Weathering Steel: What is it?

Weathering steel, commonly referred to as A606 steel, has recently gained popularity in the architectural world for its distinctive orange-brown oxide (or rust) finish. This layer of rust aids in the resistance to corrosive elements. When weathering steel is produced, it is not rusted. It gradually develops the rust-like appearance as it is exposed to the elements over time.

But, how does it develop the layer of rust and how does that actually aid in corrosion resistance? Let’s find out!

How Weathering Steel Works

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Unlike most corrosion resistant steels that resist rust, weathering steel does rust. However, it only rusts on the outer layer and will not penetrate into the steel once the initial layer has formed. With weathering steel, the layer of rust acts as a barrier to protect the steel from corrosion, whereas with other metals the rust is porous and breaks off allowing another layer to form. The specific alloying elements in the steel produce a stable layer of rust that adheres to the base metal and isn’t as porous as typical rust.

Benefits of Weathering Steel

Weathering steel has many benefits, which make it ideal for architecture.

  • Resists further rusting and staining
  • A high strength low alloy steel (HSLA)
  • Heat and corrosion resistant
  • Ease of formability
  • Low maintenance
  • Long-term performance
  • Environmentally friendly and can be recycled

What is Weathering Steel Used For?

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Because it is corrosion resistant, weathering style is frequently used for exposed structures. These can include bridges, building siding and roofing panels, truck and bus frames, as well as metal sculptures. It was initially used in the 1930s for ore wagons to help them resist corrosion. With its unique finish, it also eliminates the need for repainting or recoating of the steel.

There are elements that weathering steel can’t withstand, however. It shouldn’t be used for applications that will be exposed to chlorine. Chlorine will cause the rusted surface to corrode and can lead to premature failure of the material.

At OFR Metals we stock A606 Type 4 in coil and sheet. For more information on product availability, contact your local sales representative as it may very between branches

Is Stainless Steel Magnetic? It Depends.

Have you ever wondered why you can stick a magnet on one stainless steel fridge, but not another? They are both stainless steel, so why doesn’t it stick to both? Well, the answer is in the makeup of the steel. So, let’s see if stainless steel is magnetic.

Is Stainless Steel Magnetic? The Type of Stainless Plays a Role

Ferritic

There are different families of stainless steel and all have different physical properties. A less expensive stainless steel would be considered a ferritic steel. Ferritic stainless steels typically have better engineering properties than their counterpart, austenitic, but have reduced corrosion resistance due to lower nickel and chromium content. This makes ferritic stainless steel magnetic.

Ferritic steels provide an advantage in many applications in which thinner materials or reduced weight are required. They are also non-hardenable by heat treating.

Typical applications for ferritic stainless steels include automotive and truck exhaust systems, catalytic converters, agricultural spreaders, heat exchangers, kitchen equipment, and roofing just to name a few.

Ferritic metals are classified in the 400 series. At OFR Metals we commonly stock 409 stainless and 430 stainless steel products.

Austenitic

Austenitic stainless steels are the more common types of stainless. These grades have higher chromium and nickel content. The higher nickel content makes austenitic grades non-magnetic.

Austenitic steels are similarly non-hardenable by heat treating, but also have excellent formability and higher corrosion resistance.

These type of steels are commonly used for kitchen equipment, appliances, automotive trim, architectural applications, chemical equipment, pharmaceutical equipment, and much more.

Austenitic stainless steels are classified in the 200 and 300 series. At OFR Metals we commonly stock 201 stainless, 301 stainless, 304/304L stainless, and 316/316L stainless steel products.

So, the next time you are shopping for a refrigerator be sure to bring a magnet. Higher quality (and typically more expensive) stainless steel appliances will not hold your alphabet magnet set. But unless you plan on placing your fridge out in the elements, you will most likely get along just fine with a ferritic stainless steel appliance. It’s still stainless after all.

For more information about our stainless steel products, contact your local sales representative.

Stainless Steel 304 and 316: What’s the difference?

