Ejector head for extrusion forming of seamless steel pipe

Abstract

The utility model relates to the field of forming tools for metal extrusion, in particular to an ejector head for extrusion forming of a seamless steel pipe. The top for extrusion forming of the seamless steel pipe comprises a top body (1) and is characterized in that the top body (1) comprises a top tip (2), a top body (3) and a top tail (4), the outer side face of the top body (3) is sequentially provided with at least three annular heat dissipation grooves (31), the outer side face of the top body (1) is covered with an oxidation layer (32), the oxidation layer (32) fills all the heat dissipation grooves (31), and the outer side face of the oxidation layer (32) forms a smooth face. The utility model has the advantages of convenient manufacture and long service life.

Description

Technical Field

[0001] The utility model relates to the field of forming tools for metal extrusion, in particular to a plug used for extrusion forming of seamless steel pipes. Background Art

[0002] Currently, seamless steel pipes are mostly produced using an extrusion process, where a punch is used to form a hole at one end of the billet. This extrusion process requires the punch to withstand extremely high pressure and heat. Iron-based, high-tungsten, cobalt-containing alloy steel, a commonly used structural alloy, is used in seamless steel pipe production due to its excellent high-temperature mechanical properties. However, in the extreme operating environments of high temperature, heavy loads, and high friction encountered during seamless steel pipe processing, the wear resistance and heat resistance of iron-based, high-tungsten, cobalt-containing alloy steel remain unsuitable for seamless pipe processing.

[0003] Currently, one process involves etching threads on the plug surface and then creating an oxide film within the threads through heat treatment to improve the surface's heat resistance. However, during this traditional heat treatment process, carbon and oxygen combine, causing surface decarburization. Furthermore, the oxide film formed between the threads is insufficient, reducing the bond strength between the oxide film and the substrate. This limits the service life and affects the overall performance of the final product. Utility Model Content

[0004] In order to overcome the defects of the prior art and provide a metal extrusion molding tool which is easy to manufacture, has a long service life and improves production efficiency, the utility model discloses a plug for extrusion molding of seamless steel pipes.

[0005] The utility model achieves the purpose of the invention through the following technical solutions:

[0006] A plug for seamless steel pipe extrusion molding, comprising a plug body, characterized by:

[0007] The main body of the plug includes a tip, a body and a tail. The tip is spherical and the tail is cylindrical. The diameter of the bottom surface of the tip is smaller than the diameter of the top surface of the tail. The top surface of the body is connected to the bottom surface of the tip, and the bottom surface of the body is connected to the top surface of the tail. The outer side surfaces of the body and the tip, and the outer side surfaces of the body and the tail are all smoothly connected.

[0008] There are at least three annular heat dissipation grooves on the outer surface of the top body.

[0009] The outer surface of the plug body is covered with an oxide layer, and the oxide layer fills up the heat dissipation grooves, so that the outer side surface of the oxide layer forms a smooth surface.

[0010] The plug for seamless steel pipe extrusion molding is characterized by:

[0011] The outer side of the top body is divided into three areas, namely the front side, the middle side and the rear side, from the top to the bottom of the top body. At least two heat dissipation slots are provided in each of the three areas.

[0012] The depths of the heat dissipation slots on the front side of the top body are equal. When the number of heat dissipation slots is not less than three, the spacing between two adjacent heat dissipation slots is equal.

[0013] The depth of each heat dissipation groove provided on the middle side of the top body is determined as follows: the depth decreases from the top surface to the bottom surface of the top body, and the maximum value is less than the depth of the heat dissipation groove provided on the front side of the top body. When the number of heat dissipation grooves is not less than three, the spacing between two adjacent heat dissipation grooves is equal;

[0014] The depth of each heat dissipation groove provided on the rear side of the top body is determined as follows: it decreases in sequence from the top surface to the bottom surface of the top body, and the maximum value is less than the minimum value of the depth of the heat dissipation groove provided on the middle side of the top body. When the number of heat dissipation grooves is not less than three, the spacing between two adjacent heat dissipation grooves is equal.

[0015] The plug for seamless steel pipe extrusion molding is characterized in that the generatrix of the outer side surface of the plug body is selected from any one of an outwardly convex elliptical arc, a parabola, a branch of a hyperbola, a cycloid and a circular involute.

