A novel ingot mould device and ingot mould method for nitrogen-containing silicon steel plate shape ingot

Abstract

The application discloses a novel ingot mould device and ingot mould method for controlling nitrogen of silicon steel plate shape, and belongs to the technical field of smelting and casting. The technical problem of serious element segregation, internal pore and loose defects in smelting a novel nitrogen control steel plate shape ingot is solved. The ingot mould device is arranged at the molten steel outlet of a vacuum induction device. The ingot mould device comprises a plate shape water-cooled copper mould, a heat preservation riser, a double-hole pouring funnel and an electromagnetic stirrer. The heat preservation riser is arranged above the plate shape water-cooled copper mould, and the two are arranged in alignment and the inner cavities are communicated. The double-hole pouring funnel is arranged above the heat preservation riser, and the inner cavities are communicated after the two are connected in alignment. The electromagnetic stirrer is arranged outside the plate shape water-cooled copper mould. The application can realize stable preparation of a novel nitrogen control silicon steel plate shape ingot without macroscopic defects and low segregation.

Description

Technical Field

[0001] This invention relates to the field of vacuum induction special smelting and casting technology, and in particular to a novel ingot mold device and method for nitrogen-containing silicon steel plate-shaped ingots. Background Technology

[0002] Grain-oriented silicon steel is an important metallic material used in the transformer manufacturing industry. Its silicon content is approximately 3%, and the amount of oxide inclusions in the steel is required to be extremely low. It is typically designed to contain MnS and AlN as inhibitors to control the grain growth rate. The manufacturing process involves multiple steps, including steelmaking, hot rolling, pickling, cold rolling, and annealing. Precise control of the elements in the steel and coordinated control between multiple deformation heat treatment processes are crucial. Grain-oriented silicon steel exhibits strong directional magnetism, resulting in the lowest iron loss and highest permeability in the rolling direction. Under a certain magnetization field, it also has a high magnetic induction value. The magnetic induction intensity of grain-oriented silicon steel, as the most critical factor limiting its weight, volume, and load loss, has become a major direction for the upgrading and development of grain-oriented silicon steel materials.

[0003] In the development and design of new nitrogen-containing silicon steel, it is often necessary to optimize the content ratio of inhibitory elements such as Mn, S, Al, N, Cu, Bi, and Sn in the steel, control the content of C, O, H and other impurity elements, and ensure that the ingot has good metallurgical quality during the casting and solidification stage.

[0004] The plate-shaped ingot molds used in existing technologies are usually made of cast iron, which is suitable for smelting and casting most steel grades or alloys. However, for new silicon steels, in order to obtain a high inhibitor content, they contain a high content of nitrogen. The solubility of nitrogen in steel decreases significantly as the temperature decreases, resulting in the formation of a large number of pores inside the billet during solidification and severe segregation of alloying elements, which seriously reduces the yield and may even lead to the scrapping of the entire billet. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a novel ingot mold device and method for nitrogen-controlled silicon steel slab ingots, in order to solve the problems of macroscopic defects such as porosity and severe segregation of alloying elements in the slab ingot during the vacuum induction melting and casting stage.

[0006] The objective of this invention is mainly achieved through the following technical solutions:

[0007] On the one hand, the present invention provides a novel ingot mold device for nitrogen-controlled silicon steel plate-shaped ingots, which is located at the steel molten outlet of a vacuum induction device; the ingot mold device includes a plate-shaped water-cooled copper mold, an insulating riser, a double-hole pouring funnel, and an electromagnetic stirrer;

[0008] The insulating riser is located above the plate-shaped water-cooled copper mold, and the two are aligned and their inner cavities are connected; the double-hole casting funnel is located above the insulating riser, and the two are aligned and connected, and their inner cavities are connected; the electromagnetic stirrer is located on the outside of the plate-shaped water-cooled copper mold.

[0009] In one possible design, the plate-shaped water-cooled copper mold includes a U-shaped water-cooled side sealing plate and a first rectangular water-cooled panel and a second rectangular water-cooled panel with the same structure.

[0010] The first rectangular water-cooled panel and the second rectangular water-cooled panel are arranged parallel to each other on both sides of the U-shaped water-cooled side sealing plate, and their bottoms are connected to the bottom surface of the U-shaped water-cooled side sealing plate; the area enclosed by the three together constitutes a casting cavity for holding molten steel and ingots.

[0011] In one possible design, the electromagnetic stirrer includes a first plate-shaped electromagnetic stirrer and a second plate-shaped electromagnetic stirrer.

[0012] The first plate-shaped electromagnetic stirrer is located on the outside of the first rectangular water-cooled panel; the second plate-shaped electromagnetic stirrer is located on the outside of the second rectangular water-cooled panel; the first plate-shaped electromagnetic stirrer and the second plate-shaped electromagnetic stirrer are used to form a uniform magnetic field in the casting cavity.

[0013] In one possible design, the ingot mold device also includes two sets of upper and lower fastening clamps with identical structures;

[0014] The fastening fixture includes a U-shaped fixture body; both ends of the U-shaped fixture body are provided with threaded holes and bolts;

[0015] The fastening clamps are used to fix the first rectangular water-cooled panel and the second rectangular water-cooled panel to the two sides of the U-shaped water-cooled side sealing plate.

[0016] In one possible design, the double-hole casting funnel includes a concave channel and a first funnel and a second funnel located on both sides of the concave channel; the bottom of the first funnel has a first funnel outlet; the bottom of the second funnel has a second funnel outlet.

[0017] During casting, the molten steel flows through the concave channel and enters the casting cavity of the plate-shaped water-cooled copper mold through the outlets of the first and second funnels.

[0018] In one possible design, the first funnel outlet and the second funnel outlet are located at one-quarter and three-quarters of the length of the double-hole casting funnel, respectively; the concave channel is located at the middle position of the length of the double-hole casting funnel.

