Manufacturing Process -Joining Process & Equipments (Fusion Welding)

MMAANNUUFFAACCTTUURRIINNGG PPRROOCCEESSSS(BMFG 2323)(BMFG 2323)

Lecture 4

JOINING PROCESS & EQUIPMENT(FUSSION WELDING PROCESSES)

• Joining and assembly of two or more parts so that they can function reliably.

• Ex. Pens, bicycles, chairs, cars, etc.

• Aspect of manufacturing:1. Impossible to manufacture as a single product

e.g chairs, computers, etc.2. More economical to manufacture as individual

components, which are then assembled e.g 3. For maintenance or replacement purposes e.g. car

accessories and engines.4. Different materials due to different properties

requirement e.g. cooking pots and pans.5. Ease and less costly of transportation e.g. bicyle.

INTRODUCTIONINTRODUCTION

JOINING PROCESS & EQUIPMENTJOINING PROCESS & EQUIPMENT 1

@jurie 2007 – Lecture 4

1 - Welding.

2 - Soldering & brazing.

3 - Mechanical fastening.

4 - Adhesive bonding.



INTRODUCTIONINTRODUCTION



Joining Processes

Welding Adhesive BondingMechanical

Fastener

Fusion Brazing & Soldering Solid State

Chemical Electrical Electrical Chemical Mechanical

Oxyfuel

ThermitArc

Resistance

Electron Beam

Laser Beam

Resistance Diffusion

ExplosionCold

Friction

Ultrasonic

Fastening, Seaming

Crimping, Stitching

1. Processes in which two pieces are joined together by the application of heat, which then melts and fuses the interface.

2. Heat required obtained from electrical energy.

3. The process involves either a consumable or a non consumable electrode.

4. Filler metals (which are metals added to the weld area during welding) may or may not be used.

WELDINGWELDING



FUSION WELDINGFUSION WELDING



- Defined as the melting together & coalescing of materials.

- Heat usually supplied by chemical or electrical means.

- Filler metals may or may not be used.

- Comprised of consumable & non-consumable electrode arc welding and high energybeam welding processes.

SOLID STATE WELDINGSOLID STATE WELDING- Joining takes place without fusion.

- No liquid (molten) phase involved in the joint.

WELDINGWELDING



BRAZING AND SOLDERINGBRAZING AND SOLDERING

- Brazing: uses filler metals & involves with lower temperature compare to welding.

- Soldering: also uses similar filler metals (solders) & involves even lower temperature.

ADHESIVE BONDINGADHESIVE BONDING

- Requiring strength, sealing, thermal & electrical insulating, vibration damping, andresistance to corrosion between dissimilar metals.

MECHANICAL FASTENINGMECHANICAL FASTENING- Involved with traditional methods of joints by using fasteners – bolts, nuts & rivets.

WELDINGWELDINGFUSION WELDING PROCESSES

1) Oxyfuel-Gas Welding.2) Pressure-Gas Welding.3) Arc-Welding

a) No consumable electrode.i) Gas tungsten-arc welding.ii) Plasma-arc welding.iii) Atomic-hydrogen welding.

b) Consumable electrode.i) Shielded metal-arc welding.ii) Submerged-arc welding.iii) Gas metal-ac welding.iv) Flux-cored arc welding.v) Electrogas welding.vi) Electroslag welding.

4) Electron-Beam Welding.5) Laser-Beam Welding.



SOLID-STATE WELDING PROCESSESSOLID-STATE WELDING PROCESSES

1) Cold Welding.2) Roll Bonding/Welding.3) Ultrasonic Welding.4) Friction Welding.

a) Inertia friction welding.b) Linear friction welding.c) Friction stir welding.

5) Resistance Welding.a) Resistance spot welding.b) Resistance seam welding.c) High-frequency resistance

welding.d) Resistance projection

welding.e) Flash welding.f) Stud welding.g) Percussion welding.

6) Explosion Welding.7) Diffusion Bonding.





FUSION WELDING PROCESSFUSION WELDING PROCESS

1) OXYFUEL-GAS WELDING (OFW)

- OFW uses a fuel gas combined with oxygen to produce flame.

