Quality, Reliability, and Performance - Delivered
[email protected]

Welding Seam Types, Symbols & Process Codes Explained

Last updated:
May 2, 2024
Share your like:

Table Of Contents

A weld seam refers to the joint part formed in the welded component after welding. The metal that makes up the weld seam, i.e., the weld metal, directly affects the performance of the welded components and structures due to its shape and quality. Therefore, welders should understand the types of weld seams and their representation symbols on engineering drawings.

I. Weld Seam Forms, Shapes, and Sizes

1. Weld Seam Forms

(1) According to different joint forms, it can be divided into five types: butt weld, fillet weld, plug weld, groove weld, and edge weld.

1) Butt weld.

A weld seam welded between the bevel surfaces of the workpieces or between the bevel surface of one part and the surface of another part.

2) Fillet weld.

A weld seam welded along the intersection line of two orthogonal or nearly orthogonal parts.

3) Terminal weld seam.

The weld seam formed by a terminal joint.

4) Plug weld seam.

Two parts are overlapped, one of which has a round hole, and the weld seam formed by welding the two plates in the round hole, only the fillet weld inside the hole is not considered a plug weld.

5) Slot weld seam.

Two plates are overlapped, one of which has a long hole, and the weld seam formed by welding the two plates in the long hole, only the fillet weld is not considered a slot weld.

(2) According to the different spatial positions of the weld seam

Can be divided into flat weld seam, vertical weld seam, horizontal weld seam, and overhead weld seam four forms.

(3) According to the different continuity of the weld seam

Divided into continuous welds and intermittent welds. Intermittent welds are further divided into staggered and parallel types, as shown in Figure 2-50. In addition to specifying the size of the weld toe K, the length L and spacing e of each segment of the intermittent weld should also be indicated, and the symbol “Z” represents the staggered weld.

Figure 2-50 Intermittent fillet weld
Figure 2-50 Intermittent fillet weld

a) Staggered
b) Parallel

(4) According to the different functions of the weld

Divided into load-bearing welds that bear loads, connecting welds that do not directly bear loads but only serve to connect, sealing welds mainly used to prevent fluid leakage, and positioning welds that are welded before formal welding to assemble and fix the position of joints on the workpiece with a shorter length.

(5) According to the shape of the weld and its position at the joint

Divided into butt welds that form butt joints; edge welds applied at the edge rolling of the workpiece; plug welds formed by welding in a round hole opened in one of two overlapped plates; circumferential welds distributed along the circumference of spherical or cylindrical workpieces with ends joined together; and flush welds whose surfaces are ground to be flush with the surface of the base material, etc.

2. Shape and size of the weld

(1) Weld width

The junction between the weld surface and the base material is called the weld toe. In the cross-section of a single-pass weld, the distance between the two weld toes is called the weld width, as shown in Figure 2-51.

Figure 2-51 Weld Width
Figure 2-51 Weld Width

a) T-joint

b) Butt joint

(2) Excess Height

In butt welds, the height of the weld metal above the line connecting the surface weld toes is called excess height, as shown in Figure 2-52. Excess height increases the cross-sectional area of the weld, improves strength, and can increase the sensitivity of X-ray films, but it is prone to stress concentration at the weld toes. Therefore, the excess height should not be lower than the base material, but also not too high. The national standard specifies that the excess height for shielded metal arc welding is 0~3mm, and for submerged arc welding, the excess height is 0~4mm.

Figure 2-52 Excess Height
Figure 2-52 Excess Height

(3) Penetration Depth

In the cross-section of the welded joint, the depth of melting of the base material is called penetration depth, as shown in Figure 2-53. When the filler metal material (welding rod or wire) is fixed, the size of the penetration depth is determined by the chemical composition of the weld.

Figure 2-53 Penetration Depth
Figure 2-53 Penetration Depth

a) Butt joint fusion depth
b) Lap joint fusion depth
c) T-joint fusion depth

(4) Weld thickness

In the cross-section of the weld, the distance from the front of the weld to the back of the weld is called the weld thickness, as shown in Figure 2-54.

