Various steel and metal types have a number of different properties or qualities that are desired for their use, and one common need within the industry is to test or measure these physical properties. There are tests for everything in the metal world, from tensile strength to impact toughness, ductility and more – and, for those wondering why we didn’t mention it already, there are a couple common tests out there for metal and steel hardness, a very important quality.

At Wasatch Steel, we’re happy to help with not only a variety of steel products and materials, but also steel services and many other areas of assistance as you look to source the proper steel products for your project needs. The two most common tests used to determine metal and steel hardness are the Brinell test and the Rockwell test – these are relatively similar in a few ways, but also have some important differences that may define which you use for a given steel or metal test. Here’s a primer on metal hardness and why it matters, plus basics on both these test types, how they differ, and how they’re generally used.

Metal Hardness Basics

Metal hardness is a vital quality of any metal, and it refers to the ability of that metal or metal alloy to resist plastic deformation. It should be noted that this deformation refers to a specific location on the metal rather than a general location. In addition, metal hardness can be defined as a metal’s resistance to risks like indentation, scratching or abrasion.

Why is hardness important for metals within structural applications? Because it’s a direct measure of the metal’s ability to resist wear. Hardness may be impacted by a variety of factors, including the alloying elements used on a metal, heat treatment, work hardening, or any other hardening methods that might be considered.

Hardness tests were created to help us understand hardness levels, which can vary significantly even within the same family of metals. Next up, we’ll go over the hardness tests out there and how they differ, plus why and how they’re used.

Brinell Hardness

Technically speaking, Brinell refers to a scale of hardness that sets a numerical value on the hardness of a given metal. The method of acquiring the Brinell hardness of a metal is the Brinell test, and its full specifications are contained within ASTM E10 for those interested.

From a general standpoint, the Brinell hardness test involves pressing a certified Brinell indenter against a metal. This is done using a predetermined load and with a preset amount of time, which are specified as part of the test. Generally, the indenter will be a 10mm ball of hardened steel, providing roughly 3,000 kgf of force for steel and other similar metals.

However, when the test is being done for notably harder or softer metals, the test is changed, The indenter is applied first but then removed, and the width of the indentation it creates will be measured using a microscope. This measurement will then be converted into a hardness value using the basic Brinell scale.

Similarities to Rockwell Hardness

In several ways, the Brinell hardness scale we just went over is very similar to the other method, known as Rockwell hardness. Both are used to assign a numerical value to the hardness of a metal, and both involve a test that utilizes an indenter of a specific size, applied to the metal for a preset period of time and using a predetermined amount of force. Like the Brinell hardness test, the resulting indentation measurement from the indenter is converted into a hardness value using the applicable scale.

Differences From Rockwell Hardness

Now, there are also a few important differences between these two tests, and it pays to know them if you’re looking to test any metal for hardness. Here are these differences:

• For the Brinell test, a 10mm hardened steel ball is used as the indenter; for the Rockwell test, the ball will either be much smaller (usually under 4mm) or will be made from a diamond cone, depending on the specific metal being tested.
• The Brinell test is meant to measure the width of the indentation on the metal, while the Rockwell test measures the depth the indentation creates, establishing a zero position with a preload before the main load is applied. Once the main load is applied in the Rockwell test, it will then be removed and leave only the preload – and this distance traveled is what the Rockwell test machine measures.
• The conversion scales for these two types are not the same, and should not be mixed up for one another.

Common Uses of Tests

When it comes to the common uses of these tests, it would be a lot quicker to list the areas in which they are not used within the metal and steel industries. They’re quite literally everywhere, extremely important for understanding how a given metal will resist abrasion, scratching and other forms of wear – and how they will interact with other metals or materials also used in the construction process.

For this reason, they’re used across a huge variety of industries. They’re found in engine pistons and jet turbine blades, for instance, plus components like fixturing equipment, ship hulls and numerous other components where major wear is possible.

For more on the Brinell and Rockwell metal hardness scales and tests, or to learn about any of our steel products, speak to the staff at Wasatch Steel today.