Stamping dies comprise the principle equipment used in the metal forming process. They are used to press sheet metal into a desired shape and size. The quality of the stamping die directly affects the quality of the product. To improve the wear and tear resistance of the stamping die, certain measures must be taken.
Stamping dies are made from a steel alloy. However, high-volume production runs can wear out the
die rapidly, which leads to increased costs because of replacement and down-time. Thankfully, there are ways to extend the useful life of stamping dies, such as hardening, and other methods to improve wear and tear resistance for stamping dies. Extending the life of stamping dies offers the following benefits.
- Reduced Costs
Extending the life of the die lowers overalloperating costsbecause the need to replace the occurs with less frequency. This brings about the added cost-saving benefit of reduced down-time.
- Fewer Defects
Stamping diesthat resist wear and tear also produce components with fewer defects.
- Improved Consistency
By increasing the lifeof the stamping die, fewer inconsistencies appear in the stamped parts, because the stamping pressure can change slightly each time you use the stamp. Taking steps to extend the die’s useful life minimizesthis issue, which leads to more consistent results.
The following eight hardening tips will help you improve their wear and tear resistance of your stamping dies.
Die Heat Treatment
Stamping dies need to be heat-treated to stay sharp and resistant to wear and tear. Heat treating at temperatures of 500 to 600 degrees Celsius will create martensite, a very hard form of steel crystalline structure, within the steel alloy. The tiny crystals formed in this process have strong anti-corrosion properties, prevent rust formation and increasing hardness. For this process to work well, you must use water vaporizing equipment to quench the stamping die in oil. If this step is skipped, it will decrease the wear and tear resistance of the stamping die.
Hard Enamel Coating
Applying a hard enamel coating on the surface of the die will mask any pores and pits on its surface, giving it a smooth, shiny appearance. This makes it harder for materials to stick to the surface of the die when they’re stamped and eases pitting issues.
The hard enamel coating can be applied in 2 different ways, 1) through mechanical spray coating or 2) chemical vapor deposition (CVD). Mechanical spray coating is the less costly method, but the downside is the number of times the coating can be reapplied to the die is limited. CVD is the better option because it doesn’t have this limitation. However, CVD costs significantly more than mechanical spray coating.
Vapor Deposition Method
Metal is heated in a vacuum until it reaches a gaseous state. This vapor coats the surface of steel alloy. This reduces wear because components will not stick to the surface of the die after this process. The coating also protects against rust.
This method is less expensive than the CVD option, but more costly than the mechanical spray option. Your choice depends on your application’s requirements. For example, if only a few dies are used in the stamping process, CVD might not be considered.
Wear Resistance Coating
Wear resistance coatings are applied over hard enamel coatings, so all parts of the die’s surface have been covered. Wear resistant coatings extend the life of steel alloy dies and can improve massively its performance. Moreover, less pressure is required to stamp the component because parts don’t stick to the die’s surface. This leads to fewer defects, increased efficiency, and reduced costs. It also makes the entire process more reliable and consistent.
This is a less expensive option than the other methods mentioned previously. However, it doesn’t last as long, and needs to be reapplied frequently. That said, it is better than not using any protection against wear and tear.
Carburizing, also known as surface hardening, case hardening or carburization, increases the carbon content of the alloy, which increases surface hardness. There are various methods, such as gas carburizing or liquid carburizing, all of which have benefits and drawbacks.
Gas carburizing is the less expensive option, doesn’t require specialized equipment, and can be done in most shops. The downsides are that it can only be used on small dies and takes longer to complete.
Liquid carburizing is the more expensive option, but it can be used on any size die and is a quicker procedure than gas carburizing.
Nitriding is a heat treating process that diffuses nitrogen into the surface of a metal to create a case-hardened surface. This process is most commonly used on low-alloy steels. It can also be used on titanium, aluminum, and molybdenum. Nitriding is a heat treatment often used for stamping dies to increase their resistance to wear and tear. The nitriding process involves heating the steel alloy to a point that the nitrogen gas reacts with the metal forming a layer of nitride on its surface. This layer increases wear and tear resistance, which can be beneficial if the stamping dies are to be used in a humid or corrosive environment.
The downside to nitriding is it can only be applied once and takes a long time to complete, making it unsuitable for some applications. The process is expensive, so it’s not the best option for many situations.
Ceramic coatings are often used on stamping dies to protect them from wear and tear. The coatings are made from various materials, such as silicon carbide, aluminum oxide, and titanium nitride, all of which have benefits and drawbacks.
Silicon carbide is the most common type of ceramic coating because it has very high wear resistance. However, it lacks corrosion resistance, making it unsuitable for humid environments.
Although aluminum oxide is less wear-resistant than silicon carbide, it is more corrosionresistant. It is a great choice for applications in which stamping dies are used in humid environments. It’s also less expensive than silicon carbide.
Titanium nitride is the most corrosion-resistant of all the ceramic coatings, but it’s also the least wear-resistant. It is best used as a coating for dies designed to produce small parts.
Thermal spray deposit a layer of material onto the surface of stamping dies to protect them from wear and tear. They incorporate various materials such as metals, ceramics, or plastics, each material having its own benefit or drawback.
Metals are commonly used in thermal spray coatings because they offer high wear resistance. However, they are the most expensive option and can be challenging to apply.
Ceramics are less expensive than metals and have a higher wear resistance than plastics, but they are not as tough as metals.
Plastics, the cheapest option, are also the least wear resistant.
Using a quality lubricant can mitigate wear and tear on stamping dies. Lubricants work by reducing the friction between the surfaces of the die and the workpiece, which, in turn, reduces the amount of wear and tear caused.
There are many lubricant available, each with benefits and drawbacks. Common types include oil-based lubricants, water-based lubricants, and dry film lubricants.
Oil-based lubricants are the most common and have a high viscosity, making them very effective at reducing friction. However, they can be messy to use and may also cause corrosion of the die depending on the metal of which it is made.
Water-based lubricants are not as messy as oil-based lubricants, but they don’t last as long and need to be reapplied frequently. Dry film lubricants are also messy, and must be reapplied more often, but they last longer, so there’s less downtime while the stamping dies are being lubricated.
No matter the process, stamping dies must be in good condition. Corrosion can cause them to crack or shatter, putting a permanent end to their usefulness. Therefore, they must be thoroughly cleaned and protected at all times, but this isn’t always enough. The best way to ensure that the stamping dies will continue working for as long as possible is by treating them with one of the various coatings that we discussed above.