Common Uses of Stainless Steel

Since the early 1900s, stainless steel has been a fixture in our everyday lives. This alloy can be found everywhere, from watches to skyscrapers and aircraft. Its strength, corrosion resistance, and affordability make it an appealing choice for many projects. Even better, stainless steel is fully recyclable! The alloying elements used in its chemical composition can be extracted from melted stainless steel, and then reused with no degradation in their performance.
Having learned of its valuable properties, it is little wonder that so many different industries rely upon using stainless steel. With a wide range of grades and alloys available on the market, a manufacturer can be sure to find a type of stainless steel to suit their needs. Here are five of the most common uses of this metal alloy:

Modern construction is largely dependent on stainless steel due to its strength, flexibility, and resistance to corrosion. Its durability makes it a good choice for both interior and exterior use. Skyscrapers and commercial buildings often have frames and exterior cladding made of stainless steel. Its durability means less time and expense can be spent on maintenance, since the metal remains rust-free.

Energy and Heavy Industry
The oil, gas, and chemical industries present a great challenge to construction. These industries typically operate in environments which involve high temperatures and corrosive, toxic substances. Specialized grades of stainless steel have been developed for these industries, designed for enhanced corrosion resistance and able to handle extreme ranges of temperature. These “super-steel” grades are used for storage tanks, pipework, and valves.
Crude oil is an extremely corrosive substance, so stainless steel is invaluable in the construction of offshore rigs and drilling components. Stainless steel can also be found making up the equipment for renewable energy sources such as wind or hydro power. Its resistance to developing rust allows it to withstand the corrosive effects of seawater and varying temperatures.

Automotive and Transportation
Stainless steel has long been an integral part of automotive manufacturing, although mainly used in the past for exhaust systems and trim. With the rise of environmental concerns, more auto makers are expanding their use of stainless steel in structural components due to its recyclability.
The transportation and shipping industries are highly reliant on stainless steel, from shipping containers to tanker trucks. Transporting chemicals and other substances requires strong, non-reactive metals like stainless steel. Its strength also allows for thinner containers, which saves on fuel costs. Its corrosion resistance then requires less maintenance and easier cleaning of those containers and other transport equipment.

Medical Instruments
The production of medical instruments has involved stainless steel for well over a century. While bacteria can form on its surface, its natural corrosion resistance means a stainless steel tool is unlikely to have cracks or grooves where the bacteria can harbor itself. This makes for easy and thorough sterilization of stainless steel medical tools. The stainless steel instruments can be sterilized and reused for many cycles before they will show enough wear to be discarded.

Food Production and Catering
When it comes to cooking, once again stainless steel’s durability and corrosion resistance play key roles. Many foods such as tomatoes are highly acidic, leading to corrosion and discoloration of aluminum or copper cookware. The more reactive a metal, the more it can potentially affect a food’s flavor, often for the worse. Stainless steel is an ideal material for food production and storage because it has strong corrosion resistance, which means the metal does not react to its environment or the substances stored inside it. This durability means less waste; knives, cutlery, and cookware can be used for many years before showing excessive wear.
Stainless steel is an even more important material in commercial food production. As in the medical industry, equipment sterilization is the utmost priority, and stainless steel can hold up to cleaning cycles involving high temperatures and strong anti-bacterial products. Its non-porous surface means bacteria are unable to hide away during cleaning, and lowers the chances of carrying over any germs between food production batches.

The Basics of Welding Stainless Steel

Cracking, spatter, incomplete fusion: just a few of the many pitfalls you may face when attempting a weld. While no approach is completely foolproof, your chances of a successful weld are much better once you have a good understanding of the basics. It is also important to tailor your methods to your choice of material; what works best for one type of stainless steel may not be as helpful with another. In this case, we’ll examine a few of the most popular methods of stainless steel welding.

