Novel desulfurization process in vacuum induction melting process

Abstract

The invention discloses a novel desulfurization process in a vacuum induction melting process. According to the technical scheme, the method comprises the steps that an alloy material is dissolved and clarified, after the pressure of a furnace chamber is smaller than 10 Pa, the temperature of molten steel is increased to 60-150 DEG C above the alloy melting point for refining, and sampling is conducted every 10-30 min in the refining process till the content of oxygen and nitrogen in the molten steel is smaller than 20 ppm; then, the temperature of the molten steel is maintained to be 60-80 DEG C above the alloy melting point, after a furnace chamber is filled with argon to 10000 Pa, 0.5-5% of a Ca element additive is added into the molten steel, and the high binding force of the Ca element and the S element is utilized; the invention has the following beneficial effects: the desulfurization characteristics of Ca element and rare earth element are used; the sulfur element in the molten steel is removed in the mode that Ca is firstly used for desulfurization and then rare earth elements are used for desulfurization, and the content of the S element in the molten steel can be reduced to 10 ppm or below.

Description

Technical Field

[0001] The present invention relates to the technical field of vacuum induction melting, in particular to a new desulfurization process in a vacuum induction melting process. Background Art

[0002] Structural steel is widely used in building structures, mechanical structures, power structures, transportation structures and other fields due to its excellent mechanical properties and adaptability. S is the main impurity element in steel and seriously affects the mechanical properties of the alloy. Generally speaking, vacuum induction furnace melting is the first melting process of structural steel. It can melt the main metal materials of structural steel such as iron, nickel, and chromium into liquid. The S element in the liquid metal has a strong binding force with the more active Ca element and rare earth elements La or Ce. However, the saturated vapor pressure of Ca element is usually greater than the vacuum degree of the furnace chamber during the vacuum induction melting process, and the yield of the induction melting process is low. Rare earth elements La or Ce can also form rare earth sulfides with S in the molten steel, but their removal ability is limited. Summary of the Invention

[0003] The object of the present invention is to provide a new desulfurization process in a vacuum induction melting process to solve the problems raised in the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solution: a new desulfurization process in a vacuum induction melting process, comprising the following steps:

[0005] S1. First, dissolve the alloy material. After the furnace pressure is less than 10Pa, raise the temperature of the molten steel to above the melting point of the alloy (60-150)℃ for refining.

[0006] S2. Maintain the temperature of the molten steel at 60-80°C above the melting point of the alloy, fill the furnace chamber with argon to 10,000 Pa, add 0.5-5% of a Ca element additive to the molten steel, and maintain the molten steel temperature and furnace chamber pressure for more than 10 minutes after the Ca element additive is added to the molten steel;

[0007] S3. Add 0.1-1% rare earth elements to the molten steel, maintain the molten steel temperature above the alloy temperature (60-150)°C, evacuate the furnace until the pressure in the chamber is less than 10Pa, and then refine for more than 30 minutes to remove the residual Ca element in the molten steel by utilizing the higher saturated vapor pressure of the Ca element.

[0008] Preferably, during the refining process in S1, samples are taken every 10 to 30 minutes until the oxygen and nitrogen contents in the molten steel are less than 20 ppm.

[0009] Preferably, the strong binding force between the Ca element and the S element in S2 is used to achieve the purpose of desulfurization. According to the characteristics of the alloy, the Ca element additive can be nickel-calcium alloy, silicon-calcium alloy or metallic calcium.

[0010] Preferably, the rare earth element in S3 is La or Ce.

[0011] Compared with the prior art, the beneficial effects of the present invention are: relying on the desulfurization characteristics of Ca and rare earth elements; using the method of first desulfurizing with Ca and then desulfurizing with rare earth elements to remove sulfur in molten steel, the S element in the molten steel can be removed to below 10ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Schematic diagram of the method steps of the present invention. DETAILED DESCRIPTION

[0013] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0014] See also Figure 1 , the present invention provides a technical solution: Case 1: desulfurization process of HT700R alloy.

[0015] HT700R alloy contains high levels of Fe and Cr. Its additives are commercially pure iron and metallic chromium, respectively. These two additives contain high levels of S, totaling approximately 40 ppm. Without desulfurization, the alloy's mechanical properties are severely impacted. The melting point of HT700R alloy is 1370°C. Based on the alloy's smelting process, the desulfurization process is performed as follows.

[0016] First, dissolve the alloy material, and after the furnace pressure is less than 10Pa, refine the molten steel at a temperature of 1470-1480℃. Take samples every 10-30 minutes during the refining process until the oxygen and nitrogen content in the molten steel is less than 20ppm.

[0017] The molten steel temperature is maintained at (1430-1440)°C, and after the furnace chamber is filled with argon to 10,000 Pa, 0.6% of Ca element additive is added to the molten steel. The Ca element additive is a NiCa alloy. After the NiCa alloy is added to the molten steel, the molten steel temperature and furnace chamber pressure are maintained for more than 20-30 minutes.

