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Compare Soldering and Brazing process

We have seen the overview of a welding process, Arc welding process, Gas welding process types of flames in Gas welding and Difference between Arc welding and Gas welding and difference between DC  welding and AC welding with the help of our previous posts.

Let us get more in depth and understand the soldering and brazing process with the help of this post.


Soldering

It is basically a process of joining similar or dissimilar metals by means of a fusible filler metal (or alloy) called solder which is applied in the molten stage.

The soldering process is divided into two types i.e. soft soldering and hard soldering 


Soft soldering

Soft soldering is basically used to join thin metals like sheet metals. It requires a lower heating temperature i.e. below 150 degree Celsius. Soft solder is any alloy of lead and tin. It is also used to join small wires. The strength of soldering is low.


Hard soldering 

It has a high melting temperature, which ranges from 600 degree Celsius  to 900 degree Celsius. Solder is made of copper, silver, tin, lead and their alloys. Usually, silver soldering is preferred over hard soldering. The strength of hard soldering is more than that of soft soldering.


The melting temperature of the soft solder is about 350 to 370 degree Celsius and that of the hard solder is about 600 to 900 degree Celsius. But the melting temperature of the solder will  always be lower than the melting temperature of joining metals.



Soldering accessories


There are following soldering accessories as mentioned below


Solder

It is the filler metal used for joining processes in soldering. It is made up of an alloy of lead

and tin. It contains about 45% to 60% of tin. The tin gives greater strength and corrosion resistant property. 



Soldering iron

It is the equipment used in the soldering process for heating the workpiece to just above the melting temperature of solder. It is a steel rod containing a wooden handle at one end and tapered copper tip at the other end.


Copper has the property of absorbing and distributing the heat. The soldering iron is heated by

electric current or a heating source like a furnace. 



Flux

It is used to prevent the formation of oxides. The flux improves the quality of soldering. Zinc chloride is the most common flux used in the soldering process. The flux is spread on the joint by using a soldering iron. Some of the other fluxes are rosin, rosin plus, alcohol and ammonium chloride. 



Soldering process


First of all the joining surfaces will be cleaned thoroughly. Then the joining portions of the metals will be positioned to get the required type of joint. The flux will be then applied over the joining portions and the soldering portion of the surface will be heated to a temperature just above the melting temperature of solder.


When the solder, carrying the electric power supply, is touched on the heated surface, the

solder melts and flows into the cavities of the joining surfaces completely and gets solidified and the required soldering is done.


Following figure displayed here indicates the soldering process. 


Brazing


It is the process of joining two thin metals. Following figure shows the brazing process. It is used for joining two similar or dissimilar metals by means of hard non-ferrous metal called shelter, but the workpiece is not melted. Brazing is used for joining pipes and fittings, carbide tips on tools, etc. 


A spelter is a harder filler rod, having temperature below the melting temperature of base metal. It is commonly made of copper base and silver alloys. The molten spelter flows into the small cavities of the joining surfaces completely and it is solidified. The heat required for brazing tools is obtained from gas or electric current. 


We will see the Common defects in welding in our next post. 


Reference 

Engineering Practices by Mr. S. SUYAMBAZHAHAN 

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