Figure 2-54 Weld thickness of a butt weld
Figure 2-54 Weld thickness of a butt weld

(5) Shape and size of fillet welds

Based on the external shape of the fillet weld, fillet welds can be divided into two types: fillet welds with a raised surface are called convex fillet welds; fillet welds with a concave surface are called concave fillet welds, as shown in Figure 2-55. Under certain conditions, concave fillet welds have much less stress concentration than convex fillet welds.

Figure 2-55 Shape of fillet welds
Figure 2-55 Shape of fillet welds

a) Convex fillet weld
b) Concave fillet weld

1) Weld calculation thickness.

Draw the largest right-angled isosceles triangle within the cross-section of the fillet weld, the perpendicular length from the right-angle vertex to the hypotenuse is the weld calculation thickness. If the cross-section of the fillet weld is a standard isosceles right triangle, then the weld calculation thickness is equal to the weld thickness; in convex or concave fillet welds, the weld calculation thickness is less than the weld thickness.

2) Weld convexity.

In the cross-section of a convex fillet weld, the maximum distance between the weld toe line and the weld surface, as shown in Figure 2-55.

3) Weld concavity.

In the cross-section of a concave fillet weld, the maximum distance between the weld toe line and the weld surface, as shown in Figure 2-55b.

4) Weld leg.

In the cross-section of a fillet weld, the minimum distance from a weld toe on one workpiece to the surface of another workpiece; the weld leg size is the length of the right-angle side in the largest isosceles right triangle drawn in the cross-section, for convex fillet welds, the weld leg size is equal to the weld leg; for concave fillet welds, the weld leg size is less than the weld leg.

(6) Weld formation factor

During welding, the ratio of the weld width (B) to the calculated thickness of the weld (H) on the cross-section of a single weld seam (ψ=B/H) is called the weld formation factor, as shown in Figure 2-56. The smaller the weld formation factor, the narrower and deeper the weld, which makes it prone to porosity, slag inclusion, and cracking. Therefore, the weld formation factor should maintain a certain value, for example, the weld formation factor for submerged arc welding should be greater than 1.3.

Figure 2-56 Calculation of the Weld Formation Factor
Figure 2-56 Calculation of the Weld Formation Factor

(7) Fusion Ratio

Refers to the percentage of the base material that is melted into the weld metal during welding.

γ=FmFm+FH×100%

Where:

  • y is the fusion ratio, %;
  • m is the cross-sectional area of the melted base material, mm 2 ;
  • H is the cross-sectional area of the melted filler metal, mm 2 .

When welding high alloy steel and non-ferrous metals, the fusion ratio should be controlled to prevent welding defects.

II. Representation and Marking of Weld Symbols

The symbols used to mark the welding method, weld form, and weld dimensions on drawings are called weld symbols. Weld symbols generally consist of basic symbols and leader lines. Auxiliary symbols, supplementary symbols, and weld dimension symbols may also be added as necessary. According to the provisions of GB/T324-2008 “Representation of Weld Symbols”, weld symbols can be divided into the following types.

1. Basic Symbols

Basic symbols are used to represent the cross-sectional shape or characteristics of welds, see Table 2-13. The application of basic symbols is shown in Table 2-14.

No.NameSchematic diagramSymbol
1Edge-flanged weld (with complete edge fusion)
2I-shaped weld
3V-shaped weld
4Single-bevel V-shaped weld
5V-shaped weld with blunt edge
6Single-bevel V-shaped weld with blunt edge
7U-shaped weld with blunt edge
8J-shaped weld with blunt edge
9Backing weld
10Fillet weld
11Plug weld or slot weld
12Spot weld
13Seam weld
14Steep-flanked V-shaped weld
15Steep-flanked single V-shaped weld
16End weld
17Build-up weld
18Flat brazed joint
19Beveled brazed joint
20Folded brazed joint

Table 2-14: Examples of Basic Symbol Applications

No.SymbolDiagramAnnotation Example
1
2
3
4
5

2. Combination of Basic Symbols

Note: When welding double-sided welds or joints, basic symbols can be combined, see Table 2-15.

