Metallurgical V-N microalloying and compound deoxidation cored wire

Abstract

A metallurgical V-N microalloying and compound deoxidation cored wire contains a core wire and a cladding steel belt. The technical key point of the cored wire is as follows: the core wire of the cored wire consists of a vanadium-increasing agent, a nitrogen-increasing agent and a deoxidizing nitrogen-fixing agent of which particle sizes are less than 6mm, wherein the vanadium-increasing agent is ferrovanadium, nitrided ferrovanadium or vanadium pentoxide; the nitrogen-increasing agent is ferrosilicon nitride, silicomanganese nitride, ferromanganese nitride, ferrochromium nitride, silicon nitride, aluminum nitride or calcium cyanamide; and the deoxidizing nitrogen-fixing agent contains one or more of aluminum, calcium, magnesium and barium, and can also contain one or more of titanium, zirconium, niobium, manganese, chromium, silicon, carbon and iron. By adopting the cored wire, the V / N ratio of steel can get closer to the optimal proportion, the enhancing function of vanadium can be utilized furthest, vanadium resources can be saved, the recovery rate of nitrogen is high, the nitrogen content is stable, the compound deoxidation function can also be realized, the V-N microalloying cost can be reduced and the quality of steel can be increased.

Description

technical field [0001] The invention relates to the technical field of iron and steel metallurgy, in particular to a cored wire for metallurgy with vanadium nitrogen microalloying and composite deoxidation. Background technique [0002] Microalloying of vanadium and nitrogen is the main method for producing low-alloy high-strength steels such as rebars above HRB400. Adding nitrogen to vanadium-containing steel can form vanadium carbide or nitride in the steel. Through its dual effects of precipitation strengthening and grain refinement, the yield strength of the steel can be greatly improved, and the steel has good properties. plasticity, toughness and weldability. [0003] When microalloying steel with vanadium and nitrogen, the ratio of the vanadium content to the nitrogen content in the steel (referred to as the vanadium-nitrogen ratio V / N) has a great influence on the properties of the steel. In the case of constant vanadium content in steel, with the increase of nitro...

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Problems solved by technology

Its disadvantage is that the V / N ratio is too high; the second is that the vanadium-nitrogen alloy has a low density. After adding the block vanadium-nitrogen alloy to the molten steel, it will float on the top of the molten steel, causing part of the vanadium-nitrogen alloy to burn, and the loss of vanadium and nitrogen. The recovery rate is relatively low, especially the recovery rate of nitrogen is only 40% to 50%, which is much lower than the 80% recovery rate of vanadium, which further increases the V / N ratio in steel

Chinese patent CN1818086A proposes a patent for making a vanadium-nitrogen alloy powder into a cored wire. Although this method can improve the recovery rate of the vanadium-nitrogen alloy, the cored wire of this patent only contains vanadium-nitrogen alloy and a small amount of niobium-titanium alloy , no nitrogen-rich alloy is added, therefore, when microalloying molten steel using the cored wire described in this patent, if the nitrogen content in the steel is to be increased, the vanadium content must be increased at the same time, and the V / N ratio in the steel cannot be adjusted To the optimal ratio, the utilization rate of vanadium is still relatively low

There are three problems in this addition method. One is that the density of the block nitrogen-enriched alloy is low, even lower than that of the slag. After being added to molten steel, it will float on the steel slag, causing part of the alloy to be burned; the other is that the nitrogen-enriched alloy It has high melting point, poor thermal conductivity, and does not infiltrate with molten steel. After being added to molten steel, the melting speed of block alloy in molten steel is very slow. It is difficult to disperse nitrogen-rich alloy into molten steel only by the impact and stirring of molten steel during tapping. The third is that the deoxidation of molten steel is not complete during tapping, and the oxygen content is high, and the oxide film is easy to form on the surface of the block alloy, which further reduces the solubility and diffusion speed of nitrogen in molten steel; these three defects cause nitrogen-rich alloys Most of the nitrogen becomes nitrogen bubbles emerging from the molten steel, it is difficult to dissolve in the molten steel, resulting in a low recovery rate of nitrogen, and it is unstable, generally fluctuating between 20% and 50%.

Therefore, the use of nitrogen-rich alloys is relatively large, and the cost of increasing nitrogen is relatively high.

At the same time, the unstable nitrogen content in the steel will cause large fluctuations in the yield strength of the finished steel, making it difficult to control the quality of the steel.

This is especially unfavorable for the production of seismic steel bars