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It’s not uncommon for someone to assume tube and pipe are interchangeable terms. You yourself may not have ever considered what the difference might be. If asked, what might be your guess: maybe they’re called pipes when made of metal, and tubes if made of PVC? Are they simply the same thing no matter what the name, the way different people might refer to soda versus pop?

Basically, it comes down to use: tube is a structural element, while pipe is used to transport fluid or gas. While both types are lengthy hollow cylinders, their use means they are different in their measurements, desired qualities, and even shapes.


10 Differences Between Tube and Pipe

1. Size Measurements

Pipe is more approximate in its measurements, with sizes being referred to as nominal pipe size (NPS). The pipe’s inner diameter and wall thickness are the most important dimensions, and vary according to strength. A very strong pipe will have thick walls with a smaller inner diameter than an equivalent NPS with thinner walls.
When measuring tube, its outer diameter and wall thickness are also important dimensions. Unlike pipe, these will be the exact measurements of the tube’s cross section.

2. Wall Thickness

Pipe wall thickness is known as its schedule, and determines the liquid capacity of a pipe. Two pipes with the same NPS number but different schedule numbers will have a difference in inner wall thickness.
Tube wall thickness is defined by gauge, with the wall’s width increasing along with a higher gauge number.

3. Production Sizes

Pipe comes in a wide variety of lengths, often 6 feet or more. Tubes, on the other hand, are most often smaller parts. Many are 5 inches or less, although larger tubes can be used for some applications.

4. Materials

Many different materials can be used for pipe: iron, copper, brass, and PVC. Tube is most often made of some type of steel, whether that’s carbon, low-alloy, or stainless steel.

5. Shapes

A pipe will always be round. Tube can be made in round, square, and other shapes.

6. End Connections

The ends of pipes can be straight, beveled, or screwed. Tube ends are commonly threaded or grooved for quicker connections.

7. Tolerances

An item’s tolerance is the acceptable range in its measurements: any deviations in its straightness, shape, or strength. Pipe tends to have a wider tolerance, so long as it meets its designated schedule requirements. Tube is the opposite, being made with strict tolerance guidelines. Because tube is intended for structural and often mechanical use, strength is a high priority. Repeated quality checks are made on a tube’s straightness, gauge, and outer surface.

8. Production Process

Pipe manufacturing is quite efficient and speedy, with many items being made to stock. Production of tube is more exacting due to its strict tolerances and quality checks, which means a lengthier, more labor-intensive process.

9. Delivery

Due to the difference in production, availability also varies between pipe and tube. Pipe, especially if ordered in made to stock sizes, is likely to have a quick delivery. Tube generally takes longer to produce and ship

10. Price

As you may have already guessed, the time and effort used to produce tube also translates to a higher price tag. While pipe can be pricey, especially if made of metals like copper, the average price of pipe will be lower than tube.

Welding is a complicated process, and there can be several pitfalls on the way to completing a successful weld. The choice of welding method, how carefully all materials are cleaned before proceeding, the experience of the welding operator: just a few of the many factors that can make or break a welding job. But one of the most important is your choice of metal. Working with metals that are more compatible to welding will make this process much easier to complete, and boost your chances of a good outcome.
During its exposure to the intense heat used during welding, metal begins to expand and soften. Welding involves connecting those softened edges together, with the use of a filler metal to create a join. Doing this quickly helps reduce the risk of the metal heating to the point of melting, which can thin the material and create a weaker join. So from the start, choosing a metal more compatible to welding helps reduce the risk of a bad weld.


The Four Most Popular Welding Metals
1. Low Carbon (Mild) Steel
Mild steel is one of the most weldable metals available, and this is due to the very quality featured in its name: its low percentage of carbon. In other circumstances, carbon is a great benefit when it comes to alloying steel; it reinforces the strength and hardness of the material, making it less ductile. However, that strength can become a downfall when it comes to welding. The higher the carbon content in the steel, the greater the risk that the heat of welding will create microstructures such as martensite within the material. These microstructures are more brittle than the surrounding metal crystal structures, and end up weakening the metal’s overall strength.
The more ductile a metal, the less likely it is to develop these microstructure flaws within the material. Mild steel is the most ductile of the steel family, so it takes easily to the welding process. Choosing low carbon steel means eliminating much of the risk of a disappointing weld before the process even starts.

