• Skip to main content
  • Skip to header right navigation
  • Skip to site footer
SyBridge Technologies

SyBridge Technologies

Bridging the gap between innovation and mass production

  • Capabilities
    • Design & Engineering
    • Rapid Prototyping
    • Tooling
    • Advanced Manufacturing
    • Supportive Injection Molding
    • Reliability Services
  • Technologies
    • 3D Printing
    • Urethane Casting
    • CNC Machining
    • Injection Molding
    • Manufacturing Intelligence
    • SyBridge Connect
  • Industries
    • Life Sciences
    • Health & Beauty
    • Consumer Products
    • Aerospace
    • Mobility & Industrial
  • Resources
    • Material Selector
    • Press Room
    • Knowledge Center
    • Events
  • About Us
    • Evolution
    • Sustainability
    • Careers
  • Contact
    • Locations
Home / Resources / Guide to Heat Treatments for CNC-Machined Metal Parts

Guide to Heat Treatments for CNC-Machined Metal Parts

July 24, 2020 by SyBridge Technologies
Heat Treatments CNC

Originally published on fastradius.com on July 24, 2020

CNC machining is a subtractive manufacturing method that uses tools and rotation to create parts from solid blocks of material. Parts can be machined in a number of different ways, which makes CNC machining a versatile manufacturing process that can be used to create everything from automobile chassis to surgical equipment.

Heat treatments are a technique that have been developed to either make metals more workable during the manufacturing process or to improve the material characteristics after machining has been completed. Applying heat and other elements to metal parts in strategic ways enables the creation of parts with superior ductility, hardness, toughness, and other properties.

Here are some of the most common heat treatments for CNC-machined metal parts.

Annealing

The annealing process involves heating metals to a critical temperature, which varies by alloy, maintaining that temperature for a period of time, and then slowly air cooling the metal to create the desired microstructure within the metal.

Annealing is typically applied to metal alloys after forming to increase the ductility of the material, which makes harder metals less prone to cracking or fracturing during the machining process.

Case hardening

Case hardening is a heat treatment method that increases the hardness of the exterior layer of carbon or alloy steel without hardening the interior material. Metals like iron and steel often have a low carbon content, so applying a combination of heat and a carbon-rich substance to the surface gives an otherwise low-carbon alloy a high-carbon, hardened exterior. This makes case hardening ideal for applications that require flexibility but a durable, wear-resistance outer layer, such as engine camshafts.

While hardening processes provide tremendous improvements to the strength of metals, they also tend to increase the material’s brittleness. For that reason, case hardening is typically performed after machining.

Stress relieving

CNC machining can create stress within part material that, if left untreated, can severely compromise the part’s overall quality. Like annealing, stress relieving involves heating metal alloys to high temperatures and slowly cooling them. However, unlike annealing, this heat treatment is applied after the machining process to remove residual stresses. Stress relieving improves the mechanical properties of a part without changing the material’s structure or hardness.

Quenching and tempering

Also known as martensitic transformation, quenching and tempering is a two-part method specifically designed to increase the hardness of steel parts.

In the quenching process, the steel or steel alloy is heated to a high temperature, which causes the iron’s crystalline structure to change from ferrite to austenite. This allows the metal to absorb more carbon.

The steel is then rapidly cooled to “lock in” the iron phase change, while the addition of carbon results in an extremely strong crystal lattice structure called martensite, which has excellent surface hardness properties.

Tempering, on the other hand, is the process of heating metals to high temperatures (although temperatures much lower than the material’s critical temperature, as opposed to annealing) after the metal has been quenched. This reduces the material’s brittleness, while improving its toughness  and prolonging the life of the part.

Precipitation hardening

Precipitation hardening is used to increase the strength of malleable metals like aluminum, stainless steels, and superalloys. The process is similar to quenching and tempering and involves heating metal to a high temperature, quenching it, then heating it to a lower temperature for an elongated period. This allows precipitates in the alloy to disperse and reduce dislocation (irregularity) movement within the microstructure, drastically increasing the strength and hardness of the metal.

Precipitation hardening is commonly applied to components in aerospace applications where reducing weight without sacrificing strength is critical — pieces made from precipitation-hardened aluminum, for instance, can achieve strengths comparable to stainless steel, but at about one-third of the weight.

Choosing the ideal heat treatment process

Heat treatments can deliver incredible improvements to the material properties of metal parts. However, it’s important for product teams to do their research to determine which heat treatment is best-suited for a given part. While quenching and tempering may be ideal for creating high strength steels, it’s a far less useful process for treating aluminum alloys. Luckily, determining which treatment process is right for you is made simpler with the help of a trusted manufacturing partner.

SyBridge believes that going the extra mile should be the norm. We’re a team of engineers and designers who are passionate about making the things we once thought impossible. We bring this drive to each project, providing end-to-end support on projects of all varieties, volumes, and timelines. If you’re ready to find out what superior quality at competitive prices looks like, contact us today.

