Key words: cast steel, puddled steel, ore mine, steel screw Andrzej ŻAK * INVESTIGATION OF SCREWS FOUND IN WILHELM ORE MINE This article presents macro- and microscopic investigation of steel screws which were found during exploration ore mine Wilhelm. The mine is placed in Lower Silesia and was closed in year 1925. During investigation I proved that they were produced of puddled or cast steel. It has been confirmed, that screws were made at the turn on 19 th and 20 th century. I also described differences in heat treatment between two objects. 1. INTRODUCTION 1.1. ORIGIN OF THE ISSUE In the year 2011, during exploration of closed ore mine Wilhelm in Lower Silesia some old steel screw were found. Mine worked from year 1897 to 1925. It was necessary to find out if screws were really produced at the turn on 19 th and 20 th century or they were left there later. Investigation were done in laboratories of Institute of Materials Science and Applied Mechanics. 1.2. EXAMINATED OBJECTS Screws were covered with rust and other products of corrosion process (fig.1). They were put into container with rust remover for about twelve hours. Some products of corrosion were also mechanically removed. As a result there were obtained a quite pure surface of both objects (fig.2). * Wroclaw University of Technology, Faculty of Mechanics, I. Łukasiewicza 5, 50-371 Wrocław
Fig. 1. Screws before preparing.. Fig. 2. Screws after preparing. 2. MACROSTRUCTURES AND MICROSTRUCTURES OF SCREWS 2.1. MACROSTRUCTURE Screws were cut, polished and etched (fig.3). In the bigger screw we can clearly see effects of forging the material. It has been cold worked at temperature below its recrystallization temperature. There is also visible a great amount of corrosion effects. Screw was for sure not heat treated. We can see a lot of non-metallic impurities. Smaller screw is also corroded, especially at a bolt head. In the cylindrical part we can see some signs of plastic deformation at temperature below recrystallization temperature. Very interesting is a structure of a bolt head. It had been heat treated in the end of production process. Structure is characteristic for steel after normalization. The head were probably heated above the upper critical temperature and then cooled in open air.
Fig. 3. Macrostructure of the bigger and smaller screw. 2.2. MICROSTRUCTURE Microscopic views of the bigger screw structure (fig.4, fig.5) show the structure characteristic to old puddled steel [1][4]. There are a lot of big, non-metallic impurities (fig.4). They have significantly decreased strength of material. In greater magnification (fig.5) we can see a structure composed of ferrite and small amount of cementite at the grain boundaries. It is one of the effects of microstructural degradation processes. Another visible effects are small, non-metallic impurities both inside the grains and at the grain boundaries. Amount of carbon in analyzed alloy is low, material is probably made by iron, silicon, manganese, sulfur and phosphorus [1]. Microscopic structure is similar to structure of steel from Pomorski Środkowy Bridge in Wroclaw, presented in Grzegorz Lesiuk and Mieczysław Szata article [4]. Microscopic views of the smaller screw structure (fig.6, fig.7) show the structure characteristic to the old cast steel [1][4][5]. It is hypo-eutectoid composed of ferrite and lamellar pearlite. In the cylindrical body structure is banded to direction of plastic deformation (fig. 6). Amount of carbon is greater than in the bigger screw and the amount of on-metallic impurities is a few times smaller. There are also some signs of microstructural degradation process. In bands of ferrite there are few impurities in the middle of grains and cementite at the grain boundaries (fig. 7). Also pearlite was locally separated into ferrite and cementite. It is one of the greater signs of degradation
process [5]. Microstructure is similar to the view of steel from Pomorski Północny Bridge in Wroclaw [4]. Fig. 4. Microstructure of the bigger screw magnification 100x. Fig. 5. Microstructure of the bigger screw magnification 400x.
Fig. 6. Microstructure of the smaller screw magnification 100x. Fig. 7. Microstructure of the smaller screw magnification 400x.
3. SUMMARY Two screws found in the Wilhelm ore mine have completely different structure. The biggest one was produced from puddle steel typical to a second half of 19 th century. The smallest screw was produced from the modern cast steel. It was also heat treated in a selected part for better strength. Objects were found in the level of 120 meters depth [10], active in years 1907-1919. It was confirmed that bigger screw was produced at the turn on 19 th and 20 th century. The second one probably was produced in early 20 th century. REFERENCES [1]CZAPLIŃSKI Kazimierz, Dawne wyroby ze stopów żelaza, Wydawnictwo DWE, Wrocław 2009; [2]DUDZIŃSKI Włodzimierz, WIDANKA Krzysztof, Ćwiczenia laboratoryjne z materiałoznawstwa, Oficyna Wydawnicza Politechniki Wrocławskiej, Wrocław 2009; [3]HAIMANN Rudolf, Metaloznawstwo, Politechnika Wrocławska, Wrocław 1980; [4]LESIUK Grzegorz, SZATA Mieczysław, Degradacja mikrostruktur elementów konstrukcyjnych pochodzących z mostów wzniesionych na przełomie XIX i XX wieku, in: Zeszyty naukowe WSOWL, 1/2010; [5]PĘKALSKI Grzegorz, Degradacja maszyn wydobywczych zagadnienia materiałowe, IMiMTPWr, Wrocław; [6]PĘKALSKI Grzegorz, Korozja i ochrona przeciwkorozyjna, IMiMTPWr, Wrocław 1987/88; [7]PIECHOTA Stanisław, Technika podziemnej eksploatacji rud, Wydawnictwo AGH, Kraków 1988; [8]PŁANETA Stefan, Systemy eksploatacji podziemnej złóż rud. Koncepcja i praktyka górnicza, Oficyna Wydawnicza Politechniki Wrocławskiej, Wrocław 2009; [9]SADOWSKI Roman, Do Radzimowic po złoto i?, in: bolkow.net; [10]Kopalnia Stara Góra. Plan robót górniczych. Sekcja 9, Przedsiębiorstwo Geologiczne Rud Nieżelaznych z tymczasową siedzibą w Stalinogrodzie, 1951-1957, archiwum prywatne Adam Wojcieszonek;. BADANIE ŚRUB ZNALEZIONYCH W NIECZYNNEJ KOPALNI RUD METALI WILHELM Artykuł prezentuje badania makro- i mikrostruktury śrub stalowych znalezionych podczas eksploracji zamkniętej w roku 1925 kopalni Wilhelm na Dolnym Śląsku. Na drodze analizy zgładów metalograficznych wyróżniono struktury charakterystyczne dla starych stali zgrzewnych i zlewnych. Potwierdzono tym samym wiek elementów na przełom XIX i XX wieku. Dostrzeżono ponadto ślady bardzo starannej obróbki cieplnej na jednym z obiektów, wykonanym ze stali zlewnej. Zasygnalizowało to wysoki poziom wiedzy i staranności u producenta tego elementu.