PSI - Issue 2_A

Junjing He et al. / Procedia Structural Integrity 2 (2016) 871–878 Junjing He / Structural Integrity Procedia 00 (2016) 000 – 000

873 3

Fig. 1. Drawings for specimen with length 240 mm and thickness 5 mm

2.3. Creep test

The creep tests were conducted at the Institute of Materials Science and Welding, Graz University of Technology. For the creep tests both type of tubes as described above were used, the tubes were marked as:  Tube condition ECS (Extruded cold drawn and solution annealed)  Tube condition EQ (Extruded and quenched immediately after extrusion) The dimension of the ECS tube had 54 mm outer diameter and was 7 mm in thickness. The dimension of the EQ tube was 60 mm in outer diameter and 8 mm in thickness. Creep samples were manufactured out of the tubes and prepared according the DIN50125 and the location of the creep samples can be seen in Fig. 2. One half of the tubes was used to investigate the tubes in as-received condition and the other half was used for creep samples preparation. In total six creep samples were manufactured from each tube. For each tube type (ECS, EQ) three stresses were chosen, as listed in Table 2.

Fig. 2. Location and marking of creep samples

3. Test results

3.1. Creep rupture

The test results of the creep test are listed in Table 2. The reduction of area is calculated by the help of the initial diameter and diameter after rupture. In some cases the diameter could not be measured after rupture. For the creep rupture strength, no significant differences between the EQ and ECS samples can be observed. The material showed a low reduction in area at rupture, in the range of 4-19%. ECCC (2005) has proposed a master equation to predict the creep rupture time for different types of austenitic stainless steels. For HR3C, the master equation can be expressed as:   2 3 4 RP 0 1 0 2 0 3 0 4 0 4 exp / T t                 (1)