“1 .Welding Standards: Achieve Excellence with IS Code Guidelines”

Introduction Welding standards

Welding standards is a fundamental process in the construction and manufacturing industries, creating strong and durable joints in metal structures. Ensuring the quality and reliability of welds is crucial for the safety and longevity of these structures. In India, the Indian Standards (IS) codes provide detailed guidelines and best practices for various welding techniques. These standards help welders produce high-quality work that meets safety and performance requirements. In this article, we will explore welding standards from the IS code that every welder should know to achieve success in their projects. By understanding and following these standards, you can ensure your welds are strong, reliable, and compliant with industry regulations.

Indian Standards (IS) Codes for Welding and Welding standards:

IS 816 –

Code of practice for use of metal arc welding for general construction in mild steel

IS 819 –

Code of practice for resistance spot welding for light assemblies in mild steel

IS 1323 –

Code of practice for oxy-acetylene welding for structural work in mild steel

IS 4353 –

Recommendations for submerged arc welding of mild steel and low alloy steels

IS 9595 –

Recommendations for metal arc welding of carbon and carbon manganese steels

IS 12834 –

Code of practice for oxy-acetylene welding for structural work in steel

IS 13920 –

Ductile detailing of reinforced concrete structures subjected to seismic forces – Guidelines (includes welding guidelines in seismic zones)

American Welding Society (AWS) Codes:

1. AWS D1.1/D1.1M – Structural Welding Code – Steel
2. AWS D1.2/D1.2M – Structural Welding Code – Aluminum
3. AWS D1.3/D1.3M – Structural Welding Code – Sheet Steel
4. AWS D1.4/D1.4M – Structural Welding Code – Reinforcing Steel
5. AWS D1.5/D1.5M – Bridge Welding Code
6. AWS D1.6/D1.6M – Structural Welding Code – Stainless Steel
7. AWS D1.8/D1.8M – Structural Welding Code – Seismic Supplement
8. AWS D9.1/D9.1M – Sheet Metal Welding Code
9. AWS A2.4 – Standard Symbols for Welding, Brazing, and Nondestructive Examination
10. AWS A3.0M/A3.0 – Standard Welding Terms and Definitions
11. AWS A5.1/A5.1M – Specification for Carbon Steel Electrodes for Shielded Metal Arc Welding
12. AWS A5.18/A5.18M – Specification for Carbon Steel Electrodes and Rods for Gas Shielded Arc Welding

In this article, we will delve into the welding standards specified by IS codes in India, focusing particularly on IS 800:2007, which outlines guidelines for general construction in steel. Understanding and implementing these standards are essential for ensuring the structural integrity and safety of welded components in diverse engineering applications.

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Welding standards

IS 800:2007

is.800.2007

10.5 Welds and Welding

10.5.1 General Requirements (Clause 10.5.1)

According to IS 800:2007, the requirements for welds and welding must adhere to specific standards outlined in IS 816 and IS 9595, as applicable. These standards define the procedures and criteria for welding processes, ensuring that welds meet high-quality standards for strength and durability.

10.5.1.1 End Returns (Clause 10.5.1.1)

IS 800:2007 specifies that fillet welds ending at the edges or sides of parts should be continuously returned around corners for a distance not less than twice the size of the weld. This practice is essential, especially on the tension side of parts subjected to bending loads, to enhance weld strength and prevent stress concentrations.

Clause 10.5.1.2: Lap Joint Requirements

According to IS Code, Clause 10.5.1.2 mandates specific requirements for lap joints:

• The minimum overlap length should be at least four times the thickness of the thinner part being joined or 40 mm, whichever is greater.
• Single end fillet welds can only be used when the parts being overlapped are securely prevented from opening.
• If an element’s end is connected only by parallel longitudinal fillet welds, each weld along the edge should be as long as the distance between these welds across the joint.

Welding standards

Clause 10.5.1.3: Single Fillet Weld Restrictions

Clause 10.5.1.3 of the IS Code stipulates:

• A single fillet weld should not experience twisting forces along its length.

10.5.2 Size of Weld

Clause 10.5.2.1 Minimum Size of Normal Fillets

Regular fillet welds must be at least as large as the smallest leg size. For welds with deep penetration, where the penetration depth extends at least 2.4 mm beyond the root run, the fillet size should equal the minimum leg size plus an additional 2.4 mm.

Clause 10.5.2.2 Fillet Welds by Semi-Automatic or Automatic Processes

For fillet welds made using semi-automatic or automatic methods, where the penetration depth significantly exceeds 2.4 mm, the size should be determined based on the actual penetration depth, agreed upon by the purchaser and the contractor.

Welding standards

Clause 10.5.2.3 Minimum Size Requirement for Fillet Welds

Fillet welds must not be smaller than 3 mm in size. The initial run or a single run fillet weld should adhere to the sizes specified in Table 21 to prevent cracking when preheating is not applied.