The Material
There are many different grades of stainless steel, but they all have at least one alloying element in common: chromium. The addition of chromium is what makes steel ‘stainless’, with its characteristic shine and boosted corrosion resistance. However, adding chromium to the steel’s chemical composition – along with other elements such as molybdenum, silicon, or manganese – affect how the metal will react to heat. These elements lower the thermal conductivity of stainless steel, which means heat will not spread as easily through the material. This lack of efficient conductivity requires a stronger heat input, but higher temperatures or an extended welding time increases the chances of a burn-through or other heat-related faults. Whatever process you use for welding stainless steel, it will be a matter of balancing necessary heat input vs the potential for heat damage.

The Processes
There are several different methods of welding stainless steel, but most welders use one of these three types. There are other factors that can be considered in more detailed, but generally the selection depends upon the material’s thickness:
1. Tungsten Inert Gas (TIG) welding

This process is one of the most commonly used for welding stainless steel. TIG welding, often referred to as tungsten gas arc welding, creates a low heat input which makes it the best choice for thinner materials. The heat is generated using electricity, which powers an electric arc between the tungsten electrode and the base metal. An inert gas such as argon creates a sheathing environment around the electrode, protecting and cooling the tungsten. This dampening effect helps to keep a relatively low heat input, as well as creating less smoke and oxidation.

Low heat input means TIG welding is ideal for thin stainless steels or precision welds on critical joints. Its concentrated heat allows for a narrow fusion zone, which calls for a high degree of control over the welding process. After completion, a TIG-produced join requires little to no post-weld finishing.

2. Metal Inert Gas (MIG) welding

Also known as gas metal arc welding, MIG uses electricity to melt and join metal during a weld. However, unlike TIG welding, MIG requires the use of both an inert shielding gas and a solid wire electrode. This filler metal wire is continuously fed during the welding to create the arc between the electrode and base metal.
Due to the higher heat during the weld, MIG is best selected when welding thicker widths of stainless steel or steel plate. It can be adapted for semi-automatic welding processes, since the continuous wire feed allows for long joins. It also produces little spatter and easy cleanup after processing.

3. Resistance welding (RW)

TIG relies upon a welding operator and MIG can be done manually or through automation, but for manufacturers who require a highly automated process, resistance welding is key. The method involves an electrical current run through weld electrodes, which apply force to the pieces being joined (the “resistance” part of the process). This force is converted to heat, and the resulting heat melts the metal enough to join it together. When completed successfully, the molten metal at the point of contact will form a rounded weld, known as a “nugget”.

Unlike the other two processes, RW has a steep initial cost of equipment setup and requires a high amount of power. This means it has little portability and cannot be used in the field like TIG and MIG welding. However, for manufacturing purposes, resistance welding is ideal. It is fast, reliable, requires no filler metals or other materials, and is excellent for sheet metal applications. Stainless steel can get up to weld temperature very quickly using the RW method, so welding can be completed within a few milliseconds.

Aluminum Alloy Tempering Methods

Newly forged metals are extremely hard – hard to a fault, because such a degree of inflexibility makes the metal very brittle. This applies even to alloys made of naturally ductile metals such as aluminum. However, after some type of tempering treatment is done to ease the tension within the metal’s structure, the aluminum will be left stronger and more resilient than before.

Before beginning, it’s important to determine whether the aluminum being tempered is heat-treatable or not. If the aluminum alloy belongs to one of the following series, it should not be heat treated:
Series 1xxx: pure aluminum
Series 3xxx: alloyed with manganese
Series 4xxx: alloyed with silicon
Series 5xxx: alloyed with magnesium
Pure aluminum and aluminum alloyed primarily with one of the elements in the list above do not respond to heat treatment. In these cases, the material can be toughened through other means such as cold working or work hardening.

For the other aluminum series, their tempering can be done through annealing, homogenizing, solution heat treatment, and aging. Aging can then be further split into two groups: natural aging, and artificial aging (also known as precipitation hardening). Whatever the method chosen, the purpose of tempering is to alter the aluminum’s physical and mechanical properties without changing its shape.

