Laser processing life extension method for through-penetration mandrel plug based on composite metal layer

Abstract

This invention discloses a method for extending the lifespan of a mandrel through a tube based on a composite metal layer using laser processing, belonging to the field of laser processing. The method includes substrate pretreatment, laser cladding, machining, laser thermal spraying, and a two-stage vacuum heat treatment process: using cobalt-copper-based ceramic composite powder as the cladding material, after spiral overlapping cladding and groove removal, "Co-coated CrC" powder is used for laser thermal spraying, followed by two-stage vacuum heat treatment to optimize performance. This invention solves the defects of existing technologies such as easy coating peeling, large thermal deformation, and high cost, enabling the mandrel to possess high-temperature oxidation resistance, wear resistance, and friction reduction properties, significantly improving its lifespan and reducing costs, thus possessing good industrial application value.

Description

Technical Field

[0001] This invention relates to the field of laser processing technology, and more specifically to a method for extending the lifespan of a mandrel through a tube based on a composite metal layer using laser processing. Background Technology

[0002] In the production process of seamless steel pipes, solid bar billets are heated to a high temperature of 1200℃, and then pierced through a conical mandrel at the front end of the mandrel under high speed and high thrust. The mandrel is then removed, and the mandrel is allowed to cool to 70~120℃ before the next operation. The base material of the mandrel is usually 20CrNi3Mo alloy steel, but it is difficult to meet the requirements of continuous operation under the aforementioned harsh conditions, and surface strengthening treatment is necessary to improve its performance.

[0003] Existing surface strengthening methods have many drawbacks:

[0004] Surface oxidation treatment: The adhesion between the coating and the substrate is less than 100MPa. It is easy to peel off under alternating hot and cold conditions and high loads. The service life of the mandrel is only 60 to 200 cycles. Moreover, thermal fatigue cracks can easily extend to 1 to 3 mm of the substrate, resulting in the scrapping of the mandrel.

[0005] Arc welding of cobalt-based alloys: Excessive heat output causes the front end of the mandrel (flat-topped conical part with diameters of φ35±0.1mm to φ175±0.5mm) to bend and deform, failing to meet usage requirements;

[0006] Cobalt / molybdenum / tungsten alloy substrate replacement: extremely high cost, not commensurate with the increase in lifespan, making it difficult to promote industrialization;

[0007] Existing laser-strengthened patents: Patent CN102732878B uses a nickel-based alloy base layer + cobalt-based alloy capping layer, which does not solve the problem of insufficient friction reduction performance; Patent CN101519778B uses a cobalt-based + WC reinforcing phase, which obtains high red hardness at the expense of toughness, has a high tendency to crack, and poor comprehensive mechanical properties under alternating hot and cold working conditions.

[0008] Therefore, there is an urgent need to develop a mandrel processing method that combines long service life, low deformation, low cost, and excellent comprehensive performance to meet the needs of seamless steel pipe industrial production. Summary of the Invention

[0009] The purpose of this invention is to provide a method for extending the service life of a mandrel through tube based on laser processing of a composite metal layer, so as to solve the problems of easy peeling of coating and short service life in the existing surface strengthening technology of mandrel through tube.

[0010] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0011] A laser processing method for extending the lifespan of a mandrel through a tube using a composite metal coating is proposed. The cladding material used in the laser processing technology is a 15-45 μm cobalt-copper-based ceramic composite powder, and its chemical composition is shown below:

[0012] Ni-coated W-Ti-C powder: 33.2~34.5 wt%;

[0013] Cu: 27.3~28.6 wt%

[0014] Mn: 0.4~0.6wt%

[0015] Si: 0.5~0.7wt%

[0016] Co: Balance.

[0017] The "Ni-coated W-Ti-C" in the cobalt-copper-based ceramic composite powder used in the above-mentioned laser processing technology is obtained by separate powder preparation, with a particle size of 15~28μm, and then added to the cobalt-copper-based alloy powder by mechanical mixing to form the cobalt-copper-based ceramic composite powder.

[0018] In the aforementioned "Ni-coated W-Ti-C" alloy powder, the proportion of Ni element is 18.20~19.10wt%; the proportion of W-Ti-C component is the balance.

[0019] In the above-mentioned "Ni-coated W-Ti-C" alloy powder, the proportion of C element is 9.18~9.49wt%, the proportion of Ti element is 25.89~26.18wt%, and the balance is W element.

