1. C.T.A.S. HIGH STRENGTH STEEL - YS 490 - 690 MPa Consumables optimisation for the welding of high strength steels Appendix 6 (p. 1/16)

2. C.T.A.S. Main menu: Over-matching approach Over-matching approach Welding process Welding process Chemical composition optimization of S690 type consumables Chemical composition optimization of S690 type consumables Impact of the lowering of diffusible hydrogen in high strength steels welding consumables Impact of the lowering of diffusible hydrogen in high strength steels welding consumables Appendix 6 (p. 2/16)

3. C.T.A.S. Overmatching : Over-matching approach in the weld metal selection is a general practice. Over-matching approach in the weld metal selection is a general practice. weld metal is required with strength higher than that of the parent metal to offset the potential problems such as a reduced toughness and presence of defects in the weld metal weld metal is required with strength higher than that of the parent metal to offset the potential problems such as a reduced toughness and presence of defects in the weld metal Appendix 6 (p. 3/16)

4. C.T.A.S. Overmatching : Actual or theoretical overmatching ?  Codes require a MIN YS value for the base material  The actual YS of the base material should be very close to the min. or much more than the min.  The weld metal YS, depending on the actual base material YS, could satisfy the over or the mis-matching requirement  As practical approach is usually required : min WM ys = min BM ys + 10%= MAX BM ys Actual or theoretical overmatching ?  Codes require a MIN YS value for the base material  The actual YS of the base material should be very close to the min. or much more than the min.  The weld metal YS, depending on the actual base material YS, could satisfy the over or the mis-matching requirement  As practical approach is usually required : min WM ys = min BM ys + 10%= MAX BM ys Appendix 6 (p. 4/16)

5. C.T.A.S. Overmatching : If the steel maker can accept this narrow range of YS (YS min + 10%) the YS WM and the YS BM could be of the same order of magnitude If the steel maker can accept this narrow range of YS (YS min + 10%) the YS WM and the YS BM could be of the same order of magnitude But if we want an actual OM and the steel maker does not accept YS min+10% we have to consider an higher WM YS min (+15,+20,+30%+40%) But if we want an actual OM and the steel maker does not accept YS min+10% we have to consider an higher WM YS min (+15,+20,+30%+40%) In this case for YS 690 the min. WM ys should be 793 - 828 - 897-966 MPa In this case for YS 690 the min. WM ys should be 793 - 828 - 897-966 MPa The highest YS (897 - 966MPa) induces impact properties reduction and it makes very difficult or impossible to meet all the requirements The highest YS (897 - 966MPa) induces impact properties reduction and it makes very difficult or impossible to meet all the requirements Appendix 6 (p. 5/16)

6. C.T.A.S. Overmatching : Welding consumables are an industrial product that means that an acceptable range for the chemical elements is required Welding consumables are an industrial product that means that an acceptable range for the chemical elements is required The Standards (EN - AWS-…) require an acceptable range of mechanical properties The Standards (EN - AWS-…) require an acceptable range of mechanical properties To compare the Codes requirements we can consider the following table To compare the Codes requirements we can consider the following table Appendix 6 (p. 6/16)

7. C.T.A.S. Overmatching : BM YS 500 500+10%= 550 MPa - min WM BM YS 500 500+10%= 550 MPa - min WM BM YS 690 690+10%= 759 MPa - min WM BM YS 690 690+10%= 759 MPa - min WM EN class YS TS E AWS class YS TS E EN class YS TS E AWS class YS TS E 55 550 610 18 90 540 620 17 55 550 610 18 90 540 620 17 62 620 690 18 100 600 690 16 62 620 690 18 100 600 690 16 69 690 770 17(+0%) 110 670 760 15 69 690 770 17(+0%) 110 670 760 15 (+7.5%) 120 740 830 14 (+7.5%) 120 740 830 14 79 790 880 16(+15%) 79 790 880 16(+15%) 89 890 980 15(+30%) 89 890 980 15(+30%) Appendix 6 (p. 7/16)

8. C.T.A.S. Overmatching : Impact and tensile properties requirement are the main concern for high productivity welding process (FCAW-SAW) because  Heat Input  chemical analysis of the weld metal  dilution effect with the base material  PWHT  purity of the weld metal deposit affect the mechanical properties of the weld metal Impact and tensile properties requirement are the main concern for high productivity welding process (FCAW-SAW) because  Heat Input  chemical analysis of the weld metal  dilution effect with the base material  PWHT  purity of the weld metal deposit affect the mechanical properties of the weld metal Appendix 6 (p. 8/16)

9. C.T.A.S. General trend: Yield strength versus toughness Looking for a minimum requirement on all weld metal deposit induces an over matching of properties on real application and a loss of toughness Appendix 6 (p. 9/16)

