What Kind of Fillet Weld Is Qualified?

The weldability of base metal, matching of welding materials and base metal, welding efficiency, welding method, weld bead size, welding deformation, buckling of joint plate and other factors shall be considered in welding design.

Related reading: The Ultimate Guide to Welding

Take fillet weld bead as an example.

According to the regulations of American Welding Society Steel Structure Welding Code (AWSD1.1), fillet weld beads are divided into three categories, including ideal weld bead, acceptable weld bead width and unacceptable weld bead.

Incorrect weld bead dimensions include insufficient throat depth of fillet weld bead, too long convex surface, welding corrosion, overlap, insufficient leg length and poor fusion.

The minimum size of the fillet weld bead is also specified in the American Welding Association Steel Structure Welding Regulations and China’s Technical Code for Design of Steel Structures of Steel Buildings, as shown in Table 4.

What Kind of Fillet Weld Is Qualified? 1
What Kind of Fillet Weld Is Qualified? 2
What Kind of Fillet Weld Is Qualified? 3

The minimum leg length of fillet welding is determined by the thicker plate of the two parts of the joint, but shall not be greater than the thickness of the thinner plate.

In case of excess, sufficient preheating shall be provided to ensure the welding quality.

Related reading: Welding Quality of Welded Joints

If required by stress calculation, the welding size can be greater than the thickness of the thin plate of the joint.

Table 3 provides the minimum leg length of fillet welding for various plate thicknesses, and Table 4 shows the relationship between the full pass width of fillet welding and the maximum convex face length.

Table 3 Minimum angle length of fillet weld bead

Thickness of thicker plate at joint, t (mm)Minimum leg length of fillet weld (mm)
t≤63
6<t≤125
12<t≤196
19<t≤388

Table 4 Relation between the full pass width and the maximum convex length of fillet welding

Full weld bead width, wMaximum convex face length, c
w≤8mm1.6mm
8mm<w≤25mm3mm
25mm<w5mm

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