Patent Application
20240150860
The present invention relates to the technical field of ferrous metallurgy, and in particular to a process for smelting high-speed steel by using an intermediate frequency furnace-LF furnace-VD.
An electric arc furnace-LF furnace (ladle refining furnace)-VD (vacuum degassing) process is the mainstream process for smelting high-speed steel at present. This process takes an electric arc furnace as a rough smelting furnace that has the main functions of melting raw materials, heating, dephosphorizing, and the like. To ensure the cleanliness of steel, slagging-off is performed after the smelting is completed in the electric arc furnace, slag materials such as lime and the like are added when molten steel is poured into a steel ladle, the steel and the slag materials are mixed to help to slag, and then the steel and the slag materials are transferred to an LF furnace station for refining. The LF furnace has the main functions of deoxidation, accurate adjustment of chemical components of steel, and temperature adjustment, and the VD furnace has the functions of vacuum degassing and H, N, O removal in molten steel, so that the cleanliness of the molten steel is further improved.
However, this process has some defects in practical production. Firstly, a recovery rate of the alloy by using the electric arc furnace smelting is not ideal, and the electric arc furnace smelting is not suitable for smelting high alloy steel; secondly, for helping to slag, the electric arc furnace needs to increase the steel-tapping temperature and prolong the smelting time, which is not beneficial to energy conservation and consumption reduction; and the carbon-oxygen deposit in the molten steel is increased when the temperature is high, resulting in higher oxygen content in the molten steel, which increases the deoxidation burden of the rear process; thirdly, this process has a poor slagging effect, and low-current transmission for slagging is performed specially after the LF furnace, which affects the smelting rhythm; when a large amount of solid slag exists, the arc striking is difficult, and even the danger of breaking an electrode exists; and if pre-melted slag is used for slagging completely, the production cost is greatly increased. Moreover, the steel-tapping temperature of the conventional electric arc furnace is generally required to be above 1600° C., and the oxygen content in molten steel during steel-tapping is up to 80 ppm; however, the higher steel-tapping temperature is not beneficial to energy conservation and emission reduction, and the higher oxygen content increases the difficulty of the subsequent refining and deoxidation process.
Therefore, how to provide a high-speed steel smelting process that has a high alloy recovery rate, meets the requirements of energy conservation and emission reduction, and has high smelting efficiency and good product performance is of important significance for the development of the field of ferrous metallurgy.
An objective of the present invention is to provide a process for smelting high-speed steel by using an intermediate frequency furnace-LF furnace-VD, which solves the problems of a low alloy recovery rate, low smelting efficiency, serious environmental pollution, high energy consumption, and poor product performance of the conventional smelting process.
In order to achieve the above objective, the present invention provides the following technical solution.
The present invention provides a process for smelting high-speed steel by an intermediate frequency furnace-LF furnace-VD, which includes the following steps:
Preferably, in the process for smelting high-speed steel by using the intermediate frequency furnace-LF furnace-VD, the steel material in the step (1) is a waste steel material, and the waste steel material is one or more of steel ingot cutting heads, rolling waste, and waste drill bits.
Preferably, in the process for smelting high-speed steel by using the intermediate frequency furnace-LF furnace-VD, the slagging agent in the step (1) is a mixture of lime and fluorite with a mass ratio of 7-10:1.
Preferably, in the process for smelting high-speed steel by using the intermediate frequency furnace-LF furnace-VD, in the step (1) to the step (3), the internal control standards for the chemical components are independently as follows in percentage by weight: C 0.86-0.94%, Mn 0.20-0.35%, Si 0.25-0.35%, S≤0.005%, P≤0.030%, Cr 3.90-4.30%, V 1.80-2.00%, W 6.00-6.30%, and Mo 4.80-5.00%.
Preferably, in the process for smelting high-speed steel by using the intermediate frequency furnace-LF furnace-VD, the molten steel for steel tapping in the step (1) has a temperature of 1530-1550° C.
Preferably, in the process for smelting high-speed steel by using the intermediate frequency furnace-LF furnace-VD, the molten steel for steel tapping in the step (2) has a temperature of 1570-1585° C.
Preferably, in the process for smelting high-speed steel by using the intermediate frequency furnace-LF furnace-VD, the soft blowing in the step (3) is performed for 10-17 min.
