Stamping Through Advanced High Strength Steel
Stampers are under continuous pressure to maximize green time and improve productivity. As the use of advanced high-strength steel (AHSS) expands to an ever-growing number of industries, many are finding themselves spending more time in the tool room with dies that are in need of repair and no longer producing. With these new materials boasting superior strength and the potential to reduce part weight by up to 25 percent or more, it’s no surprise that other industries are following suit, adopting AHSS materials in their manufacturing.
Can AHSS Metals Be Too Strong?
AHSS materials are stronger, thinner and more ductile, making them an excellent choice for light-weighting components in industries ranging from aerospace to appliances. At the same time, these qualities are extremely hard on stamping punches and dies, causing tools to wear or break prematurely. This occurs when the higher yield strength and increased tensile strength of the AHSS material being formed or blanked exceeds that of the tool steel used to manufacture tooling. As a result of the increased stress, tools begin to shear, eventually breaking. To overcome this challenge and keep tools in production it is necessary to reconsider the tooling itself and make adjustments to reduce wear and tool breakage. While the solution for each application will be different, some things to consider include the type of tool steel used, the design of the tool itself, and whether or not adding a coating or surface finish will improve performance and provide longer tool life.
Stronger Tool Steel to Combat Stronger AHSS Materials?
Much like the evolution of AHSS, tool steels continue to evolve in their own right to meet the needs of stampers facing increasingly challenging materials and applications. M2, for example, is a conventional high-speed steel with good toughness, wear resistance and high compressive strength. However, if the punch is showing signs of wear, a particle metallurgy high-speed steel with higher carbon and vanadium content, such as PM-M4, provides better wear resistance. For even tougher applications where micro-fracturing is apparent or the punch head breaks altogether, PM-3V tool steel offers a greater level of impact resistance.
How Can I Bolster the Surface of My Tool Steel?
Sometimes making small changes to your tooling is enough to produce big gains in tool life and performance. Something as simple as switching the surface finish from a cylindrical to a straight-line grind, which changes the direction of the surface grain, can reduce stripping pressures and minimize galling. The addition of a surface finish change not only improves wear resistance, but can result in a cleaner, more accurate punch and a higher quality part.
Specialty coatings can boost performance and extend tool life by as much as seven times that of untreated tooling. Determining the best coating for your application will depend on a variety of factors, including: the material being pierced or formed, the presence of material adhesion or galling, whether or not there is fracturing on the cutting edge, the type of lubrication, etc. Fortunately, there are an ever-growing number of coating options, each offering a combination of benefits ranging from greater wear resistance, reduced galling, added lubricity, and increased hardness. Work with your local sales engineer or the Impax staff to determine the best options for your application.
Blend, Balance and a Bolstering Boost
Ultimately, the right mix of tool steel, design, coating and finish will depend on the specific needs of your application. Keep in mind that as our industry continues to adapt and evolve to those we serve, it’s likely that the best solution available today may be surpassed by new technology down the road. Lastly, consider consulting a variety of industry experts, thus gaining a better understanding of the complexities of working with AHSS.
Visit wilsontool.com/stampingsolutions to learn more about tool steel, treatments and surface coatings to enhance your operations.
Want to learn more? Reach out to your local Sales Engineer today!
October 29, 2019