A high-strength planet carrier cast steel material and a preparation method of a high-strength planet carrier

Abstract

The application discloses a high-strength planet carrier cast steel material which is composed of the following elements in mass fraction: C 0.28-0.35%, Si 0.20-0.50%, Mn 0.80-1.20%, Cr 0.70-1.00%, Ni 0.80-1.20%, Mo 0.25-0.50%, Al 0.02-0.05%, S≤0.010%, P≤0.015%, and the balance of Fe, and further provides a preparation method of the high-strength planet carrier, wherein low-carbon steel and alloy materials are smelted and cast after being matched to obtain the high-strength planet carrier. The application controls the content of each element in the high-strength planet carrier cast steel material, improves the strength, hardness and wear resistance of the material, improves the hardenability of the material, refines the grain of the material, reduces the impurity content and reduces the cost.

Description

Technical Field

[0001] This invention belongs to the technical field of high-strength planetary carrier cast steel materials and preparation process, specifically relating to a high-strength planetary carrier cast steel material and a method for preparing a high-strength planetary carrier. Background Technology

[0002] The planetary carrier is a critical component of a coal mining machine, and its lifespan directly determines the machine's performance and reliability. Currently, planetary carriers are manufactured using either forging-welding or integral forging methods.

[0003] Forged and welded structures have high requirements for welding level and quality. The processing technology of the window part of the integral forged planetary carrier is complicated, with large processing allowance, low efficiency and long cycle. In addition, the blank weight of the planetary carrier forgings of these two types of structures is particularly large, resulting in high raw material procurement costs and high processing costs.

[0004] Furthermore, during actual casting, the planetary carrier's support section is a completely unmachined part with high dimensional accuracy requirements, which presents significant challenges to casting production. These challenges include: 1. During assembly, due to the small space and narrow assembly gaps in the support section, interference or inability to properly install the planetary gears frequently occurs, resulting in dimensional deviations in the casting; 2. During pouring and cooling, the support section is a sand core, leading to a narrow feeding path for the molten steel. The inability to add risers within the support section further exacerbates this, resulting in severe insufficient feeding. Shrinkage cavities and porosity frequently occur at the column position of the support section, and cracks appear at the connection between the column and the casting. Consequently, the quality of the casting fails to meet design requirements and usage requirements.

[0005] To improve the machinability of planetary carriers for high-end coal mining machines and enhance their inherent quality and stability, there is an urgent need for a new type of cast steel material for planetary carriers and planetary carriers made from this material. This material can meet the requirements of high strength and high reliability, while also reducing machining difficulty, improving machining efficiency, and solving production bottlenecks. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a high-strength planetary carrier cast steel material, addressing the shortcomings of the prior art. This high-strength planetary carrier cast steel material improves the material's strength, hardness, and wear resistance, enhances hardenability, refines grain size, reduces impurity content, and lowers costs by controlling the content of each element.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a high-strength planetary carrier cast steel material, characterized in that the cast steel material is composed of the following elements by mass fraction: C 0.28%~0.35%, Si 0.20%~0.50%, Mn 0.80%~1.20%, Cr 0.70%~1.00%, Ni 0.80%~1.20%, Mo 0.25%~0.50%, Al 0.02%~0.05%, S≤0.010%, P≤0.015%, with the balance being Fe.

[0008] This invention controls the content of various elements, where Cr has a significant strengthening effect, improving strength, hardness, and wear resistance, and enhancing the hardenability of steel; Ni improves the strength of steel without reducing its plasticity, and also enhances its hardenability; Mo strengthens ferrite in steel, improving its strength, hardness, and hardenability; Al plays a good deoxidizing role in steel, refining the steel grains, increasing strength, and reducing the content of S and P. This is because when the P content in steel is greater than 0.1%, iron phosphide precipitates around the grains, reducing the plasticity and toughness of the steel; and S exists in molten steel as FeS or FeS-Fe eutectic around the grains, reducing the mechanical properties of the steel. This results in a high-strength planetary carrier cast steel material, solving the shortcomings of traditional materials where the Cr and Ni content is too high, leading to excessively high costs.

