Heat preservation ingot mold for improving solidification quality of large cast ingot
By introducing composite hollow insulation boards and refractory clay to fill the gaps in large steel ingot molds, and combining this with electromagnetic control technology, the problems of shrinkage cavities and porosity defects during the solidification process of large steel ingots were solved, thus improving the solidification quality of the ingots.
Patent Information
- Application Number
- CN202423278760.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-27
- Publication Date
- 2026-01-27
- Estimated Expiration
- 2034-12-27
AI Technical Summary
Large steel ingots are prone to shrinkage cavities, porosity and segregation defects during solidification, especially when the height-to-diameter ratio increases. Existing technologies are unable to effectively mitigate or eliminate these defects.
A heat-insulating steel ingot mold was designed, including the steel ingot mold body, a false riser, an ingot body insulation board, a riser insulation board, and an outer insulation layer. Composite hollow insulation board and refractory clay are used to fill the gaps, and electromagnetic control technology is combined to improve the heat preservation effect during the solidification process.
It effectively mitigates or even eliminates shrinkage defects inside steel ingots, improving the solidification quality of large P92 steel ingots.
Smart Images
Figure CN223833411U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of steel casting equipment, specifically relating to a heat-insulating steel ingot mold for improving the solidification quality of large ingots. Background Technology
[0002] There are many factors that affect the solidification quality of large steel ingots, which can be roughly divided into three aspects: First, process factors, including chemical composition, casting temperature, casting speed, casting method, whether and how much heat-insulating agent is used; second, mold factors, mainly including the structural design of the small base, steel ingot mold and riser; and third, heat-insulating factors, including the application of heat-insulating boards and heat-generating agents and whether or not external heat-insulating technology for steel ingot molds is used.
[0003] For the solidification process of large steel ingots, different height-to-diameter ratios have a significant impact. As the height-to-diameter ratio increases, the cooling capacity of the ingot mold increases significantly, making the ingot highly susceptible to defects such as shrinkage cavities, porosity, and segregation. Current research has found that electromagnetic control technology at the ingot riser can effectively mitigate or even eliminate segregation after solidification. However, the addition of the electromagnetic field causes the cooling rate of the riser to exceed that of the ingot body, easily leading to secondary shrinkage cavities in the ingot body. For large ingots of low-carbon, high-alloy steel like P92, the higher alloy content results in a greater tendency for internal shrinkage. Once the mold is filled with molten steel, the temperature of the molten steel continuously decreases due to the cooling effect of the mold. The upper surface of the molten steel is in contact with the external environment for heat transfer, while other parts are in contact with the mold and cooled. As solidification progresses, the rapid cooling of the mold and molten steel causes the molten steel in contact to quickly form a shell and undergo solidification shrinkage. At this stage, the upper surface of the molten steel is not yet solidified, causing the steel-to-molten steel interface to gradually descend. As solidification continues, when the temperature of the upper surface of the molten steel drops to the solidus temperature, a shell layer forms, and the upper surface of the ingot stops descending. As solidification time progresses, the solidification front of the molten steel continues to advance into the ingot. The undried molten steel undergoes liquid shrinkage as the temperature decreases, while the solidified shell undergoes solid-state shrinkage due to the decreasing temperature. Since the sum of liquid and solidification shrinkage is greater than solid-state shrinkage, under the influence of gravity, the undried molten steel detaches from the solidified shell below the primary shrinkage cavity, forming a secondary shrinkage cavity. In the later stages of ingot solidification, the final liquid phase region solidifies almost simultaneously, resulting in severe porosity due to lack of replenishment from the surrounding liquid. To reduce the impact of these defects on the solidification quality of the ingot, improving the heat preservation effect is particularly important for the quality of the ingot solidification process. Utility Model Content
[0004] The purpose of this invention is to provide a heat-insulating steel ingot mold that improves the solidification quality of large ingots, which can provide heat insulation for the molten steel inside the ingot mold and improve the solidification quality of large P92 steel ingots.
[0005] The technical solution is as follows:
[0006] A heat-insulating steel ingot mold for improving the solidification quality of large ingots includes: a steel ingot mold body and a false riser. The top opening of the steel ingot mold body and the bottom opening of the false riser are located at the top opening of the steel ingot mold body. The steel ingot mold body 1 has multiple risers on its upper and lower side walls and a vent at the bottom. The inner wall of the steel ingot mold body below the upper riser is provided with an ingot body insulation plate, and a heat-insulating cavity is provided in the middle of the ingot body insulation plate. The inner wall of the steel ingot mold body at the riser is provided with a riser insulation plate, which is a composite hollow insulation plate. The composite hollow insulation plate includes: a working layer, a hollow insulation layer, and a heat-insulating layer. The hollow insulation layer is located in the middle, and the heat-insulating layer is wrapped around the outside of the hollow insulation layer. The working layer is wrapped around the outside of the heat-insulating layer.
