8/11/2019 Lecture Welding Processes Manufacturing Technology
1/97
Welding Processes
8/11/2019 Lecture Welding Processes Manufacturing Technology
2/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
3/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
4/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
5/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
6/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
7/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
8/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
9/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
10/97
Heat input
Heat Loss
8/11/2019 Lecture Welding Processes Manufacturing Technology
11/97
Heat Input
H = energy input, energy/unit length, joules /
H = Power/Travel Speed, = P/v
P = total input power, Watts
v = travel speed of heat source, mm/se
Describes energy per unit length delivered,
not rate of delivery
Used in codes & specifications
This energy does not all go entirely to the wo
8/11/2019 Lecture Welding Processes Manufacturing Technology
12/97
Heat Input for Arcs
H = P/v = EI/v
E = Arc Voltage (Volts)
I = Arc Current (Amps)
EI = Process power, converted to Heatv = Welding Travel Speed
Hnet = f1H = f1P/v = f1EI/v
f1 = Heat Transfer Efficiency
Not all the arc energy goes into the work
8/11/2019 Lecture Welding Processes Manufacturing Technology
13/97
Arc Length
long
short
f1 = Heat Transfer Efficiency
8/11/2019 Lecture Welding Processes Manufacturing Technology
14/97
Reinforcement
Heat
Affected
Zone
Melted Base Metal
Aw = Cross Section of Weld = Am + Ar
For Autogenous Weld (no fil ler metal)
Aw = Am
Q =Heat Required to
elevate sol id to MP+ Latent Heat
of FusionHeat Required to melt
a Given Volume of Weld=
8/11/2019 Lecture Welding Processes Manufacturing Technology
15/97
Enthalpy of Melting
Q =Heat Required to
elevate sol id to MP
+ Latent Heat
of Fusion
Heat Requi red to melt
a Given Volume of Weld
=
ofFusionLatentHeatL
remtemperatuusuallyrooperatureInitialTemT
peratureMeltingTemT
CmassrgythermalenetyHeatCapaciC
volumemassDensity
LTTCQ
o
m
o
p
omp
,
/(
)/(
Not all the net heat transferred goes into melting
8/11/2019 Lecture Welding Processes Manufacturing Technology
16/97
Melting Efficiency
f2 = Melting efficiency, the fraction of the process heat
energy per unit length delivered to the metal which
is required to melt the metal
f2 = QAw/Hnet
f2 = QAwv/f1EI
From previous slide:
Hnet = f1H = f1P/v = f1EI/v
Melting Efficiency Depends On:
Higher Thermal Conductivity - Lower Efficiency
High Energy Density Heat Source - Higher Efficiency
8/11/2019 Lecture Welding Processes Manufacturing Technology
17/97
Polarity and Current Flow
I I
DCEP DCEN
Anode
Cathode
Cathode
Anode
Welding Electrode or "Electrode"
Work Electrode or "Work"
Straight
SPEN
Reverse
RPEP
8/11/2019 Lecture Welding Processes Manufacturing Technology
18/97
Conduction of Current in the Arc
Plasma
Electron
Ion
NeutralGas Atom
Ionization Free
RecombinationT>10,000K
Thermal
Cathode
Anode
Electrons Emitted
Electrons Absorbed
8/11/2019 Lecture Welding Processes Manufacturing Technology
19/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
20/97
Thermionic Work Function
V
I I/e electrons/second
Energy into
Cathode
Anode
emitted electrons = I x WF
Energy deposited by
impinging electrons = I x WF
I/e electrons/second
(from arc)
(into anode)
Energy Required for electron to escape a solid surface
Work Function of pure Tungsten = 4.4 eV
Work Function of Thoriated W = 4.1 eV
8/11/2019 Lecture Welding Processes Manufacturing Technology
21/97
} }}
8/11/2019 Lecture Welding Processes Manufacturing Technology
22/97
Arc V-I Characteristic
Welding
PowerSource
A
V
Welding
Arc
I
V
V
I0
20
30
40
10
50 100 150 200 250 3000
h1
h2
h3
h=0
h
Unstable
8/11/2019 Lecture Welding Processes Manufacturing Technology
23/97
Ionization Potential
He 24.6 ev
Ar 15.8
N 15.6
Fe 7.9
Na 5.1
P 4.3
8/11/2019 Lecture Welding Processes Manufacturing Technology
24/97
Open-Circuit Voltage
V
I
CC
CV
Voc
VocHot Start
Arc
8/11/2019 Lecture Welding Processes Manufacturing Technology
25/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
26/97
Electrical Stability of the Arc
V
I
Rs
Unstable
