RESEARCH ON SECONDARY PHASE PARTICLES IN Ti MICROALLOYED STEEL AND HEAT-AFFECTED ZONE

The secondary phase particles in Ti microalloyed steel and heat-affected zone are investigated through the extraction replica and metal film electron microscopic analysis.It is concluded that main particles in Ti microlloyed steel and its heat-affect zone are TiN as well as little AlN.Crystal grain sizes are increased obviously and the quantity is reduced after thermal circulation.In comparison to steels with high Ti and N contents,the quantity of TiN particles in the steel with low Ti/N contents is more than those and grain size is less.During thermal circulation the low dissolving capacity and coarsing of TiN particles appear,which has widely hindered action on grain growth of original austenite.