Page 39 - MetalForming January 2017

Many stamping operations involve high-impact, high-heat or high-pres- sure applications, all of which create significant stress on the tooling. For high-impact applications, AlCrN is the ideal choice except when working with aluminum materials. When working in high-heat applications, TiAlN and AlTiN give metalformers exceptionally hard coatings that perform best when working with stainless, high-strength or ultra-high strength steel. As an added benefit of stamping at high sur- face temperatures, aluminum oxide forms on the tool, which enhances coating performance. Here again, stamping aluminum with these coat- ings is not recommended.
Some proprietary coating options from tooling manufacturers are spe- cially designed for high-pressure appli- cations as well as for punching and forming high-strength low-alloy (HSLA) steels. Such coatings deliver full surface quality on polished steels, reduced galling and longer punch wear.
Take Measure of the Material
Different part-design requirements dictate the type of workpiece materi- al—and each type of material comes with its own unique set of challenges. As such, different coatings have a vast array of effects when used for stamping specific materials, and identifying the best coatings for particular materials at the onset of production can help prevent challenges and frustrations down the road.
Many proprietary coating options are designed for aluminum and other soft materials, such as mild and gal- vanized steel, while other coating options for producing aluminum parts ideally are suited for use on materials prone to galling. Additional tool-coat- ing choices when working with alu- minum include TiZrN, which is adept at helping create parts made of other nonferrous materials, such as copper and brass. Coatings that do not enhance production when working with aluminum include AlCrN, TiAlN and AlTiN.
Stainless, high-strength and ultra-
high strength steels normally experi- ence the best results using TiAlN and AlTiN coatings, especially in high-heat applications. When using these types of coatings, an aluminum oxide forms, which helps enhance performance. For HSLA steels, proprietary multilayer nanocoatings perform well under high- pressure applications for punching and forming.
Pick the Proper Tool Steel
The last piece of the puzzle is deter- mining the best tool steel for the job. When considering the application, materials, tool steel and the advantages and limitations of each, adding the coating is like the icing on the cake. It’s the added benefit that allows the tool to outperform and out-produce an uncoated tool in a similar setup.
M2 tool steels provide good results for virtually any type of part material. Best used in cases of high-compression, M2 delivers wear resistance and tough- ness in essentially any application. If the job requires a higher level of tough- ness, wear resistance and compression strength, PM-M4 tool steel is the answer, which also performs well on any type of part material.
Also, 10V tool steel helps increase tool life and, much like M2 and PM- M4, delivers sound results on most any
part material. For high-impact and wear-resistance applications, or if met- alformers experience chipping and breakage, 3V or proprietary tool steels offer desirable options. 3V is specifically beneficial when working with stainless, HSLA or spring steel, and is designed for applications that require piercing material with thicknesses that are sim- ilar to the hole diameter.
Confront Challenges
With all of this information, finding the right combination of tool steels and coatings for various applications and materials still can prove challeng- ing. Variables such as material grade and other causes for tool failure often work into the scenario.
The best solution when trouble- shooting? Conduct research and ask questions. Many tooling manufactur- ers, through trial and error when devel- oping coatings, have helped metal- formers determine and incorporate solutions that help reduce downtime, experience longer tool life and produce higher-quality parts. As applications become tougher and materials stronger, tooling manufacturers will continue to develop new tool-steel and coating combinations to help stampers advance operations and improve efficiencies.
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