Supplied B1 Module 07A textbook: PDF pages 315–358.
What each process joins
Welding fuses base material, with or without filler. Brazing joins using a filler that melts while the base parts remain solid. Soldering uses lower-temperature filler and is common for electrical connections. Adhesive bonding creates a joint with a compatible adhesive and prepared surfaces. These processes have different heat effects, joint design and qualification requirements. A repair approved for one process is not automatically approved for another. Identify the material and joint purpose before selecting a technique.
Which process normally melts the base material locally? Welding.
Soldering preparation and technique
Clean the surfaces and use the specified solder and flux. Heat the joint so solder wets the intended surfaces; merely melting solder on the iron can leave a poorly bonded joint. Provide mechanical support and strain relief as required so the solder does not carry unintended loads. Avoid excessive heat that damages insulation or components. Remove flux residues when required by the process. Lead-free and traditional solder systems have different process characteristics, so appearance criteria must be appropriate to the material.
What produces a properly wetted solder joint? Heating prepared surfaces so solder flows onto them.
Inspection of soldered connections
Inspect for wetting, correct solder quantity, bridging, loose strands and insulation damage. A cold joint results from inadequate heating or disturbance and may be weak or resistive. Do not assume every dull surface is defective; some solder systems are naturally less shiny. A smooth appearance does not prove that the conductor and terminal are correctly prepared. Follow magnification and acceptance requirements. Solder must not conceal a mechanically loose or incorrectly made connection.
What is solder bridging? An unintended solder connection between separate conductors.
Welding methods and gas safety
Gas welding uses a controlled flame; arc processes use an electric arc. TIG uses a non-consumable tungsten electrode and shielding gas, while MIG uses a consumable wire electrode. Match shielding, filler, polarity and process to the material. Protect eyes and skin from radiation, provide ventilation and manage hot work. Keep oxygen fittings free of oil and secure cylinders. Do not use a flame for leak testing. The aircraft repair must use the approved welding procedure and qualified personnel.
Which process uses a non-consumable tungsten electrode? TIG.
Brazing and welded-joint defects
Brazing depends on clean surfaces, suitable clearance and filler flow, often by capillary action. Welding quality depends on fusion, penetration, joint preparation and heat control. Inspect for cracks, porosity, lack of fusion, undercut and distortion using the prescribed visual and other methods. A large weld bead is not necessarily strong: excess reinforcement can coexist with poor fusion. Heating may alter nearby material properties or protective coatings. Do not grind away evidence of a defect before assessment.
What is lack of fusion in a weld? Failure of joined surfaces or filler to fuse where required.
Bonded joints and process control
For adhesive bonds, surface chemistry and preparation can be as important as adhesive identity. Control mix ratio, usable life, bond-line thickness, clamping and cure. Avoid contamination after preparation and apply the adhesive within the prescribed time. Inspect squeeze-out, alignment and specified NDT results, while recognising that a good-looking seam cannot prove all bond properties. Record process parameters and follow the approved repair data. Rework must address the actual defect rather than adding adhesive around a weak joint.
Why are bond preparation and cure records important? Critical bond quality depends on controlled process conditions.
Apply the knowledge
Work through these examples before starting the quiz. Explain why the other choices would not meet the requirement.
A solder joint has a bead on the terminal without wetting. What is the concern?
Poor bonding from inadequate preparation or heating — Solder must wet the specified surfaces.
Which distinction between MIG and TIG is correct?
MIG uses consumable wire; TIG uses non-consumable tungsten — Electrode arrangement distinguishes the processes.
A weld looks smooth but NDT reveals a crack. What is correct?
Assess or reject it under the approved acceptance criteria — A surface finish cannot override a confirmed unacceptable discontinuity.
A brazed joint is made with dirty surfaces. What is likely affected?
Wetting and filler flow — Clean surfaces are necessary for effective brazing.