A wear-resistant composite piercing machine top head and surface overlay manufacturing method

Abstract

The application provides a wear-resistant composite piercing mill head manufacturing method and a piercing mill head, and the manufacturing method comprises the following steps: S1, preparing a steel base head; S2, adopting a submerged-arc welding process to make a flux-cored wire cladded on a working cone surface and a nose end surface of the steel base head, so as to form a cladding layer with a thickness of 6-8 mm; and S3, pre-oxidizing the cladding layer of the steel base head at high temperature, so that the wear-resistant composite piercing mill head is obtained. The wear-resistant composite piercing mill head manufacturing method has a dense and uniform oxide film on the surface of the cladding layer of the piercing mill head, the oxide film is firmly combined with the cladding layer, and the existence of the dense and uniform oxide film can reduce the power consumption of a steel pipe piercing mill and prolong the service life of the piercing mill head.

Description

Technical Field

[0001] This invention relates to the field of perforation machine mandrel technology, and in particular to a method for manufacturing a wear-resistant composite perforation machine mandrel and the perforation machine mandrel itself. Background Technology

[0002] The mandrel of the tube threading machine is an important hot-working mold in the production of seamless steel pipes.

[0003] During the production of seamless steel pipes, the mandrel of the pipe threading machine is subjected to repeated high temperature and extrusion pressure, which can cause problems such as oxide scale peeling off, nose collapse, longitudinal cracking of the mandrel, and adhesion of steel pipes. These problems directly affect the service life of the mandrel and the qualification rate of seamless steel pipe products.

[0004] Existing patent number CN101391265 also discloses a steel-based composite material for a seamless steel pipe casting mandrel and its preparation method. It utilizes a combustion synthesis chemical reaction within the cavity of a negative pressure casting mold to form a 15-20 mm thick TiC ceramic-metal reinforced region at the leading edge of the mandrel; the bond between the ceramic reinforced region and the mandrel is a metallurgical bond. The process is as follows: 1) Ti powder, C powder, and Ni powder are used as reactants, mixed evenly in a certain proportion, and pressed into a billet; 2) The degassed billet is placed in the cavity of the negative pressure casting mold at the corresponding position of the mandrel requiring reinforcement, and the vacuum suction of the negative pressure sand box is maintained. Then, high-temperature hot-working die steel is poured into the mold, igniting the chemical reaction within the billet to form TiC ceramic particles, thereby preparing the mandrel casting blank; 3) The mandrel casting blank is machined by turning or grinding to meet the mandrel design dimensional requirements.

[0005] However, the oxide film on the surface of the aforementioned perforating machine mandrel is thin, the bonding strength between the oxide film and the substrate is low, the oxide scale on the surface of the perforating machine mandrel is easy to fall off, collapse, the perforating machine mandrel is prone to longitudinal cracking, and the service life of the perforating machine mandrel is limited. Summary of the Invention

[0006] To address the aforementioned problems, this invention aims to solve the problems described above. One object of this invention is to provide a method for manufacturing a wear-resistant composite piercing machine mandrel and a piercing machine mandrel that solves the above problems.

[0007] A method for manufacturing a wear-resistant composite piercing mill mandrel involves first melting a steel-based mandrel material in a medium-frequency induction furnace and casting it into a mandrel blank. This blank is then subjected to rough machining and heat treatment to obtain the steel-based mandrel. Finally, a submerged arc welding machine is used on the working cone surface and the nose end face of the steel-based mandrel to... flux-cored welding wireA wear-resistant and heat-resistant cladding layer with a thickness of 6-8 mm is obtained by cladding the working cone surface and nose end face of the mandrel. The mandrel is then precision machined to the specified dimensions and precision. Finally, the cladding layer is pre-oxidized at high temperature to obtain the wear-resistant composite piercing machine mandrel. The specific process steps are as follows:

