AOD Furnace Process Technology Description

AOD refining method is the abbreviation of argon oxygen decarburization. When refining stainless steel, it is to blow oxygen into the molten steel at standard atmospheric pressure while blowing inert gas (Ar, N2), by reducing the CO partial pressure, to achieve the effect of false vacuum, so that the carbon content is reduced to a very low level, and inhibit the oxidation of chromium in the steel.

AOD furnace method (i.e. argon oxygen decarburization method) is a more advanced technology for refining stainless steel. It has the advantages of simple equipment, convenient operation, strong adaptability, low investment, and low production cost, and is widely used.

The molten iron from the blast furnace and the alloy melted in the medium frequency furnace are injected into the AOD furnace through the ladle. During smelting, O2, Ar or N2 mixed gas is blown into the molten steel to decarburize the molten steel. At the same time, reducing agents, desulfurizers, ferroalloys or coolants are added from the feeding system to adjust the composition and temperature of the molten steel, and qualified stainless steel water is smelted for continuous casting.

The transportation and regulation of mixed gas during refining is one of the main systems of the argon oxygen furnace. The gas produced by the oxygen production workshop is transported to the gas storage tank near the workshop through pipelines, and finally the mixed gas is sent into the furnace through the side gun according to the flow rate and proportion required by the process.

At the beginning of smelting, oxygen is blown into the metal molten pool from the top furnace mouth through a double-layer water-cooled oxygen blowing pipe for decarburization. During refining, the mixed gas is sent into the furnace through the side gun (installed on the side wall opposite to the steel outlet and close to the bottom of the furnace).

When charging and tapping, the furnace body tilts forward at a certain angle, and the (side) tuyere is above the steel liquid level. During normal blowing, the tuyere sinks into the deep part of the molten pool. The central tube of the tuyere blows a mixed gas of oxygen and argon or nitrogen. By adjusting the oxygen-argon ratio, the partial pressure of carbon monoxide can be reduced to achieve the purpose of decarburization and chromium preservation. The type of the AOD furnace tuyere is unique. It is a consumable tuyere cooled by gas.

The tuyere adopts a double-layer sleeve structure. The outer tube only passes argon or nitrogen to cool the tuyere, and the inner tube passes a mixed gas of oxygen and nitrogen or argon.

The flow rate of the tuyere mask ring is controlled to achieve the best operating effect. The flow rate of the central tube of the tuyere mask ring and the tuyere mask ring can be controlled in the main control room.

The three-side gun technology is adopted. It can enhance the oxygen supply intensity and improve the metal material recovery rate. This technology can shorten the AOD smelting time.

A stable and reliable control system can reduce the consumption of gas and various raw materials during smelting and obtain stable product quality.

 

AOD furnaces are mostly used in conjunction with EAF furnaces for dual production. The electric furnace only needs to melt the prepared metal materials and low-phosphorus, high-medium carbon ferrochrome. The molten steel is poured into the AOD furnace through the intermediate ladle for decarburization and refining.

Stainless steel is usually smelted by two-stage blowing. The total amount of oxygen blowing required is calculated based on the C, Si, Mn content in the steel and the weight of the molten steel, and the blowing time for each stage is preliminarily calculated. Different proportions of nitrogen and oxygen mixed gases are blown into the molten steel according to the different carbon and chromium content and temperature in each stage for decarburization refining.