High-strength pipe pile steel die and machining and forming process thereof

Abstract

The invention discloses a high-strength wear-resistant pipe pile steel die and a processing and forming process thereof. The high-strength wear-resistant pipe pile steel die is prepared from the following components in percentage by weight: 0.28 to 0.38 percent of C, 0.30 to 0.60 percent of Si, 1.20 to 1.80 percent of Mn, 0.80 to 1.50 percent of Cr, 0.20 to 0.40 percent of Mo, 0.30 to 0.80 percent of Ni, 0.05 to 0.15 percent of V, 0.02 to 0.06 percent of Nb, less than or equal to 0.015 percent of P, less than or equal to 0.010 percent of S and the balance of Fe and inevitable impurities. The prepared steel die has excellent strength, toughness, wear resistance and thermal fatigue resistance, the service life is remarkably prolonged, and the steel die is suitable for harsh pipe pile production working conditions.

Description

Technical Field

[0001] This invention belongs to the field of steel molds for pipe piles, and more specifically, it relates to a high-strength steel mold for pipe piles and its processing and forming technology. Background Technology

[0002] As a crucial foundation building material, pipe piles face extremely harsh working conditions during their production. The steel molds must withstand the intense erosion of concrete slurry, alternating temperature stress, and mechanical wear during demolding. Traditional pipe pile steel molds are mostly made of medium carbon steel or ordinary alloy steel, which often struggle to achieve a balance between wear resistance, toughness, and thermal fatigue resistance. Conventional heat treatment processes can easily lead to uneven properties between the mold core and surface, or generate significant structural stress, resulting in premature wear, surface cracking, and even brittle fracture during use, severely impacting production efficiency and mold life. Therefore, developing a new type of pipe pile steel mold and its processing technology—characterized by a scientifically designed composition and optimized heat treatment process—that can achieve high and uniform comprehensive mechanical properties, particularly combining high surface wear resistance with good core toughness, thereby significantly extending its service life, is of significant practical importance. Summary of the Invention

[0003] In view of this, the technical problem to be solved by the present invention is to provide a high-strength steel mold for pipe piles and its processing technology. This solves the problems of early wear, cracking, and short lifespan caused by insufficient wear resistance, toughness, and thermal fatigue resistance of traditional steel molds for pipe piles, by optimizing alloy composition and gradient temperature controlled quenching processes to improve overall performance.

[0004] To address the aforementioned technical problems, this invention discloses a novel steel mold for pipe piles and its processing and forming process, comprising: a composition in the following weight percentages: C: 0.28~0.38%, Si: 0.30~0.60%, Mn: 1.20~1.80%, Cr: 0.80~1.50%, Mo: 0.20~0.40%, Ni: 0.30~0.80%, V: 0.05~0.15%, Nb: 0.02~0.06%, P≤0.015%, S≤0.010%, with the balance being Fe and unavoidable impurities.

[0005] According to one embodiment of the present invention, the above-mentioned components are composed of the following weight percentages: C: 0.28%, Si: 0.30%, Mn: 1.20%, Cr: 0.80%, Mo: 0.20%, Ni: 0.30%, V: 0.05%, Nb: 0.02%, P: 0.005%, S: 0.003%, with the balance being Fe and unavoidable impurities.

[0006] According to one embodiment of the present invention, the above-mentioned components are composed of the following weight percentages: C: 0.33%, Si: 0.45%, Mn: 1.50%, Cr: 1.20%, Mo: 0.30%, Ni: 0.55%, V: 0.10%, Nb: 0.04%, P: 0.010%, S: 0.016%, with the balance being Fe and unavoidable impurities.

[0007] According to one embodiment of the present invention, the above-mentioned components are composed of the following weight percentages: C: 0.38%, Si: 0.60%, Mn: 1.80%, Cr: 1.50%, Mo: 0.40%, Ni: 0.80%, V: 0.15%, Nb: 0.06%, P: 0.015%, S: 0.010%, with the balance being Fe and unavoidable impurities.

