Process method for improving quality of high-aluminum alloy steel for injection molding machine

Abstract

The invention belongs to the technical field of high aluminum alloy steel production, and relates to a process method for improving the quality of high aluminum alloy steel for an injection molding machine. The high-aluminum alloy steel continuous casting billet (1) passes through the first roller set (2), two first pressing rollers (3) of the first roller set (2) are located on the upper portion and the lower portion of the high-aluminum alloy steel continuous casting billet (1), the surface temperature of the first pressing rollers (3) of the first roller set (2) is larger than or equal to 850 DEG C, the first pressing rollers (3) on the upper portion apply pressure to the high-aluminum alloy steel continuous casting billet (1), the pressure is controlled to range from 7 Mpa to 10 Mpa, and the high-aluminum alloy steel continuous casting billet (1) is obtained. Residual incompletely-solidified molten steel in the core of the high-aluminum alloy steel continuous casting billet (1) is discharged through pressure, the center of the casting billet deforms, and center shrinkage cavities and press-fit looseness are relieved; according to the process, the quality of the continuous casting billet is improved, the flaw detection qualification rate of the forging material is increased, the investment cost is low, only the production procedures are locally adjusted, the product quality improvement effect is obvious, the number of scrapped forging material products is reduced, economic losses are reduced, the product performance further meets the product requirements of customers, and the product quality is improved.

Description

Technical Field

[0001] This invention belongs to the field of high-aluminum alloy steel production technology, and more specifically, it relates to a process method for improving the quality of high-aluminum alloy steel used in injection molding machines. Background Technology

[0002] 38CrMoAl is a high-grade nitrided alloy structural steel that holds an important position in industry due to its excellent comprehensive properties. Containing alloying elements such as chromium, molybdenum, and aluminum, it achieves extremely high surface hardness, excellent wear resistance, and high fatigue strength after nitriding treatment. It also possesses good heat resistance and corrosion resistance. These properties make it ideal for manufacturing critical components in injection molding machines that require high wear resistance, high precision, and high fatigue strength, such as screws and barrels. Traditional technology uses a die-casting-forging production process. However, feedback from downstream forging manufacturers indicates that the current yield rate of forged products is low, leading to increased production costs and hindering product diversification.

[0003] Existing technology includes a method for producing ferrochromium-aluminum alloy continuously cast slabs, titled "Production Method of Ferrochromium-Aluminum Alloy Continuous Casting Slabs," with publication (announcement) number "CN111424134A." This method discloses a production method for ferrochromium-aluminum alloy continuously cast slabs, wherein: during ladle casting, the ladle nozzle is opened directly without oxygen blowing; the composition of the refractory lining of the continuous casting tundish is controlled by mass percentage as follows: SiO2: 0.01%–5.0%, Fe2O3: 0.01%–1.50%, with the remainder being MgO; the composition of the covering agent of the continuous casting tundish is controlled by mass percentage as follows: SiO2: 0.01%–5.0%, Al2O3: 0.03%–1.80%, Fe2O3: 0.01%–1.50%, CaO: 0.01%–4.0%, MnO: 0.01%–0.03%. The composition of the protective slag in the continuous casting mold is as follows: 1%, Na2O: 0.01%–1.0%, C: 5.0%–9.0%, moisture: 0.01%–1.2%, and the remainder is MgO. The basicity R of the protective slag in the continuous casting mold is controlled at 0.5–0.8, and the composition of the protective slag by mass percentage is controlled as follows: C: 6.0%–8.5%, Al2O3: 1.2%–3.50%, Na2O: 8%–11.5%, F−: 6.0%–11.5%, Li2O: 3.0%–6.5%, MgO: 0.5%–2.0%, and the remainder is CaO and SiO2. The surface of the continuous casting billet is hot-ground. Before grinding, the surface temperature of the continuous casting billet is controlled at 100℃–700℃, and after grinding, the surface temperature of the continuous casting billet is controlled at greater than or equal to 50℃. The grinding weight loss rate is controlled at 0.2%–8%. However, this technology does not address the technical problems and solutions of this application. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a process method for improving the quality of high-aluminum alloy steel for injection molding machines, which is simple in steps, reduces the central shrinkage cavity and the porosity of the pressing, and improves the quality of the cast billet by solving the problem of low inspection qualification of forging materials and improving the quality of the product.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: This invention relates to a process method for improving the quality of high-aluminum alloy steel used in injection molding machines. S1. The high-alumina alloy steel continuous casting billet passes through the first roll group. The two first pressure rolls 3 of the first roll group are located at the upper and lower parts of the high-alumina alloy steel continuous casting billet. The surface temperature of the first pressure roll of the first roll group is ≥850℃. The upper first pressure roll applies pressure to the high-alumina alloy steel continuous casting billet. The pressure is controlled at 7Mpa-10Mpa. The pressure causes the residual unsolidified molten steel in the core of the high-alumina alloy steel continuous casting billet to be discharged, and the center of the billet is deformed, reducing the central shrinkage cavity and the looseness of the compression. S2. The high-alumina alloy steel continuous casting billet passes through the second roll group. The two second pressure rollers 5 of the second roll group are located at the upper and lower parts of the high-alumina alloy steel continuous casting billet. The surface temperature of the second pressure rollers of the second roll group is ≥830℃. The upper second pressure roller applies pressure to the high-alumina alloy steel continuous casting billet. The pressure is controlled at 7Mpa-10Mpa. The pressure consolidates the deformation of the high-alumina alloy steel continuous casting billet and prevents springback. S3. The high-alumina alloy steel continuous casting billet passing through the second roll group is slowly cooled for ≥60 hours. The temperature before slow cooling is ≥600℃ and the temperature after slow cooling is ≤150℃.

