Extrusion method of soluble magnesium alloy material hollow rod

Abstract

The invention belongs to the technical field of oil and gas exploitation, and discloses an extrusion method of a soluble magnesium alloy material hollow rod, and the extrusion method of the soluble magnesium alloy material hollow rod comprises the following steps: preparing raw materials; preparing extrusion equipment and a mold; controlling extrusion process parameters; through precise control of the component proportion of the soluble magnesium alloy, the problem of unstable performance caused by component fluctuation in a traditional process is solved, the alloy has excellent dissolvability and mechanical strength at the same time, and meanwhile, the design of a plane shunt combination die is matched with strict temperature, speed and pressure control, so that the mechanical strength of the alloy is greatly improved. According to the method, the defects of common cracks, wrinkles and the like in the extrusion process are effectively avoided, the uniformity error of the wall thickness of the hollow rod is controlled within + / -0.1 mm, the surface roughness is reduced to Ra0.8-1.6 microns, the size precision is within + / -0.2 mm, and the stability and the reliability of the product quality are improved.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas extraction technology, specifically a method for extruding hollow rods made of soluble magnesium alloy material. Background Technology

[0002] In modern industry, especially in high-end fields such as oil and gas extraction, aerospace, and biomedicine, increasingly stringent requirements are being placed on the functionality and environmental adaptability of materials. Soluble magnesium alloys, with their unique combination of properties, have become a research hotspot in recent years. These materials use magnesium as a matrix and adjust their properties by adding alloying elements such as aluminum, zinc, and calcium. They not only possess low density and high specific strength, but also exhibit controlled dissolution in specific media (such as aqueous solutions containing chloride ions), achieving natural degradation without additional recycling processes. This significantly reduces the complexity of engineering operations and the environmental burden.

[0003] In the oil and gas extraction industry, the application prospects of soluble magnesium alloy hollow rods are particularly significant. For example, in horizontal well fracturing operations, soluble magnesium alloy hollow rods can serve as core structural components for temporary tools such as bridge plugs and temporary plugging agent carriers. After the fracturing task is completed, they can gradually dissolve in the wellbore fluid, avoiding the cumbersome process of drilling and milling to retrieve traditional metal tools, significantly shortening the operation cycle and reducing safety risks such as stuck pipe. However, compared with traditional magnesium alloys, soluble magnesium alloys have a more complex composition design to achieve controllable dissolution characteristics, and usually contain a higher proportion of easily corrosive elements (such as calcium), which leads to a significant decrease in their hot working properties. During extrusion molding, the material is prone to defects such as cracks and tears due to insufficient plasticity. In particular, the molding of hollow structures requires precise control of metal flow and welding, making it extremely sensitive to process parameters.

[0004] In existing technologies, extrusion methods for hollow magnesium alloy bars are mostly based on traditional magnesium alloys and do not fully consider the unique composition of soluble magnesium alloys. For example, traditional processes often use lower extrusion temperatures to ensure alloy strength, but for soluble magnesium alloys, excessively low temperatures can lead to insufficient material plasticity and increase the risk of cracking; while simply increasing the temperature may cause excessive diffusion of alloying elements, compromising the stability of the material's solubility. Furthermore, existing die structures are mostly modified from simple solid bar extrusion dies, making it difficult to achieve uniform flow of soluble magnesium alloys during hollow forming, easily leading to quality problems such as wall thickness deviations and internal wall wrinkles.

[0005] Furthermore, due to the presence of easily oxidized alloying elements in its composition, oxide scale easily forms on the surface during high-temperature extrusion. Traditional lubrication methods are also unable to form a stable isolation film at high temperatures, leading to frequent adhesion between the metal and the mold, which further deteriorates the surface finish of the product. These problems not only affect the mechanical properties and dimensional accuracy of the product, but also disrupt the consistency of its dissolution behavior, thus restricting the large-scale application of soluble magnesium alloy hollow rods in high-end fields. Summary of the Invention

[0006] The purpose of this invention is to provide a method for extruding hollow rods of soluble magnesium alloy material to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for extruding hollow rods of soluble magnesium alloy material, the method comprising the following steps: S1. Raw material preparation: Select soluble magnesium alloy billets with specific composition ratios, melt them into ingots, and then perform homogenization treatment and machining. S2. Extrusion equipment and die preparation: A horizontal reverse extrusion press is selected, and a specially designed planar diversion combination die is adopted. The die is made of hot work die steel and is treated accordingly. S3. Extrusion process parameter control: Temperature control of billet, extrusion cylinder and die, setting appropriate extrusion speed and extrusion pressure and lubrication treatment; S4. Post-extrusion treatment: The extruded hollow bars are cooled, straightened and surface treated in sequence.

