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  Useful Welding Data

Here is a collection of some basic data on welding. We hope it would be useful for you.

Causes & Remedies for Fusion Weld Discontinuities

Suggested Pre-Heating for Standard Electrodes

AWS Electrode Classification SFA 5.1

Conversion Table
Useful Formulae
 
Causes & Remedies for Fusion Weld Discontinuities
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Causes Corrective Action
A.    POROSITY
1.    Contamination of work piece - Clean joint area.
2.    Excessive moisture pickup
       in electrode covering		 - Store electrodes properly.
- Follow manufacturers recommended rebaking procedure.
3.    Moisture on work surfaces - Use preheating / warm up work piece.
4.    High sulphur content - Use basic coated base metal electrodes.
5.    a) Long arc length
       b) Excessive current
       c) Higher travel speed		 - Change welding parameters and technique.
6.    High solidification rate - Use pre-heat.
- Increase heat input.
B.    INCLUSIONS
1.    Improper cleaning procedure - Clean work surfaces and each weld run thoroughly. Wherever necessary use power wire brush, grinders, chisels to ensure a through removal of slag.
2.    Improper welding technique
       a) Excessive weaving
       b) Higher travel speed

       c) Slag flooding ahead of welding arc
- Improve welding technique.
- Reposition work to prevent loss of slag control wherever possible.
- Restrict weaving to a minimum.
3.    Narrow, inaccessible joints - Increase groove angle.
C.    INCOMPLETE FUSION
1.    Improper joint design - Increase included angle of groove joint.
- Change the groove design to a 'J' or a 'U' type.
2.    Presence of slag or oxide film - Clean weld surfaces prior to welding.
3.    Incorrect electrode position and
       operating current		 - Maintain proper electrode position and current.
4.    Improper manipulation of arc - Use correct manipulation techniques to melt the joint faces properly.
D.    INADEQUATE PENETRATION
1.    Improper joint preparation
       a) Excessively thick root face
       b) Insufficient root opening
       c) Bridging of root opening
- Use proper joint geometry.
- Reduce root face height.
- Use wider root opening.
2.    Electrode diameter too large - Use smaller electrode in root.
- Increase root opening.
3.    Inadequate current - Follow correct welding current and technique.
E.    CRACKS
1.    High rigidity of joint - Use preheating.
- Relieve residual stresses.
- Minimize shrinkage stresses using back step or block welding sequences.
2.    Poor joint fit up - Adjust root opening all alignment.
3.    Higher carbon content of weld-metal
       and/or hardenable base material		 - Use proper electrode.
- Use buttering layers wherever necessary.
4.    Too small a weld bead - Decrease travel speed to increase cross section of bead.
- Increase electrode size.
5.    High Sulpher content in base or
       weldmetal		 - Use filler with high level of sulpher fixing element like Mn.
6.    Hot cracking - Reduce the heat input.
- Minimum joint restraints.
7.    Cracking at the crater - Filling up the crater before withdrawing the electrode.
- Use taper power control device.
- Use back step welding technique.
8.    Higher hardenability - Preheat the job.
- Post weld heat treatment without cooling to room temperature.
9.    Hydrogen induced cracking/
       Delayed cracking		 - Use low hydrogen welding electrode.
- Use suitable preheat and post weld heat treatment.
10.    Presence of brittle phases
       in the microstructure of the
       base material		 - Soften the material before welding.
11.    Low ductility of the base material - Use preheat.
- anneal the base metal.
- Use ductile weldmetal.
12.    High residual stresses - Redesign the weldmetal and reduce restraints.
- Change the welding sequence.
- Use intermediate stress-relief heat treatment.
13.    Excessive dilution - Change welding current.
- Use buttering layers wherever possible.
Suggested Pre-Heating for Standard Electrodes
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Electrode Type Re - Drying Holding in an oven after re-drying
Time in Hrs. Temp. in ° C
AWS E6013 0.5 - 1.0 hr. 70 - 80° C Portable or cabinet oven at 15-20° C above ambient temperature.
AWS E6013(S) 1.5 - 2.0 hrs. 100 - 120° C
AWS E6013(SS) 1.5 - 2.0 hrs. 100 - 120° C
 
