Progress of stainless steel smelting process technology in China

At present, China is a large country in the production and consumption of stainless steel. There are many types of stainless steel and different smelting process routes have been formed according to the use of steel types and raw materials. In recent years, China’s stainless steel smelting technology has developed in the direction of improving productivity, simplifying processes, reducing production costs and improving the quality of molten steel and has continuously optimized raw materials and process equipment.

The summary is divided into three smelting processes
At present, the smelting process for producing stainless steel in the world is mainly divided into one-step method, two-step method and three-step method. Among them, the two-step process of EAF + AOD (arc furnace + argon oxygen refining furnace) accounts for about 70%, and the three-step process 20%. As low-phosphorus molten iron is widely used in stainless steel production, the new one-step stainless steel smelting process is also being adopted by more and more stainless steel production enterprises.

One-step stainless steel smelting process
The early one-step stainless steel smelting process refers to the process of melting, decarburizing, reducing and refining scrap steel in an electric furnace, and smelting the charge into stainless steel in one step. With the continuous development of the refining process, this one-step smelting production process using only an electric furnace to smelt stainless steel is gradually phased out due to the long smelting cycle, low operating rate and high production cost.
By continuously modifying the use of low-phosphorus or dephosphorized molten iron instead of scrap steel, a new one-step smelting process has been formed. Compared with before one is to reduce investment. The other is to reduce production costs. The third is to reduce the cost of ingredients, reduce energy consumption and improve the purity of molten steel. It is especially economical for smelting 400 series stainless steel.

Two-step stainless steel smelting process
The representative process route of two-step stainless steel is EAF → AOD, EAF → VOD (arc furnace → VOD vacuum refining furnace). The capacity of the EAF → AOD process currently accounts for about 70% of the world’s stainless steel capacity. The EAF furnace is mainly used to melt scrap steel and alloy raw materials to produce stainless steel pre-melts. The stainless steel pre-melts enter the AOD furnace to smelt into qualified stainless steel molten steel.
The two-step stainless steel smelting process is widely used in the production of various series of stainless steels. Its advantages include electric furnaces do not require high raw materials, the production cycle is slightly shorter than the one-step process, and they have good flexibility 95% of stainless steel varieties.

Three-step stainless steel smelting process
The basic process of the three-step method is primary refining furnace → double-blown converter / AOD furnace → vacuum refining device. The three-step method is an advanced method for smelting stainless steel. The quality of the product is good, and it is suitable for specialized manufacturers and also for stainless steel production in United Iron and Steel Enterprises.
The three-step method of stainless steel is based on the two-step method, which adds a step of deep decarburization. The advantages of the smelting process. The first, the division of labor in each step is clear, the production rhythm is fast, and the operation is optimized. The second is the high product quality. The content of nitrogen, hydrogen, oxygen and inclusions is low and a wide range of varieties can be produced. Third, molten iron can be used and the requirements for raw materials are not high, and the choice of raw materials is flexible.