On Metal Ductility, Hardness and Malleability

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On Metal Ductility, Hardness and Malleability

metal ductility hardness malleability

When discussing physical properties related to how hard or soft a given metal is, there are a few specific properties that will generally be considered. These properties are ductility, hardness and malleability, and knowing how they differ and how to factor in each one within a given piece of metal is important for a few different reasons.

At Wasatch Steel, we’ll be happy to detail the properties of any of our steel sheet, steel pipe or other steel products, which we provide to clients for a huge variety of needs and project types. What’s being referred to when discussing each of these three properties, and which additional factors may impact these in specific ways? Let’s have a look.

Metal Ductility

When you hear discussions about metal ductility, what’s being described is the materials’ ability to change its shape without breaking. This is done through the process of plastic deformation, which occurs when the metal is placed under high levels of stress. The ability to change shape in this way is important for a few reasons, mostly related to how the metal will be used.

In many cases, being able to deform a piece of metal without it breaking is preferable. One example is when creating steel pipes – it’s often necessary to bend the steel slightly in order to get the desired shape, and if the metal were not ductile enough it would simply snap under the pressure. Ductility is also a key factor in many welding applications. When two pieces of metal are being joined together, they need to be heated to a high enough temperature that they become malleable. If the metal being worked with is not ductile, it will not be possible to heat it to the necessary temperature without it breaking.

There are a few different ways to test for ductility. One method is to take a small sample of the metal and stretch it until it breaks. The amount that it can be stretched before breaking is a good indication of the metal’s ductility. Another method is to compress the metal until it deforms plastically. This can be done with a machine that applies pressure to the metal from different angles. The amount of pressure required to deform the metal plastically is another way of measuring its ductility.

Metal Hardness

When discussing the hardness of a metal, what’s being described is the material’s resistance to local deformation, usually from indentation. Generally speaking, there are three forms of hardness a metal may be considered under:

  • Indentation: For this process, a constant load will be applied to the material to form an impression, which will then be measured using the Rockwell hardness scale (more on this in a moment).
  • Rebound: To find elastic hardness, a drop hammer is used to apply a blow to the surface of the material. The height that the hammer rebounds from is then measured and recorded using what’s known as the Leeb hardness test.
  • Scratch: Using the Mohs scale of hardness, a material’s scratch hardness is determined by comparing it to another material of known hardness. If the first material can scratch the second one, then it is harder than the second one.

The most common way of testing for hardness is by using a machine called a Rockwell hardness tester. This machine presses a small diamond or carbide ball into the surface of the metal. The amount of force required to indent the surface of the metal a certain depth is measured and used to calculate the hardness.

Hardness is an important property for many applications. In general, harder metals are more wear resistant and more difficult to machine. They are also more likely to break rather than deform when placed under stress.

Metal Malleability

Malleability is a measure of a metal’s ability to be deformed under high levels of stress without breaking. This is different from ductility in that, while both properties describe a metal’s ability to change shape, malleability specifically refers to the material’s ability to be hammered or pressed into thin sheets without breaking.

Malleability is an important property for many applications that involve shaping metals. For example, when creating coins, the metal needs to be malleable enough to be pressed into the desired shape without breaking. Malleability is also a key factor in many jewelry-making applications.

There are several factors that impact the malleability of a given metal, but likely the two most important are the temperature and the strength of the metallic bond that’s been created. Temperature has a significant impact on malleability because, as temperature increases, the atoms in the metal begin to vibrate more. This makes it easier for the atoms to slide past one another, which makes it easier to deform the metal. The strength of the metallic bond also has an impact on malleability; metals with weaker bonds between their atoms are generally more malleable than those with stronger bonds.

Knowing the hardness, ductility and malleability of a given metal is important for a variety of reasons. These properties can impact everything from the wear resistance of the metal to its ability to be shaped into a desired form. As such, it’s important to consider all three when selecting a metal for a given application.

For more on this important area of the metal world, or to learn about any of our steel products or services for varying project needs, speak to our team at Wasatch Steel today.