What is Soldering & Solder and Flux? Fully Knowledge Of( Types of solders, Soldering Equipment's, Hard Solder (or) Brazing, Types of Fluxes

 What is Soldering ?

1- Soldering is a process of giving a permanent nature to a joint of wires. 

2- Unsoldered joints become loose and oxidized after some time and cause sparking. 

3- It is necessary to ensure that the melting point of the metal to be soldered should be high enough than the melting point of the metal used as a solder. 

4- Soldering is a process in which a metal or a metal alloy having a low melting point is filled in a pre heated joint in the molten state. 

5- This molten metal alloy fills the blank space of the joint and make the joint permanent. 

6- The process of soldering is quite easy and it requires a little practice only.

Metals used for making solders 

1- Generally, a solder is an alloy metal which melts at a low temperature. An alloy metal is a mixture of two or more metals. 

2- The metal and its percentage in the mixture depends on its use. 

3 There are two main types of solders which are as follows, 

1- Hard solder,

 2- Soft solder 

 Hard solder

1- The solder which has a high melting point is called a hard solder. 

2- It is used on the metals which have high melting points, copper, brass, iron, steel etc., 

3- A hard solder is of following two types • 1- Spelter Solder, 2- Silver solder

Spelter solder 

1- It may have any one or the three following compositions.

i- Copper 50% and zinc 50% or copper 67% and zinc 33%. 

ii- Copper 50%, zinc 37% and tin 13%. 

iii- Copper, zinc and cadmium. 

Silver solder .

1- It has a lower melting point in comparison to the spelter solder. 

2- It may have any one of the four following compositions 

i- Copper 33% and silver 67%. 

ii- Copper 20%, zinc 10% and silver 70%. 

iii- Copper 20%, silver 10% and gold 70%. 

iv- Copper 35%, zinc 55% and nickel 10%.

Soft solder 

1- It has a low melting point in comparison to the hard solder.

2- It is used for soldering on small joints of copper or aluminum. 

3- It can be melted easily with a soldering iron. 

4- It is a mixture of mainly tin and lead. 

5- The percentage of tin in the solder decides its melting temperature. 

6- A solder having less percentage of tin requires a high temperature for melting and a solder having more percentage of tin requires a low temperature for melting. 

7- The following table shows different percentage of tin and lead in a solder and their melting points.

8- The above mentioned solders are used on copper joints. The solder used on aluminum joints comprises tin 70%, zinc 25%, aluminum 3% and phosphor tin 2%.

Soldering Equipment's 

O Soldering iron. 

O Soldering heater.

Soldering iron 

1- Heated by solid or gaseous fuel or electric heater. 

2- Soldering iron consists of copper point or bit. 

3- It is usually made up of square or rectangular cross-section. 

4- A stem is made of mild steel and wooden handle.

Point

Soldering iron

 O It is a size chosen to suit the class of work. 

Purpose Soldering iron

1- To absorb the heat while in the fire or muffle and give this out when applies to the job. 

2- Heating the two parts and melting the solder. 

3- The point is tinned (covered with solder) and kept clean. 

4- When applying the iron, it must be held in position for long time to attain the required temperature of work. 

5- Then drawn slowly over the surface. 

6- It will heat the adjoining area and melt the solder. 

7- The stem forms the connection between the point with it's heat as high conductivity and handle with low conductivity (which permits tool to allow easily manipulated).

Soft solder 

1- When a small assemblies have to be soft soldered, an electrically heated iron is most useful.

2- It is better than solid (or) gaseous fuel, for heat. 

Soldering heater 

1- It is used for heating the soldering bit, for accomplishment of soldering operation.

Soft Solder Definition

1- It is the material used for joining of the metals by means of heat and a filler metal. 

2- The melting point is lower than 420°C and less than that of melting point of the base metals. 

3- Method of alloys being joined is known as soft soldering. 

Soft Soldering Definition

1- It is a process for joining small intricate parts having low melting points which damages when soldering process is carried out at high temperature. 

