Coek Engineering NV - 1 -

Julien Laermans Patrick Van Roy Commercial Manager Man. Director Covalim COEK Engineering Sales Group Coek Liessel 13 Liessel 13 2440 Geel 2440 Geel Belgium Belgium Phone: +32 14 56 42 15 Phone:+32 14 56 42 18 FAX: +32 14 58 27 89 Fax:+32 14 58 27 89 julien.laermans@coek.be patrick.van.roy@coek.be

Index: ABSTRACT ……………………………………………………………… 2. KEYWORDS ……………………………………………………………… 2. INTRODUCTION ……………………………………………………………… 2. TYPICAL EQUIPMENT REQUIREMENTS ……………………………… 3. CLAD SUPPLY ……………………………………………………………… 6. VESSEL CONSTRUCTION DESIGN ISSUES ……………………… 6. VESSEL FABRICATION ISSUES ……………………………………… 8. Strip back ……………………………………………………………… 8. Nozzle construction ……………………………………………………… 9. Head manufacture ……………………………………………………… 10. Heat treatment ……………………………………………………… 11. Titanium clad restoration ……………………………………………… 11. Internal components ……………………………………………………… 11. Titanium Weld Inspection ……………………………………………… 12. Vessel testing ……………………………………………………………… 12. Finishing ……………………………………………………………… 12. Transit ……………………………………………………………… 13. EQUIPMENT PERFORMANCE ……………………………………………… 13. CONCLUSIONS ……………………………………………………………… 13. REFERENCES ……………………………………………………………… 14.

Large Titanium Clad Pressure Vessels Design, Manufacture, and Fabrication Issues

March 2006

Coek Engineering NV - 2 -

ABSTRACT There is an increasing demand for large, high pressure, titanium-steel clad pressure vessels. Many of these vessels are reactors and columns used in PTA manufacture and autoclaves used in pressure acid leaching of metal ores. Currently titanium clad vessels are being manufactured in various size combinations up to 10 m diameter, 75 m long, and 130 mm wall thickness. Operating conditions range up to 275°C and 70 bar. The large, heavy clad components present unique issues for manufacturing, forming, and fabrication. The high operating temperatures and pressures present unique design considerations to accommodate the thermal expansion mismatch between titanium and steel. Significant developments in manufacturing techniques, both cladding and fabrication, have made manufacture of this equipment viable. Welding design, technique and procedures have been developed to reduce cost and improve reliability. Inspection methods and techniques have been developed to assure equipment quality. Issues related to design and manufacture and the resulting equipment benefits are presented.

KEYWORDS

titanium, clad, reactor, column, autoclave, pressure vessel, fabrication, terephthalic acid, pressure acid leaching, and explosion cladding.

INTRODUCTION

Titanium’s superior corrosion resistance is ideal for many process applications (Ref 1). Process industries choose titanium as the material of construction for piping, tanks, pressure vessels, columns, autoclaves, and heat exchangers. When pressures and/or temperatures and size demand very thick plate, the titanium equipment can become considerably more expensive than units constructed from lower cost, lower performance materials. Titanium clad steel offers a reliable, cost effective alternative, providing durable titanium lined equipment which is lower cost than many less reliable alternatives. Titanium clad steel pressure vessels, constructed using explosion welded clad plates, have been in service since the 1960’s. Over this period, the requirements for vessel size, operating

Coek Engineering NV - 3 -

temperature, and operating pressure have continually increased. Techniques of clad manufacture, forming and fabrication have evolved to support these needs.

TYPICAL EQUIPMENT REQUIREMENTS The demand for titanium clad is dominated by equipment for manufacture of two highly different products, polyester and nickel. Both have the common need for large, high pressure, high temperature, corrosion resistant equipment. Differences in corrosion and erosion conditions drive significant differences in the equipment design and construction. The largest single application of titanium clad equipment has been in construction of reactors, crystallizer pressure vessels, and columns for manufacture of Purified Terephthalic Acid (PTA). PTA is a polymer intermediate used in manufacture of polyester based products, ranging from fibers to PET food containers. As the world demand for polyester based products has continually grown over recent decades, the demand for titanium clad manufacturing equipment has followed suit. In parallel, the continuing efforts to reduce product costs have driven the process designers to ever increasing plant capacities. The largest and heaviest titanium clad equipment in a modern PTA plant are the reactor, Figure 1, and the dehydration tower Figure 2. Operating conditions are typically 200 to 220°C and 20 to 22 bar. Titanium is totally impervious to corrosive attack in this environment. Titanium’s selection assures long term, low maintenance performance while also assuring product purity. With the exception of areas around mechanical connections, such as nozzle and flange faces, crevice corrosion is not a concern. Unalloyed titanium, ASTM B265 Grade 1, is the alloy of choice. In the absence of both corrosion and erosion concerns, titanium thickness is driven by commercial issues and tends to be in the 2 mm to 4 mm range. In today’s larger reactors and columns, steel thicknesses are in the 50 to 100 mm range. Table I presents a list of recent PTA projects.

