7 Main differences between brazing and soldering (Simplified)

People often ask about what is the basic difference between brazing and soldering. They jointly represents one of the several methods used for joining two or more metal pieces using an alloy(used as filler rods). which is used to stick them together with proper strength. Both of them involve heating the filler metal and joint surfaces. The major difference between soldering and brazing is that the temperature at which the method is being performed.  Let’s take a deep look into the two methods.

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What is soldering?

Soldering is define as a group of joining processes where coalescence is produced by heating to a suitable temperature and by using a filler metal having a melting point not exceeding 800⁰ F(427⁰C) and below the melting point of the base metals. The filler metal is usually distributed between the properly fitted surfaces of the joint by capillary action. The traditional tool for soldering is the soldering iron with a copper tip (it has high thermal conductivity) which may be heated electrically or by oil, coke or o gas flame.

Various soldering methods are –

• Soldering iron method
• Torch method
• Dip metal method
• Spray method

Classifications of soldering:

Soldering is divided into two classifications: soft and hard

Soft soldering is used extensively in sheet metal work for joining parts that are not exposed to the action of high temperature and are not subjected to excessive loads and forces. This is also employed for joining wires and small parts.

The solder is mostly composed of led and tin. This has a melting range between 150 to 350⁰C. A suitable fluxing is always used in soft soldering. The function of this is to prevent oxidation of the surfaces or to dissolve oxides that settle on the metal surfaces during the heating process.
 A blow torch or soldering iron constitutes the equipment for heating the base metals and melting the solder and flux.

Hard soldering solders melt at high temperatures and are stronger than those used in soft soldering. A common method is silver soldering. In this method silver alloyed with tin is used as solder.
In hard soldering the temperature for various soldering varies from 600 to 900⁰C. In this process the fluxes are mostly in paste form.

Also read : What is shielded metal arc welding ?

What is brazing?

Brazing involves the melting of a comparatively low melting point filler material against the base metal pieces to be joined while they are clean and free from oxides, oil, grease etc. It is not necessary to melt the base metal.

Function of the filler metal

• It wets the base metal surfaces
• Spreads along the joint by capillary action
• Adheres and solidifies to form the brazed joint.

The flux which is employed during brazing melts at a lower temperature bend the brazing filler material. It wets the surface to be brazed, removes the oxide film and gives clean surface.
The filler metals used in brazing are of copper base alloys and silver base alloys. For brasses up to 20% tin are mostly used mainly for the brazing of the ferrous metals. Silver alloys(silver and copper or silver, copper and zinc) having a melting range of 600 to 850⁰C are suitable for brazing any metal.
Like soldering the parts to be brazed are carefully cleaned, the flux applied, and the clamped in position for joining process. Borax is mainly used as flux and heated to a temperature above the melting point.  

Other fluxes are-

• Sodium, potassium and lithium borax compounds which is used in high temperature melting point fluxes
• Chlorides
• Boric acid (mainly employed as a cleaning agent)

Brazing procedure:

The procedure includes the following steps-

• Cleaning and preparing the surface to be brazed
• Fluxing the base metal and filler metal surfaces.
• Aligning the base metal parts to be joined
• Heating the joint
• Applying brazing filler metal on to the joint
• Cooling of the joint
• Removing flux residue from the completed joint

Various brazing process used:

• Torch
• Vacuum
• Induction
• DIP
• Resistance

What is the difference between brazing and soldering ?

Brazing is essentially similar to soldering, but it gives much stronger joint than soldering. The main difference is the use harder filler material which is commonly known as spelter.

The key differences between brazing and soldering are discussed below.

1.Temperature: Filler metal used in soldering as a melting point less than 800⁰F(427⁰c) whereas that in brazing has melting point above 800⁰F(427⁰c)                                                                

2.Strength: Brazing joints are stronger than soldering.

3.Corrosion resistance: Solder joints do not resist corrosion to the some extent that brazed or welded joints do.

4.Application of brazing and soldering: Soldering is mainly used in the electrical industry for permanent connection between the electronic components; it is commonly used in electronics, arts and crafts, and metal work from flashing to jewelry. It is mostly used to join wires to leads of components such as switches.

5.Cost: Soldering is a cheap process. Brazing is quite costlier.

6.Preheating: Preheating of base metal does not require in soldering. Preheating requires in brazing.

7.Types of metals : Soldering is possible only in similar sheet metals as well as thin metals.

Brazing is suitable in similar or dissimilar as well as thicker metal parts.

Difference of soldering and brazing in tabular form:

Summary of brazing and soldering

Both brazing and soldering are the common methods of joining two or more similar or dissimilar metals using filler metals. Both of the methods are similar to each other, the basic difference is that soldering process is done using filler metals less than the temperature of 800⁰F. whereas brazing is carried out at temperature above 800⁰F. Soldering is mainly used in electronic industry for joining electronic wires and components and brazing is mainly used to join all kind of metals in industry such as automotive industry. It takes comparatively more heat than any other soldering process.