uncoated plain carbon steel process variables continued
TRANSCRIPT
Uncoated Plain Carbon SteelProcess VariablesContinued
Uncoated Steel – Process Variables Continued
Lesson ObjectivesWhen you finish this lesson you will understand:• the effect that various welding parameter variables have on the weld quality of uncoated steels (continuation from last module)
Learning Activities1. Look up Keywords2. View Slides; 3. Read Notes, 4. Listen to lecture5. View Demo6. Do on-line
workbook7. Do homework
KeywordsElectrode Material, Electrode Design, Electrode Coating, Shunting, Post Weld Temper
Process VariablesProcess
Parameters:(Manufacturer’s Control)
• Weld Current Type
• Weld Time
• Hold Time
• Pulsing
• Electrode Force
• Electrode Material
• Electrode Designs
• Electrode Cooling
• Postweld Temper
Material Parameters:(Steel Company Control)
• Chemistry• Cleanliness• Surface Condition• Material Processing• Thickness
Electrode MaterialsRWMAClass #
ElectricalConductivity
Composition(%)
UltimateStrength
(ksi)
AnnealingTemperature
(°C)
ThermalConductivity
(Cal/cm-sec-°C)
-
1
2
3
4
5
Cu
99-Cu,1-Cd
99.2-Cu,0.8-Cr
97-Cu, 2.5-Co, 0.5-Be
Cu & Be
Cu & Al
90
92
80 (C)82 (F)48 (C)52 (F)20 (C)23 (F)
18 70 - 0.16
30 - -
60 (F)
30 (C)62 (F)95 (C)105 (F)110 (C)170 (F)
660 0.82
710
0.77 (C)0.75 (F)0.43 (C)0.45 (F)0.18 (C)0.19 (F)
930 (C)900 (F)1020 (C)900 (F)
* C = Cast, F = Forging
Number of Welds
5K 10K 15K 20K
Leng
th C
hang
e
Class 1
Class 2
Cu - Al Oxide
RB @ 500 C
< 3040
85
% IACS*
* Percent Internatinal Annealed Copper Standard
9280
~90
Uncoated Steel
Turn to the person sitting next to you and discuss (1 min.):• Besides alloy content, what other factors might effect the electrical conductivity of copper electrodes? How might this change your decision in the manufacturing technique used to manufacture these electrodes? Would the fact that you are welding steel (as opposed to say aluminum) have any bearing on the manufacturing technique?
Process VariablesProcess
Parameters:(Manufacturer’s Control)
• Weld Current Type
• Weld Time
• Hold Time
• Pulsing
• Electrode Force
• Electrode Material
• Electrode Designs
• Electrode Cooling
• Postweld Temper
Material Parameters:(Steel Company Control)
• Chemistry• Cleanliness• Surface Condition• Material Processing• Thickness
Electrode Geometry
“A” “A” “A” “A”6° 20°
45°
3
14
14
14
14
45°20°
Pointed
DomeTruncated
ConeTruncated
Cone
[Reference: Welding in the Automotive Industry, p.135, D. W. Dickinson]
Electrode Face Dia. Vs Welding Current Range
0.028 inch (0.71 mm)0.05C-0.09P
0.25 inch (6.4 mm)Electrode
0.312 inch (7.9 mm) Electrode
1300A
3300A
Weld Time 15 cyclesElectrode Pressure 13ksiHold Time 30 cycles
Current, kA6 7 8 9 10 11 12 13 14
But
ton
Dia
met
er,
inch
0.30
0.25
0.20
0.15
0.10
0.05
8
7
6
5
4
3
2
1
mm
[Reference: Welding in the Automotive Industry, p.137, D. W. Dickinson]
Effect of Electrode Diameter on Current Range
4000
3000
2000
1000
00.15 0.2 0.25 0.3 0.35
Electrode Diameter, in.
Cu
rre
nt R
an
ge, A
mp
Current Range:0.15 in. Button to Expulsion
[Reference: “Spot Weldability ofHigh-Strength Sheet Steels”, Welding Journal 59 (January1980), Baker & Sawhill]
Codes and Equations Used for Electrode Face Selection
ELECTRODE DIAMETER, IN
SH
EE
T T
HIC
KN
ES
S, I
N
0.1
0.2
0.3
0.2 0.4 0.6 0.8
Ayers & Fisher
D = 1.5t + 0.1 (Leng)D = 2t + 0.1 (AWS)
Ford BA 13-4
Turn to the person sitting next to you and discuss (1 min.):• It is surprising that with the many different people who have developed codes governing the electrode face diameter as a function of sheet thickness, they all come to about the same size vs. sheet thickness. Why do you suppose this is the case?
Process VariablesProcess
Parameters:(Manufacturer’s Control)
• Weld Current Type
• Weld Time
• Hold Time
• Pulsing
• Electrode Force
• Electrode Material
• Electrode Designs
• Electrode Cooling
• Shunting
Material Parameters:(Steel Company Control)
• Chemistry• Cleanliness• Surface Condition• Material Processing• Thickness
• Upslope/Downslope/ Postweld Temper
Hirsch R., Influence of Water Temp& Flow on Electrode LifeSMWC VII, AWS, 1996
Poor CoolingPoor CoolingIncreased Electrode WearIncreased Electrode Wear
Hirsch R., Influence of Water Temp& Flow on Electrode LifeSMWC VII, AWS, 1996
Warm Water
Slower Flow
NU
MB
ER
OF
WE
LDS
DISTANCE OF WATER FROMELECTRODE FACE
Room Temp
Refrigerated
Dickinson, Welding In AutoAISI, 1981
Baysore, J, DCT Inc, Private Communications, July 2000
No Water Cooling
Turn to the person sitting next to you and discuss (1 min.):• What design criteria did the NOWAT people have to consider when they developed their robots that do not need electrode cooling water?
Process VariablesProcess
Parameters:(Manufacturer’s Control)
• Weld Current Type
• Weld Time
• Hold Time
• Pulsing
• Electrode Force
• Electrode Material
• Electrode Designs
• Electrode Cooling
• Shunting
Material Parameters:(Steel Company Control)
• Chemistry• Cleanliness• Surface Condition• Material Processing• Thickness
• Upslope/Downslope/ Postweld Temper
Shunting Effect
AB
IB
IA
Itotal = IA + IB
IARA = IBRB
IB/Itotal = 1 - RB/(RA + RB)[Reference: Resistance Welding Manual, p.1-7, RWMA]
Effect of Shunting Distance (Spot Spacing)
AC welding 1/4 in. x 3 in. mild steelClass “8” weldAverage shear strength of 24welds, 17,570 lbsStock temp 25°CAll welds made with one shunt circuitCurve estimated below 2-1/2 in.shunt distance
Shunt Distance, in.
Shunt Distance, cm
Sh
ear
Str
eng
th o
f Sin
gle
We
ld, %
[Reference: Welding Handbook, Volume 2, p. 551, AWS]
Process VariablesProcess
Parameters:(Manufacturer’s Control)
• Weld Current Type
• Weld Time
• Hold Time
• Pulsing
• Electrode Force
• Electrode Material
• Electrode Designs
• Electrode Cooling
• Shunting
Material Parameters:(Steel Company Control)
• Chemistry• Cleanliness• Surface Condition• Material Processing• Thickness
• Upslope/Downslope/ Postweld Temper
Upslope/Downslope, Hold Time, & Temper
Weld Current
Temper Current
Ele
ctro
de
Pre
ssu
reC
urr
ent
Squeeze Time Weld Time Off Time Hold TimeUpslope Downslope Temper
