Welding Symbols Explained: Complete List with Diagrams

1. Scope

This standard outlines the method of presenting welding symbols. It is applicable to both metal fusion welding and resistance welding.

2. Normative References

GB/T 5185 Designation of Metal Welding and Brazing Methods in Drawings; GB/T 12212 Technical Drawings – Dimension, Proportions, and Simplified Representation of Welding Symbols.

Welding Symbols

3. Basic Requirements

3.1 The welding symbol should clearly indicate the type of weld to be made and should not include excessive notes. The representation of the weld can be through the use of a weld graphic method or a weld symbol annotation method. The method of weld symbol marking is generally preferred, but if it’s unclear or if the graphical method is simpler, it can be used instead.

3.2 The welding symbol consists of a basic symbol and leader, and additional symbols such as an auxiliary symbol, supplementary symbol, and weld size symbol can be added if needed. The scale, size, and representation method of the graphic symbols should comply with GB/T 12212. For commonly used graphic methods in GB/T 12212, see Appendix C (normative appendix).

3.3 When professional standards specify the weld size and process, these should be indicated in the welding symbol. The welding method marked on the drawing should be in accordance with Appendix B (normative appendix). Any post-welding processing such as spading, grinding, or cutting should be indicated in the technical requirements.

I. Basic Forms of Weld Seam Overlap

1. Butt Joint

Butt Joint

2. Overlap

Overlap

3. Right Angle Connection

Right Angle Connection

4. T-shaped Joint

T-shaped Joint

5. Bevel Joint:

Bevel Joint

II. Basic Fracture Shapes of Weld Seams

No.Schematic DiagramBevel FormWelding symbols
1I-shaped GrooveI-shaped Groove 
2K-shaped GrooveK-shaped Groove 
3V-shaped GrooveV-shaped Groove 
4X-shaped GrooveX-shaped Groove 
5Y-shaped GapY-shaped Gap 
6X-shaped (with pure edge)X-shaped (with pure edge) 
7Oblique V-shaped Gap 
8Oblique Y-shaped GapOblique Y-shaped Gap 
9Overlap (three-side weld)Overlap (three-side weld) 
10U-shaped GapU-shaped Gap 
11Single-sided U-shaped BreakSingle-sided U-shaped Break 
12Spot WeldingSpot Welding 
13Irregular BreakIrregular Break 
14Irregular BreakIrregular Break 
15Irregular BreakIrregular Break

III. Welding Symbols

1. Definition of Welding Symbols

These are symbols used to indicate welding methods, weld form, and weld size, among other technical content on a drawing.

2. Components of Welding Symbols

(1) Weld symbols:

1. Basic Symbols: Symbols representing the cross-sectional shape of the weld.

2. Supplementary Symbols: Symbols indicating the surface shape of the weld.

3. Additional Symbols: Symbols used to further explain certain characteristics of the weld.

(2) Reference Line:

Composed of an arrow line and a reference line.

(3) Weld Size Symbols:

Symbols indicating the dimensions of the weld shape.

3. Standard Position of Weld Symbols on Drawings

The standards specify clear rules for the placement of weld symbols, dimension symbols, and dimension values on the reference line. When creating welding diagrams, these rules must be strictly followed.

Symbols and numeric values are marked in seven zones, A~G, relative to the reference line. The positions of these zones relative to the reference line are fixed, regardless of changes in the direction of the arrow line, their position relative to the reference line will not change.

Basic Annotation Format of Weld Symbols

A Zone: Main functional area: Marks basic symbols, special symbols, backing strip symbols in supplementary symbols, and symbols for plane, convex, and concave in auxiliary symbols.

B Zone: Supplementary functional area: Located above or below the A Zone, marking the groove angle α, groove surface angle β, and root gap b in the weld size.

C Zone: On the left side of the basic symbol, marking the dimension symbols and values on the cross section of the weld, such as blunt edge p, groove depth H, weld angle size K, reinforcement h, effective weld thickness S, root radius R, weld width C, and fusion core diameter d.

D Zone: On the right side of the basic symbol, marking staggered weld symbols, and marking the longitudinal (length direction) size values of the weld, such as the number of weld sections n, weld length l, and weld spacing e.

E Zone: Marks the three-side weld symbols in supplementary symbols.

F Zone: Marks the field weld symbols and surrounding weld symbols in supplementary symbols.

