Ševčík: High Temperature Strength Analysis of Low Carbon Steels in the as - Cast State

High-temperature properties of the continually cast low carbon steel slabs are tested on various equipments [1 7]. The high temperature tensile strength test is the most used one and the primary evaluated quantity, plasticity, is mostly assessed by reduction of area values. Several heating techniques are used for high temperature tensile strength tests and the testing is performed at various deformation speeds. During testing the specimens are placed mostly in vacuum, or in a protecting, usually argon, atmosphere. Specimens with circular cross-section are ordinarily used. Their diameter was from 5 to 20 mm and length between 15 200 mm. The testing itself can be realized after heating the specimens on temperatures under the solidus temperature or, if arrangement of the experiment enables it, after melting the specimens and then cooling them down to the testing temperature. Results of the study of the influence of chemical composition and microstructure on the strength values at high temperature tensile tests are described and discussed. By increasing the testing temperature, strength values in the low carbon steel slab continually decrease. Mathematical description of the temperature course and scatter zone of strength values was realized. Influences of the chemical composition and grain size on the strength values in a temperature interval from 900 to 1500 °C with a step of 100 or 50 °C was established by means of regression analyses. These influences are temperature-dependent. Strength values at 1400 °C, which chiefly depend on the effective grain size, were thoroughly analyzed.