A method for improving steel ingot yield using high-temperature CO2 gas

Abstract

This invention belongs to the field of die casting in metallurgical processes, and particularly relates to a method for improving steel ingot yield using high-temperature CO2 gas. The method includes: 1) filling the steel ingot mold and runner with high-temperature CO2 before casting, and preheating the mold and runner to 400-700°C; 2) during casting, after the molten steel enters the ingot mold, the interior of the mold is a sealed space filled with CO2 atmosphere, and the CO2 heated by the molten steel is circulated back to the heat exchange furnace. No protective slag or heating agent is used during the casting process; 3) after casting, during the solidification process of the steel ingot, the high-temperature CO2 gas in the heat exchange furnace is used to replenish the CO2 gas in the ingot mold, resulting in slow solidification of the steel ingot and sufficient riser feeding. The advantages are: using high-temperature CO2 gas as an isolation, heat transfer, and insulation medium, and through a closed circulating heat exchange system, precise temperature and atmosphere control are achieved during the casting and solidification process of the steel ingot. By optimizing feeding and reducing waste, the steel ingot yield can be increased to over 90%.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical casting, and particularly relates to a method for improving steel ingot yield by utilizing high-temperature CO2 gas. Background Technology

[0002] With the continuous advancement of industrialization, equipment used in the engineering field is becoming increasingly larger and heavier. The demand for large forgings is growing, and the quality requirements for forgings are also becoming increasingly stringent. Large forged steel ingots are the raw materials used to process forgings, and their quality is particularly important to the final forging quality. However, the solidification process of steel ingots inevitably encounters difficulties in solidification feeding. These obstacles can promote porosity and shrinkage cavities within the ingot, and the larger the ingot and the greater its height-to-diameter ratio, the more difficult the solidification feeding becomes. To ensure the quality of the ingot itself, most companies choose to remove the feeding portion from the riser, which affects the ingot yield. Currently, the yield of steel ingots for most companies is around 85%.

[0003] To address the problem of ingot feeding, various methods have been employed, such as using exothermic agents, resistance heating, or graphite electrode heating at the riser to delay the solidification of the molten steel. External physical fields have also been used to promote feeding during the ingot solidification process. However, practice has shown that these traditional methods have limited effectiveness in improving yield, increasing it by only about 2% to 3%, and have failed to solve the problem. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, the purpose of this invention is to provide a method for improving steel ingot yield by utilizing high-temperature CO2 gas. By adjusting the temperature of the CO2 gas, the heat loss of molten steel is minimized, achieving slow solidification of the molten steel, allowing the steel ingot to shrink sufficiently, isolating it from air, minimizing oxidation, eliminating the need for risers, protective slag, and heating agents, and thus improving steel ingot yield.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for improving steel ingot yield using high-temperature CO2 gas includes the following steps: 1) Before pouring, fill the ingot mold and runner with high-temperature CO2 and preheat the ingot mold and runner to 400~700℃ for 10~30 minutes; before pouring, use CO2 to purge the air from the ingot mold to form an inert atmosphere and a sealed space to minimize the secondary oxidation of the molten steel. 2) When the molten steel enters the ingot mold during casting, the inside of the ingot mold is a closed space filled with CO2 atmosphere. The heat of the molten steel is absorbed by CO2, which heats it to 1600~1800℃. The heated CO2 is then circulated back to the heat exchange furnace, where the temperature of the CO2 gas reaches above 1800℃. No protective slag or heating agent is used during the casting process. 3) After casting, the CO2 temperature above the riser is 1700~1900℃. During the solidification process of the steel ingot, the high-temperature CO2 gas in the heat exchange furnace is used to supplement the CO2 gas in the steel ingot mold, causing the steel ingot to solidify slowly and ensuring sufficient feeding from the riser. This slow and thorough solidification of the steel ingot ensures that the feeding effect of the riser is maximized, effectively reducing defects such as shrinkage cavities. The continuous supplementary heating in the riser area using high-temperature CO2 gas at 1700~1900℃ replaces traditional exothermic agents and protective slag.