G Zone: Marks the tail symbols in supplementary symbols. After the tail symbols, the number of identical welds N, welding method code, weld quality, and inspection requirements are marked.

4. Representation Codes of Common Welding Methods in Drawings

Refer to the table below (note: the table is not provided in the query).

Code NameWelding Methods
135MAG Welding (CO2)
21Spot Welding
141TIG Welding
131MIG Welding
23Projection Welding
3Gas Welding
2Resistance Welding
111Manual Arc Welding (Coated Electrode)
114Flux-cored Wire Arc Welding
12Submerged Arc Welding
25Resistance Spot Welding
952Soldering Iron Soft Brazing
751Laser Welding
155Plasma Arc MIG Welding

5. For instance

(Example 1)

Indication: Weld height is 3, staggered welding, weld seam length is 50, interval is 30, site welding is required.

Example 2:

Statement: Spot weld diameter is 5, the number of spot welds is 10, and the interval is 30.

Example 3:

Indication: The weld height is 3, with full welding around. The joint is made using CO2 gas shielded welding, with a total of 5 locations.

Example 4:

Indication: The weld height is 3, with a bevel V-groove, the weld surface is ground flat, the weld length is 30, in total 5 segments, and the welding is carried out using CO2 gas shielded welding.

6. Basic symbols

The basic symbol represents the cross-sectional shape of the weld, as illustrated in Table 1.

Table 1 Basic Welding Symbols

Serial NoSymbol nameSketch MapWeld symbol
1Rolled edge weld (fully melted rolled edge)

Note: incompletely melted rolled edge weld is indicated by I-shaped weld symbol, and the effective weld thickness S is added, as shown in Table 7
Rolled edge weldRolled edge weld 
2I-shaped weldI-shaped weldI-shaped weld 
3V-shaped weldV-shaped weldV-shaped weld 
4Unilateral V-shaped weldUnilateral V-shaped weldUnilateral V-shaped weld 
5V-shaped weld with blunt edgeV-shaped weld with blunt edgeV-shaped weld with blunt edge 
6Single V-shaped weld with blunt edgeSingle V-shaped weld with blunt edgeSingle V-shaped weld with blunt edge 
7U-shaped weld with blunt edgeU-shaped weld with blunt edgeU-shaped weld with blunt edge 
8J-shaped weld with blunt edgeJ-shaped weld with blunt edgeJ-shaped weld with blunt edge 
9Sealing weldSealing weldSealing weld 
10Fillet weldFillet weldFillet weld 
11Plug weld or slot weldPlug weld or slot weldPlug weld or slot weld 
12Spot weldSpot weldSpot weld 
13Seam weldSeam weldSeam weld 

7. Auxiliary symbols

1. Auxiliary welding symbols represent the shape characteristics of the weld surface and are shown in Table 2.

Table 2 Auxiliary Welding Symbols

Serial NoSymbol nameSketch MapSymbolExplain
1Plane symbolPlane symbolPlane symbol The weld surface is flush
2Concave symbolConcave symbol Concave symbol Weld surface depression
3Convex symbolConvex symbolConvex symbol Raised weld surface

Note: Auxiliary symbols can be omitted if the surface shape of the weld does not need to be specified.

2. See Table 3 for application examples of auxiliary symbols.

Table 3 Application Examples of Auxiliary Symbols

Serial NoSymbol nameSketch MapSymbol
1Plane V butt weldPlane V butt weld Plane V butt weld 
2Convex X butt weldConvex X butt weld Convex X butt weld 
3Concave fillet weldConcave fillet weld Concave fillet weld 
4V-shaped weld of flat backV-shaped weld of flat back V-shaped weld of flat back 

8. Supplementary symbols

Supplementary symbols are used to add additional information about the characteristics of the welds. For examples of supplementary symbols, refer to Table 4.

See GB/T 5185 for symbols of welding process methods.