[0009] The aforementioned high-strength planetary carrier cast steel material is characterized in that the cast steel material is composed of the following elements by mass fraction: C 0.30%–0.33%, Si 0.39%–0.48%, Mn 1.05%–1.12%, Cr 0.75%–0.83%, Ni 0.83%–0.85%, Mo 0.31%–0.33%, Al 0.02%–0.04%, S≤0.004%, P≤0.012%, with the balance being Fe.

[0010] The aforementioned high-strength planetary carrier cast steel material is characterized in that the cast steel material is composed of the following elements: C 0.30%, Si 0.39%, Mn 1.05%, Cr 0.82%, Ni 0.85%, Mo 0.33%, Al 0.02%, S≤0.004%, P≤0.012%, with the balance being Fe.

[0011] In addition, the present invention provides a process for preparing a high-strength planetary carrier using cast steel material, characterized in that the method includes the following steps:

[0012] Step 1: Prepare the casting mold for the planetary carrier;

[0013] Step 2: Low-carbon steel and alloy materials are batched according to high-strength planetary carrier cast steel materials, then smelted in an electric arc furnace, and then placed in a ladle for ladle refining to obtain molten steel;

[0014] Step 3: Pour the molten steel obtained in Step 2 into the casting mold prepared in Step 1;

[0015] Step 4: After the molten steel cast in Step 3 has cooled, demold it and then perform heat treatment to obtain a high-strength planetary carrier.

[0016] The casting mold for preparing planetary carriers of the present invention includes the processes of molding, preparing sand cores, placing chills, filling sand, and sealing the mold, which ensures the integrity of the casting mold structure of the planetary carrier and enables the preparation of high-strength planetary carriers.

[0017] The above method is characterized in that the amount of raw sand used in the casting mold in step one is higher than 98%. This invention ensures the casting effect by controlling the amount of raw sand used, and uses raw sand with higher refractory properties in the thicker parts of the casting in the casting mold to prevent the raw sand from sintering and forming steel-clad sand or adhering sand.

[0018] The above method is characterized in that the process compensation amount of the opening part in the casting mold in step one meets the following requirements: 1.5mm in the middle and gradually decreasing to 0.5mm on both sides; all rounded corners are made by the model; and a lining is added to the outside of the column. In this invention, the steel melt channel in this part is increased by designing the process compensation amount and adding the lining during casting, thereby ensuring the column structure is dense. After the casting is heat-treated, it is cut off and polished to meet the casting size requirements.

[0019] The method described above is characterized in that the low-carbon steel and alloy materials described in step two are baked to remove moisture before use. This invention removes moisture from the low-carbon steel and alloy materials through baking, thus ensuring the quality of the high-strength planetary carrier.

[0020] The above method is characterized in that, in step two, the temperature of the electric arc furnace smelting is 1550℃~1650℃, and the ladle refining is performed by argon blowing upon exiting the furnace. The argon blowing pressure is 0.1MPa~0.3MPa, the time is more than 5 minutes, and the mixture is left to stand for more than 5 minutes after the argon blowing is completed. This invention ensures that low-carbon steel and alloy materials are fully melted into molten steel by controlling the temperature of the electric arc furnace smelting. Argon blowing removes impurities and harmful gases, achieving the purpose of purifying the molten steel. The standing process allows sufficient time for internal gases and inclusions to float to the surface, improving the purification effect.

[0021] The above method is characterized in that the casting temperature in step three is 1550℃~1600℃; when the molten steel rises to 2 / 3 of the riser height, a heat-insulating agent, which is wood ash, is promptly applied to cover the riser with a thickness of at least 20mm; and heat preservation is performed after casting. This invention ensures the casting effect by controlling the casting temperature, and by promptly applying the heat-insulating agent when the molten steel rises to 2 / 3 of the riser height, it ensures that the molten steel at the riser can effectively compensate for the shrinkage of the casting. Furthermore, heat preservation is performed after casting to prevent cracking.

