ACRM-WELDING Flashcards
Blending of compatible molten metals into one common part or joint.
FUSION
Joining of metals by adhesion of one metal to another
NON-FUSION
Primary concern to a welder. Metal oxides are formed in the welding zone of most metallic alloys when sufficient heat is applied. Oxygen chemically reacts with the heated surface of the metal and forms metal oxides such as iron oxide or aluminum oxide.
OXIDATION
Oxygen and acetylene, that are used to produce a flame. Acetylene is the fuel for the flame and oxygen supports combustion and makes the flame hotter. Temperature of the oxyacetylene welding ranges from 5600F to 6300F.
OXYACERELENE WELDING
Predominantly used in aircraft fabrication and repair.
ELECTRIC ARC WELDING
Stick welding is the most common type of arc welding. Composed of approximately the same chemical composition as the metal to be welded, is clamped in an electrode holder.
Capable of exceeding 10,000F
SHIELDED METAL ARC WELDING (SMAW)
Used primarily in large volume production work. No slag is deposited on the weld bead. An uncoated filler wire acts as the electrode.
An inert gas such as argon, helium or carbon dioxide flows out around the wire to protect the weld zone from oxygen.
GAS METAL ARC WELDING (GMAW)
Used in most aircraft maintenance. TIG welding uses a tungsten electrode that does not act as filler rod. The arc is concentrated on a small area of the metal, raising its temperature to as high as 11,000F.
TUNGSTEN INERT GAS WELDING (TIG)
Many thin sheet metal parts for aircraft, especially stainless steel parts, are joined by one of the forms of ______ ________ __________.
ELECTRIC RESISTANCE WELDING
Two copper electrodes are held in the jaws of a vise-like machine and the pieces of metal to be welded are clamped between them. Pressure is applied to hold the electrodes tightly together while electrical current passes between the electrodes. The duration that the electric current flows is referred to as the dwell time.
SPOT WELDING
Commonly used to manufacture fuel tanks and other components where a continuous weld is needed. The metal in a seam welder is drawn between two coppers. Pressure is applied to the wheels and timed pulses of current flow through the metal between them.
SEAM WELDING
TYPES OF WELDED JOINTS
BUTT, EDGE LAP, CORNER, TEE
Metal that is deposited as the weld is made
BEAD
Exposed surface of the weld
FACE
Depth that fusion penetrates into the base metal
ROOT
Distance through the center from the root to the face
THROAT
Edge formed where the face of the weld meets the base metal
TOE
Quantity of weld metal added above the surface of the base metal
REINFORCEMENT
Form of metal joining in which an iron-free metal is used as a cohesive material, usually brass or bronze, is melted with an oxyacetylene torch at a temperature above 800F
TORCH BLAZING
is used to clean the surface of the metal being joined. A ______ coating on a filler rod allows it to flow when melted and to adhere to a base metal surface.
FLUX
Normally melt at temperatures lower than 800F.
TORCH SOLDERING
A technician may need to solder joints in an air-conditioning system
Made with a close fit between the parts. The joint is fluxed and uniformly heated with a soft flame.
Primarily a mixture of tin and lead
SOFT SOLDERING
The filler material melts at a temperature more than 800F. The oxyacetylene flame for silver soldering should be neutral, but may have a slight excess of acetylene. The flame must be soft.
To conform to commonly accepted terminology in aircraft maintenance, silver brazing will be called silver soldering.
Stainless steel oxygen lines often have their end fittings attached by silver soldering.
HARD SOLDERING
Difficult to weld since the color does not change as it nears the melting temperature.
Done with gas-shielded electric arc, sometimes either acetylene or hydrogen gas. Hydrogen is preferred due to cleaner flame and less risk of oxidizing. For an equal thickness of metal, hydrogen requires a larger tip.
Flame should be neutral or slightly carburizing.
GAS WELDING
Preferred method. The heat from the TIG torch is much more concentrated that is it with an oxygen torch.
It should be brushed with a hog bristle or stainless steel brush to remove the oxide film, then scrubbed with solvent.
TIG WELDING
Use more oxygen. The cut made by an oxyacetylene cutting torch is known as a kerf.
OXYACETELENE CUTTING