2. Cast Iron
On the other side of the spectrum from mild steel, cast iron has an extremely high carbon content — about 2% of its overall formulation is carbon. Just as in steel, the high amount of carbon makes the metal quite strong but also very brittle. However, cast iron is still a good candidate for welding because of its relatively low melting point. This quality means a shorter period of sustained heat is used during welding, which prevents heat damage or burn-through.

3. Stainless Steel
Welding is already a complicated process, and the complex chemical composition of stainless steel can make it even more tricky. The chromium in stainless is what produces the metal’s distinctive shine and excellent corrosion resistance, but the same element can be a stumbling block during welding. The intense heat of welding leads to chromium bonding with the carbon in stainless steel, leading to warping and making it more vulnerable to rust.

It’s important to properly identify the grade of stainless before processing begins, because the formulation of stainless steel will help best determine what type of welding method should be used. Ferritic and austenitic stainless steels can be more easily welded. Martensitic stainless steel grades, which are primarily alloyed with chromium, are more prone to cracking. However, with careful attention paid throughout the process, especially with monitoring welding torch temperature, stainless steel can be welded successfully.

4. Aluminum
Aluminum welding is a balancing act, because the metal possesses qualities that are both beneficial and risky to welding. Its ductility makes it easy to weld, but its high degree of thermal conductivity is an obstacle. The heat during welding can easily spread throughout the metal, making it expand more significantly than heated steel. Then during its cooling period, the aluminum must be monitored to prevent the development of craters and cracking as it shrinks back to its original size.
Yet despite the difficulties, aluminum is one of the most popular welding metals. Its appealing properties such as corrosion resistance, durability, and relative low cost make it worthwhile to take the extra care during welding.

As you might guess, tool steel earns its name by being primarily used for tools. If you then picture a steel screwdriver, pliers, or a wrench, you’d be right – but the items created of tool steel group consist of much more. Within the steel industry, tool steel also refers to machine tools, including those used to manufacture other metal products. To meet the standards of this demanding usage, tool steel is known for being extremely hard, resistant to abrasion and deformation, and its ability to hold a cutting edge. While the steel’s chemical composition is important, the method of production must be carefully controlled to achieve the proper qualities expected in tool steel.

Tool Steel Groups
Tool steel is classed into six groups, all made of carbon steel alloyed with one or more of these main elements: molybdenum, tungsten, chromium, and vanadium. Most tool steel originates from recycled steel scrap, but not all steel scrap is suitable for tool steel. Alloy scrap containing elements which resist oxidation (such as nickel, cobalt or copper) will impede the development of carbides in the metal’s structure, and carbides are crucial to creating tool steel. To ensure the metal will be an optimal mix, tool steel will typically consist of 75% mill scrap supplemented by purchased steel scrap.
The first step is primary melting, where the scrap is heated until molten. Most often this is done in an electric arc furnace (EAF) due to it being a lower-cost production method. However, it is key to avoid contamination during the melting process to create the highest-quality steel. While the EAF is widely used for tool steel, there is some risk of contamination from dust or traces of oxidation-resistant metals from previous batches. For top notch tool steel, an alternate method known as electroslag refining (ESR) is used to melt the steel. Instead of a furnace, ESR uses electric currents to superheat and slowly melt the metal. While a more expensive process, ESR will produce a more refined type of steel without apparent surface imperfections.
After melting and alloying, the steel is poured into ingot molds and then forged into the desired shapes. This is where the six groups of tool steel are determined by their processing:

• Water hardening: Also known as W-group tool steel, this group’s defining property is being water quenched. Quenching in water does risk warping or cracking steel with its rapid cooling, and results in a relatively brittle metal. For this reason, water-hardened tool steel is not considered appropriate for high-temperature industrial uses; once the temperature nears 300 degrees Fahrenheit, there is noticeable softening of the steel parts. Typical items made of W-group steel include scissors, smaller hand tools, and springs.

• Shock-resisting: S-group tool steel is notable for its toughness and ability to withstand repeated impact. This is achieved by using low carbon steel during its production, since higher carbon content results in a harder but more brittle product. Alloying with silicon, tungsten, and chromium gives additional wear resistance and tensile strength. It’s then quenched in oil, which allows for a gentler cooling than water and helps produce a metal with a high degree of durability. Items made of S-group tool steels include tableware dies, impact hammers for nails guns, and shear blades used in cutting heavy steel plate.