Table 2-15 Combination of Basic Symbols

No.SymbolDiagramAnnotation Example
1Double-sided V-groove weld (X-weld)
2Double-sided single V-groove weld (K-weld)
3Double-sided V-groove weld with a blunt edge
4Double-sided single V-groove weld with a blunt edge
5Double-sided U-groove weld

3. Supplementary Symbols

Supplementary symbols are used to provide additional information about certain characteristics of welds or joints (such as surface shape, backing, weld distribution, welding location, etc.).

1) See Table 2-16 for supplementary symbols.

Table 2-16 Supplementary Symbols

No.NameSymbolDescription
1FlatThe weld seam surface is usually machined to be flat.
2ConcaveThe weld seam surface is recessed.
3ConvexThe weld seam surface protrudes.
4Smooth TransitionThe transition at the weld toe is smooth.
5Permanent BackingThe backing is permanently retained.
6Temporary BackingThe backing is removed after welding is completed.
7Three-Sided WeldThe weld is present on three sides.
8Peripheral WeldA weld applied along the perimeter of the workpiece; the location is marked at the intersection of the baseline and the arrow line.
9Field WeldA weld executed on-site.
10TailCan indicate the required information.

2) Tables 2-17 and 2-18 provide examples of the application and marking of supplementary symbols.

Table 2-17 Examples of Application of Supplementary Symbols

No.NameSymbolDescription
1Flat V-groove weld
2Raised double V-groove weld
3Recessed fillet weld
4Flat V-groove weld with a backing weld
5Fillet weld with a smooth surface transition

Table 2-18 Examples of Marking of Supplementary Symbols

No.SymbolDiagramAnnotation Example
1
2
3

4. Leader Line

The leader line consists of an arrow line, reference lines (solid and dashed), and a tail, as shown in Figure 2-57.

Figure 2-57 Guide Wire

(1) Arrow Line

The joint directly pointed to by the arrow is the “arrow side” of the joint, and the opposite side is the “non-arrow side” of the joint, as shown in Figure 2-58.

Figure 2-58 Schematic Diagram of the "Arrow Side" and "Non-Arrow Side" of a Joint
Figure 2-58 Schematic Diagram of the “Arrow Side” and “Non-Arrow Side” of a Joint

(2) Datum Line

The datum line should generally be parallel to the bottom edge of the drawing, but can also be perpendicular if necessary. The positions of solid and dashed lines can be interchanged as needed. When marking symmetrical welds or double-sided welds, dashed lines can be omitted.

(3) Tail

Generally omitted. The tail part is only added when there are additional requirements or explanations for the weld.

III. Simplified Representation of Weld Symbols

When it is necessary to simply draw welds in the drawing, they can be represented by views, sectional views, or cross-sectional views, or can be schematically represented by isometric drawings.

1. View

When representing welds with a view, the drawing method is as shown in Figure 2-59, where the welds represented by Figure 2-59a and b series of solid lines are allowed to be drawn by hand; the weld represented by Figure 2-59c is indicated with a thick line.

Figure 2-59 Drawing method for representing welds in a view
Figure 2-59 Drawing method for representing welds in a view

In the view representing the weld surface, the outline of the weld is usually drawn with a thick solid line. If necessary, the shape of the bevel before welding can be drawn with a thin solid line, as shown in Figure 2-60.

Figure 2-60 shows the view of the weld end face.
Figure 2-60 shows the view of the weld end face.

2. Sectional view or cross-sectional view

In a sectional view or cross-sectional view, the metal fusion zone of the weld is usually shaded in black, as shown in Figure 2-61a. If it is also necessary to represent the shape of the bevel, etc., the fusion zone part is usually outlined with a thick solid line, and if necessary, the shape of the bevel before welding is drawn with a thin solid line, as shown in Figure 2-61b.

