Method for modifying carbide of austenitic heat-resistant steel

Abstract

The invention discloses a method for modifying carbide of austenitic heat-resistant steel. The method for modifying the carbide of the austenitic heat-resistant steel comprises the following steps that electric furnace smelting, AOD furnace smelting, LF furnace refining, nickel-magnesium cored wire feeding, continuous casting or die casting, blooming cogging or die casting, rolling, full solid solution and aging solid solution are sequentially carried out on magnesium-containing austenitic heat-resistant steel raw materials to obtain the modified austenitic heat-resistant steel, wherein in the final stage of LF furnace refining, a nickel-magnesium cored wire is fed, and the nickel-magnesium cored wire comprises, by mass, 7%-25% of Mg, 5%-45% of Ni, 20%-40% of Cr, 0.1%-5.5% of N and the balance Fe and inevitable impurity elements. According to the method for modifying the austenitic heat-resistant steel, the wire feeding process is stable, the reaction is smooth, violent splashing is avoided, the yield of the magnesium element is high and reaches 20%-35%, and the production cost is low.

Description

technical field [0001] The invention relates to the technical field of iron and steel metallurgy, in particular to a method for modifying carbides of austenitic heat-resistant steel. Background technique [0002] Austenitic heat-resistant steel is widely used in metallurgy, mining, petrochemical, electric power and other industrial production, for the preparation of dry quenching coke oven lining, thermal power plant boiler burner nozzle, circulating fluidized bed boiler hood, cyclone Heat-resistant components such as tube inner tube hanging piece. High-temperature stability and high-temperature strength are two major performance indicators of heat-resistant steel, and they are also important research topics in engineering applications of heat-resistant steel. [0003] 21-4N steel is a typical heat-resistant steel commonly used for exhaust valves at home and abroad, also known as valve steel, and its composition is: C 0.48-0.58%, Si<0.35%, Mn 8.00-10.00%, P<0.04%, S&...

AI Technical Summary

Problems solved by technology

Ribbon carbides and network carbides are essentially carbides precipitated from austenite, so they are also collectively referred to as secondary carbides. The existence of secondary carbides weakens the bonding force between metals, making the steel The mechanical properties are reduced, especially the impact toughness is reduced, and it is easy to cause grain boundary cracking and reduce the wear resistance of steel

[0006] In order to improve the distribution of carbides in the steel, reduce the proportion of carbides, especially the proportion of reticular carbides, and improve the performance of austenitic valve steel, rare earth and other elements can be added to the steel to form carbides. regulation, but the cost of rare earth is high, the detection is complicated, and the pouring process is easy to accumulate tumors at the nozzle

[0007] Since the melting point of magnesium is 649°C, the boiling point is 1090°C, and the vapor pressure is 2.038MPa at 1600°C, that is, the vapor pressure is more than 20 atmospheres, the boiling point of magnesium is relatively low, so magnesium cored wire is added during the process of adding molten steel. During the process, it will volatilize and lead to low yield; on the other hand, when the oxygen level of molten steel is high, deoxidation reaction will occur when feeding magnesium cored wire, which will also cause a significant decrease in yield, severe splashing and violent reaction during the process The problem

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