A. Introduction

Explosives have been used for about 100 years to perform constructive metalworking operations, but during the past 30 years they have been developed into a vital production tool. The principal applications for explosives are forming of complex cylindrical and conical shapes, manufacture of clad heat exchanger tubesheets, hardening of metals to improve mechanical properties, compacting of powders for high-den-sity pans used in aerospace and atomic energy applications, and attachment of tubes to tubesheets in tubular heat exchangers. Explosive tube end welding is a well-established production method and offers many advantages over other methods of tube-tubesheet attachment.

Because it provides high joint strength, leaktight-ness, and trouble-free operation, explosive tube end welding has been used extensively in shell-and-tube heat exchangers in a variety of industries where leak-tight joints are critical. This includes applications involving high pressures and/or high temperatures, sometimes under cyclic or shock conditions, its location renders the joint less susceptible to problems of corrosion or erosion.

Combinations of materials incompatible for fusion welding can usually be explosive welded, and pre- or post weld heat treatment is not required. The ability to explosive weld incompatible materials can often significantly reduce the overall cost of the exchanger. In the case of materials such as Hastelloy and titanium, which can be welded by conventional means, it may be cheaper to adopt explosive welding.

Explosive welds can be tested by ultrasonic methods, and once explosive parameters have been determined they are 100% reproducible.