Welding Symbols are unique guides and instructions in form of graphs, diagrams, and images. They are necessary elements of engineering and welding. The weld symbols are specific in their nature for particular types of welds. Welders employ various types of welds and joints as per the demand of clients and the designated structure of the project. So, the necessity of weld accuracy is crucial. In this article, the aspiring students, welders, engineers, and other professionals in the welding industry can read important information on welding symbols.
- Welding Symbols Meaning
- Weld Symbols Necessity
- Welding Standards
- Welding Symbol Elements
- Welding Symbols Types
- Welding Symbols Location
- Weld Symbols Dimensions
- Spot and Seam Welds
- Stud Welds
- Surfacing Weld Symbol
- Non-Destructive Testing Symbols (AWS)
- Welding Symbols Advantages
Welding Symbols Meaning
Welding Symbols are pictorial and graphical ways to reveal prescribed information about a welding joint. The weld symbol carries more elaborated information that welder, foreman, supervisor, engineer, and architect can understand easily. Welding symbols are extensively used in engineering drawings to explain information like weld size, type, location, and other supplementary information.
The Necessity of Weld Symbols
The basic purpose of welding is to achieve the correct result after laying welds. Just performing a weld is not enough to achieve it. Accuracy and design do matter in it. We need welding symbols to weld any metal according to the prescribed guidelines. See the following image (a, b, c, d) below-
Image (a): Consider this image is given to a welder. The instruction ‘weld here’ can be interpreted in many ways or show different interpretations. Therefore, such messages are always followed by certain instructions.
Image (b): This image means a single fillet weld and the simplest weld of all. It is cheap to apply but could be seriously deficient in performance.
Image (c): This indicates a double fillet weld and slightly takes longer to apply. To make this weld successful, access to both sides of the joint should be available.
Image (d): It means a T-butt or groove weld. This weld is more complex and expensive as the horizontal object needs an edge preparation. Yet, it may be essential for certain service conditions.
Hence, we need the weld symbols. Because, sometimes, it can be risky because the size and type of the weld must be appropriate for the parent material and service conditions of the fabrication, and required information.
ISO 2553 and ANSI/AWS A2.4-98 are two main standards for defining welding/brazing terms, symbols, etc. The International Organization for Standardization has punished ISO 2553 and that of ANSI/AWS A2.4-98 by the American Welding Society. The symbols and terms might be different in both the standards.
Check some of the details on these standards as well as others as referred to-
|ANSI/AWS A2.4-98||Standard symbols for welding, brazing, and nondestructive examination|
|ANSI/AWS.A3.0-85||Standard welding terms and definitions|
|ANSI/AWS.D1.1-2000||Structural welding code|
|AWS 2.1 DC||Welding symbol chart (desk-size)|
|AWS 2.1-WC||Welding symbol chart (wall-size)|
|BS 499-C: 1999||European arc welding symbols – symbolic representation on drawings (wall chart based on BS EN 22553: 1995).|
|BS 499 Part 1: 1991||Welding terms and symbols. Part 1. Glossary for welding, brazing, and thermal cutting.|
|ISO 2553: 1992 and BS EN 22553: 1995||Welded, brazed, and soldered joints – symbolic representation on drawings.|
|ISO 9692-1: 2003 and BS EN 29692-1: 2003||Welding and allied processes – recommendations for joint preparation – manual metal arc welding, gas-shielded metal arc welding, TIG welding, and beam welding of steels.|
|ISO 4063: 1990 and BS EN 24063: 1992||Welding, brazing, soldering, and braze welding. Nomenclature of processes and reference numbers for symbolic representation on drawings.|
Welding Symbol Elements
The elements of a welding symbol carry a specific kind of information that a symbol conveys. There are elements that may be a part of a typical welding symbol. They are as follows-
- Reference Line
- Basic Welding Symbol
- Finish Symbols
- Specifications, Process
- Supplementary Weld Symbols
The image below illustrates the locations of welding symbol elements with respect to each other.
Reference Line – It is an important part of a completed welding symbol. Reference Line (horizontal line) carries on/around it all the related information of a weld. The line is usually drawn close to the weld joint due to holding important information.
Arrow – It is another necessary part of a completed welding symbol. Arrow connects the reference line with the Arrow Side of the joint. It can be placed at one or the other end of the reference line. Arrow can point in left, right, up, and down directions including towards the tail. The welding symbol can contain multiple arrows.