[0019] In one possible design, both the first funnel outlet and the second funnel outlet are circular holes.

[0020] The diameters of the outlets of the first and second funnels are both 25-30 mm.

[0021] In one possible design, the insulating riser is a hollow rectangular frustum.

[0022] Insulating risers are used to improve the feeding efficiency of ingot solidification.

[0023] In one possible design, the outer wall of the insulating riser is made of cast iron, while its inner wall is made of a mixture of magnesia and water glass.

[0024] On the other hand, the present invention also provides a novel ingot mold method for nitrogen-controlled silicon steel plate-shaped ingots, employing the aforementioned novel ingot mold device for nitrogen-controlled silicon steel plate-shaped ingots; the mold method includes the following steps:

[0025] Step 1: Place the ingot mold device at the bottom of the vacuum induction furnace;

[0026] Step 2: Load materials into the vacuum induction device and smelt them to obtain molten steel;

[0027] Step 3: Pour the molten steel through a double-hole pouring funnel into the inner cavity containing the molten steel and ingots to complete the casting process;

[0028] Step 4: Cool the furnace for 1-2 hours under inert gas protection, open the ingot mold device, demold the ingot, and obtain a plate-shaped ingot.

[0029] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0030] (1) This invention is mainly aimed at obtaining plate-shaped billets with good metallurgical quality by means of vacuum induction furnace during the laboratory development and design stage of new steel grades. The plate-shaped water-cooled copper ingot mold of this invention has the characteristics of high cooling intensity and adjustable cooling water inlet temperature and flow rate. Compared with the existing traditional cast iron plate-shaped ingot mold, it greatly improves the cooling and solidification speed of molten steel, reduces the initial grain size inside the billet, has high ingot density and reduces the possibility of forming defects such as porosity, and ensures that the material contains a high nitrogen content.

[0031] (2) The present invention provides magnetic stirrers on both sides of the plate-shaped water-cooled copper mold, which can cause internal disturbance of the molten steel during the solidification process, break dendrites, increase fine crystal nuclei and improve the nucleation rate, further reduce the grain size in the steel, and at the same time reduce the temperature gradient of the molten steel and reduce solidification thermal stress.

[0032] (3) The plate-shaped water-cooled copper mold of the present invention is a flexible assembly and disassembly device composed of a U-shaped water-cooled side sealing plate and two rectangular water-cooled panels. It can produce multiple sets of U-shaped water-cooled side sealing plates of different widths to match with rectangular water-cooled panels to meet the needs of different hot rolling compression ratio process parameters in the development of steel grades. At the same time, by adjusting the parameters of cooling water inlet temperature, flow rate and the energizing frequency of electromagnetic stirring device, plate-shaped billets with good metallurgical quality can be obtained.

[0033] (4) This invention designs a double-hole casting funnel for use with a plate-shaped water-cooled copper mold. The concave channel in the middle can buffer and divert the molten steel poured from the melting crucible. Compared with a single-hole casting funnel, double-hole casting can greatly reduce the flow time of molten steel inside the plate-shaped ingot mold, accelerate the solidification speed, and improve the metallurgical quality of the ingot. In addition, a small amount of molten steel will remain in the concave channel after casting. After solidification, it can be taken out and used to test the chemical composition of the material.

[0034] (5) The ingot mold device and ingot mold method for the novel nitrogen-controlled silicon steel plate-shaped ingot provided by the present invention realize the stable preparation of novel silicon steel plate-shaped billets with good metallurgical quality by vacuum induction melting and casting, which facilitates the subsequent development and research of the deformation heat treatment process of novel nitrogen-controlled silicon steel by hot rolling-pickling-cold rolling-annealing.

[0035] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained through the embodiments described and the accompanying drawings, which are particularly pointed out. Attached Figure Description

[0036] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0037] Figure 1 A schematic diagram of the ingot mold device for the novel nitrogen-containing silicon steel plate-shaped ingot provided by the present invention;

[0038] Figure 2 This is a top view of the plate-shaped water-cooled copper mold of the present invention;

[0039] Figure 3 This is a left view of the ingot mold device of the present invention;

[0040] Figure 4 The image shows the as-cast grain microstructure of the plate-shaped ingot prepared in Example 1.

[0041] Figure 5 The image shows the as-cast grain microstructure of the plate-shaped ingot prepared in Comparative Example 1.

[0042] Figure 6 The image shows the as-cast grain microstructure of the plate-shaped ingot prepared in Comparative Example 2.

[0043] Figure 7 The image shows the as-cast grain microstructure of the plate-shaped ingot prepared in Example 2.

[0044] Figure label:

[0045] 1- Plate-shaped water-cooled copper mold; 11- U-shaped water-cooled side sealing plate; 12- Rectangular water-cooled panel; 2- Insulating riser; 3- Double-hole casting funnel; 31- First funnel outlet; 32- Concave soup channel; 4- Plate-shaped electromagnetic stirrer; 13- First upper fastening fixture; 14- Casting cavity. Detailed Implementation

[0046] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0047] This invention discloses a novel ingot mold device for nitrogen-controlled silicon steel plate-shaped ingots. The ingot mold device is located at the steel molten outlet of a vacuum induction device (e.g., a vacuum induction furnace). The ingot mold device includes a plate-shaped water-cooled copper mold 1, an insulating riser 2, a double-hole pouring funnel 3, and an electromagnetic stirrer 4. The insulating riser 2 is located above the plate-shaped water-cooled copper mold 1, and the two are aligned and connected, with their inner cavities connected. The double-hole pouring funnel 3 is located above the insulating riser 2, and the two are aligned and connected, with their inner cavities connected. The electromagnetic stirrer 4 is located on the outside of the plate-shaped water-cooled copper mold 1.