[0008] First, the steel-based mandrel material is smelted in a medium-frequency induction furnace, and then cast into a mandrel blank using the lost foam casting method. The pouring temperature of the molten steel is 1544-1559℃. The chemical composition and mass fraction of the mandrel blank are: 0.19-0.25% C, 1.88-2.13% Cr, 1.03-1.26% Si, 4.12-4.30% Mn, 0.37-0.48% Ta, 1.36-1.49% Nb, 0.11-0.15% Ca, 0.14-0.18% K, 0 0.00-0.020% S, 0.00-0.025% P, balance Fe and unavoidable impurities; After sand removal, grinding and rough machining, the mandrel blank is heated in the furnace to 980-1000℃, held for 60-80 minutes, then furnace cooled to 880-895℃, held for 90-120 minutes, and then oil-quenched in quenching oil at 20-35℃ for 15-20 minutes, and then air-cooled to room temperature to obtain the steel-based mandrel; The working conical surface and nose end face of the steel-based mandrel are welded using a submerged arc welding machine to... flux-cored welding wire A wear-resistant and heat-resistant cladding layer with a thickness of 6-8mm is obtained by cladding the working cone surface and nose end face of the mandrel, and the mandrel is then precision machined to the specified dimensions and precision. flux-cored welding wire The chemical composition and mass fraction of the wear-resistant and heat-resistant cladding layer with a diameter of 2.0-2.5 mm are as follows: 0.67-0.75% C, 3.12-3.28% B, 18.04-18.31% Al, 33.51-33.77% Cr, 6.23-6.38% Co, 8.62-8.80% Mo, 3.73-3.91% Nb, 0.27-0.35% Y, 15.64-15.83% Ni, 0.00-0.022% S, 0.00-0.025% P, with the balance being Fe and unavoidable impurities;

[0009] After finishing, the mandrel is heated to 880-895℃ in a heat treatment furnace. Water vapor is then introduced into the furnace at a rate of 120-150 ml / min, and the temperature is maintained for 90-120 minutes. Then, the water vapor is stopped, and the mandrel is cooled to 750-780℃ in the furnace and maintained for 60-80 minutes. After the furnace cools to below 150℃, the mandrel is removed from the furnace and air-cooled to room temperature to obtain a wear-resistant composite piercing machine mandrel.

[0010] This invention discloses a method for manufacturing a wear-resistant composite piercing mill mandrel and the mandrel itself. First, a steel-based mandrel material is smelted in a medium-frequency induction furnace, a simple and efficient process with good control over the mandrel's composition. The mandrel blank is then cast using lost foam casting at a temperature of 1544-1559℃. Lost foam casting yields mandrel blanks with excellent appearance and internal quality, ensuring the mandrel possesses superior mechanical properties. The chemical composition and mass fraction of the mandrel blank are: 0.19-0.25% C, 1.88-2.13% Cr, 1.03-1.26% Si, 4.12-4.30% Mn, 0.37-0.48% Ta, 1.36-1.49% Nb, 0.11-0.15% Ca, 0.14-0.18% K, 0.00-0.020% S, 0.00-0.025% P, balance Fe and unavoidable impurities. Adding 1.88-2.13% Cr, 1.03-1.26% Si, 4.12-4.30% Mn, 0.37-0.48% Ta, and 1.36-1.49% Nb can improve the room temperature strength of the mandrel. In particular, the addition of 0.37-0.48% Ta and 1.36-1.49% Nb can significantly improve the high-temperature strength of the mandrel matrix and prevent deformation during use. Furthermore, adding 0.11-0.15% Ca and 0.14-0.18% K can change the morphology and distribution of inclusions. In particular, the addition of 0.14-0.18% K can lower the solidification temperature of the molten steel, refine the grains, and significantly improve the toughness and plasticity of the mandrel.

[0011] The mandrel blank of this invention, after sand removal, grinding, and rough machining, is heated in a furnace to 980-1000℃ and held for 60-80 minutes. It is then furnace cooled to 880-895℃ and held for 90-120 minutes. Finally, it undergoes oil quenching in quenching oil at 20-35℃ for 15-20 minutes, followed by air cooling to room temperature to obtain a steel-based mandrel. The initial furnace heating to 980-1000℃ for 60-80 minutes primarily aims to homogenize the microstructure, improve the stability of high-temperature austenite, remove Widmanstätten structure from the as-cast microstructure, and prevent the formation of pearlite in the oil-quenched microstructure. The furnace cooling to 880-895℃ for 90-120 minutes followed by oil quenching in quenching oil at 20-35℃, by lowering the quenching temperature, refines the size of the martensite and bainite obtained after quenching, which is beneficial for improving the strength and toughness of the mandrel. The quenching and holding time is controlled at 15-20 minutes to achieve a quenched microstructure mainly composed of martensite and bainite, with a small amount of retained austenite, giving the mandrel excellent strength and toughness.

