soldering, brazing and welding

8/13/2019 Soldering, Brazing and Welding

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ELEMENTS OF MECHANICAL

ENGINEERING (10 EME 14/24)

UNIT 7 : SOLDERING,BRAZINGANDWELDING.

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INTRODUCTION

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Some products cannot be manufactured as a single piece. Thedesired shape and size of such products can be obtained byjoining two parts of same or different materials. These parts aremanufactured individually and are joined together to obtain thedesired product.

Metal fabrication involves joining of two metals together. Variousprocesses are used to join the metals together depending onthe strength of the joint, material and thickness of the workmetals and other several factors. Metal Joining processes aregenerally classified as:

1. Welding

2. Soldering

3. Brazing

4. Mechanical Fasteners like bolts, nuts, rivets, screws etc.

5. Adhesive bonding.


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WELDING

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DefinitionWelding is a fabrication process of joining two similar or

dissimilar metals by heating them to a suitable

temperature and then fusing them together with or

without the application of pressure and filler metal.

Types

1. Plastic or Pressure Welding (Under pressure without

additional filler metal)2. Fusion or non-pressure welding (With additional filler

material)


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ARCWELDING

Working principle:Arc welding is a fusion welding process and basically works

on the principle that the intense heat produced by an

electrical arc struck between the electrode (filler rod) and the

work metal is used to join the two metals. In this weldingprocess the electrical energy is converted into heat energy

producing a temperature of around 50000C in the welding

zone. The high temperature of the electric arc melts the base

metal and at the same time the tip of filler metal also melts

and mixes with molten base metal to form the weld metal.

The weld metal cools and solidifies to form the weld.

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CONSTRUCTION

The constructional details of an arc welding machine are as follows:

Power supply

Insulated cables

Electrode holder and Clamping system

Electrodes

The two types of electrodes used in arc welding are:

1. Consumable electrodes

2. Non-consumable electrodes

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WORKING

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OXY-ACETYLENEWELDING

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Principle of operation:

Oxy-Acetylene Welding is basically a fusion type of gas

welding process, in which a flame produced by the

combustion of gases is employed to melt the metal. By

burning acetylene in combination with right proportion of

pure oxygen, in a welding torch, a flame upto 35000C can be

attained. As in arc welding, a filler metal is used to fill the

joint. The molten metal is allowed to flow together thus

forming a solid continuous joint upon cooling.


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CONSTRUCTION

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Gas cylinders

Pressure regulators

Pressure gauges

Welding TorchHoses


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TYPESOFOXY-ACETYLENEFLAME

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The flame temp. is not uniform throughout the entire length of the

flame, indeed it varies with the gas composition. There are three

kinds of flame:

1. Neutral Flame

2. Oxidizing Flame

3. Carburizing Flame


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SOLDERING

Definition:Soldering is defined as the method of joining two

similar or dissimilar metals by using another low temp.

metal alloy called solder under the application of heat.

Types:

Soldering is classified into,

1. Soft Soldering

2. Hard Soldering

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WORKINGPRINCIPLE

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The surfaces to be joined are cleaned and are placed on each

other. A flux is employed to prevent oxidation. The solder is heated

by soldering iron and the molten filler metal is made to flow between

the two closely placed adjacent surfaces by the capillary action. Inthe soldering process only the solder melts and the workpieces

does not.

Though soldering results in a good joint between the two plates,

the strength of the joint is limited. The soldered joints are not

suitable for high temperature applications because of the lowmelting temperatures of the filler metals used.


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METHODOFSOLDERING

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The following operations are required to be

performed sequentially for making soldered joints.

1. Shaping and fitting of metal parts together

2.

Cleaning of surfaces3. Application of flux

4. Tinning

5. Application of heat

6. Cooling and final clean up


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BRAZING

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Definition:

Brazing is defined as the method of joining two

similar or dissimilar metals by using a non-ferrous

fusible filler metal called spelter (having melting

point lower than that of the base metal) under the

application of heat.

Types:

Brazing is classified into,

1. Gas Torch Brazing

2. Furnace Brazing

3. Dip Brazing

4. Electrical Brazing


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WORKINGPRINCIPLE

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The surfaces to be joined are cleaned and are placed in joining position.

A flux is employed to prevent oxidation. The part to be joined is heated

and the molten filler metal is made to flow between the two closelyplaced adjacent surfaces by the capillary action. If a large gap is

present, capillary action will not take place and the joint will not be

strong

Brazing gives a much stronger joint than soldering. The principal

difference is the use of a harder filler material commercially known asspelter. The spelter is usually an alloy of copper, zinc and tin.


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METHODOFBRAZING

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The following operations are required to be performedsequentially for making soldered joints.

1. Cleaning and preparing the surface to be brazed.Cleaning may be done by wire brushing, filing orgrinding.

2. Coating the surface of both base metal and the fillermetal with a flux.

3. The parts are aligned, held in right position andclamped.

4. Heating the joint using a blow torch or other suitable

mean in the presence of the filler metal.5. Filler metal melts and fills the joint by capillary action.

6. The joint is allowed to cool and later is cleaned with asolvent to remove the left out flux.


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COMPARISON BETWEEN WELDING,

SOLDERING AND BRAZING

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COMPARISON BETWEEN WELDING,

SOLDERING AND BRAZING

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THANK

YOU

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soldering, brazing and welding

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