Browsing by Author "Krawczyk, Janusz Ryszard"

Now showing 1 - 7 of 7

Access status: Open Access ,
Banded microstructure in forged 18CrNiMo7-6 steel
(2009) Krawczyk, Janusz Ryszard; Pawłowski, Bogdan; Bała, Piotr
18CrNiMo7-6 steel, after hot forging, exhibits a distinct banding of ferritic-pearlitic microstructure, probably related to the segregation of alloying elements during the ingot crystallization. The heat treatment allowing to obtain bainitic microstructure in this steel is described in the paper. The obtained bainitic microstructure exhibits only very small traces of banding.
Access status: Open Access ,
Effect of the cooling rate on the mottled cast iron microstructure designed for the mill rolls
(2009) Krawczyk, Janusz Ryszard; Pacyna, Jerzy
The influence of the cooling rate changes on the mottled cast iron microstructure was described in the paper. The investigated material constituted mottled cast iron, spheroidal, chromium-nickel. This cast iron, according to currently binding standards was marked GJS-HV300(SiCrNi2-3). The microstructure was described both qualitatively and quantitatively. The discussion of the formation mechanisms and their influence on the morphology of structural components and phases was conducted. The heat treatment was performed in such a way as to obtain either a pearlitic or a bainitic matrix as well as a different morphology of lederburitic cementite and graphite precipitates for the same matrix.
Access status: Open Access ,
Some factors influencing the determination of eutectoid transformation start and finish temperatures in hypoeutectoid steels
(2009) Pawłowski, Bogdan; Bała, Piotr; Krawczyk, Janusz Ryszard
This paper presents problems related to the proper determination of the eutectoid transformation start and finish temperatures in steels during heating. Information from references indicate an essential influence of interlamellar spacing in pearlite on the formation of the dilatation effect related to the eutectoid transformation finish, on dilatometric curves. It was revealed, in this paper, that the appearance of the dilatation effect related to the eutectoid transformation finish in hypoeutectoid steels or its lack in the heating dilatograms depends on the resolution ability of the applied dilatometer.
Access status: Open Access ,
The effect of non-metallic inclusions on the crack propagation impact energy of toughened 35B2+Cr steel
(2008) Krawczyk, Janusz Ryszard; Pawłowski, Bogdan
35B2+Cr steel was designed as a material for screws. The investigations were carried out on toughened samples, taken from three ingots of 35B2+Cr steel (delivered from three various steel suppliers), and of different content of non-metallic inclusions. In each case, the fraction of non-metallic inclusions was in agreement with the corresponding standard. This study presents the results of the research focused on the influence of non-metallic inclusions on the impact energy of crack development in 35B2+Cr steel. The role of non-metallic inclusions was considered both in relation to their total fraction and in relation to the fraction of oxides, sulfides, nitrides and exogenous inclusions separately. Assuming linear dependence between notch-root radius and the impact energy of crack nucleation, basing on the impact toughness tests, the impact energy of the crack development was evaluated. It was proved, that in spite of the level of fraction of non-metallic inclusions compatible with the corresponding standards, they directly or indirectly influence the impact energy of 35B2+Cr steel. This influence depends on the character of the inclusions.
Access status: Open Access ,
The high-temperature tribology of iron matrix hypoeutectic alloy after under-annealing normalizing
(2008) Krawczyk, Janusz Ryszard; Dziurka, Rafał; Rożniata, Edyta
This work includes the results of high-temperature tribology test of cast alloy with iron matrix. The paper presents the discussion on the results of the studies of wear mechanisms and friction factor of G200CrNiMo4-3-3 adamite cast steel after three variants of under - annealing normalization. During the heat treatment of cast steel four annealing temperatures were applied: 850, 900, 950 and 1050°C. Annealing was conducted for 10 h, and then the samples were cooled at a rate of 48°C/h to room temperature. Four different annealing temperatures resulted in adequate differences in microstructure of test cast steel what determinated tribological properties of the material. Results obtained allow for determination of optimal, from wear resistance point of view, microstructure of test cast steel used for mill rolls.
Access status: Open Access ,
The influence of microstructure of 30MnB4 steel on hydrogen-assisted cracking
(2015) Krawczyk, Janusz Ryszard; Bała, Piotr; Tokarski, Tomasz; Pawłowski, Bogdan; Frocisz, Łukasz
This paper analyzes the problem of susceptibility to hydrogen-assisted cracking (fracture behavior) of zinc-coated screws made of 30MnB4 steel. Two samples (screws) were compared after proper and improper heat treatment affecting hydrogen solubility during the further galvanic process and resulting in different fracture modes. Both samples were loaded to failure by torsion. The fracture surface and microstructure of the samples were examined using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS).
Access status: Open Access ,
The role of metallurgical defects and microstructure on failure formation in roll necks of cast iron rolls
(2007) Krawczyk, Janusz Ryszard; Pacyna, Jerzy
This work presents the examples of structural reasons for failure of the necks of cast iron rolls. The most common reason for damage of metallurgical roll necks is a presence of shrinkage porosity in their volume. Moreover, a high fraction of ledeburitic cementite can lead to the formation of a continuous net of eutectic carbides, which facilitate cracking. Even very thin net of secondary carbides, formed on the boundaries of former grain of austenite, can significantly facilitate propagation of the crack. Continuous net of ledeburitic cementite, in the case of its precipitation in a form of bands and existence of hardened areas in the alloy matrix can lead to roll neck fracture relatively easy. The use of flake graphite cast iron for metallurgical rolls increases a risk of the fracture of roll neck.