[0008] Preferably, the composition ratio of the soluble magnesium alloy billet in the raw material preparation is as follows: magnesium accounts for 85%-94%, and the purity needs to reach 99.95% or higher; aluminum accounts for 3%-8%; zinc accounts for 1%-4%; calcium accounts for 0.2%-1.5%; a small amount of manganese can also be added according to actual needs, with an addition ratio not exceeding 0.5%; rare earth elements are a mixture of Ce and Nd, of which Ce accounts for 0.4%-0.6% and Nd accounts for 0.2%-0.4%, with a total ratio ≤1%.

[0009] Preferably, the smelting process in the raw material preparation involves melting each raw material in proportion under argon protection at a temperature of 700-750°C to form an ingot, and then thoroughly stirring to ensure uniform composition; the homogenization treatment involves heating the ingot to 400-450°C and holding it at that temperature for 12-24 hours; the turning process removes surface oxide scale and defects, and the dimensional accuracy of the turned billet is controlled within ±0.5mm.

[0010] Preferably, in the preparation of the extrusion equipment and mold, the extrusion pressure of the extruder is determined according to the size and material of the hollow bar, generally 10-30MN; the planar diversion combination mold includes an upper mold base, a lower mold base, a diversion mold, a core mold and a core support, and multiple diversion holes are designed on the diversion mold. The number and size of the diversion holes are optimized according to the specifications of the hollow bar and the metal flow characteristics.

[0011] Preferably, in the preparation of the extrusion equipment and mold, the mold is made of hot work die steel H13, and after quenching and tempering treatment, the mold hardness reaches HRC48-52. The mold surface is nitrided to form a nitrided layer with a thickness controlled at 0.02-0.05mm.

[0012] Preferably, in the extrusion process parameter control, the billet heating temperature is 350-420℃, the heating rate is controlled at 5-10℃ / min; the preheating temperature of the extrusion cylinder and die is 300-380℃, the preheating time is 2-4 hours, and the die temperature fluctuation is kept within ±10℃ during the extrusion process.

[0013] Preferably, in the extrusion process parameter control, the extrusion speed is adjusted according to the specifications and material of the hollow bar, generally 0.5-2 m / min. For small-diameter, thin-walled hollow bars, a lower extrusion speed is used to ensure uniform metal flow and avoid defects. For large-diameter, thick-walled hollow bars, the extrusion speed can be appropriately increased, but close attention should be paid to temperature changes and product quality during the extrusion process. During the extrusion process, the extrusion pressure changes are monitored in real time by a pressure sensor, and the working parameters of the extruder are adjusted according to the extrusion pressure feedback. The initial extrusion pressure is generally controlled at 5-10 mN. As the extrusion process proceeds, the extrusion pressure is gradually adjusted according to the metal flow and product quality requirements. The maximum extrusion pressure does not exceed 80% of the rated pressure of the extruder. The lubricant is composed of 50%-60% rapeseed oil, 30%-40% flake graphite and 5%-10% borate ester. After mixing, it is stirred at 50-60℃ for 30 minutes until uniform, and then evenly applied to the surface of the billet and the surface of the die cavity to form a uniform lubricating film.

[0014] Preferably, in the post-extrusion processing, the cooling adopts a combination of air cooling and water cooling. First, it is naturally cooled in the air to 200-250°C, and then immediately placed in water to cool to room temperature.

[0015] Preferably, in the post-extrusion processing, straightening is performed using a multi-roller straightening method. The spacing and pressure of the straightening rollers are adjusted according to the diameter and wall thickness of the hollow bar to control the straightness error of the hollow bar within 0.5 mm / m.

[0016] Preferably, in the post-extrusion treatment, the surface treatment adopts a combination of chemical cleaning and mechanical polishing. First, it is soaked in an acidic cleaning agent with 5%-8% nitric acid solution at room temperature for 3-5 minutes, and then rinsed with deionized water until pH=6-7 to remove oxide scale and residual oil. Then, mechanical polishing is performed to make the surface roughness of the hollow rod reach Ra0.8-1.6μm.