[0016] The plug for seamless steel pipe extrusion molding is characterized in that the plug body is made of iron-based high-tungsten cobalt alloy steel, wherein the mass percentages of various elements are: carbon content 0.2% to 0.4%, tungsten content 1% to 6%, cobalt content 0.1% to 2%, and the balance is iron.

[0017] The manufacturing method of the plug for seamless steel pipe extrusion molding is implemented after preparing a workpiece, wherein the workpiece includes a plug body, the plug body including a tip, a top body and a top tail, the tip is spherical, the top tail is cylindrical, the diameter of the bottom surface of the tip is smaller than the diameter of the top surface of the top tail, the top surface of the top body is connected to the bottom surface of the tip, and the bottom surface of the top body is connected to the top surface of the top tail, the outer side surfaces of the top body and the tip, and the outer side surfaces of the top body and the top tail are all smoothly transitioned, and at least three annular heat dissipation grooves are sequentially provided on the outer side surface of the top body. The method is characterized by: implementing the method in sequence according to the following steps:

[0018] a. Preprocessing:

[0019] Ultrasonic cleaning and chemical degreasing are used to thoroughly clean the workpiece surface to ensure that there is no oil stain and oxide scale on the workpiece surface. The workpiece is then dried to avoid the formation of water rust and to create good conditions for subsequent heat treatment.

[0020] b. Precision carburizing:

[0021] Place the workpiece in the gas carburizing furnace and implement temperature control, time and depth control, and atmosphere control:

[0022] b.1 Temperature control:

[0023] Gas carburizing treatment is carried out between 900℃ and 960℃, and methanol and kerosene are dripped into the furnace to make the atmosphere contain a proper proportion of CO, CH4 and H2 mixed gas to ensure that carbon atoms are effectively and evenly diffused.

[0024] b.2 Time and depth control: According to the required carburizing layer depth, the time is controlled within 4 hours to 36 hours to ensure uniform depth;

[0025] b.3 Atmosphere control: Implement low-oxygen carburizing to reduce the growth rate of the oxide film, improve the carburizing efficiency, surface oxide film thickness and density;

[0026] c. Precision oxidation:

[0027] Continue to implement temperature control, time and depth control, and atmosphere control:

[0028] c.1 Temperature control: The temperature is raised to 900°C to 1050°C for oxidation treatment, and an ethanol solution is dripped in. The ethanol solution is prepared by mixing ethanol and distilled water, and the mass ratio of ethanol to distilled water is 1:3 to 1:5. The atmosphere in the furnace is in a weak oxidizing atmosphere. The atmosphere in the furnace contains a mixed gas of CO, CO2 and H2 in an appropriate proportion, and is in a weak oxidizing atmosphere. Ensure that a dense oxide layer (32) of sufficient thickness is generated on the outer side of the plug body (1).

[0029] c.2 Time and depth control: According to the required thickness of the oxide layer (32), the oxidation time is 3 hours to 10 hours, ensuring that the heat dissipation groove (31) is filled with the oxide layer (32) and the oxide layer (32) on the outer side of the plug body (1) is dense.

[0030] c.3 Atmosphere control: Implement a weak oxidizing atmosphere to reduce the growth rate of the oxide layer and increase the thickness and density of the oxide layer;

[0031] d. Cooling:

[0032] After cooling to 800°C, the workpiece is lifted out of the gas carburizing furnace and cooled to room temperature in air;

[0033] e. Performance optimization and testing: Through metallographic analysis, hardness testing, and wear testing, we verify the structure, hardness distribution, and wear resistance of the carburized layer, as well as the fill rate of the oxide layer in the heat sink, to ensure the expected performance improvement.

[0034] The utility model has the following beneficial effects:

[0035] 1. Significantly improve wear resistance: The carbon content of the workpiece surface is increased, which avoids decarburization and softening of the structure, improves the hardness and wear resistance of the material surface, and extends the service life.

[0036] 2. Enhanced heat resistance: The carbon content of the surface metal is greatly increased, reducing thermal conductivity. The gaps between the threads are filled with an oxide film generated by heat treatment, ensuring the material's stability and strength at high temperatures while also preventing scratches on other contact materials.

[0037] 3. Comprehensive performance optimization: maintain core toughness to avoid brittle fracture; maintain surface wear resistance and high temperature resistance to ensure balanced overall mechanical properties.