For aluminum series not considered heat-treatable, annealing is the method used to temper the metal. Work hardening means the metal is placed under repeated strain during use, which causes the grain structures within it to slide against each other. These stretched areas are called slip planes, and as the aluminum continues to be used, there will be fewer and fewer areas left that are not already slip planes. If the aluminum continues to be used without tempering, eventually the metal will be overworked and break.
The annealing process essentially performs a reset on the aluminum. By exposing it to a relatively low heat of 570 to 770 degrees F, the strain within the metal lessens as the crystalline grain structure returns to its original form. Once cooled, the aluminum can again handle the creation of more slip planes.

When casting aluminum parts using molds, the edges of the part will cool faster than the interior. This uneven cooling affects the structure of the part since some areas, particularly around the edges, will have grains of pure aluminum. The interior may be more combined with its alloying elements, but have remaining pockets of pure aluminum. Because pure aluminum is quite soft, this means those grainy areas will be weaker.
Homogenizing reduces this issue by heating the aluminum to just shy of its melting point, around 900 to 1000 degrees F, and allowing a gradual cooling. Unlike the heat of the mold, the uniform heat during homogenizing allows the internal structure to develop more uniformly. Once this is done, the cast aluminum part will be much sturdier.

Solution Heat Treatment
Solution heat treating is similar to annealing, but the metal is quenched rather than being allowed to cool on its own. When aluminum cools naturally, a greater degree of precipitation occurs. This means the alloying elements within the metal may drop out of place within the metal’s internal structure, rather than being as fully integrated as when newly forged. The sudden cooling from a quench means the alloying structure will be locked into place.
Depending on the type of alloy, the aluminum is heated to 825 to 980 degrees F, almost near melting point. This heat prompts the aluminum and alloying elements to better combine into solid solution. It is then immediately immersed in water to bring a sudden drop in its temperature. After tempering, the part will be stronger due to its improved homogenization.

After quenching, there is some precipitation which happens naturally in aluminum alloy. However, this is not a drawback – the alloying precipitation helps to reinforce and lock in place the aluminum’s microstructure. If left at room temperature, natural aging will continue to develop for up to 5 days, with most of the hardening taking place within the first 24 hours. This aging window means aluminum can be shaped after solution heat treating, leaving a much stronger piece after both processes are complete.
With artificial aging, the process of precipitation in some alloys may require a second round of tempering to reach its maximum strength. The metal is exposed to a fairly low temperature of 240 to 460 degrees F, just enough to encourage the alloying elements to begin to precipitate within the metal’s interior. It is then quenched again and allowed to finish cooling at room temperature. While more labor intensive, artificial aging will result in a significantly stronger metal in a shorter time period.

The Differences between Carbon and Stainless Steels

In all likelihood, if someone were asked the difference between carbon and stainless steel, the answer would involve appearance: one is dull and one is shiny. That might sound simple, but it’s also true! While the finish of each steel is the most obvious difference, there are other, more significant ways they differ. Learning more about the characteristics of each steel type will help determine which steel is most appropriate for a project.

Corrosion Resistance
The most significant difference between the two is the high degree of corrosion resistance found in stainless steel. Both types of steel are vulnerable to corrosion due to their iron content, which reacts with oxygen to form rust. However, the addition of chromium in stainless steel alloy provides much more protection against corrosion. The chromium in stainless steel reacts more quickly with oxygen than iron, and the resulting chromium oxide forms a protective layer on the surface of the metal. The chromium oxide prevents further oxygen interaction with the metal, effectively stopping any continued corrosion.
Carbon steel alloys may also contain chromium, but not in the amounts found in stainless steel. This means carbon steel is vulnerable to the corrosive effects of rust, which leads to damaged metal unless regularly maintained. So in situations where corrosion resistance is a big concern, stainless steel will be the best choice.

Adding chromium as an alloying element in stainless steel not only boosts corrosion resistance, it is also the source of the metal’s distinctive shine. Carbon steel naturally has a flatter finish, and its vulnerability to corrosion leads to tarnishing and other discoloration. It can be sanded to smooth the metal and produce more shine, but unless some type of coating is applied to the polished carbon steel, the same rust and discoloration will develop.
Stainless steel, on the other hand, has a natural luster which polishing can increase to a mirror shine. Polishing also provides even more corrosion resistance to the metal, without the need for an additional protective coat. This is because any existing irregularities are sanded down during polishing, so corrosive particles are less likely to cling to the metal’s surface. For projects where aesthetics is an important factor, stainless steel may be preferable over polished or painted carbon steel.

