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The microstructures and precipitates in base metals and heat affected zones(HAZs)of two Zr-B microalloyed steels were characterized by means of optical microscopy(OM),transmission electron microscopy(TEM)and energy dispersive spectrum(EDS).It has been found that precipitates of tens of nanometers in size are present in the base metals of both steels.The average particle size,however,in the Zr-B steel with Ti is larger than that in the steel without Ti.After thermal simulations,in both cases,the MnS sulfides can nucleate on cubic(Nb,Ti)(C,N)carbonitrides and nearly spherical Zr-bearing compounds.The precipitates in the HAZs of both steels are coarser than those in the base metals,in the ranges of 150-200 nm and50-100 nm for Ti added and Ti-free steels, respectively.
The microstructures and precipitates in base metals and heat affected zones (HAZs) of two Zr-B microalloyed steels were characterized by means of optical microscopy (OM), transmission electron microscopy (TEM) and energy dispersive spectrum (EDS) .It has been found that precipitates of tens of nanometers in size are present in the base metals of both steels. average particle size, however, in the Zr-B steel with Ti is larger than that in the steel without Ti. After thermal simulations, in both cases , the MnS sulfides can nucleate on cubic (Nb, Ti) (C, N) carbonitrides and nearly spherical Zr-bearing compounds. The precipitates in the HAZs of both steels are coarser than those in the base metals, in the ranges of 150- 200 nm and 50-100 nm for Ti added and Ti-free steels, respectively.