Tecnologia em Metalurgia, Materiais e Mineração
https://tecnologiammm.com.br/article/doi/10.4322/tmm.2011.035
Tecnologia em Metalurgia, Materiais e Mineração
Artigo Original

ADEQUAÇÃO DA COMPOSIÇÃO QUÍMICA E DO TRATAMENTO TÉRMICO DE FERROS FUNDIDOS DE ALTO CROMO UTILIZANDO TERMODINÂMICA COMPUTACIONAL

OPTIMIZING HEAT TREATMENT OF HIGH CHROMIUM CAST IRONS USING COMPUTATIONAL THERMODYNAMICS

Albertin, Eduardo; Beneduce Neto, Flavio; Teixeira, Ivênio de Oliveira

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Resumo

O objetivo do presente trabalho é a aplicação dos recursos de termodinâmica computacional para a otimização dos tratamentos térmicos dos ferros fundidos de alto cromo. Apresentam-se as características das ligas comerciais baseadas no sistema Fe-Cr-C e as etapas de aplicação da termodinâmica computacional para auxiliar na previsão das microestruturas e propriedades que podem ser obtidas em função das composições químicas e tratamentos térmicos das ligas. São apresentados os resultados de dois casos práticos. Foi desenvolvida uma liga com 31%Cr e adição de nitrogênio, combinando resistência ao desgaste e à corrosão, graças à obtenção de uma matriz martensítica com dureza acima de 700 HV, contendo mais de 14% de cromo dissolvido. Para obter resistência ao desgaste e a impactos foi desenvolvida uma liga com 17%Cr com adição de 1,5%Mo. A análise por termodinâmica computacional permite prever a composição química da liga e o tratamento térmico necessários para atingir 0,8%Mo dissolvido na austenita antes da têmpera, o que favorece a obtenção de dureza secundária durante o tratamento de revenimento.

Palavras-chave

Ferro fundido alto cromo, Termodinâmica computacional

Abstract

A methodology for using computational thermodynamics to optimize heat treatments of high chromium cast irons is presented. The main characteristics of the commercial alloys based on the Fe-Cr-C system are discussed, together with the steps to be applied using computational thermodynamics to preview microstructures and properties that can be achieved, resulting from different alloy compositions and heat treatments. The results of application of the method for two practical cases are presented. A 31%Cr alloy (all percentages are by mass, unless otherwise stated), with nitrogen addition, was developed to resist to abrasion and corrosion, a result obtained thanks to a martensitic matrix with hardness over 700 HV, containing over 14% dissolved chromium. An abrasion and impact resistant alloy was developed using computational thermodynamics to establish the chemical composition and heat treatment to obtain 0.8%Mo dissolved in the austenite previously to the quenching treatment, leading to secondary hardening during tempering.

Keywords

High chromium cast iron, Computational thermodynamics

Referências

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