TWI680185B - Method of producing stainless steel - Google Patents

Abstract

The invention provides a method for manufacturing stainless steel, which is a vacuum oxygen decarburization process for molten steel in a ladle to obtain a first molten steel, and then the second molten steel melted by an intermediate frequency furnace is added to the ladle In the free volume, more stainless steel molten steel is obtained.

Description

Manufacturing method of stainless steel

The invention relates to a method for manufacturing stainless steel, in particular to a method for manufacturing stainless steel using a vacuum blowing oxygen decarburization process.

Conventional stainless steel manufacturing methods include two-stage and three-stage composite steelmaking. The two-stage steelmaking method first uses a primary smelting furnace to melt scrap steel and alloyed iron (for example: ferrochrome, nickel iron) to produce stainless steel preliminary molten steel. Next, a ladle is used to load the stainless steel preliminary molten steel and sent to a refining furnace for a refining process to produce stainless steel molten steel that meets the specifications. The primary refining furnace may be an electric furnace, and the refining process may be atmospheric refining or vacuum refining. The atmospheric refining may be, for example, an Argon Oxygen Decarburization (AOD) process, and the vacuum refining may be, for example, a vacuum oxygen degassing Carbon (VacuumOxygen Decarburization, VOD) process.

In the two-stage steelmaking method, the use of an electric furnace with an argon oxygen decarburization process has the advantages of high capacity and high flexibility in the selection of raw materials. However, due to the high cost of argon and the argon oxygen decarburization process, it is not conducive to manufacturing requirements. Very low carbon, hydrogen and nitrogen steel grades. Conversely, the use of an electric furnace with a vacuum oxygen decarburization process is suitable for refining steels with very low carbon, hydrogen and nitrogen. When a ladle with molten steel is placed in a vacuum tank for oxygen decarburization, in order to avoid the splash of molten steel, the ladle must reduce the amount of molten steel in the ladle, resulting in a long process and low production capacity. Shortcomings.

The three-stage steelmaking method uses vacuum oxygen decarburization as the final treatment process. First, as in the two-stage steelmaking method, a stainless steel preliminary molten steel is produced using a primary furnace (electric furnace), and then a converter is used to perform an oxygen decarburization process on the preliminary molten steel. Then, a vacuum oxygen decarburization process is performed to obtain stainless steel molten steel. In the three-stage steelmaking method, the converter may be an Argon Oxygen Decarburization (AOD) process or a Metal Refining Process (MRP) process.

Compared with the two-stage steelmaking method, the three-stage steelmaking method can combine the advantages of an electric furnace with an argon oxygen decarburization process and an electric furnace with a vacuum oxygen decarburization process. Very low carbon, hydrogen and nitrogen steel. However, both the three-stage steelmaking method and the two-stage steelmaking method that performs a vacuum oxygen decarburization process cannot avoid the problems of low productivity and long time.

In view of this, there is an urgent need to provide a method for manufacturing stainless steel by adding molten steel melted by an intermediate frequency furnace after a vacuum oxygen decarburization process to increase production capacity and thereby reduce process time.

One aspect of the present invention is to provide a method for manufacturing stainless steel, which is obtained by adding a second molten steel melted by an intermediate frequency furnace to a free volume of a steel drum after a vacuum oxygen decarburization process. Molten steel.

Another aspect of the present invention is to provide a method for manufacturing stainless steel. Method, which is a method of vacuum blowing oxygen and decarburization of molten steel obtained by smelting scrap steel and alloy iron, and mixing the obtained first molten steel with a second molten steel having a carbon content of less than 1.0% to obtain stainless steel molten steel. .

