1. EXPLOSIVE WELDING USING THE EMULSION EXPLOSIVES
Victor V. Silvestrov
A.V. Plastinin, S.I. Rafeichik, M.A. Gulevitch, and V.V. Pai
D = 1.9 km/sec
Lavrentyev Institute of Hydrodynamics
Siberian Branch of Russian Academy of Sciences Novosibirsk, Russia
X International Symposium on Explosive Production of New Materials: Science, Technology, Business, and Innovations (EPNM-2010)
June 7 – 11, 2010, Bechichi, Montenegro

2. Goals
The decrease of the velocity of detonation (VOD) to 2‒3.5 km/sec for the emulsion explosives
The application of the compositions for explosive welding of metals

3. Outline
Emulsion Explosives with detonation velocity km/sec and high detonation ability
VOD vs charge diameter. Detonation limits
Shell-life. Effect of casing
Particle velocity – time profile, detonation pressure
Throwing ability of low VOD emulsion explosives
Examples of explosive welding applications
Cladding of metals by foils with thickness up to 100 microns (without buffer layer)
Explosive welding of small diameter tube with tubeplate model (the thermal welding to pressurize the tube/tubeplate connection is not needed)

4. History of low VOD emulsion explosives
Yoshida, M., Iida, M., et al., 8th Symp. Intern. on Detonation, 1985: dcr < 6 mm, Δcr < 1 mm in wedge test for handmade emulsion explosives
Matsuzawa, T., Murakado, T., et al., “Method for explosive cladding” US Patent , : D = 2-5 km/sec, but the details and detonation limits were not discussed
Petel, O.E., Mack, D., et al., 13th Symp. Intern. on Detonation, 2006: D ≥ 3 km/sec, dcr ≈ 13 mm, Δcr = 3.3 mm in PMMA casing for commercial explosives
There are only the scanty information for
the low detonation velocity emulsion explosives

5. Main Ideas
Use of fine emulsion matrix to increase of detonation ability of explosives
Introduction of large amount of light hollow glass microballoons (GMB) into the emulsion matrix to decrease the explosive density and the detonation velocity

6. Compositions Components, wt. % EmExp–8 EmExp–50 Ammonium Nitrate67
Sodium Nitrate 14
Water 12
Paraffin, solid 3
Industrial Oil 2
Sorbitan monooleate
Sensitizer (GMB), μ 8 50
Explosive Density, g/cc
1.0
0.5
Maximal VOD, km/sec
4.76
2.1
Minimal VOD, km/sec
2.67
1.8
Critical diameter / thickness, mm
4.8 / 2
13 / 12
μ = GMB weight / Emulsion matrix weight

7. Fine Emulsion Optical picture High detonation ability
Between marks 12 μm
The size of oxidizer droplets is lower 1-2 μm
Non-Newtonian elastoplastic fluid,
Apparent viscosity 30–40 kP at 60°C
High detonation ability

8. Domestic Glass Microballoons
1 – optical analysis, 3 – 3M Belgium, 2 – sieve analysis
d, μm
58 μm
ρ00 = 0.15 g/cc
Trade mark MS-V

9. Synchrotron Radiation-Aided Tomography
Like as “Honeycombs of wild bees”
3D structure
1 mm
A small morsel of emulsion explosive at μ = 8 %
According to Pruell Ed.R., Ten K.A. (2009, LIH)

10. «Explosive Welding» area
Effect of GMB quantity
Ø 30 mm
US Patent
0.75  0.5 g/cc
Ø 20 mm
Our data
«Explosive Welding» area
μ = 20  50 wt.% GMB, D = 2  3.5 km/sec

11. Steady-State Detonation
8 %
50 %
20 %
μ is increasing
GMB, wt. %:
1 – 8
2 – 20
3 – 25
4 – 35
5 – 50
6 – 50 in casing
Weak dependence of detonation velocity on charge diameter at μ ≥ 20 %
Only one explosive component is ammonium nitrate → high safety of blasting

12. Detonation Limits
dcr
dcr/Dcr
1 – Di
2 – Dcr
3 – Dcr
4 – dcr

13. dcr. w/o case/ dcr. metal case≈ 7-8 as for individual HE’s
Effect of Casing
D, km/sec
μ = 50 %
12.4 mm
1.7 mm
Thin PE case, 12.4 mm
PTFE, 6.2 mm
Duralumin, 1.7 mm
Steel, 1.5 mm
for emulsion matrix
Sound velocity
L/d = 12 – 30
Cylindrical charge diameter, mm
dcr. w/o case/ dcr. metal case≈ 7-8 as for individual HE’s