(Fig. 1: PTA oxidation reactor) (Fig 2: PTA dehydration tower)

Coek Engineering NV - 4 -

TABLE 1: Titanium clad PTA equipment manufactured by Coek.

Project Owner Company Equipment supplied Year

PTA2 Belgium Bp Oxidation reactor, crystallizers, heat exch. 1990 PTA Yizeng 1 Sinopec Oxidation reactor 1993

PTA Capco 5 Capco (bp) Oxidation reactor, crystallizers 1993

PTA USA Bp Oxidation reactor, heat exchangers 1995 PTA Brasil Rhodiaco (bp) Crystallizers, Heat exchagners 1995

PTA Malaysia Bp Oxidation reactor, crystallizers 1995

PTA Indonesia Bp /Mitsui Oxidation reactor, crystallizers 1995 PTA Pakistan Dupont /Invista Oxidation reactor, crystallizers 1996

PTA 3 Belgium Bp Oxidation reactor, crystallizers, heat exch. 1997

PTA USA Bp Oxidation reactor 1997 PTA china Lu-o-yan Bp Oxidation reactor, crystallizers, heat exch. 1998

PTA India Misubutshi Oxidation reactor, crystallizers 1998

PTA Iran NPC Oxidation reactor, crystallizers, heat exch. 2000 PTA Zuhai (China) Bp Oxidation reactor 2001

PTA Capco 6 Capco (bp) Oxidation reactor, dehydration column, drum 2001

PTA Canada Interquisa Oxidation reactor, crystallizers 2001 PTA 3 Taiwan Formosa Oxidation reactor, crystallizers, heat exch. 2001

PTA Spain Interquisa Oxidation reactor, crystallizers 2002

PTA Panipat (India) Dupont / Invista Condensors 2003 PTA T8 (UK) Dupont Condensors 2003

PTA Indorama (Thailand) Invista Oxidation reactor, crystallizers 2003

PTA FCFC Ningbo Formosa Absorber column, heat exchangers 2003 PTA Zong Heng (China) Invista 2 oxidation reactors, 4 Condensors, preheaters 2004

PTA Reliance (India) Invista Cyrstallizers, condensors, preheaters 2005

PTA Liaoyang (China) Invista Oxidation reactor, crystallizers, preheaters 2005 PTA Heng Sheng 1 (China) Invista Crystallizers 2005

IPA FCFC China Formosa Dehydration column, oxidation reactor, heat exchangers

2006

PTA Zuhai (china) bp Oxidation reactor 2006 New production facilities of Coek in Geel are taken in operation end 2004 to produce large Ti clad equipment up to a diameter of 10 metres, and a total weight of 1000 metric tons.

Coek Engineering NV - 5 -

The second largest application of titanium clad equipment is in hydrometallurgical pressure acid leaching (PAL) of metal from ore. Titanium clad has been used in construction of autoclaves for leaching many primary metals (Ref 2). The largest single application has been in the leaching of nickel and cobalt from laterite ores (Ref 3). Titanium clad equipment has included the main autoclaves, preheaters, and flash tanks. Figure 3 shows a typical nickel PAL autoclave. The autoclaves are typically in the range of 4 to 5 m diameter and 25 m to 35 m long with a total weight of 600 to 800 tons.