[0048] Specifically, the plate-shaped water-cooled copper mold 1 is a hollow structure with an open top, and the inside of the plate-shaped water-cooled copper mold 1 is a cavity; the heat-insulating riser 2 is located directly above the plate-shaped water-cooled copper mold 1. After the two are aligned and connected, the inner cavity of the heat-insulating riser 2 is connected to the cavity of the plate-shaped water-cooled copper mold 1; the vacuum induction furnace is used to melt the raw materials of the new nitrogen-controlled silicon steel into high superheated steel liquid. After melting, the high superheated steel liquid enters the cavity of the plate-shaped water-cooled copper mold 1 through the double-hole pouring funnel 3 and the heat-insulating riser 2. Under the strong cooling effect of its cooling water, the steel liquid solidifies rapidly and quickly fills and eliminates the macroscopic defects of internal loose shrinkage cavities. Under the stirring effect of the uniform magnetic field generated by the electromagnetic stirrer 4, the steel liquid can eliminate the segregation of alloying elements.

[0049] In existing technologies, when preparing novel nitrogen-controlled silicon steel ingots, molten steel is directly poured into a plate-shaped ingot mold made of cast iron, resulting in the formation of numerous pores and severe segregation of alloying elements inside the ingot. Compared with existing technologies, this invention uses a plate-shaped water-cooled copper mold 1 to rapidly cool the high-superheated molten steel and uses an electromagnetic stirrer 4 to stir it, which can achieve stable preparation of plate-shaped ingots with no macroscopic defects and low segregation. In addition, this invention uses a vacuum induction furnace as the primary refining equipment, which can strictly control the content of active metal elements such as aluminum and titanium in the alloy and reduce the content of hydrogen, oxygen, and nitrogen in the alloy, thereby obtaining ingots with precise alloying element content and high purity.

[0050] It should also be noted that the ingot prepared by this invention can be directly rolled and heat-treated without a forging process. The composition of the novel nitrogen-controlled silicon steel of this invention, by weight percentage, includes: C: 0.05-0.07 wt.%, Si: 0.8-1.2 wt.%, Mn: 0.12-0.16 wt.%, Al: 0.02-0.03 wt.%, N: 0.020-0.028 wt.%, S: 0.008-0.012 wt.%, Cu: 0.1-0.12 wt.%, Sn: 0.1-0.12 wt.%, Bi: 0.002-0.006 wt.%, with the balance being Fe and unavoidable impurities.

[0051] In order to rapidly cool the molten steel contained therein to form an ingot, the plate-shaped water-cooled copper mold 1 of the present invention includes a U-shaped water-cooled side sealing plate 11, a first rectangular water-cooled panel and a second rectangular water-cooled panel with the same structure; the first rectangular water-cooled panel and the second rectangular water-cooled panel are arranged parallel to each other on both sides of the U-shaped water-cooled side sealing plate 11 and their bottoms are connected to the bottom surface of the U-shaped water-cooled side sealing plate 11; the area enclosed by the three together constitutes a casting cavity 14 for containing molten steel and ingots.

[0052] Specifically, such as Figure 1 and Figure 2 As shown, the U-shaped water-cooled side sealing plate 11 provides the bottom surface and two symmetrical narrow side surfaces of the casting cavity 14, and the two rectangular water-cooled panels provide two symmetrical wide surfaces of the casting cavity 14. The five planes together form a cavity that can hold molten steel / steel ingots.

[0053] Compared with the prior art, the present invention sets up a U-shaped water-cooled side sealing plate 11 and rectangular water-cooled panels 12 on both sides. On the one hand, it can form a casting cavity 14 for holding molten steel and ingots. Through the forced rapid cooling effect of the plate-shaped water-cooled copper mold 1 and the stirring effect of the uniform magnetic field generated by the electromagnetic stirrer 4, the molten steel can be rapidly solidified into a plate-shaped billet with good metallurgical quality. On the other hand, by setting the two rectangular water-cooled panels 12 on both sides of the U-shaped water-cooled side sealing plate 11, the present invention can flexibly assemble and disassemble the device, and can make multiple sets of U-shaped water-cooled side sealing plates 11 with different widths to match with the rectangular water-cooled panels 12 to meet the needs of different hot rolling compression ratio process parameters in the steel grade development process. At the same time, by adjusting the parameters of the cooling water inlet temperature, flow rate and the energizing frequency of the electromagnetic stirrer, a plate-shaped billet with good metallurgical quality can be obtained.

[0054] It should also be emphasized that the present invention can rapidly solidify molten steel by setting up a plate-shaped water-cooled copper mold 1. Due to the high degree of supercooling and fast cooling rate during solidification, the molten steel can not only improve the solidification nucleation rate, but also avoid obvious compositional segregation due to selective crystallization, making the alloy composition more uniform. At the same time, the grain size in the rapidly solidified steel is small and the size distribution is uniform.

[0055] It should be noted that the U-shaped water-cooled side sealing plate 11 and the rectangular water-cooled panels 12 on both sides of the present invention are both made of forged copper. Compared with cast copper, the plate-shaped water-cooled copper mold 1 of the present invention uses forged copper because: forged copper parts are made by hammering copper under high temperature and high pressure, and have a dense structure, high density, high hardness, wear resistance, and good dimensional stability.

[0056] The inner bottom length of the U-shaped water-cooled side sealing plate 11 of the present invention is 360mm, the inner bottom width is 30mm, and the inner height is 180mm. These dimensions are the same as the ingot mold cavity dimensions of the plate-shaped water-cooled copper mold 1.

[0057] The maximum amount of molten steel that can be poured into the casting mold device of the present invention is 15 kg. The geometric dimensions and nominal capacity of this ingot mold can be adjusted according to the requirements of steel smelting and subsequent hot working processes.