2- It uses tin-lead alloy as filler material and it uses gas torch as the heat source.

Applications of Soft Solder 

1- Soft solder is used for most engineering materials Ex: Iron, steel, copper, brass, nickel, monel can be joined. 

2- Making electrical connections .

3- Hermetic sealing of metal containers.

4- Joining lead pipe.

5- Copper tubing .

6- Filling of casting imperfections.

Different Methods of Soft Soldering 

1- There are three different methods of soft soldering on copper wire joints, which are as follows, 

i- By electric soldering iron.

ii- By blow lamp.

iii- By soldering cup and ladle.

Soft soldering By electric soldering iron 

1- A soldering iron has a copper bit which is heated by an element. 

2- When electric current is passed through the element of a soldering iron then it starts heating up. 

3- Within few minutes the tip of the bit becomes ready for soldering. 

4- Usually, a 125 watts soldering iron is used for soldering the joints of copper wires. 

5- A soldering iron should not be over heated because this will make it difficult to solder a joint.

6- An overheated soldering iron should be cooled down for a minute or two before soldering. 

7- A test can be made by applying a little quantity of flux on the bit. 

8- If the flux produces a dense smoke then the soldering iron is considered to be overheated. 

9- The soldering iron is put on the joint and the joint is allowed to be heated up. 

10- Now a little quantity of flux is applied and then the solder wire is melted on it. 

11- The molten solder fills the blank space of the joint. In this way, whole joint is soldered from one end to the other gently. 

12- The lumps of solder are removed from the joint with the soldering iron or with a file. 

13- The joint may be cleaned with a wet cloth after soldering so as to make it lustrous. 

14- Remember it that for a fine soldering the soldering iron should not be under heated or over heated.

Soft soldering By blow lamp 

1- This method is used for soldering on big joints of wires and cables. 

2- For this, first of all, the joint is heated from all sides in the blue flame of the blow lamp. 

3- After it, a little quantity of resin flux applied on the joint and then the solder wire is melte on it. 

4- The molten solder covers the joint and fills the blank spaces, The joint should led upto a proper temperature for a good soldering. 

5- The soldering should be done quickly, because the blow lamp heats up the joint within a short time.

Soft soldering By soldering cup and ladle 

1- In this method, the solder is melted in a soldering cup on a stove. 

2- The solder should be heated to a reasonable temperature because an overheated solder is not suitable for soldering. 

3- For a simple test of overheating of solder, a small price of wood is dipped in the molten solder. 

4- If the wood starts burning then the solder is overheated and if it smokes only then the solder is considered to be fit for soldering. 

5- Now, a little quantity of flux is applied on the joint and the molten solder is dropped with a ladle on the joint while the soldering cup is kept below the joint. 

6- The process is repeated two three times so that the whole joint is covered with the solder. 

7- The lumps of solder are removed with a cloth quickly.

8- Joints having a diameter or 15 mm or more can be soldered by this method, the joint may be cleaned with a wet cloth after soldering so as to make it lustrous. 

Precaution 

1- The molten solder should be shake continuously otherwise the lead being heavy in weight will deposit in the bottom of the soldering cup and only tin will be applied to the joint. 

2- In this way, the soldering will not be proper.

Soldering of the Aluminum joints .

1- In this way, the soldering will not be proper. The method of soldering on aluminum is the same as on copper joints but the solder and the flux used for soldering are quite different. 

2- The solder used is 'Alta P' or 'Alta Z'. It melts on 160°C. The flux used is 'Eyer 7' or "Kynal'.

3- The joint is cleaned with an emery cloth or a sand paper and then the flux is applied on the joint immediately. 

4- Now, soldering is done by any one of the methods described above but the 'soldering cup and ladle' method is best for good results. 

5- Tinned copper ferrule and sockets are used on aluminum joints. 

 Precaution 

1- The flux used for soldering on aluminum joints evolve poisonous gases, therefore, care should be taken that the smoke may not enter the nose or the eyes. 2- The soldering should be done in an open space.

