What is Rebar?

Introduction: What is Rebar?

It’s likely almost everyone has heard of rebar, and seen pieces of it sticking out of a concrete wall or pillar under construction. However, it’s probably also safe to assume most people are not familiar enough to explain exactly what rebar is. Could they describe how is rebar made, and its intended use? We’ll take a closer look at rebar to help answer these questions.

What is Rebar?
Rebar, short for “reinforcement bar”, is a metal bar used to increase the tensile strength of concrete. Concrete is quite hard and has great compression strength, but it is much weaker when it comes to tensile strength. Simply put, this means concrete is prone to cracking or toppling over from its own weight when used for building. A concrete sidewalk rests on the ground, which provides enough support for concrete to stay whole and strong. But when building up for the walls of a stadium, or building across for lengths such as a freeway overpass, the concrete requires reinforcement. The insertion of rebar within the structure helps the concrete to withstand great amounts of pressure and tension.
Rebar is available in several types of metals, and can even be made of fiberglass, but the most commonly used is produced out of carbon steel. This is because steel possesses thermal properties similar to concrete, which means both the structure and the rebar buried within it will react the same way to temperature changes. As the temperature rises and falls, the concrete and steel will expand or constrict together, which helps to prevent cracking.

How is Rebar Made?
Steel rebar is almost always made of recycled steel, taken from the frames of cars, appliances, and machinery which are too old for continued use. These steel pieces are melted down and cast as billets, the term used for long unfinished steel bars. The billet shape allows the pieces to be easily stacked away in storage until needed.
To make rebar, the billets are heated to a very high temperature just short of the steel’s melting point. The red-hot billets are then fed into extrusion machines, squeezing the steel out like toothpaste from a tube. This process is repeated with a series of smaller and smaller extrusion diameters, until it results in steel rods of the desired size.
From there, tooling machinery is used to create the distinctive corkscrew ribbing found on rebar rods. These ribs help to anchor rebar within the concrete, preventing the rods from slipping or bending. The final step is shearing the rebar rods to cut them down to the desired lengths.

How is Rebar Used?
Concrete is an incredibly resilient material – some ancient concrete structures such as the Roman Colosseum are still standing, thousands of years later. However, most concrete does begin to degrade as it ages and begins to form cracks. Cracks allow moisture and air to seep into the concrete, speeding the process and weakening the material’s structural integrity. If left untreated, the cracks can allow oxidation of the steel rebar, causing rust and weakening the steel.
Compromised rebar can lead to serious consequences, because the steel is no longer providing the strong degree of strength and reinforcement to the structure as intended. Not only does it provide building strength, but rebar can also help to prevent cracks from forming. And if cracks do form, the placement of rebar helps experts to predict where they’re most likely to occur, and those spots can be reinforced.
For best effect, rebar is often laid in a grid pattern. The carbon steel’s strength is maximized in grid formation, allowing it to reinforce the concrete despite tensile forces coming from many different directions. Ordinarily, non-heat treated carbon steel would be considered too brittle for construction use. Heat treatments such as hardening or annealing allow steel to retain much of its hardness while making it less breakable. However, this is not a concern when carbon steel is used for rebar, so the alloy can be left untreated. The steel is extremely hard and brittle, and highly vulnerable to rust, but once embedded within the concrete, these qualities are no longer liabilities. The extreme hardness of untreated carbon steel is a benefit, giving the structure added strength and stability.

The Five Types of Carbon Steel Round Tube

The Five Types of Carbon Steel Round Tube

When it comes to steel manufacturing, one type has the lion’s share of the market: by volume, carbon steel accounts for 90% of the steel produced each year. The increasing growth of the oil and gas industry means carbon steel tube and pipe are in constant demand, with over 50% of all steel tube and pipe being used for petrochemical production. Carbon steel’s ability to withstand corrosion and extreme environmental conditions makes it an excellent choice for parts used in oil and gas processing, from drilling to refining and transport.

Round Tube
While tube may look similar to pipe, the two shapes are used for different purposes. Pipe is used to transport substances such as oil and gas, while tube is used as a structural element. For this reason, tube is generally made to be stronger and more robust than pipe. Tube can also come in a variety of shapes such as round, square, or rectangular. When carbon steel round tube is needed, there are five types available for use:

Electric Resistance Welding (ERW)
Produced from cold-formed coil made of low carbon steel, this method uses electric resistance welding to form it into round tube. The welding itself can be done in several ways, but most often through an automated process. This means high quality ERW tube can be produced at a low manufacturing cost, making it a very popular choice for customers.
ERW tube’s affordability and versatility leads to it being used in many applications including automotive frames, supports and stands, and internal machine components.