[0006] The end shaft of the first pressure roller at the bottom of the first roller group is installed on the first frame near the bottom. A motor is installed on the first frame and drives the first pressure roller. The end shaft of the first pressure roller at the top of the first roller group is connected to the first lifting cylinder, which is connected to the first frame near the top.

[0007] The end shaft of the second pressure roller at the bottom of the second roller group is installed on the second frame near the bottom. A motor is installed on the second frame and drives the second pressure roller. The end shaft of the second pressure roller at the top of the second roller group is connected to the second lifting cylinder, which is connected to the second frame near the top.

[0008] The production process for improving the quality of high-aluminum alloy steel used in injection molding machines includes the following steps in sequence: converter process → LF refining process → RH vacuum degassing process → continuous casting process → roller pressing process → slow cooling process → forging process.

[0009] In the converter process, no silicon-containing raw materials are used. High manganese, high carbon ferrochrome, and ferromolybdenum are added to the ladle when tapping the steel. The tapping end temperature is 1500℃-1525℃. The steel composition requirements are: C≥0.08% and P≤0.012%.

[0010] In the LF refining process, the refining time is >50 min, the white slag retention time is >20 min, and the use of silicon-containing auxiliary materials is strictly prohibited; the soft blowing time is ≥30 min, and the [H] at the station is ≤2 ppm, and [O] is <15 ppm.

[0011] In the continuous casting process of the continuous casting machine, the superheat is controlled at 30-40℃ and the casting speed is 0.2m / min-0.3m / min.

[0012] In the continuous casting process of the continuous casting machine, the water flow rate in the crystallizer is controlled at 3600L / min, the water flow rate in the secondary cooling system is controlled at 0.12L / Kg, the initial stirring is controlled at 150A / 2HZ, the secondary cooling electric stirring is controlled at 350A / 3HZ, and the final stirring is controlled at 1100A / 4HZ.

[0013] In the forging process, if defects are found in the core of the continuously cast billet after sawing, they need to be repaired by welding.

