Heat Flow in Welding(1)
-
Upload
dhinakaran-veeman -
Category
Documents
-
view
244 -
download
9
Transcript of Heat Flow in Welding(1)
![Page 1: Heat Flow in Welding(1)](https://reader033.fdocuments.us/reader033/viewer/2022061615/577cc9b21a28aba711a45d0b/html5/thumbnails/1.jpg)
Heat Flow in Welding
![Page 2: Heat Flow in Welding(1)](https://reader033.fdocuments.us/reader033/viewer/2022061615/577cc9b21a28aba711a45d0b/html5/thumbnails/2.jpg)
Heat Flow in Welding
Lesson ObjectivesWhen you finish this lesson you will understand:• Heat transfer through the welding arc & factors affecting it• Heat flow in welded parts & conservatio of energy• Thermal profiles around moving heat sources & cooling rates & stresses around welds
Learning Activities1. Read Handbook pp
66-842. Look up Keywords3. View Slides; 4. Read Notes, 5. Listen to lecture6. Do on-line
workbook7. Do homework
Keywords:Conduction, Convection, Radiation, Arc Heat Flow, Thermal Conductivity-Gas, Heat Flux, Fourier’s Law, Conservation of Energy, Moving Heat Source, Thermal Cycles
![Page 3: Heat Flow in Welding(1)](https://reader033.fdocuments.us/reader033/viewer/2022061615/577cc9b21a28aba711a45d0b/html5/thumbnails/3.jpg)
CONDUCTION - Transfer of Thermal Energy between one part of a body and an Adjacent part of the same body or between one body and another which is in physical contact with it.
CONVECTION - Transfer of Thermal Energy through mass movement.
RADIATION - Transfer of Thermal Energy by the emission and absorption of Electromagnetic Radiation.
![Page 4: Heat Flow in Welding(1)](https://reader033.fdocuments.us/reader033/viewer/2022061615/577cc9b21a28aba711a45d0b/html5/thumbnails/4.jpg)
Heat Flow in the Arc
Plasma
Electron
Ion
Neutral Gas Atom
Ionization Free
Recombination T>10,000K
Thermal
Cathode
Anode
Electrons Emitted
Electrons Absorbed
ConvectionRadiation
ThermionicRadiation
![Page 5: Heat Flow in Welding(1)](https://reader033.fdocuments.us/reader033/viewer/2022061615/577cc9b21a28aba711a45d0b/html5/thumbnails/5.jpg)
![Page 6: Heat Flow in Welding(1)](https://reader033.fdocuments.us/reader033/viewer/2022061615/577cc9b21a28aba711a45d0b/html5/thumbnails/6.jpg)
Conduction in the Arc
Plasma
Electron
Ion
Neutral Gas Atom
Ionization Free
Recombination T>10,000K
Thermal
Cathode
Anode
Electrons Emitted
Electrons Absorbed
Argon
Argon
Helium
Helium
![Page 7: Heat Flow in Welding(1)](https://reader033.fdocuments.us/reader033/viewer/2022061615/577cc9b21a28aba711a45d0b/html5/thumbnails/7.jpg)
Turn to the person sitting next to you and discuss (1 min.):• The thermal conductivity of Argon and Helium increases continuously with increasing temperature, but that of nitrogen and hydrogen show a drop in conductivity where the diatomic gas atom dissociates. What do you think would happen if a significant amount of these gases were in the arc plasma?
![Page 8: Heat Flow in Welding(1)](https://reader033.fdocuments.us/reader033/viewer/2022061615/577cc9b21a28aba711a45d0b/html5/thumbnails/8.jpg)
Y t < 0
t = 0
Small t
Large t
T (y,t)
(Initial Transient)
Steady State
![Page 9: Heat Flow in Welding(1)](https://reader033.fdocuments.us/reader033/viewer/2022061615/577cc9b21a28aba711a45d0b/html5/thumbnails/9.jpg)
Y t < 0
t = 0
Small t
Large t
T (y,t)
(Initial Transient)
Steady State
![Page 10: Heat Flow in Welding(1)](https://reader033.fdocuments.us/reader033/viewer/2022061615/577cc9b21a28aba711a45d0b/html5/thumbnails/10.jpg)
sec
sec
sec2
calflowheatAqq
Kcmcaltyconductivithermal
cmcalfluxheatq
dydq
y
o
y
y
dy
Thot
Tcooler
yq
......
dyyq
qq yydyy
dyyq
![Page 11: Heat Flow in Welding(1)](https://reader033.fdocuments.us/reader033/viewer/2022061615/577cc9b21a28aba711a45d0b/html5/thumbnails/11.jpg)
Heat In - Internal Energy + Heat Generated = Heat Out
capacityheatCdensity
QGeneratedHeat
AdytTCEnergyInternal
AqInHeat
p
gen
p
y
.
dd
![Page 12: Heat Flow in Welding(1)](https://reader033.fdocuments.us/reader033/viewer/2022061615/577cc9b21a28aba711a45d0b/html5/thumbnails/12.jpg)
Start
Finish
Thermocouples
Arc
![Page 13: Heat Flow in Welding(1)](https://reader033.fdocuments.us/reader033/viewer/2022061615/577cc9b21a28aba711a45d0b/html5/thumbnails/13.jpg)
TEMP
![Page 14: Heat Flow in Welding(1)](https://reader033.fdocuments.us/reader033/viewer/2022061615/577cc9b21a28aba711a45d0b/html5/thumbnails/14.jpg)
Slow Travel Speed
Fast Travel Speed
1 2 34 5
![Page 15: Heat Flow in Welding(1)](https://reader033.fdocuments.us/reader033/viewer/2022061615/577cc9b21a28aba711a45d0b/html5/thumbnails/15.jpg)
![Page 16: Heat Flow in Welding(1)](https://reader033.fdocuments.us/reader033/viewer/2022061615/577cc9b21a28aba711a45d0b/html5/thumbnails/16.jpg)
![Page 17: Heat Flow in Welding(1)](https://reader033.fdocuments.us/reader033/viewer/2022061615/577cc9b21a28aba711a45d0b/html5/thumbnails/17.jpg)
![Page 18: Heat Flow in Welding(1)](https://reader033.fdocuments.us/reader033/viewer/2022061615/577cc9b21a28aba711a45d0b/html5/thumbnails/18.jpg)
Turn to the person sitting next to you and discuss (1 min.):• This curve was generated when a fast moving arc passed
by the thermocouples. What curves would a slow moving arc produce?
![Page 19: Heat Flow in Welding(1)](https://reader033.fdocuments.us/reader033/viewer/2022061615/577cc9b21a28aba711a45d0b/html5/thumbnails/19.jpg)
Do the Homework Assignment 5 “Heat Flow in Welding” from the Assignment Page of the
WE300 Website