Two-step method In 1965 and 1968, VOD and AOD refining devices were successively produced, which played a decisive role in the transformation of stainless steel production process. The former is decarburization by vacuum blowing oxygen, and the latter is decarburization with argon and nitrogen dilution gas. Combining either of these two refining facilities with an electric furnace creates a two-step production process for stainless steel.
The electric furnace and VOD two-step steelmaking process is more suitable for the production of stainless steel in small-scale and multi-variety compatible factories.
Using the two-step steelmaking process of electric furnace and AOD to produce stainless steel has the following advantages:
1. The AOD production process has low requirements on raw materials, and the carbon content of electric furnace tapping can reach about 2%, so cheap high-carbon FeCr and 20% stainless steel scrap can be used as raw materials, reducing operating costs.
2. The AOD method can remove 0.08% of the carbon in the molten steel in one step. If the smelting time is prolonged and the amount of Ar is increased, the carbon in the molten steel can be further removed to below 0.03%, except for ultra-low carbon. Except for ultra-low nitrogen stainless steel, 95% of the varieties can be produced.
3 The production cycle of stainless steel is shorter than that of VOD, and the flexibility is better.
4. The total investment of production system equipment is more expensive than VOD, but less than the three-step method.
5. The AOD furnace produces steel in one step, with less personnel and equipment, so the overall cost is lower.
6. AOD can use primary molten steel containing less than 1.5% C, so it can use low-priced high-carbon FeCr, FeNi40 and 35% carbon steel scrap for batching, and the cost of raw materials is low.