Search

Copyright of Kemija u Industriji is the property of Croatian Society of Chemical Engineers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper shows the trend of the world crude steel production in the first two decades of the 21st century. From 2000 to 2020, the world steelmaking continuously increased (total production of 28.5 billion t steel), but decreased in 2008 (1,6 %) and 2009 (7,7 %) because of the global financial and economic crises. For more than fifty years, the primary steelmaking processes are those by means of two technologies: oxidation of pig iron (product from blast furnace) in basic oxygen converters by means of technical oxygen, and smelting of old ferrous (steel scrap) in the electro arc furnaces. For the production of quality steel, the secondary metallurgy procedures (treatment of steel in ladle) play a greater role. In 2000, global steel production was 847.2 million t (basic oxygen converters share was 58.2 % and the electro arc furnaces 33.8 %), while in 2020, production reached 1.8775 billion t steel, which is an increase of 2.2 times. By 2020, the production of steel by steelmaking processes was 73.2 % by basic oxygen converters, 26.3 % by electro arc furnaces, 0.3 % by Siemens-Martin furnaces, and 0.2 % by other procedures of steel production. Primacy in steelmaking is in countries and companies from Asia (73.9 % of the world’s output). The recycling degree of steel in the period from 2011 to 2019 was 34–37 %. China is the largest world steelmaking country (since 1996). China had an increase in steelmaking of 8.3 times in the period from 2000 to 2020 (from 127.2 Mt up to 1.064 Gt). China produced 56.6 % of the world’s steel. From 2000 to 2020, a share of continuous casting was increased by about 10 % (from 87 to 96.6 %). [ABSTRACT FROM AUTHOR]

This paper presents the results of thermal and microstructural analysis of Cu-Al-Ni shape memory alloy before and after heat treatment. After casting, a bar of Cu-12.8 Al-4.1 Ni (wt.%) alloy, obtained by the vertical continuous casting technique, was subjected to a certain heat treatment procedure. Solution annealing was performed at 850 °C for 60 min, followed by water quenching. Tempering was then performed at four different temperatures (150 °C, 200 °C, 250 °C and 300 °C). The microstructural results were obtained by optical and scanning electron microscopy. Thermodynamic calculation of ternary Cu-Al-Ni system under equilibrium was performed using Thermo-Calc 5 software. Phase transformation temperatures were determined by differential scanning calorimetry (DSC). The DSC results show the highest values of transformation temperatures in as-cast state. After solution annealing and tempering, the transformation temperatures show lower values with exceptional stability of Ms temperature (martensite start temperature). [ABSTRACT FROM AUTHOR]