Typical operating conditions are 250 to 270°C at pressures up to 75 bar. The leachant is primarily sulfuric acid in the 5% concentration range, contains significant concentrations of oxidizing metal ions, and may contain high concentrations of chlorides (30,000 ppm). The steel wall thickness required for pressure containment is in the 100 to 130 mm range. Potential process scale build-up on the autoclave interior can result in crevice corrosion situations. The combination of the severe general corrosion conditions combined with potential crevice conditions has driven most designs to the enhanced titanium alloys, either Grade 11 (0.2% Pd) or Grade 17 (0.05% Pd). The autoclave operating environment can also exhibit significant erosion conditions. Equipment designers have tended to add additional titanium thickness to provide an erosion allowance. In the nickel leaching autoclaves that have been fabricated, nominal titanium thickness has ranged from 6.4 mm to 9.0 mm. (Ref. Table II)

TABLE II: Titanium clad PAL autoclaves for nickel and cobalt leaching.

Project # Units

Thickness(mm) Steel Ti

Cladd alloy Fabricator Year

Cawse, Australia 1 100 8 Ti GR 11 1997 Bulong, Australia 1 100 8 Ti GR17 1997 Murin Murin, Austr 4 100 8 Ti GR 1 1997 Goro New Calidonia 3 117 8 TI GR17 Coek 2003 Rio Tuba, Philipines 1 100 8 TI GR17 2003 CVRD, Brasil 2 112 8 TI GR17 Coek 2006

(u.c.) * * u.c. = Under construction.

Fig. 3: PAL autoclave

Coek Engineering NV - 6 -

CLAD SUPPLY

Explosion welding is the only process for manufacture of large, thick titanium clad steel. The unique features of the technology provide a means to weld metallurgically incompatible metals, such as titanium and steel, without formation of deleterious intermetallic compounds (Ref 4,5). Since the early 1960’s the explosion clad technology has been well developed and evolved into a highly robust, reliable manufacturing industry. For the large equipment typical of the PTA and PAL markets, manufacture of large clad plates is critical for minimizing fabrication costs. To produce large plates, explosion clad manufacturers need large flat plates of ductile titanium. The low strength, ductile alloys, Grades 1, 11, 17, 27, are preferable for cost effective manufacture. Frequently the titanium cladding plates are not available or not manufacturable in the large sizes needed for the head forming. Explosion clad manufacturers typically fabricate the required larger cladding plates by prewelding two plates of titanium together using fusion butt welding processes. Under Coek’s design, shell plates are always cladded from a single titanium plate. The explosion clad plates are typically manufactured in compliance with specification ASTM B898 (Ref 6,7) to assure suitability for the intended use. B898 requires that the manufacturer perform ultrasonic inspection to confirm bond integrity and perform bond shear strength testing. However Coek requires even more stringent restriction with respect to shear values and flatness of the plates, as well a the requested ultrasonic check level to ensure the bonding also after post weld heat treatment and hot forming of the heads. (shear test values of 200 N/ mm², and maximum unflatness of 3 mm/m for the Ti plate before cladding) Details regarding the explosion cladding technology and clad manufacturing concerns are readily available in published literature and are not further addressed here (Ref 8,9,10).

VESSEL CONSTRUCTION DESIGN ISSUES

Titanium clad equipment requires unique fabrication and welding processes when contrasted to stainless steel and nickel alloy clad equipment. When fabricating the latter, clad is restored over the steel joints using weld overlay processes. Due to formation of brittle Ti-Fe intermetallics, this is not possible with titanium-steel clad. Traditionally the clad restoration in titanium clad fabrication has been achieved using batten straps (Ref 2) which are placed on top of the cladding and welded at the edges with fillet welds. Figure 4 shows a cross section of a traditional batten strap weld, in case of 8 mm cladding. When the titanium cladding layer is relatively thin, such as in the PTA equipment, this technology has an excellent production and performance record. When the cladding layer is thicker, as in the PAL equipment, there are a number of problems with the traditional batten strap design. It is difficult to automate the welding. It is difficult to inspect the welds. The stresses in the welds can be high due to differential thermal expansion issues. The batten strap stands proud inside the vessel presenting concerns with location of internals and complicating issues when erosion is a concern. In collaboration with the University of Ghent, Coek has designed and qualified a modified batten strap design which reduces localized stresses and permits lower cost automated welding processes.

Fig 4: Cross section of traditional batten strap weld (8 mm titanium)

Coek Engineering NV - 7 -

Mechanical testing of full thickness (117 mm steel + 8 mm titanium) weld assemblies was performed by University of Ghent. Specimens of both the traditional batten strap design and of the recessed batten strap design were manufactured and tested. Figure 5 shows the tensile test specimen. Figure 6 shows a bend test specimen during testing. Tables III and IV present test data.

