Piercing plug for rolling high-alloy steel pipe and preparation method of piercing plug

Abstract

The invention discloses a piercing plug for rolling a high-alloy steel pipe and a preparation method of the piercing plug. The piercing plug for rolling the high-alloy steel pipe comprises a plug base body, a high-strength alloy layer arranged on the plug base body and an oxidation film layer arranged on the high-strength alloy layer. The high-strength alloy layer is made of cobalt-based alloy; the oxidation film layer is made of iron-based alloy. According to the piercing plug for rolling the high-alloy steel pipe, the high-strength alloy layer is designed on the plug base body, the problem that an oxidation film on the surface of the plug falls off due to high-temperature softening of a supporting part is solved, the problem that steel is bonded due to large temperature rise of the surface of the plug is solved by designing the oxidation film layer, and the piercing plug for rolling the high-alloy steel pipe has good high-temperature strength; and the service life is further prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of seamless steel pipe piercing plug manufacturing, and specifically to a piercing plug for high alloy steel pipe rolling and a preparation method thereof, and in particular to a piercing plug with a multilayer structure for high alloy steel pipe rolling and a preparation method thereof. Background Art

[0002] In the production process of hot-rolled piercing of seamless steel pipes, the stress on the plug is complex and the service environment is harsh. Especially in the production process of medium and high alloy steel, due to the large deformation resistance of high alloy steel, the stress on the plug is complex and the service environment is harsh. The surface is prone to problems such as steel sticking, meat falling, cracking and melting loss, which leads to failure. Not only is the life span short and the cost high, but it is also prone to production accidents and quality accidents. The quality and service life directly affect the output, quality and economic benefits of steel pipe production.

[0003] Chinese patent publication number CN 107855366A discloses a steel pipe perforation plug and a preparation method thereof. In this technology, the Cr content is very high, the high alloy steel matrix is ​​not conducive to obtaining a high-quality oxide film, and it is difficult to obtain good high temperature resistance and heat insulation effects with a single material.

[0004] Chinese patent publication number CN 104364414 A discloses a piercing plug and a method for manufacturing the piercing plug. The piercing plug of this technology comprises a plug body and a spray coating containing iron and iron oxide formed on the surface of the plug body, and the chemical composition of the spray coating; however, in this technology, the spray coating has a weak bonding force with the substrate and is prone to fall off, thereby reducing the life of the plug.

[0005] In view of the above situation, it is urgent to develop a new perforation plug and its preparation method, which can solve the problems existing in the single material plug design, such as insufficient thermal strength of the substrate, poor bonding between the oxide film and the substrate, and easy cracking and peeling of the oxide film. Summary of the invention

[0006] In view of the problems existing in the prior art that can be solved in the design of a single material plug, such as insufficient thermal strength of the substrate, poor bonding between the oxide film and the substrate, and easy cracking and peeling of the oxide film, the purpose of the present invention is to provide a perforated plug for rolling a high-alloy steel pipe and a preparation method thereof. By designing a high-strength alloy layer on the plug substrate, the problem of the oxide film on the surface of the plug softening at high temperature and falling off of the supporting part is solved, and the problem of the temperature rise on the surface of the plug sticking to the steel is solved by designing the oxide film layer, so that the perforated plug for rolling a high-alloy steel pipe has good high-temperature strength, and at the same time the surface has a good lubricating oxide film and does not stick to the steel, thereby further improving the service life.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A first aspect of the present invention provides a piercing plug for high alloy steel pipe rolling, comprising a plug substrate, a high strength alloy layer provided on the plug substrate, and an oxide film layer provided on the high strength alloy layer;

[0009] The material of the high-strength alloy layer is cobalt-based alloy;

[0010] The material of the oxide film layer is iron-based alloy.

[0011] Preferably, the high-strength alloy layer comprises the following components by weight percentage: Co: 45-49%, Cr: 15-30%, W: 13-20%, Ni: 10-20%, Fe: 6-12%, Mn: 0.3-0.9%, Mo: 0.3-0.9%.

