The 6 Basic Joint Types for Friction Welding

The origin of friction welding and 6 basic joint types dates back to the Soviet Union in 1956 when first experiments and patents on the process were issued. In the early 1960’s American friction welding companies Caterpillar, Rockwell International, and American Manufacturing Foundry filed patents and developed proprietary machines for the friction welding process. Rotational friction welding machines can either be inertia friction welding or direct-drive friction welding machines. The basic joint types are used for either process but the principles of an inertia and direct drive friction welds are slightly different.

Friction welding is sometimes referred to as spinning or spin welding. A friction welding joint is sometimes referred as interface, fusion, or bond and is a point or edge where two or more pieces are joined together by friction. In the basic use friction welding, raw materials are saw cut and sometimes machined to a particular geometry and the process is ready to start.

The industry has six basic types of joints that have been defined as:
  1. Tube to Tube – Tubular, equal outside diameter, equal inside diameter
  2. Tube to Bar – Tubular, equal outside diameter, equal inside diameter
  3. Tube to Disc – Tubular, unequal outside diameter, equal inside diameter
  4. Tube to Plate – Tubular, unequal outside diameter, unequal inside diameter
  5. Bar to Bar – Solid, Equal diameters
  6. Bar to Plate – Solid, unequal diameters

In most cases, the use of balanced geometry welds (bar to bar, tube to tube) is recommended. This maintains a balanced heat flow and eases the flash removal process when required. All joint types produce successful, full strength, and 100% full interface bonding.

The different joint types allow for the use of similar or different (bi-metal) material welds for advantages in:
  1. Material savings
  2. Weight reduction
  3. Improved part performance
  4. Secondary processes time reduction
  5. Tooling cost savings

Common weld unions include same materials of different sizes. Specialty welds include the use of different materials, semi-finish or finished components, 3 materials or 2 weld unions, and odd shapes or non-round parts. Spinweld’s one business day friction welding feasibility analysis will help recommend a suitable joint type based on your needs or project specifics.