[0012] The steel-based mandrel obtained after oil cooling is then welded using a submerged arc welding machine on its working conical surface and nose end face. medicine Core welding wireA wear-resistant and heat-resistant cladding layer with a thickness of 6-8 mm is obtained by cladding the working conical surface and nose end face of the mandrel, and the mandrel is then precision machined to the specified dimensions and precision. A submerged arc welding machine is used to melt materials with a diameter of 2.0-2.5 mm. flux-cored welding wire This method achieves high efficiency and a dense cladding layer, ensuring excellent metallurgical bonding between layers and between layers and layers. The chemical composition and mass fraction of the wear-resistant and heat-resistant cladding layer of this invention are: 0.67-0.75% C, 3.12-3.28% B, 18.04-18.31% Al, 33.51-33.77% Cr, 6.23-6.38% Co, 8.62-8.80% Mo, 3.73-3.91% Nb, 0.27-0.35% Y, 15.64-15.83% Ni, 0.00-0.022% S, 0.00-0.025% P, with the balance being Fe and unavoidable impurities. The addition of 18.04-18.31% Al and 33.51-33.77% Cr is primarily beneficial for obtaining a dense oxide layer during the subsequent oxidation process. In particular, the addition of 3.12-3.28% B, besides generating high-hardness Cr2B and Cr7(B,C)3 borides to improve the wear resistance of the cladding layer, also promotes the formation of B3O2-Cr2O3-Al2O3 composite oxides during the subsequent oxidation process, further enhancing the fineness and density of the oxides and improving their toughness and adhesion to the wear-resistant and heat-resistant cladding layer, preventing cracking and peeling of the oxide on the mandrel surface during use. The addition of 6.23-6.38% Co, 8.62-8.80% Mo, and 3.73-3.91% Nb also contributes to improving the wear resistance and heat resistance of the cladding layer. The addition of 15.64-15.83% Ni can increase the strength of the cladding layer. In particular, the addition of 0.27-0.35% Y not only refines the cladding coating and improves its strength, toughness, and density, but also improves the melting process of submerged arc welding machines. flux-cored welding wire At that time, the appearance quality of the obtained coating.

[0013] This invention involves heating the precision-machined mandrel in a heat treatment furnace to 880-895°C, then introducing steam at a rate of 120-150 ml / min to create a high-temperature oxidizing atmosphere. Holding this temperature for 90-120 minutes promotes the formation of a fine, dense oxide film within the wear-resistant and heat-resistant coating on the mandrel, improving its performance. However, the steam introduction time should not be too long, as this increases the oxide film thickness and internal stress, making it prone to cracking and peeling during use. After 90-120 minutes of steam introduction, the steam is stopped, and the mandrel is cooled in the furnace to 750-780°C and held for 60-80 minutes. This helps reduce internal stress in the coating. After cooling to below 150°C, the mandrel is removed from the furnace and air-cooled to room temperature, further eliminating internal stress and extending its service life, ultimately resulting in a wear-resistant composite piercing machine mandrel.

[0014] The present invention provides a method for manufacturing a wear-resistant composite piercing machine mandrel and the piercing machine mandrel itself, which have the following technical advantages:

[0015] 1. The wear-resistant composite piercing machine mandrel manufacturing method of this application has a mandrel body with high strength and good toughness, wherein the tensile strength is greater than 1500MPa, the elongation is greater than 28%, and the reduction of area is greater than 35%, which can effectively ensure that the mandrel will not crack or deform during use;

[0016] 2. The wear-resistant composite piercing machine mandrel manufacturing method of this application has a dense submerged arc welded cladding layer with good metallurgical bonding to the steel base mandrel. The cladding layer is free of inclusions and cracks, and has high hardness at high temperatures, with a hardness greater than 50 HRC at 600℃; 3. The wear-resistant composite piercing machine mandrel manufacturing method of this application has a dense and uniform oxide film on the surface of the cladding layer. The oxide film is firmly bonded to the cladding layer. The presence of the dense and uniform oxide film can reduce the power consumption of the steel pipe piercing machine and improve the service life of the piercing machine mandrel;

[0017] 4. The wear-resistant composite piercing machine mandrel manufacturing method of this application results in a mandrel with a service life significantly longer than that of alloy tool steel and alloy structural steel mandrels. On a Φ100 unit, the original mandrel life was less than 250 pieces (steel pipes) / mandrel, while the composite piercing machine mandrel of this invention has a lifespan of 850-930 pieces (steel pipes) / mandrel. Using the mandrel of this invention can improve the piercing machine's operating rate, reduce the labor intensity of workers, and lower the production cost of steel pipes. Its widespread application has significant economic and social benefits.