• High speed: This group is mainly used for cutting tools, which requires a very hard and abrasion-resistant type of steel. Tungsten, chromium, and vanadium allow HS steel to withstand very high temperatures, such as the heat friction created while cutting other metals. It also manages to hold a cutting edge with repeated use, allowing for higher speeds while cutting without having to pause to resharpen. HS steel can be found in various cutting tools such as drill bits, saw blades, and milling cutters.

• Hot work: Hot-working (H-group) steels are used to cut and shape materials at very high temperatures. To achieve a steel that can withstand prolonged exposure to intense heat, H-group steels are made of a low carbon steel with a higher percentage of alloying content. This produces a tool steel with a high amount of carbides, giving it good overall toughness and wear resistance. The most common use for hot work steel is to produce other metal items because it can withstand the heat needed to forge and cast other metals. It’s used in machinery such as pressure dies, extrusion, and forging equipment.

• Cold work: This tool steel type is narrowed down further into three groups known as the A series (air-hardened), O series (oil-hardened), and D series (high carbon/chromium). All three are intended to be used to cut or form materials at low temperatures.

1. A-series: As the name suggests, steel in this series is hardened via air. Because of the quenching method and its high chromium content, A-series cold work steel is known for low distortion during heat treatment. This makes it a good fit for machining purposes, and so can be found in dies, forming tools, and gauges.

2. O-series: Oil-quenching avoids the cracking and warping risks brought on by water-quenching, and is used for larger parts which require minimal distortion. It offers good wear resistance and toughness, lending itself to a wide range of applications as a general-use cold work steel. Typical uses of O-series tool steel include stamping dies, bushings (metal parts used to absorb vibration and friction), shear blades, and other cutting tools.

3. D-series: Made of a high-carbon steel with a high alloy percentage of chromium, this can also be categorized as a type of stainless steel. However, unlike typical stainless steel, its corrosion resistance is limited and thus is not used to make consumer products. Instead, D-series tool steel applications include cutters, dies, plastic injection molds, and machining rollers.

• Special purpose: this group includes tool steels with alloying elements such as nickel, which typically resist the formation of carbides. The extra time and effort needed to produce these tool steels makes them too expensive for general purposes, so they are manufactured for specific use. Special purpose tool steel can be found in plastic molding dies, zinc die casting, and drills.

If there is one constant amongst professional and home chefs, it’s the belief that the single most important tool to possess is a good knife. A sharp knife is easier to control, requiring less force that might lead to slippage and hand injuries. It slices through foods more cleanly, requiring less effort to cut and chop. Professional chefs prize their knives so highly, they carry them to and from work to ensure they always have their preferred tools on hand.
But what differentiates one knife from another? What is the reason for one knife being priced at $20, and another at $200? Most often, it comes down to its material: when it comes to knife construction, the type of steel will have the greatest impact on its performance.

First, we need to determine the qualities that make up a good quality knife. Some of the most important characteristics include:
• Corrosion resistance: prevention against rust and pitting
• Edge-holding capability: the length of time a knife can keep its sharp edge
• Strength and ductility: the knife’s ability to absorb force without damaging its shape
• Hardness and wear resistance: the toughness of the knife, along with how frequently it can be sharpened
• Workability: the steel’s ability to be formed into the desired knife shape

The difficulty lies in producing a knife that fulfills as many of these criteria as possible, because they can conflict with each other. A stainless steel knife with great edge retention will require a lot more effort when it comes to sharpening. Ductile knives have good tensile strength, which allows them to flex during cutting and therefore avoid breaking – but they also need regular sharpening since they lose their edge more quickly. Added chromium or vanadium in the steel will boost a knife’s corrosion resistance but make it easier to snap with too much lateral pressure.
So the construction of knives depends on balancing these factors, while producing the best type of knife for a consumer’s needs. With these criteria in mind, we can examine the best choice of metal for knifemaking.

Carbon Steels
Carbon steels are just as the name describes, steels where carbon is the main alloying element. A higher level of carbon produces a very hard and wear-resistant steel. This is highly desirable for knifemaking, because that strength and hardness means the knife can be ground to an acute degree of sharpness. The knife will also retain the razor edge for an extended time during its use.
However, that sharpness often comes at a high sticker price, plus the added fuss of regular maintenance. High carbon steels are more prone to rusting than other types of steels, which means they will begin to develop rust if left wet. In humid environments (either due to climate or a small, steamy kitchen), it may be recommended to keep the blade oiled between uses to guard against rust. The high carbon content also reacts to acidic foods such as tomatoes and onions, darkening the blade and leaving a patina. While this patina does protect the steel from corrosion, some users may find it unsightly. If so, washing the knife and patting it dry immediately after each use will help preserve the blade’s shine. With careful maintenance, a carbon steel knife can be a lifetime investment; its hardness and durability will allow for many years of use.

