Imagine a medieval blacksmith hammering a sword fresh out of the fire. With the weapon still red-hot, he dunks it in water. The water hisses and boils around the submerged steel as it turns color from glowing orange to grey. This iconic scene of rapidly cooling a workpiece is called quenching, or quench hardening, and is one of the oldest and most common heat treatment processes used to harden and strengthen common carbon steels. In modern metallurgy, superior corrosion resistance for most stainless steels is also an important property achieved through quenching.
Internal stresses form naturally during many manufacturing processes. Machining, stamping and welding, for example, are common manufacturing methods that augment the amount of stress in a material’s fabric. And although stress build-up is a natural byproduct of these processes, too much of it leads very commonly to part distortion. Most of these stresses must therefore be removed before a part can be considered ready and safe to use. Thanks to heat treatment, these stresses can be relieved (without changing a part’s mechanical properties) through a thermal process known as stress relieving.
Joining multiple metal parts together into a single, cohesive unit is an indispensable process to manufacturing. Bolts, screws, and adhesives are often used to unite separate parts, but many applications call for a more solid connection. Thanks to the craft of welding, manufacturers are able to effectively create a single part from multiple components. Casting facilities are also able to use welding to repair minor casting defects, improving overall process efficiency and reducing part cost.
Understanding the weldability of various alloys is key to creating welds that last and parts that perform in the field. As a mechanical property, weldability is also an important consideration in designing and producing cast parts.
Hardening a metal achieves much more than simply making it mechanically harder. It also improves strength, making the alloy more resistant to plastic deformation, and can aid with corrosion resistance. However, a harder metal is also often a more brittle metal. As such, hardening is usually just one part of a properly designed heat treatment plan.
Because hardening can be accomplished through numerous heat treatment strategies, it’s important to know what options are available to a casting customer, how the methods differ, and where hardening fits into the master plan.
In this article, we’ll explore the science and practice of hardening, and explain when conditions are appropriate for a particular hardening strategy. Whether you’re working with the Eagle Group or another metal manufacturer, hardening is an important step in manufacturing, so it’s good to know the basics.
Normalizing is one of the most common heat treatments used in manufacturing carbon steel. It is a vital process to ensure that the mechanical and physical properties of a carbon steel workpiece are integrated and distributed uniformly across the material.
In steelmaking, material uniformity is achieved by carefully controlling a casting’s microstructure – specifically, its grains. Grains are distinct areas of crystal structures oriented in the same direction. Multiple grains together make up a metal’s structure. The goal of normalizing is to target these grains in order to even out the differences between them, resulting in a more mechanically stable product. It’s for this reason that the process is named as such: it ‘normalizes’, or homogenizes, grain size, shape, and orientation.
“Hardness” is a concept we use every day to compare objects: fresh bread vs. stale bread, a baseball vs. a softball. In manufacturing the definition is a bit more specific: hardness is a measure of a material’s ability to resist localized scratching or deformation by indentation at a specific loading location.
Our understanding of hardness and relative hardness between materials is key to manufacturing metal products. The correlation of hardness with other mechanical properties also makes it possible for us to predict, with a high degree of accuracy, the strength and ductility of a material without submitting it to destructive testing.
Past civilizations had practical reasons for caring about metal properties. They asked questions like “Can I break my enemy’s sword before he breaks mine?” or “How thick does my armor need to be to provide enough protection?” These warriors had a vested interest in material strength.
In previous installments of our series on Metal Properties, we’ve discussed characteristics that set metals apart from one another, as well as those that distinguish them from other nonmetallic elements. Conductivity represents an array of essential features that go to the very heart of what defines a metal. In this article we will be asking: what are the factors affecting the conductivity of metals? What are the most thermally and electrically conductive metals, and why does conductivity matter for manufacturers?
All materials possess some degree of conductivity. One of the main characteristics of metals is their ability to conduct heat and electricity, so metals are all relatively conductive compared to non-metals. However, even within metals you’ll find a broad range in levels of conductivity. A sound knowledge of where various metals fall on the spectrum helps manufacturers choose the right alloy for each product.
Corrosion is a common challenge affecting the surface of most metal parts. While corrosion often only affects the aesthetics of a metal part, severe corrosion can affect performance and can even lead to equipment failure. Corrosion is such a widespread challenge that the global cost of corrosion is estimated to be $2.5 trillion annually, according to a study by the National Association of Corrosion Engineers (NACE).
Here we explore many of the ways corrosion can manifest in a material, and the techniques manufacturers use to prevent corrosion from affecting part performance.
In the metal manufacturing industry, mechanical properties play a huge role when choosing the right alloy for each job. Throughout casting and machining processes, as well as during the product's useful life, the chosen material will be subject to many external forces. It’s up to the manufacturers to create products that perform as needed every step of the way. By understanding mechanical properties, manufacturing professionals can make the right choices for materials and processes.