WELDING REPRESENTATION

Welding Symbol and Weld Joint Design

OBJECTIVES1. Describe the various welding processes.

2. Draw the common welding symbols.

3. Dimension a welding drawing using standard ANSI welding notation.

4. Identify and draw a fillet weld, groove weld, back weld, spot weld, seam weld, projection weld, and flash weld.

5. Describe the use of welding symbols in CAD drawings.WeldingWelding is widely used in fabricating machine parts or other structures that formerly would have been formed by casting or forging. Structural steel frames for buildings, ships, andother structures are often welded. Welding symbols on a mechanical drawing provide precise instructions for the welder. The weld type and the location of each weld must be clearly defined using standardized symbols. CAD libraries of welding symbols can simplify the drawing process. Weldingtemplates can speed the process of drawing by hand.

Welding Processes Arc welding (SMAW, Shielded Metal Arc Welding, GMAW Gas Metal Arc Welding) Resistance welding (RSW, Resistance Spot Welding) Gas welding (OFW, Oxy Fuel Welding)

GMAWRSWAn automobile frame is welded on a robotic automobile assembly line. (Courtesy of Vladimir Pcholkin/Stone/Getty images.)OFW

UNDERSTANDING A WELDING SYMBOLA welding symbol added to the drawing has many different features that specifyeach detail of the weld. The items that can be specified are: Type of weld Process Depth of bevel, size, or strength for some weld types Groove weld size Groove angle Root opening Length of weld Number and pitch (center to center spacing) of welds Whether the weld is to be field welded (done on site) All-around indicator Which side of the material is to be welded

WELDED JOINTS

Butt jointCorner jointT-jointLap jointEdge jointA number of different types of welds are applicable to each type of joint, depending on the thickness of metal, the strength of joint required, and other considerations.Basic Welds and Symbols

WELDING SYMBOLS

The basic element of the symbol is the bent arrow The arrow points to the joint where the weld is to be made Attached to the reference line, or shank, of the arrow is the weld symbol for the desired weld.The weld symbol is placed below the reference line if the weld is to be on the arrow side of the joint, or above the reference line if the weld is to be on the other side of the joint. If the weld is to be on both the arrow side and the other side of the joint, weld symbols are placed on both sides of the reference line.Supplementary Symbols

End the weld at the starting point, or ALL THE WAY AROUNDWeld at the final construction site (Not in the shop)Fully penetrateConsumable insert is melted into the final weldmentA back strap or backing plate is placed onto the back of the jointFinal contour should be flush (possibly by grinding or machining)Final contour should be Convex (possibly by grinding or machining)Final contour should be concave (possibly by grinding or machining)The Welding Symbol Tail

Reference to a specification, process, or other supplementary information is indicated by any desired symbol in the tail of the arrow. Otherwise, a general note may be placed in the tail. If no reference is indicated in the symbol, the tail may be omitted.UNLESS OTHERWISE INDICATED, MAKE ALL WELDS PERSPECIFICATION NO.XXX

Resistance Spot Weld and an Electron Beam Weld are called out in the Tail of the Welding Symbols.FILLET WELDSDimensioning of Fillet WeldsThe size of the weld is the length of one leg, For fillet welds on both sides of a joint, the dimensions should be indicated on both sides of the reference line, whether the dimensions are identical or different.

.5 Leg lengthsFillet Weld Length and Pitch

TWO inch length of weld, with a FIVE inch pitch (center-to-center). The .25 represents the weld leg length.THREE inch length of weld, with a TEN inch pitch (center-to-center). The .25 represents the weld leg length.Surface Contour and Fillet Welds

Fillet weld with a Flush FinishFillet weld with a Flush Finish by GrindingFillet weld with a Flush Finish by ChippingFillet weld with a Flush Finish by MachiningFillet weld with a Convex Finish by MachiningKEY: C= chipping G = grinding M = machining R = rolling H = hammeringGROOVE WELDS

Symbols and their ResultBACK OR BACKING WELDSA back or backing symbol opposite the groove weld symbol indicates bead-type welds used as back or backing welds on single-groove welds.

Back or Backing Weld SymbolsSURFACE WELDS

The surface weld symbol indicates a surface to be built up with single- or multiple-pass bead type welds. Because this symbol does not indicate a welded joint, there is noarrow-side or other-side significance, so the symbol is always drawn below the reference line. Indicate the minimum height of the weld deposit at the left of the weld symbol, except where no specific height is required. When a specific area of a surface is to be built up, give the dimensions of the area on the drawing.Surfacing (or Hardfacing)A Plow BladePLUG AND SLOT WELDS

The same symbol is used for plug welds and slot welds.

If it is in the arrow-side member, place theweld symbol below the reference line

If it is in the other-side member, place the weld symbol above the lineA plug weld is understood to fill the depth of the hole unlessits depth is indicated inside the weld symbolSPOT WELDSThe size of a spot weld is its diameter. If you need to indicate the minimum acceptable shear strength in pounds per spot, instead of the size of the weld, place this value at the left of the weld symbol. The pitch would be placed to the right of the weld symbol if needed . .

SEAM WELDS

The seam weld symbol, with the welding process indicated in the tail, The size of the seam weld is its width. Show this value at the left of the weld symbol, on either side of the reference line. If you need to indicate the minimum acceptable shear strength in pounds per linear inch, instead of the size of the weld, place this value at the left of the weld symbol, and show the length of a seam weld at the right of the weld symbolPROJECTION WELDS

In projection welding, one member is embossed in preparation for the weld.Projection welds are dimensioned by either size or strength. The size is the diameter of the weld.FLASH AND UPSET WELDS

Note that the process reference for flash welding (FW) or upset welding (UW) must be placed in the tail of the symbol.Flash and upset weld symbols have no arrow-side or other-side significance, butthe supplementary symbols do.

WELD SYMBOLS FROM CADMost CAD systems provide a way to quickly generate weld symbols to place in your drawing.

SolidWorks Weld Symbol Dialog BoxWeld Geometry

Fusion Weld Zone

Characteristics of a typical fusion weld zone in oxyfuel gas and arc welding. Grain Structure in Shallow and Deep Welds

(a)(b)Figure- Grain structure in (a) a deep weld (b) a shallow weld. Note that the grains in the solidified weld metal are perpendicular to the surface of the base metal. In a good weld, the solidification line at the center in the deep weld shown in (a) has grain migration, which develops uniform strength in the weld bead.Weld BeadsFigure- (a) Weld bead (on a cold-rolled nickel strip) produced by a laser beam. (b) Micro-hardness profile across the weld bead. Note the lower hardness of the weld bead compared to the base metal.

(a)(b)Regions in a Fusion Weld Zone

Schematic illustration of various regions in a fusion weld zone (and the corresponding phase diagram) for 0.30% carbon steel.Thank You !!