[0006] The heat exchanger includes a preheating chamber, a regenerator chamber, a heating chamber, a final heating module, and a return gas storage module. The preheating chamber, regenerator chamber, and heating chamber are connected by pipes. The preheating chamber is connected to a CO2 inlet pipe. The final heating module is located inside the heating chamber and is connected to the ingot mold. The return gas storage module is located inside the preheating chamber and is connected to the ingot mold. The final heating module and the return gas storage module are connected by pipes. The return gas storage module is connected to a CO2 return gas pipe. A CO2 filling pipe connects the final heating module and the ingot mold. A sealing ring is installed between the heat exchanger and the ingot mold.

[0007] The preheating chamber, heat storage chamber, and heating chamber are all equipped with heating and pressure holding modules, and the heating and pressure holding module in the heating chamber is connected to the final heating module.

[0008] The final heating module is equipped with a pressure measuring device and a temperature measuring device.

[0009] The method for improving steel ingot yield using the aforementioned heat exchange furnace includes the following steps: 1) Place the heat exchange furnace above the steel ingot mold. CO2 gas enters through the CO2 inlet pipe, passes through the preheating chamber, heat storage chamber, and heating chamber, and is heated and stored in the final heating module. After meeting the operating temperature and pressure, CO2 gas is introduced into the steel ingot mold to expel the air in the steel ingot mold and the gating system, and to preheat the steel ingot mold and the gating system. 2) Move the ladle above the central injection pipe, ready to begin pouring; Before pouring, close the CO2 inflation pipe and open the CO2 return pipe; The pouring process begins. Molten steel enters the ingot mold from the bottom through the central pouring pipe and the gating channel, heating the CO2 inside the ingot mold. The heated CO2 is squeezed by the molten steel and enters the return gas storage module through the CO2 return gas pipe. No protective slag or heating agent is used in the pouring process. After casting, during the solidification process of the steel ingot, the pipe connecting the final heating module and the return gas storage module is opened. The high-temperature CO2 gas in the return gas storage module is charged into the final heating module, and then sent to the steel ingot mold for reheating by the final heating module; the pressure and temperature of the CO2 gas above the steel ingot mold are detected. 3) 1.5 to 2.5 hours after the casting is completed, close the CO2 charging pipe and the CO2 return pipe, and seal the unused CO2 gas in the heating and pressure holding modules of the heat exchange furnace preheating chamber, heat storage chamber and heating chamber for reuse in the next casting. At the same time, remove the heat exchange furnace and allow the steel ingot mold to cool naturally.

[0010] The heat exchange furnace is equipped with a pressure measuring device and a temperature measuring device on the outside, which are used to detect the pressure and temperature of the steel ingot mold.

[0011] Compared with the prior art, the beneficial effects of the present invention are: This invention utilizes high-temperature CO2 gas as an isolation, heat transfer, and insulation medium, and achieves precise temperature and atmosphere control during the casting and solidification of steel ingots through a closed-loop circulating heat exchange system. By optimizing feeding and reducing waste, the steel ingot yield is increased to over 90%.

[0012] This invention utilizes a heat exchange furnace to fill the steel ingot mold with high-temperature CO2 before casting, preheating it while isolating it from air to minimize oxidation. The heated CO2 can be circulated back to the heat exchange furnace, eliminating the need for risers and ensuring sufficient ingot shrinkage. It also eliminates the need for protective slag and heating agents, effectively reducing heat loss from the molten steel, minimizing secondary oxidation, and increasing ingot yield. By adjusting the CO2 gas temperature, slow solidification of the molten steel is achieved, ensuring sufficient ingot shrinkage and increasing the ingot yield to over 90%, while also realizing the resource utilization of CO2. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of the present invention.

[0014] Figure 2 This is a schematic diagram of the heating furnace.

[0015] In the diagram: 1. Ingot mold; 2. Sprue; 3. Injection pipe; 4. Ladle; 5. Heat exchanger furnace; 51. Preheating chamber; 52. Regenerator chamber; 53. Heating chamber; 54. CO2 inlet pipe; 55. CO2 filling pipe; 56. CO2 return pipe; 57. Pressure measuring device and temperature measuring device; 58. Final heating module; 59. Return gas storage module; Area A is the preheating route; Area B is the heating route. Detailed Implementation

