Abstract
Industry can manufacture high strength, high grade steel but the problem is: How to join?
Friction Stir, Linear / Tubular Friction and Flash Butt are solid state but each have its limitations. Remaining practice is to melt either with or without filler material – K-Tig, Electron Beam, Plasma and various filler material that mix and match to compensate for the change across heat affected zone (HAZ); molten metal resting against cold steel. Coarse Grain resting on Fine Grain, Intergranular Stress, Residual Stress and Stress Risers are some of the suspected entry points of hydrogen atom.
An alternative joining technique uses standard off the shelf parts but arranged in a slightly different order. Result is a weld that is fine grained base to base, no fusion line; one shot in an inert environment and autogenous. This technique joins using technicians, not welders. The three components are induction heating across work faces, forge and sheari. Weld integrity is documented in real time. No toxic fume. Geometries are flat, curved and tubular.
Royal Society Publishing Dear and Skinnerii and NACE publicationiii stated ‘Presently this phenomenon is not completely understood’. And as Afrooz Barnoush stated: there are so many different processes happening that I think we should perhaps specify them and consider them separately.
Considering only one aspect – the surface. It is the first line of defence, the armour against hydrogen entrance or accumulation. Characteristics of this solid state weld is that the ID is smooth, no discontinuation between base metal and fusion area. Weld O.D., I.D. are in uniform compression, verified using Frontics AIS3000 indentationtesteriv. The armour is tightly knit. Because the weld is one shot, when the work facesjoin and shear, the interior of the weld is the last to cool. As the entire weld cools, theexterior is drawn inwards, it shrinks. Thus compression. Interior of the weld is in
tension. Transition boundary between compression and tension needs further analysis. It is assumed that thickness of workpiece will affect depth of compression.
This technique will benefit planned pipelines for Hydrogen; can weld shut spent nuclear fuel container lid, next to fuel pellets safely. Risers can be joined using even higher strength steel, thinner wall, less weight, pipe to pipe and pipe to flange.