[0012] Preferably, the high-strength alloy layer has a thickness of 1 to 10 mm.

[0013] Preferably, the oxide film layer comprises the following components by weight percentage: C: 0.15-0.40%, Cr: 1-5%, and the balance is iron.

[0014] Preferably, the oxide film layer further includes Ni: 2.5-3.5%.

[0015] Preferably, the oxide film layer includes V: 0.20-0.50%, W: 7.5-9.0%.

[0016] Preferably, the oxide film layer has a thickness of 0.1 to 1.3 mm.

[0017] Preferably, a cemented carbide phase WC is added to the oxide film layer.

[0018] Preferably, the plug substrate is made of one of 20CrNi3, 3Cr2W8V and 35CrMo.

[0019] The second aspect of the present invention provides a method for preparing a perforated plug for rolling a high-alloy steel pipe as described in the first aspect of the present invention, wherein a plug substrate of the perforated plug is obtained by machining, a high-strength alloy layer is clad on the surface of the plug substrate of the perforated plug by laser cladding, and then an oxide film layer is clad on the surface of the high-strength alloy layer to obtain a perforated plug for rolling a high-alloy steel pipe.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The perforated plug for high alloy steel pipe rolling and the preparation method thereof of the present invention solve the problem of the oxide film on the plug surface softening and falling off due to the high temperature of the support part by designing a high-strength alloy layer on the plug substrate, and solve the problem of the plug surface sticking to steel due to large temperature rise by designing the oxide film layer, so that the perforated plug for high alloy steel pipe rolling has good high temperature strength, and at the same time, the surface has a good lubricating oxide film and does not stick to steel, further improving the service life;

[0022] 2. The high-strength alloy layer of the perforated plug for high-alloy steel pipe rolling of the present invention provides a solid support for the oxide film layer in a high-temperature service environment, and the oxide film layer plays a role of lubrication and heat insulation; the surface hardness and wear resistance of the perforated plug for high-alloy steel pipe rolling are greatly improved, and it is repairable, which meets the requirements of national green manufacturing;

[0023] 3. The piercing plug for high alloy steel pipe rolling of the present invention has good high temperature strength and a service life of 26 to 30 times longer than the original one. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0025] Figure 1 The present invention is a schematic structural diagram of a piercing plug for rolling a high alloy steel pipe. DETAILED DESCRIPTION

[0026] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form.

[0027] The piercing plug for high alloy steel pipe rolling provided by the present invention has good high temperature strength and a service life of 26 to 30 times that of the original piercing plug.

[0028] Combination Figure 1 As shown, a piercing plug for high alloy steel pipe rolling provided by the present invention comprises a plug base 1, a high strength alloy layer 2 arranged on the plug base 1 and an oxide film layer 3 arranged on the high strength alloy layer 2.

[0029] The material of the high-strength alloy layer is a cobalt-based alloy; in a specific embodiment, the high-strength alloy layer provides a solid support for the oxide film layer in a high-temperature service environment, and includes the following components by weight percentage: Co: 45-49%, Cr: 15-30%, W: 13-20%, Ni: 10-20%, Fe: 6-12%, Mn: 0.3-0.9%, Mo: 0.3-0.9%;

[0030] In the above-mentioned high-strength alloy layer, the design principles of each component are as follows:

[0031] Co: Co has a high melting point. Adding Co is beneficial to improving the material's high temperature load-bearing capacity, thermal corrosion resistance, cold and thermal fatigue resistance, and high temperature creep resistance. However, if the Co content is too high, the cost is high, the cost-effectiveness of the material is reduced, and the application range of the material is limited; therefore, the Co content is controlled at 45-49%.

