Investigation on the Use of PETN Based Sheet Explosive in Hardening and Welding

Abstract

In explosive hardening and welding processes, one of the essential requirements is the preservation of the surface integrity of participant materials, for this the velocity of detonation (VoD) is kept low. For explosive hardening process, standard sheet explosives are used and for explosive welding process various types of powder explosives are widely used. Nevertheless, these types of powder explosives have limitations viz., difficulties in mixing and handling; cannot maintain uniform thickness along the large surface, large critical thickness, variation in VoD with thickness of explosives. To overcome the problems of conventional sheet explosive and powder explosives, a novel PETN based slurry casted explosives is developed which consists of PETN explosive mixed with inert additives, plastic binder and plasticizer. This slurry casted explosive has uniform density and thickness and easy to prepare and handle. The VoD can be maintained as desired in the range of 2000 m/s to 6000 m/s by varying the ratio. This chemical mixture was used for surface hardening of mild steel, and high manganese steel plates. Post hardening, it is observed that the plates were not damaged and their dimensional and material integrity remained unchanged. In explosive welding process slurry casted PETN based sheet explosive with low VoD was developed by mixing it with inert additives and used for explosive bonding of Aluminum to Stainless Steel, Copper to Stainless Steel. The VoD of the explosive was measured, and it detonated successfully during the trials. Since PETN has very small critical diameter, sheets can be made as small as 2 mm thickness with reliable and stable detonation. It is concluded that most of the problems of powder explosives can be surmounted by using high explosive based slurry casted sheet explosive. With these preliminary investigations, future work will be carried out to fully optimize and establish this new process for explosive hardening and welding.