Comparison of the Mould Lifetime Between Steel hardened Alloy Drill and Non-Drill
Steel hardened alloys are highly attributed as excellent materials when it comes to providing steadiness and longevity to moulds or similar production tools. During the hardening process, several techniques like tempering, quenching or annealing are used in order to achieve the desired hardness. Although these techniques are very useful in improving wear resistance, good wear performance is largely affected by the properties of the steels and their bulk composition.
In particular, different types of drillings such as pre-drilled or post-drilled holes, may further improve fatigue strength and corrosion resistance. Drillings are used as two paths in different materials, one is the core and the other is the cladding.The first path is necessary to ensure that the steel is strong and stable and the second is used to protect the metal from corrosion or oxidation. In this sense, drilling holes have been reported to enhance fatigue strength of hardened alloys and also improve their anti-corrosion property.
An experiment was carried out to analyze the mould lifetime between steel hardened alloys with drilled and non-drilled. For that purpose, a number of samples composed of 304 stainless steel were tested for the purpose of investigating the influence of the drilled or non-drilled on the hardness or wear resistance of the material. In this regard, six samples were prepared including a forged, a forge post-drilled, a non-drilled, and a pre-drilled sample.
The samples were subjected to a hardness test by using a Rockwell hardness tester, which was operated with a 15 kg load. It was found that the forged sample achieved 91.5 Rc and the forge post-drilled sample showed 91.9 Rc, while the non-drilled sample obtained 91.2 Rc and the pre-drilled sample reached 91.3 Rc.This result indicates that the use of drilling can increase the hardness value, with an increase of 0.7 Rc in the case of the former,while a decrease of 0.3Rc was detected in the latter.
On the other hand, the wear resistance of the samples was evaluated by means of a wear test in which the abrasion of the steel hardened alloys by abrasive materials was compared. The samples were subjected to 10 millioncycles of wear against a sandpaper abrasive material, in which the wear loss increased from forged to pre-drilled samples from 8.51-10.37 mm3 respectively. As a result, despite the hardness results, it can be claimed that for a given set of steel hardened alloys, it is beneficial to opt for a post-drilled moulded sample instead of a pre-drilled one in order to reduce the wear rate.
To evaluate the mould lifetime of the two steel hardened alloys,wear rate was compared with the elapsed time. It was observed that the drill-holes samples resulted in a 6.3 % more significant reduction in the wear rate, compared with the non-drilled samples. This result indicates that drilling holes in the samples can reduce the wear in the die and increase the mould lifetime.
In conclusion, based on the results obtained in this study, it is concluded that steel hardened alloy moulds with drill-holes provide an improved wear resistance and increased mould life. The hardening effect provided by the drillings helps to reduce the wear rate making them more suitable for die casting or forming operations. Thus, mould tool life can be effectively improved by adopting a post-drilled moulded steel hardened alloy.