[0016] The present invention will now be described in detail with reference to the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0017] A method for improving steel ingot yield using high-temperature CO2 gas includes the following steps: 1) Before pouring, fill the steel ingot mold 1 and the sprue 2 with high temperature CO2 and preheat the steel ingot mold 1 and the sprue 2 to 400~700℃ for 10~30 minutes; before pouring, use CO2 to purge the air in the steel ingot mold 1 to form an inert atmosphere sealed space to minimize the secondary oxidation of the molten steel. 2) When the molten steel enters the ingot mold 1 during casting, the inside of the ingot mold 1 is a closed space filled with CO2 atmosphere. The heat of the molten steel is absorbed by CO2, which heats it to 1600~1800℃. The heated CO2 is then circulated back to the heat exchange furnace 5. The temperature of the CO2 gas in the heat exchange furnace 5 reaches above 1800℃. No protective slag or heating agent is used during the casting process. 3) After casting, the CO2 temperature above the riser is 1700~1900℃. During the solidification process of the steel ingot, the high-temperature CO2 gas in heat exchange furnace 5 is used to supplement the CO2 gas in the steel ingot mold 1, causing the steel ingot to solidify slowly and ensuring sufficient feeding from the riser. This slow and thorough solidification of the steel ingot ensures that the feeding effect of the riser is maximized, effectively reducing defects such as shrinkage cavities. The continuous supplementary heating in the riser area using high-temperature CO2 gas at 1700~1900℃ replaces traditional heating agents and protective slag.

[0018] See Figure 1 , Figure 2 The heat exchanger 5 includes a preheating chamber 51, a regenerator chamber 52, a heating chamber 53, a final heating module 58, and a return gas storage module 59. The preheating chamber 51, regenerator chamber 52, and heating chamber 53 are connected by pipes. The preheating chamber 51 is connected to a CO2 inlet pipe 54. The final heating module 58 is located within the heating chamber 53 and is connected to the ingot mold 1. The return gas storage module 59 is located within the preheating chamber 51 and is connected to the ingot mold 1. The final heating module 58 and the return gas storage module 59 are connected by pipes. The return gas storage module 59 is connected to a CO2 return gas pipe 56. A CO2 charging pipe 55 connects the final heating module 58 and the ingot mold 1. A sealing ring is arranged between the heat exchanger 5 and the ingot mold 1. Each of the preheating chamber 51, regenerator chamber 52, and heating chamber 53 is equipped with at least one heating and pressure holding module. The heating and pressure holding module in the heating chamber 53 is connected to the final heating module 58. The target temperature and pressure are achieved through a multi-stage heating and pressure-holding module. These modules are connected by pipes and equipped with control valves. The preheating chamber 51 has a temperature limit of 700℃, the heat storage chamber 52 has a temperature limit of 1000℃, and the heating chamber 53 has a temperature limit of 1400℃. The pressure values ​​of each heating and pressure-holding module are set according to usage requirements to ensure sufficient gas supply.

[0019] The final heating module 58 is connected to a pressure measuring device and a temperature measuring device 57. The heat exchange furnace 5 is equipped with a pressure measuring device and a temperature measuring device 57 on the outside, which are used to detect the pressure and temperature of the steel ingot mold 1.

[0020] See Figure 1 , Figure 2 The method for improving steel ingot yield using high-temperature CO2 gas achieved by the aforementioned heat exchanger furnace 5 specifically includes the following steps: 1) Arrange the steel ingot mold 1, gating system 2, and central injection pipe 3 in the pit according to production requirements, such as... Figure 1 As shown. The heat exchange furnace 5 is placed above the steel ingot mold 1. CO2 gas travels along the preheating route A. The CO2 gas enters through the CO2 inlet pipe 54, passes through the preheating chamber 51, the heat storage chamber 52, and the heating chamber 53, and is heated and stored in the final heating module 58. After meeting the operating temperature and pressure, CO2 gas is introduced into the steel ingot mold 1 to expel the air in the steel ingot mold 1 and the gating system 2, and to preheat the steel ingot mold 1 and the gating system 2. The preheating temperature is 400~700℃, and the preheating time is 10~30 minutes. The preheated CO2 gas is discharged from the central injection pipe 3 and can be collected and recovered by the CO2 storage tank.

