Ammunition and explosives – Projectiles – Having jacket
Reexamination Certificate
1999-09-08
2001-12-04
Poon, Peter M. (Department: 3643)
Ammunition and explosives
Projectiles
Having jacket
C102S518000, C029S002100
Reexamination Certificate
active
06324985
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the field of metallurgy, and more specifically, to low temperature solid state bonding of tungsten to other metallic materials. In particular, tungsten heavy alloy ballasts are bonded to high strength steel penetrator cases by coating the mating surfaces with copper and silver, and then bonding the interface by hot isostatic pressing at relatively low temperatures.
DESCRIPTION OF THE RELATED ART
It is known in the art to ballast a high strength steel penetrator/warhead with an inner core made of tungsten to improve its performance. The extreme loads that are produced at target impact require that the dense tungsten ballast be bonded to the steel case. In some penetrators of the past, a tungsten heavy alloy ballast, known as WHA, was thermo-shrink fit to the inside of a steel penetrator case to secure the ballast to the case. This type of bonding, however, has drawbacks. One is that the bond strength between the WHA ballast and steel case is insufficient, causing separation of the two on impact with a target. Another drawback is the bond strength varied from unit to unit, leading to unpredictability in testing.
An example of a tungsten penetrator is described in U.S. Pat. No. 4,823,703, which issued to Donaldson. An armor penetrating projectile has a core which can be made of tungsten alloy, and an outer sabot which can be made of steel. The core and sabot can be bonded together by shrink fitting, adhesive bonding, brazing, soldering and the like. The sabot can also be formed directly on the core by metallic deposition, superplastic forming, diffusion bonding or fiber reinforced lay-up with resin.
U.S. Pat. No. 5,253,797, which issued to Ferrando et al., describes a composite gun barrel in which a molybdenum sleeve envelops a steel core. The steel and molybdenum surfaces are bonded together by coating one or both surfaces with molten silver nitrate, and then heating the structure beyond the decomposition temperature of the silver nitrate to form a uniform deposit of silver. The molybdenum and steel surfaces are then brought together and sintered to form a diffusion bond between the silver metal layer, and the molybdenum and steel surfaces.
A continuing need exists for improved methods of bonding steel and tungsten to make a variety of products, such as ballasted steel penetrators.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a ballasted steel penetrator which includes a bond between the tungsten ballast and high strength steel case that is strong enough to survive impact with a target.
Another object of the present invention is to provide a method of making a penetrator which can produce a repeatable, testable, strong bond between a WHA ballast and a steel case.
Still another object of the invention is to provide a method of making a composite article having a steel portion bonded to a tungsten portion, in which the high strength (>200 Ksi tensile) steel portion does not weaken or loose strength during bonding.
Yet another object of the present invention is to provide a method of making a composite article in which a tungsten ballast is bonded to a steel case with the case in the fully heat treated condition.
These and other objects of the invention are met by providing a method of making a penetrator which comprises the steps of forming a tungsten ballast, forming a steel casing with a bore sized to fit the tungsten ballast therein, coating mating surfaces of the tungsten ballast and the steel casing with silver and copper, fitting the tungsten ballast within the bore of the steel casing, and subjecting the tungsten ballast and steel casing to a pressure and temperature sufficient to form a diffusion bond between the tungsten ballast and the steel casing, wherein the bond temperature is below the final tempering temperature of the steel casing.
The foregoing features and advantages of the present invention will be further understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 4241483 (1980-12-01), Voitas
patent: 4823703 (1989-04-01), Donaldson
patent: 5352526 (1994-10-01), Solanki et al.
patent: 5440995 (1995-08-01), Levitt
patent: 5880382 (1999-03-01), Fang et al.
patent: 5988488 (1999-11-01), Slattery et al.
Collins Timothy D.
Lockheed Martin Corporation
Poon Peter M.
Swidler Berlin Shereff & Friedman, LLP
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