[0020] A further proposed method for laser cladding is as follows: Laser cladding is performed on a perforated mandrel substrate with no fatigue cracks detected by surface inspection. The selected laser is a fiber laser with a spot size of φ6mm and a power of 5200~5500w. The single-sided cladding thickness is 1.6~1.8mm, the linear velocity is 11~15mm / s, and the overlap rate is 40~45% of the spot diameter. After the parameters are set, spiral overlap cladding is performed. After cladding, the workpiece is machined to remove the grooves of the cladding layer.

[0021] Laser thermal spraying was performed on the cobalt-copper-based composite ceramic cladding layer, and the thermal spraying powder was "Co-coated CrC".

[0022] Furthermore, the laser thermal spraying method is as follows: the selected laser is a fiber laser with a spot size of φ4mm and a power of 5800~6000w, the single-sided spraying thickness is 0.15~0.20mm, the linear velocity is 350~370mm / s, and the overlap rate is 60~65% of the spot diameter; after the parameters are set, spiral overlap thermal spraying is performed.

[0023] Furthermore, in the "Co-coated CrC" alloy powder used in the aforementioned laser thermal spraying, the proportion of Co element is 12.25~14.10wt%; the proportion of CrC component is the balance.

[0024] Furthermore, in the aforementioned "Co-coated CrC" alloy powder, the proportion of C element is 8.59~8.78wt%, with the balance being Cr element.

[0025] A further embodiment of the heat treatment steps for the workpiece after laser thermal spraying is as follows: 4.1 Place the workpiece in a vacuum furnace and heat it to 1020±10℃ at a rate of 8.5~9.5℃ / min, hold it at that temperature for 300±5min, and then cool it with the furnace; 4.2 Place the workpiece in a vacuum furnace and heat it to 800±10℃ at a rate of 15.2~16.7℃ / min, hold it at that temperature for 80±5min, and then remove it from the furnace and cool it.

[0026] Further explanation is provided regarding the selection of components and heat treatment regime for composite metal coatings:

[0027] (a) Co+Cu element combination in cladding layer

[0028] Purpose of element combination: Both Co and Cu are non-carbide forming elements. Their core role is to disperse and strengthen the "Ni-encapsulated W-Ti-C" phase while preventing its decomposition. By fully utilizing the heat resistance of Co and the friction reduction of Cu, the two can also "soften" the cladding layer, thus building a tough platform for the underlying material.

[0029] Selection criteria for element content: After laser cladding, the macroscopic hardness of the matrix phase of the cladding layer needs to reach 280~320 HB, and the cladding layer must not have porosity or crack defects. Based on this, the Cu content needs to be controlled between 27.3wt% and 28.6wt%. If it is lower than 27.3wt%, the hardness of the cladding layer is insufficient; if it is higher than 28.6wt%, the cladding layer is prone to cracking. Co element, as the balance element in the cladding layer, is mainly added according to the amount of "Ni-coated W-Ti-C" alloy powder added.

[0030] (ii) The "Ni-coated W-Ti-C" phase (alloy powder) in the cladding layer

[0031] The purpose of combining elements is to provide high-temperature wear resistance to the cladding layer. WC can synergistically provide high-temperature red hardness. The addition of Ti or TiC mainly reduces the high-temperature decomposition ability of WC, refines the grains of the "Ni-encapsulated W-Ti-C" phase, and further improves the wear resistance of the cladding layer. Ni plays a "bonding + bridging" role in the cladding layer, which can effectively prevent cracking and decomposition of the "W-Ti-C" hard phase.

[0032] The selection criteria for element content: The content range of "Ni-W-Ti-C" is set at 33.2~34.5wt%. This range is determined after considering the hardness and toughness requirements of the cladding layer to ensure that the two are balanced.

[0033] (III) Mn and Si elements in the cladding layer

[0034] Purpose of element combination: The core role of Mn and Si elements is to remove S and O elements from the cladding layer, thus ensuring the smooth formation of the cladding layer.

[0035] Selection of element content: The N and S content in the alloy powder used in this application is both below 400 PPM. Therefore, the Mn content can be controlled at 0.4wt%~0.6wt% to remove the S element. If the Mn content is too high, it will lead to coarsening of the cladding layer structure. In laser cladding, the Si element is used as a metallurgical reaction forming agent. Its content usually needs to be below 1.0wt%. Therefore, this application sets it at 0.5~0.7wt%. If the Si content is too high, it is easy to form slag inclusions. If the content is too low, the cladding layer has poor formability and cannot flow and spread smoothly.

