5 Ways to Improve Die Performance

While selecting a die casting, designers generally think that tooling is not reliable or that short die life will affect production. Research & developments over the last decade, however, have proved that a variety of methods are available that can be used to improve die life, enhance the performance of die and reduce the overall cost-per-part.

The 5 key factors, which can extend die life are -

• Die Design
• Die Material
• Heat Treatment
• Coatings
• Operation / Maintenance

These factors can be adjusted and modified as per the requirement to improve the die performance anywhere from 50 % to nearly 100 %. This is a significant improvement in performance that typically outsets any further increase in cost for producing superior-quality, long-lasting tooling, making it a better choice than cheaper low quality tooling.

Judging Die Performance
In general, improved die performance results in more parts at a lesser cost. The 3 factors, which affect the tooling and limit the die performance are -

• Soldering and chemical attack between the die material and liquid metal.
• Wear & erosion.
• Heat checking or thermal fatigue occurring as a result of the thermal cycling, which takes place with each shot or casting cycle.

These factors can be eliminated or reduced to improve the die performance and reduce the overall costs.

Performance Improvement Ways -
The 5 key factors given here for the improvement of die performance are a beginning point for determining what combination of elements will have the highest impact on performance in a specific situation. As like there are several nuances within each performance improvement element, the particular steps, which will produce the best results will depend upon various factors, such as the die casting type (hot or cold chamber), the cast alloy, size of shot, or the wall of casting (thin wall or thick wall).

Die Design
For the improvement of tool life, the parts should always be designed with round edges or generous radii. Gate location is also a critical factor, as the control of metal flow in die cavity is a major factor in producing sound die castings. The metal must necessarily flow quickly and uniformly into the die, as it minimizes the sharp direction changes, which can result in premature tool wear.

Die Material
For majority of tool construction, casters generally prefer superior grade H13 tool steel as the starting point. However, many die casters nowadays, are realizing that the die life can be significantly improved by using modified versions of H11 steel, heat treated to a hardness level of 48 HRC. H11 has greater molybdenum content, with lower vanadium and silicon, facilitating greater toughness than H13, superior temper resistance, which improves the die life in demanding applications, such as - thick-walled castings.

Heat Treatment
Research have proved that heat treatment process is as critical in impacting the die life as the selection of the proper die steel. The thermal fatigue cracking can be greatly reduced by using an austenitizing temperature, which will place the optimum amount of carbide forming elements in solid solution in the austenite. When combined with a speedy quench rate, the toughness remains unaffected.

Coatings
Coating and/or surface treatment helps in improving the tool life by preventing the soldering and erosion between the tool steel and the liquid alloy being cast. Though surface modification techniques like ferritic nitrocarburizing and plasma ion nitriding also improve the die life, coatings generally provide better improvement.

Operations/Maintenance
As good design is the starting point in ensuring the long die life, proper operation and maintenance are critical to the overall success in improving the die performance. These include the die set up procedure, pre-heating tools and verifying clamping pressures. In case, a hard coating has been applied, the cleaning pressure needs to be changed to avoid damaging the coating.