Table 4 Supplementary Symbols

Serial NoSymbol nameSketch MapSymbolExplain
1Symbol with backing plateSymbol with backing plateSymbol with backing plate Indicates that there is a backing plate at the bottom of the weld
2Three side weldThree side weldThree side weld Indicates that there are welds on three sides
3Peripheral weldPeripheral weldPeripheral weld Indicates welding around the workpiece
4Site Symbols Site Symbols Indicates welding on site
5Tail symbol Tail symbol Mark welding process method

Table 5 Example of supplementary symbol application

Serial NoSketch MapDimension exampleExplain
1Indicates that there is a backing plate at the bottom of the back of the V-shaped weldIndicates that there is a backing plate at the bottom of the back of the V-shaped weldIndicates that there is a backing plate at the bottom of the back of the V-shaped weld
2There are welds on three sides of the workpiece, and the welding method is manual arc weldingThere are welds on three sides of the workpiece, and the welding method is manual arc weldingThere are welds on three sides of the workpiece, and the welding method is manual arc welding
3It means welding around the workpiece on siteIt means welding around the workpiece on siteIt means welding around the workpiece on site

IV. Position of Welding Symbols on Drawings

1. Basic requirements

Complete weld representation methods consist of the basic symbol, auxiliary symbol, supplementary symbol, leader, dimension symbol, and data. The leader line is composed of an arrow leader line (also known as an arrow line) and a datum line, which can be either a solid line or a dotted line, as illustrated in Figure 1.

Fig. 1 Leader line

2. Relationship between arrow line and welding joint

Two terms are used to describe the relationship between the arrow lines and the joints:

a. Arrow side of the connector;

b. Non-arrow side of the connector.

Refer to Figures 2 and 3 for a description of these two terms.

(a) Weld seam on arrow side

(b) Weld seam is on the non arrow side

Fig. 2 T-joint with single fillet weld

Fig. 3 Cross joint of double fillet weld

3. Arrow position

Generally, there is no specific requirement for the position of the arrow line relative to the weld, as shown in Figures 4(a) and (b). However, when marking single-sided V-shaped, single-sided V-shaped with a blunt edge, and J-shaped welds, the arrow must point towards the workpiece with the groove, as shown in Figures 4(c) and (d). If necessary, bending the arrow line once is allowed, as shown in Figure 5.

Fig. 4 Location of arrow line
Fig. 5 Curved arrow line

4. Location of reference line

The dotted line of the reference line can be drawn either above or below the solid line of the reference line. The datum line must be parallel to the bottom edge of the drawing.

5. Position of datum mark relative to datum line

a. If the weld is on the arrow side of the joint, the basic symbol shall be marked on the solid line side of the datum line, as shown in Fig. 6 (a);

b. If the weld is on the non-arrow side of the joint, the basic symbol shall be marked on the dotted line side of the datum line, as shown in Fig. 6 (b);

c. When symmetrical welds and double-sided welds are marked, dotted lines may not be necessary, as shown in Fig. 6 (c) and (d).

(a) The weld is on the arrow side of the joint
(b) The weld is on the non arrow side of the joint.
(c) Symmetrical weld
(d) Double side weld

Fig. 6 Position of basic symbol relative to reference line

V. Weld Size Symbol and Its Marking Position

1. Basic Dimensions and Related Concepts of Welds

1. Weld Toe:

The junction between the surface of the weld and the parent metal.

2. Weld Width (B):

The distance between the two weld toes on the surface of the weld.

3. Weld Thickness:

In the cross-section of the weld, the distance from the front of the weld to the back of the weld.

4. Leg Size:

The length of the right-angled side in the largest isosceles right-angled triangle drawn in the cross-section of the fillet weld.

5. Weld Leg:

In the cross-section of the fillet weld, the shortest distance from a weld toe on one right-angled surface to another right-angled surface.

6. Penetration Depth:

In the cross-section of the weld joint, the depth of melting of the parent metal or the previous weld seam.

7. Welding Form Factor:

The ratio of weld width B to calculated weld depth H on the single seam cross-section during fusion welding.

8. Reinforcement:

The maximum height of the weld metal that exceeds the line on the surface of the parent metal.

9. Weld Root:

The junction of the back of the weld and the parent metal.

10. Crater

During arc welding, a depression formed at the end of the welding path due to improper arc breaking or arc extinguishing.

11. Weld Pool

During fusion welding, under the influence of the welding heat source, the part of the metal on the workpiece that forms a certain geometric shape and becomes liquid.

