# MAG Welding Tests of Modern High Strength Steels with Minimum Yield Strength of 700 MPa
## 3 Results and Discussion  
### Tensile Tests  
Figures 5 and 6 present the tensile test results for all base materials. In Figure 5, elongations are given and, in Figure 6, strength values are presented. The results are presented for specimens in as-welded (with reinforcement) and in machined condition (with flat surface of weld seam). In Figure 6, both yield and ultimate tensile strength are given so that the solid bar represents yield strength and the transparent bar represents ultimate tensile strength. For efficiency of the analysis of the results, base material values are also included in the figures. According to Figure 5, the total elongation of S690 QL is 16.3%, whereas the total elongations of base materials of TMCP (MC) steels are 13.4 and 13.1%. With the lowest heat input, S690 QL has as well the longest elongations with differences of 3-4% (machined) and 4-6% (with reinforcement) compared to the TMCP steels. The welding decreases the elongation of all materials, but the elongation of S690 QL is more affected by increasing heat input than the elongation of TMCP steels. In S690 QL with machined specimens, the elongation reaches the minimum value of 7.0% for the weld t\({}_{8/5}\) = 10 s. In reinforced specimens of S690 QL, there is a decreasing trend in elongations of the welds among increasing heat input from the value 14.4% (t\({}_{8/5}\) = 5 s) to 9.1% (t\({}_{8/5}\) = 20 s). However, with reinforcement, S690 QL shows the highest elongations even though the elongation is clearly reduced by increasing heat input and therefore, with high heat input, the elongation of S700 MC-2 with the value 9.2% is very similar to the value of S690 QL (9.1%). With machined weld specimens, the S700 MC-2 exhibits the highest elongations (9.3-10.4%), except with the lowest heat input (9.2%). The elongations of S700 MC-1 are at all points about 1-2% lower than the elongations of S700 MC-2. The reason for the higher drop of elongation of the machined specimens from the S690 QL is related with higher strain localization in zones adjacent to the coarse gain zones because less weld metal exists to distribute the deformation energy. Figure 5: Elongations of the welds: (**a**) machined specimens; (**b**) specimens with reinforcements. Figure 6: Yield and ultimate tensile strength of the welds: (**a**) machined specimens; (**b**) specimens with reinforcements. Figure 6 reveals that the yield strength is more affected by the welding heat input than the ultimate tensile strength. The highest yield strength in the base material is measured at the S690 QL, which is 812 MPa. Therefore, after welding, the relative decrease in yield strength in S690 QL is bigger than in TMCP steels and the same trend can be seen with the machined specimens as well as with the reinforced specimens. When considering the tensile strength, an opposite behavior can be observed. Initially, S690 QL has the lowest tensile strength (859 MPa), but, in the welded specimens, the tensile strength is higher than in other materials (Rm of high heat input welds: 783 MPa machined, 832 MPa in as-welded condition). When comparing the TMCP steels with each other, the yield strength of S700 MC-1 base material is about 40 MPa higher than in S700 MC-2. In that sense, the yield strength of S700 MC-2 is maintained better after welding than in S700 MC-1 because the strength of the high heat input weld of S700 MC-2 is only 14 MPa lower than the S700 MC-1 when machined specimens are compared. When considering specimens in as-welded conditions, the yield strength of the high heat input weld of S700 MC-2 is 12 MPa higher than the yield strength of S700 MC-1. By contrast, the tensile strength of S700 MC-2 is initially 23 MPa higher than in S700 MC-1. In that regard, S700 MC-1 retains the tensile strength better than S700 MC-2.