[0018] Other features and advantages of the invention will become clear when reading the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In these drawings, similar reference numerals are used to denote similar elements. The drawings described below are some embodiments of the invention, but not all embodiments. Other drawings will be readily available to those skilled in the art based on these drawings without any inventive effort.

[0020] Figure 1 An exemplary structural diagram of the wear-resistant composite perforating machine mandrel of the present invention is shown;

[0021] In the diagram: 1. Steel base top; 2. Cladding layer. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0023] The following describes in detail, with reference to the accompanying drawings and embodiments, the manufacturing method of the wear-resistant composite piercing machine mandrel and the piercing machine mandrel.

[0024] A method for manufacturing a wear-resistant composite piercing machine mandrel includes:

[0025] Step S1: Prepare the steel-based mandrel; Step S2: Apply submerged arc welding to the working cone surface and nose end face of the steel-based mandrel to achieve the desired shape. flux-cored welding wire A cladding layer with a thickness of 6-8mm is formed on the working cone surface and nose end face of the steel base mandrel; in step S3, the cladding layer of the steel base mandrel is pre-oxidized at high temperature to obtain a wear-resistant composite piercing machine mandrel.

[0026] Specifically, step S1, preparing the steel-based mandrel, includes: melting the steel-based mandrel material and casting it into a mandrel blank using a lost foam casting method, followed by rough machining and heat treatment to obtain the steel-based mandrel; wherein the casting temperature of the lost foam casting method is 1544-1559℃; wherein the chemical composition of the mandrel blank includes: 0.19-0.25% C, 1.88-2.13% Cr, 1.03-1.26% Si, 4.12-4.30% Mn, 0.37-0.48% Ta, 1.36-1.49% Nb, 0.11-0.15% Ca, 0.14-0.18% K, 0.00-0.020% S, 0.00-0.025% P, with the balance being Fe.

[0027] Specifically, the heat treatment includes: heating the mandrel blank to 980-1000℃ in the furnace, holding it at that temperature for 60-80 minutes, then furnace cooling it to 880-895℃, holding it at that temperature for 90-120 minutes, then oil quenching it in quenching oil at 20-35℃ for 15-20 minutes, and finally air cooling it to room temperature.

[0028] Specifically, in step S2: flux-cored welding wireDiameter 2.0-2.5 mm; Chemical composition of cladding layer includes: 0.67-0.75% C, 3.12-3.28% B, 18.04-18.31% Al, 33.51-33.77% Cr, 6.23-6.38% Co, 8.62-8.80% Mo, 3.73-3.91% Nb, 0.27-0.35% Y, 15.64-15.83% Ni, 0.00-0.022% S, 0.00-0.025% P, balance Fe.

[0029] Specifically, step S3, high-temperature pre-oxidation, includes: heating the mandrel to 880-895°C in a heat treatment furnace, introducing steam into the furnace at a rate of 120-150 ml / min, and holding it at that temperature for 90-120 minutes. Then, stopping the steam supply and cooling the mandrel to 750-780°C in the furnace for 60-80 minutes, followed by air cooling to room temperature after the furnace has cooled to below 150°C, thus obtaining the wear-resistant composite piercing machine mandrel.

[0030] A wear-resistant composite piercing machine mandrel includes a steel base mandrel and a cladding layer, wherein the cladding layer is clad on the working cone surface and the nose end face of the steel base mandrel.

