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Predicting ADI mechanical properties

100%

Giętka T. , Dymski S.

2009

tom Vol. 9, iss. 3

267-274

Ductile cast iron was quench-hardened with the isothermal transformation according to two alternatives. The first treatment alternative consisted in the austenitizing process at temperature t\gamma = 830, 860 i 900 oC and annealing at temperature tpi = 400, 350 and 300oC in a period of time up to 240 min. The second treatment alternative consisted in dual-stage austenitizing. The material was annealed in temperature of t\gamma = 950oC and cooled to temperature t\gamma = 900, 860 and 830oC. The isothermal transformation was performed in the same conditions as in the first alternative. The cast iron was ferritizingly annealed before the isothermal quench-hardening. The cast iron matrix after the annealing was ferritic. Metallographic cubic specimens with the size about of 10 mm were quench-hardened with the isothermal transformation. Matrix microstructure, austenite percentage and Vicker's hardness were determined using the specimens. Hardness test results were used to determine, on the base of material coefficients, tensile strength Rm, yield strength Rp0,2 and deformation A5. Tests showed that heat treatment according to two alternatives of the quench hardening led to obtain ADI cast iron with accordance to PN-EN 1564 : 2000 grade: EN-GJS-800-8, EN-GJS-1000-5, EN-GJS-1200-2. Only ausferritic cast iron was assumed as a base of qualification.

The influence of saturation of cast iron austenite with carbon on the ausferrite transformation

67%

Giętka T. , Szykowny T. , Dymski S.

2007

tom Vol. 7, iss. 3

241-246

Austenitizing during quench hardening of the ductile cast iron influences the content of carbon in austenite depending on the soaking heat. On the other hand, the saturation of austenite impacts its transformation in the ausferritizing process of a metal matrix and forming of microstructure. Ductile cast iron with the ferrite matrix was hardened with isothermal transformation in the range of ausferritizing in temperature [...]. Microstructure was investigated, there were also defined the proportion of austenite in the matrix of the cast iron and the content of carbon in it and hardness and impact strength in unnotched specimens. It was stated, that the precooling temperature deciding on the content of carbon in austenite influences kinetics of the ausferritic transformation, the content of carbon in the [gamma] phase and impact strength and, in a less degree, hardness. As a result of gradual austenitizing the cast iron after quench hardening, in some conditions of treatment, reached mechanical properties corresponding, according to the ASTM A 897 standard, with high grades of ADI. Chilling in the range of austenitizing in temperature 850 and 800 oC led to the decrease of carbon in austenite what influenced positively on the matrix microstructure and properties of the ADI. Investigations in this range will be continued.

Wpływ temperatury austenityzowania na charakterystyczne temperatury przemian w stopie Fe-30%Ni

67%

Ciura F. , Michta G. , Osuch W.

tom R. XXIV, nr 6

260-263

Badaniom poddano próbki ze stopu Fe-30%Ni różniące się morfologią i ilością martenzytu otrzymanego na drodze odkształcenia oraz w wyniku hartowania w ciekłym azocie. Zastosowanie metod magnetycznych pozwoliło na określenie charakterystycznych temperatur przemian fazowych oraz udziału poszczególnych faz powstałych w wyniku odkształcenia plastycznego oraz podczas chłodzenia w ciekłym azocie, a także podczas przemiany odwrotnej alfa'->gama w zakresie temperatur pomiędzy As i Af. W pracy podjęto również próbę określenia wpływu temperatury austenityzowania na charakterystyczne temperatury przemian w stopie Fe-30%Ni, wiążąc je ze strukturą badanego stopu.

The specimens of the alloy Fe-30%Ni with different martensite morphology and content were achieved by deformation and quenching at temperature of liquid nitrogen. By means of magnetic methods the temperatures of phase transformations and the phase contents at the particular steps of treatment (i.e. after plastic deformation quenching in liquid nitrogen and reverse transformation between As and Af temperatures) were determined. The microstructural investigations enabled the determination of the influence of the austenitizing temperature on the transformations temperatures.