[0014] The working principle and beneficial effects of the technical solution adopted in this invention are as follows: The present invention describes a process method for improving the quality of high-aluminum alloy steel used in injection molding machines. This method involves setting up a first roller group and a second roller group. The high-aluminum alloy steel continuously cast billet, after processing in the continuous casting process, sequentially passes through the first and second roller groups. Static pressure is applied to the high-aluminum alloy steel continuously cast billet by the first and second roller groups, respectively. In this way, based on the solidification characteristics of the 38CrMoAl steel continuous casting process and combined with the tooling equipment of the continuous casting process, the process flow is adjusted, key process control points are controlled, and external pressure is applied at the end of the billet solidification stage. This causes residual incompletely solidified molten steel in the billet core to be discharged, resulting in deformation of the billet center and a denser solidified structure in the core. This solves the defects such as central porosity, shrinkage cavities, and cracks caused by incomplete billet feeding under the original process. In terms of billet quality improvement, it addresses the problem of low inspection pass rates for forging materials, thus achieving an overall quality improvement. Attached Figure Description

[0015] The following is a brief explanation of the contents depicted in the accompanying drawings and the markings therein: Figure 1 This is a schematic diagram of the roller assembly structure of the process method for improving the quality of high-aluminum alloy steel for injection molding machines according to the present invention; Figure 2 This is a schematic diagram of the roller assembly structure of the process method for improving the quality of high-aluminum alloy steel for injection molding machines according to the present invention; Figure 3 This is a partial structural diagram of a circular continuously cast billet processed by a roller assembly in the process method for improving the quality of high-aluminum alloy steel for injection molding machines according to the present invention. The labels in the attached diagram are as follows: 1. High-alumina alloy steel continuous casting billet; 2. First roll group; 3. First pressure roll; 4. Second roll group; 5. Second pressure roll; 6. First frame; 7. First lifting cylinder; 8. Second frame; 9. Second lifting cylinder. Detailed Implementation

[0016] The following description, with reference to the accompanying drawings, provides a more detailed explanation of the specific embodiments of the present invention, including the shape and structure of each component, the relative positions and connections between the parts, the functions and working principles of each part: As attached Figure 1 -Appendix Figure 3As shown, this invention is a process method for improving the quality of high-aluminum alloy steel used in injection molding machines. S1. The high-aluminum alloy steel continuous casting billet 1 passes through a first roller group 2. The two first pressure rollers 3 of the first roller group 2 are located at the upper and lower parts of the high-aluminum alloy steel continuous casting billet 1. The surface temperature of the first pressure rollers 3 of the first roller group 2 is ≥850℃. The upper first pressure roller 3 applies pressure to the high-aluminum alloy steel continuous casting billet 1, with the pressure controlled at 7MPa-10MPa. This pressure causes the residual incompletely solidified molten steel in the core of the high-aluminum alloy steel continuous casting billet 1 to be discharged, resulting in central deformation of the billet and reducing central shrinkage cavities and compression porosity; S2. High... The aluminum alloy steel continuous casting billet 1 passes through the second roller group 4. The two second pressure rollers 5 of the second roller group 4 are located above and below the high-aluminum alloy steel continuous casting billet 1. The surface temperature of the second pressure rollers 5 of the second roller group 4 is ≥830℃. The upper second pressure roller 5 applies pressure to the high-aluminum alloy steel continuous casting billet 1, with the pressure controlled between 7MPa and 10MPa. This pressure consolidates the deformation of the high-aluminum alloy steel continuous casting billet 1 and prevents springback. S3. The high-aluminum alloy steel continuous casting billet passing through the second roller group 4 undergoes slow cooling for ≥60 hours. The temperature before slow cooling is ≥600℃, and the temperature after slow cooling is ≤150℃. To address the shortcomings of the existing technology, an improved technical solution is proposed. In the structural setup, a first roller group 2 and a second roller group 4 are set up. The high-aluminum alloy steel continuous casting billet 1, after continuous casting, passes sequentially through the first roller group 2 and the second roller group 4. The first roller group 2 and the second roller group 4 apply static pressure to the high-aluminum alloy steel continuous casting billet 1, respectively. In this way, based on the solidification characteristics of the continuous casting process of 38CrMoAl steel and combined with the tooling equipment of the continuous casting process, the process flow is adjusted, key process control points are controlled, and external pressure is applied at the end of the solidification of the continuously cast billet. This causes the residual incompletely solidified molten steel in the core of the billet to be discharged, resulting in deformation of the billet center and a more compact core structure. This solves the defects such as central porosity, shrinkage cavities, and cracks caused by incomplete feeding of the billet under the original process. It also addresses the problem of low forging inspection pass rates in terms of billet quality improvement, achieving an overall quality improvement. This invention improves the forging inspection pass rate by increasing the quality of continuously cast billets, with low investment costs. It only involves local adjustments to the production process, resulting in a significant improvement in product quality, reducing the number of scrapped forgings, minimizing economic losses, and further meeting customer requirements for product performance, thus improving product quality.