Cold Drawn Seamless (CDS)
CDS tube starts with steel billets, heated to an extremely high temperature and pierced with machinery to create the tube’s hole. The steel is then rolled to elongate the tube and shrink its diameter, and cooled once it has been formed to the desired shape. This process results in very sturdy tube with thick walls and a smooth surface.
Because CDS tube is not only strong but aesthetically attractive, it is often used for visible automotive parts such as roll bars and frames. Other common uses include hydraulic cylinders, infrastructure columns, and boiler tubing.

Drawn-Over-Mandrel (DOM)
This type of tubing is produced through machining with the use of mandrels. A mandrel is a taper bar, used to gradually increase the diameter of a part placed on it – such as the small mandrels used by jewelers to resize and widen rings. For round tubing, steel coil is sheared and joined by welding, then finished by using mandrels. This machining creates high-quality tube with excellent levels of hardness, strength, and consistency.
DOM tube is used extensively in the automotive industry, found in parts including shock absorbers, dampeners, and seat frames. It is also regularly used in hydraulic parts such as pumps and cylinders.

This type is manufactured to meet the necessary requirements of hydraulic lines, including the strength to withstand the stress of containing pressurized fluids. Similar to CDS, hydraulic starts with carbon steel bars which are heated, pierced, and rolled until it results in sturdy tubes. Hydraulic tube has a very shiny and bright finish which makes it appealing for its aesthetic quality as well as its overall strength and utility.
Due to its high degree of strength, hydraulic tube can also be used for applications where tubes will be bent or fitted together.

Hot Finished
Also known as seamless tube, this type is made by piercing and rotating an extremely hot piece of carbon steel. The rotation creates the shape, and it then goes through a series of mills to reduce the tube’s diameter and wall thickness. This fairly low-cost process creates a versatile, easily machinable tube. However, hot finished tube sizing tends to be less precise than other types, and its finish looks rougher. For this reason, hot finished tube is typically found in applications where aesthetics or size variance are unimportant.
Seamless tube can be found in heavy-duty uses such as construction and drilling equipment, pillars, and wind turbine components.

Suitability of Welding Carbon Steel

Carbon steel is just as described: a steel alloy containing added carbon, with the carbon making up 0.05% to 2.0% of its weight. This percentage range means carbon steel is a sprawling category, covering many different types of steels with varying levels of carbon. Steel with any other combination of alloying elements can be included in this category, so long as they contain carbon.
Clearly the many possible chemical compositions of carbon steel make it difficult to make blanket statements about this metal. Carbon increases the hardness and strength of steel, but the percentage of carbon added creates different results with the steel’s mechanical properties. Those properties then affect how the metal reacts to further processing such as welding. It is very important to understand the exact qualities of a selected carbon steel to produce a successful weld; doing otherwise risks metal damage or a weld that may fail later during use.

Carbon Content
The most important decision before beginning a weld will be the type of steel to use. Carbon steels are organized as three basic types:
• Low carbon steels: containing less than 0.30% carbon by weight
• Medium carbon steels: containing 0.30% to 0.60% carbon by weight
• High carbon steels: containing 0.61% to 2% carbon by weight

Each of these groups will weld differently due to their carbon content. The higher the steel’s carbon level, the more prone it will be to weld cracking. Low carbon steels can be much more easily welded, which is why they are the typical choice for this process.. However, high carbon steels can be welded, provided extra care is taken with the more brittle material. Heating high carbon steel prior to the weld, as well as afterwards, will help prevent cracking. Additional filler metals may also be used with high carbon steel to create a better weld.

Carbon Equivalency
Once the type of carbon steel is selected, further determination of its weldability is done using the carbon equivalency formula. This formula examines what effect the other alloying elements besides carbon may have on a weld. The percentages of alloying elements are calculated as an additional degree of carbon – and that boosted carbon level translates into a steel considered more difficult to weld. As an example: using the formula means a medium carbon steel with no added manganese will be judged as easier to weld than the same carbon metal including manganese alloy.