[0022] The above method is characterized in that the heat treatment process in step four is as follows: heating to 920℃ and normalizing for 3 hours, followed by air cooling, then heating to 620℃ for tempering for 3 hours, followed by air cooling, then heating to 880℃ and holding for 3 hours, followed by oil quenching, and finally heating to 570℃ for a second tempering for 3.5 hours, followed by oil cooling. This invention improves the performance of the high-strength planetary carrier by performing heat treatment in steps, ensuring that the various performance indicators of the high-strength planetary carrier meet or exceed the requirements for use.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. This invention improves the strength, hardness, and wear resistance of high-strength planetary carrier cast steel by controlling the content of each element, thereby improving the hardenability, refining the grain size, and controlling the impurity content. This solves the problem of excessively high Cr and Ni content and high cost in traditional materials.

[0025] 2. This invention uses low-carbon steel and alloy materials as raw materials to prepare high-strength planetary carriers by casting, and improves their internal properties through heat treatment, thereby reducing the manufacturing cost of raw materials, simplifying the processing procedures, shortening the processing cycle, and further improving their overall stability, ensuring the quality and service life of the high-strength planetary carriers, and meeting the requirements of coal mining machines for high-strength planetary carriers.

[0026] 3. In this invention, during casting, the process is adjusted by designing the process correction and adding lining to enlarge the molten steel channel in that area, thereby ensuring the column's structure is dense. After the casting is heat-treated, it is cut off and ground to meet the casting dimensional requirements. This improves the quality of the high-strength planetary carrier.

[0027] 4. The high-strength planetary carrier cast steel material of the present invention has a yield strength greater than 900MPa, a tensile strength greater than 1008MPa, and a hardness greater than 293HB. The high-strength planetary carrier prepared therefrom has a yield strength greater than 945MPa, a tensile strength greater than 1045MPa, and a hardness greater than 296HB.

[0028] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the process correction amount for the opening part in this invention.

[0030] Figure 2 This is a physical image of the high-strength planetary carrier prepared in Embodiment 1 of the present invention.

[0031] Figure 3 This is a SEM image of the high-strength planetary carrier prepared in Example 2 of the present invention.

[0032] Figure 4 This is a SEM image of the high-strength planetary carrier prepared in Example 3 of the present invention. Detailed Implementation

[0033] Figure 1 This is a schematic diagram of the process correction amount for the opening portion in this invention. Figure 1 The planetary carrier in the middle is the cast planetary carrier, from Figure 1 As can be seen, the opening part of the planetary carrier is window-shaped, with a correction amount of 1.5mm in the middle of the opening part, which gradually decreases to 0.5mm on both sides of the opening part, and additional lining is added to the outside of the column.

[0034] Example 1

[0035] The cast steel material in this embodiment is composed of the following elements: C 0.33%, Si 0.48%, Mn 1.05%, Cr 0.83%, Ni 0.83%, Mo 0.32%, Al 0.03%, S 0.005%, P 0.011%, with the balance being Fe.

[0036] This embodiment includes the following steps:

[0037] Step 1: Prepare the casting mold for the planetary carrier; the amount of raw sand in the casting mold is higher than 98%; the process compensation amount of the opening part in the casting mold meets the following requirements: 1.5mm in the middle and gradually decreases to 0.5mm on both sides, all rounded corners are made by the model, and additional lining is added to the outside of the column;

[0038] Step 2: After baking and dehydrating the low-carbon steel and alloy materials according to the high-strength planetary carrier cast steel material, the materials are batched and then smelted in an electric arc furnace at a temperature of 1550℃~1650℃. After that, the materials are placed in a ladle for ladle refining. Argon gas is blown into the ladle at a pressure of 0.1MPa~0.3MPa for more than 5 minutes. After the argon blowing is completed, the materials are allowed to stand for more than 5 minutes to obtain molten steel.

[0039] Step 3: Pour the molten steel obtained in Step 2 into the casting mold prepared in Step 1 at a temperature of 1550℃~1600℃. When the molten steel rises to 2 / 3 of the riser, promptly sprinkle wood ash insulation agent, with an amount sufficient to cover the riser with a thickness of more than 20mm. After pouring, keep it warm.

[0040] Step 4: After the molten steel cast in Step 3 has cooled, demold it, heat it to 920℃ and normalize it for 3 hours, then air cool it, then heat it to 620℃ and temper it for 3 hours, then air cool it, then heat it to 880℃ and hold it for 3 hours, then oil quench it, and finally heat it to 570℃ and temper it for 3.5 hours, and then oil cool it to obtain a high-strength planetary carrier.