[0017] The end shaft of the first pressure roller 3 at the lower part of the first roller group 2 is mounted on the first frame 6 near the lower part. A motor is mounted on the first frame 6, and the motor drives the first pressure roller 3. The end shaft of the first pressure roller 3 at the upper part of the first roller group 2 is connected to the first lifting cylinder 7, which is connected to the first frame 6 near the upper part. In this structure, the motor drives the lower first pressure roller to rotate, and the first pressure roller applies pressure to the surface of the high-alumina alloy steel continuous casting billet 1 at the end of solidification. This causes the residual incompletely solidified molten steel in the core of the billet to be discharged, resulting in deformation of the billet center and a denser solidified structure in the core. This solves the defects such as central porosity, shrinkage cavities, and cracks caused by incomplete feeding of the billet under the original process. The upper first pressure roller can also be connected to a motor, which is mounted on the first frame. In this way, the pressure rollers of the first roller group can both rotate and apply pressure.

[0018] The high-alumina alloy steel continuous casting billet described in this invention is either a plate-shaped continuous casting billet or a round continuous casting billet. Regardless of the type of continuous casting billet, the pressure rollers can apply external force to the continuous casting billet from above and below.

[0019] The end shaft of the second pressure roller 5 at the lower part of the second roller group 4 is mounted on the second frame 8 near the lower part. A motor is mounted on the second frame 8, and the motor drives the second pressure roller 5. The end shaft of the second pressure roller 5 at the upper part of the second roller group 4 is connected to the second lifting cylinder 9, which is connected to the second frame 8 near the upper part. In this structure, the motor drives the lower second pressure roller to rotate, and the second pressure roller applies pressure to the surface of the high-alumina alloy steel continuous casting billet 1 at the end of solidification. This causes the residual incompletely solidified molten steel in the core of the billet to be discharged, resulting in deformation of the billet center and making the core solidification structure more compact. This solves the defects such as central porosity, shrinkage cavities, and cracks caused by incomplete feeding of the billet under the original process. The upper second pressure roller can also be connected to a motor, which is mounted on the first frame. In this way, the pressure rollers of the second roller group can both rotate and apply pressure. The more important purpose of the second roller group is to prevent the continuous casting billet from springing back after the first pressure roller applies force.

[0020] The production process for improving the quality of high-aluminum alloy steel used in injection molding machines includes the following steps: converter process → LF refining process → RH vacuum degassing process → continuous casting process → roller pressing process → slow cooling process → forging process. In the converter process, silicon-containing raw materials are not used. High-manganese, high-carbon ferrochrome, and ferromolybdenum are added to the ladle during tapping. The tapping temperature is between 1500℃ and 1525℃, and the steel composition requirements are: C ≥ 0.08%, P ≤ 0.012%, thus improving the quality of the tapped steel.

[0021] In the LF refining process, the refining time must be >50 min, the white slag retention time must be >20 min, and the use of silicon-containing auxiliary materials is strictly prohibited; the soft blowing time must be ≥30 min, and the outgoing [H] ≤2 ppm, [O] <15 ppm. In the above steps, "outgoing [H] ≤2 ppm, [O] <15 ppm" refers to the control requirements for hydrogen and oxygen concentrations during gas emission or treatment. Specifically: Outgoing [H] ≤2 ppm: This means that the concentration of hydrogen (H2) in the emitted gas must not exceed 2 ppm (parts per million), that is, the volume of hydrogen in every 1 million volumes of emitted gas must not exceed 2 volumes. [O] <15 ppm: This means that the concentration of oxygen (O2) in the emitted gas must be below 15 ppm (parts per million), that is, the volume of oxygen in every 1 million volumes of emitted gas must be less than 15 volumes.

