PSI - Issue 20

Ekaterina M. Maksimova / Procedia Structural Integrity 20 (2019) 174–179 Ekaterina M. Maksimova / Structural Integrity Procedia 00 (2019) 000–000

176

3

Table 2. Chemical composition (wt., %) and mechanical properties of welding electrodes

Elongation (%)

Tensile strength (MPa)

Impact strength (V-notch) (J/cm 2 )

Electrode

С

Si

Mn

Ni

Mo

S

P

UONI 13/ Moroz LB-52TRU

0,075

0,3

0,7 0,9

2,8

- -

0,010 0,017

0,017 0,020

210

660 540

22,0

0,09

0,42

-

≥ 49 at -30° С

29

Table 3. Welding parameters Marking of welded samples (No) Ambient temperature (° С )

Current I ( А ) Voltage U (V)

Current type

Heat input (kJ/m)

Pass and electrode diameter (mm)

Electrode

1) 973 2) 1681 3) 1698 1) 804 2) 1489 3) 1796 1) 660 2) 2028 3) 1597 1) 682 2) 1514 3) 1729

1) root – 3 2) filler – 4 3) face – 4 1) root – 3 2) filler – 4 3) face – 4 1) root – 3 2) filler – 4 3) face – 4 1) root – 3 2) filler – 4 3) face – 4

1) I=98, U=23,6 2) I=154, U=24,4 3) I=154, U=24,4 1) I=98, U=26,2 2) I=145, U=25,5 3) I=146, U=25,0 1) I=87, U=26,5 2) I=141, U=23,3 3) I=141, U=22,6 1) I=99, U=26,8 2) I=136, U=24,1 3) I=136, U=24,3

UONI 13/ Moroz

3

-45

DC

UONI 13/ Moroz

7

+20

DC

6

-45

LB-52TRU

DC

8

+20

LB-52TRU

DC

The HAZ structures were investigated by a high resolution scanning electron microscope with a Schottky cathode JEOL JSM-7800F. To analyze the structure, the metallographic specimens were taken in the cross-section of the welded joints. After grinding and polishing, chemical etching of the surface with a 4% alcohol solution of nitric acid was used. Research results and discussion The base metal microstructure is a ferritic-pearlite mixture with a ratio of the volume fraction of structural components in the amount of 90/10 (ferrite / perlite) (Fig. 2). The average grain diameter of ferrite is about 6 microns. The base metal has a uniform polygonal structure.

Fig. 2. The base metal microstructure.

Figures 3, 4 show the HAZ microstructure of the filling passes of welded joints made by manual arc welding using the UONI 13/Moroz electrode.