[0017] The beneficial effects of this invention are as follows: 1. In this invention, by precisely controlling the composition ratio of soluble magnesium alloy (e.g., 85%-94% magnesium, 3%-8% aluminum, etc.), the problem of unstable performance caused by composition fluctuations in traditional processes is solved, enabling the alloy to possess both excellent solubility and mechanical strength. At the same time, the design of the planar splitting combination die, combined with strict temperature (350-420℃ for billet, 300-380℃ for die), speed (0.5-2m / min), and pressure control, effectively avoids defects such as cracks and wrinkles commonly encountered during extrusion. This ensures that the wall thickness uniformity error of the hollow bar is controlled within ±0.1mm, the surface roughness is reduced to Ra0.8-1.6μm, and the dimensional accuracy reaches within ±0.2mm, thereby improving the stability and reliability of product quality. 2. In this invention, the selection of a horizontal reverse extrusion press, combined with optimized process parameters, makes the metal flow more uniform and the extrusion pressure more stable, reducing the number of downtimes caused by material blockage and die wear. Compared with traditional extrusion methods, the plasticity of the billet is improved through homogenization treatment (holding at 400-450℃ for 12-24 hours). Combined with the high-temperature lubrication effect of special lubricant, the scrap rate of the extrusion process is reduced by more than 40%, the production cycle is shortened by 30%, and the output per shift is significantly increased, providing a reliable guarantee for large-scale production and improving production efficiency and process stability. 3. In this invention, by strictly controlling the addition ratio of elements such as calcium (0.2%-1.5%) and aluminum (3%-8%), abnormal dissolution rate caused by compositional imbalance is avoided. At the same time, the appropriate addition of rare earth elements (total ratio ≤1%) improves the corrosion resistance of the alloy, significantly enhances its service stability under complex working conditions, and fully guarantees the solubility and functional adaptability of the material. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the extrusion method for hollow rods of soluble magnesium alloy material in this invention. Detailed Implementation

[0019] 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, and 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.

[0020] like Figure 1 As shown, this embodiment of the invention provides a method for extruding hollow rods of soluble magnesium alloy material. The method for extruding hollow rods of soluble magnesium alloy material includes the following steps: S1. Raw material preparation: Select soluble magnesium alloy billets with specific composition ratios, melt them into ingots, and then perform homogenization treatment and machining. S2. Extrusion equipment and die preparation: A horizontal reverse extrusion press is selected, and a specially designed planar diversion combination die is adopted. The die is made of hot work die steel and is treated accordingly. S3. Extrusion process parameter control: Temperature control of billet, extrusion cylinder and die, setting appropriate extrusion speed and extrusion pressure and lubrication treatment; S4. Post-extrusion treatment: The extruded hollow bars are cooled, straightened and surface treated in sequence.

[0021] The composition ratio of the soluble magnesium alloy billet in the raw material preparation is as follows: magnesium (Mg) accounts for 85%-94%, and the purity (i.e., magnesium element content) needs to reach 99.95% or higher; aluminum (Al) accounts for 3%-8%; zinc (Zn) accounts for 1%-4%; calcium (Ca) accounts for 0.2%-1.5%; a small amount of manganese (Mn) can also be added according to actual needs, with an addition ratio not exceeding 0.5%; rare earth elements are a mixture of Ce and Nd, with Ce accounting for 0.4%-0.6% and Nd accounting for 0.2%-0.4%, and the total ratio ≤1%.

[0022] The raw material preparation process involves melting the raw materials in proportion under argon protection at a temperature of 700-750℃ to form ingots, followed by thorough stirring to ensure uniform composition. The homogenization process involves heating the ingots to 400-450℃ and holding them for 12-24 hours. When the calcium addition ratio is >1.0%, the homogenization temperature is increased to 430-450℃ and the holding time is extended to 18-24 hours. When the calcium addition ratio is ≤1.0%, the homogenization temperature is 400-430℃ and the holding time is 12-18 hours to ensure uniform distribution of calcium. The turning process removes surface oxide scale and defects, and the dimensional accuracy of the turned billet is controlled within ±0.5mm.

[0023] In the preparation of extrusion equipment and molds, the extrusion pressure of the extruder is determined according to the size and material of the hollow bar, generally 10-30MN. The planar diversion die assembly includes an upper die base, a lower die base, a diversion die, a core die, and a core support. The core die and the core support adopt an interference fit (fit tolerance H7 / u6) to ensure the stability of the core die position during extrusion and avoid wall defects on the inner wall of the hollow bar. Multiple diversion holes are designed on the diversion die. The number and size of the diversion holes are optimized according to the specifications of the hollow bar and the metal flow characteristics. When the outer diameter of the hollow bar is 50-100mm, the number of diversion holes is 4-6; when the outer diameter is >100mm, the number of diversion holes is 6-8. The diameter of the diversion holes is 1.5-2 times the wall thickness of the hollow bar, and the hole spacing is evenly distributed to ensure symmetrical metal diversion.