Category: Knowledge CenterTag: CNC Machining

Related Articles

PEEK

Know Your Materials: Polyetheretherketone (PEEK)

CNC

The Ultimate CNC Machining Guide

Polyoxymethylene (POM), more commonly known as acetal or its branded name Delrin®, is an engineering plastic offering low friction, high stiffness, and excellent dimensional stability. Polyoxymethylene is a category of thermoplastics and includes many different formulations of the material, all of which vary slightly. As such, it’s important to learn as much as you can about each type before choosing one for your next project. Delrin® is a semi-crystalline engineering-grade thermoplastic widely used to create highly precise parts. In general, Delrin® provides impressive dimensional stability and sliding properties. It’s known for its high strength, wide operating temperature range (-40°C to 120°C), and excellent mechanical properties. Here’s everything you need to know about this material, from how it’s made to its best-fit applications. Inside the polyoxymethylene production process Acetal was first discovered by German chemist Hermann Staudinger in 1920 before it was commercially synthesized by research chemists at DuPont, the original manufacturers of Delrin® plastic, in 1956. Like all other plastics, acetal is created by distilling hydrocarbon fuels down into lighter groups called “fractions,” which can then be combined with other catalysts via polymerization or polycondensation to produce a finished plastic. To make an acetal homopolymer like Delrin®, anhydrous formaldehyde must be generated by causing a reaction between aqueous formaldehyde and alcohol to form a hemiformal. The hemiformal is then heated to release the formaldehyde, and the formaldehyde is polymerized by anionic catalysis. The resulting polymer is stabilized when it reacts with acetic anhydride, which creates polyoxymethylene homopolymer. Acetal comes in many different commercial varieties and formulations, each with its own advantages and disadvantages. For example, Delrin® 500 is medium-viscosity, all-purpose polyoxymethylene that has a good balance of flow and physical properties. It can be used to produce parts via CNC machining and injection molding and is frequently used to manufacture mechanical parts, fuel systems, and fasteners. Delrin® 1700P, on the other hand, is a very low- viscosity, fast-molding resin that is best suited for parts with complex shapes, thin walls, long flow paths, or multi-cavity tools. It also offers the best molding thermal stability for deposit-free molding in demanding conditions. Since there are dozens of different formulations of acetal, it’s important to do your research and make sure your prospective plastic offers all of the properties you need for your application. Delrin® plastic properties and mechanical specifications small black Delrin pieces Delrin® can also be found in all-purpose industrial equipment like bearings, gears, pumps, and meters. Acetal’s excellent mechanical properties make it extremely versatile, offering a unique blend of properties that you won’t find in most metals or other plastics. Delrin® plastic is strong, rigid, and resistant to impact, creep, abrasion, friction, and fatigue. It’s also well known for its excellent dimensional stability during high-precision machining. Acetal can also stand up to moisture, gasoline, solvents, and a wide range of other neutral chemicals at room temperature. From a design standpoint, parts made with extruded POM naturally have a glossy surface finish. Since acetal is compatible with CNC machining, injection molding, extrusion, compression molding, rotational casting, and more, product teams are free to choose the manufacturing process that works best for their budget and their needs. However, it’s worth noting that Delrin® plastic is typically very challenging to bond. Acetal material properties vary by formulation, but the mechanical properties for Delrin® 100 NC010, one of the most popular formulations, include: Tensile modulus: 2900 MPa Yield stress: 71 MPa Yield strain: 26% Density: 1420 kg/m3 Charpy notched impact strength, +23°C: 15 kJ/m2 Coefficient of linear thermal expansion, normal: 110 E-6/K Water absorption: 0.9% Delrin® does have a few limitations. For instance, even though Delrin® is resistant to many chemicals and solvents, it’s not very resistant to strong acids, oxidizing agents, or UV radiation. Prolonged exposure to radiation can warp the color and cause the part to lose its strength. Also, this material isn’t readily available in a flame-retardant grade, which limits its utility for certain high-temperature applications. Why choose Delrin® plastic? These limitations notwithstanding, there are many reasons to choose acetal over other materials. When compared to other plastics, acetal offers better creep, impact, and chemical resistance, better dimensional stability, and higher strength. It also has a lower coefficient of friction. Acetal outpaces certain metals as well. Parts built with this material have a higher strength-to-weight ratio, better corrosion resistance, and offer more opportunities for part consolidation. You can build thinner and lighter parts faster and at a lower price point with acetal than with a comparable metal. Delrin® plastic can be found in almost every major manufacturing sector. In the automotive industry, common applications include heavy load-bearing gears, fuel system components, loudspeaker grilles, and safety system components like seatbelt hardware. Delrin® can also be found in all-purpose industrial equipment like bearings, gears, pumps, and meters. In the consumer goods and appliances space, this material can be used to make anything from zippers and pens to knife handles and lawn sprinklers. Getting started with Delrin® There’s a lot for product teams to love about Delrin®. It’s strong, stable, versatile, and its excellent mechanical properties make it a good choice for a wide variety of applications in a number of industries. However, with dozens of different formulations of acetal on the market, it can be very challenging to determine which one might be the best fit for your unique project. A seasoned manufacturing partner can help demystify the material selection process. When you partner with Fast Radius, you partner with a team of on-demand manufacturing experts who have years of experience helping product teams navigate material selection. We’re well-versed in the wide range of materials that can be used for both traditional and additive manufacturing — including Delrin®. Once you’ve selected the Delrin® formulation that’s the right fit for your application, our team of experts can help facilitate the entire manufacturing process — from design and prototyping to production and fulfillment. With a full suite of manufacturing services including CNC machining and injection molding, Fast Radius can bring your vision to life quickly and easily. Contact us today to get started.

Know Your Materials: Delrin (Polyoxymethylene)

PC-ABS

Know Your Materials: Polycarbonate (PC)

CNC

Is Bead Blasting the Right Finish for Your Part?

CNC

How CNC Setups Affect Project Costs

Ready to discuss your next project?

Connect with an expert

We Bring Ideas to Life

  • LinkedIn
  • Facebook
  • Instagram
  • YouTube

Global Headquarters

265 Spring Lake Drive
Itasca, IL 60143 USA

info@sybridge.com

+1 (833) 824-1116

Copyright © 2025 · Return To Top

  • Legal Information
  • EULA
  • Terms and Conditions​
  • Accessibility​
  • Privacy Policy
  • Sustainable Purchases Policy