G. Totten, Portland State University, Portland, OR; L. C. Casteletti, A. Lombardi Neto, Escola de Engenharia de São Carlos –USP-São Carlos –SP-Brazil, Sao Carlos, SP, Brazil
In this work [11] an alloy with 31% Mn, 7,5% Al, 1,3% Si, 0,9% C and bal Fe was produced and evaluated for tensile strength and formability oxidation resistance. The average tensile strength was 756 Mpa with an elongation of 55%. In oxidation resistance tests at 700 0C evaluating mass gain, the alloy exhibited behavior similar to the AISI 304 austenitic stainless steels. At 800 0C the oxidation resistance is somewhat inferior to 304 steel but the oxide layer stabilizes after 40 h of testing. The alloy demonstrated high cold conformability, allowing the manufacture of wires with sections of 2 mm x 2 mm by cold rolling starting with square sections of 10 mm and without the use of intermediate annealing .
The alloys used in the manufacture of heating elements can be divided in two groups: the cooper based alloys and the Fe – Ni – Cr alloys. Cooper alloys goes up to 300 0C and Fe – Ni – Cr alloys up to 1350 0C. This leaves a window from 300 to 800 0C were expensive Fe – Ni – Cr alloys are being used in temperatures well bellow their capabilities.
The characteristics of cold conformability, oxidation resistance up to 800 0C and the absence of an optimal alloys for this range of temperatures suggested the possibility of using this Fe based alloy for heating elements. To explore this possibility, tests to determine the electrical properties of this alloy were performed.
The obtained results were similar to that presented by the Kanthal alloy, indicating the possibility of using the developed alloy for electric resistances.