[0007] Furthermore, the inner wall of the malfunctioning part is equipped with a malfunctioning part insulation plate.
[0008] Furthermore, a first positioning hook is provided on the inner wall of the steel ingot mold body, and the ingot body insulation plate is fixed to the inner wall of the steel ingot mold body through the first positioning hook. The gap between the ingot body insulation plates is filled with refractory clay.
[0009] Furthermore, a second positioning hook is provided on the inner wall of the ingot mold body at the riser. The riser insulation plate is fixed to the inner wall of the ingot mold body by the second positioning hook, and the gap between the riser insulation plates is filled with refractory clay.
[0010] Furthermore, a third positioning hook is provided on the inner wall of the sprue, and the sprue insulation board is fixed to the inner wall of the sprue by the third positioning hook. The gaps between the sprue insulation boards are filled with refractory mortar.
[0011] Furthermore, the riser insulation plate extends above the upper edge of the ingot mold body, and the false riser is connected and fixed to the ingot mold body by a positioning and locking mechanism.
[0012] Furthermore, an external insulation layer is provided on the outer wall of the ingot mold body of the riser.
[0013] This utility model has the following advantages compared with the prior art:
[0014] This invention can provide heat preservation for molten steel inside the ingot mold. In the process of casting steel ingots, based on the control of molten steel temperature, casting speed and electromagnetic regulation of riser during solidification, it further enhances the heat preservation effect during solidification, effectively reduces or even completely eliminates shrinkage defects inside the steel ingot, improves the solidification quality of molten steel, and improves the solidification quality of large P92 steel ingots. Attached Figure Description
[0015] Figure 1 This is a schematic diagram of the longitudinal section structure of the front of the heat-insulating steel ingot mold for improving the solidification quality of large ingots in this utility model.
[0016] Figure 2 This is a schematic diagram of the longitudinal section of the side of the heat-insulating steel ingot mold for improving the solidification quality of large ingots in this utility model. Detailed Implementation
[0017] The following description fully illustrates specific embodiments of the present invention to enable those skilled in the art to practice and reproduce it.
[0018] like Figure 1 The image shown is a schematic diagram of the longitudinal section of the front of the heat-insulating steel ingot mold for improving the solidification quality of large ingots in this utility model; as shown... Figure 2 The image shown is a schematic diagram of the longitudinal section of the side of the heat-insulating steel ingot mold for improving the solidification quality of large P92 steel ingots in this utility model.
[0019] The steel ingots prepared by the heat-insulating steel ingot mold are all 17t ingots, which are a combination mold of cast iron steel ingot mold and stainless steel riser. The height-to-diameter ratio of the steel ingot is 2.7, which is much larger than the normal height-to-diameter ratio of steel ingot.
[0020] A heat-insulating steel ingot mold for improving the solidification quality of large ingots includes: a steel ingot mold body 1 and a false riser 2. The top opening of the steel ingot mold body 1 and the bottom opening of the false riser 2 are provided at the top opening of the steel ingot mold body 1. Multiple risers 11 are provided on the side wall of the steel ingot mold body 1 and a vent 12 is provided at the bottom. An ingot body heat insulation plate 13 is provided on the inner wall of the steel ingot mold body 1 below the riser 11.
[0021] The steel ingot mold body 1 has multiple risers 11 on the upper and lower side walls, and the inner wall of the steel ingot mold body 1 at the upper riser 11 is provided with an ingot body heat insulation plate 13.
[0022] The main materials of the ingot body insulation plate 13 are clay clinker, expanded lightweight material, diatomaceous earth, composite organic fiber, and composite binder, with an insulating cavity in the middle. A first positioning hook is provided on the inner wall of the ingot mold body 1, and the ingot body insulation plate 13 is fixed to the inner wall of the ingot mold body 1 by the first positioning hook. The first positioning hook is used to prevent the ingot body insulation plate 13 from falling off during the casting process. The gaps between the ingot body insulation plates 13 are filled with refractory clay to prevent steel penetration and affect the surface quality of the ingot.
[0023] To reduce heat dissipation at riser 11, a riser insulation plate 14 is installed on the inner wall of the ingot mold body 1 at riser 11. A second positioning hook is provided on the inner wall of the ingot mold body 1 at riser 11, and the riser insulation plate 14 is fixed to the inner wall of the ingot mold body 1 by the second positioning hook. The second positioning hook is used to prevent the riser insulation plate 14 from falling off during the casting process. The gaps between the riser insulation plates 14 are filled with refractory clay to prevent steel penetration and affect the surface quality of the ingot.