[0032] Cr: Increasing the Cr content can effectively improve the material's antioxidant properties, thereby inhibiting the oxidation-wear interaction promotion mechanism and improving wear resistance. Cr combines with C to form carbides, which can also improve wear resistance. However, if the Cr content continues to increase, it will cause a decrease in the amount of other alloying elements added, which is not conducive to improving hardness and wear resistance. Moreover, too high a Cr content will make it easy for the blank and the tool to stick together under high temperature and high pressure, resulting in tool failure or. Therefore, the Cr content is controlled at 15-30%.

[0033] W: W can improve the high temperature strength of the material, improve the thermal strength, and improve the strength through solid solution and the formation of carbides, Co3W and other intermetallic compounds and other strengthening precipitation phases. However, when the content is too high, it is not good for the welding quality, and it is easy to form too many brittle phases such as intermetallic compounds to reduce the toughness of the cladding layer. Therefore, the W content is controlled at 13-20%.

[0034] Ni: Ni can improve the high temperature strength of the material and improve the toughness, improve the fluidity of the welding cladding process, thereby improving the quality of the cladding layer and preventing the occurrence of welding cracks. However, if the Ni content is too high, the cost is high, the cost performance of the material is reduced, and the application range of the material is limited. Therefore, the Ni content is controlled at 10-20%.

[0035] Fe: Fe can improve the plasticity and toughness of Co-based alloys, improve machinability, and help reduce the Fe element content gradient between the cladding layer and the iron-based material, thereby reducing the difference between dissimilar metals on both sides of the interface and improving the interface bonding strength, but excessive content reduces high-temperature strength. Therefore, the Fe content is controlled at 6-12%.

[0036] Mn: Mn can improve the machinability of Co-based alloys and help reduce the content gradient of Mn elements between the cladding layer and the iron-based material, thereby reducing the difference between dissimilar metals on both sides of the interface and improving the interface bonding strength, but excessive content reduces high strength. Therefore, the Mn content is controlled at 0.3-0.9%.

[0037] Mo: Mo can strengthen the solid solution and form intermetallic compounds such as Co3Mo to improve the strength, but when the content is too high, it is not good for the welding quality, and it is easy to form too many brittle phases such as intermetallic compounds to reduce the toughness of the cladding layer. Therefore, the Mo content is controlled at 0.3-0.9%.

[0038] In a specific embodiment, the thickness of the high-strength alloy layer is 1 to 10 mm.

[0039] The material of the oxide film layer is an iron-based alloy; in a specific embodiment, the oxide film layer plays a role of lubrication and heat insulation, and includes the following components by weight percentage: C: 0.15-0.40%, Cr: 1-5%, and the balance is iron.

[0040] In the above-mentioned oxide film layer, C:C is a carbide-forming element, which can improve the strength of the perforated plug, including room temperature and high temperature strength, through solid solution strengthening and precipitation strengthening. However, too high C will be detrimental to the toughness of the plug and reduce the resistance to cold and hot fatigue, and too high C is not conducive to the formation of oxide film, because the reaction of oxygen and carbon takes precedence over the reaction of oxygen and iron. Therefore, the present invention needs to control the C content between 0.15 and 0.40%. Cr: Cr is conducive to the formation of an oxide film with good adhesion to the matrix on the surface, but too high Cr content is not conducive to the oxidation of the grain boundary before the matrix to generate more oxide film-matrix bonding tentacles per unit area, resulting in a decrease in the oxide film-matrix bonding force. Cr can also combine with carbon to form carbides to improve high temperature strength. Therefore, the present invention needs to control the Cr content between 1.00 and 5.00%.

