Predicted hardness of Austempered Vermicular Graphite Iron

The aim of this study was to determine the hardness of vermicular cast iron subjected to austempering, depending on the parameters of the heat treatment process. The heat treatment was conducted based on orthogonal experimental design, with a total of 27 experiments performed. The samples underwent austenitization at temperatures of 890°C, 925°C, and 960°C, followed by austempering at 290°C, 340°C, and 390°C. The austenitization and austempering times were set to 90 min, 120 min, and 150 min. To analyse the influence of these parameters, a full polynomial regression model was developed. The proposed model, which describes the hardness of the cast iron after heat treatment, showed a predicted coefficient of determination (R²) of approximately 78%. For optimization purposes, the Response Surface Methodology (RSM) was employed. The results of the ANOVA analysis indicated that the austempering temperature (Tpi), the square of the austenitization time (τγ²), the interaction between austenitization temperature and time (Tγ τγ), as well as the interaction between austenitization and austempering temperatures (Tγ Tpi) had the most significant impact on the examined parameter. Following variance analysis, the model was refined once more to eliminate insignificant predictors. The simplified model improved the predicted coefficient of determination to 93%. The optimal conditions for the analyzed parameters, assuming a maximum hardness of approximately 440 HB, were obtained under the following heat treatment conditions: Tγ = 930°C, Tpi = 290°C, τγ = 150 min, and τpi = 150 min

Racial differences in systemic sclerosis disease presentation: a European Scleroderma Trials and Research group study

Objectives. Racial factors play a significant role in SSc. We evaluated differences in SSc presentations between white patients (WP), Asian patients (AP) and black patients (BP) and analysed the effects of geographical locations.Methods. SSc characteristics of patients from the EUSTAR cohort were cross-sectionally compared across racial groups using survival and multiple logistic regression analyses.Results. The study included 9162 WP, 341 AP and 181 BP. AP developed the first non-RP feature faster than WP but slower than BP. AP were less frequently anti-centromere (ACA; odds ratio (OR) = 0.4, P < 0.001) and more frequently anti-topoisomerase-I autoantibodies (ATA) positive (OR = 1.2, P = 0.068), while BP were less likely to be ACA and ATA positive than were WP [OR(ACA) = 0.3, P < 0.001; OR(ATA) = 0.5, P = 0.020]. AP had less often (OR = 0.7, P = 0.06) and BP more often (OR = 2.7, P < 0.001) diffuse skin involvement than had WP.AP and BP were more likely to have pulmonary hypertension [OR(AP) = 2.6, P < 0.001; OR(BP) = 2.7, P = 0.03 vs WP] and a reduced forced vital capacity [OR(AP) = 2.5, P < 0.001; OR(BP) = 2.4, P < 0.004] than were WP. AP more often had an impaired diffusing capacity of the lung than had BP and WP [OR(AP vs BP) = 1.9, P = 0.038; OR(AP vs WP) = 2.4, P < 0.001]. After RP onset, AP and BP had a higher hazard to die than had WP [hazard ratio (HR) (AP) = 1.6, P = 0.011; HR(BP) = 2.1, P < 0.001].Conclusion. Compared with WP, and mostly independent of geographical location, AP have a faster and earlier disease onset with high prevalences of ATA, pulmonary hypertension and forced vital capacity impairment and higher mortality. BP had the fastest disease onset, a high prevalence of diffuse skin involvement and nominally the highest mortality

Thermal Shock Resistance of Cast Iron with Various Shapes of Graphite Precipitates

The influence of a shape of graphite precipitates in cast iron on the thermal shock resistance of the alloy was initially determined. Investigations included the nodular cast iron and the vermicular one, as well as the cast iron containing flake graphite. The thermal shock resistance was examined at a special laboratory stand which allowed for multiple heating and cooling of specimens within the presumed temperature range. The specimens were inductively heated and then cooled in water of constant temperature of about 30°C. There were used flat specimens 70 mm long, 5 mm thick in the middle part, and tapering like a wedge over a distance of 15 mm towards both ends. The total length of cracks generated on the test surfaces of the wedge-shaped parts of specimens was measured as a characteristic value inversely proportional to the thermal shock resistance of a material. The specimens heated up to 500°C were subjected to 2000 test cycles of alternate heating and cooling, while the specimens heated up to 600°C underwent 1000 such cycles. It was found that as the heating temperature rose within the 500-600°C range, the thermal shock resistance decreased for all examined types of cast iron. The research study proved that the nodular cast iron exhibited the best thermal shock resistance, the vermicular cast iron got somewhat lower results, while the lowest thermal shock resistance was exhibited by grey cast iron containing flake graphite

The influence of small amounts of aluminium on the effectiveness of cast iron spheroidization with magnesium

The influence of aluminium added in amounts of about 1.6%, 2.1%, or 2.8% on the effectiveness of cast iron spheroidization with magnesium was determined. The cast iron was melted and treated with FeSiMg7 master alloy under industrial conditions. The metallographic examinations were performed for the separately cast rods of 20 mm diameter. They included the assessment of the shape of graphite precipitates and of the matrix structure. The results allowed to state that the despheroidizing influence of aluminium (introduced in the above mentioned quantities) is the stronger, the higher is the aluminium content in the alloy. The results of examinations carried out by means of a computer image analyser enabled the quantitative assessment of the considered aluminium addition influence. It was found that the despheroidizing influence of aluminium (up to about 2.8%) yields the crystallization of either the deformed nodular graphite precipitates or vermicular graphite precipitates. None of the examined specimens, however, contained the flake graphite precipitates. The results of examinations confirmed the already known opinion that aluminium widens the range of ferrite crystallization