[0041] Figure 2 This is a physical image of the high-strength planetary carrier prepared in this embodiment. Figure 1 As can be seen from the image, the high-strength planetary carrier prepared in this embodiment has a smooth surface.

[0042] Example 2

[0043] The cast steel material in this embodiment is composed of the following elements: C 0.30%, Si 0.39%, Mn 1.05%, Cr 0.82%, Ni 0.85%, Mo 0.33%, Al 0.02%, S 0.004%, P 0.012%, with the balance being Fe.

[0044] This embodiment includes the following steps:

[0045] Step 1: Prepare the casting mold for the planetary carrier; the amount of raw sand in the casting mold is higher than 98%; the process compensation amount of the opening part in the casting mold meets the following requirements: 1.5mm in the middle and gradually decreases to 0.5mm on both sides, all rounded corners are made by the model, and additional lining is added to the outside of the column;

[0046] Step 2: After baking and dehydrating the low-carbon steel and alloy materials according to the high-strength planetary carrier cast steel material, the materials are batched and then smelted in an electric arc furnace at a temperature of 1550℃~1650℃. After that, the materials are placed in a ladle for ladle refining. Argon gas is blown into the ladle at a pressure of 0.1MPa~0.3MPa for more than 5 minutes. After the argon blowing is completed, the materials are allowed to stand for more than 5 minutes to obtain molten steel.

[0047] Step 3: Pour the molten steel obtained in Step 2 into the casting mold prepared in Step 1 at a temperature of 1550℃~1600℃. When the molten steel rises to 2 / 3 of the riser, promptly sprinkle wood ash insulation agent, with an amount sufficient to cover the riser with a thickness of more than 20mm. After pouring, keep it warm.

[0048] Step 4: After the molten steel cast in Step 3 has cooled, demold it, heat it to 920℃ and normalize it for 3 hours, then air cool it, then heat it to 620℃ and temper it for 3 hours, then air cool it, then heat it to 880℃ and hold it for 3 hours, then oil quench it, and finally heat it to 570℃ and temper it for 3.5 hours, and then oil cool it to obtain a high-strength planetary carrier.

[0049] Figure 3 This is a SEM image of the high-strength planetary carrier prepared in this embodiment. Figure 3 As can be seen, the microstructure consists of fine tempered troostite.

[0050] Example 3

[0051] The cast steel material in this embodiment is composed of the following elements: C 0.30%, Si 0.43%, Mn 1.12%, Cr 0.75%, Ni 0.83%, Mo 0.31%, Al 0.04%, S 0.006%, P 0.007%, with the balance being Fe.

[0052] This embodiment includes the following steps:

[0053] Step 1: Prepare the casting mold for the planetary carrier; the amount of raw sand in the casting mold is higher than 98%; the process compensation amount of the opening part in the casting mold meets the following requirements: 1.5mm in the middle and gradually decreases to 0.5mm on both sides, all rounded corners are made by the model, and additional lining is added to the outside of the column;

[0054] Step 2: After baking and dehydrating the low-carbon steel and alloy materials according to the high-strength planetary carrier cast steel material, the materials are batched and then smelted in an electric arc furnace at a temperature of 1550℃~1650℃. After that, the materials are placed in a ladle for ladle refining. Argon gas is blown into the ladle at a pressure of 0.1MPa~0.3MPa for more than 5 minutes. After the argon blowing is completed, the materials are allowed to stand for more than 5 minutes to obtain molten steel.

[0055] Step 3: Pour the molten steel obtained in Step 2 into the casting mold prepared in Step 1 at a temperature of 1550℃~1600℃. When the molten steel rises to 2 / 3 of the riser, promptly sprinkle wood ash insulation agent, with an amount sufficient to cover the riser with a thickness of more than 20mm. After pouring, keep it warm.