- Function of the flame – act as a source of the heat to melt the metals at the joint.

- Common gas welding process uses acetylene (oxyacetylene gas welding – OAW).

- Application: structural sheet metal fabrication, automotive bodies, and various repairwork.

- OAW process utilizes the heat generated by the combustion of acetylene gas (C2H2)in a mixture of oxygen.

- These primary combustion process, occurs in the inner core of the flame, involves thereaction of:

C2H2 + O2 ----------> 2CO + H2 + Heat (1/3 total heat generated in the flame)

- The secondary combustion process involves further burning of hydrogen and carbonmonoxide:

2CO + H2 + 1.5O2 ------------>2CO2 + H2O + Heat (2/3 of the total heat)



(a) General view of oxy torch.

(b) cross-section of a torch used in oxyacetylene welding. The acetylene valve is opened first; the gas is lit with a spark lighter or a pilot light; then the oxygen valve is opened and the flame adjusted.

(c) Basic equipment used in oxyfuel-gas welding. To ensure correct connections, all threads on acetylene fittings are left-handed, whereas those for oxygen are right-handed. Oxygen regulators are usually painted green, acetylene regulators red.

Torch Used in Oxyacetylene WeldingTorch Used in Oxyacetylene WeldingJOINING PROCESS & EQUIPMENTJOINING PROCESS & EQUIPMENT 11


• Flame types1. Neutral – ratio 1: 1, no excess oxygen2. Oxidizing – greater oxygen supply (excess oxygen), harmful for

steel due to oxidizes. Only suit for nonferrous metal e.g copper & copper based alloys.

3. Carburizing – insuffient of oxygen (excess acetytelene), low temperature, thus suit for applications requiring low heat e.g. brazing, soldering, flame hardening.

• Filler metals1. To supply additional metal to the weld zone during welding.2. Filler rods or wire and may be coated by flux.3. The purpose of flux is to retard oxidation of the welded

surfaces.



Three basic types of oxyacetylene flames used in oxyfuel-gas welding and cutting operations: (a) neutral flame; (b) oxidizing flame; (c) carburizing, or reducing, flame. The gas mixture in (a) is basically equal volumes of oxygen and acetylene.

Oxyacetylene Flames Used in WeldingOxyacetylene Flames Used in Welding



PRESSURE GAS WELDINGPRESSURE GAS WELDING

- Involved with two components starts by heating the interface.- Once when the interface begins to melt, the torch is withdrawn.- A force is applied to press both components together and maintain until the interface solidifies.- The joined end with the occurrence of a flash.



ARC-WELDING PROCESSESARC-WELDING PROCESSES

NONCONSUMABLE ELECTRODENONCONSUMABLE ELECTRODE

- In arc welding, the heat is obtained from electrical energy – by using AC or a DC power supply.

- The process involved can be either consumable or non-consumable electrode.

- An arc is produced between the tip of electrode and the work piece which need to be welded.

- The arc produces temperatures ≈ 30,0000C.

-The electrode is a tungsten electrode type.- Need externally supplied shielding gas because of the high temperatures involved in order to prevent oxidation of the weld zone. - For this non-consumable electrode welding process, DC is used and the polarity is important.- For straight polarity which is also known as direct-current electrode negative (DCEN); the workpiece is positive (anode), while the electrode is negative (cathode).- In this case, it will produce welds that are narrow and deep.



- For reverse polarity which also known as direct-current electrode positive (DCEP); the workpiece is negative, and the electrode is positive.

- In this process, weld penetration is less, and the weld zone is shallower and wider.



GAS TUNGSTEN-ARC WELDING (GTAW)GAS TUNGSTEN-ARC WELDING (GTAW)- Also known as TIG welding.- Suitable for thin metals.- This process is expensive because of the cost of inert gas.- Provides welds with very high quality and surface finish.- Filler metal is supplied from a filler wire.- This filler metals are similar to the metal that need to be welded, and flux is not used.- In this operation, tungsten electrode is not consumed, therefore a constant and stable arc gap is maintained at a constant current level.- The shielding gas is usually argon or helium.- Power supply – either DC at 200A, or AC at 500A; depending on the metals to be welded.- Generally, AC is suitable for aluminum and magnesium.- Thorium or zirconium may be used in the tungsten electrodes to improve the electron emission characteristics.- Contamination of the tungsten electrode by molten metal can cause discontinuities in the weld.- Therefore, contact between the electrode with the molten metal pool should be avoided.