The Leading Role of Aluminium in the Growing Production of Castings Made of the Non-Ferrous Alloys

The paper presents changes in the production volume of castings made of non-ferrous alloys on the background of changes in total production of casting over the 2000-2019 period, both on a global scale and in Poland. It was found that the dynamics of increase in the production volume of castings made of non-ferrous alloys was distinctly greater than the dynamics of increase in the total production volume of castings over the considered period of time. Insofar as the share of production of the non-ferrous castings in the total production of castings was less than 16% during the first two years of the considered period, it reached the level of 20% in the last four years analysed. This share, when it comes to Poland, increased even to the greater degree; it grew from about 10% of domestic production of castings to over 33% within the regarded 2000-2019 period. The greatest average annual growth rate of production, both on a global scale and in Poland, was recorded for aluminium alloys as compared with other basic non-ferrous alloys. This growth rate for all the world was 4.08%, and for Poland 10.6% over the 2000-2019 period. The value of the average annual growth rate of the production of aluminium castings in Poland was close to the results achieved by China (12%), India (10.3%) and the South Korea (15.4%) over the same period of time. In 2019, the total production of castings in the world was equal to about 109 million tonnes, including over 21 million tonnes of castings made of non-ferrous alloys. The corresponding data with respect to Poland are about 1 million tonnes and about 350 thousand tonnes, respectively. In the same year, the production of castings made of aluminium alloys was equal to about 17.2 million tonnes in the world, and about 340 thousand tonnes in Poland

The Influence of Small Amounts of Aluminium on the Effectiveness of Cast Iron Spheroidization with Magnesium

The influence of aluminium added in amounts of about 1.6%, 2.1%, or 2.8% on the effectiveness of cast iron spheroidization with magnesium was determined. The cast iron was melted and treated with FeSiMg7 master alloy under industrial conditions. The metallographic examinations were performed for the separately cast rods of 20 mm diameter. They included the assessment of the shape of graphite precipitates and of the matrix structure. The results allowed to state that the despheroidizing influence of aluminium (introduced in the above mentioned quantities) is the stronger, the higher is the aluminium content in the alloy. The results of examinations carried out by means of a computer image analyser enabled the quantitative assessment of the considered aluminium addition influence. It was found that the despheroidizing influence of aluminium (up to about 2.8%) yields the crystallization of either the deformed nodular graphite precipitates or vermicular graphite precipitates. None of the examined specimens, however, contained the flake graphite precipitates. The results of examinations confirmed the already known opinion that aluminium widens the range of ferrite crystallization

The Influence of the Shape of Graphite Precipitates on the Cast Iron Abrasion Resistance

The paper presents the initial results of investigation concerning the abrasion resistance of cast iron with nodular, vermicular, or flake graphite. The nodular and vermicular cast iron specimens were cut out of test coupons of the IIb type with the wall thickness equal to 25 mm, while the specimens made of grey cast iron containing flake graphite were cut out either of special casts with 20 mm thick walls or of the original brake disk. The abrasion tests were carried out by means of the T-01M tribological unit working in the pin-on-disk configuration. The counterface specimens (i.e. the disks) were made of the JT6500 brand name friction material. Each specimen was abraded over a distance of 4000 m. The mass losses, both of the specimens and of the counterface disks, were determined by weighting. It was found that the least wear among the examined materials was exhibited by the nodular cast iron. In turn, the smallest abrasion resistance was found in vermicular cast iron and in cast iron containing flake graphite coming from the brake disk. However, while the three types of specimens (those taken from the nodular cast iron and from grey cast iron coming either from the special casts or from the brake disk) have almost purely pearlitic matrix (P95/Fe05), the vermicular cast iron matrix was composed of pearlite and ferrite occurring in the amounts of about 50% each (P50/Fe50). Additionally, it was found that the highest temperature at the cast iron/counterface disk contact point was reached during the tests held for the nodular cast iron, while the lowest one occurred for the case of specially cast grey iron

Initial Assessment of Abrasive Wear Resistance of Austempered Cast Iron with Vermicular Graphite

The work compares the abrasive wear resistance of cast iron containing vermicular graphite, measured in the as-cast state and after austempering carried out at 290°C, 340°C, or 390°C. Theexaminations were performed by means of the T-01M tribological tester using the pin-on-disc configuration. Specimens used for examinations were taken from the end tabs of the tensile specimens, these being cut out of the test walls of the double-leg keel block test castings. Examinations proved that the austempering process increases the abrasive wear resistance of vermicular cast iron by several times as compared with the as-cast material. A tendency for a slight decrease in abrasive wear with an increase in austempering temperature can be stated. The coefficient of friction took a little higher values for cast iron after thermal treatment than for the as-cast material. The work was completed with roughness examination by means of electron scanning microscopy