[0024] In the preparation of extrusion equipment and molds, the molds are made of hot work die steel H13. After quenching and tempering, the mold hardness reaches HRC48-52. The mold surface is nitrided to form a nitrided layer with a thickness controlled between 0.02-0.05mm. The thickness of the nitrided layer of 0.02-0.05mm was determined through multiple tests. This range can ensure that the surface hardness of the mold is ≥HV800, while avoiding interface stress concentration caused by excessive nitrided layer. The service life is increased by more than 30% compared with non-nitrided molds.

[0025] In the extrusion process parameter control, the billet heating temperature is 350-420℃, and the heating rate is controlled at 5-10℃ / min; the preheating temperature of the extrusion cylinder and die is 300-380℃, and the preheating time is 2-4 hours; during the extrusion process, the die temperature fluctuation is kept within ±10℃.

[0026] In the extrusion process parameter control, the extrusion speed is adjusted according to the specifications and material of the hollow bar, generally ranging from 0.5 to 2 m / min. For small-diameter, thin-walled hollow bars, a lower extrusion speed is used to ensure uniform metal flow and avoid defects. For large-diameter, thick-walled hollow bars, the extrusion speed can be appropriately increased, but close attention must be paid to temperature changes and product quality during the extrusion process. During the extrusion process, pressure sensors monitor the extrusion pressure changes in real time, and the operating parameters of the extruder are adjusted based on the extrusion pressure feedback. The initial extrusion pressure is generally controlled at 5- 10MN. As the extrusion process proceeds, the extrusion pressure is gradually adjusted according to the metal flow and product quality requirements. The maximum extrusion pressure shall not exceed 80% of the rated pressure of the extruder. The lubricant consists of 50%-60% rapeseed oil (viscosity 30-50 cSt, 40℃), 30%-40% flake graphite (particle size 200-500 mesh), and 5%-10% borate ester (as a high-temperature stabilizer). After mixing, the mixture is stirred at 50-60℃ for 30 minutes until uniform. It is then evenly applied to the surface of the billet and the surface of the mold cavity to form a uniform lubricating film.

[0027] In the post-extrusion processing, cooling is achieved by a combination of air cooling and water cooling. First, the material is naturally cooled in the air to 200-250℃, and then immediately placed in water to cool to room temperature. The air cooling range of 200-250℃ is determined based on the phase transformation temperature of magnesium alloys: at this temperature, the alloy has completed partial stratification. Water cooling can suppress grain coarsening and avoid thermal stress cracking caused by sudden temperature changes (water cooling temperature difference > 200℃ when > 250℃).

[0028] In the post-extrusion processing, a multi-roller straightening method is adopted. The spacing and pressure of the straightening rollers are adjusted according to the diameter and wall thickness of the hollow bar to control the straightness error of the hollow bar within 0.5mm / m.

[0029] In the post-extrusion treatment, the surface treatment adopts a combination of chemical cleaning and mechanical polishing. First, it is soaked in an acidic cleaning agent with 5%-8% nitric acid solution (volume fraction) at room temperature for 3-5 minutes, and then rinsed with deionized water until pH=6-7 to remove oxide scale and residual oil. Then, mechanical polishing is performed to make the surface roughness of the hollow rod reach Ra0.8-1.6μm.

[0030] It should be noted that, in this document, relational terms such as "first" and "second" are used only 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. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0031] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for extruding hollow rods of soluble magnesium alloy material, characterized in that: The extrusion method for the hollow rod of the soluble magnesium alloy material includes the following steps: S1. Raw material preparation: Select soluble magnesium alloy billets with specific composition ratios, melt them into ingots, and then perform homogenization treatment and machining. S2. Extrusion equipment and die preparation: A horizontal reverse extrusion press is selected, and a specially designed planar diversion combination die is adopted. The die is made of hot work die steel and is treated accordingly. S3. Extrusion process parameter control: Temperature control of billet, extrusion cylinder and die, setting appropriate extrusion speed and extrusion pressure and lubrication treatment; S4. Post-extrusion treatment: The extruded hollow bars are cooled, straightened and surface treated in sequence.