[0031] Example 1:

[0032] A wear-resistant composite piercing machine mandrel and its manufacturing method are disclosed. First, a steel-based mandrel material is melted in a medium-frequency induction furnace and cast into a mandrel blank. Then, rough machining and heat treatment are performed to obtain the steel-based mandrel 1. Finally, MZ-1-1000 welding agent, combined with flux TF-81, is used on the working cone surface and nose end face of the steel-based mandrel 1 to... flux-cored welding wire A cladding layer 2 with a thickness of 6.0-6.3 mm is obtained by multi-layer, multi-pass welding on the working cone surface and nose end face of the mandrel. The mandrel is then precision machined to the specified dimensions and precision. Finally, the cladding layer 2 is pre-oxidized at high temperature to obtain the wear-resistant composite piercing machine mandrel. The specific process steps are as follows:

[0033] ① First, steel-based mandrel material is smelted in a medium-frequency induction furnace and cast into mandrel blanks using the lost foam casting method. The pouring temperature of the molten steel is 1544℃. The chemical composition and mass fraction of the mandrel blank are: 0.19% C, 2.13% Cr, 1.03% Si, 4.30% Mn, 0.37% Ta, 1.49% Nb, 0.11% Ca, 0.18% K, 0.017% S, 0.023% P, with the balance being Fe and unavoidable impurities. After sand removal, grinding, and rough machining, the mandrel blank is heated to 980℃ in the furnace and held for 80 minutes. Then, it is furnace cooled to 880℃ and held for 120 minutes. Finally, it is oil-quenched in quenching oil at 20℃ for 15 minutes and then air-cooled to room temperature to obtain steel-based mandrel 1.

[0034] ② Apply MZ-1-1000 welding agent and TF-81 flux to the working cone surface and nose end face of the steel-based mandrel 1 obtained in step ①. flux-cored welding wire The cladding layer 2 with a thickness of 6.0-6.3mm is obtained by multi-layer and multi-pass welding on the working cone surface and nose end face of the mandrel, and the mandrel is then precision machined to the specified dimensions and precision. flux-cored welding wire The chemical composition and mass fraction of the cladding layer 2 with a diameter of 2.0 mm are: 0.67% C, 3.28% B, 18.04% Al, 33.77% Cr, 6.23% Co, 8.80% Mo, 3.73% Nb, 0.35% Y, 15.64% Ni, 0.020% S, 0.021% P, with the balance being Fe and unavoidable impurities; ③ The mandrel after finishing in step ② is heated to 880℃ in a heat treatment furnace, and steam is introduced into the furnace at a rate of 120 ml / min, and held at this temperature for 120 minutes. Then, the steam is stopped, and the mandrel is cooled to 750℃ in the furnace and held for 80 minutes. After the furnace cools to below 150℃, the mandrel is removed from the furnace and air-cooled to room temperature to obtain the wear-resistant composite piercing machine mandrel. The mechanical properties of the composite mandrel are shown in Table 1.

[0035] Example 2:

[0036] A wear-resistant composite piercing machine mandrel and its manufacturing method are disclosed. First, a steel-based mandrel material is melted in a medium-frequency induction furnace and cast into a mandrel blank. Then, rough machining and heat treatment are performed to obtain the steel-based mandrel 1. Finally, MZ-1-1000 welding agent, combined with flux TF-81, is used on the working cone surface and nose end face of the steel-based mandrel 1 to... flux-cored welding wire A cladding layer 2 with a thickness of 7.8-8.0 mm is obtained by multi-layer, multi-pass welding on the working cone surface and nose end face of the mandrel. The mandrel is then precision machined to the specified dimensions and precision. Finally, the cladding layer 2 is pre-oxidized at high temperature to obtain the wear-resistant composite piercing machine mandrel. The specific process steps are as follows:

[0037] First, steel-based mandrel material was smelted in a medium-frequency induction furnace and cast into mandrel blanks using the lost foam casting method. The pouring temperature of the molten steel was 1559℃. The chemical composition and mass fraction of the mandrel blank were: 0.25% C, 1.88% Cr, 1.26% Si, 4.12% Mn, 0.48% Ta, 1.36% Nb, 0.15% Ca, 0.14% K, 0.010% S, 0.024% P, with the balance being Fe and unavoidable impurities. After sand removal, grinding, and rough machining, the mandrel blank was heated to 1000℃ in the furnace and held for 60 minutes. Then, it was furnace cooled to 895℃ and held for 90 minutes. Finally, it was oil-quenched in quenching oil at 35℃ for 20 minutes and then air-cooled to room temperature to obtain steel-based mandrel 1.