[0058] In order to stir the molten steel in the casting cavity 14, the electromagnetic stirrer 4 of the present invention includes a first plate-shaped electromagnetic stirrer and a second plate-shaped electromagnetic stirrer; the first plate-shaped electromagnetic stirrer is located outside the first rectangular water-cooled panel; the second plate-shaped electromagnetic stirrer is located outside the second rectangular water-cooled panel; the first plate-shaped electromagnetic stirrer and the second plate-shaped electromagnetic stirrer are used to form a uniform magnetic field in the casting cavity 14, thereby stirring the molten steel.

[0059] Specifically, both the first plate-shaped electromagnetic stirrer and the second plate-shaped electromagnetic stirrer are double-sided traveling wave magnetic field stirrers with an energizing frequency of 20 to 60 Hz; the two electromagnetic stirrers are respectively fixed to the outside of the two rectangular water-cooled panels 12 of the plate-shaped water-cooled copper mold 1.

[0060] Compared with the prior art, the present invention, by setting a first plate-shaped electromagnetic stirrer on the outer side of the first rectangular water-cooled panel and a second plate-shaped electromagnetic stirrer on the outer side of the second rectangular water-cooled panel, can ensure that the magnetic field formed in the casting cavity 14 is a uniform magnetic field with the magnetic field lines parallel to the horizontal plane of the molten steel, thereby making the solidification quality (including grain size and element homogenization degree) of the plate-shaped new silicon steel billet have good consistency from bottom to top.

[0061] In order to fix the two rectangular water-cooled panels 12 to both sides of the U-shaped water-cooled side sealing plate 11, the ingot mold device of the present invention further includes two sets of upper and lower fastening clamps with the same structure; the fastening clamps include U-shaped clamp bodies; both ends of the U-shaped clamp bodies are provided with threaded holes and bolts; the fastening clamps are used to fix the first rectangular water-cooled panel and the second rectangular water-cooled panel to the two sides of the U-shaped water-cooled side sealing plate 11.

[0062] Specifically, such as Figure 2 and Figure 3 As shown, the upper set of fastening fixtures includes a first upper fastening fixture 13 and a second upper fastening fixture; the lower set of fastening fixtures includes a first lower fastening fixture and a second lower fastening fixture; the first upper fastening fixture 13 and the second upper fastening fixture are symmetrically arranged and both are located in the upper half of the water-cooled copper mold; the first lower fastening fixture and the second lower fastening fixture are symmetrically arranged and both are located in the lower half of the water-cooled copper mold; each of the four fastening fixtures includes a U-shaped fixture body, with threaded holes at both ends of the U-shaped fixture body, and bolts installed in the threaded holes; during fixing, the first rectangular water-cooled panel and the second rectangular water-cooled panel are first set parallel to each other. On both sides of the U-shaped water-cooled side sealing plate 11, a first plate-shaped electromagnetic stirrer is set on the outer side of the first rectangular water-cooled panel, and a second plate-shaped electromagnetic stirrer is set on the outer side of the second rectangular water-cooled panel. Then, the U-shaped clamp bodies of each fastening fixture are inserted into the side sealing plates of the U-shaped water-cooled side sealing plate 11 from both sides, and each bolt is tightened, thereby fixing the two rectangular water-cooled panels 12 and the two electromagnetic stirrers on the U-shaped water-cooled side sealing plate 11, so that the two rectangular water-cooled panels 12 and the U-shaped water-cooled side sealing plate 11 together constitute the casting cavity 14 for holding molten steel and ingots.

[0063] It should be noted that both the upper and lower fastening clamps of this invention are made of stainless steel. This is because stainless steel has good strength, toughness, fatigue resistance, good corrosion resistance, and a smooth and beautiful surface.

[0064] In order to achieve rapid cooling of the molten steel in the casting cavity 14, the U-shaped water-cooled side sealing plate 11, the first rectangular water-cooled panel and the second rectangular water-cooled panel of the present invention are all connected to cooling water inlet and outlet pipes. In addition, flow meters and thermometers are installed on the cooling water inlet and outlet pipes, so as to monitor the inlet and outlet flow rate and inlet and outlet water temperature parameters in real time.

[0065] It should be noted that the insulating riser 2 of the present invention is in the shape of a hollow rectangular truncated cone. The insulating riser 2 is used to improve the feeding efficiency of ingot solidification. The outer wall of the insulating riser 2 is made of cast iron, and its inner wall is made of a mixture of magnesia and water glass.

[0066] Specifically, the above-mentioned heat-insulating riser 2 is a hollow rectangular truncated cone with a narrow upper part and a wide lower part. Its upper part is tightly connected to the double-hole casting funnel 3, and its lower part has the same size as the plate-shaped water-cooled copper mold 1 and the two are aligned and installed. The outer wall of the heat-insulating riser 2 is made of cast iron, and the interior is made of a mixture of magnesia sand and water glass. Magnesia sand acts as a binder. The heat-insulating riser 2 can improve the feeding efficiency of the ingot solidification.

[0067] To buffer and distribute the molten steel, the double-hole casting funnel 3 of the present invention includes a concave channel 32 and a first funnel and a second funnel located on both sides of the concave channel 32; the bottom of the first funnel is provided with a first funnel outlet 31; the bottom of the second funnel is provided with a second funnel outlet; during casting, the molten steel flows through the concave channel 32 and enters the casting cavity 14 of the plate-shaped water-cooled copper mold 1 through the first funnel outlet 31 and the second funnel outlet.

[0068] Specifically, the first funnel and the second funnel of the present invention have the same structure and are symmetrically arranged. The concave channel 32 is located in the middle of the two. The molten steel smelted by the vacuum induction furnace is buffered and distributed by the concave channel 32 and enters the first funnel and the second funnel respectively. It then enters the casting cavity 14 through the outlet 31 of the first funnel and the outlet of the second round hole funnel.

