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Welding Symbol Details: Interpretation Based on the *** Standard GB/T 10044-2006 The welding symbols are the core carrier for transmitting welding process information in fields such as offshore platform manufacturing, offshore platform steel structure engineering, and pressure vessels. Through standardized graphics, letters, and numbers, they precisely describe the shape, size, position, and processing requirements of the weld seam, and are the key technical document for guiding welding production and ensuring quality. This article, in combination with the *** standard GB/T 10044-2006 "Representation Methods of Welding Symbols", provides a detailed analysis of the constituent elements, annotation rules, and typical applications of welding symbols.
This article focuses on the above-mentioned welding symbol abbreviations. If there are any incorrect descriptions, we sincerely invite all leaders to provide guidance. Thank you!! If you like this article, please leave your follow.
The basic framework of the welding symbol consists of the baseline and the arrow, which together determine the position and direction of the weld, and serves as the carrier for all additional information:
The horizontal solid line (or dashed line, used for non-metallic welding) is divided into the arrow side (the end close to the arrow) and the other side (the end far from the arrow). When the welds are distributed on both sides of the arrow, the symbol should be marked on both sides of the reference line; if only one side is welded, the symbol is located on the side of the reference line close to the arrow.
Special case: When the component is very thin and it is impossible to mark the side information of the arrow, the arrow tail can be omitted (as shown in the illustration, "The arrow tail can be omitted when there is no additional information"). However, the baseline must be complete.
Point to the location of the weld seam. The direction of the arrow should be perpendicular or inclined to the surface of the weld piece (in line with the projection relationship), and the relative position of the arrow to the edge of the weld piece should clearly reflect the actual welding area (for example, the arrow of the "circumferential weld symbol" points to the circumferential weld).
Please note: If the arrow and its tail are swapped, the meaning of the symbol may change (such as the difference between single-sided welding and double-sided welding). When marking, it is necessary to strictly follow the process requirements.
Letters and numbers above or below the baseline (depending on the position of the symbols) are used to quantify the geometric parameters and processing techniques of the weld seam. The core elements include:
Indicates the thickness or width of the weld, commonly seen in butt welds, fillet welds, etc. For example, the weld leg size (K value) of the fillet weld needs to be marked next to the weld contour symbol (F) (as shown in "Welding Dimension or Strength S" in the illustration).
Rule: If the dimensions on both sides of the weld are the same, only need to mark on one side of the reference line; if they are asymmetrical, they need to be marked on both sides respectively (for example, "3/4" indicates 3mm on one side and 4mm on the other side).
Bevel angle (R): The angle formed between the bevel surfaces (as shown in "Bevel Angle and Plug Welding Groove", referring to V-shaped, U-shaped, and J-shaped bevels), commonly seen in V-shaped, U-shaped, and J-shaped bevels, affects the welding penetration and the amount of filler metal used.
Bevel depth (D): The vertical distance from the bevel surface to the base material surface (as shown in "welding depth within the bevel"), used to control the degree of root fusion.
Groove gap (A): The reserved space between the two welded components during assembly (as shown in "Groove gap, and the filling depth for plug welding or slot welding"), ensuring that the welding rod or wire can extend into the molten pool.
Filler depth: In spot welding or slot welding, the depth to which the filler metal is deposited in the hole or slot. This should be marked in conjunction with the gap parameters (for example, "A = 2mm, filler depth ≥ 1.5mm").
Representing the cross-sectional shape of the weld with a specific graphic is a core identifying element of welding symbols (shown in the center position of the figure). For example:
Tungsten Inert Gas (TIG) welding seam: Straight line or symmetrical zigzag line;
Corner weld: Right-angled triangle (indicating convex corner welding) or concave corner welding symbol;
Spot welding / slot welding: Rectangular or trapezoidal shape.
Different industries (such as pressure vessels and steel structures) may have detailed regulations for contour symbols, and these should be used in conjunction with specific standards.
Marked on the left or right side of the baseline (as shown in "Welding Specifications/Welding Method, or Other Information"), the content includes:
Welding method code (such as GMAW - Fusion Welding with Gas Shielding, GTAW - Tungsten Electrode Gas Shielded Welding);
Welding current, voltage, welding speed (such as I = 180A, U = 22V, v = 50cm/min);
Welding position (such as PA - flat welding, PB - horizontal welding, PC - vertical welding, PD - overhead welding);
Welding materials (such as E4315 welding rods, ER70S-6 welding wire).
For the welding requirements of complex structures, the standard has defined several specific symbols, which need to be accurately labeled according to the specific context:
Above the arrow line or the reference line, draw a circle (⚪) to indicate that this weld needs to be completed at the construction site (rather than being prefabricated in the factory). This is commonly seen in the assembly of large components in sections (such as bridges, storage tanks) (refer to the "on-site welding symbol" in the illustration).
Note: The on-site welding symbols cannot be used alone; they must be combined with the basic weld symbols (for example, ⚪ + F represents on-site fillet weld).
The arrow lines encircle the circumference of the weldment, and are accompanied by specific symbols to indicate annular welds (such as pipe butt welds, flange sealing welds) (refer to the "circumferential weld symbol" in the illustration).
When marking, it is necessary to indicate the weld length (L) or the weld pitch (P). For example, "L = 300mm" indicates that each weld segment is 300mm long.
When performing multi-layer welding, the number of layers should be indicated after the weld size (for example, "3×3mm" indicates a 3-layer weld, with each layer being 3mm).
Special welding methods such as spot welding, seam welding, and stud welding require the number of welds to be marked near the baseline (as shown by "(N)"). For example, "(5)" indicates 5 spot welds.
If the welds are symmetrically distributed on both sides of the arrow, only the dimensions need to be marked on one side (for example, for double-sided fillet welds, only the weld leg dimension on one side needs to be marked). This avoids duplication.
When symbols are superimposed, they should be arranged in the following order: "Welding method → Specification parameters → Weld seam outline → Dimensions → Groove parameters". This ensures a clear hierarchy of information (such as "GTAW-180A ⚪F-K6-A3").
Distinguishing between the presence and absence of the baseline
The solid line reference line is used to mark the front welds of the weldment, while the dashed line reference line is used for the back or invisible welds. They must be strictly aligned with the direction of the component view.
All values are in millimeters (mm) by default and no additional units need to be specified; angle units are in degrees (°), and it is necessary to clearly indicate (e.g. "R = 60°").
Take "bilateral对接 weld seam + on-site installation" as an example
1. Baseline level, with the arrow pointing towards the left weld piece;
2. On both sides of the baseline, mark the symmetrical weld size as "S = 8mm";
3. The above indicates the groove angle "R = 60°" and the groove depth "D = 5mm".
4. Add a circle beside the arrow line to indicate "On-site Welding". On the left side, mark the welding method as "GMAW" and the current as "160A".
This symbol fully conveys the core information of "on-site installation, bilateral full penetration butt welding, specific groove parameters and welding process", avoiding any misunderstandings during construction.
Conclusion
Welding symbols serve as the "universal language" for cross-disciplinary technical communication, and their standardization directly affects welding efficiency and quality. To master the core rules of GB/T10044-2006, one needs to repeatedly compare the annotated examples based on engineering practice, and focus on understanding the logical relationships among the reference lines, arrows, and dimension parameters. For complex structures, it is recommended to use 3D models to assist in the annotation, ensuring that the symbols are perfectly matched with the physical positions. Correct use of welding symbols is not only a basic requirement for technical documents but also an important manifestation of modern manufacturing's standardization and refinement.