[0024] The riser insulation plate 14 extends 20mm above the upper edge of the ingot mold body 1, allowing this portion of the riser insulation plate 14 to be inserted into the stainless steel dummy riser 2. The dummy riser 2 and the ingot mold body 1 are connected and fixed by a positioning and locking mechanism 3. This prevents the connection between the dummy riser 2 and the ingot mold body 1 from penetrating the steel during the pouring process.
[0025] The riser insulation board 14 is a composite hollow insulation board with a thermal conductivity of 0.17 [W / (m·K)] / 1000℃. The fire resistance of the working layer of the composite hollow insulation board is ≥1700℃, the fire resistance of the insulation layer of the composite hollow insulation board is ≥1580℃, and the bulk density is ≤0.9kg / dm³. 3 .
[0026] The composite hollow insulation panel comprises a working layer, a hollow insulation layer, and a thermal insulation layer. The hollow insulation layer is located in the middle, and the thermal insulation layer wraps around the outside of the hollow insulation layer. The working layer wraps around the outside of the thermal insulation layer, forming a composite structure. The working layer is mainly composed of fused magnesia and other materials; the thermal insulation layer is mainly composed of clay clinker, expanded lightweight material, diatomaceous earth, composite organic fiber, and composite binder. The working layer is at least 20mm thick to prevent it from being "punctured" by high-temperature molten steel. During hot stripping, the hollow insulation panel is designed to completely separate from riser 11.
[0027] The area where the false riser 2 is located is within the electromagnetic field zone. To reduce heat dissipation at the false riser 2, a false riser insulation plate 21 is installed on the inner wall of the false riser 2. A third positioning hook is provided on the inner wall of the false riser 2, and the false riser insulation plate 21 is fixed to the inner wall of the false riser 2 by the third positioning hook. The third positioning hook is used to prevent the false riser insulation plate 21 from falling off during the casting process. The gaps between the false riser insulation plates 21 are filled with refractory clay to prevent steel penetration and affect the surface quality of the steel ingot.
[0028] An external insulation layer 15 is provided on the outer wall of the steel ingot mold body 1 outside the riser 11. The external insulation layer 15 is made of 50mm thick aluminum silicate insulation cotton, which wraps the area of riser 11. The thermal conductivity of aluminum silicate should be 0.03-0.045W / (m·K).
[0029] Insulation steel ingot mold usage process:
[0030] Large P92 steel ingots are made of low-carbon, high-alloy P92 steel. The composition, by mass percentage, is as follows: C: 0.07%-0.13%, Mn: 0.30%-0.60%, Si≤0.50%, S≤0.010%, P≤0.020%, Cr: 8.50%-9.50%, Ni≤0.40%, Mo: 0.30%-0.60%, V: 0.15%-0.25%, Al≤0.020%, Nb: 0.04%-0.09%, N: 0.030%-0.070%, W: 1.50%-2.00%, B: 0.001%-0.006%, with the remainder being iron.
[0031] Its smelting process is as follows: non-vacuum induction furnace → VOD furnace oxygen blowing and decarburization → LF furnace → VD furnace → ingot casting; the specific steps are:
[0032] 1. Preliminary smelting is carried out in a non-vacuum induction furnace. Steel scraps, cut ends, and pure iron of low-carbon high-alloy P92 steel are loaded into the furnace in proportion and smelted and melted. Among them, steel scraps account for 60% and cut ends account for 40% of the returned material.
[0033] 2. When charging the induction furnace, first load steel scrap into 5-7 bags. Then, use a magnetic disk to hoist the cut-off pieces or pure iron. This method can effectively avoid bridging. After the initial charging is completed, increase the power of the medium-frequency furnace to 1500kw for preheating for 10-15 minutes. Gradually increase the power to 6000kw. During this period, additional charge can be added according to the melting of the furnace charge. Add 35-55kg of carbonizing agent. After all the furnace charge has been added and melted to form a liquid surface, add carbonized rice husks to keep the liquid surface warm. Increase the power to 8000kw and heat up. When the temperature reaches 1650-1670℃, tap out the steel. Add 120-140kg of aluminum balls with the steel stream.
[0034] 3. After tapping, the ladle is transferred to the VOD furnace station. The temperature upon entry is above 1625℃. After temperature measurement and sampling, it enters the vacuum decarburization stage. After VOD completion, lime and aluminum balls are added in two batches at the VOD station for reduction. The first batch adds 1000-1500 kg of lime and 400-500 kg of aluminum balls; the second batch adds 1000-1500 kg of lime and 100-300 kg of aluminum balls. After the addition is complete, samples are taken to analyze the aluminum content, and then slag turning is performed according to the slag layer thickness.
[0035] 4. After slag removal, the slag is transferred to the LF furnace for slag formation. Ferrosilicon powder, calcium carbide, and quicklime are added to ensure that the FeO content in the slag is ≤0.6%, the basicity is 3-5, and then the alloy is adjusted. The refining time is greater than 40 minutes. After LF refining is completed, the slag is moved to the VD station.