Mechanical Properties
Both carbon and stainless steels are produced in multiple types and grades, so it can be difficult to make a clear distinction between the two kinds of steel. In general, stainless steels tend to be more ductile, while carbon steels have greater tensile strength. This is due to the carbon alloying percentage found in carbon steels. Carbon makes steel harder, to the point of becoming very strong and brittle with high-carbon steels.
However due to the variety of available carbon and stainless steels, these properties may not apply across the board. A low-carbon steel can be more ductile than certain types of martensitic stainless steel. Some stainless steel grades will be harder and with greater tensile strength than a low-carbon steel. Ultimately, the mechanical properties of any kind of steel should be considered for its specific use in a project.

As a general rule, stainless steel will be more expensive than carbon steel due to its alloying elements. Carbon steel may contain other elements, but is mainly made up of iron and carbon which are fairly affordable. Stainless steel is created with the addition of chromium, and also has higher amounts of alloying elements such as nickel and manganese. Each additional element to the stainless steel’s chemical composition increases the cost. For a lower budget project where aesthetics is a lesser priority, carbon steel will be the best way to go.

Selecting Tool Steel Grades

When it comes to industrial machinery such as drills, dies and cutting tools, tool steel is the favored choice. As you can tell by the name, it’s designed for this very purpose. High amounts of carbon and other alloying elements gives tool steel enhanced hardness and strength, qualities which allow it to weather the repeated stresses of manufacturing. But while all tool steel is tough, selecting the right grade of tool steel is important to ensuring you have the type best suited for the job. A good starting point is to first determine the exact purpose of the tool steel you plan to use:

1. Will it be doing work at low temperatures?
2. Will be doing work at high temperatures?
3. Do you intend to use it at high speeds?
4. Will the tool steel be involved in repeated impacts?
5. Will it be used for plastic molding?
6. What is your budget?

Low Temperature Work
For work performed at very low temperatures, the tool steel group known as cold work steel best fits the bill. All tool steels are very hard, but extreme hardness tends to be accompanied by increased risk of cracking. With extreme cold, metal can become even more brittle. So cold work steels are carefully quenched, using methods that allow the steel to retain some degree of flexibility. Quenching in oil (O-series), air (A-series), or adjusting the chemical composition to include more chromium (D-series) produces cold work steel that can perform well in low temperatures. While these cold work steels are pricier than water-hardened types, the mechanical benefits justify the higher cost.

High Temperature Work
Whatever the type of steel, any prolonged exposure to high temperatures will begin to affect its mechanical properties. As the temperature climbs, the atoms in the steel will increase their movement, creating structural changes within the metal. Because tools steels are already heat-treated prior to use, the application of more heat makes them even more vulnerable to structural changes. At worst, it can affect the steel’s crystal structure to the point of reversing the initial heat treatment. To avoid this, hot work steels are formulated with lower carbon and higher alloying content. The increased amount of molybdenum and tungsten produces a steel that can retain its hardness and wear resistance at extreme high temperatures.

High Speed Work
Tool steel used at high speeds are put under a great deal of pressure. High speed tool usage leads to increased friction, which means the steel will be exposed to both heavy wear and high temperatures. This means a metal must possess the durability of hot work steel, and even more resiliency to hold up to the friction. High speed tool steels typically include tungsten, chromium, and vanadium as their alloying elements to produce a very hard steel. This protects it against the pressure and abrasion of high speed work, while its hardness allows it to retain a sharp cutting edge during use.