Gas Tungsten-Arc Welding (GTAW)Gas Tungsten-Arc Welding (GTAW)



The gas tungsten-arc welding process and its basic equipment, formerly known as TIG (for tungsten inert gas) welding.

PLASMA-ARC WELDING (PAW)PLASMA-ARC WELDING (PAW)- In this welding operation, a concentrated plasma arc is produced and directed towards the weld area.

-The arc is stable and the temperature can reaches up to 33,0000C.- PAW has less thermal distortion, and higher energy concentration – permitting deeper and narrower welds.

- Plasma: it is an ionized hot gas composed of nearly equal numbers of electrons and ions.

- This plasma is initiated between the tungsten electrode and the small orifice by a low-current pilot arc.

- Operating current: usually below 100A.- Filler metal is fed into the arc during the welding process.- There are two methods of plasma-arc welding:i) Transferred-arc method- Workpiece being welded is part of the electrical cuircuit.- The arc transfers from the electrode to the workpiece.ii) Nontransferred method- The arc occurs between the electrode and the nozzle.- The heat is carried to the workpiece by the plasma gas.



- The welding speeds: from 120 to 1000 mm/min.- Can be welded with part thickness less than 6mm.



Two types of plasma-arc welding processes: (a) transferred, (b) nontransferred. Deep and narrow welds can be made by this process at high welding speeds.

ARC WELDING PROCESSES: CONSUMABLE ELECTRODEARC WELDING PROCESSES: CONSUMABLE ELECTRODE

SHIELDING METAL-ARC WELDING (SMAW)SHIELDING METAL-ARC WELDING (SMAW)

- Old method, simplest, held manually.- Most of all industries and maintenance welding currently performed with this process.- The electric arc is generated by touching the tip of a coated electrode against the workpiece.- Need to have a sufficient distance and movement to maintain the arc.- The heat generated, melts a portion of the electrode tip, its coating, and the base metal in the immediate arc area.- The molten metal consists of a mixture of the base metal (workpiece), the electrode metal, and substances from the coating on the electrode; thus this mixture forms the weld when it solidifies.- The electrode coating deoxidizes the weld area and provides a shielding gas to protect it from oxygen in the environment.- The equipment consists of a power supply, cables and electrode holder.- Power supply: can be either DC or AC, ranges between 50 to 300A.- For sheet metal welding, DC is preferred because of the steady arc produces.



Shielded Metal-Arc Welding (SMAW)Shielded Metal-Arc Welding (SMAW)



SUBMERGED-ARC WELDING (SAW)SUBMERGED-ARC WELDING (SAW)

- The weld arc is shielded by a granular flux consisting of lime, silica, manganese oxide, calcium flouride.

- The flux is fed into the weld zone from a hopper by gravity flow through a nozzle.

- The thick layer of flux completely cover s the molten metal and it prevents from spatter and sparks.

- The flux also acts as a thermal insulator by promoting deep penetration of heat into the workpiece.

-The consumable electrode is a coil of bare round wire 1.5 to 10 mm in diameter; and fed automatically through a tube which is called welding gun.

-Electric current: range between 300 to 2000 A.-Power supply: single or three phase power point; rating up to 440V.-Due to flux is a gravity fed type; therefore this welding process is limited largely to welds into flat or horizontal position.

-Circular weld can be made on pipes or cylinders – provided that they are rotated during welding process.

-Suitable for carbon and alloy steel and stainless steel sheet or plates.-Welding speeds: as high as 5 m/min.





Submerged-Arc Welding (SAW)Submerged-Arc Welding (SAW)

Schematic illustration of the submerged-arc welding process and equipment. The unfused flux is recovered and reused.