Tool Steels
This class of steel is typically alloyed with four main elements: chromium, tungsten, vanadium, and molybdenum. This alloy mixture produces a steel that is extremely hard and resistant to abrasion and deformation. Because of this toughness, it is most often used in machinery for extruding, pressing, and cutting other metals, which is why it earned the name “tool steel”.
When used for knifemaking, tool steel generally goes to the production of utility and combat knives. Like high carbon steels, tool steels are quite hard which means they can be ground to an extremely sharp edge. But it also has pitfalls that make it less suitable for the regular wear of cooking knives: a propensity to rust, increased risk of snapping with lateral pressure, and the edge can develop nicks and chips. The alloying elements help protect against corrosion, but depending on the knife’s use, it may not always be convenient to clean it immediately which will contribute to its wear. But it will stay very sharp for a long time, making these knives valued assets to soldiers and hunters in the field.

Stainless Steels
Produced by adding chromium and other elements to steel, stainless steel offers a high degree of corrosion resistance. While it can begin to rust if treated carelessly, a stainless steel knife is easier to maintain compared to a carbon steel knife. Keeping the blade clean and dry will generally be enough to prevent against corrosion and darkening. The chromium in the alloy also gives the distinctive silvery sheen of stainless steel, and helps resist tarnishing.
The main disadvantage of stainless steel is that it is a softer and more malleable material than carbon steel. Carbon steel’s extreme hardness gives it the ability to be honed to a razor edge. In contrast, a stainless steel knife is more difficult to sharpen, is more prone to deformation while sharpening, and is unlikely to reach the same peak sharpness of a carbon blade. However, that softness may not necessarily be a drawback. Most home cooks don’t require a super-sharp knife, and a stainless steel knife does keep its edge for quite some time. Its ductility also means less risk of chipping the blade, since the softer steel is better able to absorb force during chopping. The affordable price of most stainless steel knives, along with their low maintenance, is why they are the best-selling option on the market.

Often when we speak of heat, it concerns scenarios we’d rather avoid: getting sweaty and sunburnt from the summer sun, overheating laptops or car engines, maybe singeing your hair after leaning too close to a candle. And rightly so! In all these cases heat can be damaging, whether to your possessions or your own self.

Yet despite some risks, heat is greatly beneficial. The sun’s beams feel warm and pleasant after a cold winter. The flames of a stove burner or grill cook your food. And when it comes to metal, heat is no different. Too much heat can damage metal to the point of weakening or destroying it. But heat is also a transformative force, from forging the metal to hardening it and modifying its mechanical properties.

There are four ways the application of heat affects metal:

• Structural
• Electrical Resistance
• Magnetism
• Thermal Expansion

Structural

Heat is a crucial part of the metal making process, with furnaces heated to such high temperatures that metal ore turns molten. However, it’s not always necessary to go to such extremes to affect the properties of the metal. Any time metal is heated, the atoms making up the metal or alloy begin to move. Given enough heat and then carefully cooled, the crystal structure of the metal can be reshaped into a lattice that is much stronger than prior to heat treatment. In the case of high carbon steels, heat application allows the iron to absorb additional carbon, which produces an exceptionally hard and strong steel.

Electrical Resistance

As metal is heated, the electrons within it will absorb energy and move faster. The faster the electrons move, the more likely they are to collide with the metal’s atoms and scatter them. Electrical resistance measures how strongly the metal works against this potential scattering as the temperature rises. That means the higher the electrical resistance of a metal, the lower its conductivity.

Magnetism

There are three elements with naturally magnetic properties, known as ferromagnetic metals: iron, cobalt, and nickel. But once heat is applied – and especially as the temperature goes up – the metal’s natural magnetism is reduced. If heated to a certain point known as the metal’s Curie temperature, its magnetic property will be reduced completely.

Thermal Expansion

As metal is heated, it begins to expand; its volume, length and overall surface area will grow as it continues to absorb more heat. This is due to the atoms making up the metal, which increase their movement as the temperature rises. This movement creates vibrations within the metal’s structure to the point that it swells, an occurrence which is known as thermal expansion. For safety reasons, any metal structure such as bridges or buildings must be designed to accommodate a certain degree of thermal expansion and contraction. Otherwise, you run the risk of damaging the metal as it warms and cools.