Inventors:
Leslie L. Harner - Fleetwood PA
Earl L. Frantz - Reading PA
Assignee:
Carpenter Technology Corporation - Reading PA
International Classification:
C03C 2702
Abstract:
A thermally stable Super Invar has a substantially suppressed martensitic transformation inception point as well as an average coefficient of thermal expansion substantially lower than Invar. The composition in weight percent consists essentially of ______________________________________ w/o ______________________________________ C 0. 02 Max. Mn 0. 4-0. 8 Si up to 0. 25 Ni 32. 0-33. 2 Co 4. 5-5. 5 ______________________________________ and the balance iron except for incidental amounts of other elements including up to 0. 015 w/o P, 0. 015 w/o S, 0. 25 w/o Cr, 0. 20 w/o Mo, 0. 20 w/o. Cu, as well as other incidental elements in amounts which do not undesirably affect the austenitic microstructure or otherwise detract from the desired properties of the alloy. The composition is particularly suited for the manufacture of precision optical articles as well as other articles where minimal expansion mismatch between a metal member and a nonmetal member is required at temperatures of -90. degree. C. (-130. degree. F.