight yet strong, and nonmagnetic and nontoxic. It conducts heat and electricity; it also reflects heat and electricity. The metal is easily workable and can retain strength under extreme cold, ideal for trailers. It is also one of the most easily recyclable materials, especially when it comes to metal.

What is Aluminum Used For?

Aluminum is used in many end markets. Some of the markets we provide aluminum products to include truck & trailers, commercial lighting, roofing & siding, heat exchangers, outdoor furniture, framework, and much more.

For more information on how we can help with your aluminum needs, contact your local sales representative. You can also view our full Product Guide here.