Welding Symbols Types
After seeing a little bit about weld symbol elements, take a look at different welding symbols. It consists of both Basic Welding Symbols and Supplementary Welding Symbols. The first one is the most commonly used in drawings and later one can be used to convey additional information about a weld.
1. Basic Welding Symbols
Welding Symbols consist of symbols for different types of Groove or Butt Welds. Further, it includes Bevel Groove Weld, Square Groove Weld, V Groove Weld, J, U, etc.
They also consist of Fillet Weld, the most frequently used type of weld, Edge Weld, Spot Weld, Plug/Slot Weld, etc.
Groove/Butt Welding Symbols
|Single V Butt/Groove Weld||The commonest form of edge preparation for this welding type|
|Square Butt/Groove Weld||This weld is limited to a maximum section thickness, depending on the welding process|
|Single Bevel Butt/Groove Weld||An edge preparation process is generally used when only one edge of the adjoining sections is available for preparation.|
|Single U Butt/Groove Weld||Sections with thicknesses greater than 12mm, this weld is used to restrict the quantity of the weld metal required.|
|Single J Butt/Groove Weld||In sections with thicknesses greater than 16mm, only one edge of the adjoining sections is available for preparation, then this weld is used to restrict the quantity of weld metal required.|
|Edge Flanged Groove Weld||ISO Standard – It is a Groove Weld between plates with raised edges. AWS Standard – it illustrates an edge weld on a flanged Groove Joint.|
|Corner Flanged Groove Weld||Groove Weld plates with one raised edge.|
|Single V Butt Weld with Broad Root Face||ISO Standard Symbol for Single V Groove Weld with Broad Root Face.|
|Single Bevel Butt Weld with Broad Root Face||ISO Standard Symbol for Single Bevel Groove Weld with Broad Root Face. Even though these two are mentioned in ISO 2553, but best avoided.|
|Flare V Groove Weld||AWS Standard Symbol shows Groove Weld formed by two curved surfaces.|
|Flare Bevel Groove Weld||AWS Standard Symbol hints Groove Weld formed by one curved surface and one plane surface.|
|Steep Flanked Single V Butt Weld||ISO Standard Symbol for Steep Flanked V Groove Weld with bevel angle of 5⁰-20⁰ for edge preparation.|
|Steep Flanked Single Bevel Butt Weld||ISO Standard Symbol for Steep Flanked Bevel Groove Weld with bevel angle of 15⁰-30⁰ for edge preparation.|
|Fillet, Edge, Other Weld Symbols|
|Fillet Weld||Most commonly used type of welding. The leg lengths are equal, if not specified.|
|Edge Weld||Usually deposited only on one side|
|Plug/Slot Weld||It forms overlapping joints using circular or elongated holes. That is completely filled with weld metal.|
|Arc Spot Weld||The symbol illustrates that it is made from one side of the joint. It is made using high heat input at a single spot.|
|Resistance Spot Weld||The Symbol illustrates that it requires access from both sides.|
|Resistance Seam Weld||Similar to Spot Welding. It is made in a linear form, instead of a single point. The symbol requires access from both sides of the joint.|
|Arc Seam Weld||It is made from only one side of the joint. Usually called Resistance Seam Welding.|
|Surfacing||The arrow line (symbol) points to the entire surface that is to be coated with weld metal.|
2. Supplementary Welding Symbols
The supplementary welding symbols provide additional information about the weld joints. Sometimes, the same symbol is used in the AWS and ISO standards.
|Supplementary Welding Symbols|
|Flat (Flush)||Used to indicate a weld face that is flat and flush with the surface. Also, shows the final shape of the weld (contour of the weld)|
|Convex||Illustrates a convex contour finish.|
|Concave||Shows a concave contour finish. Used in special cases where welded surfaces must be smooth for cleaning or painting.|
|Smooth Blended Toes||ISO Standard Symbol used to indicate weld toes must be ground to remove any slag intrusions at the toes of the welds.|
|Spacer||Indicates the use of a spacer in the joint|
|Back/Backing Weld||Used both for back weld and backing weld. Back Weld – on the opposite/reverse side of the Groove Weld after main weld finishing. Backing Weld – done before the main weld.|
|Removable Backing||Illustrates a joint with a removable backing strip.|
|Permanent Backing||Shows a permanent backing strip.|
|Consumable Insert||AWS Standard Symbol shows the tail of the Welding Symbol consists of the type of insert.|
|Weld All Round||Peripheral Weld or Weld All Around indicates a weld that must be made over the entire circumference.|
|Field weld||Field Weld or Site Weld shows welds that are not made at the initial fabrication location but rather on the field.|
|Melt Through||Indicates the need for complete penetration in welds from one side to the other.|
Welding Symbols Location
The location of welding symbols plays a significant role in the process. It consists of Butt/Groove Welds and Fillet Welds.