[0069] Compared with the prior art, the present invention uses a double-hole casting funnel 3, which can play a role in buffering the molten steel during the casting process.

[0070] It should be noted that the first funnel outlet 31 and the second funnel outlet of the present invention are located at one-quarter and three-quarters of the length of the double-hole casting funnel 3, respectively; the concave channel 32 is located at the middle position of the length of the double-hole casting funnel 3. In addition, the double-hole casting funnel 3 is made of magnesium, which has high temperature resistance and good thermal stability.

[0071] Compared with the prior art, the present invention pours molten steel into the ingot mold through a double-hole pouring funnel 3, so that the molten steel flows and solidifies quickly and evenly in the ingot mold, which can reduce segregation.

[0072] It should be noted that the first funnel outlet 31 and the second funnel outlet are both circular holes with a diameter of 24-26 mm.

[0073] This invention also provides a novel ingot mold method for nitrogen-controlled silicon steel plate-shaped ingots, employing the aforementioned novel ingot mold device for nitrogen-controlled silicon steel plate-shaped ingots; the ingot mold method includes the following steps:

[0074] Step 1: Place the vacuum induction melting ingot mold device at the bottom of the vacuum induction furnace at the molten steel outlet;

[0075] Step 2: Load materials into the vacuum induction furnace and perform vacuum smelting to obtain molten steel;

[0076] In step 1 above, before smelting in the vacuum induction furnace, industrial pure iron is first added to the magnesium crucible for iron washing. After the iron washing is completed, the raw materials are proportioned according to the target composition of the new nitrogen-controlled silicon steel and in combination with various metals or alloys and element yields. Depending on the timing of the addition, the raw materials of industrial pure iron, photoelectric carbon, high-purity silicon, metallic copper, metallic tin, and iron sulfide are loaded into the crucible, and the raw materials of aluminum granules, manganese-nitrogen alloy, and metallic bismuth are added to the secondary feeding box.

[0077] In step 1 above, the mechanical pump and the Roots pump are turned on in sequence to draw a multi-stage vacuum system. When the vacuum degree in the furnace is lower than 10 Pa, the electric vacuum induction melting is started. The electric vacuum induction melting includes three stages: melting period, refining period, and alloying period. The smelting tasks of melting raw materials, refining and degassing, stirring molten steel, and adding alloy materials are completed according to the melting requirements. Inert gas is introduced for protection, and the electric power is adjusted to make the temperature of molten steel reach the tapping temperature.

[0078] In step 1 above, the components of the novel nitrogen-controlled silicon steel, by weight percentage, include: C: 0.05-0.07 wt.%, Si: 0.8-1.2 wt.%, Mn: 0.12-0.16 wt.%, Al: 0.02-0.03 wt.%, N: 0.020-0.028 wt.%, S: 0.008-0.012 wt.%, Cu: 0.1-0.12 wt.%, Sn: 0.1-0.12 wt.%, Bi: 0.002-0.006 wt.%, with the balance being Fe and unavoidable impurities.

[0079] Step 3: Pour the molten steel through the double-hole pouring funnel 3 into the cavity containing the molten steel and ingots to complete the casting process;

[0080] In step 3 above, after the vacuum induction melting is completed, the electromagnetic stirrer 4 of the plate-shaped water-cooled copper mold 1 is turned on, and the electric power is adjusted so that the temperature of the molten steel reaches a high superheat temperature. Then the crucible is tilted to start pouring, and the molten steel enters the plate-shaped water-cooled copper mold 1 through the double-hole pouring funnel 3 and the heat preservation riser 2.

[0081] In step 3 above, the temperature difference between the inlet and outlet of the cooling water is 2–3°C, and the cooling water flow rate is 40–80 m³ / h. 3 / h, Cooling capacity (kW) = Cooling water flow rate (m³ / h) 3 / h)×Specific heat capacity of water (kJ / kg·℃)×Temperature difference (℃);The specific heat capacity of water is usually 4.186kJ / kg·℃;The cooling capacity of water-cooled copper mold is 335kW~1005kW.

[0082] Step 4: Cool the furnace for 1-2 hours under inert gas protection, open the ingot mold device, demold the ingot, and obtain a plate-shaped ingot.

[0083] In step 4 above, the electromagnetic stirrer 4 outside the plate-shaped water-cooled copper mold 1 is turned on to the preset stirring frequency of 20-60Hz, the melting crucible is slowly tilted, and the casting begins. The molten steel is poured into the cavity of the plate-shaped water-cooled copper mold 1 through the double-hole pouring funnel 3 and the heat-insulating riser 2, and the casting is completed.

[0084] In step 4 above, the furnace is cooled for 1 to 2 hours under inert gas protection. The furnace body vent valve is opened to release the air, the cooling water is turned off, the double-hole casting funnel 3 and the heat preservation riser 2 are removed in sequence, and the plate-shaped water-cooled copper mold 1 and the plate-shaped ingot are taken out of the furnace. The fastening clamps and the rectangular water-cooled panel 12 are disassembled to remove the ingot.

[0085] In summary, this invention utilizes the strong cooling effect of cooling water to rapidly solidify molten steel, and the high superheated molten steel quickly replenishes and eliminates macroscopic defects caused by internal porosity and shrinkage. Furthermore, the electromagnetic stirring action eliminates the segregation of alloying elements (electromagnetic stirring can increase the equiaxed grain ratio of the billet and refine the solidification structure, thus significantly reducing the segregation of alloying elements).