[0021] 2) Move the ladle 4 above the central injection pipe 3, ready to start pouring; Before pouring, close the CO2 charging pipe 55 and open the CO2 return pipe 56. The pouring process begins. Molten steel enters the ingot mold 1 from the bottom through the central pouring pipe 3 and the gating channel 2. The inside of the ingot mold 1 is a sealed space filled with CO2 atmosphere. The heat of the molten steel is absorbed by the CO2, which heats the CO2 inside the ingot mold 1 to 1600~1800℃. The heated CO2 is squeezed by the molten steel and enters the return gas storage module 59 through the CO2 return gas pipe 56. No protective slag or heating agent is used in the pouring process. After casting, the CO2 temperature above the molten steel is between 1700 and 1900℃. During the solidification process of the ingot, following heating route B, the pipe connecting the final heating module 58 and the return gas storage module 59 is opened. The high-temperature CO2 gas in the return gas storage module 59 is then introduced into the final heating module 58, and then sent to the ingot mold 1 for reheating. This minimizes heat loss and ensures more complete solidification of the molten steel. The pressure and temperature of the CO2 gas above the ingot mold 1 are monitored, and the CO2 gas temperature above the ingot mold 1 must be maintained above 1300℃.

[0022] 3) 1.5 to 2.5 hours after the casting is completed, close the CO2 charging pipe 55 and the CO2 return pipe 56 to seal the unused CO2 gas in the heating and pressure holding module in the preheating chamber 51, heat storage chamber 52 and heating chamber 53 of the heat exchange furnace 5. The gas can be used again in the next casting. At the same time, remove the heat exchange furnace 5 to allow the steel ingot mold 1 to cool naturally.

[0023] This invention constructs a closed-loop CO2 gas circulation system, which recovers the high-temperature CO2 that absorbs heat from molten steel to the heat exchange furnace 5 for reheating, thus achieving efficient energy recovery and utilization.

[0024] Example 1: A 11.5-ton steel ingot was cast, with a casting time of 12 minutes and a total steel volume of 13 tons. Before casting, CO2 gas at 1000°C was introduced to preheat the ingot mold and runner to 500°C for 13 minutes. After the molten steel entered the mold, the CO2 temperature was raised to 1300°C. As more molten steel entered the mold, the CO2 gas inside was heated to 1650°C. After casting, the CO2 gas temperature above the molten steel was 1860°C. One hour later, the CO2 gas temperature above the molten steel was measured at 1554°C. After complete solidification, the weight of the ingot obtained by removing the solidification shrinkage portion was 11.8 tons, resulting in an ingot yield of 11.8 / 13 = 90.7%.

[0025] Example 2: A 23-ton steel ingot was cast, with a casting time of 16 minutes and a total steel volume of 26 tons. Before casting, CO2 gas at 1150°C was introduced to preheat the ingot mold and runner to 480°C for 9 minutes. After the molten steel entered the mold, the CO2 temperature was raised to 1350°C. As more molten steel entered the mold, the CO2 gas inside was heated to 1670°C. After casting, the CO2 gas temperature above the molten steel was 1872°C. One hour later, the CO2 gas temperature above the molten steel was measured at 1576°C. After complete solidification, the weight of the ingot obtained after removing the solidification shrinkage portion was 23.5 tons. The ingot yield was 23.5 / 26 = 90.4%.

[0026] Example 3: A 36-ton steel ingot was cast, with a casting time of 22 minutes and a steel volume of 40 tons. Before casting, CO2 gas at 1260°C was introduced to preheat the ingot mold and runner to 550°C for 18 minutes. After the molten steel entered the mold, the CO2 temperature was raised to 1360°C. As more molten steel entered the mold, the CO2 gas inside was heated to 1720°C. After casting, the CO2 gas temperature above the molten steel was 1906°C. One hour later, the CO2 gas temperature above the molten steel was measured at 1540°C. After complete solidification, the weight of the ingot obtained after removing the solidification shrinkage portion was 36.5 tons. The ingot yield was 36.5 / 40 = 91.3%.

[0027] This invention utilizes a heat exchange furnace to fill the steel ingot mold with high-temperature CO2 before casting, preheating it while isolating it from air to minimize oxidation. The heated CO2 can be circulated back to the heat exchange furnace, eliminating the need for risers and ensuring sufficient ingot shrinkage. It also eliminates the need for protective slag and heating agents, effectively reducing heat loss from the molten steel, minimizing secondary oxidation, and increasing ingot yield. By adjusting the CO2 gas temperature, slow solidification of the molten steel is achieved, ensuring sufficient ingot shrinkage and increasing the ingot yield to over 90%, while also realizing the resource utilization of CO2.

