13th International Conference on Fracture June 16–21, 2013, Beijing, China 2 high-strength and thickness steel with the FAD method are summarized as follow: 1) Measure the CTOD values of the welding joints of the high-strength steel at a specific temperature; 2) Plot the stress-strain curve of the welding joints of the high-strength steel through an uniaxial tensile test, and then transfer it to a true stress-strain curve with related equations; 3) Plot the Level 2B FAD with the true stress-strain curve, make the failure assessments of the joint and the welding seam center of the high-strength steel plates; 4) Calculate the load ratio and fracture ratio (coordinates of the assessment points) with the CTOD values and stress-strain curve, and then plot the FADs with the ratios. The toughness assessments of the welding joint would be completed with the FADs. 2 CTOD experiment and results The present paper mainly research on the FADs of the welding seam center of butt-weld joint between EQ70 and EQ56 high-strength steel plates(Level-AB) with 38 mm thickness. The CTOD test is carried out according toBS7448[5] and Offshore Standard DNV-OS-C401[6]The chemical composition of the EQ70 and EQ56 steel plates are shown in the table 1 and table 2, while the different welding technologies are shown in table 3. The EQ 56 and EQ 70 were butt welded with equiangular welding groove (45°K style groove), by multi-layer and multi-pass manual arc welding. While it should preheat temperature to70 , ℃ kept the groove straight edge perpendicular to the specimen plane, with 210 to 230 thermal insulation ℃ per hour after welding. To the specimen of EQ56/70, the K type groove straight edge should perpendicular to the side of EQ70[7]. Three-point bending specimens, with single side fatigue precrack, were applied in the CTOD test and processed into 26 mm thickness(B) and 52 mm width(W). The results and effectiveness of the CTOD test were list in the table 4. Table 1 The chemical compositions of EQ 70 specimen with 38 mm thickness (%) C Si Mn P S Cu Ni Cr Mo 0.14 0.08 0.86 0.011 0.002 0.26 0.49 0.76 0.32 V ZR Ti Nb Sol Al N B Ceq PCM 0.04 0.005 0.013 0.016 0.064 0.0023 0.0010 0.56 — Table 2 The chemical compositions of EQ56 specimen with 38 mm thickness (%) C Si Mn P S Al Ni 0.05 0.41 1.51 0.009 0.001 0.033 0,73 Cr Cu Nb V Ti Mo w(C)eq 0.33 0.71 0.04 0.04 0.009 0.22 0.51 Table 3 Welding technologies of the joints of EQ70/56 Technical parameter Type No.of welding bead Diameter (mm) Electricity (A) Voltage (V) Welding speed (mm/min) Maximum Energy Input (kJ/mm) Average Energy Input (kJ/mm) 1 3.2 130~160 20~25 69 3.62 2.85 A others 4.0 170~195 22~27 77 4.10 3.51
RkJQdWJsaXNoZXIy MjM0NDE=