[0036] (iv) "Co-coated CrC" phase (alloy powder) in the spray coating

[0037] Purpose of element combination: Co mainly plays the role of bonding the cladding layer and the "CrC" phase; the "CrC" phase in the sprayed coating is in an unsaturated state and is actually composed of Cr and CrC. As the "consumption" layer in the top composite metal coating, its core function is to be integrated into the cladding layer. The Cr and CrC in it can supplement the cladding layer with antioxidant, friction-reducing and wear-resistant properties.

[0038] The selection criteria for element content are as follows: the proportion of Co is set at 12.25~14.10wt%, which is determined by the powder preparation process, the hardness requirements of the cladding layer, and the toughness requirements; the content of C is set at 8.59~8.78wt%, the purpose of which is to produce unsaturated CrC, so that it forms a Cr-CrC combination, thereby significantly improving the oxidation resistance, friction reduction and wear resistance of the cladding layer.

[0039] (v) Setting of heat treatment system

[0040] The purpose of heat treatment is as follows: The first stage, "heating to 1020±10℃ and holding for 300±5 minutes", aims to eliminate the internal stress of the composite metal coating (especially the spray coating), reduce component segregation, and more importantly, enhance the bonding strength between the "Co-coated CrC" phase and the cladding layer, so as to promote the incorporation of more Cr or Cr-C into the cladding layer through diffusion and embedding. The second stage, "heating to 800±10℃ and holding for 80±5 minutes", aims to promote the precipitation of the "Cu" phase in the cladding layer, increase the proportion of the matrix phase dominated by Co, and thus enhance the heat resistance and friction reduction performance of the cladding layer. In addition, the "cooling after unloading" step in this stage can also improve the hardness of the top substrate.

[0041] Selection of heat treatment parameters: In line with the above heat treatment objectives, the first stage ensures the elimination of internal stress, homogenization of composition, and improvement of the bonding strength between phases by precisely controlling the heating temperature and holding time; the second stage ensures the full precipitation of Cu phase by reasonably setting the temperature and holding time, and further optimizes the hardness of the substrate by cooling after exiting the furnace, ultimately achieving an improvement in the overall performance of the mandrel.

[0042] The present invention has the following beneficial effects:

[0043] This invention utilizes a composite system design of "cobalt-copper-based ceramic composite cladding layer + Co-coated CrC spray coating layer," combined with precise laser processing technology and two-stage vacuum heat treatment, to create a comprehensive performance guarantee for the mandrel insertion tool that combines high toughness, high-temperature wear resistance, oxidation resistance, and friction reduction. This effectively solves the problems of easy coating peeling and poor service stability in existing technologies. At the same time, it eliminates the need for expensive nickel-based or cobalt-based alloys or special substrates, significantly reducing material costs. Furthermore, the precise temperature control characteristics of laser processing greatly reduce thermal deformation during mandrel processing, resulting in strong process stability and facilitating large-scale industrialization. This provides an efficient and reliable technical solution for seamless steel pipe production. Attached Figure Description

[0044] Figure 1 A schematic diagram of a laser-processed perforated mandrel tip;

[0045] Figure 2 A schematic diagram of the coating distribution on the top of a laser-processed perforated mandrel.

[0046] Figure 3 A photograph of the perforated mandrel tip after more than 1,500 perforations on a machine, according to Embodiment 3 provided by the present invention.

[0047] Figure 4 A schematic diagram of the heat treatment process was drawn to illustrate the solution provided by this invention.

[0048] The components include: 100 laser-powder system, 200 perforated mandrel head, 300 perforated mandrel; 1 laser thermal spray coating, 2 laser cladding layer, and 3 substrate. Detailed Implementation

[0049] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0050] Example 1

[0051] The cladding material used in laser processing technology is a cobalt-copper-based ceramic composite powder with a particle size of 15~45μm. Its chemical composition is as follows: Ni-coated W-Ti-C powder 33.2wt%, Cu 27.3wt%, Mn 0.4wt%, Si 0.5wt%, Co balance; wherein "Ni-coated W-Ti-C" is obtained by separate powder preparation, with a particle size of 15~28μm, and its composition is: Ni 18.20wt%, C 9.18wt%, Ti 25.89wt%, W balance, and then added to the cobalt-copper-based alloy powder by mechanical mixing.

