Chapter 33 (Completed)

silver solder

(alloys based on silver and copper) have brazing temperatures significantly below that of pure copper and are used in joining steels, copper, brass, and nickel

induction brazing

1. the complete heating cycle is very rapid, usually only a few seconds in duration 2. the operation can be made semiautomatic so that only semiskilled labor is required. 3. Heating can be confined to the specific area of the joint through use of specially designed coils, frequency control, and short heating times. This minimizes softening and distortion and reduces problems associated with scale and discoloration. 4. Uniform results are easily obtained due to the precise control of both heating rate and final temperature. 5.By making new, and relatively simple heating coils, a wide variety of work can be brazed with a single power supply

autogenous weld

A fusion welding process using heat without the addition of filler metal to join two pieces of the same metal.

fluidity

A measure of the flow characteristics of the molten braze metal and is a function of the metal, its temperature, surface cleanliness and clearance.

thermit

A mechanical mixture of about one part finely divided aluminum and three parts iron oxide, plus possible alloy additions.

laser-beam cutting (LBC)

A process by which a laser beam impinges on the workpiece in order to heat and sever the piece. Also known as ______________.

electron-beam welding (EBW)

A technique for joining materials in which highly collimated electron beams are used at a pressure below 10-3mmHg (0.1333 pascal) to produce a highly concentrated heat source.

electroslag welding (ESW)

A welding process in which consumable electrodes are fed into a joint containing flux; the current melts the flux, and the flux in turn melts the faces of the joint and the electrodes, allowing the weld metal to form a continuously cast ingot between the joint faces.

dip brazing

Assemblies are immersed in a bath of molten brazing metal. The bath provides heat and metal for the joint. It is a somewhat wasteful process and is usually used only for small products.

butt joint

Do not require additional thickness in the vicinity of the joint and are most often used where the strength requirements are not that critical.

fluxless soldering

Includes techniques using controlled atmosphere (hydrogen plasma), thermomechanical surface activation (plasma gas impingment) and protective coatings that prevent oxide formation and enhance wetting.

fluxless brazing

Includes techniques using controlled furnace atmospheres which reduce existing oxides and prevent the formation of new ones. Examples are vacuum furnaces and special brazing metals such as phosphorus.

braze welding

Molten filler is deposited by gravity and is very effective for the repair of steel products and ferrous castings. Capillary action is not required to distribute the filler metal.

molding plates

Plates that confine molten metal. Usually made of copper, that are allowed to slide. As the weld metal solidifies at the bottom of the pool, the molding plates move upward at a rate that is typically between 12 and 40 mm/ min.

noncorrosive flux

Soldering fluxes are generally classified as corrosive or ________. The most common ____________ is rosin.

thermit welding (TW)

Superheated molten metal and slag are produced from an exothermic chemical reaction between a metal oxide and a metallic reducing agent.

laser-beam welding (LBW)

The primary apparatus is the continuous-wave, convectively cooled CO2laser with either oscillator/amplifier (gaussian output beam) or unstable resonator (hollows output beam) optics. These lasers, available in output powers ranging from approximately 1000 to 15,000 W, have been used to demonstrate specific welding accomplishments in a variety of metals and alloys

surfacing

The process of depositing a layer of weld metal on the surface or edge of a base material or different composition. The usual objectives are to obtain improved resistance to wear, abraison, heat, or chemical attack without having to make the entire piece from an expensive material, one that is difficult to fabricate, or one that would not posses the desired bulk properties.

percussion welding (PEW)

_____________ is similar to flash welding, wherein a rapid discharge of stored energy produces a brief period of arcing, which is then followed by the rapid application of force to expel the molten metal and produce the joint. In __________, the arc duration is only 1 to 10 ms. The heat is intense but highly concentrated. Only a small amount of molten metal is produced, little or no upsetting occurs at the joint, and the heat-affected zone is quite small. Application is generally restricted to the butt welding of bar or tubing where heat damage is a major concern.

soldering

a brazing type of operation where the filler metal has melting temperatures below 450 degrees celcius. typically used for connecting the metals, connecting electronic components, joining metals while avoiding exposure to high elevated temperature., and filling surface flaws and defects.

vapor-phase soldering

a product with prepositioned solder is passed through a chamber containing hot, saturated vapors, which condense on the cooler product, transferring the heat of vaporization.

wettability

a strong function of the surface tensions b/t the braze metal and the base alloy. generally, the _____ is good when the surfaces are clean and the two metals can form intermediate diffused alloys.

endothermic cutting

also called clean cutting, results in oxide-free surfaces

laser spot welding

can be performed with access to only one side of the joint. It is a non contact process and produces no indentations. No electrodes are involved, so electrode wear is no longer a production problem.