[0086] The ingot mold device and method of the present invention are mainly designed for melting new nitrogen-controlled silicon steel plate-shaped metal ingots in a 10-50kg vacuum induction furnace (ZLG type), and are suitable for reducing solidification defects of plate-shaped ingots and improving their metallurgical quality.

[0087] Example 1

[0088] This embodiment provides a novel ingot mold device and method for nitrogen-controlled silicon steel slab casting, used in a ZGL type 50kg vacuum induction furnace to smelt novel oriented silicon steel (nitrogen content in the steel ranges from 0.012 to 0.016 wt.%) and complete the slab casting operation. It includes the following steps:

[0089] Step 1: Place the ingot mold device at the bottom of the vacuum induction furnace at the molten steel outlet;

[0090] Two rectangular water-cooled panels 12 and two plate-shaped electromagnetic stirrers are fixed to both sides of the U-shaped water-cooled side sealing plate 11 using two sets of upper and lower fastening clamps, thus completing the installation of the plate-shaped water-cooled copper mold 1. Then, the installed plate-shaped water-cooled copper mold 1 is moved to a suitable position in the vacuum induction furnace using an overhead crane. Next, the cooling water inlet and outlet pipes of the U-shaped water-cooled side sealing plate 11 and the two rectangular water-cooled panels 12, as well as the external wiring of the two plate-shaped electromagnetic stirrers, are connected. Finally, the heat-insulating riser 2 is installed directly above the plate-shaped water-cooled copper mold 1, and the double-hole casting funnel 3 is installed above the heat-insulating riser 2. Thus, the overall installation of the ingot mold device is completed.

[0091] Step 2: Load materials into the vacuum induction furnace and perform vacuum smelting to obtain molten steel;

[0092] Before smelting in a vacuum induction furnace, industrial pure iron is added to the magnesium crucible for iron washing to ensure that the crucible is clean and to prevent impurities in the crucible from contaminating the smelted steel materials.

[0093] With a furnace charge of 15 kg and based on the target composition of the new silicon steel (by mass percentage, containing 0.06% C, 1.2% Si, 0.15% Mn, 0.010% S, 0.025% Al, 0.021% N, 0.002% Bi, 0.1% Sn, 0.1% Cu, with the remainder being Fe), the furnace charge of industrial pure iron and various alloy raw materials was calculated. 14.85 kg of industrial pure iron, 165 g of high-purity silicon, 1 g of iron sulfide, 15 g of metallic tin, and 15 g of metallic copper were loaded into the bottom of the smelting crucible. 10 g of manganese-nitrogen alloy (nitrogen content approximately 15 wt.%), 6 g of electrolytic manganese, 4 g of metallic aluminum granules, and 7 g of photoelectric carbon were loaded into the material box at the top of the vacuum induction furnace.

[0094] The vacuum smelting process includes: Step 21, closing the vacuum induction furnace lid and sequentially opening each level of the furnace's vacuum system to evacuate to a vacuum level less than 0.5 Pa; Step 22, turning on the power supply and gradually increasing the vacuum induction furnace's power from the initial 20 kW to 60 kW to induction heat the raw materials inside the melting crucible, initiating the melting period smelting, which lasts for 0.75 hours; Step 23, ending the melting period and beginning the refining period smelting, reducing the power supply. During the refining period, the power is maintained at 50kW. The temperature of the molten steel is monitored in real time by a non-contact optical thermometer above the inspection hole of the vacuum induction furnace cover. The power is dynamically adjusted to maintain the temperature of the molten steel at 1600℃. The refining period lasts for 0.25 hours. In step 24, after the refining period ends, the alloying period begins. The power is reduced to 45kW, and 0.02MPa argon gas is introduced as a protective gas. The alloy raw materials inside the material box at the top of the vacuum induction furnace are added to the molten steel inside the melting crucible and kept at that temperature for 5 minutes.

[0095] Step 3: Pour the molten steel through the double-hole pouring funnel 3 into the cavity containing the molten steel and ingots to complete the casting process;

[0096] Turn on the cooling water system of plate-shaped water-cooled copper mold 1, and adjust the cooling water inlet temperature and flow rate to the set values ​​(inlet water temperature 25℃, inlet water flow rate 35m). 3 / h), turn on the power switch of the electromagnetic stirrer 4 and adjust its frequency to 30Hz; adjust the input power, the temperature of the molten steel is 1530℃, slowly tilt the melting crucible in the furnace to start pouring, the molten steel accurately flows through the concave channel 32 in the middle of the double-hole pouring funnel 3 to the first funnel outlet 31 and the second funnel outlet on both sides, and passes through the heat preservation riser 2 into the casting cavity 14 of the plate-shaped water-cooled copper mold 1. The molten steel solidifies rapidly into a plate-shaped billet under the action of cooling water and electromagnetic stirring.

[0097] Step 4: Cool the furnace for 1.5 hours under inert gas protection, open the ingot mold device, demold the ingot, and obtain a plate-shaped ingot.

[0098] After maintaining the vacuum argon-filled conditions for 1 hour, the cooling water of the plate-shaped water-cooled copper mold 1 and the power switch of the electromagnetic stirrer 4 are turned off. The furnace body vent valve is opened to release the air. The double-hole pouring funnel 3 and the heat preservation riser 2 are removed. The plate-shaped water-cooled copper mold 1 is taken out and disassembled using an overhead crane. The demolding operation is completed. At this time, the work of smelting 15kg of new silicon steel plate-shaped billets in the vacuum induction furnace is completed.

[0099] The slab-shaped cast billet was longitudinally cut open, and the cross-section showed no porosity or cracks. Low-magnification microstructure analysis was performed to statistically determine the grain size and Mn element segregation coefficient. The results are shown in Table 1. The microstructure of the cast grains under an optical microscope is as follows: Figure 4 As shown.