[0018] 0.5% of the rare earth element La is added to the molten steel, the temperature of the molten steel is maintained at (1470-1480)°C, and the furnace chamber is evacuated to a pressure of less than 10Pa. The steel is then refined for more than 30 minutes. The higher saturated vapor pressure of the Ca element is utilized to remove the residual Ca element in the molten steel. At the same time, the S element in the molten steel can also be removed to below 10ppm.

[0019] Case 2: Desulfurization process of HT700P alloy.

[0020] HT700P alloy contains high levels of Fe and Cr. Its additives are commercially pure iron and metallic chromium, respectively. These two additives contain high levels of S, totaling approximately 40 ppm. Without desulfurization, the alloy's mechanical properties are severely impacted. The melting point of HT700P alloy is 1370°C. Based on the alloy's smelting process, the desulfurization process is performed as follows.

[0021] First, dissolve the alloy material, and after the furnace pressure is less than 10Pa, refine the molten steel at a temperature of 1470-1480℃. Take samples every 10-30 minutes during the refining process until the oxygen and nitrogen content in the molten steel is less than 20ppm.

[0022] The molten steel temperature is maintained at (1430-1440)°C, and after the furnace chamber is filled with argon to 10,000 Pa, 0.6% of Ca element additive is added to the molten steel. The Ca element additive is a NiCa alloy. After the NiCa alloy is added to the molten steel, the molten steel temperature and furnace chamber pressure are maintained for more than 20-30 minutes.

[0023] 0.5% of the rare earth element La is added to the molten steel, the temperature of the molten steel is maintained at (1470-1480)°C, and the furnace chamber is evacuated to a pressure of less than 10Pa. The steel is then refined for more than 30 minutes. The higher saturated vapor pressure of the Ca element is utilized to remove the residual Ca element in the molten steel. At the same time, the S element in the molten steel can also be removed to below 10ppm.

[0024] Case 3: Desulfurization process of HT700T alloy.

[0025] HT700T alloy contains high levels of Fe and Cr. Its additives are commercially pure iron and metallic chromium, respectively. These two additives contain high levels of S, totaling approximately 40 ppm. Without desulfurization, the alloy's mechanical properties are severely impacted. The melting point of HT700T alloy is 1370°C. Based on the alloy's smelting process, the desulfurization process is performed as follows.

[0026] First, dissolve the alloy material, and after the furnace pressure is less than 10Pa, refine the molten steel at a temperature of 1470-1480℃. Take samples every 10-30 minutes during the refining process until the oxygen and nitrogen content in the molten steel is less than 20ppm.

[0027] The molten steel temperature is maintained at (1430-1440)°C, and after the furnace chamber is filled with argon to 10,000 Pa, 0.6% of Ca element additive is added to the molten steel. The Ca element additive is a SiCa alloy. After the SiCa alloy is added to the molten steel, the molten steel temperature and furnace chamber pressure are maintained for more than 20-30 minutes.

[0028] 0.5% rare earth element Ce is added to the molten steel, the molten steel temperature is maintained at (1470-1480)°C, and the furnace pressure is evacuated to less than 10Pa. The steel is then refined for more than 30 minutes. The higher saturated vapor pressure of the Ca element is utilized to remove the residual Ca element in the molten steel. At the same time, the S element in the molten steel can also be removed to below 10ppm.

[0029] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A new desulfurization process in vacuum induction melting, characterized by: The following steps are involved: S1. First, dissolve the alloy material. After the furnace pressure is less than 10Pa, raise the temperature of the molten steel to above the melting point of the alloy (60-150)℃ for refining. S2. Maintain the temperature of the molten steel at 60-80°C above the melting point of the alloy, fill the furnace chamber with argon to 10,000 Pa, add 0.5-5% of a Ca element additive to the molten steel, and maintain the molten steel temperature and furnace chamber pressure for more than 10 minutes after the Ca element additive is added to the molten steel; S3. Add 0.1-1% rare earth elements to the molten steel, maintain the molten steel temperature above the alloy temperature (60-150)°C, evacuate the furnace until the pressure in the chamber is less than 10Pa, and then refine for more than 30 minutes to remove the residual Ca element in the molten steel by utilizing the higher saturated vapor pressure of the Ca element.

2. A new desulfurization process in a vacuum induction melting process according to claim 1, characterized in that: During the refining process in S1, samples are taken every 10 to 30 minutes until the oxygen and nitrogen contents in the molten steel are less than 20 ppm.

3. A new desulfurization process in a vacuum induction melting process according to claim 1, characterized in that: The S2 utilizes the strong binding force between the Ca element and the S element to achieve the purpose of desulfurization. According to the characteristics of the alloy, the Ca element additive can be nickel-calcium alloy, silicon-calcium alloy or metallic calcium.

4. A new desulfurization process in a vacuum induction melting process according to claim 1, characterized in that: The rare earth element in S3 is La or Ce.

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