The Heat Treatment Parameters Analysis Using Two-Way ANOVA Method

Milosan Ioan
Analysis of variance (ANOVA) is the method used to compare continuous measurements to determine if the measurements are sampled from the same or different distributions. It is an analytical tool used to determine the significance of factors on measurements by looking at the relationship between a quantitative "response variable" and a proposed explanatory "factor". This method is similar to the process of comparing the statistical difference between two samples, in that it invokes the concept
more » ... vokes the concept of hypothesis testing. The two-way analysis of variance (Two-way ANOVA) is an extension to the one-way analysis of variance. The two-way ANOVA compares the mean differences between groups that have been split on two independent variables (called factors). A major importance represents the studies about the studies that analyze important technological parameters of heat treatment processes with Two-way ANOVA method. The paper presents an example of calculation for two-way analysis of variance repeated measures applied for the results of harness properties of an austempered ductile iron. The major objective of this research was to analyze (with Two-way ANOVA method) the influence of two independent variables on the dependent variable in the case of two alternatives of heat treatment. The independent variables are: the temperature at isothermal level, Tiz (in our case that has 2levels: Tiz= 300 and 400°C) and the maintained time at the isothermal level, tiz (that has four levels: tiz = 30; 60; 90 and 120 min). All calculations were made for two alternatives of austenizing temperatures of heat treatment: TA = 830 and 900°C. By studying all the data presented in this paper following remarkable conclusions: that the austenizing temperature, TA= 900 °C is an important variable for our heat treatment while the austenizing temperature, TA=830 °C is not an important factor for the values of hardness properties of the studied ductile cast iron.