Ti (CN) Precipitation in Ultra-High Strength Ti Micro-Alloyed Steels with 700MPa Yield Strength on TSCR Process

Abstract

Precipitates in ultra-high strength Ti micro-alloyed strips with 700MPa yield strength on TSCR process and in the thermal simulation experimental specimen are observed via Scanning Electronic Microscope (SEM) and Transmission Electron Microscope (TEM), the results show that: the precipitates in the Ti micro-alloyed cast slab thermal simulation experiment can be divided into three categories: 1) micron-sized liquation TiN, 2) 100-200nm sized TiC formed along original austenite grain boundaries or along the dendrite segregation band, 3) solid precipitated 50-100nm sized TiN. Deformation induced spherical TiC (about 10nm-30nm) homogeneously distributed in the matrix after the austenite deformation .After simulated coiling, dispersed TiC (about 5-15nm ) precipitated from ferrite are found in the specimen. TiN with hundreds of nanometers size are commonly found in Ti micro-alloyed strips in industrial production. Ti4C2S2and Ti (CN) are complex precipitated, Ti4C2S2size is less than 30nm; physical and chemical phase analysis shows that the nanosized TiC precipitates are characterized by high volume fraction and small dimensions.