ButtJoint: it isused to join two members aligned in the same plane. This joint is frequentlyused in plate, sheet metal, and pipe work. Corner and Tee Joints: these joints are used tojoin two members located at right angles to each other. In cross section, thecorner joint forms an L-shape, and the tee joint has the shape of the letter T. Lap Joint: this joint is made bylapping one piece of metal over another. This is one of the strongest types ofjoints available; however, for maximum joint efficiency, the overlap should beat least three times the thickness of thethinnest member of the joint. Edge Joint: it is used to join theedges of two or more members lying in the same plane. In most cases, one of themembers is flanged, as seen in the figure. This type is frequently used insheet metal work for joining metals 1/4 inch or less in thickness that are notsubjected to heavy loads. There are many types of welds. The most common types arethe bead, surfacing, plug, slot, fillet, and groove.
- · A weld Bead isa weld deposit produced by a single pass
with one of the welding processes.A weld bead may be either narrow or wide,depending on the amount of transverse oscillation(side-to-side movement) used by the welder. A weld bead madewithout much weaving motion is often referred to as a stringerbead. On the other hand, a weldbead made with side-to-side oscillation is called a weave bead.
- · Several weld beads appliedside-by-side are usually used in Surfacingwhichis a welding process used to apply a hard, wear-resistant layer of metalto surfaces or edges of worn-outparts.
- · A Filletweld is triangular in shape and this weld is used to join two surfacesthat are atapproximately right angles to each other in a lap, tee, or comer joint.
- Plug and Slot welds are welds made throughholes or slots in one member of a lap joint. These welds are used to join thatmember to the surface of another member that has been exposed through the hole.
- Groove welds (also may be referred to as Butt welds)are simply welds made in the groove between two members to be joined. The weldis adaptable to a variety of butt joints, as seen in the figure.
Groove welds may be joined with one or more weldbeads, depending on the thickness ofthe metal.If two or more beads are deposited in the groove,the weld is made with multiple-pass
layers, as shown in the figure. As a rule, a multiple-passlayer is made with stringer beads in manual operations.
o The buildup sequence refers to the orderin whichthe beads of a multiple-pass weld are depositedin the joint. Usually, before adding thenext pass, the previous pass needs to cooldown to a certain temperature which is calledthe inter-pass temperature. Also, beforeadding the next pass, the surface of theprevious pass needs to be cleaned from slag, especially with SMAW, using a wire brush or otherappropriate method. While there are manyvariations of joints, the parts of the joint are described by standard terms.
- · The rootof a joint is that portion of the joint where the metals are closest to each other. As shown in the figure, the root may be a point, a line, or an area, when viewed in crosssection.
- · A grooveis an opening or space provided between the edges of the metal parts tobe welded.
o The grooveface is that surface of a metal part included in the groove, as shownin view A.
- · A givenjoint may have a root face or a root edge.
o The root face,also shown in view A, is the portion of the prepared edge of a part to bejoined by a groove weld that has not been grooved. As you can see, · The specifiedrequirements for a particular joint are expressed in terms such as bevelangle, groove angle, groove radius, and root opening whichare illustrated in the figure. o The bevel angle isthe angle formed betweenthe prepared edge of a member and aplane perpendicular to the surface o The grooveangle is the total angle of the groovebetween the parts to be joined. Forexample, if the edge of each of two plateswere beveled to an angle of 30 degrees,the groove angle would be 60 o The grooveradius is the radius used to form the shape of a J- or U-groove weldjoint. It is used only for special groove joint designs. o The root opening refersto the separation between the parts to be joined at the root of the joint. Itis sometimes called the “root gap”. ? Root penetration refersto the depth that a weld extendsinto the root of the joint. Root penetration is measuredon the center line of the root cross section.
? Jointpenetration refers to the minimum depth that a grooveweld extends from its face into a joint,
exclusive of weld reinforcement. ?In many cases, rootpenetration and joint penetration, often refer to the same dimension. ? Weld reinforcement isa term used to describe weldmetal in excess of the metal necessary to fill ajoint. The reinforcement needs to be grindedin some casesdepending on the intended use of the joint.
It is important to be familiarwith the terms used to describe a weld. The figure shows the parts of grooveweld and fillet welds. · The faceis the exposed surface of a weld on the side from which the weld was made. · The toeis the junction between the face of the weld and the base metal. · The rootof a weld includes the points at which the back of the weld intersects thebase metal surfaces. · In a filletweld, the leg is the portion of the weld from the toe to theroot. · In a filletweld, the throat is the distance from the root to a point onthe face of the weld along a line perpendicular to the face of the weld.Theoretically, the face forms a straight line between the toes. · The sizeof a fillet weld refers to the length of the legs of the weld. The twolegs are assumed to be equal in size unless otherwise specified. Some other terms which are usedto describe areas or zones of welds are:
- The fusionzone is the region of the base metal that is actually melted. Thedepth of fusion is the distance that fusion extends into the base metal orprevious weldingpass.
- The heat-affectedzone (HAZ) refers to that portion of the base metalthat has not been melted; however, thestructural or mechanical propertiesof the metal have been altered by thewelding heat.
Introduction to Non-DestructiveTesting Techniques Introduction to Welding Technology Page 9 of 9 Welding symbols are used ondrawings to indicate the type and specifications of the weld.
- The figure showsthe American Welding Society (AWS) standard welding symbol. The most important features of thewelding symbol are illustrated below:
- The table showsthe Basic weld symbol for the different types of welds.
- The figures belowshow some examples for the use of welding symbols