Brazing, soldering and Adhesives
Brazing:
Brazing is a Multi metal part joining process in which we heated the metal, convert it to liquid and then move it with the help of capillary action to join them.
In brazing, the metal formed is stronger than the individual parts. This occur because of three reasons
1. Because of small part clearance
2. The metallurgical bonding and
3. The geometric construction that is imposed on Bonding
Like welding, brazing is also metals parts joining process but it has some advantage over the welding, some of them are
1. Any metal parts can be joined
2. Less time consuming and
3. Some methods are useful for multiple parts joining having different geometries
4. Brazing can applied to those parts that have a very thin diameter, welding cannot do that for us.
5. Less heat is needed for Brazing as compared to Welding.
Some of the disadvantage of Brazing is
1. Welded joint are more stronger then brazed metal
2. Higher service temperature may weaken the brazed metal
3. Color changes because of Metal conversion to other form and mixing of different color of metals.
It must be noted that not every metal is compatible for mixing with the base metal, here are some of the properties that the filler metal must possess to use as a filler metal
1. Melting temperature must be comparable with base metal
2. Good surface finish
3. Good fluidity
4. Chemical and physical interaction with the base metal
Soldering
Soldering is a process similar to Brazing with the exception of melting point of the metal is less than 450 degree Celsius.
As similar to brazing, the filler metals are melts and transfer to it by capillary action. Filler metal called solder, is added to joints, which distribute between the parts.
In a process called Tinning, the solder is added with a metal known as Tin, which improves its clearance.
As an industrial process, soldering is associated with Electronics assembly.
Some of the advantage soldering has over Brazing and Welding are
1. Low energy needed as compared to Brazing and welding
2. Availability of varieties of heating methods
3. Good conductivity
4. Easy to use and make again, if damage
The disadvantages of soldering are
1. The biggest disadvantage is Low Joint strength unless reinforced by some mechanical means.
2. The soldered metal melts or weaken at higher temperature
Solders and fluxes
Solders and fluxes both is used in soldering process. Both are very important in soldering process.
Solders:
Solders are alloy of tin and lead, both of metals are low melting point. Both Lead and tin has a range of liquids and solidus temperature.
Lead is used in low quality because of its poisonous nature while tin is chemically active and help in welding process. Sometimes silver and antimony is also used in soldering process.
Fluxes:
Fluxes should do the following
1. Molten shape during soldering temperature
2. Remove oxides and other compounds
3. Prevent oxidation reactions on metal surface
4. Promotes wetting
Soldering methods:
Here are some of the methods that is used in soldering
1. Hand soldering
2. Wave soldering
3. Reflow soldering
Adhesive Bonding
Adhesive bonding is a joining technique in which the filler metal holds two or more similar or dissimilar parts together.
Adhesive makes a permanent joint that are less stronger than brazing and soldering. Adhesives bonding have a higher interest in engineering and sciences because of its structural nature.
The strength of adhesive results due to certain mechanism
1. Chemical bonding in which adhesive unite with other adhesives.
2. Physical interaction between primary and secondary atoms of adhesives
Joint design for adhesives:
The following design aspects should take into consideration while designing joint for adhesive
1. The contact area between joints should be maximize
2. While designing stresses and its flow in material must be taken into consideration, so that to avoid
3. Is design in such a way that shear and normal stresses are avoided
Adhesive Types:
Adhesive have three types
1. Natural
2. Inorganic
3. Synthetic
Natural adhesives are derived from other natural compounds such as plants and animals. They are gums, dextrin’s and collagen.
Inorganic adhesives are derived from inorganic compounds such as sodium chloride or supplants. They have high melting and boiling points.
Humans manufacture synthetic adhesives, some mechanism are
1. Mixing different catalyst with different compounds
2. Heating a chemical compound
3. By Ultra violet radiation
4. By evaporating water from water containing compound