[0038] 4. Process controllability: Precise process parameter control improves the repeatability of carburizing and oxidation treatments and the consistency of product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a structural diagram of the present utility model. DETAILED DESCRIPTION

[0040] The present invention is further described below through specific embodiments. Example

[0041] A plug for seamless steel pipe extrusion molding, comprising a plug body 1, such as Figure 1 As shown, the specific structure is:

[0042] The plug body 1 includes a tip 2, a body 3 and a tail 4. The tip 2 is spherical, and the tail 4 is cylindrical. The diameter of the bottom surface of the tip 2 is smaller than the diameter of the top surface of the tail 4. The top surface of the body 3 is connected to the bottom surface of the tip 2, and the bottom surface of the body 3 is connected to the top surface of the tail 4. The outer side surfaces of the body 3 and the tip 2, and the outer side surfaces of the body 3 and the tail 4 are all smoothly transitioned.

[0043] At least three annular heat dissipation grooves 31 are sequentially provided on the outer surface of the top body 3.

[0044] The outer surface of the plug body 1 is covered with an oxide layer 32 , and the oxide layer 32 fills up the heat dissipation grooves 31 , so that the outer side surface of the oxide layer 32 forms a smooth surface.

[0045] In this embodiment:

[0046] The outer side surface of the top body 3 is divided into three areas, namely, the front side surface, the middle side surface and the rear side surface, from the top surface of the top body 3 to the bottom surface. At least three heat dissipation slots 31 are respectively provided in the front side surface, the middle side surface and the rear side surface of the top body 3.

[0047] The depths of the heat dissipation grooves 31 on the front side of the top body 3 are equal, and the distances between two adjacent heat dissipation grooves 31 are equal;

[0048] The depth of each heat dissipation groove 31 provided on the middle side of the top body 3 is determined as follows: the depth decreases from the top surface to the bottom surface of the top body 3, the maximum value is less than the depth of the heat dissipation groove 31 provided on the front side of the top body 3, and the spacing between two adjacent heat dissipation grooves 31 is equal;

[0049] The depth of each heat dissipation groove 31 provided on the rear side surface of the top body 3 is determined as follows: the depth decreases in sequence from the top surface to the bottom surface of the top body 3, the maximum value is less than the minimum value of the depth of the heat dissipation groove 31 provided on the middle side surface of the top body 3, and the spacing between two adjacent heat dissipation grooves 31 is equal.

[0050] The generatrix of the outer side surface of the top body 3 of the plug body 1 is selected from any one of an outwardly convex elliptical arc, a parabola, a branch of a hyperbola, a cycloid and an involute of a circle. In this embodiment, a parabola is selected.

[0051] In this embodiment, the plug body 1 is made of iron-based high-tungsten cobalt alloy steel, wherein the mass percentages of various elements are: carbon content 0.2% to 0.4%, tungsten content 1% to 6%, cobalt content 0.1% to 2%, and the balance is iron.

[0052] When manufacturing this embodiment, the following steps are carried out in sequence:

[0053] a. Preparation of workpiece: the workpiece as Figure 1 As shown: it includes a plug body 1, which includes a top 2, a top body 3 and a top tail 4. The top 2 is spherical, and the top tail 4 is cylindrical. The diameter of the bottom surface of the top 2 is smaller than the diameter of the top surface of the top tail 4. The top surface of the top body 3 is connected to the bottom surface of the top 2, and the bottom surface of the top body 3 is connected to the top surface of the top tail 4. The outer side surfaces of the top body 3 and the top 2, and the outer side surfaces of the top body 3 and the top tail 4 are all smoothly transitioned. At least three annular heat dissipation grooves 31 are sequentially provided on the outer surface of the top body 3.

[0054] b. Preprocessing:

[0055] Ultrasonic cleaning and chemical degreasing are used to thoroughly clean the surface of the workpiece to ensure that there is no oil stain and oxide scale on the surface of the workpiece. The workpiece is then dried to avoid the formation of water rust and create good conditions for subsequent heat treatment.

[0056] c. Precision carburizing:

[0057] Place the workpiece in the gas carburizing furnace and implement temperature control, time and depth control, and atmosphere control:

[0058] c.1 Temperature control:

[0059] Carry out gas carburizing treatment between 900°C and 960°C. In this embodiment, the temperature is 950°C. Methanol and kerosene are added dropwise to make the furnace atmosphere contain a mixture of CO, CH4 and H2 in appropriate proportions. The carburizing atmosphere is mainly composed of methane to ensure that carbon atoms are effectively and evenly diffused.