[0052] Laser cladding: The operation is carried out on a 20CrNi3Mo alloy steel substrate with no fatigue cracks after surface inspection. A fiber laser with a spot size of φ6mm and a power of 5200w is selected. The cladding thickness on one side is 1.6mm, the linear speed is 11mm / s, and the overlap rate is 40%. After spiral cladding, the groove is removed by machining.

[0053] Laser thermal spraying: A fiber laser with a spot size of φ4mm and a power of 5800w is selected. The single-sided spraying thickness is 0.15mm, the linear speed is 350mm / s, the overlap rate is 60%, and the spraying is done in a spiral overlap manner. The thermal spraying powder is "Co-coated CrC", with the following composition: Co 12.25wt%, C 8.59wt%, and Cr balance.

[0054] Heat treatment: (1) Heat to 1010℃ at 8.5℃ / Min, hold for 295 Min, and cool with the furnace; (2) Heat to 790℃ at 15.2℃ / Min, hold for 75 Min, and cool after being removed from the furnace.

[0055] Example 2

[0056] The cladding material used in laser processing technology is a cobalt-copper-based ceramic composite powder with a particle size of 15~45μm. Its chemical composition is as follows: Ni-coated W-Ti-C powder 34.5wt%, Cu 27.3wt%, Mn 0.6wt%, Si 0.7wt%, Co balance; among which, "Ni-coated W-Ti-C" is obtained by separate powder preparation, with a particle size of 15~28μm, and its composition is: Ni 19.10wt%, C 9.49wt%, Ti 26.18wt%, W balance, and then mechanically mixed into the cobalt-copper-based alloy powder.

[0057] Laser cladding: The operation is carried out on a 20CrNi3Mo alloy steel substrate with no fatigue cracks after surface inspection. A fiber laser with a spot size of φ6mm and a power of 5500w is selected. The cladding thickness on one side is 1.8mm, the linear speed is 15mm / s, and the overlap rate is 45%. After spiral cladding, the groove is removed by machining.

[0058] Laser thermal spraying: A fiber laser with a spot size of φ4mm and a power of 6000w is selected. The single-sided spraying thickness is 0.20mm, the linear speed is 370mm / s, the overlap rate is 65%, and the spraying is done in a spiral overlap manner. The thermal spraying powder is "Co-coated CrC", with the following composition: Co 14.10wt%, C 8.78wt%, and Cr balance.

[0059] Heat treatment: (1) Heat to 1030℃ at 9.5℃ / Min, hold for 305 Min, and cool with the furnace; (2) Heat to 810℃ at 16.7℃ / Min, hold for 85 Min, and cool after being removed from the furnace.

[0060] Example 3

[0061] The cladding material used in laser processing technology is a cobalt-copper-based ceramic composite powder with a particle size of 15~45μm. Its chemical composition is as follows: Ni-coated W-Ti-C powder 33.8wt%, Cu 27.9wt%, Mn 0.5wt%, Si 0.6wt%, Co balance; among which, "Ni-coated W-Ti-C" is obtained by separate powder preparation, with a particle size of 15~28μm, and its composition is: Ni 18.65wt%, C 9.33wt%, Ti 26.03wt%, W balance, and then mechanically mixed into the cobalt-copper-based alloy powder.

[0062] Laser cladding: The operation is carried out on a 20CrNi3Mo alloy steel substrate with no fatigue cracks after surface inspection. A fiber laser with a spot size of φ6mm and a power of 5350w is selected. The cladding thickness on one side is 1.7mm, the linear speed is 14mm / s, and the overlap rate is 42%. After spiral cladding, the groove is removed by machining.

[0063] Laser thermal spraying: A fiber laser with a spot size of φ4mm and a power of 5900w is selected. The single-sided spraying thickness is 0.17mm, the linear speed is 360mm / s, the overlap rate is 62%, and the spraying is done in a spiral overlap manner. The thermal spraying powder is "Co-coated CrC", with the following composition: Co 13.18wt%, C 8.69wt%, and Cr balance.

[0064] Heat treatment: (1) Heat to 1020℃ at 9.0℃ / Min, hold for 300 Min, and cool with the furnace; (2) Heat to 800℃ at 15.9℃ / Min, hold for 80 Min, and cool after being removed from the furnace.

[0065] Summary of test data from the examples

[0066] Example 1

[0067] In this embodiment, the piercing life of the mandrel tip is 1480 cycles, and the front-end thermal deformation is 0.28 mm; compared with nickel-based alloys, the material cost is 88% of that of nickel-based alloys; compared with cobalt-based alloys, the material cost is 67% of that of cobalt-based alloys.

