Brazing, Soldering, and Adhesive Bonding

Question 1

How do brazing and soldering differ from fusion welding processes?

Answer 1

Filler metal is used

No melting of the base metals occur

Question 2

How do brazing and soldering differ from solid-state soldering?

Answer 2

No melting of the base metals

.

Question 3

What is the technical difference between brazing and soldering.

Answer 3

Brazing - Filler metal melts at a temp above 450 Celsius

Soldering - Filler metal melts at a temp at or below 450 Celsius

Question 4

Under what circumstances between brazing and soldering be preferred over welding?

Answer 4

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

Question 5

WHat are two joint types most commonly used in brazing?

Answer 5

butt joint

lap joint

Question 6

Certain changes in joint configuration are usually made to improve strength of brazed joints. What are those changes?

Answer 6

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.

Question 7

The molten filler metal in brazing is distributed throughout the joint by capillary action. What is capillary action?

Answer 7

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

Question 8

What are desirable characteristics of a brazing flux

Answer 8

low melting temperature

low viscosity when melted

promotes wetting of metal surfaces

protects the joint until solidification occurs

Question 9

What is dip brazing

Answer 9

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

Question 10

Define braze welding

Answer 10

Used for filling a more conventional weld joint. Greater quantity of filler material deposited/ Joint consists entirely of filler metal.

Question 11

What are some disadvantages and limitations of brazing

Answer 11

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

Question 12

What is wave soldering

Answer 12

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

Question 13

List the advantages often attributed to soldering as an industrial joining process

Answer 13

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

Question 14

What are disadvantages and drawbacks of soldering

Answer 14

.low mechanical strength

elevated service temperatures can weaken joint

Question 15

What is meant by the term structural adhesive

Answer 15

Capable of forming strong, permanent joints between strong, rigid adherends

Question 16

An adhesive must cure in order to bond. What is meant by the term curing?

Answer 16

Process by which the adhesives physical properties are changed from a liquid to a solid

Question 17

What are some of the methods used to cure adhesives

Answer 17

Application of heat and.or pressure

Question 18

What is an important precondition for the success of an adhesive bonding operation

Answer 18

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

Question 19

What are some of the methods used to apply adhesives in industrial production operations

Answer 19

brushing

flowing

manual rollers

silk screening

spraying

automatic applicators

roll coating

Question 20

Identify some of the advantages of adhesive bonding compared to alternative joining methods

Answer 20

.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

Question 21

What are some of the limitations of adhesive bonding

Answer 21

joints are generally not as strong as other joining methods

adhesives must be compatible with materials being joined

service temp are limited

cleanliness and surface preparation prior to application of adhesives are important

curing times can impose a limit on production rates

inspection of bonded joint is difficult