TC 9-237 – Chapter 6 – Section II

Section II. NOMENCLATURE OF THE WELD

6-7. GENERAL

Common terms used to describe the various facets of the weld are explained in paragraphs 6-8 and 6-9 and are illustrated in figure 6-13.

nomenclature of welds

6-8. SECTIONS OF A WELD

a. Fusion Zone (Filler Penetration). The fusion zone is the area of base metal melted as determined in the cross section of a weld.

b. Leg of a Fillet Weld. The leg of a fillet weld is the distance from the root of the joint to the toe of the fillet weld. There are two legs in a fillet weld.

c. Root of the Weld. This is the point at which the bottom of the weld intersects the base metal surface, as shown in the cross section of weld.

d. Size of the Weld.

(1) Equal leg-length fillet welds. The size of the weld is designated by leg-length of the largest isosceles right triangle that can be scribed within the fillet weld cross section.

(2) Unequal leg-length fillet welds. The size of the weld is designated by the leg-length of the largest right triangle that can be inscribed within the fillet weld cross section.

(3) Groove weld. The size of the weld is the depth of chamfering plus the root penetration when specified.

e. Throat of a Fillet Weld.

(1) Theoretical throat. This is the perpendicular distance of the weld and the hypotenuse of the largest right triangle that can be inscribed within the fillet weld cross section.

(2) Actual throat. This is distance from the root of a fillet weld to the center of its face.

f. Face of the Weld. This is exposed surface of the weld, made by an arc or gas welding process on the side from which the welding was done.

g. Toe of the Weld. This is the junction between the face of the weld and the base metal.

h. Reinforcement of the Weld. This is the weld metal on the face of a groove weld in excess of the metal necessary for the specified weld size.

6-9. MULTIPASS WELDS

heat affected zones in multipass weld
welding procedure schedule - various welds
welding procedure schedule - various welds
welding procedure schedule - various welds

a. The nomenclature of the weld, the zones affected by the welding heat when a butt weld is made by more than one pass or layer, and the nomenclature applying to the grooves used in butt welding are shown in figure 6-14. Figure 6-15 is based on weld type and position.

b. The primary heat zone is the area fused or affected by heat in the first pass or application of weld metal. The secondary heat zone is the area affected in the second pass and overlaps the primary heat zone. The portion of base metal that hardens or changes its properties as a result of the welding heat in the primary zone is partly annealed or softened by the welding heat in the secondary zone. The weld metal in the first layer is also refined in structure by the welding heat of the second layer. The two heating conditions are important in determining the order or sequence in depositing weld metal in a particular joint design.

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