CN106319155A - Method and device for adding high vapor pressure magnesium into molten steel - Google Patents

Abstract

The invention provides a method and a device for adding high vapor pressure metal magnesium into molten steel, wherein the magnesium adding device mainly comprises a storage tank, a control valve and a body, the body conveying pipe, an embedded pipe and a three-way pipe comprise the steps of putting the magnesium adding device into a pipe furnace, filling pure magnesium particles with the particle size of 0.5-2mm into the storage tank, opening the control valve after the temperature of the middle lower part of a conveying pipe group is raised to 1120-1200 ℃, adding the pure magnesium particles into the conveying pipe group at the speed of 0.5-1.5g/min, simultaneously opening an argon regulating valve, introducing argon at the flow rate of 0.5-1.5L/min, and loading magnesium vapor in the conveying pipe into the molten steel. Therefore, the invention has the advantages of stable and safe magnesium addition into the molten steel, high magnesium yield, no introduction of alloy elements, low production cost, uniform magnesium distribution in the molten steel and the like.

Description

Method and device for adding high vapor pressure magnesium to molten steel

technical field

The invention relates to a method and a device for adding high vapor pressure magnesium to molten steel. The device is put into a tube furnace, and when the temperature reaches a set temperature, magnesium metal is made to form magnesium vapor, and then loaded into molten steel .

Background technique

Steelmaking is an oxidation refining process, that is, oxygen is blown into molten iron to remove excess elements (C, Si, Mn) and impurities (S, P) in pig iron to meet the limit of steel performance. Due to the effect of oxygen blowing steelmaking, at the end of steelmaking, the maximum oxygen content in molten steel can reach 0.1%, but the solubility of oxygen in solid steel is extremely low (for example, the maximum solubility in δ-Fe is 0.0082%), these Excessive oxygen will be precipitated in the form of FeO or other oxides during the solidification process, thus reducing the performance of the steel. Therefore, the oxygen in the molten steel must be removed after the decarburization is completed. Oxygen in steel includes dissolved free oxygen [O] _D and oxygen [O] _L in inclusions. Deoxidation means adding deoxidizers (such as manganese, silicon, titanium, aluminum, magnesium, etc.) The free oxygen in the steel is transferred to the oxide inclusion (inclusion), floated up and removed to achieve the purpose of reducing the oxygen content in the steel. The level of oxygen content in steel can indirectly reflect the level of the amount of intermediary in steel, and the total oxygen T[O] in steel is commonly used to indicate the cleanliness of molten steel.

The total oxygen content T[O] in the steel is closely related to the quality of the product. The requirements for the oxygen content of typical steel types are shown in Figure 1. Therefore, how to reduce the oxygen content in the steel and improve the cleanliness of the steel? The effective use of deoxidized products is also more and more concerned by metallurgists.

According to the different deoxidizing ability, deoxidizing alloys are divided into weak deoxidizing agents (such as Mn, Si, Ti and other deoxidizing agents) and strong deoxidizing agents (such as Al, Mg, etc.). In the early iron and steel production, silicon and manganese were often used as deoxidizers. Due to the high oxygen content in balance with Si and Mn, in order to remove the oxygen content in steel to an extremely low level, most iron and steel enterprises use Al as the final deoxidizer. . Studies have shown that when the dissolved aluminum content in steel is 0.03%-0.05%, the average oxygen content in steel can be reduced to below 3ppm. However, the cluster Al ₂ O ₃ inclusions remaining in the steel after aluminum deoxidation will greatly reduce the plasticity, toughness, fatigue strength, and corrosion resistance of the steel, especially destroying the continuity of the steel matrix. Under the action of dynamic load, the material will fail, and the steel yield and product quality will be reduced. On the other hand, Al ₂ O ₃ inclusions in the molten steel pouring process can easily cause nozzle blockage and cause production accidents such as pouring interruption.

Magnesium has a strong chemical activity, and Mg has a strong affinity for non-metallic elements in molten steel. As early as 1970's, Mori et al. pointed out the possibility of deoxidizing molten steel by magnesium vapor. They used magnesium as a deoxidizer to obtain [%Mg][%O]<1.0×10 ^-6 at 1873K. Saxena and others studied the possibility of using magnesium as a refining agent for steelmaking, and found that a very small, uniform distribution of spinel (spinel) oxides is formed in the steel, and this spinel has a strong effect on the steel. Fatigue performance and other properties are not impaired.