Preferably, in the process for smelting high-speed steel by using the intermediate frequency furnace-LF furnace-VD, the molten steel for steel tapping in the step (3) has a temperature of 1475-1485° C.
Preferably, in the process for smelting high-speed steel by using the intermediate frequency furnace-LF furnace-VD, in the step (3), when a furnace type of the VD furnace is 20 t, an initial flow rate of argon for vacuum extraction by closing the cover is 13-16 NL/min, the flow rate of argon is increased to 50-54 NL/min after the vacuum degree reaches 67 Pa, and the flow rate of argon is reduced to 13-16 NL/min after the degassing treatment is performed for 13-20 min.
It can be known from the technical solution that, compared with the prior art, the present invention has the following beneficial effects.
The present invention provides a process for smelting high-speed steel by an intermediate frequency furnace-LF furnace-VD, which includes the following steps:
In the present invention, the high-speed steel smelted is preferably CW6Mo5Cr4V2.
In the present invention, in the step (1) to the step (3), the internal control standards for the chemical components are preferably independently as follows in percentage by weight: C 0.86-0.94%, Mn 0.20-0.35%, Si 0.25-0.35%, S≤0.005%, P≤0.030%, Cr 3.90-4.30%, V 1.80-2.00%, W 6.00-6.30%, and Mo 4.80-5.00%.
In the present invention, before the steel material is melted in the intermediate frequency furnace in the step (1), the steel material also needs to be sorted and cleaned to reduce impurities entering the smelting process.
In the present invention, the steel material in the step (1) is preferably a waste steel material, and the waste steel material is preferably one or more of steel ingot cutting heads, rolling waste, and waste drill bits.
In the present invention, according to the sampling analysis result in the step (1), if the phosphorus content is higher than the internal control standard, the phosphorus content is reduced by adding low-phosphorus pure iron.
In the present invention, the slagging agent in the step (1) is preferably a mixture of lime and fluorite with a mass ratio of 7-10:1, more preferably a mixture of lime and fluorite with a mass ratio of 7.5-9.2:1, and still more preferably a mixture of lime and fluorite with a mass ratio of 8:1.
In the present invention, an amount of aluminum particles added in the step (1) is preferably 1.4-1.7 kg/ton of molten steel, more preferably 1.45-1.62 kg/ton of molten steel, and still more preferably 1.53 kg/ton of molten steel.
In the present invention, the mass of the slag in the step (1) is preferably 3-5% of the mass of the molten steel, more preferably 3.3-4.7% of the mass of the molten steel, and still more preferably 4.1% of the mass of the molten steel.
In the present invention, a temperature of the molten steel for steel tapping in the step (1) is preferably 1530-1550° C., more preferably 1534-1548° C., and still more preferably 1545° C.
In the present invention, a temperature of the electric heating in the step (2) is preferably 1470-1510° C., more preferably 1472-1506° C., and still more preferably 1489° C.
In the present invention, the aluminum content in the molten steel in the step (2) is preferably 0.03-0.05%, more preferably 0.035-0.048%, and still more preferably 0.042%.
In the present invention, a temperature of the molten steel for steel tapping in the step (2) is preferably 1570-1585° C., more preferably 1571-1579° C., and still more preferably 1576° C.
In the present invention, the heat insulating agent in the step (3) is preferably carbonized rice husk.
In the present invention, the time of the degassing treatment in the step (3) is preferably 13-20 min, more preferably 14-19 min, and still more preferably 17 min.
In the present invention, the time of the soft blowing in the step (3) is preferably 10-17 min, more preferably 11-15 min, and still more preferably 14 min.
In the present invention, a temperature of the molten steel for steel tapping in the step (3) is preferably 1475-1485° C., more preferably 1478-1484° C., and still more preferably 1481° C.
In the present invention, when a furnace type of the VD furnace in the step (3) is 20 t, an initial flow rate of argon for vacuum extraction by closing the cover is preferably 13-16 NL/min, more preferably 13.4-15.8 NL/min, and still more preferably 15.2 NL/min; after the vacuum degree reaches 67 Pa, the flow rate of argon is increased to preferably 50-54 NL/min, more preferably 51-53.5 NL/min, and still more preferably 52.6 NL/min; and after the degassing treatment is performed for 13-20 min, the flow rate of argon is reduced to preferably 13-16 NL/min, more preferably 13.1-15.2 NL/min, and still more preferably 13.6 NL/min.