1. Butt/Groove Welds (location)
The following image indicates groove welding symbol location. The symbols in the image are shown for references both for ISO and AWS standards.
The first image below shows a Single V Groove Weld. It illustrates the welding symbols are located on the reference line and the arrow is pointing to one side of the joint. So, the weld can be in a plane view or a cross-section. Here, the arrow is used to point to the weld in a cross-section.
The second image below indicates a Single Bevel Groove Weld. It illustrates that the arrow points to the edge of the joint which is to be prepared for bevel.
2. Fillet Welds (location)
The symbols for Fillet Welds are similar to Groove Welds. They are also located on a reference line that is connected to an arrow and points to one side of the joint. The T-Joint and Cruciform Joint (welding joints) demonstrate the same and reveal location significance.
The first image below shows an end view of a T-Joint with a single Fillet Weld. The weld shape would not normally be shown on an engineering drawing.
The second image below indicates an end view of a Cruciform Joint with two single fillet welds. Both the welds are on different joints; which means they do not form a double fillet weld. That’s why it requires two separate arrows to indicate two single fillet welds.
The third image below shows an end view of a Cruciform Joint with a double fillet weld on the left side and a single fillet weld on the right side. The fillet weld symbol is always drawn with the upright leg on the left.
The fourth image below shows that it needs to show two symbols, one on each side of a vertical member (use two arrows with a single reference line). This method can be used as per AWS Standards (AWS A2.4-98), but not specifically authorized in ISO 2553.
Weld Symbols Dimensions
In some of the welds, the weld size can be specified. Both the ISO and AWS Standards have their own specific ways to reveal the necessary dimensions of the welds. The edge preparation depends on the factors like consumables, welding processes, parameters, and other details. Check weld symbol dimensions both for Groove Welds and Fillet Welds.
1. Groove Welds (dimensions)
a) Fully Penetrated Groove Welds
The two images below show illustrations of ISO Symbol and AWS Symbol for Fully Penetrated Single V Groove Welds and Symmetrical Double-V Butt/Groove Welds including symbolic notation.
i) Fully Penetrated Single V Groove Welds
ii) Symmetrical Double V Groove Welds
b) Partial Penetrated Groove Welds
Both ISO and AWS Standards can specify the size of Groove Weld by a number. It is placed on the left of the weld symbol. In AWS Standard, the number is placed in a bracket and the dimension is in inches. In ISO Standard, the number is placed directly and the dimension in millimeters, usually.
The first image below shows a Partial Penetration of a Single V Groove Weld.
The second image below shows a Partial Penetration Square Groove Weld. AWS Standards can indicate additional information for edge preparation. Between the sides of the weld symbol, the size of the gap between the plates is mentioned. AWS dimensions are in inches and that of ISO dimensions in millimeters.
c) Groove Weld Dimensions
AWS Standard can specify all the details of groove weld dimensions such as weld sizes on each joint side, root face, bevel angles, and root gap. The image below shows a 5/8-inch plate with a 60° bevel angle. The depth of the bevel is 1/4 inch and the weld size is 3/8 inch. It gives an overlap at the center of 1/8 inch.
d) Length of Groove Weld
The whole length of the joint must be welded in case the length of the groove weld is not mentioned. But sometimes the weld length is smaller than the joint length and may consist of intermittent welds. In this case, the specific lengths of welds and their location can be shown on the right of the weld symbol and on the drawing.
The image below indicates an AWS Standard Symbol revealing information on intermittent Square Groove Welds along with hatching.
2. Fillet Welds (Dimensions)
a) Fillet Welds (Transverse)
ISO Standard – the size of the fillet welds can be mentioned using leg length (z) and throat thickness (a). The dimension is placed on the left of the weld symbol. It depends on if the leg length or throat thickness is to be specified.
AWS Standard – the size of the fillet weld indicates the leg length and the dimension (number) is placed on the left of the weld symbol.
