Nuclear

Features

• Small heat affected zone
• Joints are homogeneous, leak tight and very strong
• Low incidence of defects
• Repeatable weld configurations
• Near parent metal strength on the weld
• Many different and specialist metals can be welded
• Versatile weld parameters and precision control employed to achieve the desired end product

Electron beam welding has been adopted on a large scale in the nuclear industry. The properties of a small heat affected zone, low incidence of defects and near parent metal strength are exploited in the fabrication of fuel and coolant containers of all sizes.

Problem

In this example the tubular fabrication in austenitic stainless steel type 304L shown above, is made up of three pieces: a hexagonal base welded to a tube with the tube itself capped by a nosepiece. The whole assembly is some 2 m in length. The requirement is for a straight assembly without significant drooping due to contractio distortion.

Solution

The solution adopted involved pre-weld tacking at low power followed by 120° of full weld depth and completed by a full circumference weld of full depth commenced on the opposite side to the 120° of pre-weld. The various distortions engendered by this regime cancelled each other to produce straight assemblies. The weld fusion zone was made at a sufficient level of power to over penetrate and produce a heavy consolidated internal bead. This was sufficiently large to be machined to parent metal diameter and give a smooth bore.