Figure 2-61 Sectional (surface) view representing the weld
Figure 2-61 Sectional (surface) view representing the weld

3. Isometric drawing

The method of representing welds with an isometric drawing is as shown in Figure 2-62.

Figure 2-62 shows the axonometric drawing of the weld
Figure 2-62 shows the axonometric drawing of the weld

4. Enlarged view

When necessary, the weld area can be enlarged and labeled as shown in Figure 2-63.

Figure 2-63 Enlarged view of the weld
Figure 2-63 Enlarged view of the weld

IV. Dimensions and labeling of weld symbols

1. Rules for dimensioning weld symbols

1) Horizontal dimensions are labeled on the left side of the basic symbol.

2) Vertical dimensions are labeled on the right side of the basic symbol.

3) Bevel angle, groove angle, and root gap are labeled on the top or bottom of the basic symbol.

4) The quantity of identical welds is labeled at the end.

5) When there are many dimensions that are difficult to distinguish, the corresponding dimension symbols can be marked in front of the dimension data.

6) The dimensions determining the weld position should not be marked in the weld symbol, but should be marked on the drawing.

7) When there are no dimension markings on the right side of the basic symbol and no other instructions, it means that the weld is continuous along the entire length of the workpiece.

8) When there are no dimension markings on the left side of the basic symbol and no other instructions, it means that the butt weld should be fully penetrated.

9) When plug welds and slot welds have beveled edges, the dimensions of their bottom should be marked.

2. Method of marking weld dimension symbols

The method of marking weld dimension symbols is shown in Figure 2-64.

Figure 2-64 Method of marking weld dimension symbols
Figure 2-64 Method of marking weld dimension symbols

3. Common weld dimension symbols

The common weld dimension symbols are shown in Table 2-19.

Table 2-19 Common Weld Seam Size Symbols

SymbolNameDiagram
δWorkpiece Thickness
αBevel Angle
βBevel Face Angle
bRoot Gap
PBlunt Edge
RRoot Radius
HBevel Depth
SEffective Weld Thickness
cWeld Width
KWeld Toe Size
dSpot Weld: Nugget Diameter
Plug Weld: Hole Diameter
nNumber of Weld Segments
lWeld Length
eWeld Spacing
NNumber of Identical Welds
hExcess Height

4. Supplementary Explanation for Weld Seam Size Symbol Annotation

1) Peripheral weld.

When the weld seam surrounds the workpiece, a circular symbol can be used, as shown in Figure 2-65.

Figure 2-65 Annotation of Peripheral Weld

2) Field weld.

A small flag represents a field or on-site weld, as shown in Figure 2-66.

Figure 2-66 Annotation of Field Weld

5. Application of Weld Seam Symbol Size Annotation

The application of weld seam symbol size annotation is shown in Table 2-20.

No.NameDiagramDimension SymbolAnnotation Method
1Butt WeldS: Effective Thickness of Weld
2Continuous Fillet WeldK: Size of Weld Leg
3Intermittent Fillet WeldI: Weld Length
e: Spacing
n: Number of Weld Segments
K: Size of Weld Leg
4Staggered Intermittent Fillet Weldl: Weld Length
e: Spacing
n: Number of Weld Segments
K: Size of Weld Leg
5Plug Weld
or
Slot Weld
l: Weld Length
e: Spacing
n: Number of Weld Segments
c: Slot Width
e: Spacing
n: Number of Weld Segments
d: Hole Diameter
6Spot Weldn: Number of Weld Spots
e: Distance Between Weld Spots
d: Fusion Core Diameter
7Seam Weldl: Weld Length
e: Spacing
n: Number of Weld Segments
c: Weld Width

V. Simplified notation method for weld symbols

The simplified notation method for weld symbols is shown in Table 2-21.

