2040 – 04 – Finding Melting Points

The temperature where a metal changes from a solid to a liquid is its melting point.
The opposite of the melting point, when a metal changes from a liquid to a solid, is the freezing point. Pure metals have freezing and melting points that are often very close in temperature.

To picture this idea, imagine an ice cube is your pure metal. Ice melts and freezes at 0 degrees Celsius. If your ice cube is at negative ten degrees Celsius, then you heat it up ten degrees, it will melt. If it’s at 4 degrees Celsius, and you cool it down to 0 degrees Celsius, it will re-freeze.

For pure metals, the freezing and melting points are the same. Pure metals need extra energy to melt from a solid to a liquid. This extra energy is referred to as fusion.

Because they combine a variety of materials, metal alloys melt differently than pure metals. The process is much slower and has different terminology:

– The liquidus marks the point at which the alloy is entirely melted
– The solidus marks the point at which the alloy begins to melt.

  1. Do Alloy steels melt the same as pure metals? 

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2040 – 01 – Defining Physical Properties

2040 – 01 – Defining Physical Properties

When we talk about a metal’s physical properties, we’re referring to the way a specific metal responds to forces in its environment, like heat and electricity. Some key physical properties include a metal’s mass and weight, the point at which it melts, the point at which it bends or breaks, and whether it can conduct electricity or transmit heat. A material’s physical properties dictate whether it’s suitable to be used in the manufacturing, forging, or electronics. It’s imperative for workers who create and forge metals to know the melting properties of the materials they’re working with. Similarly, electricians need to […]

2040 – 02 – What is Mass and Weight

2040 – 02 – What is Mass and Weight

Mass and weight are common terms, and are often used as synonyms. But mass and weight actually have two distinct meanings: Mass refers to the number of molecules packed into an object. If a material has great mass, it has more tightly packed molecules. It’s also key to remember that an object’s mass remains the same regardless of its weight. Weight describes gravity’s pull on an object. Consider this example: an object floating in the ocean might weigh less than an object sitting on land, but they both have the same mass.

2040 – 03 – Defining Density

2040 – 03 – Defining Density

If you know a metal’s mass, then you can figure out its density. Density refers to the size and closeness of the molecules that compose a material; it’s the mass-per-unit volume. A high density means that an object is tightly packed with molecules. Pound cake, for example, has high density, while angel food cake has lower density. A common figure used in manufacturing is the strength-to-weight ratio. It compares the density of a metal to its strength. This comparison shows the value of a metal’s strength relative to its price, which usually depends on its weight. Titanium, for example, has […]

2040 – 05 – Examining Specific Heat

2040 – 05 – Examining Specific Heat

To describe the amount of energy that it takes to heat a material by exactly one degree, we use the term “specific heat.” An object’s molecules move faster when the temperature increases, and slower as it cools. Depending on their composition, different molecules vibrate at different speeds; exhibiting resistance to slowing down or speeding up, making the materials they compose harder to heat up or cool down. Metals that have molecules that move more slowly have a higher specific heat. It requires more energy to encourage these molecules to vibrate. Using a cutting tool generates heat as the blade meets […]

2040 – 06 – Understanding Thermal Conductivity

2040 – 06 – Understanding Thermal Conductivity

Heat is generated when a metal is cut, but heat can also move through metal. The speed at which heat moves through metal is called thermal conductivity. It works almost like a game of telephone: when one part of a material heats up, its molecules begin vibrating, which causes its neighboring molecules to vibrate as well. For example, when you stir hot soup with a metal spoon, heat from the soup travels up the spoon and you can feel it in your hand. Some materials have higher thermal conductivity than others: a silver spoon would get hot very quickly, while […]

2040 – 07 – What is Thermal Expansion

2040 – 07 – What is Thermal Expansion

When a material heats up, its molecules acquire more energy, becoming more active and taking up more space as they move. This increase in activity is called thermal expansion. While some projects require workers to manipulate metals using thermal expansion, some materials expand more drastically than others and it’s important to be aware that even a slight change in volume can create defects in a finished product. A workpiece subjected to excessive thermal stresses can warp, crack, or fall apart.

2040 – 08 – About Electrical Conductivity

2040 – 08 – About Electrical Conductivity

If a material is electrically conductive, electricity can easily move through it. Electricity is transmitted through electrons and conductors promote the movement of electricity. A resistor slows the movement of electricity. Insulators, which are essential to modern electricity, are highly resistant to electric charge. Metals are held together by metallic bonds, which makes them great electrical conductors. A metallic bond has electrons that have a fairly unrestricted range of movement within their electron cloud. Their frequent movement means they can transmit electric signals quickly and easily. Ceramics and polymers are bad conductors because they have ionic bonds and covalent bonds. […]

2040 – 09 – Defining Corrosion and Degradation Resistance

2040 – 09 – Defining Corrosion and Degradation Resistance

A material’s ability to resist deterioration is another essential physical property. In metals and ceramics, deterioration is called corrosion, while deterioration in plastics is called degradation. A number of abrasive substances, such as salts, acids, water, pollution or even oxygen can cause a material to corrode or degrade. Corrosion can happen anywhere on a workpiece. But when it occurs in specific, often undesirable locations, corrosion is called pitting. Crevice corrosion can also occur, wreaking havoc along riveted or bolted joints. It’s key to point out, though, that not all corrosion causes damage – some corrosion is essential to a finished […]

2040 – 10 – Summary

2040 – 10 – Summary

A metal’s physical properties, like melting point, conductivity, and corrosion resistance, all define how it will be used in the manufacturing industry. Other essential factors, like its mass and strength-to-weight ratio also determine the types of projects to which a metal will be suited. When subjected to extreme heat, metals will melt and expand. Different metals have different melting and freezing points. Metal alloys have a range at which they melt, due to their mixed composition. Pure metals, on the other hand, melt and freeze at a particular temperature. The energy needed to heat a material by one degree is […]

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