[0041] In a specific embodiment, the oxide film layer includes Ni: 2.50-3.50%; Ni: Ni is a solid solution strengthening element that is beneficial to improving the high temperature strength of the matrix, and can also improve the hardenability of the material, preventing the formation of more ferrite soft phases due to surface decarburization during the high temperature oxidation process of the plug, which leads to a decrease in the surface high temperature strength; Ni will form Ni-rich particles in the inner oxide film formed during the high temperature oxidation heat treatment, which is beneficial to improving the internal bonding force of the oxide film. However, if the Ni content is too high, the manufacturing cost of the plug is high, and the Ni content is too high, which will reduce the phase transition temperature point of the material from the ferrite phase to the austenite phase, making the material more susceptible to austenite phase transition due to temperature rise during use. In the subsequent cooling process, the austenite is transformed into martensite or bainite, thereby causing fatigue damage and generating internal stress due to phase transition, thereby reducing the resistance to cold and hot fatigue. Therefore, the present invention needs to control the Ni content between 2.50 and 3.50%.

[0042] In a specific embodiment, the oxide film layer also includes V: 0.20-0.50%, W: 7.5-9.0%; V mainly plays a role in refining grains and improving the toughness of the material. Too high a V content is not good for the high-temperature oxidation resistance of steel, so the present invention needs to control the V content to 0.20-0.50%. W forms carbides, which exist in the material as M6C and MC type carbides. This type of carbide has the characteristics of high hardness and can significantly improve the high-temperature strength of the material. If the W content is too high, there is a tendency to reduce the thermal conductivity, so the present invention needs to control the W content to 7.5-9.0%.

[0043] In a specific embodiment, the thickness of the oxide film layer is 0.1-1.3 mm.

[0044] In a specific embodiment, hard alloy phase tungsten carbide WC is added to the oxide film layer to improve the bonding strength between the oxide film layer and the substrate.

[0045] In a specific embodiment, the plug base mainly serves to connect the ejector rod in the structure and provide a welding base for the high-strength alloy layer; the plug base is made of one of 20CrNi3, 3Cr2W8V, 35CrMo and the like.

[0046] The preparation method of the above-mentioned perforated plug for rolling high-alloy steel pipes is to obtain the plug substrate of the perforated plug by machining, to clad a high-strength alloy layer on the surface of the plug substrate of the perforated plug by laser cladding, and then to clad an oxide film layer on the surface of the high-strength alloy layer to obtain the perforated plug for rolling high-alloy steel pipes; in the above-mentioned laser cladding process, the laser power used is 1000~2900w, and the alloy powder conveying rate is 20~150g / min.

[0047] A piercing plug for rolling a high alloy steel pipe and a preparation method thereof are further introduced below with reference to specific examples.

[0048] Example 1

[0049] Combination Figure 1 As shown, the piercing plug for rolling high alloy steel pipe in this embodiment includes a plug base 1, which is made of 20CrNi3 steel and mainly serves to connect the push rod and provide a welding base for the high strength alloy layer 2 in the structure.

[0050] First, the plug base 1 is machined to obtain the required geometric dimensions to ensure that the subsequent high-strength alloy layer 2 and the oxide film layer 3 have a certain machining allowance after welding, and to ensure that the thickness of the oxide film layer 3 is 0.1-1.3 mm after obtaining the plug shape that meets the requirements. On the surface of the plug base 1, a layer of high-strength alloy layer 2, such as a cobalt-based alloy, is clad by laser cladding, and its composition is shown in Table 1. Its thickness is 1-10 mm, which plays a role in providing solid support for the oxide film layer. On the surface of the high-strength alloy layer 2, another layer of oxide film 3 is welded. The material of the oxide film 3 is 20CrNi4 powder, and its composition is shown in Table 1. The oxide film layer is added with hard alloy phase WC; the welding process is laser cladding, and the thickness of the oxide film 3 is 0.3-1.3 mm. Then, the geometric dimensions that meet the requirements are obtained by machining.

[0051] The strength of the perforated plug is greatly improved by the above process, which can not only meet the rigidity required for perforation, but also has good high temperature resistance. The service life is expressed by the number of perforations. The number of perforations of the perforated plug for high alloy steel pipe rolling in this embodiment can reach 30 times, that is, 30 zirconium alloy steel pipes are prepared, which can reach 30 times of the original perforated plug (which is made of 20CrNi3 material and has 1 perforation). The oxide film layer may be partially worn after a period of use, which can be repaired by turning off and then melting the oxide film layer, and the cost can be reduced by recycling.