Hard Solder (or) Brazing 

1- A hard solder is an alloy of copper and zinc. In metals at a very high temperature. 

2- Hard soldering is used for joining brass, copper, iron and steel. 

3- The most important application of hard solders is in power apparatus for making permanent connections, for joining metals such as copper, silver, gold and alloys such as brass, gun metal etc., 

4- The hard solder is called brazing solder when applied to copper, iron, brass etc., and is called silver solder when applied to precious metals like silver, gold etc.

5- The solders which fuse only at red heat and so can be used metals which can withstand that temperature such as iron, copper, brass and gun metal. 

6- Usually, they are copper zinc alloys. For brass work, the proportion is 1 to 1 and for copper and iron the proportion is 3 copper to 2 zinc. 

7- Hard solders have high melting point. Their common use is for making connections in power apparatus. 

8- The important properties of such solders are given as follows.

Flux Usage of Hard Solder

1- To prevent oxidation. 

2- To clean the soldering surface. 

Types of Fluxes Use Hard Solder

1- Acid .

2- Rosin .

3- Acid flux is contains organics salts. 

4- Rosin flux is produced from turpentine and water soluble compounds.

Why Fluxes Used in Hard Soldering?

1- Soldering flux is a solution used to clean metal surfaces before they are soldered together. 

2- Its essential function is to deoxidize the surface of the metal without decomposing, because any oxides allowed to remain on the surface of the metal might cause poor solder connections. 

3- The fluxes are used, 

  i- To assure metallic contact between the solder and the base metal. 

  ii- To secure good adherence to the base metal surface. 

 iii- To prepare for the wetting of the metal surface with the molten metal. 

Action of flux used in Hard soldering

1- If flux is dry, it is mixed prior to its application with water or with other solvents. 

2- On heating during soldering, the water or the solvents gets evaporated. 

3- The molten flux forms a protective coating over the clean metal. 

4- Also dissolves oxides off the top of liquid solder which then wets the base metal.

What is the Classification of fluxes ?

1- Fluxes are classified into three types, 

i- Rosin fluxes or non corrosive fluxes 

ii- Inorganic fluxes or corrosive fluxes 

iii- Organic fluxes or mild fluxes 

Rosin fluxes or non corrosive fluxes 

1- Rosin fluxes are named for their primary ingredient, rosin. 

2- Some of the rosin fluxes are, i - Rosin. ii- Rosin plus alcohol  iii- Tallow and olive oil 

3- These fluxes leave residue which are hard and non conducting.

4- Three main types of rosin flux are used, 

i- Rosin (R) flux.

ii- Rosin mildly activated (RMA) flux and 

iii- Rosin activated (RA) flux .

5- Each of these have a different level of activators, which are the agents that allow the flux to deoxidize and clean. 

6- Applications of non corrosive fluxes, • 

i- Used for copper, brass, tin, cadmium and silver plates. 

ii- Rosin is used in electrical works. 

iii- Tallow is used with lead.

Inorganic fluxes or corrosive fluxes 

1- These fluxes consists of inorganic salts and acids. 

2- Generally fluxes consists of zinc and ammonium chloride and are also added sodium or potassium chloride. 

3- This flux works by either dissolving the oxide or partially lessening the oxide particles and floating them off into body of flux. 

4- After soldering there is need to remove flux residue. 

5- Applications of corrosive fluxes,

 i- Copper alloys.  ii- Low carbon steels .

 iii- Low alloy steels . iv- Stainless steels.

Organic Fluxes or Mild Fluxes 

1- These are mild organic acids such as stearic acid, oleic acid, lactic acid and benzoic acid. 

2- These fluxes provides a good fluxing action as corrosive fluxes, but they leave very less flux residue. 

3- After soldering there is no need to remove flux residue. 

4- Application of mild fluxes, 

i- Organic fluxes are very useful in applications where controlled quantities of flux can be applied. 

ii- Sufficient heat can be used to fully decompose or volatilize the corrosive constituents.