Stainless steel 304 and 316 are the most widely used types of stainless steel. It can be difficult to visually, and sometimes characteristically, tell the difference between the two types of steel. So, what is the difference?

The biggest difference in the types of steel is the presence of molybdenum in stainless 316. Molybdenum is a metallic element that resembles chromium and tungsten in most characteristics. It is especially used for the strengthening and hardening of steel. The most common make up of stainless 316 is 16% chromium, 10% nickel, and 2% molybdenum – whereas stainless 304 is typically 18% chromium and 8% nickel. The molybdenum is added to stainless 316 to help resist corrosion to chlorides.

Stainless 304 has excellent resistance to corrosion and rust, but may be susceptible to corrosion from chloride solutions. Stainless 316, however, is ideal for applications that will be exposed to marine, pharmaceutical, and chemical elements.

The infographic below explores more of the differences, and similarities, between the two types of stainless steel.

For more information on which type of stainless steel you should choose for your next project or application contact your local sales representative. You can also find more information on how stainless steel is made here.

Stainless Steel 304 and 316: What’s the Difference?

stainless 304 vs stainless 316

Aluminum Alloys 3003 and 5052: What’s the Difference?

Aluminum 3003 and aluminum 5052 are some of the most commonly used aluminum alloys. But it isn’t always easy to differentiate the two. So, what is the difference?

Aluminum 3003

Aluminum 3003 is the cheaper of the two, but that doesn’t necessarily mean it isn’t up to par for certain applications. It has moderate strength and good formability and workability. It is also corrosion resistant making it ideal for applications such as heat exchangers and roofing and siding. Its major alloying element is manganese which allows for the formation of grains that absorb impurities and prevent corrosion.

Aluminum 5052

If that also sounds like aluminum 5052 that is because both alloys obtain similar characteristics. However, the 5052 alloy has a higher strength and greater corrosion resistance (including to salt water). Its major alloying element is magnesium. Magnesium overcomes the corrosive effects of the iron present in the alloy. It also has better finishing characteristics than the 3003 alloy. These attributes make aluminum 5052 a great fit for food processing equipment and truck trailers as well as marine and aquatic features.

Because the difference isn’t always obvious with these two mill finish aluminum alloys, we have provided an infographic for easy reference.

If you have more questions about the difference in these two aluminum alloys contact your local sales representative. For more information on how aluminum is made read our blog post on the process: “Aluminum: How it is Made.”

Aluminum Alloys 3003 and Aluminum 5052: What’s the difference?

difference between aluminum alloys 3003 and 5052

Hot Rolled Steel: How it is Made

Hot Rolled Steel SheetHave you ever wondered how different things are created? How a semi-truck is produced or what your water heater is made out of? If you are anything like me, this is a daily occurrence. The likely answer is that it started in a rolling steel mill in the form of a slab of unfinished metal and was worked into a hot rolled coil.

How Hot Rolled Steel is Made

Hot rolled steel is the most basic carbon steel product mills produce. It is used to manufacture products in which the surface finish is not critical, including automotive, truck frames, water heaters, agriculture equipment, compressor shells, guard rails and the list goes on.

The Heating Process

The process in which hot rolled is produced begins with heating slabs of steel to approximately 2,300 degrees Fahrenheit. The amount of heat directly affects the properties of the steel. Meaning, if the temperature is not high enough it can cause defects in the material. This is likely due to carbides (compound of carbon) and nitrates (polyatomic ion-an even more complex term) not fully dissolving.

When the hot material is being transferred from the furnace it reacts with the oxygen in the air. This reaction forms a mill scale or a flaky surface of iron oxides. The mill scale can affect the surface quality of the hot rolled steel if left alone. To remove the iron oxides the material is then sent through a mill scale cleanse. It is sprayed with high pressure water (much higher than your power washer at home).

