*3.2. Press Hardening Trials of Hat Shaped Profiles*

Steel blanks having dimensions 1.3 × <sup>70</sup> × 150 mm<sup>3</sup> were cut from cold rolled sheets, heated in a furnace to 930 ◦C and held for 4 min, prior to transferring them to the tooling within ~9 s. The dies were preheated to enable the blank temperature to be controlled during forming and simultaneous quenching of the hat profile. The dies were closed in 2.5 s and the blanks cooled in the dies for 8 s to a temperature corresponding to *Ms* − 10 ◦C. The blanks were then transferred to a second furnace within ~11 s and held at *Ms* + 30 ◦C for 5 min before air cooling to room temperature. The temperature was measured using a thermocouple welded to the blank. Examples of typical temperature–time curves recorded on the blanks during press hardening are shown in Figure 1. Six hat profiles were produced from steel CR1 and five from steel CR3. The quenching temperatures were controlled within 4 ◦C, for all CR1 samples and 2 ◦C for 4 out of 5 CR3 samples with regard to the set value (*Ms* − 10 ◦C). The measured temperature for the fifth CR3 sample was 9 ◦C below the set value. The heat created when austenite was transformed to martensite and bainite respectively increased the temperature in the samples, but the furnace temperature was controlled so that the set value (*Ms* + 30 ◦C) was reached within 5 min.

**Figure 1.** Typical temperature–time curves during press hardening of hat profiles of steels CR1 and CR3.