Fig. 5: Tensile specimen, 125 mm thick clad plate Fig. 6: Four-point bend test, 125 mm With steel weld and Coek batten strap weld. Thick Coek batten strap design weld specimen. TABLE III: Tensile test data presenting strain vs load for the two batten strap designs.

TABLE IV: Bend test data presenting strain vs load for the two batten strap designs.

3,32 4,79 0,104 0,103 0,085 0,094 point 4 (cover plate)

8,35 3,89 0,273 0,109 0,211 0,071 point 3 (across weld)

6,6 5,1 0,251 0,118 0,188 0,078 point 2 (across weld)

6,09 2,67 0,226 0,169 0,175 0,12 point 1 (cladding)

Local strains (%) :

30,39 31,4 2,5 2,75 2,055 2,109 Deflection at mid-span (mm)

design design design design design design

Original Modified OriginModifieOriginal Modified

capacity ) stress (177 Mpa) (136 MPa)

(maximum load At 1.3 times At design stress

Load of 1000 KN Load of 300 KN Load of 235 KN

0,493 0,619 0,222 0,249 0,171 0,206 point 4 (cover plate)

0,43 0,436 0,211 0,247 0,153 0,213 point 3 (across weld)

0,603 0,58 0,268 0,256 0,201 0,196 point 2 (across weld)

0,47 0,478 0,239 0,345 0,169 0,317 point 1 (cladding)

Local strains (%) :

design design design design design design

Original Modified Original Modified Original Modified

applied ) stress (177 Mpa) (136 MPa)

(maximum load At 1.3 times design At design stress level Load of 4870 KN Load of 2990 KN Load of 2300KN

Coek Engineering NV - 8 -

VESSEL FABRICATION ISSUES

Strip Back: The titanium must be removed from the steel before the steel welding can be performed. This is commonly referred to as “Strip Back”. Strip back can be achieved by a number of ways: milling, cutting a notch and peeling, or arc gouging. Coek has concluded that milling is technically the most viable solution. However, clad plates are not perfectly flat, any effort to mill off the clad must compensate for flatness variations. Coek has invested in special equipment to reduce strip back problems and consequently reduce costs and increase quality. The large PTA and PAL vessels typically are such large diameter that the clad cans cannot be rolled from a single piece of clad plate. To produce these large diameter cans, Coek welds two or more plates end to end prior to rolling the cylinders. These welds are made only in the steel. Unless proper preparations are considered, the rolling conditions can cause clad disbonding at the edges of the butt welds. At Coek, only the ends of the plates are fully prepared for welding prior to can rolling. The titanium is stripped back along the other edges but the steel edge is left square. The longitudinal seams in the steel are

fully welded and the cans are rolled true. Fig. 7 and 8 gives an overview of the rolling campaign as well as finished rolled cans. Also note the titanium protection with plastic sheets on the inside of the can. The rolled cans are then aligned using a unique proprietary device to insure precise fit up of the circumferential joint prior to welding. Misalignments

should be avoided as much as possible in order to prevent thermal stresses on the titanium welds during operation. The steel weld is completed using the SAW welding process. Welds are inspected by angle beam UT, radiography or TOFD, dependent upon steel thickness and weld position. The unique automated equipment and processes allow Coek’s assembly to be quite efficient.

Fig 7: Rolling of 130 mm plates

Fig 8: Rolled Ti clad cans

Coek Engineering NV - 9 -

Nozzle construction: The Nozzle construction for a titanium clad vessel is a very critical issue in the fabrication and design of a titanium clad vessel. Due to thermal expansion, relatively high stresses can be obtained during operation of the equipment. Therefore the fabrication of this construction should be executed with a high level of precautions. For nozzles, it is typical to install a titanium sleeve inside of the steel nozzle. The titanium thickness and contour must be adequately designed to assure that the lining will not collapse during vessel operation. At the vessel interior end of the nozzle, the titanium liner is welded to the clad face. At the other end of the nozzle, the titanium liner must be securely attached to the nozzle face to assure stability in the gasket area. Coek has performed finite element analyses on the nozzle configurations typically used for Titanium clad equipment. The calculated stress

intensities are within acceptable ranges, but proves that adequate workmanship, welding performance and extend of examination in this area are key factors to avoid failure of this construction. Picture 1 gives the stresses under internal pressure (7 barg) and temperature of 177°C on Carbon steel and titanium. Picture 2 gives the stresses under the same conditions as under Picture 1, with the selection set of only titanium components. Picture 3 gives the deformation shape under pressure and temperature. The collar sleeve

thicknesses as used in the examination are 3 mm, corresponding to the design conditions as used for the PTA equipment.