High Impact Work
To undergo repeated major impacts, the necessary grade of tool steel must have a high degree of shock resistance. Tool steel is prized for its hardness, but that hardness means the metal can crack, chip, or lose its shape with impact. Shock resistant tool steels generally have a lower carbon content along with alloys such as silicon, sacrificing some hardness to give it more ductility and tensile strength. However, this does come at the cost of lower wear resistance. This means high impact tool steels are best suited for impacts only, rather than machinery that will experience more friction and wear.

Plastic Molding Work
The tool steels used for plastic molding are known as the P-series, or special purpose steels. These are much softer than the other types of tool steel due to alloying elements such as nickel, which impedes hardening during the forging process. While the hardness is decreased, P-series tool steel possesses enough malleability to allow it to be shaped into a variety of molding dies. After being heat treated, the tool steel molds can be used to produce plastic items. Theis grade of tool steels are rarely used for any other purpose, because the lengthy and complex manufacturing process makes it more costly to produce.

Cost of Tool Steel
As you can see, the more specialized the task of a tool steel, the more you should prepare yourself to spend. The price tag is well worth it: purchasing the right type of tool steel means it will perform better for its intended work and will last longer while doing it. Choosing the wrong type of tool steel can result in more frequent repairs or even replacements, both requiring an additional cost. However, for general usage not involving any extreme conditions, W-series tool steel will perform well. Due to being water quenched, these steels are the least expensive of all tool steels to produce or purchase. Hand tools, springs, and other small steel goods are typically made of this grade of tool steel.

The Strongest Metals

Out of the many metals found on Earth, which is the strongest? It’s a straightforward question, but not one with a simple answer. You may find yourself becoming rather philosophical, because first you must define exactly what it is you mean by “strength”. When it comes to metal, being strong isn’t just a matter of toughness. There are several different ways of determining whether a metal is strong, and it helps to know how these assessments are made.

Types of Metal Strength
There are four basic ways to test the strength of a metal:
• Compressive strength: This measures the metal’s ability to withstand squeezing or compression. Testing involves using external force to press the metal, in order to see how much stress it can take without affecting its shape.

• Yield Strength: This tests the metal’s elastic behavior, which is the tension it can take without becoming deformed or broken. This is performed through a bend test, where the ends of a bar or beam are bent towards each other into a U-shape. The amount of force needed to bend the metal, and then past its breaking point, will identify its yield strength.

• Impact Strength: As the name suggests, this measures the impact the metal can withstand from heavy blows. Stronger metals will be able to withstand a major impact, even repeatedly, without cracking or breaking.

• Tensile Strength: A metal’s tensile strength is its ability to resist tension, specifically when the material is being stretched. Metals with high tensile strength are better able to withstand this test, while metals with low tensile strength can be easily pulled apart.

Comparing Strongest Metals
Having learned about the different types of metal strength, it becomes clear that it’s unlikely for any single metal to lead in every category. A metal can have high marks when it comes to one or more types of strength, while being more vulnerable in another area. As a general list, we can consider these to be some of the strongest metals:

Out of all pure metals, tungsten may have the best claim to the title of Strongest Overall. It is very tough, has the highest melting point of any unalloyed metal, and tops all others when it comes to tensile strength. However, its major pitfall is impact strength. Due to its incredible hardness, tungsten is very brittle – so much so that it’s known to shatter upon impact when dropped. But when used as an alloying element in steel, tungsten greatly enhances a metal’s strength. Due to its hardness and high melting point, tungsten is often used in military and aerospace applications.

Chromium is not only the hardest metal on Earth, but the third hardest element overall: surpassed only by carbon (diamond) and boron in hardness. But like tungsten, that hardness makes chromium extremely brittle in its pure form. Its greatest value is as an alloy, lending itself to boosting both yield and tensile strength. It is also very resistant to corrosion and reflective when polished, so it has aesthetic appeal along with strength.

While titanium isn’t nearly as hard as tungsten and chromium, it has extraordinary tensile strength. It is a relatively low density metal, and beats all other metals when it comes to strength-to-density ratio. What that means in actual practice is that titanium can be produced to be thin and flexible, without sacrificing strength and durability. In addition, it is highly resistant against corrosion, cracking, and other metal failure. Its lightness and strength make it a prized choice in the medical and aeronautical industries.