According to one aspect of the present invention, a method for manufacturing stainless steel is provided. First, supply molten steel to the ladle. The distance between the molten steel level and the top edge of the ladle is defined as the free distance, and the free distance and the inner diameter of the ladle are defined as the free volume. Next, the steel ladle is moved into a vacuum oxygen decarburization furnace, and a vacuum oxygen decarburization process is performed on the molten steel to obtain the first molten steel. Then, an intermediate frequency furnace is used to melt the second molten steel, wherein the volume of the second molten steel is less than the aforementioned free volume. After the vacuum oxygen decarburization process is completed, a second molten steel is added to the free volume of the steel ladle to obtain stainless steel molten steel.

According to an embodiment of the present invention, the molten steel and the second molten steel each include iron, chromium, and / or nickel.

According to an embodiment of the present invention, the method further includes performing an arc high-temperature melting process on scrap steel and alloy iron to obtain the above-mentioned molten steel.

According to an embodiment of the present invention, the method further includes performing an arc high temperature melting process on scrap steel and alloy iron to obtain primary molten steel. Next, the converter is used to perform oxygen blowing and decarburization on the primary molten steel to obtain molten steel.

According to an embodiment of the present invention, the alloy iron includes ferrochrome and / or nickel iron.

According to an embodiment of the present invention, after the first molten steel has completed the vacuum oxygen decarburization process, it further includes a reduction process of the first molten steel.

According to another aspect of the present invention, a method for manufacturing stainless steel is provided. First, the arc high temperature melting process is performed on scrap steel and alloy iron to Get molten steel. Next, the molten steel is moved into a steel ladle, and a vacuum oxygen decarburization process is performed on the molten steel to obtain the first molten steel. After the vacuum oxygen decarburization process is completed, a second molten steel is added to the first molten steel to obtain a stainless steel molten steel, wherein the carbon content of the second molten steel is, for example, less than 1.0%.

According to an embodiment of the present invention, before adding the second molten steel, the distance between the molten steel level of the first molten steel and the top edge of the ladle is defined as a free distance, and the free distance is within the ladle. The diameter is defined as the free volume.

According to an embodiment of the present invention, the method further includes smelting the second molten steel by using an intermediate frequency furnace.

According to an embodiment of the present invention, before moving the molten steel into the ladle, the method further includes performing a process of blowing oxygen and decarburizing the molten steel by using a converter.

According to an embodiment of the present invention, before adding the second molten steel, the method further includes performing a reduction process on the first molten steel.

The manufacturing method of stainless steel to which the present invention is applied is by performing a vacuum oxygen decarburization process on molten steel in a ladle to obtain a first molten steel having a specific carbon content, and then smelting a second molten steel in an intermediate frequency furnace. The molten steel is added to the free volume of the steel bucket, thereby obtaining a higher yield of stainless steel molten steel.

100‧‧‧ Method

110‧‧‧Procedure of supplying molten steel to steel ladle

120‧‧‧ Vacuum blowing oxygen decarburization process for molten steel to obtain the first molten steel

130‧‧‧The step of smelting the second molten steel by using the intermediate frequency furnace

140‧‧‧ Add the second molten steel to the free volume of the steel bucket to obtain stainless steel molten steel

In order to make the above and other objects, features, advantages, and embodiments of the present invention more comprehensible, the detailed description of the drawings is as follows: [FIG. 1] illustrates a method for manufacturing stainless steel according to an embodiment of the present invention flow chart.

As mentioned above, the present invention provides a method for manufacturing stainless steel, which is obtained by adding a second molten steel melted by an intermediate frequency furnace to a free volume of a steel drum after a vacuum oxygen decarburization process, to obtain stainless steel. Molten steel.