10. C.T.A.S. Overmatching : WELDING PROCESS WELDING PROCESS welding parameters (WP) : Amp-volt-speed  Heat Input (HI) welding parameters (WP) : Amp-volt-speed  Heat Input (HI) process with “narrow range” of WP  low HI / low productivity shielding metal arc welding (SMAW) tungsten inert gas (TIG) process with “narrow range” of WP  low HI / low productivity shielding metal arc welding (SMAW) tungsten inert gas (TIG) process with “wide range” of WP  high HI / high productivity Flux cored arc welding (FCAW) Sub merged arc welding (SAW) process with “wide range” of WP  high HI / high productivity Flux cored arc welding (FCAW) Sub merged arc welding (SAW) Appendix 6 (p. 10/16)

11. C.T.A.S. Overmatching : FCAW - SAW  considering a certain chemical analysis FCAW - SAW  considering a certain chemical analysis the welding parameters have to be precisely defined to reach the required YS and the welding parameter range becomes narrow the welding parameters have to be precisely defined to reach the required YS and the welding parameter range becomes narrow YS and TS increasing  Impact decreasing YS and TS increasing  Impact decreasing Appendix 6 (p. 11/16)

12. C.T.A.S. Overmatching : chemical analysis of the weld metal  purity of the weld metal deposit P,As,Sn,Sb are considered in Y (Brsucato Factor) Y=(10Sb+5Sn+2P+As)/100 (ppm)  O2 affects the impact properties before PWHT (basic flux-low oxygen) chemical analysis of the weld metal  purity of the weld metal deposit P,As,Sn,Sb are considered in Y (Brsucato Factor) Y=(10Sb+5Sn+2P+As)/100 (ppm)  O2 affects the impact properties before PWHT (basic flux-low oxygen) Appendix 6 (p. 12/16)

13. C.T.A.S. Overmatching : chemical analysis of the weld metal  dilution with the base material if we consider a certain chemical analysis defined to obtain certain mechanical properties in all weld metal (without dilution effect) this mechanical behaviour can be modified by the dilution effect and the welding material could be not allow to meet the requirement chemical analysis of the weld metal  dilution with the base material if we consider a certain chemical analysis defined to obtain certain mechanical properties in all weld metal (without dilution effect) this mechanical behaviour can be modified by the dilution effect and the welding material could be not allow to meet the requirement Appendix 6 (p. 13/16)

14. C.T.A.S. Overmatching : PWHT effect on weld metal properties  PWHT reduces the YS and TS but it could decrease the impact properties  N2-V-Nb affect the impact properties after PWHT (precipitation on V-Nb nitrides) N2 should be less than 0,006% in weld metal but the total amount of N2 in the weld metal depends not only of the welding consumable but also of the skinless of the welder mainly for manual process PWHT effect on weld metal properties  PWHT reduces the YS and TS but it could decrease the impact properties  N2-V-Nb affect the impact properties after PWHT (precipitation on V-Nb nitrides) N2 should be less than 0,006% in weld metal but the total amount of N2 in the weld metal depends not only of the welding consumable but also of the skinless of the welder mainly for manual process Appendix 6 (p. 14/16)

15. C.T.A.S. Hydrogen Hydrogen in the weld metal increasing the tensile properties the wed metal becomes more and more sensitive to the “cold cracking”  Diffusible Hydrogen in the weld metal (as lower as possible) (Standards require max 5ml/100gr)  preheat and interpass temperature during welding (Standards require 120 - 180°C)  Crack propagation depending on stress state - strength of material - plastic strain capacity  Heat Input defined to reduce the stress state Hydrogen in the weld metal increasing the tensile properties the wed metal becomes more and more sensitive to the “cold cracking”  Diffusible Hydrogen in the weld metal (as lower as possible) (Standards require max 5ml/100gr)  preheat and interpass temperature during welding (Standards require 120 - 180°C)  Crack propagation depending on stress state - strength of material - plastic strain capacity  Heat Input defined to reduce the stress state Appendix 6 (p. 15/16)

16. C.T.A.S. HIGH STRENGTH STEEL - 490 - 690 MPa ASPECTS TO DEFINE: ASPECTS TO DEFINE: WHAT IS THE min WM YS NEEDED TO HAVE AN ACTUAL OVERMATCHING ? WHAT IS THE min WM YS NEEDED TO HAVE AN ACTUAL OVERMATCHING ? WHAT IS THE IMPACT PROPERTY REQUIRED TO THE WM ? WHAT IS THE IMPACT PROPERTY REQUIRED TO THE WM ? IS THE PWHT NECESSARY? IS THE PWHT NECESSARY? WHAT’S THE “IDEAL” CHEMICAL ANALYSIS [Y (5-10)? - V-Nb%?]  INDUSTRIAL PRODUCT WHAT’S THE “IDEAL” CHEMICAL ANALYSIS [Y (5-10)? - V-Nb%?]  INDUSTRIAL PRODUCT WHAT IS THE MAX. DIFFUSIBLE HYDROGEN ACCEPTABLE FOR A PRACTICAL WELDED JOINT (5-3-2 ml/100gr)? WHAT IS THE MAX. DIFFUSIBLE HYDROGEN ACCEPTABLE FOR A PRACTICAL WELDED JOINT (5-3-2 ml/100gr)? Appendix 6 (p. 16/16)