Fusion-welding Process (Gas and Arc Welding)

8/10/2019 Fusion-welding Process (Gas and Arc Welding)

1/27

Fusion-welding Process

Oxyfuel-gas welding

Electrodes arc weldingElectron beam welding


2/27

General characteristic of fusion-

welding Process

Joining

ProcessOperation Advantage

Skill level

required

Welding

position

Current

type

Distortion

*

Typical

cost of

equipmen

t ($)

Oxyfuel ManualPortable

and flexibleHigh All - 2-4

Low

(500+)

*1=highest; 5=lowest

Source: Serope Kalpakjian, Manufacturing Engineering and

Technology


3/27

Oxyfuel-gas welding

Abbreviation OFG

It uses a fuel gas combined with oxygen to

produce a flame at high temperature to melt

the metals at joint.

The most popular welding process is

acetylene, also known as oxyacetylene-gas

welding (OAW)


4/27

C2H2 + O2 -> 2CO + H2+ Heat

Primary combustion process

2CO + H2+ 1.5O2 -> 2CO2+ H2O + Heat

Secondary combustion process


5/27

Types of flame

The proportional of acetylene and oxygen in the gasmixture is an important factor in oxyfuel-gas welding.

(a) At neutral flame, the ratio of oxyfuel-gas welding is

1:1.(b) When higher oxygen supply, the flame can be harmful

for steel because it oxidizes the metal. Known asoxidizing flame

(c) If oxygenis insufficient, the flame is known asreducing, or carburizing flame. Suitable for lowmelting welding material.


6/27

TYPES OF FLAME


7/27

The principle of the OGW


8/27

Filler metals used to supply additional metal

to the weld zone during welding, and may be

coated with flux.

The purpose of the flux is to retard oxidation

of the surfaces of the parts being welded.

The slag development protects the molten

puddle of metal against oxidation as the weld

cools.


9/27

Welding Practice and Equipment

OGW can be used with most ferrous and non-

ferrous metals for almost any workpiece

thickness, limit to 6mm less.

The equipment for OGW consists of a welding

torch, proper goggle, face shields for safety

measures.


10/27

General view and cross sectional of a

torch


11/27


12/27

Other type of gas welding

Pressure gas welding

Termit welding


13/27


14/27

Thermit welding


15/27

Also known as thermite or exothermic welding

Involves mixing a metal powder with a metal

oxide and apply a high temperature ignition

source to cause an oxidation-reduction

reaction. The temperature can reach up to

2500oC.

Also combined with aluminum powder


16/27

Application of thermit welding

1 2 3

4


17/27

Electrodes for Arc Welding

Electrodes for consumable arc-welding process

are classified according to following properties:

Strength of the deposited weld metal

Current (AC or DC)

Type of coating


18/27


19/27

Specifications for electrodes and filler metals(including dimensional tolerances, quality controlprocedures, and processes) are published by the

American Welding Society (AWS) and theAmerican National Standards Institute (ANSI).

Some specifications appear in the AerospaceMaterials Specifications (AMS) by the Society of

Automotive Engineers (SAE). Electrodes are sold by weight and are available in

a wide variety of sizes and specifications.


20/27


21/27

Example of mild steel coated electrode

table


22/27

Functions of electrode coating

Stabilizethe arc.

Generate gases as a shield against thesurrounding atmosphere.

Controlthe rate at which the electrode melts

Act as a flux to protect the weld against theformation of oxides, nitrides and other

inclusions. Add alloying elements to enhance the

properties of the joint.


23/27

Electron-beam welding

Or called (EBW), developed in the 1960s.

Heat is generated by high velocity, narrow-beam

electrons.

Requires special equipment in order to focus the

beam on the workpiece, typically in a vacuum.

The higher the vacuum, the deeper the beam

penetrates, the greater the depth-to-width ratio

There are 3 methods; EBW-HV, EBW-MV, EBW-NV


24/27

Almost any metal can be welded andworkpiece thickness range from foil to plate.

Capacities of electron beam guns range up to

100kW. This process has a capability of making high-

quality welds that are almost parallel sided,

are deep and narrow. It can process any metal (butt and lap) with

thickness up to 150 mm.


25/27

Application of EBW


26/27

Results of EBW work


27/27

References

Serope Kalpakjian, Manufacturing Engineering

and Technology, 7thedition.

Some pictures are taken from the Google

Images.

Fusion-welding Process (Gas and Arc Welding)

Documents

Transcript of Fusion-welding Process (Gas and Arc Welding)