Table 2-21 Simplified notation method for weld symbols

No.Annotation methodExplanationDiagram
1Single AnnotationWhen annotating the size of staggered symmetric welds in a weld symbol, it is permissible to annotate on the reference line just once.
2Omission of Segment Count AnnotationWhen there is no strict requirement for the number of segments for intermittent welds, symmetrical intermittent welds, and staggered intermittent welds, omitting the weld segment count is allowed.
3Collective AnnotationIn the same drawing, when several welds have the same bevel size and weld symbols, collective annotation can be used.
4Annotation of Weld QuantityIn the same drawing, when several welds are in the same position within a joint, simplification can be achieved by annotating the same weld quantity at the end of the weld symbol. However, other types of welds still need to be annotated separately.
5Simplified Code AnnotationTo simplify the annotation method or when the annotation location is limited, simplified weld codes can be annotated. However, the meanings of these simplified codes must be explained either below the drawing or near the title bar. When simplified codes are used, the codes and symbols explained below the drawing or near the title bar should be 1.4 times the size of those annotated on the drawing.
6Omission of Reference Line or Weld Length AnnotationIn cases where it does not lead to misunderstanding, and when the arrow line points to the weld while there are no weld requirements on the non-arrow side, omitting the reference line (dashed line) on the non-arrow side is allowed. When the start and end positions of the weld length are clear (as determined by the dimensions of the components, etc.), omitting the weld length in the weld symbol is permitted.

Note:
1. The positioning dimensions of the weld location should comply with relevant regulations.

2. When all the welds on the same drawing use the same welding method, the code indicating the welding method at the tail of the weld symbol can be omitted and not marked, but it must be stated in the technical requirements or other technical documents that “all welds use … welding” etc.; when most of the welding methods are the same, it can also be stated in the technical requirements or other technical documents that “except for the welding methods indicated in the drawing, the rest of the welds use … welding” etc.

3. When all the welds in the same drawing are the same and their positions are clearly indicated by the pictorial method, they can be uniformly indicated by symbols in the technical requirements or described in text; when some of the welds are the same, the same method can be used for representation, but the remaining welds should be clearly marked in the drawing.

VI. Welding and related process method codes

1. Welding and related process method codes (see Table 2-22)

Table 2-22 Welding and related process method codes (excerpted from GB/T5185—2005)