[0052] Example 2

[0053] Combination Figure 1 As shown, the piercing plug for rolling high alloy steel pipe in this embodiment includes a plug base 1, which is made of 35CrMo steel and mainly serves to connect the push rod and provide a welding base for the high strength alloy layer 2 in the structure.

[0054] First, the plug base 1 is machined to obtain the required geometric dimensions to ensure that the subsequent high-strength alloy layer 2 and the oxide film layer 3 have a certain machining allowance after welding, and to ensure that the thickness of the oxide film layer 3 is 0.1 to 1.3 mm after the plug shape that meets the requirements is obtained. On the surface of the plug base 1, a layer of high-strength alloy layer 2, such as a cobalt-based alloy, is clad by laser cladding, and its composition is shown in Table 1. Its thickness is 1 to 10 mm, which plays a role in providing solid support for the oxide film layer. On the surface of the high-strength alloy layer 2, another layer of oxide film layer 3 is welded. The material of the oxide film layer 3 is an iron-based alloy powder, and its composition is shown in Table 1. The oxide film layer is added with a hard alloy phase WC; the welding process is laser cladding, and the thickness of the oxide film layer 3 is 0.1 to 1.3 mm, and then the geometric dimensions that meet the requirements are obtained by machining.

[0055] The strength of the perforated plug has been greatly improved through the above process, which can not only meet the rigidity required for perforation, but also has good high temperature resistance. The service life is expressed by the number of perforations. The number of perforations of the perforated plug for high alloy steel pipe rolling in this embodiment can reach 26 times, that is, 26 zirconium alloy steel pipes are prepared, which can reach 26 times of the original perforated plug (which is made of 20CrNi3 material and has a perforation number of 1 time). The oxide film layer may be partially worn after a period of use, which can be repaired by turning off and then melting the oxide film layer, and the cost can be reduced by recycling.

[0056] Example 3

[0057] Combination Figure 1As shown, the piercing plug for rolling high alloy steel pipe in this embodiment includes a plug base 1, the material of the plug base is 3Cr2W8V steel, which mainly connects the push rod in the structure and provides a welding base for the high strength alloy layer 2.

[0058] First, the plug base 1 is machined to obtain the required geometric dimensions to ensure that the subsequent high-strength alloy layer 2 and the oxide film layer 3 have a certain machining allowance after welding, and to ensure that the thickness of the oxide film layer 3 is 0.1 to 1.3 mm after the plug shape that meets the requirements is obtained. On the surface of the plug base 1, a layer of high-strength alloy layer 2, such as a cobalt-based alloy, is clad by laser cladding, and its composition is shown in Table 1. Its thickness is 1 to 10 mm, which plays a role in providing solid support for the oxide film layer. On the surface of the high-strength alloy layer 2, another layer of oxide film layer 3 is welded. The material of the oxide film layer 3 is an iron-based alloy powder, and its composition is shown in Table 1. The oxide film layer is added with a hard alloy phase WC; the welding process is laser cladding, and the thickness of the oxide film layer 3 is 0.1 to 1.3 mm, and then the geometric dimensions that meet the requirements are obtained by machining.

[0059] The strength of the perforated plug is greatly improved by the above process, which can not only meet the rigidity required for perforation, but also has good high temperature resistance. The service life is expressed by the number of perforations. The number of perforations of the perforated plug for high alloy steel pipe rolling in this embodiment can reach 29 times, that is, 29 zirconium alloy steel pipes are prepared, which can reach 29 times of the original perforated plug (which is made of 20CrNi3 material and has a perforation number of 1 time). The oxide film layer may be partially worn after a period of use, which can be repaired by turning off and then melting the oxide film layer, and the cost can be reduced by recycling.