Figure 1 Weld Seam Formation Coefficient (¢) = B/H
Figure 2

12. Kerf Angle:

The angle between two kerfs;

13. Angle of groove surface:

The angle between the end face of the groove to be machined and the groove surface:

2. General requirements

2.1 If necessary, datum symbols can be provided with dimension symbols and data. See Table 6 for dimension symbols.

Table 6 Weld Size Symbols

SymbolSymbol nameExample diagramSymbolSymbol nameExample diagram
δWorkpiece thicknessWorkpiece thicknesseWeld spacingWeld spacing
αGroove angleGroove angleKFillet sizeFillet size
bRoot gapRoot gapdNugget diameterNugget diameter
PBlunt edgeBlunt edgeSEffective thickness of weldEffective thickness of weld
cWeld widthWeld widthNNumber of identical welds symbolNumber of identical welds symbol
RRoot radiusRoot radiusHGroove depthGroove depth
LWeld lengthWeld lengthhSurplus heightSurplus height
nNumber of weld segmentsNumber of weld segmentsβGroove face angleGroove face angle

2.2 The marking principles for the weld size symbol and data are illustrated in Figure 7.

a. The dimensions of the cross-section of the weld are indicated on the left side of the basic symbol;

b. The dimension in the length direction of the weld is indicated on the right side of the basic symbol;

c. The groove angle, groove face angle, and root gap dimension are indicated on the top or bottom of the basic symbol;

d. The number symbol for the same weld is indicated at the end;

e. When there are many dimension data to be marked and they are difficult to distinguish, corresponding dimension symbols can be added in front of the data for clarity.

Fig. 7 Marking principle of weld size

2.3 See Table 7 for the example of weld size marking.

Table 7 Example of Weld Dimension

Serial NoWeld nameSketch MapWelding dimension symbolExample
1Butt weldButt weldS: Effective thickness of weldEffective thickness of weld
Butt weldEffective thickness of weld
Butt weldEffective thickness of weld
2Crimping weldCrimping weldS: Effective thickness of weldCrimping weld
Crimping weldCrimping weld
3Continuous fillet weldContinuous fillet weldK: Fillet sizeContinuous fillet weld
4Intermittent fillet weldIntermittent fillet weldL: Weld length, excluding crater; e: weld gap ;n: number of weld segmentsIntermittent fillet weld
5Staggered intermittent fillet weldStaggered intermittent fillet weldL: Weld length, excluding crater;e: weld gap;n: number of weld segments; K: weld fillet sizeStaggered intermittent fillet weld
6Plug weld or slot weldPlug weldL: Weld length, excluding crater; e: weld gap; n: number of weld segments; c: slot width.Plug weld
slot welde: Weld clearance; n: number of weld segments; d: diameter of hole.slot weld
7Seam weldSeam weldL: Weld length, excluding crater; e: weld gap; n: number of weld segments; c: weld width.Seam weld
8Spot weldSpot weldn: Number of weld segments; e: spacing; d: weld spot diameter.Spot weld

3. Description of dimension symbols

3.1 The size for determining the position of the weld shall be indicated on the drawing rather than within the weld symbol.

3.2 If no marking is present on the right side of the basic symbol and no further information is given, it is assumed that the weld is continuous along the entire length of the workpiece.

3.3 If there is no marking on the left side of the basic symbol and no other information is given, it is assumed that the butt weld should be completely welded.

3.4 When the plug weld and groove weld have beveled edges, the size of the bottom of the hole should be marked.

VI. Example of Symbol Application

Appendix A

(Informative appendix)

Example of symbol application

A. 1 Application of basic symbols

See Table A.1 for examples of basic symbols.

A. 2 Basic symbol combination

See Table A.2 for application examples of basic symbol combination.

A. 3 Combination of basic symbols and auxiliary symbols

See Table A.3 for examples of the combination of basic symbols and auxiliary symbols.

A. 4 Special cases

See Table A.4 for the marks of flared weld, unilateral flared weld, stack weld and lock edge weld.

Table A.1 Application examples of basic symbols

Table A.2 Example of basic symbol combination

Table A.3 Examples of combination of basic symbols and auxiliary symbols

Table A.4 Marking of Special Welds

Appendix B

(Normative appendix)

Welding method and its name

B. 1 Marking of welding method in drawings

When various welding methods are marked on the drawings, Chinese characters shall be used instead of the codes specified in GB/T 5185.

B. 2 Common welding methods and their names

Common welding methods and their names are as follows:

a) Manual arc welding (coated electrode MIG welding);

b) Submerged arc welding;

c) MIG welding: Molten inert gas protection welding;

d) MAG welding: Molten non inert gas protection welding;

e) TIG: Tungsten inert gas welding.

f) Spot welding;

g) Oxygen acetylene welding;

h) Energy storage welding;

i) Flame brazing;

j) Induction brazing;

k) Soldering (tin).