(Tateyama et al. used magnesium-clad wire (cored wire) (Mg, MgO, CaF ₂ ) to conduct magnesium deoxidation and desulfurization experiments in an induction furnace protected by argon gas on low-carbon steel.) The addition of magnesium is less than 15%, 5 minutes After that, the T[O] and [S] in the molten steel can be reduced to 9ppm, and [S] can be reduced to 3ppm; T[O] and [S] in the molten steel after standing still for 10 minutes have not been found to rise, and they are kept at 11ppm and 3ppm respectively. level. Therefore, it can be seen that Mg has a strong affinity with S and O in molten steel, and does not change the composition of molten steel, so it is an ideal deoxidizing and desulfurizing agent. In addition, with the development of oxide metallurgy technology in recent years, Mg is used to treat molten steel to obtain high melting point, fine and dispersed magnesium-containing intervening fine grains, making the related issues of adding Mg to molten steel a hot issue.

In fact, in the process of iron and steel production, the gas injection method has been used to spray passivation magnesium (passivationmagnesium) particles into molten iron (hot metal) to achieve the purpose of desulfurization of molten iron. A similar method is also used to pass magnesium into molten iron to produce nodular cast iron. Please refer to Figure 2, the relationship between the vapor pressure and temperature of Mg and Al. From Figure 2, it can be seen that Mg has a very high vapor pressure (200 times that of aluminum) at the steelmaking temperature (1600°C) ), obviously, since the molten steel temperature (1600°C) is much higher than the molten iron temperature (1300-1400°C), this method of spraying passivated magnesium particles cannot be directly applied to the magnesium treatment process of molten steel. Therefore, the use of magnesium in actual steelmaking production is also largely limited here. Therefore, how to add magnesium to molten steel in a safe and effective manner has become one of the core issues in the metallurgical technology of molten steel magnesium treatment.

At present, the commonly used methods of adding magnesium to molten steel include flushing method, cored wire method, plunge method, etc. The types of alloys added include rare earth magnesium alloys, high magnesium alloys, and passivated magnesium particles. Wait. The Chinese published patent introduces a method of uniformly paving NiMg alloy on the bottom of an ingot mold and adding magnesium. The range of Mg content in the added NiMg alloy is 5-50%. Obviously, this method introduces metal Ni into the molten steel, which not only destroys the chemical composition of the original molten steel, but also increases the production cost. At the same time, when applying this method, the oxygen level in the steel needs to be adjusted to a higher level, which also increases the total oxygen content of the molten steel.

There is also a magnesium cored wire with a special structure, which is fed into the depth of the molten steel through a cored wire injection system. Obviously, when the magnesium core wire reaches the bottom of the molten steel, the magnesium will undergo the evolution process of Mg(s)→Mg(l)→Mg(g). Due to the huge temperature change between the molten steel and the magnesium core wire, the Mg The process of (s)→Mg(g) is completed in a very short period of time. Since magnesium will generate a very large pressure during the gasification process, it is very easy to cause violent tumbling of molten steel and produce production accidents. There is also a kind of Mg vapor prepared by Aluminothermic reduction, and argon is used as a carrier to introduce magnesium vapor into molten steel.

Although there are many traditional methods of adding magnesium to molten steel, they are obviously flawed and not ideal. The inventor has specially researched and improved this deficiency, and relying on his own expertise and years of experimental experience, Finally, after repeated tests, corrections and improvements, the present invention is born.

Contents of the invention

The invention relates to a method and a device for adding high vapor pressure magnesium to molten steel. The device is a magnesium adding device, which includes a closed material storage tank, a control valve and a delivery pipe group. Put the magnesium adding device into the tube furnace, and then put the pure magnesium particles with a particle size of 0.5-2mm into the storage barrel. Because when the particle size of pure magnesium is less than 0.5mm, the magnesium particles will pass through the embedded pipe in the delivery pipe group and contact the molten steel, and when the particle size is larger than 2mm, the magnesium particles will not be able to pass through the control valve. into the delivery tube. When the temperature in the lower part of the conveying pipe rises to 1120°C-1200°C, open the control valve, feed pure magnesium particles into the conveying pipe at an appropriate feeding speed, and open the argon regulating valve at this time. Because when the argon gas flow is lower than 0.2L/min, the magnesium-containing argon bubbles formed at the bottom of the molten steel will be too large, which is not conducive to the transfer of magnesium in the argon bubbles to the molten steel, and when the argon gas flow is greater than 0.5L/min , or the vapor pressure of magnesium on the surface of molten steel is too low, resulting in a decrease in the yield of magnesium. Therefore, the flow of argon gas at 0.2-0.5L/min can quickly and safely load the magnesium vapor in the delivery pipe into the molten steel.