Picture 1 Picture 2

Picture 3

Coek Engineering NV - 10 -

Head Manufacture: The preferred process for manufacture of titanium clad heads is hot pressing in the temperature range of 600 to 700°C. At lower temperatures, there is risk of clad disbonding. At higher temperatures, the titanium-iron intermetallic begins to form at the bond, causing loss of bond strength relatively quickly. Figure 8 presents the relationship between bond strength, forming temperature, and time at temperature. Fig.8: Titanium-steel shear strength as a function of time at forming temperature.

0

50

100

150

200

250

300

350

400

1 2 4 6 10

Time (hours)

She

ar S

tren

ght (

MP

a)

598°C654°C709°C821°C

The diameters of the large PTA and PAL vessels typically exceed the size limits of available hot pressing equipment for making fully formed, single piece heads. Consequently segmental construction is common for these heads. The crown plate and petal plates are individually formed by hot pressing as described above and then welded together to produce the complete head. Fig.9 shows the press used

to form the head segments. When making the welds between the head components, it is critical that the fabricator welds the dish ends prior to final forming to avoid distortion. The cold pressing which is subsequently

required to remove weld distortion can cause clad disbonding, particularly when pressure is applied directly on the edge of the crown or segments. At Coek, large manipulators permit automated positioning of the head beneath the weld torch assuring best welding position and technique.

B898 required shear value after bonding

Coek’s required min. After bonding

Fig 9 : Head press (2500 tons)

Coek Engineering NV - 11 -

Heat Treatment: High steel thicknesses mandate post weld stress relief heat treatments (PWHT) for most PTA and PAL vessels. The PWHT is performed after completion of the steel welds and prior to welding the titanium batten strip. The 20 x 10 x 12 m heat treat furnace at Coek provides the capability to perform most PWHT under optimum conditions.

Very large vessels are fabricated in sections, with the steel closure welds being made after completion of much of the titanium liner work. The steel closure welds are typically given PWHT using localized heat treatment procedures. Fig. 10

illustrates the closing seam of an

autoclave fabricated

and heat treated in 2 pieces. (2 systems will be used for local

PWHT: induction heating or resistance heating. The temperature will be controlled by thermocouples per seam. Titanium Clad Restoration: To complete the vessel interior, titanium batten strips are applied using partial inlay strip or overlap strip design, dependent upon lining thickness and weld contour. Where

ever possible, automated wire fed GTA procedures are employed to assure reliability and minimize cost. As with all titanium welding, shielding gas control is critical to assure reliable weld quality. Gas protection on the backside of the batten strap welds is achieved using shielding gas feed ports drilled through

from the steel side. Figures 11 shows the final batten strap appearance in case of 8 mm Titanium cladding. (Cover strip of 3 mm based on Coek’s revised coverstrip design.) Internal Components: The PAL vessels typically have significant titanium internal components. The titanium internals are welded directly to the surface of the titanium cladding. However, thermal expansion issues must be fully analyzed during design of the internals and the attachment welds to assure that stresses resulting from the differential expansions of steel and titanium (approximately 2:1 ratio) do not tear the components or welds apart. Expansion devices and slip joints are typically used.

Fig 11 : Titanium clad surface on interior after completion of batten strap welds.

Fig 10 : Closing seam of autoclave

Coek Engineering NV - 12 -

During welding, it is extremely important that all welding is executed in a clean environment, and under full argon atmosphere. Titanium Weld Inspection: Titanium cover strip welds are 100% inspected by penetrant testing followed by air and helium leak testing. The weld purge holes provide an easy method for introducing air at the weld backside. The location and position of these welds are such that radiography and/or angle beam ultrasonic inspection are not possible. Vessel Testing: Upon completion of fabrication, hydrostatic testing is performed in accordance with

pressure vessel code requirements. Additionally hot cycle pressure tests, performed under simulated pressure/temperature service conditions, are performed to confirm liner reliability. Two hot pressure test cycles are commonly performed, followed by re-testing of all liner welds using penetrant and helium leak procedures. Any defective areas must be reworked. If significant rework is preformed, additional hot cycle tests are often mandated. Fig 12 shows the execution of a hot gas cycle test for a PAL autoclave.