[0008] According to an embodiment of the present invention, the processing and forming process of the above-mentioned high-strength wear-resistant pipe pile steel mold alloy includes the following steps: S1: Smelting and casting: Smelting in an electric furnace or converter according to the proportion, and after ladle refining and vacuum degassing, casting into steel ingots or continuous casting into billets; S2: Forging and rolling: Heat steel ingots or continuous casting billets to 1180~1250℃, hold them at that temperature, and then perform multi-directional forging or rolling to produce steel plates or modules. The final forging and final rolling temperatures shall not be lower than 900℃. S3: Preliminary heat treatment: The formed workpiece is normalized at a temperature of 900~940℃, and then air-cooled. S4: Final heat treatment: includes the following sub-steps: S41: Quenching: Heat the workpiece to 880~910℃ for austenitization, hold it at that temperature, and then use "gradient temperature control quenching". First, it is rapidly cooled in a nitrate salt bath at 260~320℃ and held for 3-8 minutes. Then, it is transferred to a low-temperature salt bath at 140~180℃ to continue cooling to room temperature. S42: Tempering: Heat the quenched workpiece to 560~620℃, hold it at that temperature for a sufficient time, and then air cool it after removing it from the furnace.

[0009] According to one embodiment of the present invention, after the tempering in step S42, a stress-relief tempering step is further included, with a heating temperature of 480~520°C and a holding time of 1 / 3~1 / 2 of the final tempering holding time.

[0010] According to one embodiment of the present invention, after the final heat treatment is completed, the inner working surface of the steel mold is subjected to surface strengthening treatment, which is laser cladding or plasma spraying, and the cladding or spraying material is a cobalt-based or nickel-based tungsten carbide metal ceramic layer.

[0011] According to one embodiment of the present invention, the mold segments of the split steel mold described above need to be integrally forged in step S2, and after being processed in steps S3 and S4, they are then divided along the preset mold parting surface using wire cutting or water jet cutting processes; after division, the mold parting surface is finely ground, and local surfacing is performed using low-hydrogen welding rods to correct the dimensions; after surfacing, stress-relieving tempering is required.

[0012] Compared with the prior art, the present invention can achieve the following technical effects: 1) The prepared steel mold has excellent strength, toughness, wear resistance and thermal fatigue resistance, which significantly improves its service life and is suitable for harsh pipe pile production conditions.

[0013] Of course, any product implementing this invention does not necessarily need to achieve all of the above technical effects at the same time. Attached Figure Description

[0014] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a flowchart illustrating an embodiment of the present invention. Detailed Implementation

[0015] The following will describe in detail the implementation of the present invention with reference to the accompanying drawings and embodiments, so that the process of how the present invention uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. Example 1:

[0016] The weight percentages of Example 1 are as follows: C: 0.28%, Si: 0.30%, Mn: 1.20%, Cr: 0.80%, Mo: 0.20%, Ni: 0.30%, V: 0.05%, Nb: 0.02%, P: 0.005%, S: 0.003%, with the balance being Fe and unavoidable impurities.

[0017] Preparation method of Example 1: S1: Smelting and casting: Smelting is carried out in an electric arc furnace, and after refining in an LF furnace and vacuum degassing in a VD furnace, it is cast into steel ingots.

[0018] S2: Forging: The steel ingot is heated to 1190°C, held at that temperature, and then forged into a block through multi-directional free forging. The final forging temperature is controlled above 920°C.

[0019] S3: Preliminary heat treatment: Perform normalizing treatment, heat to 910°C, hold at that temperature and then air cool to refine the grains.

[0020] S4: Final heat treatment: S41: Quenching: Heating to 880°C for austenitization, holding at that temperature, and then quenching with gradient temperature control: First, quench in a 280°C nitrate bath for rapid cooling and hold for 5 minutes, then quickly transfer to a 160°C low-temperature salt bath to cool to room temperature.

[0021] S42: Tempering: Temper at 600°C for a sufficient time, then remove from the furnace and air cool.

[0022] S5: Post-treatment: To stabilize dimensions, perform a stress-relieving tempering process at 500°C.

