With no carbon (or micro carbon) martensite as the matrix, aging can produce intermetallic compound precipitation hardening of ultra-high strength steel. Unlike traditional high-strength steel, it is strengthened by dispersion precipitation of intermetallic compounds without carbon. This makes it have some unique properties: high strength and toughness, low hardening index, good formability, simple heat treatment process, almost no deformation when aging, and good welding performance. Therefore, maraging steels have been widely used in sectors that require such characteristics. The simple heat treatment process is another important advantage of maraging steel. After hot working, the steel should be solid solution treated before cold working and aging strengthening. The purpose is to: dissolve the remaining precipitates after thermal processing, make the matrix dissolved with sufficient strengthening elements, and obtain a uniform high dislocation density of the whole martensite tissue. The solid solution temperature is usually 820~840 ℃, the solid solution time is 1h per 25ram thickness, air cooling after solid solution, and the cooling speed has little effect on the organization and performance. The high strength of maraging steel is obtained by aging treatment. Aging temperature is generally 480 ℃, high strength grade steel can be used 510 ¨ C, aging time is 3~6h, air cooling after aging. After aging, a large number of dispersed and ultra-microscopic intermetallic compound particles are precipitated on the martensite matrix, which doubles the strength of the material and reduces the loss of toughness.
The properties of maraging steels can also be improved by austenite deformation, or martensite deformation, or a combination of both. The austenite deformation treatment reduces the austenite grain size to less than 10um, thus obtaining a maraging steel with a certain ductility and strength greater than 3500MPa. The martensite deformation treatment after solid solution and before aging can usually increase the strength by 200MPa due to the generation of more dislocations. The martensite deformation before solid solution can refine the austenite grain and increase the strength of the steel after aging.