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Shielded Metal Arc Shielded Metal Arc Welding Joints and Welding Joints and
PassesPasses
Butt joint, Corner joint, Lap joint Tee joint, Root pass, Hot pass, Filler pass, Cover pass
PREP FOR 1PREP FOR 1STST PROJECT! PROJECT!
The know how behind how to do your first project!
Joints , Welds, And Passes
4 - 3
Tack WeldsTack Welds
Short welds spaced at intervals to join parts to whole in process of assembly before welding
Must be strong◦Hold part in position◦Able to resist stress when expansion and
contraction occur during weldingNumber and size of tack welds depend
upon thickness of plate, length of seam, and amount of cold working to be done
4 - 4
Tack WeldsTack Welds
Use more heat for tack welding than for major welding
Must have good fusion and good root penetration
Flat and smooth
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
American Welding Society
4 - 5
Tack WeldsTack Welds
Position is important as metal heats and cools it expands and contracts
Example from P.D Session
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
American Welding Society
4 - 6
Stringer BeadStringer Bead
Weld made by moving weld pool along intended path in straight line
Fast cooling rates because of faster travel speed◦Can impact grain structure and affect distortion
level
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
American Welding Society, Welding Inspection Technology, 4th ed.,p. 4-27, Fig. 4.32, 2000.
4 - 7
PorosityPorosity
Cavity-type discontinuities (pores) formed by gas entrapment during solidification
Discontinuities are spherical and may be elongated
Usually caused by contamination of filler metal or base metal or impropergas shielding
Not considered as severeconcern as cracks or incomplete fusion
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
4 - 8
Four Weld TypesFour Weld Types
Bead (surface) weld
Fillet weld
• Groove weld
• Plug (slot) weld
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
4 - 9
Bead WeldsBead Welds
Also called surface weldsSingle-pass deposits of weld metalUsed to build up pad of metal and to
replace metal on worn surfaces
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
4 - 10
Fillet WeldsFillet Welds
Consist of one or more beads deposited in right angle formed by two plates
Take triangular cross section due to location placed in weld joint
Used for lap joints, T-joints, and open corner joints
Weld symbol takes same triangular shape as weld
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
4 - 11
Fillet WeldFillet Weld
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
American Welding Society, Welding Inspection Technology, 4th ed., p. 4-24, Fig. 4.22, 2000
Important aspect is its profile
KNOW TERMS**
4 - 12
Fillet WeldsFillet WeldsMost common weld used in industryAs strong or stronger than base metal if weld
correct size and proper welding techniques used
Contour is shape of face of weld◦Flat◦Convex◦Concave
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
4 - 13
Under WeldedUnder Welded
Remember: A weld or weld joint is no stronger than its weakest point.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
4 - 14
Weld LengthWeld Length
Fillet and groove welds usually made along full length of joint◦Sometimes full strength can be achieved by
welding a portion of jointEffective length of fillet weld measured as
overall length of full-size fillet weld◦Start and stop of weld must be allowed for
Not square, so allowance made when measuring Space between welds determined by
center-to-center distance of weld which is called pitch
4 - 15
Weld Area Weld Area and Stressand Stress
Easily calculatedImportant to determine how much stress
joint can take
area = weld length x weld size
area weld
load stress
Safety margins are built in to ensure the weld is able to withstand the load.
4 - 16
Groove WeldsGroove Welds
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Consist of one or more beads deposited in groove
Used for butt joints◦Unprepared with square edges◦Prepared with bevel or J-groove
If both members prepared same, take shape of V or U and named V-groove or U-groove butt joint
Weld applicable on both plate and pipe
4 - 17
Groove WeldsGroove Welds
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
American Welding Society
ActivityActivityForm joints with pieces of wood or metal
and draw
Square Butt JointSquare Butt Joint
Made by tack welding two flat pieces of plate together
Root Opening/Gap – Space between the plates
Edge WeldEdge Weld
Made by placing edges of the weld evenly
Metal held together by clamp with no openings
Weld should equal the thickness of the plate, have build up
Weld bead equal to thickness of joint (usually tack first)
Edge WeldEdge Weld
Outside Corner JointOutside Corner Joint
Placing plates at 90˚ to each other with edges forming V-Groove
May or may not have slight root opening left between plate edges
Weld bead should completely fill V-Groove formed by the plates and may be slightly convexted
Outside Corner JointOutside Corner Joint
Outside Corner JointOutside Corner Joint
Lap Joint (Project #2) Lap Joint (Project #2)
Made by overlapping the edges of two plates
Can be welded on one or both sides of joint with fillet welds
Build up of weld should equal the thickness of the plate
Lap Joint (Project #2) Lap Joint (Project #2)
Penetration on lap joints does not improve strength
Complete fusion is required – root must be melted for fusion
Lap Joint (Project #2) Lap Joint (Project #2)
Very important to use tack welds to hold in place and clean slag after welds
Lap Joint (Project #2) Lap Joint (Project #2)
Lap Joint (Project #2) Lap Joint (Project #2)
Tee Joint Tee Joint
Tack welding one piece of metal to another piece of metal at a right angle
Important to place tack welds correctly ◦PD EXAMPLE
◦Remove slag from tack welds
Tee Joint Tee Joint
Watch heat and strength
Root PassRoot Pass
First weld bead of a multi pass weld
Fuses two parts of metal together and establishes depth of weld metal penetration
Essential for a good weld
Root PassRoot Pass
May or may not use backing strip
Root PassRoot Pass
Terms to know for project
Root PassRoot Pass
Ideal root pass
Root PassRoot Pass
Our project (except backing plate)
Hot PassHot PassSurface of root pass may be irregular,
have undercut, overlap, slag inclusions or other defects
A way to clean out trapped slag and make the root pass more uniform
Hot PassHot PassUses a higher-than-normal amperage
setting and a fast travel rate to reshape the bead and burn out the trapped slag.
Can be made after chipping away slag and cleaning with wire brush
Filler PassFiller PassUsed after root pass in completed and has
been cleaned
Groove is filled up with beads = Filler passes
“Fills up” Area to be welded
Filler PassFiller PassUse stringer beads
Beads must overlap each other enough so the finished bead is smooth
Must clean bead before doing next pass
****** VERY IMPORTANT FOR****** PROJECT #1
Filler PassFiller Pass
WILL BE DOING THIS ON PROJECT
Cover PassCover Pass
Last bead on a multi-pass weld = Cover Pass
Important to keep it clean and neat looking because most welds have visual inspection
Should be free from defects (undercut, overlap, porosity, slag inclusions)
Cover PassCover Pass
No more than 1/8th the groove opening
Project #1Project #1
Project #1Project #1
Project #1Project #1
PLATE PREPARATION
Project #1Project #1
Project #1Project #1