2. The extrusion method for a hollow rod of soluble magnesium alloy material according to claim 1, characterized in that: The composition ratio of the soluble magnesium alloy billet in the raw material preparation is as follows: magnesium accounts for 85%-94%, and the purity needs to reach 99.95% or higher; aluminum accounts for 3%-8%; zinc accounts for 1%-4%; calcium accounts for 0.2%-1.5%; a small amount of manganese can also be added according to actual needs, with an addition ratio not exceeding 0.5%; rare earth elements are a mixture of Ce and Nd, of which Ce accounts for 0.4%-0.6% and Nd accounts for 0.2%-0.4%, with a total ratio ≤1%.

3. The extrusion method for a hollow rod of soluble magnesium alloy material according to claim 1, characterized in that: The raw material preparation process involves melting each raw material in proportion under argon protection at a temperature of 700-750℃ to form an ingot, and then thoroughly stirring to ensure uniform composition. The homogenization treatment involves heating the ingot to 400-450℃ and holding it at that temperature for 12-24 hours. The turning process removes surface oxide scale and defects, and the dimensional accuracy of the turned billet is controlled within ±0.5mm.

4. The extrusion method for a hollow rod of soluble magnesium alloy material according to claim 1, characterized in that: In the preparation of the extrusion equipment and mold, the extrusion pressure of the extruder is determined according to the size and material of the hollow bar, which is generally 10-30MN; the planar diversion combination mold includes an upper mold base, a lower mold base, a diversion mold, a core mold and a core support. Multiple diversion holes are designed on the diversion mold, and the number and size of the diversion holes are optimized according to the specifications of the hollow bar and the metal flow characteristics.

5. The extrusion method for a hollow rod of soluble magnesium alloy material according to claim 1, characterized in that: In the preparation of the extrusion equipment and mold, the mold is made of hot work die steel H13, and after quenching and tempering treatment, the mold hardness reaches HRC48-52. The mold surface is nitrided to form a nitrided layer with a thickness controlled at 0.02-0.05mm.

6. The extrusion method for a hollow rod of soluble magnesium alloy material according to claim 1, characterized in that: In the extrusion process parameter control, the billet heating temperature is 350-420℃, and the heating rate is controlled at 5-10℃ / min; the preheating temperature of the extrusion cylinder and die is 300-380℃, and the preheating time is 2-4 hours; during the extrusion process, the die temperature fluctuation is kept within ±10℃.

7. The extrusion method for a hollow rod of soluble magnesium alloy material according to claim 1, characterized in that: In the extrusion process parameter control, the extrusion speed is adjusted according to the specifications and material of the hollow bar, generally 0.5-2 m / min. For small-diameter, thin-walled hollow bars, a lower extrusion speed is used to ensure uniform metal flow and avoid defects. For large-diameter, thick-walled hollow bars, the extrusion speed can be appropriately increased, but close attention should be paid to temperature changes and product quality during the extrusion process. During the extrusion process, the extrusion pressure changes are monitored in real time by a pressure sensor, and the working parameters of the extruder are adjusted according to the extrusion pressure feedback. The initial extrusion pressure is generally controlled at 5-10 mN. As the extrusion process proceeds, the extrusion pressure is gradually adjusted according to the metal flow and product quality requirements. The maximum extrusion pressure does not exceed 80% of the rated pressure of the extruder. The lubricant is composed of 50%-60% rapeseed oil, 30%-40% flake graphite and 5%-10% borate ester. After mixing, it is stirred at 50-60℃ for 30 minutes until uniform, and then evenly applied to the surface of the billet and the surface of the die cavity to form a uniform lubricating film.

8. The extrusion method for a hollow rod of soluble magnesium alloy material according to claim 1, characterized in that: In the post-extrusion processing, cooling is achieved by a combination of air cooling and water cooling. The air is first allowed to cool naturally to 200-250°C, and then the air is immediately placed in water to cool to room temperature.

9. The extrusion method for a hollow rod of soluble magnesium alloy material according to claim 1, characterized in that: In the post-extrusion processing, straightening is performed using a multi-roller straightening method. The spacing and pressure of the straightening rollers are adjusted according to the diameter and wall thickness of the hollow bar to control the straightness error of the hollow bar within 0.5 mm / m.

10. The extrusion method for a hollow rod of soluble magnesium alloy material according to claim 1, characterized in that: In the post-extrusion treatment, the surface treatment adopts a combination of chemical cleaning and mechanical polishing. First, it is soaked in an acidic cleaning agent with 5%-8% nitric acid solution at room temperature for 3-5 minutes, and then rinsed with deionized water until pH=6-7 to remove oxide scale and residual oil. Then, mechanical polishing is performed to make the surface roughness of the hollow rod reach Ra0.8-1.6μm.

Images