Plasma arc welding

© Pearson & GNU Su-Jin Kim© Pearson & GNU Su-Jin Kim

Welding & JoiningWelding & JoiningManufacturing ProcessesManufacturing Processes

Plasma arc welding

• A concentrated plasma arc is produced and directed toward the weld area.

• Higher quality and speed than the TIG.

Plasma AW

http://www.youtube.com/watch?v=jo376zPns8I



Plasma cutting

http://www.youtube.com/watch?v=mJJydOxHwZU&feature=results_main&playnext=1&list=PL8EE6E5350B31D89B

Negativeelectrode

Cutting gas

-

+

Shielding gas

Plasma channel

Positive metal

• Plasma: gas -(heat)> plasma ( +ions + -electrons )• Focused stream of plasma cut sheet metal.• Cutting speed ≈ efficiency, power / thickness, specific

heat, melting point : v ≈ η P / (t w c Tm)



Electron-beam Welding• Kinetic energy of high-velocity electrons is converted

into heat to strike the workpiece.• The higher the vacuum the more the beam will be able

to penetrate the part and the greater depth-to-width ratio.

http://www.youtube.com/watch?v=NONurFigP5I



Laser-beam welding

• Uses a high-power laser beam as a heat source to produce a fusion weld.

• Has a high energy density and a deep penetrating capability.

http://www.youtube.com/watch?v=51d6gQxg1KI



Laser-beam Cutting

http://ma.gnu.ac.kr/vod/Machining/Laser_beam_machining.MP4

• High power (kW) laser melts and evaporates material.• CO2 & Nd:YAG lasers are used for industrial cutting.

Mirror

XenonFlashlamp

Nd:YAGcrystal

Laser

Mirror



Laser Welding Machine

• Multi axis machine used for laser cutting, welding, marking.

http://ma.gnu.ac.kr/vod/Joining/Laser_Welding.wmv Machine



Laser-beam Cutting

• Standard roughness material thickness / laser power, ∝cutting speed : r ∝ t0.5 / (P0.5 v0.3)

• Cutting rate ≈ laser power / evaporation energy per volume, thickness, width of laser: v ≈ P / (e t w)

Laser beam

Focusing lens

Gas

Material

wt



Laser drill

• Non-contact, a wide range of materials, accuracy and consistency, as small as 10 – 20 microns.

Aerospace part: http://www.youtube.com/watch?v=83OQTZZ4ML8

Glass: http://www.youtube.com/watch?v=CS60VzAkhxk



Resistance Welding( 전기저항용접 )

• Welding is produced by means of electrical resistance between 2 joined members.

• Heat generated is RtIH 2 H = heat generated (J)I = current (A)R = resistance in ohmst = time (s)



Resistance Welding

• Contact resistance of electrode-workpiece < Faying surface resistance of workpiece surface

• Pressure reduces contact resistance and is increased after solidification for forging

• Rapid, small heat affected zone, no filler, high reliability, automation possible

• Mostly lap joint, thickness is limited<12mm, clean interface is needed

• Difficult to weld high conductivity material (Al, Cu)



Resistance spot welding• Tips of the 2 opposing electrodes contact surfaces of lap

joint and resistance heating produces a spot weld.• Good bond in the weld nugget is obtained by having

pressure continually applied till current is turned off.• Strength of weld depends on surface roughness and

cleanliness of mating surfaces.

http://www.youtube.com/watch?v=AwL1CAg43PU&p=9B6D9EAE75875D9D

http://ma.gnu.ac.kr/vod/Joining/Resistance_spot_welding_aluminume.MP4



Resistance Welding

Resistance Seam Welding• Current and pressure is continuous or

on-off through rolls

Resistance Projection Welding• Many welds simultaneously

Rolls

Plates

Electrode



High frequency welding ( 고주파용접 )

• High frequency current up to 450 kHz Localize heat Forge the joint

• Used for pipe and structural beam welding• Small heat affected zone• Highly conductive material can be easily joined (up to 20

mm)

Documents

Plasma arc welding