Shielded Metal Arc Welding Joints and Passes Butt joint, Corner joint, Lap joint Tee joint, Root pass, Hot pass, Filler pass, Cover pass

PREP FOR 1ST PROJECT! The know how behind how to do your first project! Joints , Welds, And Passes

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 welding Number and size of tack welds depend upon thickness of plate, length of seam, and amount of cold working to be done Tack Welds

Tack Welds Use more heat for tack welding than for major welding Must have good fusion and good root penetration Flat and smooth American Welding Society Tack Welds Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Position is important as metal heats and cools it expands and contracts Example from P.D Session American Welding Society Tack Welds Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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 Stringer Bead American Welding Society, Welding Inspection Technology, 4th ed., p. 4-27, Fig. 4.32, 2000. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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 improper gas shielding Not considered as severe concern as cracks or incomplete fusion Porosity Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Four Weld Types Groove weld Plug (slot) weld Bead (surface) weld Fillet weld Groove weld Plug (slot) weld Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Bead Welds Also called surface welds Single-pass deposits of weld metal Used to build up pad of metal and to replace metal on worn surfaces Bead Welds Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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 Fillet Welds Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Fillet Weld Important aspect is its profile KNOW TERMS** American Welding Society, Welding Inspection Technology, 4th ed., p. 4-24, Fig. 4.22, 2000 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Fillet Welds Most common weld used in industry As 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.

Remember: A weld or weld joint is no stronger than its weakest point. Under Welded Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Fillet and groove welds usually made along full length of joint Sometimes full strength can be achieved by welding a portion of joint Effective 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 Weld Length

area = weld length x weld size Easily calculated Important to determine how much stress joint can take area = weld length x weld size Safety margins are built in to ensure the weld is able to withstand the load. Weld Area and Stress

Groove Welds 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 Groove Welds Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Groove Welds American Welding Society Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Activity Form joints with pieces of wood or metal and draw

Square Butt Joint Made by tack welding two flat pieces of plate together Root Opening/Gap – Space between the plates

Edge 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 Weld

Outside 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 Joint

Outside Corner Joint

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) Penetration on lap joints does not improve strength Complete fusion is required – root must be melted for fusion

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)

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 Watch heat and strength

Root 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 Pass May or may not use backing strip

Root Pass Terms to know for project

Root Pass Ideal root pass

Root Pass Our project (except backing plate)

Hot Pass Surface 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 Pass Uses 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 Pass Used after root pass in completed and has been cleaned Groove is filled up with beads = Filler passes “Fills up” Area to be welded

****** VERY IMPORTANT FOR****** PROJECT #1 Filler Pass Use 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 Pass WILL BE DOING THIS ON PROJECT

Cover 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 Pass No more than 1/8th the groove opening

Project #1

Project #1

Project #1 PLATE PREPARATION

Project #1

Project #1