Abstract
Fine-grained steels belong to the progressive materials, which are increasingly used in the production of welded structures subjected to both static and dynamic loads. These are unalloyed or microalloyed steels hardened mainly by the grain-boundary strengthening mechanism. Such steels require specific welding procedures, especially in terms of the heat input value. At present, there are studies of the welding influence on the change of thermomechanically processed steels’ mechanical properties, however mainly under static loading. The paper is therefore focused on the assessment of the welding effect under dynamic loading of welded joints. In the experimental part was determined the influence of five different heat input values on the change of weld fatigue life. As a result, there is both determination of five S-N curves for the double-sided fillet welds from the thermomechanically processed fine-grained steel S460MC and the quantification of the main influences reducing the fatigue life of the joint.
Highlights
In today’s modern and innovative times, more and more demands are placed on industrially used materials
These are usually microalloyed fine-grained steels that are alloyed by very low contents of elements such as, e.g., V, Ti, and Nb. Such elements form fine carbides, nitrides, or carbonitrides and contribute to the grain refinement and strengthening of the matrix [1,2]. It has a secondary effect in increased values of the yield strength and ultimate tensile strength, but there is lower values of transient temperature and brittle fracture properties [3,4]
Not many papers are devoted to the influence of welding on changes in the fatigue life of welded joints for HSLA steels with a yield strength lower than 550 MPa [10], despite the fact that these materials and welded structures are used very often—for example, in land transportation [11]
Summary
In today’s modern and innovative times, more and more demands are placed on industrially used materials. Not many papers are devoted to the influence of welding on changes in the fatigue life of welded joints for HSLA steels with a yield strength lower than 550 MPa [10], despite the fact that these materials and welded structures are used very often—for example, in land transportation [11] (i.e., in areas of quite intense dynamic loading). Most authors studying the HSLA steel welds’ fatigue life usually focus on the butt welds from the high-strength steels If they deal with the fillet welds, there are performed fatigue tests at selected stress amplitudes within the loading cycles from up to 2 × [17], and for the remaining stress amplitudes are just used an approximation of the fatigue curves or there are used cruciform welds at testing [18,19]. Very important is knowledge about mutual proportion among the yield strength, fatigue limit of the base material σc(BM) , and fatigue limit of the fillet welded joint σc(W) from steel S460MC and its comparison with the (ultra) high-strength steels, presented by other authors
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