Rolling Mill and Stands

The cleansed material is then sent through a rolling mill and is rolled from a thickness of roughly nine inches to an inch. The process consists of a series of four to five stands (set of rollers) that decrease the thickness and increase the length by horizontal rolls. The material is also squeezed vertically to control the width.

At this stage the material’s ends are sheared to create a transfer bar. The transfer bar is sent through another series of stands to further reduce the thickness to the desired sheet gauge.

The Cooling Stage

The flat-rolled steel is delivered across a runout table that consists of cooling sprays. The cooling rate may be modified for each strip to create the desired properties of the coiled end product.

After the material is cooled it enters coilers. Once coiled, the product is ready to be delivered to service centers, like OFR Metals, for further processing. It may also be delivered straight to fabricators.

The hot rolled material can also endure additional processes, including pickle and oiling, cold rolling, and other coatings.

The process of creating hot rolled steel sheets is much more interesting with visuals. Check out this great video to learn more about the hot rolling process.

Aluminum Tread: How it is Made

Aluminum TreadA couple months ago we took an in-depth look at how aluminum sheet and coil is made. We learned how it is mined, refined, smelted, and fabricated. But, mill-finished aluminum isn’t the only aluminum product we carry. We also process aluminum tread.
While the initial production of aluminum tread is the same as the other aluminum coil products, it goes through a couple extra steps to get the diamond-embossed texture.

Creating the Tread Design

The aluminum coil is sent through a synchronized set of rolls. The bottom rolls press against the top rolls to create a raised pattern (diamond) on the top side of the coil. This process can be done on stainless steel and some carbon steel as well.

OFR Metals Processing

After receiving aluminum tread coils we can then cut it to our customers’ desired lengths. The standard thicknesses we carry are .045-.125 and we supply it in both sheet and coils.

Benefits of Tread

Tread is used in a variety of industries and found in both external and internal environments thanks to its corrosion resistance.

Other benefits of tread include:

  • Strength
  • Durability
  • Weldability
  • Skid resistance

Uses of Aluminum Tread

Tread is used in a variety of industries. Let’s look at some of the most common.

Walkways and Ramps

Vijay Chennupati Nettle CaveOne of the most common uses for aluminum tread is walkways. The diamond texture offers slip resistance to ensure safe walking. The most common place I think of tread walkways are warehouses and school portables. Could you imagine walking up the ramp to go to your 7th grade English class in the middle of winter if the ramp isn’t made of steel tread? Students would be falling all over the place. Or a worker walking up a ramp into a warehouse in a rainstorm with his/her hands full of boxes. Let’s just hope the boxes aren’t full of fragile items and the worker is OK.

Truck and Trailer Parts

Horse Trailers (tread)Another common place to find aluminum tread is on trucks and trailers. It is a great material to use on truck bumpers and mud flaps due to its durability and corrosion-resistance. Aluminum tread is made to withstand the salt and sand on the roads during harsh winter conditions.
While the above are two of the more common uses for aluminum tread it is not exclusive. Look for it on siding panels, food trucks, tool boxes, running boards, etc.

 

Electro-Galvanized Steel: How it is Made

Recently we discussed how galvanized steel is made. It is a very interesting process, at least I think so.

electro-galvanized steel coilHow Electro-Galvanized Steel is Made

Today, however, we are going to take a look at a different process application of zinc, electro-galvanization. In the galvanizing process the finish is obtained through a hot-dip or continuous galvanization process. Electro-Galvanized is made through an electrochemical process.

Electrochemical Process

The electrochemical process involves the steel being immersed in a cold zinc bath while an electrical current is run through it. This is also known as electroplating.

electro-galvanized, electrolythic bathThe zinc acts as an anode to protect the steel. An anode is the positively charged electrode (electrical current) that attracts electrons and anions (a negatively charged ion). The steel is preserved from corrosion by cathodes. Cathodes are the negatively charged electrodes that attract cations (positively charged ions).

Conversion coatings are then applied to the metal to enhance the corrosion protection even more. This builds up an additional layer of zinc and chromium hydroxides resulting in a blue tinted finish to the material.

