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.
In this article, we’ll discuss how experienced machine shops like Eagle CNC think about the complex relationship between heat treatment and machinability. Determining where heat treatment fits into the CNC machining process is a vital consideration for machining parts to net shape quickly and cost-effectively.
Eagle CNC is the Eagle Group’s state-of-the-art machine shop, specializing in CNC machining of both ferrous and nonferrous castings, forgings, bar stock and burn outs. At Eagle CNC, we machine new parts directly from raw stock, or from parts that have been shell cast or investment cast by our sister companies, Eagle Alloy and Eagle Precision. While our workpieces start in a variety of states, nearly every product we machine undergoes heat treatment before delivery.
Eagle Alloy provides a wide range of metalcasting services. In addition to casting hundreds of alloy grades that can be formed into virtually any castable shape, our foundry is fully equipped to heat treat the majority of parts we manufacture. In this blog, we’ll be opening the doors to our heat treatment facilities. You’ll get to know what kind of heat treat equipment we utilize to deliver superior products that consistently meet performance expectations.
Casting a part into its required shape does not fully prepare it for a life of service – only heat treatment can ensure a part performs exactly how it should. With the exception of a handful of nickel-based specialty alloys, Eagle Alloy heat treats just about every part that is cast in our facilities. From annealing and normalizing to stress relieving and quenching, we have the furnaces, quench tanks, data and expertise to take a product from inception to delivery.
Metal manufacturers utilize a number of tools to control the mechanical and physical properties of raw materials. An alloy’s chemistry is only one part of the equation: obtaining the final properties can only be achieved through heat treatment. In this introduction, we'll cover the following topics:
- Why heat treatment is important for metalcasting
- Heat treatment for carbon steel vs heat treatment for stainless steel
- The importance of using ASTM standards
- Key heat treatment processes used by foundries and machine shops
Heat treatment is a broad term describing a range of thermal processes used to control an alloy’s properties. These processes ensure a finished product carries the mechanical and physical properties demanded by its application. Encompassing both heating and cooling, heat treatment incorporates a few distinct and equally important phases:
- Ramp-up: heating the metal;
- Soak: maintaining the metal at a desired temperature for a specified amount of time;
- Cooling: cooling to a specified temperature at a controlled rate and in a controlled environment.