[0060] Example 4

[0061] Combination Figure 1 As shown, the piercing plug for rolling high alloy steel pipe in this embodiment includes a plug base 1, the material of the plug base is 3Cr2W8V steel, which mainly connects the push rod in the structure and provides a welding base for the high strength alloy layer 2.

[0062] First, the plug base 1 is machined to obtain the required geometric dimensions to ensure that the subsequent high-strength alloy layer 2 and the oxide film layer 3 have a certain machining allowance after welding, and to ensure that the thickness of the oxide film layer 3 is 0.1 to 1.3 mm after the plug shape that meets the requirements is obtained. On the surface of the plug base 1, a layer of high-strength alloy layer 2, such as a cobalt-based alloy, is clad by laser cladding, and its composition is shown in Table 1. Its thickness is 1 to 10 mm, which plays a role in providing solid support for the oxide film layer. On the surface of the high-strength alloy layer 2, another layer of oxide film layer 3 is welded. The material of the oxide film layer 3 is an iron-based alloy powder, and its composition is shown in Table 1. The oxide film layer is added with a hard alloy phase WC; the welding process is laser cladding, and the thickness of the oxide film layer 3 is 0.1 to 1.3 mm, and then the geometric dimensions that meet the requirements are obtained by machining.

[0063] The strength of the perforated plug is greatly improved by the above process, which can not only meet the rigidity required for perforation, but also has good high temperature resistance. The service life is expressed by the number of perforations. The number of perforations of the perforated plug for high alloy steel pipe rolling in this embodiment can reach 27 times, that is, 27 zirconium alloy steel pipes are prepared, which can reach 27 times of the original perforated plug (which is made of 20CrNi3 material and has a perforation number of 1 time). The oxide film layer may be partially worn after a period of use, which can be repaired by turning off and then melting the oxide film layer, and the cost can be reduced by recycling.

[0064] Example 5

[0065] Combination Figure 1 As shown, the piercing plug for rolling high alloy steel pipe in this embodiment includes a plug base 1, which is made of 35CrMo steel and mainly serves to connect the push rod and provide a welding base for the high strength alloy layer 2 in the structure.

[0066] First, the plug base 1 is machined to obtain the required geometric dimensions to ensure that the subsequent high-strength alloy layer 2 and the oxide film layer 3 have a certain machining allowance after welding, and to ensure that the thickness of the oxide film layer 3 is 0.1 to 1.3 mm after the plug shape that meets the requirements is obtained. On the surface of the plug base 1, a layer of high-strength alloy layer 2, such as a cobalt-based alloy, is clad by laser cladding, and its composition is shown in Table 1. Its thickness is 1 to 10 mm, which plays a role in providing solid support for the oxide film layer. On the surface of the high-strength alloy layer 2, another layer of oxide film layer 3 is welded. The material of the oxide film layer 3 is an iron-based alloy powder, and its composition is shown in Table 1. The oxide film layer is added with a hard alloy phase WC; the welding process is laser cladding, and the thickness of the oxide film layer 3 is 0.1 to 1.3 mm, and then the geometric dimensions that meet the requirements are obtained by machining.

[0067] The strength of the perforated plug is greatly improved by the above process, which can not only meet the rigidity required for perforation, but also has good high temperature resistance. The service life is expressed by the number of perforations. The number of perforations of the perforated plug for high alloy steel pipe rolling in this embodiment can reach 28 times, that is, 28 zirconium alloy steel pipes are prepared, which can reach 28 times of the original perforated plug (which is made of 20CrNi3 material and has a perforation number of 1 time). The oxide film layer may be partially worn after a period of use, which can be repaired by turning off and then melting the oxide film layer, and the cost can be reduced by recycling.

[0068] Example 6

[0069] Combination Figure 1 As shown, the piercing plug for rolling high alloy steel pipe in this embodiment includes a plug base 1, which is made of 20CrNi3 steel and mainly serves to connect the push rod and provide a welding base for the high strength alloy layer 2 in the structure.