[0023] Example 1 achieves excellent overall toughness and impact fatigue resistance by adopting a heat treatment process that prioritizes the lower limit of the composition and focuses on toughness, while keeping costs under control. Example 2:

[0024] The weight percentages of Example 2 are as follows: C: 0.33%, Si: 0.45%, Mn: 1.50%, Cr: 1.15%, Mo: 0.30%, Ni: 0.55%, V: 0.10%, Nb: 0.04%, P: 0.010%, S: 0.008%, with the balance being Fe and unavoidable impurities.

[0025] Preparation method of Example 2: S1: Smelting and casting: Smelting is carried out in a converter, and after refining by LF+RH, it is continuously cast into slabs.

[0026] S2: Rolling: The slab is heated to 1220°C and hot rolled in multiple passes to produce a steel plate of the required thickness. The final rolling temperature is not lower than 910°C.

[0027] S3: Preparatory heat treatment: The cut steel plate is normalized at 930°C and then air-cooled.

[0028] S4: Final heat treatment: S41: Quenching: Heating to 900°C for austenitization, holding at that temperature, and then performing gradient temperature-controlled quenching: first quenching in a 300°C nitrate bath for 4 minutes, and then transferring to a 150°C low-temperature salt bath for cooling.

[0029] S42: Tempering: Temper at 580°C, hold at that temperature, and then air cool.

[0030] S5: Surface strengthening: Plasma spraying is performed on the working surface of the inner wall of the steel mold after processing to prepare a nickel-based tungsten carbide metal ceramic coating.

[0031] Example 2 uses the median composition of the ingredients and combines it with standard heat treatment processes to achieve an optimal balance of strength, toughness, and wear resistance. The "gradient temperature controlled quenching" process is highly effective with this formula, effectively preventing cracking in complex molds. Example 3:

[0032] The weight percentages of Example 3 are as follows: C: 0.38%, Si: 0.60%, Mn: 1.80%, Cr: 1.50%, Mo: 0.40%, Ni: 0.80%, V: 0.15%, Nb: 0.06%, P: 0.012%, S: 0.005%, with the balance being Fe and unavoidable impurities.

[0033] Preparation method of Example 3: S1: Smelting and casting: Smelting is carried out in an ultra-high power electric furnace, followed by deep desulfurization and vacuum circulation degassing, and then casting into high-quality steel ingots.

[0034] S2: Forging: Heating to 1240°C, and then forging in multiple directions through upsetting and drawing to ensure a dense core structure. The final forging temperature is ≥930°C.

[0035] S3: Preparatory heat treatment: Normalize at 940°C and air cool.

[0036] S4: Final heat treatment: S41: Quenching: Heat to 910°C for full austenitization, and use toughening quenching: first quench in a 320°C nitrate salt bath for rapid cooling and hold for 6 minutes, then transfer to a 140°C salt bath for slow cooling.

[0037] S42: Tempering: Tempering at a relatively low temperature of 560°C is used to retain more high-hardness carbides, followed by air cooling after heat preservation.

[0038] S5: Special treatment for split mold halves: This mold is designed as two halves. The forging and heat treatment described above are all completed on the integral module. After the performance meets the standards, it is precisely divided along the preset parting surface using slow wire EDM. After division, the parting surface is finely ground, and local welding is performed using low-hydrogen welding rods for correction. Finally, it is stress-relieving tempered at 520°C.

[0039] Example 3: The high alloy content, combined with a relatively high quenching temperature and a relatively low tempering temperature, gives the material extremely high surface hardness and wear resistance. The "integral heat treatment followed by segmentation" process ensures the uniformity of performance and dimensional stability of each part of the split mold segment, eliminating mold closing gap problems caused by split heat treatment.

[0040] Comparison chart of strength, toughness, and wear resistance for Examples 1, 2, and 3:

[0041] These three embodiments demonstrate how to meet the performance requirements of different application scenarios by adjusting the composition and fine-tuning the process parameters, providing complete and hierarchical implementation support for the core patent claims.

[0042] In summary, the prepared steel mold possesses excellent strength, toughness, wear resistance, and thermal fatigue resistance, significantly improving its service life and making it suitable for harsh pipe pile production conditions.