Please refer to FIG. 1, which is a flowchart illustrating a method 100 for manufacturing stainless steel according to an embodiment of the present invention. First, step 110 is performed to provide molten steel into a steel ladle. In one embodiment, the molten steel includes iron and chromium. In another embodiment, the molten steel includes iron, chromium, and nickel. In one embodiment, the distance between the molten steel level and the top edge of the ladle is defined as a free distance, and the free distance and the inner diameter of the ladle are defined as a free volume. In summary, the product of the free distance and the inner surface area defined by the inner diameter of the steel drum is the free volume of the aforementioned steel drum. In general, the ratio of the free volume to the total volume of the steel drum is not particularly limited. In one embodiment, the ratio of the free volume to the total volume of the steel drum is about 1: 3 to about 1: 4, but in practical applications, the ratio of the free volume to the total volume of the steel drum can be more or less . As mentioned above, the free distance of the steel drum is set to prevent the molten steel from spilling out of the steel drum during subsequent processes, and even cause equipment damage, which in turn interrupts the production process.

In one embodiment, before step 110, an arc high temperature melting process may be selectively performed on the scrap steel and alloy iron to obtain molten steel. In one example, the scrap steel includes scrap stainless steel and / or scrap carbon steel. In one example, the alloy iron includes ferrochrome and / or nickel iron. In another embodiment, prior to step 110, an arc high temperature melting process for scrap steel and alloy iron may be selectively performed by an electric arc furnace (EAF) to obtain primary molten steel, and then, a converter is used. Oxygen decarburization process for primary molten steel to obtain Get molten steel. In another embodiment, the oxygen blowing decarburization process may be, for example, an Argon Oxygen Decarburization (AOD) process or a Metal Refining Process (MRP) process.

Next, the method 100 proceeds to step 120, moving the steel drum into a vacuum oxygen decarburization furnace, and performing a vacuum oxygen decarburization (VOD) process on the molten steel to obtain the first molten steel. Then, step 130 is performed to melt the second molten steel by using the intermediate frequency furnace. In one embodiment, the second molten steel has a carbon content similar to that of the target composition of the first molten steel. In another embodiment, the carbon content of the second molten steel may be, for example, less than 1.0%, but preferably less than 0.1%. In other embodiments, the order of performing steps 120 and 130 is not limited, and steps 120 and 130 may be performed simultaneously.

In the above embodiment, before adding the second molten steel, the distance between the molten steel level of the first molten steel and the top edge of the ladle can also be defined as the free distance, and the product of the free distance and the inner diameter of the ladle is defined It is a free volume, and the volume of the second molten steel is smaller than the free volume of the steel ladle mentioned above. It is necessary to add a slagging agent (such as lime) and a deoxidizing agent (such as ferrosilicon) in the molten steel. Reserve space for some steel buckets. Therefore, before step 130, the free volume must be used to calculate the weight of the raw materials required for smelting in the intermediate frequency furnace. The first molten steel and the second molten steel are preferably molten steel obtained from the same steel type. In one embodiment, the first molten steel may be, for example, a 300-series molten steel, and the second molten steel system includes iron, chromium, and nickel (for example, a 300-series molten steel). In another embodiment, the first molten steel may be, for example, a 400 series molten steel, and the second molten steel system includes iron and chromium (eg, a 400 series molten steel). In an embodiment, the raw material for the intermediate frequency furnace melting is the first molten steel The scrap steel whose target composition is to be refined is similar, and the second molten steel thus obtained has a composition close to the target composition to be refined by the first molten steel.

After step 120 and step 130, step 140 is performed to add the second molten steel to the free volume of the ladle to increase the total amount of the molten steel in the ladle. In one embodiment, before adding the second molten steel, the distance between the molten steel level of the first molten steel and the top edge of the ladle is defined as a free distance, and the product of the free distance and the inner diameter of the ladle is defined as Free volume, and the volume of the second molten steel is less than the free volume.

