Fragmentation device with increased surface hardness and a method of producing the same

Patent metadata

Field	Value
Publication number	US-9738947-B1
Application number	US-201514689696-A
Country	US
Kind code	B1
Filing date	Apr 17, 2015
Priority date	Apr 18, 2014
Publication date	Aug 22, 2017
Grant date	Aug 22, 2017

Abstract

A method of modifying material properties of a fragmentation device, includes providing a fragmentation device with a first surface, a first section, a second section, a second surface spaced apart from the first surface, a third section, and a fourth section disposed between the first, second, and third sections. The method further includes positioning the fragmentation device within a carbon-rich environment, and absorbing carbon from the carbon-rich environment into the first and second surfaces of the fragmentation device. Additionally, the method further includes increasing a content of carbon at the first and second surfaces of 0.06 wt. % carbon to 1.0 wt. % carbon and maintaining an original content of carbon of 0.01 wt. % carbon to 0.05 wt. % carbon at the fourth section of the fragmentation device by controlling penetration of the carbon into the fourth section.

First claim

What is claimed:

1. A method of modifying material properties of a fragmentation device, comprising:
providing a fragmentation device with a first surface, a first section extending from the first surface, a second section disposed on at least one side of the first section and extending from the first surface, a second surface spaced apart from the first surface, a third section extending from the second surface, and a fourth section disposed between the first, second, and third sections, the first section of the fragmentation device having a first thickness and the second section of the fragmentation device having a second thickness less than the first thickness, and an area of the first surface being greater than an area of the second surface;
positioning the fragmentation device within a carbon-rich environment;
increasing the temperature within the carbon-rich environment up to 1,200° C.;
absorbing carbon from the carbon-rich environment into the first and second surfaces of the fragmentation device;
increasing a content of carbon at the first and second surfaces to 0.06 wt. % carbon to 1.0 wt. % carbon; and
maintaining an original content of carbon at 0.01 wt. % carbon to 0.05 wt. % carbon at the fourth section of the fragmentation device by controlling penetration of the carbon into the fourth section.

2. The method of claim 1 , further comprising absorbing the carbon to a first depth with the first section and absorbing the carbon to a second depth within the second section, the first depth being less than the second depth relative to the first surface, and the first and second depths being less than a depth of the fourth section relative to the first surface.

3. The method of claim 1 , wherein the first thickness is 0.5-1.0 inches and the second thickness is 0.45-0.99 inches relative to the first surface.

4. The method of claim 1 , wherein increasing the content of carbon at the first and second surfaces includes increasing a hardness of the first and second surfaces to 50-70 Rockwell C.

5. The method of claim 1 , wherein maintaining the original content of carbon at the fourth section includes maintaining a hardness of the third section at 10-50 Rockwell C.

6. A method of manufacturing a fragmentation device, comprising:
selecting a material for a fragmentation device, the material including a first surface, a second surface generally opposite the first surface, and an intermediate section disposed between the first and second surfaces, an area of the first surface being greater than an area of the second surface;
forming a plurality of first sections and a plurality of second sections extending from the first surface, each of the second sections being disposed along at least one side of each of the first sections, and a thickness of the first sections being greater than a thickness of the second sections;
forming the material into a shape defining the fragmentation device;
increasing a carbon content of the first and second surfaces of the material;
maintaining a carbon content of the intermediate section by controlling penetration of carbon into the intermediate section; and
positioning an energetic device within the fragmentation device.

7. The method of claim 6 , wherein a hardness of the first and second surfaces of the material is generally equal.

8. The method of claim 6 , wherein a hardness of the intermediate section of the material is less than the hardness of the first and second surfaces.

9. The method of claim 6 , wherein increasing the carbon content of the first and second surfaces includes positioning the material within a carbon-rich environment.

10. The method of claim 9 , wherein increasing the carbon content of the first and second surfaces includes elevating the temperature of the carbon-rich environment to a temperature configured to form a martensitic phase within the first surface of the material.

11. The method of claim 10 , wherein the temperature of the carbon-rich environment is up to 1,200° C.

12. The method of claim 6 , wherein the thickness of the first sections is 0.5-1.0 inches and the thickness of the second sections is 0.45-0.99 inches relative to the first surface.

13. The method of claim 6 , further comprising absorbing carbon to a first depth with the first section and absorbing the carbon to a second depth within the second section, the first depth being less than the second depth relative to the first surface, and the first and second depths being less than a depth of the intermediate section relative to the first surface.

14. A fragmentation device, comprising:
a fragmentation structure with a first surface, a first section extending inwardly from the first surface, a second section disposed on at least one side of the first section and extending inwardly from the first surface, a second surface spaced apart from the first surface, a third section extending from the second surface, and a fourth section disposed between the first, second, and third sections, the first section of the fragmentation structure having a first thickness and the second section of the fragmentation structure having a second thickness less than the first thickness, a carbon content of the first and second sections being greater than a carbon content of the fourth section, and an area of the first surface being greater than an area of the second surface; and
an energetic device positioned within the fragmentation structure.

15. The fragmentation device of claim 14 , wherein the thickness of the first sections is 0.5-1.0 inches and the thickness of the second sections is 0.45-0.99 inches relative to the first surface.

16. The fragmentation device of claim 14 , wherein the first surface has a first hardness of 50-70 Rockwell C.

17. The fragmentation device of claim 16 , wherein the second surface has a second hardness of 50-70 Rockwell C.

18. The fragmentation device of claim 17 , wherein the fourth section of the fragmentation structure has a third hardness of 10-50 Rockwell C.

19. The fragmentation device of claim 14 , wherein the second section of the first surface has a tapered configuration with a narrowing width extending inwardly from the first surface.

Assignees

• Us Navy

Inventors

• Deshpande Nishkamraj U
• Scheid Eric
• Schwabe James E

Classifications

• C21D2211/008

  Martensite · CPC title

• C23C8/22

  of ferrous surfaces · CPC title

• F42B12/24

  with grooves, recesses or other wall weakenings {(F42B12/26, F42B12/28 take precedence)} · CPC title

• C21D9/16 Primary

  for explosive shells · CPC title

• C21D1/06

  Surface hardening · CPC title