Magnesium metal has a strong affinity with oxygen and sulfur in steel, and has a very high deoxidation and desulfurization effect, and the MgO and MgS intermediaries produced by it have the characteristics of small size and uniform particle size distribution. Using magnesium as the primary deoxidation element in the steelmaking process, or as a secondary deoxidation and desulfurization element, not only can achieve extremely low levels of total oxygen and sulfur content in steel, but also can be used as an improvement after primary deoxidation with aluminum, titanium, etc. Inclusion modifier, which modifies the large aluminum oxide and titanium oxide inclusions in the steel into fine magnesium-aluminum, magnesium-titanium composite inclusions. Lay the foundation for the application of oxide metallurgy technology.

However, the melting point and boiling point of metallic magnesium are 670°C and 1100°C respectively. Under the condition of steelmaking temperature (1600°C), its vapor pressure will reach 20-25 atmospheres. If solid metallic magnesium is directly added to molten steel, on the one hand it will Inevitably, violent tumbling of molten steel and even explosion accidents are caused, and on the other hand, the yield of magnesium is seriously reduced. Therefore, using the device and method of the present invention, magnesium can be added to the molten steel in a safe and efficient manner, which becomes the key to the magnesium treatment of molten steel.

Description of drawings

Figure 1 is a diagram of the requirements of the existing typical steel grades on the oxygen content;

Fig. 2 is the relationship figure of vapor pressure and temperature of existing Mg and Al;

Fig. 3 is the schematic sectional view of magnesium adding device of the present invention;

Fig. 4 is a schematic diagram of putting the magnesium addition device of the present invention into a tube furnace.

Explanation of reference signs: 1 magnesium adding device; 11 storage tank; 12 control valve; 13 body; 131 conveying pipe; 132 embedded pipe; 1321 air hole; ; 16 crucible; 2 tube furnace; 20 furnace; 21 pipeline; 211 valve; 212 valve; 213 valve; 22 gas purifier; 23 flow meter; 230 flow meter; sensor.

detailed description

The following are examples, but the contents of the present invention are not limited to the scope of these examples.

First, please refer to FIG. 3 , which is a schematic cross-sectional view of the magnesium addition device of the present invention. The magnesium addition device 1 is mainly composed of a storage tank 11 , a control valve 12 and a body 13 . The main body 13 has a conveying pipe 131, and an embedded pipe 132 is arranged in the hollow interior. The embedded tube 132 is closed at the bottom of the embedded tube 132 and has several air holes 1321, and a temperature sensor 14 is arranged at the bottom of the embedded tube 132, and a corrosion resistant coating is formed on the inner wall of the body 13 15. The above components are tightly connected to prevent air from entering.

Next, the magnesium addition device 1 of the present invention is installed in the hearth 20 of the tube furnace 2, with reference to Fig. 4, the magnesium addition device 1 is put into the tube furnace 2, the magnesium addition in the tube furnace 2 The upper and lower ends of the device 1 are respectively extended and communicated by pipelines 21, and valves 211, 212 and 213 are respectively provided at different positions, and a gas purifier 22 is provided between the valves 211 and 213, and flow meters 23 and 230 are provided. , the uppermost end is connected to the valve 213 by a gas delivery conduit 24, a crucible is placed on the inner wall of the magnesium addition device 1 for placing molten steel 3, and a temperature sensor 4 is provided on the outer wall of the tube furnace 2.

Under the condition of steelmaking temperature of 1600°C, how to add magnesium into molten steel safely and with high yield is the important core of the present invention. Please still refer to shown in Fig. 3 and 4, when the present invention is actually used, first valve 211, 212 and 213 are opened, then valve 212 is adjusted to make flowmeter 230 flow range be the flow rate of 1-2L/min, and feed argon Gas for 10 minutes, so that the oxygen partial pressure in the tube furnace 2 is reduced to the minimum. Next, put pure magnesium particles with a particle size of 0.5-2min into the storage tank 11, and adjust the valve 213 so that the flow rate of the flow meter 23 in the range of 0.5-1L/min is fed into the argon gas for 5 minutes, and then close the valve 213. Then energize the steel in the crucible 16 of the tubular furnace 2 to heat up to 1600° C., and then keep the temperature to completely melt the steel in the crucible 16 , so that the temperature of the molten steel 3 is evened.

