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Research Papers: Materials and Fabrication

Optimization of a Weld Overlay on a Plate Structure

[+] Author and Article Information
John Goldak

Carleton University, Ottawa, ON K1S 5B6, Canadajgoldak@mrco2.carleton.ca

Carleton University, Ottawa, ON K1S 5B6, Canada

Jianguo Zhou, Stanislav Tchernov, Dan Downey

Goldak Technologies Incorporated, Ottawa, ON K1V 7C2, Canada

J. Pressure Vessel Technol 132(1), 011402 (Dec 09, 2009) (9 pages) doi:10.1115/1.4000511 History: Received January 29, 2009; Revised September 22, 2009; Published December 09, 2009; Online December 09, 2009

Abstract

An overlay weld repair procedure on a $1066.8×1066.8 mm2$ square plate 25.4 mm thick was simulated to compute the 3D transient temperature, microstructure, strain, stress, and displacement of the overlay weld repair procedure. The application for the overlay was the repair of cavitation erosion damage on a large Francis turbine used in a hydroelectric project. The overlay weld consisted of a $4×6$ pattern of $100×100 mm2$ squares. Each square was covered by 15 weld passes. Each weld pass was 100 mm long. The total length of weld in the six squares was 36 m. The welds in each square were oriented either front-to-back or left-to-right. The welding process was shielded metal arc. The analysis shows that alternating the welding direction in each square produces the least distortion. A delay time of 950 s between the end of one weld pass and the start of the next weld pass was imposed to meet the requirement of a maximum interpass temperature to $50°C$.

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Figures

Figure 1

The geometry of the overlay weld repair simulation described in Ref. 1 is shown

Figure 2

This cross section of the block for one overlay 100 mm square shows the FEM mesh for the filler metal

Figure 3

The FEM mesh of several blocks of overlay 100 mm square are shown embedded the structure being repaired

Figure 4

The FEM mesh of 6×4 checker board pattern of blocks of 100 mm overlay squares are shown together with stiffening gussets of the structure being repaired

Figure 5

The temperature in K at a virtual thermocouple located at the centroid of the bottom of the plate is plotted versus time. Each peak is associated with one weld pass in one block.

Figure 6

The decay of the maximum temperature in the structure between two weld passes is shown as a function of time for a maximum interpass temperature of 50°C. The delay time for any higher maximum interpass temperature can be read from the graph.

Figure 7

The phase fraction of martensite is shown for the front-to-back overlay

Figure 8

The phase fraction of ferrite is shown for the front-to-back overlay

Figure 9

The hardness is shown for the front-to-back overlay. The blue denoting zero hardness is because the algorithm only computes hardness if the material point transformed to austenite.

Figure 10

The εzz strain as a function of time for strain gauge at the center of the bottom surface

Figure 11

The εzz strain as a function of time for strain gauge at the center of the bottom surface for longer time

Figure 12

Left-to-right distortion magnified ten times at 1,000,000 s

Figure 13

Front-to-back distortion magnified ten times at 1,000,000 s

Figure 14

Checker board distortion magnified ten times at 1,000,000 s

Figure 15

Difference of left-to-right distortion to checker board distortion magnified ten times at 1,000,000 s

Figure 16

Difference of front-to-back distortion to checker board distortion magnified ten times at 1,000,000 s

Figure 17

Difference of left-to-right distortion to front-to-back distortion magnified ten times at 1,000,000 s

Figure 18

The temperature at the point at which a thermocouple is located is plotted versus time. This figure is from Ref. 12.

Figure 19

The εzz strain as a function of time for strain gauge 1 on the top surface of the 100×100 is shown. This figure is from Ref. 12.

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