Unlike the other three metals on this list, steel is man-made: an alloy rather than a pure element. Alloys have the advantage of combining several different metals, resulting in a chemical composition designed to boost the metal’s most useful qualities. Carbon steel on its own is a strong material, with the carbon contributing to the steel’s hardness and toughness. With additional alloying elements such as vanadium or tungsten, steel becomes one of the strongest and most versatile metals on the market.

Aluminum Alloys for Anodizing

Anodizing the Aluminum Series

While aluminum is the most common metal to be anodized, not every grade of aluminum alloy receives this type of processing. As time passes, aluminum oxide naturally forms on the surface of aluminum, creating a layer of corrosion resistant protection. This layer not only halts continued oxidation and corrosion, it also helps reinforce the metal from the hardness of aluminum oxide.
However, this oxidation develops most successfully on pure aluminum – and pure aluminum is limited in its usage due to being a relatively soft and weak metal. Alloying the metal will give it greater strength and durability, but those properties come at the price of affecting aluminum’s ability to oxidize. Anodization is a convenient method of producing a thin, even layer of protective oxide on aluminum alloy.
Because anodization uses the metal’s aluminum content to form this anodic oxide layer, in theory any type of aluminum alloy can be used for this process. But some types of aluminum alloy have much greater chances of producing a successfully anodized piece. Due to the different element combinations in alloys, the anodizing of some series will produce much stronger and aesthetically appealing products than others.

Expected Results of Anodizing Aluminum Series
1xxx Series
This series covers pure aluminum, or aluminum with such tiny amounts of other elements that it can be considered virtually pure. 1xxx series can be anodized, but the pure metal remains weak and can be easily damaged. With or without anodizing, 1xxx aluminum is not strong enough for most structural applications.

2xxx Series
The primary alloying element for 2xxx is copper, which produces a very hard and strong type of aluminum. Anodization does not offer much additional protection, because the copper impedes the development of an anodic layer. The processing also gives the metal a yellow tint which consumers generally find unappealing.

3xxx Series
Manganese is the main alloying element in this series, and results in a layer of good-quality anodization. Unfortunately, the anodic layer is likely to be an unattractive brown tint that can vary from piece to piece, making it difficult to match when using multiple sheets in a project.

4xxx Series
Like the 3xxx series, the main alloying element in 4xxx causes the metal to turn an unappealing color after anodizing. 4xxx is alloyed with silicon, and this results in a dark gray anodized aluminum with sooty black patches. These blotches are very difficult to remove, so when 4xxx is anodized, it is generally used in architectural applications.

5xxx Series
This series is alloyed with magnesium, and is well-suited to anodizing. Once complete, the anodic layer is transparent, strong, and offers long-lasting protection. However, the chemical composition in some grades of 5xxx aluminum should be examined carefully, because some elements within may make anodizing a bit tricky. If the magnesium content is very high, or it contains over 0.1% silicon, the oxide layer may appear streaky.

6xxx Series
Both magnesium and silicon are the alloying agents in the 6xxx series, and these aluminum grades are considered to be excellent candidates for anodizing. The anodic oxide layer is clear and strong, as long as the alloy’s magnesium content is kept below a certain percentage. The strength of anodized 6xxx aluminum makes it a good choice for structural and mechanical applications, but its attractive finish means it can function well for aesthetic purposes too.

7xxx Series
Zinc is the primary alloying element in 7xxx series aluminum, and it takes well to the anodizing process. This series is already known for being some of the strongest types of aluminum, and anodizing increases that quality even further. The only risk comes if the chemical composition of the alloy is high in zinc. For 7xxx grades with heavy zinc content, the otherwise clear oxide layer can turn brown.

What is Anodizing?