[0100] Example 2

[0101] This embodiment provides a novel ingot mold device and method for nitrogen-controlled silicon steel slab casting, used in a ZGL type 50kg vacuum induction furnace to smelt novel oriented silicon steel (nitrogen content in the steel ranges from 0.012 to 0.016 wt.%) and complete the slab casting operation. It includes the following steps:

[0102] Step 1: Place the ingot mold device at the bottom of the vacuum induction furnace at the molten steel outlet;

[0103] Two rectangular water-cooled panels 12 and two plate-shaped electromagnetic stirrers are fixed to both sides of the U-shaped water-cooled side sealing plate 11 using two sets of upper and lower fastening clamps, thus completing the installation of the plate-shaped water-cooled copper mold 1. Then, the installed plate-shaped water-cooled copper mold 1 is moved to a suitable position in the vacuum induction furnace using an overhead crane. Next, the cooling water inlet and outlet pipes of the U-shaped water-cooled side sealing plate 11 and the two rectangular water-cooled panels 12, as well as the external wiring of the two plate-shaped electromagnetic stirrers, are connected. Finally, the heat-insulating riser 2 is installed directly above the plate-shaped water-cooled copper mold 1, and the double-hole casting funnel 3 is installed above the heat-insulating riser 2. Thus, the overall installation of the ingot mold device is completed.

[0104] Step 2: Load materials into the vacuum induction furnace and perform vacuum smelting to obtain molten steel;

[0105] Before smelting in a vacuum induction furnace, industrial pure iron is added to the magnesium crucible for iron washing to ensure that the crucible is clean and to prevent impurities in the crucible from contaminating the smelted steel materials.

[0106] The furnace charge of industrial pure iron and various alloy raw materials was calculated based on a furnace charge of 15 kg and the target composition of the new silicon steel (by mass percentage, containing 0.06% C, 1.2% Si, 0.15% Mn, 0.010% S, 0.025% Al, 0.027% N, 0.004% Bi, 0.1% Sn, 0.1% Cu, with the remainder being Fe).

[0107] The vacuum smelting process includes: Step 21, closing the vacuum induction furnace lid and sequentially opening each level of the furnace's vacuum system to evacuate to a vacuum level less than 0.5 Pa; Step 22, turning on the power supply and gradually increasing the vacuum induction furnace's power from the initial 20 kW to 60 kW to induction heat the raw materials inside the melting crucible, initiating the melting period smelting, which lasts for 0.75 hours; Step 23, ending the melting period and beginning the refining period smelting, reducing the power supply. During the refining period, the power is maintained at 55kW. The temperature of the molten steel is monitored in real time by a non-contact optical thermometer above the inspection hole of the vacuum induction furnace cover. The power is dynamically adjusted to maintain the temperature of the molten steel at 1610℃. The refining period lasts for 0.25 hours. In step 24, after the refining period ends, the alloying period begins. The power is reduced to 45kW, and 0.02MPa argon gas is introduced as a protective gas. The alloy raw materials inside the material box at the top of the vacuum induction furnace are added to the molten steel inside the melting crucible and kept at that temperature for 5 minutes.

[0108] Step 3: Pour the molten steel through the double-hole pouring funnel 3 into the cavity containing the molten steel and ingots to complete the casting process;

[0109] Turn on the cooling water system of plate-shaped water-cooled copper mold 1, and adjust the cooling water inlet temperature and flow rate to the set values ​​(inlet water temperature 25℃, inlet water flow rate 50m). 3 / h), turn on the power switch of the electromagnetic stirrer 4 and adjust its frequency to 40Hz; adjust the input power, the temperature of the molten steel is 1550℃, slowly tilt the melting crucible in the furnace to start pouring, the molten steel accurately flows through the concave channel 32 in the middle of the double-hole pouring funnel 3 to the first funnel outlet 31 and the second funnel outlet on both sides, and passes through the heat preservation riser 2 into the casting cavity 14 of the plate-shaped water-cooled copper mold 1. The molten steel solidifies rapidly into a plate-shaped billet under the action of cooling water and electromagnetic stirring.

[0110] Step 4: Cool the furnace for 2 hours under inert gas protection, open the ingot mold device, demold the ingot, and obtain a plate-shaped ingot.

[0111] After maintaining the vacuum argon-filled conditions for 1 hour, the cooling water of the plate-shaped water-cooled copper mold 1 and the power switch of the electromagnetic stirrer 4 are turned off. The furnace body vent valve is opened to release the air. The double-hole pouring funnel 3 and the heat preservation riser 2 are removed. The plate-shaped water-cooled copper mold 1 is taken out and disassembled using an overhead crane. The demolding operation is completed. At this time, the work of smelting 15kg of new silicon steel plate-shaped billets in the vacuum induction furnace is completed.

[0112] The slab-shaped billet was longitudinally cut, and the average grain size, macroscopic defects, and Mn element segregation coefficient of the billet are shown in Table 1. The microstructure of the as-cast grains under an optical microscope is shown in... Figure 7 As shown.

[0113] Comparative Example 1

[0114] Comparative Example 1 is basically the same as Example 1, except that the power switch of the electromagnetic stirrer 4 was not turned on in step 3, that is, electromagnetic stirring was not performed during the solidification of the molten steel. Similarly, the cast billet obtained in Comparative Example 1 was characterized and analyzed in the same way as in Example 1, and the results are shown in Table 1. The microstructure of the as-cast grains under an optical microscope is as follows: Figure 5 As shown.

[0115] Comparative Example 2

[0116] Comparative Example 2 is essentially the same as Example 1, except that in step 2, a waterless cast iron ingot mold with the same billet geometry is used instead of the plate-shaped water-cooled copper mold 1 device in this invention, and the operation of the ingot mold using the ingot mold device of this invention in step 3 is omitted. Similarly, the billet obtained in Comparative Example 2 is subjected to the same characterization analysis as in Example 1, and the results are shown in Table 1. The microstructure of the as-cast grains under an optical microscope is as follows: Figure 6 As shown.