[0056] Step 4: After the molten steel cast in Step 3 has cooled, demold it, heat it to 920℃ and normalize it for 3 hours, then air cool it, then heat it to 620℃ and temper it for 3 hours, then air cool it, then heat it to 880℃ and hold it for 3 hours, then oil quench it, and finally heat it to 570℃ and temper it for 3.5 hours, and then oil cool it to obtain a high-strength planetary carrier.

[0057] Figure 4This is a SEM image of the high-strength planetary carrier prepared in this embodiment. Figure 4 As can be seen, the microstructure consists of fine tempered troostite.

[0058] The cast steel materials from Examples 1 to 3 were subjected to performance tests compared with 42CrMo steel and ZG34CrNiMo steel. The results are shown in Table 1, and the mass fractions of each element in 42CrMo steel and ZG34CrNiMo steel are shown in Table 2.

[0059] Table 1

[0060]

[0061]

[0062] Table 2

[0063]

[0064] As can be seen from Table 1, the cast steel materials of Examples 1 to 3 have excellent mechanical properties and fully meet the application requirements. Combining Table 1 and Table 2, it can be seen that the cast steel materials of Examples 1 to 3 have reduced Cr and Ni content, while having excellent mechanical properties and reducing the preparation cost.

[0065] The mass fractions of each element in the high-strength planetary frames prepared in Examples 2 and 3 are shown in Table 3, and the mechanical property test results are shown in Table 4.

[0066] Table 3

[0067]

[0068]

[0069] Table 4

[0070]

[0071] As can be seen from Tables 3 and 4, the high-strength planetary carriers prepared in Examples 2 and 3 have excellent mechanical properties.

[0072] Example 4

[0073] The cast steel material in this embodiment is composed of the following elements: C 0.28%, Si 0.50%, Mn 0.80%, Cr 1.00%, Ni 0.80%, Mo 0.50%, Al 0.02%, S≤0.010%, P≤0.015%, with the balance being Fe.

[0074] This embodiment includes the following steps:

[0075] Step 1: Prepare the casting mold for the planetary carrier; the amount of raw sand in the casting mold is higher than 98%; the process compensation amount of the opening part in the casting mold meets the following requirements: 1.5mm in the middle and gradually decreases to 0.5mm on both sides, all rounded corners are made by the model, and additional lining is added to the outside of the column;

[0076] Step 2: After baking and dehydrating the low-carbon steel and alloy materials according to the high-strength planetary carrier cast steel material, the materials are batched and then smelted in an electric arc furnace at a temperature of 1550℃~1650℃. After that, the materials are placed in a ladle for ladle refining. Argon gas is blown into the ladle at a pressure of 0.1MPa~0.3MPa for more than 5 minutes. After the argon blowing is completed, the materials are allowed to stand for more than 5 minutes to obtain molten steel.

[0077] Step 3: Pour the molten steel obtained in Step 2 into the casting mold prepared in Step 1 at a temperature of 1550℃~1600℃. When the molten steel rises to 2 / 3 of the riser, promptly sprinkle wood ash insulation agent, with an amount sufficient to cover the riser with a thickness of more than 20mm. After pouring, keep it warm.

[0078] Step 4: After the molten steel cast in Step 3 has cooled, demold it, heat it to 920℃ and normalize it for 3 hours, then air cool it, then heat it to 620℃ and temper it for 3 hours, then air cool it, then heat it to 880℃ and hold it for 3 hours, then oil quench it, and finally heat it to 570℃ and temper it for 3.5 hours, and then oil cool it to obtain a high-strength planetary carrier.

[0079] Example 5

[0080] The cast steel material in this embodiment is composed of the following elements: C 0.35%, Si 0.20%, Mn 1.20%, Cr 0.70%, Ni 1.20%, Mo 0.25%, Al 0.05%, S≤0.010%, P≤0.015%, with the balance being Fe.

[0081] This embodiment includes the following steps:

[0082] Step 1: Prepare the casting mold for the planetary carrier; the amount of raw sand in the casting mold is higher than 98%; the process compensation amount of the opening part in the casting mold meets the following requirements: 1.5mm in the middle and gradually decreases to 0.5mm on both sides, all rounded corners are made by the model, and additional lining is added to the outside of the column;

[0083] Step 2: After baking and dehydrating the low-carbon steel and alloy materials according to the high-strength planetary carrier cast steel material, the materials are batched and then smelted in an electric arc furnace at a temperature of 1550℃~1650℃. After that, the materials are placed in a ladle for ladle refining. Argon gas is blown into the ladle at a pressure of 0.1MPa~0.3MPa for more than 5 minutes. After the argon blowing is completed, the materials are allowed to stand for more than 5 minutes to obtain molten steel.