One of the greatest advantages of aluminum is its natural resistance to corrosion. Ferrous metals such as steel are highly vulnerable to corrosion due to their iron content; iron atoms react with oxygen to produce rust, which wears away and damages the metal. Aluminum atoms react even more quickly to oxygen, but its oxide doesn’t flake off as iron oxide does. Aluminum oxide is quite hard and difficult to remove from the metal’s surface, so it become a natural layer of protection from oxygen permeating the metal underneath.
However, this natural oxidation takes some time to occur – and manufacturers understandably want faster results to produce corrosion-resistant aluminum for sale. This is where anodizing comes into play: this electrochemical process enables oxide to form much more quickly than it would on its own. Unlike paint or plating, which can chip or wear away, the anodized surface layer is fully integrated with the metal itself to provide long-lasting protection.

The Anodizing Process
Anodizing is a multi-step process, but at its most basic it can be described as highly controlled oxidation. By treating the metal and applying an electric current, the aluminum atoms are prompted into an accelerated interaction with oxygen. The end result is a metal surface that is evenly and completely anodized, with a high degree of corrosion resistance.
These steps include:
1. Cleaning: A thorough cleaning must be done to prepare the aluminum for the processing. Either an alkaline or acid-based cleaner is used to remove any surface grease or dirt from the metal.

2. Pre-Treatment: The benefits of anodizing can be both functional and aesthetic. During processing, dyes and other treatments can be applied to create a more attractive appearance in the final product. To modify the metal’s finish, two procedures can be done as pre-treatment:

a. Etching: To achieve a matte finish, heated sodium hydroxide solution is applied to the aluminum. Sodium hydroxide, also known as lye, is an extremely caustic substance capable of corroding metal. The solution strips away any minor surface imperfections, leaving it smooth and matte.

b. Brightening: Mirror-finish aluminum is created by treating the aluminum with a concentrated mixture of phosphoric and nitric acids. Similar to the lye solution, the acids corrode away the metal’s top layer along with minor imperfections. Once complete, the result is smooth, shiny metal.

3. Anodizing: The cleaned and pre-treated aluminum is then submerged in an electrolyte solution. Anodizing requires electricity, and an acid solution provides a boost in conductivity. As the electric current passes through the tank containing the aluminum and solution, oxygen ions are released from the electrolytes and interact with the aluminum to form a layer of aluminum oxide. The process is carefully monitored to achieve the degree of oxide thickness for the desired product.

4. Coloring: To produce colored anodized aluminum, four different methods can be used. Since this is done during the anodizing process, the color will be highly resistant against fading, scratches, and other wear. Generally this is done through these four methods:

a. Dye: The anodized metal is immersed in a dye and lye solution.

b. Electrolytic coloring: An electric current sent through an electrolyte solution the dye to the aluminum’s surface.

c. Integral coloring: This process combines anodizing and coloring into one step to anodize, color, and seal the aluminum.

d. Interference coloring: The aluminum is treated with sulfuric acid and then soaked in dye.

5. Sealing: Although freshly anodized aluminum has the corrosion resistance of aluminum oxide, sealing offers an additional layer of protection. During the processing, the various chemicals used will leave microscopic “pores” open on the metal’s surface. Left unsealed, contaminants can be absorbed more easily onto the surface during storage, risking corrosion or discoloring. Once the pores in the anodic film are closed by applying a final seal, anodized aluminum will be highly resistant to scratches, abrasions, and color fading.

Hot Rolled Steel Grades

When it comes to steelmaking, production can be divided into two basic groups: cold rolled and hot rolled steel. In earlier eras, molten steel was cast into blocks known as ingots. These ingots were convenient to stack and ship, and could be melted back down when needed for use. In current times, steel manufacturing is done on a massive and continuous scale. To make this process more efficient, manufactured steel is produced to be as close to a finished product as possible.
Newly forged steel emerges as a continuous slab of red-hot metal, which is then fed into a series of mills. The process is similar to a home pasta maker: with each consecutive rolling, you will end up with a thinner and thinner result. As the steel progresses through the mills, the metal remains hot enough to stretch and thin out into a long strip. Once rolled out to the desired thickness, it can be cut into shapes such as bars, or thinned enough to be rolled into coil.