Alternatively, in the above step 140, after the first molten steel has completed the oxygen blowing and decarburization process or before the second molten steel is added, the first molten steel may be selectively subjected to the reduction process before the second molten steel is added. In summary, the above reduction process may include adding ferrosilicon as a deoxidizing agent and adding lime as a slagging agent to reduce the first molten steel to slagging and adjust the composition of the molten steel to obtain stainless steel with a preset composition Molten steel. In one embodiment, the stainless steel molten steel is used to produce 304 stainless steel, and its preset composition (ie, the target composition to be refined) contains less than 0.06 wt% carbon, less than 0.6 wt% silicon, and less than 2.0 wt%. Manganese, less than 0.04 wt% phosphorus, less than 0.01 wt% sulfur, 8.0 wt% to 9.0 wt% nickel, 18.0 wt% to 19.0 wt% chromium, less than 0.5 wt% molybdenum, less than 0.6 wt% copper , Less than 0.06wt% nitrogen, the remaining components are iron and unavoidable impurities.

The following uses several embodiments to illustrate the application of the present invention, but it is not intended to limit the present invention. Those with ordinary knowledge in the technical field of the present invention can make various changes and modifications without departing from the spirit and scope of the present invention. Retouch.

Example 1

Example 1 uses the above method to produce 304 stainless steel. The composition of 304 stainless steel is required to contain less than 0.06% carbon, less than 0.6wt% silicon, less than 2.0wt% manganese, less than 0.04wt% phosphorus, and less than 0.01wt%. Sulfur, 8.0 wt% to 9.0 wt% nickel, 18.0 wt% to 19.0 wt% chromium, less than 0.5 wt% molybdenum, less than 0.6 wt% copper, less than 0.06 wt% nitrogen, the remaining ingredients are iron and inevitable Impurities.

First, molten steel prepared by electric furnace (two-stage steelmaking method) or converter (three-stage steelmaking method) is transferred into a steel ladle and placed in a vacuum oxygen decarburization furnace. The volume of molten steel accounts for two-thirds of the volume of the ladle. Taking the inner diameter of the steel bucket as 200cm, the free distance is 100cm, and the molten steel is about 49 tons (the density of 300 series molten steel is 7.80g / cm ³ and the density of 400 series molten steel is 7.69g / cm ³ ), so The free volume of the steel bucket is about 3.14 × 10 ⁶ cm ³ . Then, the vacuum oxygen decarburization furnace is evacuated, and the oxygen steel is subjected to an oxygen decarburization process to obtain 49 tons of the first molten steel. The above-mentioned molten steel can be prepared by a conventional manufacturing process, and the carbon content of the first molten steel is less than 0.1%, and the rest is not described herein.

In addition, based on the free volume of the ladle, it is estimated that the ladle can hold about 20 tons of molten steel. Next, scrap steel having a composition similar to the target composition to be refined in the first molten steel is added to the intermediate frequency furnace as a raw material to be smelted into a second molten steel of 20 tons, wherein the second molten steel contains iron, chromium and nickel. And the carbon content is less than 0.1%.

After the vacuum oxygen decarburization process is completed, the vacuum is broken, and the second molten steel is poured into the free distance of the ladle to form the third molten steel, and the slag is reduced and the composition is adjusted to make the The composition of the third molten steel in the barrel was adjusted to the composition required by the above 304 stainless steel, and 69 tons of Rusty steel molten steel.

Example 2 and Comparative Example

Example 2 uses a process similar to Example 1 to produce 304 stainless steel. The difference is that the volume of the first molten steel in Example 2 accounts for three-quarters of the total volume of the ladle, and the weight of the molten steel is approximately With 55 tons, the specifications of the steel bucket are the same as in Example 1. With a free distance of 75 cm and a free volume of 2.36 × 10 ⁶ cm ³ , the molten steel that can be contained is about 16 tons. An intermediate frequency furnace is used to melt 16 tons of the second molten steel and add it to the steel drum. Therefore, after the process of reducing slagging and adjusting components is completed, Example 2 can obtain 71 tons of stainless steel molten steel.

The comparative example was carried out in the same way as in Example 1, except that the comparative example used a conventional process, that is, the second molten steel was not added after the vacuum oxygen decarburization process was completed, so only the first molten steel was reduced to produce Process of slag and adjusting ingredients. Therefore, the weight of the stainless steel molten steel produced in the comparative example was only 49 tons.