[0022] In the continuous casting process, the superheat is controlled at 30-40℃, and the casting speed is 0.2 m / min-0.3 m / min. The crystallizer water flow rate is controlled at 3600 L / min, the secondary cooling water flow rate is controlled at 0.12 L / kg, the initial stirring is controlled at 150 A / 2 Hz, the secondary cooling electric stirring is controlled at 350 A / 3 Hz, and the final stirring is controlled at 1100 A / 4 Hz. In the above steps: 1. Casting speed definition: The speed at which the billet is pulled from the crystallizer during continuous casting, measured in meters per minute (m / min). Function: Directly affects production efficiency and billet quality. Excessive casting speed may result in an excessively thin billet shell, increasing the risk of steel leakage; excessively slow casting speed reduces production efficiency. 2. Crystallizer water flow rate definition: The consumption of cooling water in the crystallizer, usually measured in tons per hour (t / h). Function: Cools the molten steel in the crystallizer, forming a sufficiently strong billet shell to prevent steel leakage. 3. **Second Cooling Water Quantity** Definition: The ratio of water consumption per unit time in the secondary cooling zone to the billet mass, expressed in liters per kilogram (L / kg). **Function:** Controls the surface temperature distribution of the billet, influencing crack formation and segregation; adjustment is required based on steel characteristics. 4. **Initial Stirring** Definition: The first electromagnetic stirring applied during continuous casting, typically referring to electromagnetic stirring in the crystallizer (M-EMS). **Function:** Improves molten steel flow, reduces inclusions, and enhances the internal quality of the billet. 5. **Second Cooling Electromagnetic Stirring** Definition: Electromagnetic stirring applied in the secondary cooling zone, such as electromagnetic stirring in the secondary cooling section (S-EMS). **Function:** Optimizes solidification structure, expands the equiaxed grain region, and eliminates intermediate crack defects. 6. **Final Stirring** Definition: Electromagnetic stirring applied at the end of continuous casting, such as electromagnetic stirring at the solidification end (F-EMS). **Function:** Improves center segregation, shrinkage cavities, and crack defects in high-carbon steel and alloy steel billets.

[0023] The specific implementation effect of the process method of the present invention is verified as follows: 1. The sawing surface condition of the cast billet during the preparation of materials after the forging process was recorded. In the example, the quality of 52 sawing surfaces was recorded. The maximum size of shrinkage cavity was 10mm, and the maximum size of crack was 15mm. Compared with the sawing surface quality under the original continuous casting process, the maximum size of shrinkage cavity was 30mm, and the maximum size of crack was 80mm. 2. The overall forging flaw detection was statistically analyzed. In the example, a total of 490 pieces were flaw-detected, consuming a batch of 1166.111t. Among them, 297.541t of forging bars were produced, with a pass rate of 98.11%, and 868.57t of special-shaped parts were produced, with a pass rate of 88.46%. The overall flaw detection pass rate was 90.925%. Compared with the overall flaw detection pass rate of 82% under the original continuous casting process, the overall quality of product processing was effectively improved.