[0070] First, the plug base 1 is machined to obtain the required geometric dimensions to ensure that the subsequent high-strength alloy layer 2 and the oxide film layer 3 have a certain machining allowance after welding, and to ensure that the thickness of the oxide film layer 3 is 0.1 to 1.3 mm after the plug shape that meets the requirements is obtained. On the surface of the plug base 1, a layer of high-strength alloy layer 2, such as a cobalt-based alloy, is clad by laser cladding, and its composition is shown in Table 1. Its thickness is 1 to 10 mm, which plays a role in providing solid support for the oxide film layer. On the surface of the high-strength alloy layer 2, another layer of oxide film layer 3 is welded. The material of the oxide film layer 3 is an iron-based alloy powder, and its composition is shown in Table 1. The oxide film layer is added with a hard alloy phase WC; the welding process is laser cladding, and the thickness of the oxide film layer 3 is 0.1 to 1.3 mm, and then the geometric dimensions that meet the requirements are obtained by machining.

[0071] The strength of the perforated plug is greatly improved by the above process, which can not only meet the rigidity required for perforation, but also has good high temperature resistance. The service life is expressed by the number of perforations. The number of perforations of the perforated plug for high alloy steel pipe rolling in this embodiment can reach 29 times, that is, 29 zirconium alloy steel pipes are prepared, which can reach 29 times of the original perforated plug (which is made of 20CrNi3 material and has a perforation number of 1 time). The oxide film layer may be partially worn after a period of use, which can be repaired by turning off and then melting the oxide film layer, and the cost can be reduced by recycling.

[0072] Table 1 Material and service life of piercing plug

[0073]

[0074]

[0075] In summary, the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A piercing plug for rolling a high alloy steel pipe, characterized in that: It comprises a plug substrate, a high-strength alloy layer arranged on the plug substrate, and an oxide film layer arranged on the high-strength alloy layer; The material of the high-strength alloy layer is cobalt-based alloy; The material of the oxide film layer is iron-based alloy.

2. The piercing plug for high alloy steel pipe rolling according to claim 1, characterized in that: The high-strength alloy layer includes the following components by weight percentage: Co: 45-49%, Cr: 15-30%, W: 13-20%, Ni: 10-20%, Fe: 6-12%, Mn: 0.3-0.9%, and Mo: 0.3-0.9%.

3. The piercing plug for rolling a high alloy steel pipe according to claim 1, characterized in that: The thickness of the high-strength alloy layer is 1 to 10 mm.

4. The piercing plug for high alloy steel pipe rolling according to claim 1, characterized in that: The oxide film layer includes the following components by weight percentage: C: 0.15-0.40%, Cr: 1-5%, and the balance is iron.

5. The piercing plug for high alloy steel pipe rolling according to claim 4, characterized in that: The oxide film layer also includes Ni: 2.5-3.5%.

6. The piercing plug for rolling a high alloy steel pipe according to claim 4, characterized in that: The oxide film layer includes V: 0.20-0.50%, W: 7.5-9.0%.

7. The piercing plug for high alloy steel pipe rolling according to claim 1, characterized in that: The thickness of the oxide film layer is 0.1-1.3 mm.

8. The piercing plug for high alloy steel pipe rolling according to claim 1, characterized in that: The oxide film layer contains cemented carbide phase WC.

9. The piercing plug for high alloy steel pipe rolling according to claim 1, characterized in that: The plug substrate is made of one of 20CrNi3, 3Cr2W8V and 35CrMo.

10. A method for preparing a piercing plug for rolling a high alloy steel pipe according to any one of claims 1 to 9, characterized in that: A plug substrate of a piercing plug is obtained by machining, a high-strength alloy layer is clad on the surface of the plug substrate of the piercing plug by laser cladding, and then an oxide film layer is clad on the surface of the high-strength alloy layer to obtain a piercing plug for rolling a high-alloy steel pipe.

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