AWS E7016 1.0 - 3.0+ hrs. 250 - 350° C Portable or cabinet oven at 80-100° C for unlimited time
AWS E7018
AWS E7018 - I
AWS E7018 - G
 
AWS E7018 - A1 1.0 - 3.0+ hrs. 350 - 375° C
AWS E7018 - A2
AWS E7018 - A3
 
Stainless Steel electrodes 1.0 - 3.0+ hrs. 200 - 300° C


AWS Electrode Classification SFA 5.1
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AWS
Classification		 Type of covering Welding
Position		 Type of current
E 6010 High cellulose sodium F, V, OH, H DC(+)
E 6011 High cellulose potassium F, V, OH, H AC/DC(+)
E 6012 High titania sodium F, V, OH, H AC/DC(-)
E 6013 High titania potassium F, V, OH, H AC,DC(+)/DC(-)
E 6019 Iron oxide titania potassium F, V, OH, H AC,DC(+)/DC(-)
E 6020 High iron oxide H-fillets
F		 AC/DC(-)
AC,DC(+)/DC(-)
E 6022 High iron oxide F,H AC/DC(-)
E 6027 High iron oxide, iron powder H-fillets
F		 AC/DC(-)
E 7014 Iron powder, titania F, V, OH, H AC,DC(+)/DC(-)
E 7015 Low hydrogen sodium F, V, OH, H DC(+)
E 7016 Low hydrogen potassium F, V, OH, H AC/DC(+)
E 7018 Low hydrogen potassium, iron powder F, V, OH, H AC/DC(+)
E 7018M Low hydrogen iron powder F, V, OH, H DC(+)
E 7024 Iron powder, titania H-fillets,F AC/DC(+)/DC(-)
E 7027 High iron oxide, iron powder H-fillets
F		 AC/DC(-)
AC,DC(+)/DC(-)
E 7028 Low hydrogen potassium, iron powder H-fillets,F AC/DC(+)
E 7028 Low hydrogen potassium, iron powder F, OH, H
V-down		 AC/DC(+)
Conversion Table
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Property To Convert From To Multiply by
Area dimensions
(mm2)		 in2
mm2		 mm2
in2		 6.451600 x 102
1.550033 x 10-3
Current Density
(A/mm3)		 A/in2
A/mm2		 A/mm2
A/in2		 1.550033 x 10-3
6.451600 x 102
Deposition rate
(Kg/h)		 lb/h
Kg/h		 Kg/h
lb/h		 0.45*
2.2*
Flow rate
(litre per minute)		 ft3/h
gallon per hour
gallon per minute
cm3/min
litre per minute
cm3/min		 litre per minute
litre per minute
litre per minute
litre per minute
ft3/h
ft3/h		 4.719475 x 10-4
6.309020 x 10-2
3.785412
1.000000 x 10-3
2.118880
2.118880 x 10-3
Heat Input
(J/m)		 J/in
J/m		 J/m
J/in		 3.937008 x 10
2.540000 x 10-2
Linear measurements
(mm)		 in
ft
mm
mm
 mm
mm
in
ft		 2.540000 x 10
3.048000 x 102
3.937008 x 10-2
3.280840 x 10-3
Tensile strength psi
lb/ft2
N/mm2
Pa
Pa
Pa		 Pa
Pa
Pa
psi
lb/ft2
N/mm2		 6.894757 x 103
4.788026 x 10
1.000000 x 106
1.450377 x 10-4
2.088543 x 10-2
1.000000 x 10-6
Travel speed, wire
feed speed (mm/s)		 in/min
mm/s		 mm/s
in/min		 4.233333 x 10-4
2.362205
Energy J
J		 ft.lb.f
Kgf.m		 0.737
0.102
* Approximate conversion.
Useful Formulae
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  1. Carbon Equivalent :

CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15


2. % Delta Ferrite :

%F = 3 [Creq - 0.93Nieq - 6.7]


3. Heat Input :
H(KJ/mm) V x I x 60
VS x 1000
Where : V = Voltage
I = Current
VS = Welding speed in mm/min

4. Preheating :
CC =   C + Mn + Ni + Cu + Cr + Mo + V
    6   15   5
Ct = CC x 0.005 x tmm CE = CC + Ct Preheat temperature ° C = 350 (CE - 0.25)1/2

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