resistance brazing

can be used to produce relatively simple joints in metals with high electrical conductivity. The parts to be joined are pressed between two electrodes and a current is passed through.

hybrid processes

combining laser welding with arc welding, with both operating in one process zone and producing one weld pool

furnace brazing

if the flux and filler metal can be preloaded into the joints, a number of assemblies can be heated simultaneously in controlled atmosphere or vacuum furnaces

wave soldering

is a process used to solder wire ends, such as the multiple connectors that protrude through holes in electronic circuit boards.Molten solder is pumped upward through a submerged nozzle to create a wave or crest in a pool of molten metal.

upset welding (UW)

is also similar to flash welding, but there is no period of arcing. while the equipment and geometries are similar, the heating is achieved through electrical resistance

metallizing

is the general name for the technique of coating metal on the surface of non-metallic objects.

brazing

is the permanent joining of similar or dissimilar metals or ceramics through the use of heat and a filler metal whose melting temperature is above 450F but below the melting point of the materials being joined Uses a molten filler metal to crate joints. Capillary action is required to distribute the filler metal.

thermal cladding

is the process of depositing a layer of weld metal on the surface or edge of a different composition base material.

assist gas

is used to blow the molten metal through the cut, cool the work piece, minimize the heat-affected zone, and possibly assist in combustion of the material

filler metal

metal used to fill in gaps between two metals

jigs and fixtures

often used to hold components during heating, when used, however, it is necessary to provide springs that will compensate for thermal expansion, particularly when two or more dissimilar metals are being joined

brazing fluxes

play an important part in the process by (1) dissolving oxides that may have formed on the surfaces prior to heating, (2) preventing the formation of new oxides during heating, and (3) lowering the surface tension between the molten brazing metal and the surfaces to be joined, thereby promoting the flow of the molten material into the joint.

thermal spray

processes offer a means of applying a coating of high-performance material (metals, alloys, ceramics, intermetallics, cermets, carbides, or even plastics) to more economical and more easily fabricated base metals.

exothermic cutting

produces an oxidized edge

corrosive flux

provide enhanced cleaning action, but require complete removal after the soldering operation to prevent corrosion problems during service

lead-free solder

since 1988, the use of lead-containing solders in drinking water lines has been prohibited in the U.S. and this ban may well be extended to include other applications and industries. if substitute solders are to be acceptable, however, they should not only be harmless to the environment, but should also exhibit desireable characteristics in areas of melting temperature, wettability, electrical and thermal conductivity, thermal expansion coefficient, mechanical strength, ductility, creep resistance, thermal fatigue resistance, manufacturability, and cost

hardfacing

the deposited surfaces are generally harder than the base metal, joining two different types of metal by welding a bead on the top of the surface of the joint to add strength this should not be used alone if possible

kerf

the gap that is formed after a metal is melted by the flame of the oxyfuel gas torch. It is equal to the width of a groove made by a cutting tool.

rosin

the most common type of noncorrosive flux

joint clearance

the most important of all factors contributing to joint strength; if the joint is too tight, it may be difficult for the braze metal to flow into the gap, and the flux may be unable to escape. there must be sufficient clearance so that the braze metal will wet the joint and flow into it under the force of capillary action. As the gap is increased beyond the optimum value the joint strenght decreases rapidly, dropping off to that of the braze metal itself.

torch brazing

the procedure uses oxyacetylene, oxyhydrogen, or other gas-flame combinations for the source of heat for brazing. most repair brazing is used in this manner b/c of its flexibility and simplicity, but the process is also wide production applications

lap joint

the type of joint that can be made with resistance welding, technique of joining two pieces of material together by overlapping them

capillary action

this is required to bond. _________ distributes the filler metal between the closely fitting surfaces of the joint. The flow is dependent on the viscosity of the liquid, the geometry of the joint, and surface wetting characteristics.

flash welding (FW)

two pieces of metal are placed so they touch on the ends that are to be joined a current is passed through the metal to heat the metal the metal pieces are then separated the electrical charge then jumps from one piece to the other causing the ends to melt the two pieces are then pressed together to form a solid joint

flux

used in brazing to dissolve oxides that may have formed on the surface prior to heating, prevent the formation of new oxides during heating and lowering the surface tension between the molten brazing metal and the surfaces to be joined. It promotes the flow of the molten material into the joint.

dip soldering

where the entire piece is immersed in molten metal, has been used to produce automobile radiators and "tinned" coatings

slat-bath brazing

where the parts are preheated and then dipped in a bath of molten salt that is maintained at a temperature slightly above the melting point of the brazing metal.