Now that we have had our chemistry lesson for the day, let’s discuss the benefits of electro-galvanized steel.

Benefits of Electro-Galvanization

The electrochemical process allows for a thinner zinc deposit layer so the steel has a higher corrosion resistance and higher performance.

The finish of electro-galvanized is readily paintable. This is an important quality to industries creating products such as trailers, appliances, and agriculture equipment.

Contact your local sales representative to learn more about the quality of our electro-galvanized steel. And stay tuned to learn a little bit more about what electro-galvanized steel is used for.

Aluminum: How it is Made

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 your hot Maserati…Oh, you don’t drive a Maserati? Well, this is awkward. Anyway, what you may not know is that your [insert car brand here] basically started with dirt.

aluminum mining, dump truck, dirtMining

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.

aluminum sheet, leveler, cut to lengthFabricating

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.

The steel mills we work with roll it into large coils and sent it to us by train or truck. We then slit it, shear it, or cut it to your specific length.

aluminum coilAluminum comes in a variety of different finishes. The most common we, at OFR, use is mill finish 3003, mill finish 5052, painted, anodized, and even aluminum tread.

Aluminum has many desirable qualities. It is lightweight and strong, 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.

So, go green my fellow Buzz readers! Or not, that’s up to you.

Check back next month to learn about specific uses of aluminum.

Hat Tip: Alcoa and Wikipedia

Galvanized Steel: How it is Made

Galvanized steel coils, ofr metalsMany people know what galvanized steel is. It is used for a wide variety of applications ranging from HVAC ductwork to gardening pails; household decorations to garbage cans. The spangle finish on the surface makes it visually appealing, but also makes it more durable and corrosion resistant.

So, how is galvanized steel made? Where does that spangle come from? Well, let’s find out.

Hot-Dip Galvanization

Galvanized steel is a carbon steel that has been coated with zinc. The most common method of zinc coating is the hot-dip process.

The hot-dip process consists of submerging the carbon steel into a molten zinc bath (approximately 680 degrees Fahrenheit). When the material is removed from the zinc bath and cooled a reaction to the oxygen in the air occurs. The reaction causes the zinc to become part of the steel (an iron-zinc alloy bond). The new surface finish appears to have a crystalline finish or spangled finish.

While this is the most common form of galvanization, it is often used for steel products that have previously been fabricated as the thickness of the final product is not easily controlled. Another method of the galvanization process is continuous galvanizing.

Continuous Galvanizing

Continuous galvanizing applies the zinc coating to the surface of a continuous ribbon of steel (coil) as it passes through a zinc bath. The coil travels at speeds of approximately 600 feet per minute.

As the coil leaves the zinc bath it carries with it an extra layer of molten zinc. The extra zinc is removed with high pressure air (air knives) to create the desired thickness. The material is then allowed to cool and the spangled finish is formed.

Skip with Galvanized Steel FinishContinuous galvanizing allows for more precise control of the thickness and is typically used for steel products that have not yet been fabricated. As the coating thickness increases, the risk of losing some coating during fabrication or forming also increases.

Overall Surface Finish

Galvanized coil and sheet are produced for applications in which corrosion resistance is important. The zinc coating lengthens the life of the end product, making it desirable for manufacturers. The appealing surface finish also makes it desirable for the consumer.

Stainless Steel: How it is Made

Stainless steel sheetToday we are taking a turn from carbon to discuss stainless steel. 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 OFR Metals 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 periodic table 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

“OK, great. So… how is it made?”

I’m getting there dear Buzz readers. We had to cover the basics first. Here we go…

stainless steel mining cartMining

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.

stainless steel roughing millHot 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 (which we defined while discussing how hot rolled is made).

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

“OK, then what happens?”stainless steel delivery train

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.

railcar unloading coilSkip prefers the train, as he gets sea sick.

When we receive the material we process it further to ensure our customers are getting the product they need.