GAS METAL-ARC WELDING GAS METAL-ARC WELDING (GMAW)(GMAW)- Also known as metal inert-gas (MIG).- The weld area is shielded by an effectively inert atmosphere of argon, helium, carbon dioxide, or other various gas mixtures.- The temperatures generated are relatively low.- Suitable only for thin sheets which is less than 6mm.- The process are economical and can be automated easily.- The consumable bare wire is fed automatically through a nozzle into the weld arc controlled by wire-feed drive motor.- There are 3 types of GMAW process:

i) Spray transfer.ii) Globular transfer.iii) Short circuiting.



Gas Metal-Arc Welding (GMAW)Gas Metal-Arc Welding (GMAW)



Schematic illustration of the gas metal-arc welding process and its basiq equipment, formerly known as MIG (for metal inert gas) welding.

SPRAY TRANSFERSPRAY TRANSFER

- Small size of molten metal droplets from the electrode are transferred to the weld area at a rate of several hundred droplets per second.

- The transfer is spatter free and very stable.- Using high DC current and voltages with large diameter of electrodes.- The electrodes are used with argon or an argon rich gas mixture act as a shielding gas.

GLOBULAR TRANSFERGLOBULAR TRANSFER-Utilizes with carbon-dioxide-rich gases, and globules are propelled by the forces of the electric-arc transfer of a metal, resulting in considerable spatter.

- High welding current are used – greater weld penetration and higher welding speed.

SHORT CIRCUITINGSHORT CIRCUITING-The metal is transferred in individual droplets, as the electrode tip touches the molten weld metal and short circuits.- Low currents and voltages are utilized.- Electrodes are made from small-diameter wire.- Power required: ≈ 2 kW.



ELECTRON-BEAM WELDING ELECTRON-BEAM WELDING (EBW)(EBW)- Can be welded almost any metal; butt or lap welded and the

thicknesses up to 150mm.

- The thickness of the workpiece can range from foil to plate.

- Generally, there is no involvement of shielding gas, flux, or filler metal.

- Distortion and shrinkage in the weld area is minimal.

- Heat is generated by high velocity narrow-beam electrons.

- Capacity of electron guns range up to 100 kW.

- The kinetic energy of the electrons is converted into heat as they strike the workpiece.

- Required special equipment to focus the beam on the workpiece, typically in vacuum.

- The higher the vacuum, the more the beam penetrates, and the greater is the depth-to width ratio, range between 10 and 30.

- Sizes of the welds are much smaller compared to conventional process.

- Parameters can be controlled accurately at welding speeds as high as 12 m/min; this can be done by using automation and servo motor.



LASER-BEAMWELDING (LBW)LASER-BEAMWELDING (LBW)

- Utilizes a high power laser beam as the source of heat.

- The beam can focused onto a very small area, and due to this it has high energy density and deep penetrating capability.

- This process is suitable for welding deep and narrow joints with depth-to-width ratios ranging from 4 to 10.

- The laser beam may be pulsed for a application such as the spot welding of thin materials with power level up to 100 kW.

- Minimum shrinkage and distortion, good strength and generally are ductile and free of porosity.

- Can be automated to be used on a variety of materials with thicknesses up to 25mm.

- Typical metals and alloys welded: aluminum, titanium, ferrous metals, copper.

- Welding speeds: range from 2.5 m/min to as high as 80 m/min for thin metals.



Advantages of LBW over EBW:• A vacuum is not required, and the beam can be transmitted through air.• Laser beams can be shaped, manipulated, and focused optically by using fiber optics, therefore the process can be automated easily.• The beams do not generate x-rays.• The quality of the weld is better than in EBW with less tendency for incomplete fusion, spatter, porosity, and less distortion.



Example of Laser Welding

Laser welding of razor blades.

Comparison of Laser-Beam and Tungsten-Arc WeldingComparison of Laser-Beam and Tungsten-Arc Welding

Comparison of the size of weld beads in (a) electron-beam or laser-beam welding to that in (b) conventional (tungsten-arc) welding.



Manufacturing Process -Joining Process & Equipments (Fusion Welding)

Documents

Transcript of Manufacturing Process -Joining Process & Equipments (Fusion Welding)