[0036] 5. At the start of VD (Vacuum Deposition), observe the argon flow rate and exhaust gas temperature increase during pump injection. To prevent slag spillage, a slow vacuum pump injection can be adopted, ensuring a vacuum degree ≤0.5 Torr and a time ≥20 minutes. When the vacuum output H ≤2.0ppm, O ≤7ppm, and the temperature reaches 1590℃, nitrogen adjustment is performed, with an argon flow rate of 14-16 Nm3 / h. Ferrochromium nitride is added in batches, with each addition not exceeding 150kg. The ferroboron injection operation should be performed after nitrogen adjustment, and an aluminum or iron container should be inserted into the molten steel. Finally, the quaternary slow-release magnesium-aluminum alloy cored wire operation is performed, ensuring that the aluminum content is 0.016-0.018%. After completion, soft blowing is performed to ensure that the molten steel is not exposed to air for 20-25 minutes, followed by a 10-minute settling time.
[0037] 6. Measure the temperature before hoisting the ladle. The temperature of the molten steel should be between 1570-1580℃. Cover the ladle with carbonized rice husks. After hoisting the ladle, it can be directly loaded onto the truck for pouring.
[0038] 7. Argon gas protection is used for the entire casting process. Molten steel enters the inner cavity of the ingot mold body 1 from riser 11. To prevent secondary oxidation of the molten steel, the protective slag is suspended during the casting process to ensure that the molten steel is not exposed. After the casting is completed, 80kg of carbonized rice husks are added to the ingot in time and the composite hollow heat insulation cover is covered.
[0039] 8. After all the pouring work is completed, apply electromagnetic control at the false riser 2 until the steel ingot is completely solidified and demolded.
[0040] 9. After the steel ingot is demolded, it is slowly cooled. After slow cooling, the steel ingot is longitudinally cut along the center line. The solidification quality of the steel ingot is evaluated by low-magnification corrosion.
[0041] After the steel ingot solidifies and anneales, it is longitudinally cut and sampled along the center line. The solidification is good and the shrinkage crack defect is completely eliminated, which shows that the patented technology has a good effect on improving the solidification structure.
[0042] The terminology used in this invention is descriptive and exemplary, and not restrictive. Since this invention can be embodied in various forms without departing from the spirit or essence of the technical solution, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims. Therefore, all variations and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.
Claims
1. A heat-insulating steel ingot mold for improving the solidification quality of large ingots, characterized in that, include: The ingot mold body and the false riser are described. The top opening of the ingot mold body and the bottom opening of the false riser are described. The false riser is located at the top opening of the ingot mold body. The ingot mold body has multiple risers on its upper and lower side walls and a vent at the bottom. The inner wall of the ingot mold body below the upper riser is provided with an ingot body insulation plate, and the middle of the ingot body insulation plate is provided with a heat insulation cavity. The inner wall of the ingot mold body at the riser is provided with a riser insulation plate, which is a composite hollow insulation plate. The composite hollow insulation plate includes a working layer, a hollow insulation layer, and a heat insulation layer. The hollow insulation layer is located in the middle, the heat insulation layer is wrapped around the outside of the hollow insulation layer, and the working layer is wrapped around the outside of the heat insulation layer.
2. The heat-insulating steel ingot mold for improving the solidification quality of large ingots as described in claim 1, characterized in that, The inner wall of the sprue is equipped with a sprue insulation plate.
3. The heat-insulating steel ingot mold for improving the solidification quality of large ingots as described in claim 1, characterized in that, The inner wall of the steel ingot mold body is provided with a first positioning hook, and the ingot body insulation plate is fixed to the inner wall of the steel ingot mold body through the first positioning hook. The gap between the ingot body insulation plates is filled with refractory clay.
4. The heat-insulating steel ingot mold for improving the solidification quality of large ingots as described in claim 1, characterized in that, A second positioning hook is provided on the inner wall of the ingot mold body at the riser. The riser insulation plate is fixed to the inner wall of the ingot mold body by the second positioning hook. The gap between the riser insulation plates is filled with refractory clay.
5. The heat-insulating steel ingot mold for improving the solidification quality of large ingots as described in claim 2, characterized in that, The inner wall of the sprue is provided with a third positioning hook, and the sprue insulation board is fixed to the inner wall of the sprue by the third positioning hook. The gap between the sprue insulation boards is filled with refractory mortar.
6. The heat-insulating steel ingot mold for improving the solidification quality of large ingots as described in claim 1, characterized in that, The riser insulation plate extends above the upper edge of the ingot mold body, and the false riser is connected and fixed to the ingot mold body by a positioning and locking mechanism.
7. The heat-insulating steel ingot mold for improving the solidification quality of large ingots as described in claim 1, characterized in that, An external insulation layer is provided on the outer wall of the ingot mold body of the riser.