[0084] Step 3: Pour the molten steel obtained in Step 2 into the casting mold prepared in Step 1 at a temperature of 1550℃~1600℃. When the molten steel rises to 2 / 3 of the riser, promptly sprinkle wood ash insulation agent, with an amount sufficient to cover the riser with a thickness of more than 20mm. After pouring, keep it warm.

[0085] Step 4: After the molten steel cast in Step 3 has cooled, demold it, heat it to 920℃ and normalize it for 3 hours, then air cool it, then heat it to 620℃ and temper it for 3 hours, then air cool it, then heat it to 880℃ and hold it for 3 hours, then oil quench it, and finally heat it to 570℃ and temper it for 3.5 hours, and then oil cool it to obtain a high-strength planetary carrier.

[0086] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A high-strength planetary carrier, characterized in that, It is composed of the following elements by mass fraction: C 0.30%~0.33%, Si 0.39%~0.48%, Mn 1.05%~1.12%, Cr 0.75%~0.83%, Ni 0.83%~0.85%, Mo 0.31%~0.33%, Al 0.02%~0.04%, S≤0.004%, P≤0.012%, with the balance being Fe; the high-strength planetary carrier has a yield strength greater than 945MPa, a tensile strength greater than 1045MPa, a hardness greater than 296HB, and its microstructure is fine tempered troostite.

2. The high-strength planetary carrier according to claim 1, characterized in that, It is composed of the following elements in the following mass fractions: C 0.30%, Si 0.39%, Mn 1.05%, Cr 0.82%, Ni 0.85%, Mo 0.33%, Al 0.02%, S≤0.004%, P≤0.012%, with the balance being Fe.

3. A method for preparing a high-strength planetary carrier as described in any one of claims 1 or 2, characterized in that, The method includes the following steps: Step 1: Prepare the casting mold for the planetary carrier; Step 2: Low-carbon steel and alloy materials are batched according to high-strength planetary carrier cast steel materials, then smelted in an electric arc furnace, and then placed in a ladle for ladle refining to obtain molten steel; Step 3: Pour the molten steel obtained in Step 2 into the casting mold prepared in Step 1; Step 4: After the molten steel cast in Step 3 has cooled, demold it and then perform heat treatment to obtain a high-strength planetary carrier. The heat treatment process is as follows: heat to 920℃ and normalize for 3 hours, then air cool, then heat to 620℃ and temper for 3 hours, then air cool, then heat to 880℃ and hold for 3 hours, followed by oil quenching, and finally heat to 570℃ and temper for 3.5 hours, followed by oil cooling.

4. The method according to claim 3, characterized in that, The amount of raw sand used in the casting mold described in step one is higher than 98%.

5. The method according to claim 3, characterized in that, The process compensation amount for the opening part in the casting mold described in step one is as follows: 1.5mm in the middle and gradually reduced to 0.5mm on both sides. All rounded corners are made by modeling, and additional lining is added to the outside of the column.

6. The method according to claim 3, characterized in that, The low-carbon steel and alloy materials mentioned in step two are baked to remove moisture before use.

7. The method according to claim 3, characterized in that, In step two, the temperature of the electric arc furnace smelting is 1550℃~1650℃. The furnace refining process involves argon blowing when the furnace is exited. The argon blowing pressure is 0.1MPa~0.3MPa, the time is more than 5 minutes, and the furnace is left to stand for more than 5 minutes after the argon blowing is completed.

8. The method according to claim 3, characterized in that, The casting temperature in step three is 1550℃~1600℃. When the molten steel rises to 2 / 3 of the riser, a heat-insulating agent is promptly applied. The heat-insulating agent is wood ash, and the amount used is to cover the riser with a thickness of more than 20mm. Heat preservation is carried out after casting.

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