[0117] Table 1. Characterization analysis results of cast billets in the examples and comparative examples.

[0118]

[0119] Through Examples 1 and 2, as well as two comparative examples, it was found that using a plate-shaped water-cooled copper mold 1 equipped with an electromagnetic stirrer 4 to complete the casting operation of the novel nitrogen-controlled silicon steel material effectively refines the as-cast grain size and reduces the possibility of nitrogen precipitation and escape causing porosity in the billet due to reduced nitrogen solubility. Furthermore, while ensuring smooth casting, it effectively shortens the local cooling time of the alloy, reduces the non-equilibrium solidification diffusion kinetic energy of segregated elements in the steel, and improves the uniformity of alloy element distribution.

[0120] In summary, the ingot mold device and method for novel nitrogen-controlled silicon steel slab ingots provided by this invention are suitable for vacuum smelting and casting in the laboratory development stage of new steel grades such as new silicon steel. By using high-intensity water cooling and electromagnetic stirring, the molten steel is rapidly solidified, resulting in slab ingots with fine grains and high density. This is helpful for the development of new oriented silicon steel materials. The slab ingots with good metallurgical quality can be directly connected to subsequent hot rolling process research.

[0121] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A novel ingot mold device for nitrogen-controlled silicon steel plate-shaped ingots, characterized in that, The ingot mold device is located at the steel molten outlet of the vacuum induction device; the ingot mold device includes a plate-shaped water-cooled copper mold, an insulated riser, a double-hole casting funnel, and an electromagnetic stirrer. The insulating riser is located above the plate-shaped water-cooled copper mold, and the two are aligned and their inner cavities are connected; the double-hole casting funnel is located above the insulating riser, and the two are aligned and connected, and their inner cavities are connected; the electromagnetic stirrer is located on the outside of the plate-shaped water-cooled copper mold. The double-hole casting funnel includes a concave casting channel and a first funnel and a second funnel located on both sides of the concave casting channel; the bottom of the first funnel is provided with a first funnel outlet; the bottom of the second funnel is provided with a second funnel outlet; During casting, the molten steel flows through the concave channel and enters the casting cavity of the plate-shaped water-cooled copper mold through the outlets of the first and second funnels; The first funnel outlet and the second funnel outlet are located at one-quarter and three-quarters of the length of the double-hole casting funnel, respectively; the concave channel is located at the middle position of the length of the double-hole casting funnel. The plate-shaped water-cooled copper mold includes a U-shaped water-cooled side sealing plate and a first rectangular water-cooled panel and a second rectangular water-cooled panel with the same structure. The first rectangular water-cooled panel and the second rectangular water-cooled panel are arranged parallel to each other on both sides of the U-shaped water-cooled side sealing plate, and their bottoms are connected to the bottom plate of the U-shaped water-cooled side sealing plate; the area enclosed by the three together constitutes a casting cavity for holding molten steel and ingots. The electromagnetic stirrer includes a first plate-shaped electromagnetic stirrer and a second plate-shaped electromagnetic stirrer. The first plate-shaped electromagnetic stirrer is located on the outside of the first rectangular water-cooled panel; the second plate-shaped electromagnetic stirrer is located on the outside of the second rectangular water-cooled panel; the first plate-shaped electromagnetic stirrer and the second plate-shaped electromagnetic stirrer are used to form a uniform magnetic field in the casting cavity to stir the molten steel. Both the first plate-shaped electromagnetic stirrer and the second plate-shaped electromagnetic stirrer are double-sided traveling wave magnetic field stirrers with an energizing frequency of 20~60 Hz. The novel nitrogen-controlled silicon steel plate-shaped ingot can be directly rolled and heat-treated without the need for forging.

2. The ingot mold device for the novel nitrogen-controlled silicon steel plate-shaped ingot according to claim 1, characterized in that, The ingot mold device also includes two sets of upper and lower fastening clamps with the same structure. The fastening clamp includes a U-shaped clamp body; both ends of the U-shaped clamp body are provided with threaded holes and bolts; The fastening clamps are used to fix the first rectangular water-cooled panel and the second rectangular water-cooled panel to the two sides of the U-shaped water-cooled side sealing plate.

3. The ingot mold device for the novel nitrogen-controlled silicon steel plate-shaped ingot according to claim 2, characterized in that, Both the first funnel outlet and the second funnel outlet are circular holes; The diameters of the outlets of the first and second funnels are both 25-30 mm.

4. The ingot mold device for the novel nitrogen-controlled silicon steel plate-shaped ingot according to claim 1, characterized in that, The shape of the heat-insulating riser is a hollow rectangular frustum; The insulating riser is used to improve the feeding efficiency of ingot solidification.

5. The ingot mold device for the novel nitrogen-controlled silicon steel plate-shaped ingot according to claim 4, characterized in that, The outer wall of the insulating riser is made of cast iron, and its inner wall is made of a mixture of magnesia and water glass.

6. A novel ingot mold method for nitrogen-controlled silicon steel plate-shaped ingots, employing the ingot mold device for the novel nitrogen-controlled silicon steel plate-shaped ingots as described in any one of claims 1 to 5; the ingot mold method includes the following steps: Step 1: Place the ingot mold device at the bottom of the vacuum induction furnace; Step 2: Load materials into the vacuum induction device and smelt them to obtain molten steel; Step 3: Pour the molten steel through the double-hole casting funnel into the inner cavity containing the molten steel and ingot, thus completing the casting process; Step 4: Cool the furnace for 1-2 hours under inert gas protection, open the ingot mold device, demold the ingot, and obtain a plate-shaped ingot.

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