Table 21 Minimum Size of First Rtm or of a Single Run Fillet Weld

SI No.	Thickness of Thicker Part (mm)	Minimum Size of Fillet Weld (mm)
i)	– 10	3
ii)	10 – 20	5
iii)	20 – 32	6
iv)	32 – 50	8 (of first run), 10 (for minimum size of weld)

NOTES: Welding standards

1. When the minimum size of the fillet weld given in the table is greater than the thickness of the thinner part, the minimum size of the weld should be equal to the thickness of the thinner part. The thicker part shall be adequately preheated to prevent cracking of the weld.
2. Where the thicker part is more than 50 mm thick, special precautions like pre-heating should be taken.

Clause 10.5.2.4 Size Specification for Butt Welds

The size of butt welds should be defined by the effective throat thickness.

Welding standards

Clause 10.5.3

(Clause 10.5.3.1) Effective Throat Thickness

In welding standards, the effective throat thickness for a fillet weld must be at least 3 mm. Usually, it shouldn’t be more than 0.7 times the thickness of the thinner plate being welded. But in specific cases, it can be as much as equal to the thickness of the thinner plate.

Welding standards

Understanding It

The effective throat thickness is critical in welding. For Example, if you’re welding two plates of different thicknesses together, the throat thickness of the fillet weld should be at least 3 mm. If one plate is thinner than the other, the throat thickness shouldn’t exceed 70% of the thinner plate’s thickness, unless there are special conditions allowing it to match the thinner plate’s thickness entirely.

Effective Length or Area of Weld

Clause 10.5.3.2: Calculation of Stress in Fillet Welds

For calculating stress in fillet welds where the joining faces are inclined, the effective throat thickness should be K times the fillet size. The value of K depends on the angle between the fusion faces, as specified in Table 22.

Table 22: Values of K for Different Angles Between Fusion Faces

(Clause 10.5.3.2)

Angle Between Fusion Faces	60°–90°	91°–100°	101°–106°	107°–113°	114°–120°
Constant, K	0.70	0.65	0.60	0.55	0.50

Clause 10.5.3.3: Effective Throat Thickness of Butt Welds

• For complete penetration butt welds, the effective throat thickness is equal to the thickness of the thinner part being joined.
• For incomplete penetration butt welds, the effective throat thickness is equal to the minimum thickness of the weld metal common to both parts, excluding any reinforcements.

Welding standards

Welding standards

(Clause 10.5.4) Effective Length or Area of Weld

(Clause 10.5.4.1) Fillet Welds

The effective length of a fillet weld is considered only where it matches the specified size and required throat thickness. Typically, the actual weld length equals the effective length shown on the drawing plus twice the weld size, but never less than four times the size of the weld.

Example: If a drawing specifies a fillet weld of 10 mm, the effective length considered will be the length specified on the drawing plus 20 mm, ensuring it is at least 40 mm in total.

(Clause 10.5.4.2) Butt Welds

For butt welds, the effective length is determined by the continuous full-size weld length, which must not be less than four times the size of the weld.

Example: A butt weld of 8 mm size should have an effective length equal to or greater than 32 mm to meet the standard requirements.

Welding standards

Clause 10.5.4.3 Effective Area of Plug Welds

The effective area of a plug weld is based on the size of the hole in the surface where the weld connects. These welds are not meant to bear loads.

Example: Imagine a metal plate with holes. A plug weld joins another plate through these holes, securing them together without carrying any significant weight.

Clause 10.5.4.4 Side Weld Length Limitation

If the length of a side weld transferring shear exceeds 150 times its throat size (tt), its strength should be adjusted according to long joint considerations (refer to 10.5.7.3). However, this limitation does not apply to welds joining a flange to a web where the welds support the entire length.

Example: In a steel beam, side welds connect the flange and web. If these welds are long enough relative to their size, their strength must be adjusted accordingly to ensure structural integrity.

Welding standards

(Clause 10.5.5) Intermittent Fillet Welding Requirements

Clause 10.5.5.1: Effective Length Requirement

Unless stated otherwise, intermittent fillet welding must be at least four times the size of the weld, with a minimum length of 40 mm.

Example: If you’re welding a joint with a 6 mm weld size, the effective length should be at least 24 mm, but not less than 40 mm regardless of the weld size.

Clause 10.5.5.2: Spacing Between Welds

The clear spacing between intermittent fillet welds’ effective lengths should be between 12 to 16 times the thickness of the thinner plate being joined. For compression and tension joints, respectively. Additionally, the spacing should never exceed 200 mm in any case.

Example: If you’re welding two plates, one 10 mm thick and the other 8 mm thick, the spacing between intermittent welds should be between 120 mm and 160 mm for compression joints and between 128 mm and 160 mm for tension joints.

