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SAE ARP1317 Revision A, October 1, 2000
Electron Beam Welding
Description / Abstract:
Purpose:
This Aerospace Recommended Practice (ARP) describes techniques recommended for use in producing electron beam welded joints in materials commonly employed in the aerospace industry.
Application:
The guidelines herein are oriented toward the use of welding equipment capable of maintaining the workpiece at pressure levels of 1 x 10-4 Torr (133 x 10-4 Pa) or lower during welding.
Radiation Hazard:
When operating, electron beam welding machines create radiation.
Guidelines and procedures referenced herein regarding radiation levels are contained in U.S. Department of Commerce, Bureau of Standards Handbook No. 60, X-ray Protection.
Safety - Hazardous Materials: While the materials, methods, applications, and processes described or referenced in this specification may involve the use of hazardous materials, this specification does not address the hazards which may be involved in such use. It is the sole responsibility of the user to ensure familiarity with the safe and proper use of any hazardous materials and to take necessary precautionary measures to ensure the health and safety of all personnel involved.
Discussion of Process:
Description of the Process: Electron beam weldig is a process wherein coalescence of adjacent metal surfaces is produced by the heat obtained from a concentrated beam composed primarily of high-velocity electrons impinging on the surfaces to be joined. In the type of equipment used primarily in aerospace applications, welding is performed in a vacuum chamber in which both the work piece and the electron gun are at pressure levels of 1 x 10-4 Torr (133 x 10-4 Pa) or lower. Welding voltage levels used are normally in the range of 30 to 150 kV at currents up to 1 A.
Advantages of the Process:
Depending on the power of the machine, butt joints over 5.0 in (127 mm) thick can be produced in most weldable materials in a single pass because of the very high energy density available with the process.
Welds can be produced with a very high depth-to-width ratio with correspondingly narrow heat-affected zones. Shrinkage and distortion are minimized, and, with some alloys, metallurgical and mechanical property changes between the parents metal and the weld zone are small when compared with most other fusion welding processes.
It is often possible to weld joints that would be inaccessible to other fusion welding processes because welds can be made with the joint more than 24 ub (610 mm) from the electron gun (depending on gun design and accelerating voltage).
Different alloys within any one material group may be welded together; in some cases, alloys from different groups may also be welded (see 3.2).
Metals reactive with the atmosphere can be welded without atmospheric contamination because welding is performed in a vacuum.
Limitations of the Process:
The size of assemblies that can be welded is often limited by the vacuum-chamber size. However, in some instances, special chambers can be used that attach to the assembly at the weld joint and avoid the necessity of placing the entire assembly in the chamber.
Close tolerances are required in detail parts to achieve the degree of accuracy required in fit-up to make an acceptable weld.
The addition of filler metal is more difficult than with other fusion welding processes.
Definitions of the terms used herein and specific application of nondestructive testing techniques are contained in ARP 1333 and AWS A3.0.
This Aerospace Recommended Practice (ARP) describes techniques recommended for use in producing electron beam welded joints in materials commonly employed in the aerospace industry.
Application:
The guidelines herein are oriented toward the use of welding equipment capable of maintaining the workpiece at pressure levels of 1 x 10-4 Torr (133 x 10-4 Pa) or lower during welding.
Radiation Hazard:
When operating, electron beam welding machines create radiation.
Guidelines and procedures referenced herein regarding radiation levels are contained in U.S. Department of Commerce, Bureau of Standards Handbook No. 60, X-ray Protection.
Safety - Hazardous Materials: While the materials, methods, applications, and processes described or referenced in this specification may involve the use of hazardous materials, this specification does not address the hazards which may be involved in such use. It is the sole responsibility of the user to ensure familiarity with the safe and proper use of any hazardous materials and to take necessary precautionary measures to ensure the health and safety of all personnel involved.
Discussion of Process:
Description of the Process: Electron beam weldig is a process wherein coalescence of adjacent metal surfaces is produced by the heat obtained from a concentrated beam composed primarily of high-velocity electrons impinging on the surfaces to be joined. In the type of equipment used primarily in aerospace applications, welding is performed in a vacuum chamber in which both the work piece and the electron gun are at pressure levels of 1 x 10-4 Torr (133 x 10-4 Pa) or lower. Welding voltage levels used are normally in the range of 30 to 150 kV at currents up to 1 A.
Advantages of the Process:
Depending on the power of the machine, butt joints over 5.0 in (127 mm) thick can be produced in most weldable materials in a single pass because of the very high energy density available with the process.
Welds can be produced with a very high depth-to-width ratio with correspondingly narrow heat-affected zones. Shrinkage and distortion are minimized, and, with some alloys, metallurgical and mechanical property changes between the parents metal and the weld zone are small when compared with most other fusion welding processes.
It is often possible to weld joints that would be inaccessible to other fusion welding processes because welds can be made with the joint more than 24 ub (610 mm) from the electron gun (depending on gun design and accelerating voltage).
Different alloys within any one material group may be welded together; in some cases, alloys from different groups may also be welded (see 3.2).
Metals reactive with the atmosphere can be welded without atmospheric contamination because welding is performed in a vacuum.
Limitations of the Process:
The size of assemblies that can be welded is often limited by the vacuum-chamber size. However, in some instances, special chambers can be used that attach to the assembly at the weld joint and avoid the necessity of placing the entire assembly in the chamber.
Close tolerances are required in detail parts to achieve the degree of accuracy required in fit-up to make an acceptable weld.
The addition of filler metal is more difficult than with other fusion welding processes.
Definitions of the terms used herein and specific application of nondestructive testing techniques are contained in ARP 1333 and AWS A3.0.
SAE ARP1317 Revision A, October 1, 2000
Electron Beam Welding