scholarly journals Determination of Eutectoid Transformation Temperatures in Ductile Cast Iron

2015 ◽  
Vol 15 (4) ◽  
pp. 51-54 ◽  
Author(s):  
A.W. Orłowicz ◽  
A. Trytek ◽  
M. Mróz ◽  
M. Tupaj
Keyword(s):  
Cast Iron ◽  
Cooling Rate ◽  
Ductile Cast Iron ◽  
Eutectoid Transformation ◽  
Heating Rates ◽  
Cooling Rates ◽  
Metallographic Examination ◽  
Transformation Temperatures ◽  
Rate Of Cooling

Abstract The paper proposes a methodology useful in verification of results of dilatometric tests aimed at determination of temperatures defining the start and the end of eutectoid transformation in the course of ductile cast iron cooling, based on quenching techniques and metallographic examination. For an industrial melt of ductile cast iron, the effect of the rate of cooling after austenitization at temperature 900°C carried out for 30 minutes on temperatures TAr1start and TAr1end was determined. The heating rates applied in the study were the same as the cooling rates and equaled 30, 60, 90, 150, and 300°C/h. It has been found that with increasing cooling rate, values of temperatures TAr1start and TAr1end decrease by several dozen degrees.

Influence of Cooling Rate and Alloying Elements on Kinetics of Eutectoid Transformation in Spheroidal Graphite Cast Iron

2010 ◽  
Vol 457 ◽  
pp. 163-168 ◽  
Author(s):  
Primož Mrvar ◽  
Mitja Petrič ◽  
Jožef Medved
Keyword(s):  
Cast Iron ◽  
Cooling Rate ◽  
Alloying Elements ◽  
Spheroidal Graphite ◽  
Eutectoid Transformation ◽  
Spheroidal Graphite Cast Iron ◽  
Graphite Cast Iron ◽  
Short Time ◽  
Kinetics Of

Paper deals with influence of cooling rate and alloying elements on kinetics of eutectoid transformation in spheroidal graphite cast iron (SGI). Transformation of austenite can proceed into ferrite and graphite (FeFeG) and/or in pearlite (Fe  FeFe3C). Examination of eutectoid transformation was made by evaluating the “in-situ” dilatation curves together with metallographic examinations, DTA, and dilatation analyses in solid state. ThermoCalc software was applied for thermodynamic calculations of phase equilibria. Based on numerous quantitative relations, such as relation between fractions of ferrite and pearlite in the as-cast SGI that was determined by analysis of dilatometric curves and taking into account also composition of melt, ferrite/pearlite ratio in the microstructure could be determined in a very short time. Thus the melt composition could be corrected by adding Cu and/or Mn or Si, respectively, using the "in situ" dilatation analyses. Characteristic temperatures of eutectoid transformation have been established from the kinetics of austenite transformation and from temperature dependence of ferrite and/or pearlite growth. Kinetics curves that enable to determine fractions of single microstructure constituents in the microstructure as function of transformation time, mainly used for ferrite and pearlite SGI, can be well determined with physical sigmoidal Boltzmann model.

scholarly journals Thermal stress, cooling-rate and fictive temperature of silicate melts

2021 ◽  
Vol 176 (10) ◽  
Author(s):  
Sharon L. Webb
Keyword(s):  
Heat Capacity ◽  
Cooling Rate ◽  
Heating Rate ◽  
Calibration Curve ◽  
Silicate Melts ◽  
Internal Stresses ◽  
Heating Rates ◽  
Fictive Temperature ◽  
Slow Cooling ◽  
Cooling Rates

AbstractThe unknown cooling-rate history of natural silicate melts can be investigated using differential scanning heat capacity measurements together with the limiting fictive temperature analysis calculation. There are a range of processes occurring during cooling and re-heating of natural samples which influence the calculation of the limiting fictive temperature and, therefore, the calculated cooling-rate of the sample. These processes occur at the extremes of slow cooling and fast quenching. The annealing of a sample at a temperature below the glass transition temperature upon cooling results in the subsequent determination of cooling-rates which are up to orders of magnitude too low. In contrast, the internal stresses associated with the faster cooling of obsidian in air result in an added exothermic signal in the heat capacity trace which results in an overestimation of cooling-rate. To calculate cooling-rate of glass using the fictive temperature method, it is necessary to create a calibration curve determined using known cooling- and heating-rates. The calculated unknown cooling-rate of the sample is affected by the magnitude of mismatch between the original cooling-rate and the laboratory heating-rate when using the matched cooling-/heating-rate method to derive a fictive temperature/cooling-rate calibration curve. Cooling-rates slower than the laboratory heating-rate will be overestimated, while cooling-rates faster than the laboratory heating-rate are underestimated. Each of these sources of error in the calculation of cooling-rate of glass materials—annealing, stress release and matched cooling/heating-rate calibration—can affect the calculated cooling-rate by factor of 10 or more.

scholarly journals Influence of nickel addition and casting modulus on the properties of hypo-eutectic ductile cast iron

2019 ◽  
Vol 55 (2) ◽  
pp. 283-293 ◽  
Author(s):  
E. Colin-García ◽  
A. Cruz-Ramírez ◽  
G. Reyes-Castellanos ◽  
J.A. Romero-Serrano ◽  
R.G. Sánchez-Alvarado ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Cast Iron ◽  
Cooling Rate ◽  
Ductile Iron ◽  
Ductile Cast Iron ◽  
Strength Ratio ◽  
Cast Irons ◽  
Microstructural Changes ◽  
Nodule Count ◽  
Nickel Addition

The effect of the casting modulus on the distribution and features of graphite in hypo-eutectic ductile iron unalloyed and alloyed with nickel (0.88 wt %) was studied. The cooling rate of the casting plates of 25.4, 12.7 and 8.5 mm in thickness with a casting modulus of 6.87, 4.46 and 3.31 mm, respectively promotes several microstructural changes, such as cementite precipitation and a noticeable nodule count increment. The nickel addition suppressed the cementite formation and improved the nodule count and nodularity for the three casting modulus evaluated. The nickel addition increased the nodule count in 69, 67 and 128 % for the modulus of 3.31, 4.46 and 6.87 mm, respectively, regarding the unalloyed ductile iron. It was found that the biggest casting modulus produced the biggest nodules with the lowest nodule count for both ductile cast irons. Further to the improvements in the graphite features, the nickel addition allowed to keep almost constant the yield and tensile strength ratio for the different casting modulus.

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