Fine Carbonitride Particles Research Articles

A New Type of Submerged-Arc Flux-Cored Wire Used for Hardfacing Continuous Casting Rolls

It is expected that the welding hardfacing of continuous casting rolls has better welding performance and higher wear resistance. A new type of submerged-arc hardfacing flux-cored wire has been developed through nitrogen replacing part of carbon and addition of the nitrogen-fixing elements of niobium and titanium. And microstructure, degree of hardness and high-temperature wear resistance of its deposited metal samples were also investigated. It is found that the microstructure is martensite, residual austenite and carbonitride precipitates. As a result, the hardfacing metal with homogeneous distribution of very fine carbonitride particles had high hardness and excellent wear-resisting property during high-temperature wear, which could significantly extend the service life of continuous casting rolls.

Effect of carbonitride precipitates on the abrasive wear behaviour of hardfacing alloy

Hardfacing alloy of martensitic stainless steel expect higher abradability to be achieved through the addition of nitrogen being provided by the fine scale precipitation of complex carbonitride particles. Niobium and titanium as the most effective carbonitride alloying elements were added in the Fe–Cr13–Mn–N hardfacing alloy to get carbonitride precipitates. Carbonitride was systematically studied by optical microscopy, scanning electronic microscopy and energy spectrum analysis. Abrasive wear resistance of hardfacing alloy in as-welded and heat-treated conditions was tested by using the belt abrasion test apparatus where the samples slide against the abrasive belt. It is found that carbonitride particles in the hardfacing alloy are complex of Cr, Ti and Nb distributing on the grain boundary or matrix of the hardfacing alloy with different number and size in as-welded and heat-treated conditions. A large number of carbonitrides can be precipitated with very fine size (nanoscale) after heat treatment. As a result, the homogeneous distribution of very fine carbonitride particles can significantly improve the grain-abrasion wear-resisting property of the hardfacing alloy, and the mass loss is plastic deformation with minimum depth of grooving by abrasive particles and fine delamination.

Detection of interphase precipitation in microalloyed steels by microhardness measurements

Interphase precipitation of fine carbonitride particles during the austenite-to-ferrite phase transformation is generally recognized as an important mechanism for the strengthening of hot-rolled microalloyed steels [1]. Very high precipitation hardening contributions have in fact been reported for Ti and Nb microalloyed steels under experimental processing conditions [2,3]. In commercial microalloyed steels, which are hot-rolled under industrial conditions, however, the role of interphase precipitation is not well understood because it has long been known to occur in only some of the ferrite grains and not in others [4]. Although the reasons for such a selective behaviour remain unknown, there is a definite lack of more quantitative information about this precipitation mode because

Quantitative study of carbonitride precipitation in niobium and titanium microalloyed hot strip steel

A commercial microalloyed steel was examined by optical and transmission electron microscopy in order to determine the origin and the amount of carbonitride precipitation which had formed as the result of industrial processing on a hot strip mill. Almost one-half of the total microalloy addition (0.06Ti and 0.02 Nb) had remained in the form of eutectic or undissolved particles after soaking. Intragranular nucleation of fine carbonitride particles was observed to have occurred only in austenite. No additional carbonitride particles had formed in ferrite during coiling and almost one-half of the microalloying elements dissolved during soaking had remained in solution at the end of the industrial rolling process. According to well established structure-propertyrelationships, a precipitation strengthening potential of 60-80 MN m−2 could be assigned to thecarbonitride particles whichhad nucleated in austenite.