According to the above embodiment, by the method for manufacturing stainless steel provided by the present invention, a vacuum oxygen decarburization process is performed on molten steel in a steel ladle to obtain a first molten steel with a specific carbon content, and then the intermediate frequency furnace is The smelted second molten steel is added to the free volume of the ladle, thereby increasing the total amount of stainless steel ladle in the ladle and increasing the output after the process, which can effectively reduce the process time and production costs.

Although the present invention has been disclosed as above with several embodiments, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field to which the present invention pertains can make various modifications without departing from the spirit and scope of the present invention. Changes and retouching, so the protection scope of the present invention shall be determined by the scope of the appended patent application.

Claims (11)

A method for manufacturing stainless steel includes: providing a molten steel to a ladle, wherein a distance between a molten steel level of the molten steel and a top edge of the ladle is defined as a free distance, and the free distance The inner diameter of one steel ladle is defined as a free volume; the steel ladle is moved into a vacuum oxygen decarburization furnace, and a vacuum oxygen decarburization process is performed on the molten steel to obtain a first molten steel ; Smelting a second molten steel by an intermediate frequency furnace, wherein a volume of the second molten steel is less than the free volume, and a carbon content of the second molten steel is less than 1.0%; and after the vacuum oxygen degassing is completed, After the carbon process, the second molten steel is added to the free volume of the steel ladle to obtain a stainless steel molten steel, wherein a component of the second molten steel is similar to a component of the stainless steel molten steel. The method for manufacturing stainless steel according to item 1 of the scope of the patent application, wherein the molten steel and the second molten steel both contain iron and chromium, or the molten steel and the second molten steel both contain iron, chromium, and nickel. The method for manufacturing stainless steel according to item 1 of the scope of patent application, further comprising: performing an arc high temperature melting process on a scrap steel and an alloy iron to obtain the molten steel. The method for manufacturing stainless steel according to item 1 of the scope of patent application, further comprising: performing an arc high temperature melting process on a scrap steel and an alloy iron to obtain a preliminary molten steel; and using a converter to the preliminary molten steel An oxygen blowing decarburization process is performed to obtain the molten steel. The method for manufacturing stainless steel according to item 3 or 4 of the scope of patent application, wherein the alloy iron comprises ferrochrome and / or nickel iron. The method for manufacturing stainless steel according to item 1 of the scope of patent application, wherein after the first molten steel completes the vacuum oxygen decarburization process, the method further includes performing a reduction process on the first molten steel. A method for manufacturing stainless steel includes: performing an arc high temperature melting process on a scrap steel and an alloy iron to obtain a molten steel; moving the molten steel into a steel ladle, and performing a vacuum oxygen decarburization on the molten steel Process to obtain a first molten steel; and after the vacuum oxygen decarburization process is completed, a second molten steel is added to the first molten steel to obtain a stainless steel molten steel in which the carbon of the second molten steel is The content is less than 1.0%, wherein a component of the second molten steel is similar to a component of the stainless steel molten steel. The method for manufacturing stainless steel according to item 7 of the scope of patent application, wherein before adding the second molten steel, a distance between the molten steel level of one of the first molten steel and a top edge of the steel ladle is defined as A free distance, and the free distance and an inner diameter of the steel ladle are defined as a free volume, and a volume of the second molten steel is smaller than the free volume. The method for manufacturing stainless steel according to item 7 of the scope of patent application, further comprising smelting the second molten steel by using an intermediate frequency furnace. According to the method for manufacturing stainless steel described in item 7 of the scope of patent application, before moving the molten steel into the steel ladle, the method further includes performing a process of oxygen decarburization on the molten steel by using a converter. The method for manufacturing stainless steel according to item 7 of the scope of patent application, wherein before adding the second molten steel, the method further includes performing a reduction process on the first molten steel.