Appendix C

(Normative appendix)

Graphic method

C. 1 General

When a simple representation of the weld is needed in the drawing, it can be shown through views, cross-sectional views, or cross-sectional drawings. This appendix provides a straightforward method commonly used by companies as outlined in GB/T 12212 for ease of use. For more information, refer to GB/T 12212.

C. 2 Views

C. 2.1 The drawing method of welds is shown in Fig. C.1 and Fig. C.2 (a series of fine solid line segments representing welds can be drawn by hand).

It is also allowed to use thick lines (2b ~ 3b) to represent welds, as shown in Fig. C.3.

However, in the same drawing, only one painting method is allowed.

Drawing method of welds

C. 2.2 In the representation of the end face of the weld, a thick solid line is typically used to outline the contour of the weld.

If needed, a thin solid line can be used to depict the groove shape before welding, as depicted in Figure C.4.

C. 3 Sectional view or sectional view

In sectional or profile views, the metal fusion welding area of the weld is typically marked in black, as depicted in Figure C.5. If the groove shape needs to be indicated as well, the fusion welding area can also be represented as outlined in Clause C.2.2, as shown in Figure C.6.

Fig. C.5
Fig. C.6

VII. Welding Symbol Examples

I-shaped weld
V-shaped weld
Unilateral V-shaped weld
V-shaped weld with blunt edge
Single V-shaped weld with blunt edge
U-shaped weld with blunt edge
J-shaped weld with blunt edge
Fillet weld
Sealing weld
Plug weld or slot weld
Spot weld
Plane connection (brazing)
Seam weld
Double V weld (X weld)
Double sided single V weld (K weld)
Double sided V-shaped weld with blunt edge
Double sided single V weld with blunt edge
Double U-shaped weld with blunt edge
Don't forget, sharing is caring! : )
Shane
Author

Shane

Founder of MachineMFG

As the founder of MachineMFG, I have dedicated over a decade of my career to the metalworking industry. My extensive experience has allowed me to become an expert in the fields of sheet metal fabrication, machining, mechanical engineering, and machine tools for metals. I am constantly thinking, reading, and writing about these subjects, constantly striving to stay at the forefront of my field. Let my knowledge and expertise be an asset to your business.

Up Next

Mastering CAD/CAM: Essential Technologies Explained

Basic Concepts of Computer-Aided Design and Computer-Aided Manufacturing Computer-aided design and computer-aided manufacturing (CAD/CAM) is a comprehensive and technically complex system engineering discipline that incorporates diverse fields such as computer [...]

Virtual Manufacturing Explained: Concepts & Principles

Concept of Virtual Manufacturing Virtual Manufacturing (VM) is the fundamental realization of the actual manufacturing process on a computer. It utilizes computer simulation and virtual reality technologies, supported by high-performance [...]

Understanding Flexible Manufacturing Systems: A Guide

A Flexible Manufacturing System (FMS) typically employs principles of systems engineering and group technology. It connects Computer Numerical Control (CNC) machine tools (processing centers), coordinate measuring machines, material transport systems, [...]

Exploring 4 Cutting-Edge Nanofabrication Techniques

Just as manufacturing technology plays a crucial role in various fields today, nanofabrication technology holds a key position in the realms of nanotechnology. Nanofabrication technology encompasses numerous methods including mechanical [...]

Ultra-Precision Machining: Types and Techniques

Ultra-precision machining refers to precision manufacturing processes that achieve extremely high levels of accuracy and surface quality. Its definition is relative, changing with technological advancements. Currently, this technique can achieve [...]

Exploring High-Speed Cutting: Tech Overview & Application

Cutting machining remains the most prominent method of mechanical processing, holding a significant role in mechanical manufacturing. With the advancement of manufacturing technology, cutting machining technology underwent substantial progress towards [...]

Top 7 New Engineering Materials: What You Need to Know

Advanced materials refer to those recently researched or under development that possess exceptional performance and special functionalities. These materials are of paramount significance to the advancement of science and technology, [...]

Metal Expansion Methods: A Comprehensive Guide

Bulge forming is suitable for various types of blanks, such as deep-drawn cups, cut tubes, and rolled conical weldments. Classification by bulge forming medium Bulge forming methods can be categorized [...]
MachineMFG
Take your business to the next level
Subscribe to our newsletter
The latest news, articles, and resources, sent to your inbox weekly.
© 2024. All rights reserved.

Contact Us

You will get our reply within 24 hours.