[0043] The foregoing description illustrates and describes several preferred embodiments of the present invention. However, as previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept by means of the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A high strength abrasion resistant pipe pile steel form characterized by, Composed of the following ingredients by weight percentage Composition: C: 0.28~0.38%, Si: 0.30~0.60%, Mn: 1.20~1.80%, Cr: 0.80~1.50%, Mo: 0.20~0.40%, Ni: 0.30~0.80%, V: 0.05~0.15%, Nb: 0.02~0.06%, P≤0.015%, S≤0.010%, balance Fe and unavoidable impurities.

2. The high-strength wear-resistant pipe pile steel mold according to claim 1, characterized in that, Composed of the following ingredients by weight percentage Composition: C: 0.28%, Si: 0.30%, Mn: 1.20%, Cr: 0.80%, Mo: 0.20%, Ni: 0.30%, V: 0.05%, Nb: 0.02%, P: 0.005%, S: 0.003%, with the balance being Fe and unavoidable impurities.

3. The high-strength wear-resistant pipe pile steel mold according to claim 1, characterized in that, Composed of the following ingredients by weight percentage Composition: C: 0.33%, Si: 0.45%, Mn: 1.50%, Cr: 1.20%, Mo: 0.30%, Ni: 0.55%, V: 0.10%, Nb: 0.04%, P: 0.010%, S: 0.016%, with the balance being Fe and unavoidable impurities.

4. The high-strength wear-resistant pipe pile steel mold according to claim 1, characterized in that, Composed of the following ingredients by weight percentage Composition: C: 0.38%, Si: 0.60%, Mn: 1.80%, Cr: 1.50%, Mo: 0.40%, Ni: 0.80%, V: 0.15%, Nb: 0.06%, P: 0.015%, S: 0.010%, with the balance being Fe and unavoidable impurities.

5. A processing and forming process for a high-strength wear-resistant pipe pile steel mold, used to prepare the high-strength wear-resistant pipe pile steel mold as described in any one of claims 1-5, characterized in that, Includes the following steps: S1: Smelting and casting: Smelting in an electric furnace or converter according to the specified proportions, and after ladle refining and vacuum degassing, casting into steel ingots or continuous casting into billets; S2: Forging and rolling: Heat steel ingots or continuous casting billets to 1180~1250℃, hold them at that temperature, and then perform multi-directional forging or rolling to produce steel plates or modules. The final forging and final rolling temperatures shall not be lower than 900℃. S3: Preliminary heat treatment: The formed workpiece is normalized at a temperature of 900~940℃, and then air-cooled. S4: Final heat treatment: Includes the following sub-steps: S41: Quenching: Heat the workpiece to 880~910℃ for austenitization, hold it at that temperature, and then use gradient temperature control quenching. First, quench it in a nitrate bath at 260~320℃ for rapid cooling and hold it for 3-8 minutes. Then, transfer it to a low-temperature salt bath at 140~180℃ to continue cooling to room temperature. S42: Tempering: Heat the quenched workpiece to 560~620℃, hold it at that temperature for a sufficient time, and then air cool it after removing it from the furnace.

6. The processing and forming process of the high-strength wear-resistant pipe pile steel mold according to claim 5, characterized in that, After the tempering in step S42, a stress-relief tempering step is also included, with a heating temperature of 480~520℃ and a holding time of 1 / 3~1 / 2 of the final tempering holding time.

7. The processing and forming process of the high-strength wear-resistant pipe pile steel mold according to claim 5, characterized in that, After the final heat treatment is completed, the inner working surface of the steel mold is subjected to surface strengthening treatment, which is laser cladding or plasma spraying, and the cladding or spraying material is a cobalt-based or nickel-based tungsten carbide metal ceramic layer.

8. The processing and forming process of the high-strength wear-resistant pipe pile steel mold according to claim 5, characterized in that, For the mold segments of the split steel mold, they need to be forged as a whole in step S2, and after being processed in steps S3 and S4, they are then divided along the preset mold parting surface using wire cutting or water jet cutting processes. After segmentation, the mold surface is finely ground, and local welding is performed using low-hydrogen welding rods to correct the dimensions. After welding, stress-relieving tempering is required.

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