The technical solutions in the examples of the present invention will be clearly and completely described below. Apparently, the described examples are merely a part, rather than all of the examples of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.
In a 20 t intermediate frequency furnace-20 t LF furnace-VD vacuum treatment production line for smelting M2 (CW6Mo5Cr4V2) high-speed steel, internal control standards (in percentage by weight) for chemical components are as follows: C 0.86-0.94%, Mn 0.20-0.35%, Si 0.25-0.35%, S≤0.005%, P≤0.030%, Cr 3.90-4.30%, V 1.80-2.00%, W 6.00-6.30%, and Mo 4.80-5.00%.
The smelting process includes the following steps:
According to the analysis results, 120 kg of ferrochrome (high chromium), 160 kg of ferrovanadium (vanadium 50 wt %), and 130 kg of ferromolybdenum (molybdenum 60 wt %) were added in sequence, the reaction system was powered for 5 min, a sample was taken again for spectrum analysis, and the second analysis results are shown in Table 2:
According to the analysis results, the chemical components were basically qualified, the furnace body was slightly inclined, and the slag is completely removed; 30 kg of aluminum particles were added, 400 kg of lime, 50 kg of fluorite, and 120 kg of steel-making accelerant were added, the reaction system was powered, the slag surface was continuously stirred by a wood stick to promote slagging, the temperature was measured after the slag was molten, and steel temperature was performed when the temperature was 1550° C.
The slag was dipped to observe the color and the fluidity of the slag, it was found that the slag was yellowish, and part of aluminum particles were added to adjust the slag to be white or yellowish white; and the reaction system was continuously powered for 15 min, the temperature was measured to be 1570° C., a sample was taken again for spectrum analysis, and the second analysis results are shown in Table 4:
The recovery rate of aluminum was calculated at 70%, 4.3 kg of aluminum wires was fed according to the control target of the Al content in the molten steel of 0.04%, the reaction system was powered for 5 min, the temperature was measured to be 1583° C., and steel tapping was performed.
In a 20 t intermediate frequency furnace-20 t LF furnace-VD vacuum treatment production line for smelting M2 (CW6Mo5Cr4V2) high-speed steel, internal control standards (in percentage by weight) for chemical components are as follows: C 0.86-0.94%, Mn 0.20-0.35%, Si 0.25-0.35%, S≤0.005%, P≤0.030%, Cr 3.90-4.30%, V 1.80-2.00%, W 6.00-6.30%, and Mo 4.80-5.00%.
The smelting process includes the following steps:
According to the analysis results, 140 kg of ferrochrome (high chromium), 175 kg of ferrovanadium (vanadium 60 wt %), and 180 kg of ferromolybdenum (molybdenum 60 wt %) were added in sequence, the reaction system was powered for 8 min, a sample was taken again for spectrum analysis, and the second analysis results are shown in Table 7:
According to the analysis results, the chemical components were basically qualified, the furnace body was slightly inclined, and the slag is completely removed; 32 kg of aluminum particles were added, 440 kg of lime, 50 kg of fluorite, and 110 kg of steel-making accelerant were added, the reaction system was powered, the slag surface was continuously stirred by a wood stick to promote slagging, the temperature was measured after the slag was molten, and steel temperature was performed when the temperature was 1545° C.
The slag was dipped to observe the color and the fluidity of the slag, it was found that the slag was yellowish, and part of aluminum particles were added to adjust the slag to be white; and the reaction system was continuously powered for 17 min, the temperature was measured to be 1558° C., a sample was taken again for spectrum analysis, and the second analysis results are shown in Table 9:
The recovery rate of aluminum was calculated at 70%, 2.9 kg of aluminum wires was fed according to the control target of the Al content in the molten steel of 0.035%, the reaction system was powered for 5 min, the temperature was measured to be 1579° C., and steel tapping was performed.
The above descriptions are only preferred embodiments of the present invention. It should be noted that those of ordinary skill in the art can also make several improvements and modifications without departing from the principle of the present invention, and such improvements and modifications shall fall within the protection scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202210060668.X | Jan 2022 | CN | national |
This application is the national phase entry of International Application No. PCT/CN2022/125051, filed on Oct. 13, 2022, which is based upon and claims priority to Chinese Patent Application No. 202210060668.X, filed on Jan. 19, 2022, the entire contents of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2022/125051 | 10/13/2022 | WO |
