Papers by Keyword: Gray Iron

Abstract: This study investigates the formation and distribution of titanium carbide (TiC) in gray iron with varying titanium (Ti). Gray cast iron samples were produced with Ti levels ranging from 0.033 to 0.349 wt% using a 100-kg induction furnace. The microstructures of the samples were examined using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS), showing that TiC particles are the predominant TCCs in this study. It was found that TiC particles were dispersed around graphite and matrix structures. The number of TiC increased with Ti. The Gibbs free energy calculations supported the formation of TiC both in molten and solid states.

Abstract: Gray iron, a widely used engineering material, is favored for its desirable properties such as good damping capacity, thermal conductivity, and corrosion resistance. However, when exposed to elevated temperatures over time, issues like oxidation and graphite depletion can impact its durability. High-silicon gray iron, with elevated silicon content exceeding 3.0%, is known for its ability to withstand heat and oxidation, making it suitable for many applications, including cookware. This study investigates the impact of varying silicon levels (2.00-4.56%Si) on the solidification behavior, microstructure, and oxidation resistance of gray iron. Three heats with different silicon concentrations were produced and analyzed. Results indicated that higher silicon content increases the eutectoid temperature, stabilizes the ferritic structure, and introduces Type-D graphite in the microstructure. Graphite depletion was observed only in samples with 2.00%Si. The oxidation resistance improved with higher silicon content, as evidenced by a decrease in weight gain after exposure to 800 °C for 4 hours. This suggests the potential of using lower silicon levels in gray iron for cookware applications, balancing material cost with good impact resistance.

Abstract: This study investigates the microstructure and the solidification behavior of titanium-alloyed gray irons. Thermal analysis technique was used to identify the Temperature of Liquidus Arrest (T_LA), the Temperature of Eutectic Undercooling (T_EU) and the Temperature of the Eutectic Recalescence (T_ER). It was found that the titanium addition promoted the formation of the primary austenite causing the larger difference in T_LA and T_EU. In addition, titanium encouraged the refining of eutectic mixture. The SEM showed the graphite particles were refined with increasing titanium. Fine particles of titanium-containing compound were readily observed throughout the microstructure. The hardness as high as 176 HB was achieved at 0.495%Ti addition.

Abstract: Fatigue strength and fracture of high strength cast irons, gray iron grade 300 and CGI grade 450, used for producing lightweight cylinder blocks, were studied. The results show endurance ratios of 0.27-0.28 and 0.38 for gray irons and CGI, respectively. The fracture surfaces in cast irons in general show the predominance of graphite and graphite/matrix interface; however, in CGI there is a larger proportion of fractured pearlitic matrix than in gray iron. This fact, and the differences in the morphology of the graphite/matrix interface, flat in gray iron, rough in CGI, explain the higher results of fatigue strength in CGI compared to gray iron. The results of fatigue strength are compared with the literature and with previous works.

Abstract: Hot strength and fracture mechanisms in high quality cast irons were studied, comparing the standard gray iron Grade 300, alloyed with Mo, typically used for cylinder heads in high power engines, with other two materials: one gray iron Grade 300, obtained through graphite refinement and one compacted graphite iron, Grade 450. In these last two materials, the strength increase was obtained by changing the graphite structure, not by hardening the matrix. The experimental results with tensile tests carried out up to 500 °C show that the different strengthening mechanisms, use of Mo or modification of the graphite structure, are both efficient for increasing the strength at room temperature as well as at high temperatures. The CGI has a lower strength reduction with temperature than the gray irons, which shows the significant impact of the compacted graphite shape in reducing the notch effect. These results show the enormous potential of CGI in cylinder heads for high-performance engines.

Abstract: The present study is undertaken to investigate the influence of annealing and normalizing heat treatment on the bimetallic interface microstructures of 304 stainless steel and gray cast iron. The current work is aim to control the bimetal interface microstructures by different types of heat treatment processes to improve performance of the bimetallic castings performance. For low temperature annealing, specimens are heated to 760 0C for 60 min in an electrical heating furnace. For high temperature annealing and normalizing, specimens are heated to 920 0C for 120 and 240 min. A different interface structures are obained for all heat treated samples. Annealing and normalizing induce a significant effect on the diffusion of C and Cr elements and slightly effect on the diffusion of Ni element. Thickness of interface layer 1 (austenite + carbide) increases by increasingthe annealing temperature.

Abstract: Bimetallic castings are widely employed as working elements in winning machines which work in conditions of intensive friction wear. The main features of wear are: dynamic percussive loads, intensive abrasive wear caused by erosion and corrosion. Three cylindrical rods cavities of the same dimensions of φ 20x200 mm were made in sand mould. Different amount of liquid iron alloy with carbon equivalent of 4.14, Mn of 0.58 and Cu of 0.17 wt% was poured into the three rod cylindrical cavities over the solid 304 stainless steels cylindrical desks inserts. Good coherent interfaces for all liquid/Solid volumes (16 to 24) are produced and multi-layers interfacial microstructure bimetal are produced. Increasing the liquid/solid volumes from 16 to 24 increases the thickness of transient layer from 52 to 89 μm and decreases the amount of ledeburite in the structure of solidified gray cast iron.

Abstract: A results of test of erosion and corrosion resistance of pearlitic gray cast iron (grade EN GJ 400) are showed. The NaCl solutions and of ethylene glycol solutions were used as the test environment. Examination were performed at varying cavitation load, in the range 2,8 ÷ 20 W/cm².

Abstract: Investigation of dynamic coarsening in lamellar cast iron is extended over a wide interval ranging from hypoeutectic to eutectic composition. The dendrite morphology is defined on as-cast samples produced under various cooling rates. The as-cast morphology is considered being close to the one at the end of solidification. The obtained relations describing the coarsening process as a function of local solidification time and fraction austenite are compared to results obtained from interrupted solidification experiments. By using the Modulus of primary dendrite (M_PD) and the Hydraulic diameter of the interdendritic space (D^Hyd_IP) become possible to characterize the coarseness of a wide range of lamellar cast irons solidified under various cooling rates.

Abstract: Dynamic coarsening of austenite dendrite in lamellar cast iron has been studied for a hypoeutectic alloy. The common morphological parameter to characterize dynamic coarsening, secondary dendrite arm space has been replaced by the Modulus of primary dendrite ( M_PD ) and the Hydraulic diameter of the interdendritic space ( D^Hyd_IP ) to interpret the dynamic coarsening with respect to the local solidification time. The obtained results demonstrate the coarsening process of both the solid and liquid phase. The interdendritic space is increasing as the contact time between the solid and liquid phase increases. The ratio between the D^Hyd_IP/M_PD is strongly dependent on the precipitated fraction primary austenite indicating clearly the morphology variation during coarsening. The interrupted solidification method demonstrate that the observed coarsening process is not only a combination of the increasing fraction precipitated solid phase and the rearrangement of the solid liquid interphase curvature but the volume change due to density variation is also contribute to the coarsening process. Keywords: dendrite morphology, hydraulic diameter, interdendritic space, gray iron.