Current linear solid state welding process reaches hot working temperature with friction. The world’s largest linear friction machine LF35 – 75 weights 61 metric tons. And the maximum working surface is approximately 15 in2 depending on material. Besides large energy input, typical flash, grain flow and fusion line are signature linear friction characteristics.
An alternative solid state welding process was invented over 2 decades ago. Technique uses all of today’s standard equipment but arranged in a slightly different order. Result is a weld that has no heat affected zone, no fusion line, fine grained base to base, laminar gain flow and a smooth profile. And a residual stress profile that is unique.
Recent patent grants, published and pending has extended this original technique from tubular only to linear, thick to ultra thin w/ no warp or burn through. Ideal for similar to dissimilar materials, especially irradiated material.
Tubular solid state procedure is to place heating coil (s) in-between work faces, take to hot working temperature just below melting in an inert environment, remove coil, forge and shear. Induction supplies over 98% of energy required (EWI.org 2012). Forge and shear make up the remaining 2 – 5% of energy required.
Extending the concept of tubular to linear i.e. induction heating between the work faces, forge and shear in an inert environment, the science is the same.
U.S. DOT and EWI attempted to join Rail using linear friction. The approximate power required to join was 10 tons / in2. EWI experimented w/ traditional pre heat to assist in joining. But the welds that did joint had traditional characteristics.
The proposed method to join Rail using solid state is to place induction coil (s) in-between Rails, take to hot working temperature in an inert environment, remove coil (s), forge and shear. If the science holds true and solid state carries over from tubular to linear, resulting characteristics should be fine grained base to base, no fusion line, heat penetration in millimeters. But more importantly, hardness mapping for linear should mirror tubular characteristics – recrystallized zone slightly harder but no soft dips.
Results and Discussions
Tubular solid state is used by Federal Mogul to join diesel cylinder heads. Technique won The Pace Automotive Award 2016 for innovation. Technique is also used in commercial truck axle 5” O.D. x 5/8” – 7/8” wall and partly commercialized in O&G exploration. Technique falls under ASME IX, code case 2799.
Numerous options has been presented to ANS, AWS, ASM Aeromat, Navy, AREMA etc.
Welding shut spent fuel container lid safely.
Joining 3, 4, 5”+ submarine hull w/ no flaw.
Joining thick to ultra thin w/ no warp, no burn through…
Will be presenting to ICONE30 in Kyoto, May 2023. Subject will be joining nuclear fuel rod to end cap w/ no flaw. Repeatable. Then IIW S’Pore July 2023.
This author is developing 4 – 6” tubular solid state welding equipment. And are actively pursuing linear and other geometries.
Tubular and linear solid state is radical new science. Tubular is proven. Linear is conceptual. Conventional practice has always kept pre heat temperature below certain level. By taking pre heat, then heating to just below melting and then forge and shear is the most radical thinking in the welding industry for the past 75 years.
Technique is modular. For identical material and geometry, the power settings will be identical anywhere in the world. The three variables induction, forge and shear are monitored, weld integrity is documented in real time.
Today’s linear friction equipment using solid state can increase work pieces significantly or reduce equipment footprint.
Tubular solid state will enable pipeline to be joined faster and more secure. There is no root weld, no stress riser. Shipbuilding and submarine can eliminate uncertainty as weld integrity is documented in real time. And for additive manufacturing, additional parts can be joined using solid state instead of filler welding. ITER and upcoming Fusion projects can benefit.