Investigation Of Microstructure In X80Pipeline Steel Refined By Adding Nano-oxides

As important steel materials, the pipeline steel is widely applied in economic construction. However the problem of pipeline steel welding heat affected zone (HAZ) grain coarsening is the key that restricts the effective use of high grade pipeline steel. The present research aims to curb the high level pipeline steel welding heat affected zone (HAZ) grain coarsening tendency. The experimental investigation has been carried out.To improve the nano-ceramic particles pre-dispersion state, the nano-MgO particles are adopted as raw materials. Meanwhile, micron Fe powder and micron Mo powder are used as the carrier powder, and carried out process of pre-dispersd forming on the mixing nano-ceramic which is mixed by the way of manual and mechanical methods. Measure and calculate the dispersing situation of nano-MgO particles in the Fe Mo matrix,particle size,actual density and relative density of sintering specimen which are prepared under the conditions of different sintering temperature and different quality mixture ratio.And then obtain all kinds of data of the sintering sample through optical microscope and electron microscopic.The experimental results show that with the increase of the amount of carrier particles,the scattered size of the nano-MgO particles in Fe Mo matrix have significantly reduced, and the distribution is more uniformly.Under the condition in which nano-MgO particles and carrier powder particles mixing proportional is1:48,and sintering temperature is1050℃, the conglobatus of nano-MgO particles whose size are under1μm are increased obviously in Fe, Mo matrix.The X80pipeline steel is used for experimental material. Experiments are carried out in the way of adding the mixture of nano-Ti2O3particles and carrier powder prepared by the cold-pressing shaping method into the X80pipeline steel liquid, and then analyzing the microstructure and inclusions of X80pipeline steel which is added nano-Ti2O3particles with different amount and methods through the optical microscope and electron microscope. It is found that when adopting to the metheod of adding nano-ceramic particles with the steel material, X80pipe steel as-cast structure is refinement with the increasing amount of adding nano-Ti2O3powder particles.But under the the same amount of nano-Ti2O3particles,adopting to the method of adding the nano-ceramic particles when the liquid steel is melt completely grain refinement effect of the X80pipeline steel is better than the method of adding the nano-ceramic particles with the steel.When using the method of adding the nano-ceramic particles with the steel and the amount of adding nano-Ti2O3particles is0.01%the X80pipe steel as-cast structure is refined1.87times compared with not adding nano-Ti2O3particles. It is found that inclusions are most consist of multi-element compositing compound through composition analyzing the element of the inclusions in the X80pipeline steel after the melting.