Stable Arc
SourceArc willoperate here
8/11/2019 Lecture Welding Processes Manufacturing Technology
27/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
28/97
Manual Arc Control
F
B
F
B
B>FF>B
hh
F
B
B=F
h
F = Feed RateB = Burn-Off Rate
8/11/2019 Lecture Welding Processes Manufacturing Technology
29/97
Manual Arc Control Inputs
V
I
Arc
Current Varies
h
h
Power
I
Source
Vary
V
I
Arc
Power
I
Vary Current
Source
Vary
8/11/2019 Lecture Welding Processes Manufacturing Technology
30/97
Self-Regulation of the Arc
VmF
B
h
ContactTube or Tip
Feed Rolls
Wire Spoolor Reel
WireFeederCV
Power
SourceV
I
V
I
CV
I=F/k1
arc too
arc tooshort
long
currentdrops
currentrises
F=constant, I varies
BF
8/11/2019 Lecture Welding Processes Manufacturing Technology
31/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
32/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
33/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
34/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
35/97
Ave I
8/11/2019 Lecture Welding Processes Manufacturing Technology
36/97
Pulsed Arc
Tandom
Arc
8/11/2019 Lecture Welding Processes Manufacturing Technology
37/97
11 - 37
Welding Power Sources
Each type of power source has fundamentalelectrical differences that best suit particularprocesses
Welding machine
Must meet changing arc load and environmentalconditions instantly
Must deliver exact amount of electric currentprecisely at right time to welding arc
Available in wide variety of types and sizes
8/11/2019 Lecture Welding Processes Manufacturing Technology
38/97
11 - 38
Four Types of Power Source
Engine-driven generators
Powered by gas or diesel combustion engine
Can be found with a.c. or d.c. electric motor
No longer being manufactured and rarely found
Inverters
Increases frequency of incoming primary power
Constant current, constant voltage, or both
Produce a.c. or d.c. welding current
8/11/2019 Lecture Welding Processes Manufacturing Technology
39/97
11 - 39
Four Types of Power Source
A.C. transformers
Used to step down a.c. line power voltage to a.c.
welding voltage
Transformer-rectifiersUse basic electrical transformer to step down a.c.
line power voltage to a.c. welding voltage
Welding voltage then passed through rectifier to
convert a.c. output to d.c. welding currentMay be either d.c. or a.c.-d.c. machines
8/11/2019 Lecture Welding Processes Manufacturing Technology
40/97
11 - 40
Bridge Rectifier
8/11/2019 Lecture Welding Processes Manufacturing Technology
41/97
11 - 41
Output Slope
Two basic types
Constant current
Constant voltage
8/11/2019 Lecture Welding Processes Manufacturing Technology
42/97
11 - 42
Current Controls
Amperage
Quantity of current (flow)
Determines amount of heat produced at weld
VoltageMeasure of force of current (push)
Determines ability to strike an arc and maintain its
consistency
8/11/2019 Lecture Welding Processes Manufacturing Technology
43/97
11 - 43
Constant CurrentWelding Machines
Used for shielded metal arc welding and gas tungsten
arc welding
Available in both d.c. and a.c. welding current
Current remains fairly constant regardless of changes in arc
length
Total Wattage stays the same
Voltage drops as amps increase (dropping arc voltage(DAV) machine)
Enables welder to control welding current in specificrange by changing length of arc
8/11/2019 Lecture Welding Processes Manufacturing Technology
44/97
11 - 44
Open Circuit and Arc Voltage
Open circuit voltage runs between 50-100 volts (no
welding being done, volts high, no amps)
Drops to arc voltage when arc struck
Arc voltages (Voltage generated between electrode and work duringwelding, voltage lower, amps higher)
Range: 36 volts (long arc) to 18 volts (short arc)
Determined by arc length held by welder and type of
electrode used
Arc lengthened, arc voltage increases and currentdecreases
8/11/2019 Lecture Welding Processes Manufacturing Technology
45/97
11 - 45
Polarity
Electrode negative and electrode positive used in d.c.
welding
DCEN (d.c. electrode negative)
Electrode connected to negative terminal of power source
and work connected to positive terminal (current flows
from neg to pos) flow from electrode to work = more
electrode consumption.
