Estudo da variação da concentração do elemento químico Boro em amostragens no aço

Abstract

During the steel plate manufacturing by continuous ingot casting, a sample is realized to certificate the chemical composition. For the plates produced by continuous ingot casting that for any reason did not have the analyses result sample or to confirm the sample result, there is another sample provided from a metal piece cut off from the plate corner. This kind of sampling is also realized at the steel plate world marketing, and it is increasing along the world. However, it is noted a difference between the analyze results of the Boron element for certain interval concentration when the analyses are made by optical spectrometry emission – Spark, which have different results for ingot casting, plate corner and final rolled product. This difference may cause issues as questionings or even refuse of the plate chemical composition by the client with the producer. During the work development it was observed that the behavior of boron in the solidification of the plate differs from the other elements showing a high relative error compared to the sampling realized during the plate production. While the other steel elements had mostly relative error below 10%, boron had a relative error of 39.4 Due the partition coefficient (k) of boron is much lower than 1 (k <1), there is a high segregation tendency, with solute rejection to the liquid, the boron concentration being lower in the first solidifying regions (closest to the mold) and higher in the last solidifying portion. The major objective of the study is to verify the dispersion of Boron at the steel plate produced by continuous ingot casting and identify the plate regions which better represent the result expected of Boron in the steel.