Most Popular Grades
Hot rolled steel is available in several different grades, which are the standards set for a steel type. Generally, steels in North America conform to the standards set by the American Society for Testing and Materials (ASTM), or those set by the Society of Automotive Engineers (SAE). ASTM steel grades always begin with an “A”, which is the letter assigned to ferrous metals. SAE steel grades use a four-digit number for identification.

A36 Hot Rolled Steel
One of the most popular grades of hot rolled steel, A36 is a low carbon steel alloy. The low percentage of carbon within A36 steel means it is highly versatile: it can easily be formed, machined, or welded.
The low amounts of other alloying elements such as nickel and chromium make A36 steel just average in corrosion resistance, but also keeps the price relatively low. For this reason, it is widely used in applications where cosmetic appearance is not a priority. You will often find A36 hot rolled steel used for heavy duty construction and equipment manufacturing.
Common applications include:
• Bridge and building construction
• Automotive frames and trailers
• Agriculture equipment
• Oil and gas equipment

1018 Hot Rolled Steel Bar
Another popular choice of hot rolled steel is 1018, which is a similar grade to A36. A36 is often the top choice in manufacturing, but 1018 will be selected if the application calls for bar or strip steel. It is even lower in carbon percentage than A36, and this low carbon in 1018 allows for excellent formability. The low carbon level also allows 1018 to be a fairly ductile type of steel which can be easily bent and machined.
Common applications include:
• Gears
• Pins and studs
• Steel bar in square, rounded square, hexagonal and other shapes

1011 Hot Rolled Sheet and Plate
SAE 1011 is a strong, low-alloy form of hot rolled steel. Its low percentages of carbon and other alloying elements means this steel grade is very hard and strong, while remaining easy to drill, form and weld. 1011 is strong and durable, but can be vulnerable to corrosion with its low alloying percentages. Exposed to the elements, the iron content of 1011 will begin to discolor, corrode, and roughen its surface. For added corrosion protection, an outer layer is often applied to the steel’s surface, through painting or processing such as galvanization.
Common applications include:
• Building and roofing construction
• Shipping containers
• Automotive parts
• Heavy equipment

What are Pipe Schedules?

For people new to working with pipe, referring to their “schedule” may be unfamiliar. Imagine you have two pipes in front of you: one labeled schedule 40, while the other is schedule 80. Both are manufactured of the same type of metal, with the same grade, and the same 3-inch diameter. So, what is it that makes these two pipes different, other than their schedule numbers?

First, it helps to understand the functional challenges faced by pipe. Pipe is designed to move along liquid or gas under pressure – pressure which can be internal, external, or both. To sustain fluid pressure, pipe must be strong enough to withstand a great deal of stress. This means the product dimensions of pipes aren’t simply measured by length and diameter, but its wall strength as well. A high-pressure fluid will require thicker pipe walls than pipes used for low-pressure applications like drainage.

Pipe Schedules
The wall thickness that determines a pipe’s strength is known as its schedule. Pipe schedules are a standard to identify wall thickness for the same size of pipe. The outer diameter of a particular pipe size will stay constant while the inner diameter varies according to the schedule type. Using the example of the 3-inch pipes, you can see the difference once you measure their inner diameter. The outer diameter for both pipes will remain approximately 3.5 inches, but their other qualities differ:

3” Schedule 40 pipe
• Wall thickness of 0.216 inches
• Inner diameter of 3.05 inches
• Weight per foot is 7.58 pounds

3” Schedule 80 pipe
• Wall thickness of 0.300 inches
• Inner diameter of 2.90 inches
• Weight per foot is 10.25 pounds

As you can tell, the schedule 80 pipe is significantly heavier due to its thicker walls. Those thicker walls mean schedule 80 pipe is better able to handle high pressure, which might cause greater wear or damage to schedule 40 pipe. Clearly, pipe schedules are quite important to ensure a project’s success and the best use of your funds. For home plumbing projects, schedule 40 pipe is sufficient, with no need to spend extra for schedule 80 pipe. For industrial uses, on the other hand, investing more money up-front for schedule 80 pipe may help prevent damage and costly repair work in the future.