PSI - Issue 5

Lars Sieber et al. / Procedia Structural Integrity 5 (2017) 1011–1018 Sieber et al. / Structural Integrity Procedia 00 (2017) 000 – 000

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Table 1. Chemical composition of the material samples

Content of tramp elements [%] (variation in case of segregation at I-sections)

Sample

C

Si

Mn

P

S

Al

N 2

MV

0.07 0.08

0.008 0.008 0.002 0.004 0.001 0.006

0.51 0.44

0.069 0.074

0.103 0.032

0.002 0.004 0.001 0.003 0.001 0.002

0.0170 0.0175 0.0250 0.0210 0.0200 0.0140

GDD HDD

0.07 – 0.12

0.63 – 0.85

0.06 – 0.12

0.07 – 0.14

AV

0.07

0.42

0.057

0.084

0.04 – 0.07 0.04 – 0.06

0.43 – 0.60 0.46 – 0.51

0.05 – 0.15 0.04 – 0.09

0.03 – 0.12 0.01 – 0.02

TFT TFS

Table 2. Maximum content of tramp elements according to old delivery standards for weldable structural steel

Maximum content of tramp elements [%]

Standard

Steel

C

Mn

P

S

N 2

Thomas steel

0.19 0.24

- -

0.126 0.098

0.084 0.084

- -

DIN 1612:1943

Siemens-Martin steel

DIN 17100:1957

Mild steel

0.25

-

0.075

0.063

0.0110

DIN EN 10025:1994

Rimmed steel

0.21

1.50

0.055

0.055

0.0090

3.2. Welding tests with current filler material

To evaluate the weldability of the selected mild steels, welding tests were carried out. Contrary to the investigations by Lüddecke (2006), butt welds were realized between plates of old mild steels and new structural steel S235. For the material samples of I-beams (HDD, TFT and TFS) the required plates were extracted of the web to consider the influence of segregation. Welding connections were made mainly on 2 opposite edges of the old steel plates to exploit the material samples. The manual metal arch welding of these butt welds was realized with basic coated stick electrodes of type E 42 2 B 42 H10 according to EN ISO 2560:2010. To minimize the seam volume as well as the angular distortion of the weld, the weld preparation was carried out as an X-shaped seam with an opening angle of 50° (see Figure 1a). The seam was multi-pass welded alternating with stringer beads in flat position (PA). This welding order (Figure 1b) resulted in a reduction of the residual stresses as well as into normalization of the lower welding beads. The use of thin stick electrodes with a diameter of 2.5 mm guaranteed a low fusion penetration. This resulted in a low concentration gradient of the harmful tramp element in the seam.

b

a

Fig. 1. (a) Joint preparation; (b) Welding sequence of the multi-pass welded joint