Finishing: Upon completion of all fabrication the titanium surfaces are conditioned to assure that no iron contamination is present on the titanium surface, mechanical conditioning and/or pickling are typical. Absence of surface contamination is confirmed by ferroxyl testing. The vessel exteriors are painted as appropriate for the operating environment and owner requirements. Nozzles are blanked off and the units are sometimes pressurized with dry nitrogen to prevent contamination during transit.

Fig 12 : Hot gas cycle test

Coek Engineering NV - 13 -

Transit: Logistics of large vessel transport are often complex and difficult. The weight of PTA and

PAL equipment can often approach 1,000 metric tons while heights may be up to 10-meters or more. Road transport often requires massive multi-wheel transit carriages and in some regions may be impossible. These transport issues are a critical component of initial vessel design. At Coek the transport issues are minimized by convenient site location, with roll on roll off facilities, adjacent to an industrial canal which provides access to ocean ports. Fig. 13 illustrates a transport of a titanium clad dehydration column of 600 tons. (total transportation weight of 800 tons.)

EQUIPMENT PERFORMANCE As indicated in Tables I and II, there are a significant number of large titanium clad pressure vessels in service. Some PTA units have been in service for over 30 years. Experience shows that properly designed and fabricated titanium clad units offer reliable, maintenance free service performance and are a cost effective solution to a difficult equipment problem. Experience also shows that failure to fully consider service conditions in the design stage or failure to fabricate using proper techniques and procedures can result in equipment that does not perform to expectation. Improper design and/or construction can result in highly shortened service life, significantly increased maintenance, and critical safety concerns. This has clearly been demonstrated in some installations, both PTA and PAL.

CONCLUSIONS

Developments in clad manufacture and fabrication techniques have made possible the manufacture of reliable, large titanium-steel clad equipment. A novel recessed batten strap design has been developed and qualified for clad restoration. The new design offers significant benefits when the titanium cladding is thick, as is typical of pressure acid leaching autoclaves. Vessels as large as 10 m diameter, 75 m long, and/or 125 mm wall thickness have been fabricated and are performing reliably in severe process environments.

Fig. 13: Road transport to the Ro-Ro kade

Coek Engineering NV - 14 -

REFERENCES

1. Donachie, M.J.Jr., Titanium, A Technical Guide, ASM International, Metals Park, OH, 1988. 2. Banker, J.G., Forrest, A.L., “Titanium/Steel Explosion bonded Clad for Autoclaves and

Reactors”, Proceedings of Randol Gold Forum ’96, Randol Corp., Golden, CO, 1996.

3. Banker, J. G. and Winsky J. P., “Titanium/Steel Explosion Bonded Clad for Autoclaves and Vessels,” Proceedings of ALTA 1999 Autoclave Design & Operation Symposium, Alta Metallurgical Services, Melbourne, Australia, May 1999.

4. Holtzman, A. H. and Cowan, G. R., “Bonding of Metals with Explosives”, Welding Research

Council Bulletin No 104, April, 1965

5. Pocalyko, A., “Explosively Clad Metals” Encyclopedia of Chemical Technology, Vol 15, third Edition, John Wiley & Sons, 1981, pp 275-296.

6. “Standard Specification for Reactive and Refractory Metal Clad Plate.” Specification ASTM

B898-99, ASTM International, Conshohocken, PA 1999

7. Banker, J.G., “An Introduction to ASTM B898, the Reactive and Refractory Clad Metal Plate Specification”, Proceedings of Corrosion Solutions Conference 2001, Wah Chang, Albany, OR, 2001

8. Blazynski, T. Z., Explosive Welding, Forming, and Compaction, Applied Scientific Publishers

Ltd., Essex, UK, 1983.

9. Patterson, A., “Fundamentals of Explosion Welding”, ASM Handbook, Vol. 6, Welding, Brazing, and Soldering, 1993, pp 160-164.

10. Banker,J.G. and Reineke E.G., “Explosion Welding”, ASM Handbook, Vol. 6, Welding,

Brazing, and Soldering, 1993, pp 303-305.