[0060] c.2 Time and depth control: Depending on the desired carburized layer depth, the time is controlled between 4 hours and 36 hours. In this embodiment, 24 hours is used to ensure uniform depth and carbon concentration of 0.5% to 1.2%;

[0061] c.3 Atmosphere control: Implement low-oxygen carburizing to reduce the growth rate of the oxide film, improve the carburizing efficiency, surface oxide film thickness and density.

[0062] d. Precision oxidation:

[0063] Continue to implement temperature control, time and depth control, and atmosphere control:

[0064] d.1 Temperature Control: The temperature is raised to between 900°C and 1050°C for oxidation treatment. In this embodiment, the temperature is 950°C. An ethanol solution is added dropwise. The ethanol solution is prepared by mixing ethanol and distilled water in a mass ratio of 1:4. The furnace atmosphere contains a mixture of CO, CO2, and H2 in an appropriate proportion, creating a weakly oxidizing atmosphere. This ensures that a dense oxide layer 32 of sufficient thickness is formed on the outer surface of the plug body 1.

[0065] d.2 Time and depth control: Depending on the desired thickness of the oxide layer 32, the oxidation time is 3 hours to 10 hours. In this embodiment, 5 hours is used to ensure that the heat dissipation groove 31 is fully filled with the oxide layer 32 and the oxide layer 32 on the outer surface of the plug body 1 is dense.

[0066] d.3 Atmosphere control: Implement a weak oxidizing atmosphere to reduce the growth rate of the oxide layer 32 and increase the thickness and density of the oxide layer 32;

[0067] e. Cooling:

[0068] After cooling to 800°C, the workpiece is lifted out of the gas carburizing furnace and cooled to room temperature in air;

[0069] f. Performance Optimization and Testing: Through metallographic analysis, hardness testing, and wear testing, we verify the structure, hardness distribution, and wear resistance of the carburized layer, as well as the filling rate of the oxide film between the thread teeth, to ensure the expected performance improvement.

Claims

1. A plug for seamless steel pipe extrusion molding, comprising a plug body (1), characterized in that: The main body (1) of the mandrel comprises a top (2), a top body (3) and a top tail (4); the top (2) is in a spherical segment shape, the top tail (4) is in a cylindrical shape, the diameter of the bottom surface of the top (2) is smaller than the diameter of the top surface of the top tail (4), the top surface of the top body (3) is connected to the bottom surface of the top (2), the bottom surface of the top body (3) is connected to the top surface of the top tail (4), and the outer side surfaces of the top body (3) and the top (2), and the outer side surfaces of the top body (3) and the top tail (4) are all smoothly transitionally connected; At least three annular heat dissipation grooves (31) are sequentially provided on the outer surface of the top body (3). The outer surface of the mandrel body (1) is covered with an oxide layer (32), and the oxide layer (32) fills each heat dissipation groove (31), so that the outer side surface of the oxide layer (32) forms a smooth surface; The outer side surface of the top body (3) is divided into three regions, namely, a front side surface, a middle side surface and a rear side surface, in order from the top surface to the bottom surface of the top body (3). At least two heat dissipation grooves (31) are respectively provided in the three regions, namely, the front side surface, the middle side surface and the rear side surface of the top body (3). The depths of the heat dissipation grooves (31) provided on the front side of the top body (3) are all equal. When the number of the heat dissipation grooves (31) is not less than three, the spacing between two adjacent heat dissipation grooves (31) is all equal. The depth of each heat dissipation groove (31) provided on the middle side surface of the top body (3) is determined as follows: the depth decreases in sequence from the top surface to the bottom surface of the top body (3), and the maximum value is less than the depth of the heat dissipation groove (31) provided on the front side surface of the top body (3); when the number of the heat dissipation grooves (31) is not less than three, the spacing between two adjacent heat dissipation grooves (31) is equal; The depth of each heat dissipation groove (31) provided on the rear side surface of the top body (3) is determined as follows: the depth decreases in sequence from the top surface to the bottom surface of the top body (3), and the maximum value is less than the minimum value of the depth of the heat dissipation groove (31) provided on the middle side surface of the top body (3). When the number of the heat dissipation grooves (31) is not less than three, the spacing between two adjacent heat dissipation grooves (31) is equal.

2. The plug for seamless steel pipe extrusion molding according to claim 1, characterized in that: The generatrix of the outer side surface of the top body (3) of the mandrel body (1) is selected from any one of an outwardly convex elliptical arc, a parabola, a branch of a hyperbola, a cycloid and a circular involute.

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