COMPUTATIONAL WELDING MECHANICS

Structure and Materials

The pipe was 508 mm (20 in.) diameter and 7.9 mm (0.312 in.) wall API 5LX-65 ERW.

Table 6-1: Composition of HSLA steel

С Ni Si V Mo 0.12 0.11 0.16 0.001 0.001

W Mn Cr Си P Al 0.001 0.91 0.01 0.001 0.002 0.04

Table 6-2: Pipe material properties, from [8]

Designation

API-SLX65

Yield Strength

71.3 ksi (483 MPa)

Tensile Strength

89.8 ksi (621 MPa)

Elongation %

29.4

Deposition of Welds

The welding consumables were Type E7018 low hydrogen shielded metal arc electrodes. At the test weld location a flat grove was machined into the pipe and a single weld pass was deposited along the centerline of the machined area. The weld was made with an internal pressure of 6.2 MPa.

All welds were made at an internal pressure of 900 psig (6.2 MPa). Tables 6-2 and 6-3 which are taken from [8] specify the data
for each weld. The electrode size was 2.38 mm, heat input was 0.79 KJ/mm and travel speed was 2.1 mm/s.

Figure 6-5 shows a composite mesh for a weld on a pressure vessel.

Figure 6-5: The various parts of the FEM mesh are shown. The smallest part, WP1, at the top of the figure, contains the weld pool.

In [8] welds A, B, D, G, //and I were rated as "safe" welds; C, J and L were rated as marginal and weld E and F were rated as bum through. We only consider one weld from each class, i. e., welds H, J and E. For these three welds, the welding current was 80 amps, the voltage 21 volts and the electrode size 3/32 in.

Table 6-3: Summery of Weld Data

Test

ID

Wall

Thickness

(in.)

Heat

Input

(KJ/in.)

Travel

Speed

(in./min)

H

0.156

20

5.0

J

0.156

25

4.0

E

0.125

20

5.0

FEM Mesh

The mesh for the pressure vessel, called PV1, had 3006 tf-node brick elements. For each weld, a fine mesh with 3456 elements, called MP1, was created for the region around the machined slot. Outside of MP1, a transition mesh with 768 elements, called TM2, and coarser transition mesh called TM1 with 140 elements was made. Inside MP1 an even finer mesh was created, called WP1, with 3840 elements.

Figure 6-6 shows the moving mesh near the weld pool region with the weld. Also filler metal is being added as the weld moves. The mesh WP1 was also moved with the arc during the welding process.

Figure 6-6: The mesh moves with the arc and filler metal being added during the welding process is shown.

COMPUTATIONAL WELDING MECHANICS

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