[0038] On the working cone surface and nose end face of the steel-based mandrel 1, MZ-1-1000 is used, along with flux TF-81, to make... Core welding wire The cladding layer 2 with a thickness of 7.8-8.0 mm is obtained by multi-layer and multi-pass welding on the working cone surface and nose end face of the mandrel, and the mandrel is then precision machined to the specified dimensions and precision. flux-cored welding wire The chemical composition and mass fraction of the cladding layer 2 with a diameter of 2.5 mm are: 0.75% C, 3.12% B, 18.31% Al, 33.51% Cr, 6.38% Co, 8.62% Mo, 3.91% Nb, 0.27% Y, 15.83% Ni, 0.017% S, 0.020% P, balance Fe and unavoidable impurities;

[0039] After finishing, the mandrel is heated to 895℃ in a heat treatment furnace. Steam is then introduced into the furnace at a rate of 150 ml / min and held for 90 minutes. Steam is then stopped, and the mandrel is cooled to 780℃ and held for 60 minutes. After the furnace cools to below 150℃, the mandrel is removed and air-cooled to room temperature to obtain a wear-resistant composite piercing machine mandrel. The mechanical properties of the composite mandrel are shown in Table 1.

[0040] Example 3:

[0041] A wear-resistant composite piercing machine mandrel and its manufacturing method are disclosed. First, a steel-based mandrel material is melted in a medium-frequency induction furnace and cast into a mandrel blank. Then, rough machining and heat treatment are performed to obtain the steel-based mandrel 1. Finally, MZ-1-1000 welding agent, combined with flux TF-81, is used on the working cone surface and nose end face of the steel-based mandrel 1 to... flux-cored welding wire A cladding layer 2 with a thickness of 6.9-7.2 mm is obtained by multi-layer, multi-pass welding on the working cone surface and nose end face of the mandrel. The mandrel is then precision machined to the specified dimensions and precision. Finally, the cladding layer 2 is pre-oxidized at high temperature to obtain the wear-resistant composite piercing machine mandrel. The specific process steps are as follows:

[0042] First, steel-based mandrel material was smelted in a medium-frequency induction furnace and cast into mandrel blanks using the lost foam casting method. The pouring temperature of the molten steel was 1548℃. The chemical composition and mass fraction of the mandrel blank were: 0.21% C, 1.94% Cr, 1.18% Si, 4.25% Mn, 0.39% Ta, 1.38% Nb, 0.14% Ca, 0.17% K, 0.009% S, 0.017% P, with the balance being Fe and unavoidable impurities. After sand removal, grinding, and rough machining, the mandrel blank was heated to 990℃ in the furnace and held for 70 minutes. Then, it was furnace cooled to 890℃ and held for 100 minutes. Finally, it was oil-quenched in quenching oil at 28℃ for 17 minutes and then air-cooled to room temperature to obtain steel-based mandrel 1.

[0043] The steel-based mandrel uses MZ-1-1000 welding agent and TF-81 flux on its working conical surface and nose end face. Core welding wire The cladding layer 2 with a thickness of 6.9-7.2mm is obtained by multi-layer and multi-pass welding on the working cone surface and nose end face of the mandrel, and the mandrel is then precision machined to the specified dimensions and precision. flux-cored welding wire The chemical composition and mass fraction of the cladding layer 2 with a diameter of 2.5 mm are: 0.71% C, 3.19% B, 18.25% Al, 33.60% Cr, 6.32% Co, 8.73% Mo, 3.78% Nb, 0.29% Y, 15.78% Ni, 0.016% S, 0.023% P, balance Fe and unavoidable impurities;

[0044] After finishing, the mandrel is heated to 890℃ in a heat treatment furnace. Steam is then introduced into the furnace at a rate of 130 ml / min and held for 110 minutes. Steam is then stopped, and the mandrel is cooled to 760℃ and held for 70 minutes. After the furnace cools to below 150℃, the mandrel is removed and air-cooled to room temperature to obtain a wear-resistant composite piercing machine mandrel. The mechanical properties of the composite mandrel are shown in Table 1.