The image below illustrates a fillet weld both in ISO and AWS Standards with a leg length of 6mm (1/4 inch).
b) Deep Penetration Welds
The ISO standard can specify deep penetration welds. The effective weld throat is indicated by ‘S’, which is placed in front of the throat thickness (dimension). Further, it is followed by the nominal throat thickness preceded by the letter ‘A’. See in the image below-
c) Double Fillet Welds
The dimensions in double fillet weld are repeated even if they are identical. ISO dimensions are in millimeters and that of AWS dimensions in inches. See in the image below-
d) Unequal Leg Length Fillet Welds
If the short or long leg is not clear, instructions (in reference line tail) can indicate the identification. The ISO system uses a closed tail with a reference letter.
e) Longitudinal Fillet Welds
If the weld is intermittent and not continuous, then the length of the weld and also the gaps between the welds can be mentioned. The image below shows a plan view and cross-section of an intermittent fillet weld both for the ISO and AWS Standard symbols.
Spot and Seam Welds
a) Resistance Spot Welds
Resistance spot welding requires access to both sides of the joint and the weld symbol is centered on the reference line. See in the image below-
b) Arc Spot Welds
For placing the weld symbol on one side of the reference line, the arc spot welding is carried out from one side of the joint. The image below shows the different ways of indicating the number of welds both in the ISO and AWS standards.
c) Projection Welds
Both in ISO and AWS standards, the spot and projection weld symbols are identical, but with additional indications. The letter P is placed in front of the weld size in the ISO system. the letters PW are placed in the tail of the reference line in the AWS standard. A reference to projection size is indicated by a separate sketch in the tail in the AWS system. See details in the image below.
d) Seam Welds
The only difference in the meaning of the letters is that
In the AWS system, the letter e indicates the pitch of the welds (center to center). And in the ISO standard, the bracketed letter (e) refers to the distance between welds.
The image below shows the notation for sizes and spacing of intermittent seam welds.
The stud welding process is used to attach studs to a component in order to locate or secure other parts. It is generally applied to studs ranging from 1.6mm (1/16in) to 19mm (3/4in) in diameter. For larger studs, manual welding is used by covered electrodes to deposit a fillet weld. The fillet weld and weld all round symbols indicate these welds on a drawing. See the image below.
Surfacing Weld Symbol
Surfacing weld symbol can be used to point out cladding for corrosion resistance, hard facing with wear-resistant materials, or the build-up of surfaces to required dimensions. The surfacing symbol should point to the surface where the surfacing weld is to be deposited. By placing the dimension to the left of the weld symbol, the thickness of the weld is specified. And the area to be surfaced is indicated on the drawing.
a) Multiple Layers
Multiple reference lines may specify the multiple layers of surfacing welds, with the thickness of each layer specified by placing its dimension to the left of the weld symbol.
Non-Destructive Testing Symbols (AWS)
The image below shows AWS letter designations for (Nondestructive Testing) NDT.
Welding Symbols Advantages
Welding symbols are necessary and important graphical images that contain the very welding procedure. Without the symbol, welders, fabricators, and engineers cannot reach the prescribed frame of the project. These symbols are their guidelines while performing welding processes.
1. Welding symbols ensure consistent quality and production for custom metal fabrication. Weld symbols guide welders the things like where to place weld, size of weld, and kind of weld to apply for obtaining overall quality.
2. They help welding-machine operators while programming welding sequences when symbols clearly marked on the design diagram. This allows the operator in programming and ensures every weld joint is performed as per the exact standards outlined in the design document.
3. The symbols save the time needed to complete the drawing and improve clarity. Employ a set of weld symbols while preparing an edge for a butt/groove weld, and shape/size of fillet weld.
4. Using welding symbols results in less wastage of material. Because they guide the performer to the point sans wastage.
5. Welding symbols make it easy for welders/engineers to handle complicated shape.
6. Performing welds using symbols imparts maximum efficiency.
7. They also provide a smooth appearance, strength, and light-weight welding joints.
Welding symbols are a crucial part of laying welds as per the requirements. They are eyes for the welders and engineers to understand the structure. There are many welding symbols, the main being the basic and supplementary weld symbols. Other aspects of welding symbols are elements, dimensions, locations, standards, etc. So, the above-mentioned information is important for students, welders, fabricators, engineers, mechanics, and other professionals working in the welding industry.
Related: Other Welding Technology Topics