[0024] The present invention has been described above with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A process for improving the quality of high-aluminum alloy steel used in injection molding machines, characterized in that: S1. The high-alumina alloy steel continuous casting billet (1) passes through the first roller group (2). The two first pressure rollers (3) of the first roller group (2) are located at the upper and lower parts of the high-alumina alloy steel continuous casting billet (1). The surface temperature of the first pressure roller (3) of the first roller group (2) is ≥850℃. The upper first pressure roller (3) applies pressure to the high-alumina alloy steel continuous casting billet (1). The pressure is controlled at 7Mpa-10Mpa. The pressure causes the residual unsolidified molten steel in the core of the high-alumina alloy steel continuous casting billet (1) to be discharged, the center of the billet is deformed, and the central shrinkage cavity and compression porosity are reduced. S2. The high-alumina alloy steel continuous casting billet (1) passes through the second roller group (4). The two second pressure rollers (5) of the second roller group (4) are located at the upper and lower parts of the high-alumina alloy steel continuous casting billet (1). The surface temperature of the second pressure rollers (5) of the second roller group (4) is ≥830℃. The upper second pressure roller (5) applies pressure to the high-alumina alloy steel continuous casting billet (1). The pressure is controlled at 7Mpa-10Mpa. The pressure consolidates the deformation of the high-alumina alloy steel continuous casting billet (1) and prevents springback. S3. The high-alumina alloy steel continuous casting billet that has passed through the second roll group (4) is slowly cooled for ≥60 hours, with a temperature ≥600℃ before slow cooling and a temperature ≤150℃ after slow cooling.

2. The process for improving the quality of high-aluminum alloy steel for injection molding machines according to claim 1, characterized in that: The end shaft of the first pressure roller (3) at the lower part of the first roller group (2) is installed on the first frame (6) near the lower part. A motor is installed on the first frame (6) and the motor drives the first pressure roller (3). The end shaft of the first pressure roller (3) at the upper part of the first roller group (2) is connected to the first lifting cylinder (7). The first lifting cylinder (7) is connected to the first frame (6) near the upper part.

3. The process for improving the quality of high-aluminum alloy steel for injection molding machines according to claim 1 or 2, characterized in that: The end shaft of the second pressure roller (5) at the lower part of the second roller group (4) is installed on the second frame (8) near the lower part. A motor is installed on the second frame (8) and the motor drives the second pressure roller (5). The end shaft of the second pressure roller (5) at the upper part of the second roller group (4) is connected to the second lifting cylinder (9). The second lifting cylinder (9) is connected to the second frame (8) near the upper part.

4. The process for improving the quality of high-aluminum alloy steel for injection molding machines according to claim 1 or 2, characterized in that: The production process for improving the quality of high-aluminum alloy steel used in injection molding machines includes the following steps in sequence: converter process → LF refining process → RH vacuum degassing process → continuous casting process → roller pressing process → slow cooling process → forging process.

5. The process for improving the quality of high-aluminum alloy steel for injection molding machines according to claim 4, characterized in that: In the converter process, no silicon-containing raw materials are used. High manganese, high carbon ferrochrome, and ferromolybdenum are added to the ladle when tapping the steel. The tapping end temperature is 1500℃-1525℃. The steel composition requirements are: C≥0.08% and P≤0.012%.

6. The process for improving the quality of high-aluminum alloy steel for injection molding machines according to claim 4, characterized in that: In the LF refining process, the refining time is >50 min, the white slag retention time is >20 min, and the use of silicon-containing auxiliary materials is strictly prohibited; the soft blowing time is ≥30 min, and the [H] at the station is ≤2 ppm, and [O] is <15 ppm.

7. The process for improving the quality of high-aluminum alloy steel for injection molding machines according to claim 4, characterized in that: In the continuous casting process of the continuous casting machine, the superheat is controlled at 30-40℃ and the casting speed is 0.2m / min-0.3m / min.

8. The process for improving the quality of high-aluminum alloy steel for injection molding machines according to claim 8, characterized in that: In the continuous casting process of the continuous casting machine, the water flow rate in the crystallizer is controlled at 3600L / min, the water flow rate in the secondary cooling system is controlled at 0.12L / Kg, the initial stirring is controlled at 150A / 2HZ, the secondary cooling electric stirring is controlled at 350A / 3HZ, and the final stirring is controlled at 1100A / 4HZ.

9. The process for improving the quality of high-aluminum alloy steel for injection molding machines according to claim 4, characterized in that: In the forging process, if defects are found in the core of the continuously cast billet after sawing, they need to be repaired by welding.

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