[0045] Table 1 Mechanical properties of the composite mandrel

[0046]

[0047] From Table 1, we can see that:

[0048] The steel-based mandrel of this invention features high strength and good ductility, with a tensile strength greater than 1500 MPa, elongation greater than 28%, and reduction of area greater than 35%, ensuring that the mandrel will not crack or deform during use. The submerged arc welding cladding layer of this invention has a dense structure and a good metallurgical bond with the steel-based mandrel. The cladding layer is free of inclusions and cracks, and has high hardness at high temperatures, exceeding 50 HRC at 600℃. The surface of the cladding layer has a dense and uniform oxide film, which is firmly bonded to the cladding layer. The presence of this dense and uniform oxide film reduces the power consumption of the steel pipe piercing machine and increases the service life of the piercing machine mandrel. The service life of the mandrel of this invention is significantly longer than that of alloy tool steel and alloy structural steel mandrels. On a Φ100 unit, the original mandrel life was less than 250 pipes / mandrel, while the service life of the composite piercing machine mandrel of this invention is 850-930 pipes / mandrel. Using the mandrel of this invention can improve the working efficiency of piercing machines, reduce the labor intensity of workers, and lower the production cost of steel pipes. Its widespread application has good economic and social benefits.

[0049] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or apparatus comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the article or apparatus that includes that element.

[0050] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. The present invention has been described in detail with reference to preferred embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for manufacturing a wear-resistant composite piercing machine mandrel, characterized in that, include: Step S1: Prepare the steel-based mandrel; Step S2 involves using submerged arc welding on the working conical surface and nose end face of the steel base head to clad the flux-cored wire onto the working conical surface and nose end face of the steel base head, forming a cladding layer with a thickness of 6-8 mm. The diameter of the flux-cored welding wire is 2.0-2.5 mm; The chemical composition of the cladding layer by mass percentage is: 0.67-0.75% C, 3.12-3.28% B, 18.04-18.31% Al, 33.51-33.77% Cr, 6.23-6.38% Co, 8.62-8.80% Mo, 3.73-3.91% Nb, 0.27-0.35% Y, 15.64-15.83% Ni, 0.00-0.022% S, 0.00-0.025% P, balance Fe; Step S3 involves high-temperature pre-oxidation treatment of the cladding layer of the steel-based mandrel to obtain a wear-resistant composite piercing machine mandrel.

2. The method for manufacturing the wear-resistant composite perforating machine mandrel according to claim 1, characterized in that, The step S1 of preparing the steel-based mandrel includes: The steel-based mandrel material is melted and cast into a mandrel blank using the lost foam casting method. Then, it is rough-machined and heat-treated to obtain the steel-based mandrel. Among them, the pouring temperature for the lost foam casting method is 1544-1559℃; The chemical composition of the mandrel blank, by mass percentage, is as follows: 0.19-0.25% C, 1.88-2.13% Cr, 1.03-1.26% Si, 4.12-4.30% Mn, 0.37-0.48% Ta, 1.36-1.49% Nb, 0.11-0.15% Ca, 0.14-0.18% K, 0.00-0.020% S, 0.00-0.025% P, with the balance being Fe.

3. The method for manufacturing the wear-resistant composite perforating machine mandrel according to claim 2, characterized in that, The heat treatment includes: The mandrel blank is heated in the furnace to 980-1000℃, held for 60-80 minutes, then furnace cooled to 880-895℃, held for 90-120 minutes, then oil-quenched in quenching oil at 20-35℃ for 15-20 minutes, and then air-cooled to room temperature.

4. The method for manufacturing the wear-resistant composite perforating machine mandrel according to claim 1, characterized in that, The high-temperature pre-oxidation treatment in step S3 includes: The mandrel with the cladding layer is heated to 880-895℃ in a heat treatment furnace. Water vapor is introduced into the furnace at a rate of 120-150 ml / min and held at that temperature for 90-120 minutes. Then, the water vapor is stopped and the mandrel is cooled to 750-780℃ in the furnace and held for 60-80 minutes. After the furnace is cooled to below 150℃, the mandrel is removed from the furnace and air-cooled to room temperature to obtain the wear-resistant composite piercing machine mandrel.

5. A wear-resistant composite piercing machine mandrel, characterized in that, It includes a steel-based mandrel and a cladding layer, wherein the piercing machine mandrel is prepared by the wear-resistant composite piercing machine mandrel manufacturing method according to any one of claims 1-4.

Images