At this time, the magnesium adding device 1 is placed above the crucible 16 of the tube furnace 2, and when the temperature sensor 14 detects that the temperature ranges from 1120° C. to 1200° C., it remains within this range. At this time, the control valve 12 is opened, and the pure magnesium particles in the storage tank 11 are added into the inline pipe 132 at a certain speed of adding magnesium particles, and the pure magnesium particles can be vaporized by the temperature to form magnesium vapor. At this time, the valve 213 is opened, and argon gas is introduced at a flow rate of 0.2-0.5 L/min to complete the process of adding magnesium to the molten steel.

Therefore, use the technology that the present invention adds high vapor pressure magnesium in molten steel 3, have following advantage obviously:

(1) The present invention mainly adds pure magnesium to molten steel 3, so other elements will not be introduced to complicate the composition of molten steel 3.

(2) The feature of the present invention is to use argon gas as a carrier to add magnesium metal into molten steel 3 after it is vaporized, so as to avoid the danger of explosion due to direct contact between solid magnesium particles and liquid molten steel.

(3) The present invention adopts argon gas as protective gas throughout the course of implementation to avoid oxidation of magnesium in contact with air.

(4) The focus of the present invention is to utilize the temperature range of 1120° C.-1200° C. in the furnace 20 of the tube furnace 2 to achieve the gasification process of magnesium, and no additional heating device for heating and gasifying magnesium is required.

(5) The present invention vaporizes solid magnesium in the temperature range of 1120°C-1200°C, and the vapor pressure of magnesium in this temperature range is only 4 atmospheres.

(6) The embedded pipe 132 of the present invention is made of high-temperature-resistant stainless steel; therefore, the conveying pipe 131 will not burst during the magnesium gasification process.

(7) The present invention uses argon gas as a carrier when adding magnesium to the molten steel 3, which can well and evenly form the composition of the molten steel 3, avoiding the total distribution of magnesium components in the molten steel 3 during the addition of the tube furnace 2 uneven condition.

(8) In the present invention, when magnesium is added to molten steel 3, the recovery rate of magnesium is relatively high.

(9) The present invention can accurately control the magnesium content in the steel by controlling the amount of magnesium added to the embedded pipe 14 by the storage tank 11 and cooperating with the magnesium adding time.

In summary, the present invention can safely and stably add magnesium into molten steel without introducing other alloy elements, not only has low production cost but also has a high yield of magnesium, especially the distribution of magnesium in molten steel is very uniform , and the same or similar device or method has not been found to be patented or disclosed before the application, and it is reasonable to meet the requirements of the invention patent, and the patent application is filed according to law.

The above-mentioned embodiments are only descriptions of preferred implementations of the present invention, and are not intended to limit the scope of the present invention. Variations and improvements should fall within the scope of protection defined by the claims of the present invention.

Claims (6)

1. the method that a molten steel adds high vapour pressure magnesium, it is characterised in that mainly set a magnesium adding set and put into pipe In formula stove, when magnesium add device middle and lower part temperature rise to design temperature time, add pure magnesium grain, make pure magnesium particle shape become magnesium vapor, By argon, magnesium vapor is loaded in molten steel.

2. the method that molten steel as claimed in claim 1 adds high vapour pressure magnesium, it is characterised in that argon regulation valve with The flow of 0.5～1.5L/min is passed through argon.

3. the method that molten steel as claimed in claim 1 adds high vapour pressure magnesium, wherein, this magnesium vapor utilize argon with The flow of 0.2～0.5L/min is added in molten steel.

4. the method that molten steel as claimed in claim 1 adds high vapour pressure magnesium, wherein, the particle diameter of this pure magnesium grain is 0.5～2mm.

5. the device of the molten steel high vapour pressure magnesium of interpolation, it is characterised in that it is mainly by magnesium adding set and tube furnace institute Composition, this magnesium adding set includes:

One storage vat, for hermetic container, is located at topmost；

One body, for hollow tubular, combines closely with this storage vat, forms a conveying pipe；One control valve, is located at Between this storage vat and this conveying pipe, the blanking of storage vat can be adjusted；One embedded pipe, is located in this conveying pipe, and it is close Closing shape, bottom offers several pore.

6. molten steel as claimed in claim 5 adds the device of high vapour pressure magnesium, wherein, offers bottom this embedded pipe Several apertures are less than the pore of pure magnesium grain.