The paper presents results of tests concerning butt welded joints made of structural high-strength steel S1100QL using the robotic welding station. The subject of the tests was to determine the effect of cooling time t_8/5 on primary mechanical properties of joints. Time t_8/5 was controlled by changing preheating temperature in relation to constant linear energy (SE samples) and changing linear energy in relation to constant heating temperature (ST samples). Both of the above-named cases involved the preparation of three test plates in relation to three times of 5 seconds, 7.5 seconds and 10 seconds. Welded joints subjected to non-destructive and destructive tests represented quality level B (according to PN-EN ISO 5817). No effect of time t_8/5 on mechanical properties was noticed in terms of the ST series specimens. The tensile strength identified in the tests amounted to 1020 MPa. The specimen ruptured in the weld. However, the effect of the tensile strength on hardness was noticeable, particularly in the HAZ (even above 450 HV1). The reverse tendency could be observed in relation to the SE specimens. The value of time t_8/5 was important in terms of joint strength, amounting to more than 1100 MPa in relation to the shortest time, where the specimen ruptured in the HAZ. In turn, the effect of time t_8/5 was negligible as regards hardness.

doi: 10.17729/ebis.2022.4/5