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High strength hot rolled and aged microalloyed 5% Ni steel

100%

Lis A. K. , Lis J.

tom Vol. 18, nr 1-2

37--42

Purpose: Purpose of this paper was to give information about low temperature strength and impact CharpyV toughness of low carbon microalloyed 5%Ni bainitic steel after thermomechanical rolling (TMR) or thermomechanical controlled processing (TMCP) and ageing at different temperatures: 580°C/2 h, 640°C/1h and 680°C/1h. Design/methodology/approach: The tensile strength tests were performed at -196, -60 and 20°C and Charpy V samples were broken at -100, -80, -60, -40, -20 and 20°C temperatures. The tensile strength TS, yield strength YS, elongation A5 and reduction of area RA were established from tensile experiments. After TMCP 16 mm steel plate had YS = 730MPa, TS = 950 MPa, A5 = 22,5% and RA = 61% and impact energy > 50 J at -196°C. Findings: The best combination of mechanical properties; yield strength and Charpy V toughness was achieved for steel after TMR and ageing 580°C/ 2h; YS = 800MPa, TS = 900 MPa, A5 = 22.5%, at -1000C KVmin.= 110 J. Research limitations/implications: The precise methodology for retained austenite identification and its amount content determination in the investigated microstructures is still metallographic problem which needs to be resolved. Practical implications: The best combination of yield strength and Charpy V toughness was achieved for steel after TMR and ageing 580°C/ 2h. At liquid nitrogen temperature ultrahigh strength properties were: YS = 1140 MPa, TS = 1280 MPa, A5 = 26%, RA = 55% and KV 122 J at -100°C. Originality/value: The detailed microstructure examination of the steel with optical and mainly scanning transmission electron microscopy was needed to explain its good properties at very low temperature. TRIP effect was observed due to the presence of highly alloyed retained austenite in the microstructure. That type of steel may be used for contemporary military and structural applications working at low temperatures.

Komputerowe systemy pomiarowe w badaniach właściwości materiałów

84%

Rymaszewski J. , Pawlak R. , Lebioda M. , Tomczyk M.

tom z. 98

419-428

Zaprezentowano komputerowe systemy pomiarowo - kontrolne wykorzystywane w badaniach właściwości materiałów elektrotechnicznych. Trzy spośród nich zostały zrealizowane na potrzeby pomiarów parametrów elektrycznych materiałów. Czwarty system służy do ilościowej analizy obrazów i wykorzystywany jest w badaniach struktury materiałów.

The computer control-measurement systems have been presented in this paper. These systems are used in investigations of the properties of electrical materials. Three systems were achieved for the measurement of electrical properties of materials. The fourth system was achieved for quantity image analysis and it is used in investigations of materials microstructure.

Crack initiation in steel parts working in boilers and steam pipelines

84%

Renowicz D. , Cieśla M.

tom Vol. 21, nr 2

49-52

Purpose: The purpose of this paper is to identify the influence of loading history and the processes of material degradation on the crack initiation and on durability under thermo-mechanical fatigue conditions. Design/methodology/approach: Based on the operation data, the conditions of laboratory examinations of specimens were determined. A specialist apparatus unit was used for the examination, enabling the simulation of any spectrum of mechanical load and temperature changes. Findings: The material durability criterion has been defined based on an energy related approach to the problem of crack initiation in steels which work under thermal fatigue conditions. Research limitations/implications: In the case discussed, i.e. a pipeline part, the present criteria should be expanded with critical values describing the total length of cracks initiated on the internal surface of a specimen. Practical implications: The paper refers to the research on steel 10H2M (10CrMo.910) used in the conventional boilers, superheaters and pipelines in power plants. Originality/value: Originality of the paper is the methodology of the lifetime prediction of steam pipeline parts working in thermo-mechanical fatigue conditions.