GB1585082A - Method of treatment of cast high explosives - Google Patents

Description

(54) METHOD OF TREATMENT OF CAST HIGH EXPLOSIVES (71) We, MEssERscHMITT-BoLKow- BLOHM GESELLSCHAFT MIT BESCHRANKTER HAFTUNG, of 8000 Munchen, German Federal Republic, a company organised and existing under the laws of the German Federal Republic do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement :: This invention relates to a method of treating cast high explosives which are prepared from a high proportion of at least one unmelted (solid) high expolsive substance, particularly hexogen, in various grain sizes, and a smaller proportion of at least one melted explosive substance, particularly TNT, both constituents being heated and suspended and poured into a mould, or into a warhead casing directly. The solid explosive constituent is possibly compressed and the suspension subjected to pressure, after which the solid and the melted explosive constituent are cooled to room temperature, preferably in a number of stages.

Reference is made to our copending application No. 4434/76, Serial No. 1585083) According to this invention there is provided a method of treating cast high explosives which are prepared from a high proportion of at least one unmelted (solid) high explosive substance in various grain sizes, and a smaller proportion of at least one melted explosive substance, both explosive substances being heated and suspended and then poured into a mould immediately, after which the solid and the melted explosive constituent are cooled to room temperature in which method the explosive mass, after solidification in the mould by part or complete cooling to room temperature, is again heated to a temperature just below the melting point of the explosive substance melted during the production stage, this treatment temperature being held for a time, after which the explosive is again cooled to room temperature slowly to avoid cracking. This cooling may be carried out in stages, in order to avoid internal stresses.

After solidification of the melt, therefore, the treatment of the explosive moulded body according to the invention, can be carried out either while the cooling process is still in progress, so that the method of treatment according to the invention is integrated in the entire production process, or else after the moulded body has cooled down to room temperature, thus constituting a form of after-treatment by which is meant the treatment immediately following the cooling. The completely assembled warhead together with the charge can also undergo an after-tratment of this kind some time after assembly, possibley even years thereafter and also repeatedly.

The following operations and times for the after-treatment according to the invention have been found preferable in the case of a warhead of calibre about 100mm and a charge comprising hexogen and TNT.

The explosive body is re-heated from room temperature to 72 to 780C, preferably 75 0C, and this heating period is 5 to 7 hours, preferably 6 hours, the constant treatment temperature is maintained for 4 to 6 hours, preferably for 5 hours, the cooling period being 12 to 14 hours, preferably 13 hours.

By this treatment method the following effects are obtained: As the explosive when heated to the plastic state of the TNT expands to a far greater extent than the warhead casing, the explosive mass is subjected to such a high pressure, due to the rigidly of the warhead, that any existing cracks disappear due to the coalescence of TNT.

Furthermore the internal stresses caused by the deliberate very slow cooling of the explosive are largely avoided thus reducing the sensitivity to cracking as a whole. The melting point of TNT may be exceeded at certain points, owing to the occurrence of very high local pressures, especially in the peripheral zone of the charge, which is also where most cracks occur. During the subsequent slow cooling process, elongated TNT crystals then occur, particularly in the parts subject to the danger of cracking and by reason of the firm adhesion to the adjacent hexogen grains are insensitive to further cracking during subsequent extremes of temperature.

Furthermore, in the process of heat treatment of heat treatment according to the invention, the following occurs which is of decisive importance for the improvement of quality.

Tests have shown that the TNT present in the spaces between the hexogen grains is at least partly sublimed during the heating process and distributes itself in a gaseous state within the charge more satisfactorily than in the actual production (casting), thus the TNT undergoes a practically even distribution, so that the homogeneity of the charge is again further increased. This improves the efficiency of the charge producing an even detonation wave front and satisfactory formation of a spike from a conical liner of a hollow charge. In addition, the mechanical strength of the charge proves to be increased by about 10%.

Octogen can be used in place of hexogen and trinitrobenzene in place of TNT.

WHAT WE CLAIM IS: 1. A method of treating cast high explosives which are prepared from a high proportion of at least one unmelted (solid) high explosive substance in various grain sizes, and a smaller proportion of at least one melted explosive substance, both explosive substances being heated and suspended and then poured into a mould immediately, after which the solid and the melted explosive constituent are cooled to room temperature, in which method the explosive mass, after solidification in the mould by part or complete cooling to room temperature, is again heated to a temperature just below the melting point of the explosive substance melted during the production stage, this treatment temperature being held for a time, after which the explosive is again cooled to room temperature slowly to avoid cracking.

2. A method in accordance with claim 1, wherein the explosive mass is of hexogen and TNT and has a calibre of about 100 mm, the mass being reheated from room temperature to 72 to 78 C, preferably 750C, during a period of 5 to 7 hours, preferably 6 hours, the aforementioned temperature being maintained constant for 4 to 6 hours, preferably 5 hours, the cooling period lasting for 12 to 14 hours, preferably 13 hours, and preferably being carried out in stages.

3. A method in accordance with any preceding claim carried out substantially as herein described.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. partly sublimed during the heating process and distributes itself in a gaseous state within the charge more satisfactorily than in the actual production (casting), thus the TNT undergoes a practically even distribution, so that the homogeneity of the charge is again further increased. This improves the efficiency of the charge producing an even detonation wave front and satisfactory formation of a spike from a conical liner of a hollow charge. In addition, the mechanical strength of the charge proves to be increased by about 10%. Octogen can be used in place of hexogen and trinitrobenzene in place of TNT. WHAT WE CLAIM IS:

1. A method of treating cast high explosives which are prepared from a high proportion of at least one unmelted (solid) high explosive substance in various grain sizes, and a smaller proportion of at least one melted explosive substance, both explosive substances being heated and suspended and then poured into a mould immediately, after which the solid and the melted explosive constituent are cooled to room temperature, in which method the explosive mass, after solidification in the mould by part or complete cooling to room temperature, is again heated to a temperature just below the melting point of the explosive substance melted during the production stage, this treatment temperature being held for a time, after which the explosive is again cooled to room temperature slowly to avoid cracking.

2. A method in accordance with claim 1, wherein the explosive mass is of hexogen and TNT and has a calibre of about 100 mm, the mass being reheated from room temperature to 72 to 78 C, preferably 750C, during a period of 5 to 7 hours, preferably 6 hours, the aforementioned temperature being maintained constant for 4 to 6 hours, preferably 5 hours, the cooling period lasting for 12 to 14 hours, preferably 13 hours, and preferably being carried out in stages.

3. A method in accordance with any preceding claim carried out substantially as herein described.