ANALYSIS MICROCHEMICAL

Author: BOTELLA RUEDA VICENTE.
Year: 2004.
University: MÁLAGA [www.uma.es].
Place of defense: FACULTAD.
Place of preparation: FACULTAD DE CIENCIAS DE MÁLAGA.

Summary: Within the field of austenitic stainless steel, niobium is described as an element alfágeno or advocate for the formation of ferrite: trente a number of other elements (carbon, nitrogen, nickel, etc.). To be garnmágenos or promoters for training austenite. However, the authors do not agree on the value of coefficient alfágeno (ie the power ferrite trainer of this element of taking chromium as a reference) assignable to this element. One factor that has not been taken into account is that the effect of niobium, as a alfágeno only is attributable to the parties soluble total content of this element in stainless steel, deducting that part of the total, to form inclusions precipitates or highly stable (NbC, NbN, etc..) does not dissolve in steel during solidification or during heat treatment and, therefore, may not be available for the balance of phases austenita-ferrita. We have developed several series bullion austenitic stainless steels most commonly used alloy with different percentages of niobium. The quantities of niobium added, in many cases, have exceeded the values of concentration of this element in the samples certified patterns in the market and that can be used to obtain the calibration curves of analytical systems (especially ray fluorescence spectrometers X) for analysis via dry samples massive stainless steel. It has become necessary, therefore, together with the manufacture of ingots, the use of analytical techniques (additional emission spectrometry with source excitation coupled plasma induction -ICP- lnductivily Coupled Plasma-) for the analytical characterization of a niobium controlled degree of accuracy has been studied the relationship between the content of niobium, and the percentage of ferrite measured. We have characterized quantitatively and qualitatively non-metallic inclusions, and precipitated phases present in the metal ingots, through techniques metalografia quantitatively using scanning electron microscopy. Thus, it has been possible to calculate what: pull of the elements are in precipitates and / or solubilized, allowing to determine the actual content of soluble niobium. It has discussed ways in which the niobium is shared by the various phases and precipitates and has been observed their behavior alfágeno, considering only the portion solubilizada.