Claims

1. A method for improving steel ingot yield using high-temperature CO2 gas, characterized in that, Includes the following steps: 1) Before casting, fill the steel ingot mold and runner with high temperature CO2, and preheat the steel ingot mold and runner to 400~700℃ for 10~30 minutes; 2) When the molten steel enters the ingot mold during casting, the inside of the ingot mold is a closed space filled with CO2 atmosphere. The heat of the molten steel is absorbed by CO2, which heats it to 1600~1800℃. The heated CO2 is then circulated back to the heat exchange furnace, where the temperature of the CO2 gas reaches above 1800℃. No protective slag or heating agent is used during the casting process. 3) After casting, the CO2 temperature above the riser is 1700~1900℃. During the solidification of the steel ingot, the high-temperature CO2 gas in the heat exchange furnace is used to supplement the CO2 gas in the steel ingot mold, and the steel ingot solidifies slowly, and the riser feeds the ingot fully.

2. The method for improving steel ingot yield using high-temperature CO2 gas according to claim 1, characterized in that, The heat exchanger includes a preheating chamber, a regenerator chamber, a heating chamber, a final heating module, and a return gas storage module. The preheating chamber, regenerator chamber, and heating chamber are connected by pipes. The preheating chamber is connected to a CO2 inlet pipe. The final heating module is located in the heating chamber and is connected to the steel ingot mold. The return gas storage module is located in the preheating chamber and is connected to the steel ingot mold. The final heating module and the return gas storage module are connected by pipes. The return gas storage module is connected to a CO2 return gas pipe. A CO2 filling pipe connects the final heating module and the steel ingot mold.

3. The method for improving steel ingot yield using high-temperature CO2 gas according to claim 2, characterized in that, The preheating chamber, heat storage chamber, and heating chamber are all equipped with heating and pressure holding modules, and the heating and pressure holding module in the heating chamber is connected to the final heating module.

4. The method for improving steel ingot yield using high-temperature CO2 gas according to claim 2, characterized in that, The final heating module is equipped with a pressure measuring device and a temperature measuring device.

5. The method for improving steel ingot yield using high-temperature CO2 gas according to claim 2, characterized in that, The method for improving steel ingot yield using the aforementioned heat exchange furnace includes the following steps: 1) Place the heat exchange furnace above the steel ingot mold. CO2 gas enters through the CO2 inlet pipe, passes through the preheating chamber, heat storage chamber, and heating chamber, and is heated and stored in the final heating module. After meeting the operating temperature and pressure, CO2 gas is introduced into the steel ingot mold to expel the air in the steel ingot mold and the gating system, and to preheat the steel ingot mold and the gating system. 2) Move the ladle above the central injection pipe, ready to begin pouring; Before pouring, close the CO2 inflation pipe and open the CO2 return pipe; The pouring process begins. Molten steel enters the ingot mold from the bottom through the central pouring pipe and the gating channel, heating the CO2 inside the ingot mold. The heated CO2 is squeezed by the molten steel and enters the return gas storage module through the CO2 return gas pipe. No protective slag or heating agent is used in the pouring process. After casting, during the solidification process of the steel ingot, the pipe connecting the final heating module and the return gas storage module is opened. The high-temperature CO2 gas in the return gas storage module is charged into the final heating module, and then sent to the steel ingot mold for reheating by the final heating module; the pressure and temperature of the CO2 gas above the steel ingot mold are detected. 3) 1.5 to 2.5 hours after the casting is completed, close the CO2 charging pipe and the CO2 return pipe, and seal the unused CO2 gas in the heating and pressure holding modules of the heat exchange furnace preheating chamber, heat storage chamber and heating chamber for reuse in the next casting. At the same time, remove the heat exchange furnace and allow the steel ingot mold to cool naturally.

6. The method for improving steel ingot yield using high-temperature CO2 gas according to claim 1, characterized in that, The heat exchange furnace is equipped with a pressure measuring device and a temperature measuring device on the outside, which are used to detect the pressure and temperature of the steel ingot mold.

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