CodeWelding Method
1Arc Welding
101Metal Arc Welding
11Gasless Arc Welding
111Shielded Metal Arc Welding
112Gravity Welding
114Self-Shielded Flux-Cored Arc Welding
12Submerged Arc Welding
121Single Wire Submerged Arc Welding
121Electroslag Submerged Arc Welding
123Multi-Wire Submerged Arc Welding
124Metal Powder Added Submerged Arc Welding
125Flux-Cored Submerged Arc Welding
13Gas Shielded Metal Arc Welding
131Metal Inert Gas Welding (MIG)
135Metal Active Gas Welding (MAG)
156Non-Inert Gas Shielded Flux-Cored Arc Welding
137Inert Gas Shielded Flux-Cored Arc Welding
14Non-Consumable Electrode Gas Shielded Arc Welding
141Tungsten Inert Gas Welding (TIG)
15Plasma Arc Welding
151Plasma Arc MIG Welding
152Plasma Arc Powder Surfacing
18Other Arc Welding Methods
185Magnetic Arc Butt Welding
2Resistance Welding
21Spot Welding
211Single-Sided Spot Welding
212Double-Sided Spot Welding
22Seam Welding
221Lap Seam Welding
222Flat Seam Welding
225Thin Film Butt Seam Welding
226Band Seam Welding
23Projection Welding
231Single-Sided Projection Welding
232Double-Sided Projection Welding
24Flash Welding
241Preheated Flash Welding
242Non-Preheated Flash Welding
25Resistance Butt Welding
29Other Resistance Welding Methods
291High-Frequency Resistance Welding
3Gas Welding
31Oxy-Fuel Welding
311Oxyacetylene Welding
312Oxypropane Welding
313Oxyhydrogen Welding
4Pressure Welding
41Ultrasonic Welding
42Friction Welding
44High Energy Rate Welding
45Diffusion Welding
47Pneumatic Welding
48Cold Pressure Welding
5High Energy Beam Welding
51Electron Beam Welding
511Vacuum Electron Beam Welding
512Non-Vacuum Electron Beam Welding
52Laser Welding
521Solid-State Laser Welding
522Gas Laser Welding
7Other Welding Methods
71Thermit Welding
72Electroslag Welding
73Gas Shielded Arc Spot Welding
74Induction Welding
741Induction Butt Welding
742Induction Seam Welding
75Light Radiation Welding
753Infrared Welding
77Impact Resistance Welding
78Stud Welding
782Resistance Stud Welding
783Arc Stud Welding with Ceramic Ferrule or Shielding Gas
784Short-Circuit Arc Stud Welding
785Capacitor Discharge Stud Welding
786Capacitor Discharge Stud Welding with Ignition Tip
787Arc Stud Welding with Fusible Collar
788Friction Stud Welding
8Cutting and Gas Cutting
81Flame Cutting
82Arc Cutting
821Air Arc Cutting
822Oxy-Arc Cutting
83Plasma Arc Cutting
84Laser Cutting
86Flame Gouging
87Carbon Arc Gouging
871Air Carbon Arc Gouging
872Oxy Carbon Arc Gouging
88Plasma Gouging
9Brazing, Soldering, and Brazing
91Hard Brazing
911Infrared Hard Brazing
912Flame Hard Brazing
913Furnace Hard Brazing
914Dip Hard Brazing
915Salt Bath Hard Brazing
916Induction Hard Brazing
918Resistance Hard Brazing
919Diffusion Hard Brazing
924Vacuum Hard Brazing
93Other Hard Brazing Methods
94Soft Soldering
941Infrared Soft Soldering
942Flame Soft Soldering
943Furnace Soft Soldering
944Dip Soft Soldering
945Salt Bath Soft Soldering
946Induction Soft Soldering
947Ultrasonic Soft Soldering
948Resistance Soft Soldering
949Diffusion Soft Soldering
951Wave Soldering
952Soldering Iron
954Vacuum Soft Soldering
956Drag Soldering
96Other Soft Soldering Methods
97Brazing
971Gas Brazing
972Arc Brazing

Note: The following welding methods have been removed in the new standard (GB/T5185—2005) from the old standard (GB/T5185—1985), these welding methods may still be used for special occasions, or appear in various documents from the past.

  • 113 Bare Wire Arc Welding
  • 322 Air-Propane Welding
  • 115 Coated Wire Arc Welding
  • 43 Forge Welding
  • 118 Lying Welding
  • 752 Arc Beam Welding
  • 149 Atomic Hydrogen Welding
  • 781 Electric Arc Stud Welding
  • 181 Carbon Arc Welding
  • 917 Ultrasonic Brazing
  • 32 Air Gas Welding
  • 923 Friction Brazing
  • 321 Air Acetylene Welding
  • 952 Scraping Soldering

Examples of welding method code notation (see Table 2-23)

Table 2-23 Examples of welding method code notation

Annotation ExampleMeaning
Symmetrical fillet welds with a leg size of 5mm are welded on the construction site using shielded metal arc welding.
With a blunt-edged V-groove weld, first perform root welding with plasma arc welding, then cover the surface with submerged arc welding.
Request FREE Quote
Contact Form

Latest Posts
Stay up to date with new and exciting content on various topics, including useful tips.
Talk To An Expert
Contact Us
Our sales engineers are readily available to answer any of your questions and provide you with a prompt quote tailored to your needs.

Request a Custom Quote

Contact Form

Request A Custom Quote
Get a personalized quote tailored to your unique machining needs.
© 2024 Artizono. All rights reserved.
Get Free Quote
You will get our expert reply within 24 hours.
Contact Form