Flashcards in Brazing, Soldering, and Adhesive Bonding Deck (21)
How do brazing and soldering differ from fusion welding processes?
Filler metal is used
No melting of the base metals occur
How do brazing and soldering differ from solid-state soldering?
No melting of the base metals
What is the technical difference between brazing and soldering.
Brazing - Filler metal melts at a temp above 450 Celsius
Soldering - Filler metal melts at a temp at or below 450 Celsius
Under what circumstances between brazing and soldering be preferred over welding?
Base metal have poor weld-ability
Components cannot tolerate the higher heat and temperatures of welding
Production rates need to be faster and less expensive than welding
Joint areas are inaccessible for welding but brazing or soldering is possible
High strength of weld joint is not needed
WHat are two joint types most commonly used in brazing?
Certain changes in joint configuration are usually made to improve strength of brazed joints. What are those changes?
butt joints - butting surface areas are increased in various ways such as scarfing or stepping the edges
lap joints - overlap area is made as large as possible.
The molten filler metal in brazing is distributed throughout the joint by capillary action. What is capillary action?
The physical tendency of a liquid to be drawn into a small diameter tube or other narrow openings in spite of the force of gravity
What are desirable characteristics of a brazing flux
low melting temperature
low viscosity when melted
promotes wetting of metal surfaces
protects the joint until solidification occurs
What is dip brazing
A molten salt bath or a molten metal bath accomplishes heating. Assembled parts immersed in the baths contained in a heating pot. Solidification occurs when parts are removed from the baths
Define braze welding
Used for filling a more conventional weld joint. Greater quantity of filler material deposited/ Joint consists entirely of filler metal.
What are some disadvantages and limitations of brazing
the strengths of the brazed joint is generally less than that of a welded joint
High service temperatures may weaken a brazed joint
part sizes limited
Color of the filler metal is often different than the color of the base metals
What is wave soldering
The flow of molten solder onto the underside of a printed circuit board to provide soldered connections between the component leads that projects through holes in the boards and the copper circuit lands on the board
List the advantages often attributed to soldering as an industrial joining process
lower heat energy required
various heating methods
good electrical and thermal conductivity
capable of making airtight and liquid tight joints
ease of repair and rework
What are disadvantages and drawbacks of soldering
.low mechanical strength
elevated service temperatures can weaken joint
What is meant by the term structural adhesive
Capable of forming strong, permanent joints between strong, rigid adherends
An adhesive must cure in order to bond. What is meant by the term curing?
Process by which the adhesives physical properties are changed from a liquid to a solid
What are some of the methods used to cure adhesives
Application of heat and.or pressure
What is an important precondition for the success of an adhesive bonding operation
Surfaces of the adherend must be clean
Adhesives in its initial liquid form must achieve wetting of the adherend surface
Helpful for the surface to be relatively smooth
What are some of the methods used to apply adhesives in industrial production operations
Identify some of the advantages of adhesive bonding compared to alternative joining methods
.process is applicable to wide variety of materials
parts of different sizes and cross sections can be joined
bonding occurs over the entir surface area of the joint
some adhesives are flexible after bonding and are tolerant of cyclic loads and differences in thermal expansions
low temp curing avoids damage to parts being joined
sealing as well as bonding can be achieved
joint design often simplified