DCEP (d.c. electrode positive)
Electrode connected to positive terminal of power sourceand work connected to negative terminal
8/11/2019 Lecture Welding Processes Manufacturing Technology
46/97
11 - 46
D.C. Transformer-Rectifier WeldingMachines
Copyrigh t The McGraw-Hill Companies, Inc. Permission required for reprodu ction or di splay.
The Lincoln Electric Co.
Miller Electric Mfg. Co.
Have many designs and purposes
Flexibility one reason for wide acceptance
Deliver either DCEN or DCEP
May be used for:Stick electrode welding
Gas tungsten arc welding
Submerged arc welding
Multi-operator systemsStud welding
8/11/2019 Lecture Welding Processes Manufacturing Technology
47/97
11 - 47
Transformer-Rectifier Machines
Have two basic parts
Transformer for producing and regulatingalternating current that enters machine
rectifier that converts a.c. to d.c.
Third important part is ventilating fan
Keeps rectifier from overheating
Design improves arc stability and makes iteasy to hold short arc which is soft and steady
No major rotating parts so consume littlepower
8/11/2019 Lecture Welding Processes Manufacturing Technology
48/97
11 - 48
A.C. Transformer WeldingMachines
Most popular a.c. welding machine
Function of transformer
Step down high voltage of input current to high
amperage, low voltage current required forwelding
Especially suited
for heavy work
Copyrigh t The McGraw-Hill Companies, Inc. Permission required for reprodu ction or di splay.
The Lincoln Electric Co.Miller Electric Mfg. Co
8/11/2019 Lecture Welding Processes Manufacturing Technology
49/97
11 - 49
Advantages of a.c. PowerSources
Reduces tendency to arc blow
Can use larger electrodes
Resulting in faster speeds on heavy materials
Lower cost Decreased power consumption
High overall electrical efficiency
Noiseless operation
Reduced maintenance
8/11/2019 Lecture Welding Processes Manufacturing Technology
50/97
11 - 50
D.C. and A.C.-D.C. Inverter WeldingMachines
Portable, lightweight, and versatile
May be either constant current, constant
voltage or both
Can perform several different processes
Copyrigh t The McGraw-Hill Companies, Inc. Permission required for reprodu ction or di splay.
Miller electric Mfg. Co.The Lincoln Electric Co.
8/11/2019 Lecture Welding Processes Manufacturing Technology
51/97
11 - 51
Duty Cycle
Percentage of any given 10-minute period that
machine can operate at rated current without
overheating or breaking down
Rating of 100% means machine can be used atrated amperage on continuous basis
Required by continuous, automatic machine welding
Rating of 60% means machine can be used at its
capacity 6 out of every 10 minutes without
damage
Satisfactory for heavy SMAW and GTAW
8/11/2019 Lecture Welding Processes Manufacturing Technology
52/97
Duty Cycle
Duty Cycle Amperes TimeAvailable
30% 250 3 Min/10 Min
40% 225 4 Min/10 Min
50% 200 5 Min/10 Min
60% 190 6 Min/10 Min70% 180 7 Min/10 Min
80% 170 8 Min/10 Min
90% 155 9 Min/10 Min
100% 140 10 Min/10 Min
8/11/2019 Lecture Welding Processes Manufacturing Technology
53/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
54/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
55/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
56/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
57/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
58/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
59/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
60/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
61/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
62/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
63/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
64/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
65/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
66/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
67/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
68/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
69/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
70/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
71/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
72/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
73/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
74/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
75/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
76/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
77/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
78/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
79/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
80/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
81/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
82/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
83/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
84/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
85/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
86/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
87/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
88/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
89/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
90/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
91/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
92/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
93/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
94/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
95/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
96/97
8/11/2019 Lecture Welding Processes Manufacturing Technology
97/97