14. Shell-Life of low VOD emulsions
industrial oil () and solid paraffin (▲)
Shell-life is larger than one month
16 mm

15. Particle velocity - time profiles
Original free-contact electromagnetic method
(Pai V.V. et al, 1998) was used
80 mm, 230 mm (L)
GMB, wt. %:
1 – 8
2 – 20
3 – 35
4 – 50
Chemical spike predicted by ZND theory = YES except for curve (4)

16. Estimations of Detonation Parameters
ρ0,
g/cc
UD, km/sec
PD,
GPa
tR, μs
aR, mm n
1.04
1.08
5.1
0.4
1.3
3.2
0.75
0.86
2.0
0.9
2.6
0.63
0.6
0.8
2.9
0.5
0.77 ‒
1.5
U7[p.l; [;\=\\\\
Particle velocity, UD ~ 1.1 km/sec
Reaction zone width, aR ~ 1 mm
Detonation pressure, PD 0.7 ~ 5.1 GPa
Detonation product’s index, n ~ 3.2
Reaction time, tR ~ 0.8 μsec
Detonation energy, Q ~ 1.4 kJ/g
Q = D2/(2(n2-1))

17. Acceleration of Plate by Sliding Detonation
To study the throwing ability of emulsion explosives it was determinate
the 2D X-Y profile of test copper plate (inclined resistive wire method)
1 – Nichrome wire 40 μm
2 – copper plate 1 mm
3 – plane layer of explosive
4 – pins
5 – detonation front

18. Comparisons of 2D Experimental and Computed Plate Profiles
Experimental profiles
P ~ ρn
Hydrodynamic approximation
2D numerical calculations
with n - target values
n value
Bend angle
Plate velocity
Solid curves – experiments, markers – 2D calculations

19. n - index of Detonation Products
(a) 1 – cylindrical and 2 – flat charges
(b) μ = 8 (3), 20 (4), 50 (5) wt. %
For developed emulsion explosives n – index depends on the initial density and on the thickness of flat layer of explosives

20. Results of lateral acceleration
The plate velocities are ranged from 0.5 up to 1.3 km/sec, and the bend angles from 10 to 27 degrees.
These collision values are close to the necessary ones to explosive welding of metals.

21. Explosives Cladding by foils
Clad layers: foils μm – aluminum, titanium, stainless steel, bronze, nickel, copper, molybdenum
Emulsion explosives: 2-3 or 6-12 mm (T), 50 mm (W), up to 300 mm (L)
Base plate: copper, mild steel
Bronze 0.29 mm/steel 10 mm, Expl = 3.4 mm
After shot
Without shock buffer layer between explosives and foil

22. Emulsion Explosives Cladding by Foils
exp = 3 mm
Al 0.2 mm / Copper
exp = 2 mm
0.1 mm
exp = 2.7 mm
Cu 0.2 mm / Steel
0.2 mm
100 
Ni 0.3 mm / Steel
1 mm
exp = 3 mm
exp = 12 mm
Ti 100 μm / stainless steel
Mo 200 μm / steel
Cu 1 mm / steel
 ≈ m, a/ ≈
VC = 2.0 – 3 km/sec, Δexp = 2 – 12 mm

23. Explosive Welding Tube to Collar
pressing-out, r = 0.27
air gap
welding, r = 0.32
Ø11 мм
section of the connection zone
wavy seam
model of tubeplate is the mild steel sleeve
stainless steel tube, Ø12.5/11 mm
explosive cartridge: < 11 mm in diameter, D ≈ 3 km/s, 0.75 g/cc
The thermal welding to pressurize the tube/sleeve connection is not needed

24. Results
Emulsion explosives with a detonation velocity of 2–3.5 km/sec, detonation pressure of GPa and high detonation ability are developed
Emulsion explosive based on fine emulsion has a very small critical diameter if the charge is enclosed to strong casing
Two applications of the low velocity detonation emulsion explosives for explosive welding are tested:
cladding of metals by foils up to 0.1 mm in thick
welding of small diameter tubes to a tube collar

25. Thank You for Attention
Acknowledgments
The work was supported by the RFBR (grant # a), by the Siberian Branch of RAS (project 2.10), and partially by the Grant of President of the Russian Federation (project NSh )
Thank You for Attention

26. X-ray picture of detonating charge
Cylindrical charge 20 mm in diameter, 0.5 g/cc,
Detonation pressure GPa
D = 1.9 km/sec
Detonation front
tR < 0.5 μsec, aR < 1 mm
Bend angle of casing (PE 0.7 mm + 30 μm Lead)  35 º

27. Optical Fiber Technique for VOD measuring at d<4 mm
Pins
L/d = 20 – 35
Detonation cord
3 fibers
Contact / ion pins
Optical fibers