[0068] Example 2

[0069] In this embodiment, the piercing life of the mandrel tip is 1530 cycles, and the thermal deformation at the front end is 0.29 mm; compared with nickel-based alloys, the material cost is 89% of that of nickel-based alloys; compared with cobalt-based alloys, the material cost is 69% of that of cobalt-based alloys.

[0070] Example 3

[0071] In this embodiment, the piercing life of the mandrel tip is 1510 cycles, and the thermal deformation at the front end is 0.25 mm; compared with nickel-based alloys, the material cost is 85% of that of nickel-based alloys; compared with cobalt-based alloys, the material cost is 65% of that of cobalt-based alloys.

[0072] The test results of the above embodiments show that the mandrel heads processed by the method of the present invention all have excellent performance, verifying the effectiveness and stability of the technical solution of the present invention.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for extending the lifespan of a mandrel through a tube based on a composite metal layer using laser processing, characterized in that, Includes the following steps: S1 Substrate Pretreatment: Select the core rod end substrate and confirm that there are no fatigue cracks after surface flaw detection; S2 laser cladding: A fiber laser is used to perform spiral overlapping cladding on the surface of a pretreated substrate. The cladding material is a cobalt-copper-based ceramic composite powder, which contains Co, Cu, Mn, Si and composite hard phase powder containing Ni, W, Ti and C. In the cobalt-copper-based ceramic composite powder, the proportion of composite hard phase powder containing Ni, W, Ti, and C is 33.2~34.5wt%, Cu is 27.3wt%~28.6wt%, Mn is 0.4wt%~0.6wt%, Si is 0.5~0.7wt%, and the balance is Co; S3 Machining: After cladding, the workpiece is machined to remove the grooves on the surface of the cladding layer; S4 laser thermal spraying: A fiber laser is used to perform spiral overlapping thermal spraying on the surface of the cladding layer. The thermal spraying material is a composite powder containing Co, Cr, and C. The composite powder containing Co, Cr, and C is a Co-encapsulated CrC powder, wherein the proportion of Co is 12.25~14.10 wt%, the proportion of C is 8.59~8.78 wt%, and the balance is Cr; S5 Two-Stage Vacuum Heat Treatment: First, heat the workpiece to 980~1050℃ at a rate of 8.5~9.5℃ / Min, hold for 280~320Min, and then cool it in the furnace; then heat the workpiece to 780~820℃ at a rate of 15~17℃ / Min, hold for 70~90Min, and then remove it from the furnace and cool it. The composite hard phase powder containing Ni, W, Ti, and C is Ni-coated W-Ti-C powder with a particle size of 15~28μm, which is added to the cobalt-copper-based alloy powder by mechanical mixing after separate powdering. In the Ni-W-Ti-C powder, Ni accounts for 18.2~19.10 wt%, C accounts for 9.18~9.49 wt%, Ti accounts for 25.89~26.18 wt%, and the balance is W.

2. The method for extending the lifespan of a mandrel based on a composite metal layer using laser processing according to claim 1, characterized in that, The cobalt-copper-based ceramic composite powder has a particle size of 15~45μm.

3. The method for extending the lifespan of a mandrel based on a composite metal layer using laser processing according to claim 1, characterized in that, The laser cladding process parameters are as follows: laser spot size is φ5~7mm, power is 5000~5800w, single-sided cladding thickness is 1.5~2.0mm, linear speed is 10~16mm / s, and overlap rate is 38~48% of the spot diameter.

4. The method for extending the lifespan of a mandrel based on a composite metal layer using laser processing according to claim 1, characterized in that, The process parameters for laser thermal spraying are as follows: laser spot size is φ3~5mm, power is 5600~6200w, single-sided spraying thickness is 0.12~0.22mm, linear speed is 340~380mm / s, and overlap rate is 58~68% of the spot diameter.

5. The method for extending the lifespan of a mandrel based on a composite metal layer using laser processing according to claim 1, characterized in that, The specific parameters for the two-stage vacuum heat treatment are as follows: the first stage is heated to 1010~1030℃ and held for 295~305 minutes; the second stage is heated to 790~810℃ and held for 75~85 minutes.

6. The method for extending the lifespan of a mandrel based on a composite metal layer using laser processing according to claim 1, characterized in that, The substrate of the mandrel core is 20CrNi3Mo alloy steel.

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