Overall Chemical Composition
Even after selecting a lower carbon steel, and calculating an acceptable carbon equivalency, the overall chemical composition should still be reviewed. Some elements will just not take well to welding, even with a great deal of effort. Any amount of lead in carbon steel, for instance, will significantly raise the probability of weld cracks. Other common alloying elements such as sulfur or phosphorus can have the same effect, resulting in a weak or failed weld. While carbon steel with trace amounts of either sulfur or phosphorus can still be welded, the percentages must remain extremely low (approximately 0.05% or less) to avoid weld cracking.

Cooling Rate
The job is still not complete after creating a weld, because as it cools, cracking may develop. Carbon is again the main culprit here, due to it making the steel more brittle. With higher levels of carbon and equivalent alloys, the metal must be cooled at a slower rate to prevent cracks from occurring.
In addition to the steel’s carbon percentage, other factors must be accounted for during weld cooling. The thickness of the steel being welded will affect the cooling rate, and thinner material has a higher risk of distortion. The temperature where the weld is being performed is also important. In cold temperatures, preheating may be necessary even for lower carbon steels, while it can be performed without prior operations in warmer environments.

Buyers Guide To Carbon Steel

¬¬¬¬Six Questions when Buying Carbon Steel

Carbon steel is a widely used material, found in items from structural steel to kitchen knives. However, these industries do not necessarily use the same grade of steel. At its most basic, this metal group is made up of any steel alloy with added carbon. The carbon percentage will usually be somewhere between 0.05% to 2.0% of the metal’s overall weight.
In any chemical composition, a range of 0.05 to 2.0 is a significant margin. Steel is no different: when it comes to formulating steel alloys, the variance in carbon percentage has a transformational effect on the produced metal. Carbon strengthens and hardens the steel, but decreases its ductility. That means the higher the carbon percentage, the less flexible the steel becomes. A high-carbon steel grade put under high or repeated stress would be more brittle and liable to crack. A grade of steel with lower carbon content will be more ductile, but not nearly as strong.
So before starting a project with carbon steel, you should carefully consider the grade you select. It can make a big difference in the end result’s success. Reviewing these six questions beforehand can help in making your choice:

1. Will the carbon steel be machined?
Machining is a process where the parts and shapes are cut from the metal. Because lower carbon grades are relatively softer steel, they are more easily and efficiently machined. A high carbon grade can be used, provided the alloy’s chemical composition includes sulfur which improves the steel’s machinability. Without sulfur, the hardness of high carbon steel will result in major wear of the cutting tools.

2. Will the carbon steel be welded?
In general, the same grades of lower carbon steel more suited for machining can be more easily welded as well. High carbon steels can be used, but often require additional treatments before and after welding. And in contrast to machining, the steels grades containing sulfur are not recommended for use in welding. The sulfur in these alloys will have a higher risk of developing cracks at the weld join.

3. Does the carbon steel need to be heat-treatable?
When it comes to heat, a good rule of thumb is 0.3. Steels with a carbon content of 0.3% or higher can be heat treated easily. This is due to the carbon itself, which helps the formation of martensite crystallization within the steel, reinforcing its hardness and strength. Grades of lower carbon steels lack the carbon necessary for martensite formation, making heat treatments unsuccessful.

4. Does the carbon steel need good formability?
Due to the wide margin of carbon percentages across grades, it can be difficult to say which grades might be more formable than others. The selected grade is often dependent on the shape: rolled sheet requires a much more ductile type of steel, but forming pieces such as angle and beam can involve a wider grade range. Overall, the more ductile carbon steels – meaning, lower carbon grades – are much easier to form.

5. Does the carbon steel need high corrosion resistance?
Because steel’s main element is iron, it is vulnerable to oxidation leading to corrosion. This is an accepted fact that when using any grade of carbon steel, it will develop a certain amount of rust. In applications where corrosion resistance is a high priority, it may be better to consider using another material such as stainless steel instead. To minimize corrosion of carbon steels, they can be coated to create a barrier between the metal and its environment. This can go from involved processes such as galvanization or plating the metal to simply applying a coat of paint.

6. How strong a carbon steel is needed?
The steel’s application is crucial to deciding the strength needed for your metal. High carbon steel is incredibly strong, but if intended to be used for making small parts such as nuts and bolts, your needs would be better served by low carbon steel’s machinability. But while low carbon steel is more formable, it would be worth the greater effort when making tools to use high carbon steel for its hardness and durability. While it may be tempting to select the hardest and strongest material available, its actual use should be an important factor in selecting the right carbon steel.

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.