Welding standards

Clause 10.5.5.3: Intermittent Butt Weld Requirements

Requirement for Intermittent Butt Welds

Unless stated otherwise, intermittent butt welds must be at least four times the size of the weld in effective length. The distance between the effective lengths of welds should not exceed 16 times the thickness of the thinner part being joined. These welds should not be used in positions exposed to dynamic, repetitive, or alternating stresses.

Explanation with Example:

For instance, if you have a weld size of 5 mm, the effective length between welds should be at least 20 mm (4 times 5 mm). If the thinner part being welded is 1 mm thick, the distance between welds should not exceed 16 mm (16 times 1 mm).

Welding standards

Clause 10.5.6: Types and Quality of Welds

Types and Quality of Welds

According to this code, welds can be fillet, butt, slot, plug, or compound welds. Welding electrodes must meet IS 814 standards.

Welding standards

(Clause 10.5.7) Design Stresses in Welds

(Clause 10.5.7.1) Shop Welds

(Clause 10.5.7.1.1)Fillet Welds

When designing a fillet weld, the strength, denoted as fwd, is determined by its throat area. This strength is calculated using the formula:

fwd=fwn/ymw

Clause 10.5.7.1.2 Butt Welds

Definition and Treatment:

Butt welds are considered the same as the base metal (the metal parts being joined). The thickness of the butt weld is measured as the throat thickness.

Stress Limit:

The stress on the butt weld should not be more than the stress allowed on the base metal.

Example:

If you have two steel plates welded together with a butt weld, the weld should be as strong as the plates themselves. The thickness of the weld is measured where the two plates meet (the throat). If the plates can handle a certain amount of stress, the weld should not exceed this stress limit.

This ensures that the welded joint is just as strong as the rest of the metal structure.

Welding standards

Clause 10.5.7.1.3 Slot or Plug Welds

The design shear stress for slot or plug welds should follow the guidelines stated in 10.5.7.1.1.

Example: For instance, if you’re using a slot weld in a steel connection, make sure the stress calculations align with 10.5.7.1.1.

Clause 10.5.7.2 Site Welds

The design strength for site welds, which are made during the erection of structural members, should be calculated as per 10.5.7.1. However, a partial safety factor (γ_w) of 1.5 must be applied.

Example: When welding steel beams on-site for a construction project, you must use the partial safety factor of 1.5 in your calculations to ensure safety and compliance.

Welding standards

Clause 10.5.7.3 Long Joints

If the length of the welded joint (l_j) of a splice or end connection in a compression or tension element exceeds 150 times the thickness (t), the design capacity of the weld (as specified in 10.5.7.1.1), f_wd, should be reduced by a certain factor.

Example: Imagine you’re connecting two steel columns with a welded splice, and the joint length is more than 150 times the thickness of the material. In this case, you must reduce the design capacity of the weld according to the specified factor.

Welding standards

(Clause 10.5.8) Fillet Weld Applied to the Edge of a Plate or Section

(Clause 10.5.8.1) Weld Size for Square Edges

When a fillet weld is used on the square edge of a part, the weld size should generally be at least 1.5 mm smaller than the edge thickness to prevent washing down of the exposed edge (see Fig. 17A).

Example: If a plate has an edge thickness of 10 mm, the fillet weld size should be 8.5 mm.

Welding standards

(Clause 10.5.8.2) Weld Size for Rounded Edges

When applying a fillet weld to the rounded toe of a rolled section, the weld size should generally not be more than three-quarters of the section’s thickness at the toe (see Fig. 17B).

Example: If the thickness at the toe of a rolled section is 12 mm, the fillet weld size should be a maximum of 9 mm.

Welding standards

(Clause 10.5.8.3) Avoiding Excess Melting

If the specified size of a fillet weld is such that the parent metal does not project beyond the weld, ensure that no excessive melting of the outer cover occurs that would reduce the throat thickness (see Fig. 18).

Example: Ensure proper welding technique to avoid reducing the effective throat thickness when the parent metal is flush with the weld.

Welding standards

(Clause 10.5.8.4) Full-Size Fillet Welds for Dynamic Loads

For fillet welds on the edges of plates or sections subjected to dynamic loading, the fillet weld must be full-size with leg length equal to the thickness of the plate or section, adhering to the limitations in Clause 10.5.8.3.

Example: For a dynamically loaded plate with a thickness of 8 mm, the fillet weld should have a leg length of 8 mm.

Welding standards

(Clause 10.5.8.5)End Fillet Welds

End fillet welds, perpendicular to the force direction, should be of unequal size with a throat thickness not less than half the part’s thickness (0.5t), as shown in Fig. 19. The difference in weld thickness should be adjusted at a uniform slope.

Example: For a part with a thickness of 10 mm, the end fillet weld should have a minimum throat thickness of 5 mm.

Welding standards

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