Material formula and preparation method of high-performance stainless steel seamless perforated pipe

Abstract

The invention discloses a material formula and a preparation method of a high-performance stainless steel seamless perforated pipe. A stainless steel base material and trace alloy elements in a specific proportion are selected according to the material formula to optimize the comprehensive performance of the pipe; the preparation method comprises the following steps: smelting and refining raw materials according to a formula to ensure uniform and pure components; through a special extrusion process, the extrusion temperature, speed and pressure are accurately controlled, so that the metal flows in the mold to form a seamless porous structure, and meanwhile, the porosity is regulated and controlled; and finally, performing heat treatment to eliminate internal stress and refine grains. Performance test results show that the high-performance stainless steel seamless porous pipe prepared by the method is low in corrosion rate and good in corrosion resistance in a 3.5% NaCl solution; the tensile strength is high, the ductility is good, and the high strength and toughness are both achieved; and the porosity can be accurately controlled, and pore distribution is uniform. A new scheme is provided for preparation of the high-performance stainless steel seamless perforated pipe, and the method has wide application prospects in multiple fields.

Description

Technical Field

[0001] The present invention relates to the technical field of metal material and pipe preparation, and in particular to a material formula and a preparation method of a high-performance stainless steel seamless porous pipe. Background Art

[0002] Stainless steel seamless porous tubes are widely used in many fields, such as chemical, petroleum, food, pharmaceutical and other industries, and are often used in filtration, separation, fluid transmission and other processes. However, existing stainless steel seamless porous tubes have some shortcomings. On the one hand, in terms of material properties, the comprehensive properties of some stainless steel materials such as corrosion resistance, strength and toughness cannot meet the requirements of certain extreme working conditions. For example, in strong acid, strong alkali or high temperature and high pressure environments, the pipes are prone to corrosion, deformation or even rupture, affecting their service life and safety. On the other hand, in terms of preparation methods, traditional porous tube preparation processes may have problems such as uneven pore distribution and difficulty in accurately controlling porosity, resulting in unstable indicators such as the filtration performance and fluid transmission efficiency of the pipe, limiting its use in high-precision application scenarios. Therefore, it is of great practical significance to develop a material formula and preparation method for high-performance stainless steel seamless porous tubes. Summary of the Invention

[0003] The purpose of the present invention is to provide a material formula and preparation method for high-performance stainless steel seamless porous tubes to solve the problems of insufficient material performance and preparation process defects of existing stainless steel seamless porous tubes, and to obtain high-performance stainless steel seamless porous tubes with excellent corrosion resistance, high strength, good toughness, uniform pore distribution and precise porosity control.

[0004] To achieve the above objectives, the present invention provides the following technical solutions:

[0005] A material formula for a high-performance stainless steel seamless porous tube consists of the following components, calculated by mass percentage: 60-70% iron, 18-22% chromium, 8-12% nickel, 2-4% molybdenum, 0.1-0.3% nitrogen, ≤0.03% carbon, ≤1.0% silicon, ≤2.0% manganese, ≤0.035% phosphorus, ≤0.03% sulfur, and 5-15% pore-forming agent, wherein the sum of the contents of each component is 100%.

[0006] Furthermore, the chromium forms a chromium oxide protective film on the surface of the stainless steel, thereby improving the corrosion resistance of the material; the nickel enhances the toughness and corrosion resistance of the material, especially improves the toughness of the material in a low-temperature environment; the molybdenum further improves the corrosion resistance of the material in a reducing medium, preventing pitting and crevice corrosion; the nitrogen partially replaces the role of nickel, thereby improving the corrosion resistance while increasing the strength of the material; the carbon content is controlled at a low level to avoid the formation of carbide precipitation and reducing the corrosion resistance of the material; the silicon and manganese act as deoxidizers and alloying elements to improve the fluidity of the molten steel and the quality of the ingot; the phosphorus and sulfur are harmful elements, and their contents are strictly controlled to prevent reducing the toughness and corrosion resistance of the material; the pore-forming agent is ammonium bicarbonate, which decomposes at high temperatures to produce gas, forming pores in the stainless steel matrix.

[0007] A method for preparing a high-performance stainless steel seamless porous tube, using the material formula according to any one of claims 1-2, comprising the following steps:

[0008] S1 Raw material preparation: Accurately weigh various raw materials according to the material formula, pre-treat the above metal raw materials to remove surface impurities, including oxide scale and oil stains;

[0009] S2 Melting: The pre-treated metal raw materials are placed in a vacuum induction melting furnace for melting. The melting temperature is controlled at 1500-1600℃ and the melting time is 2-3 hours. Nitrogen is added in the later stage of melting for nitriding treatment to make the nitrogen element evenly dissolved in the molten steel.

[0010] S3 Casting: The molten steel is poured into a pre-prepared mold. The casting temperature is controlled at 1400-1500℃ and the casting speed is uniform and stable to avoid defects such as pores and slag inclusions.

[0011] S4 hot extrusion: After the cast billet cools to room temperature, it is heated to 1000-1100℃ and then hot extruded to obtain a seamless tube billet. During the hot extrusion process, the extrusion ratio is controlled at 8-12 and the extrusion speed is 5-10mm / s to ensure the dimensional accuracy of the tube billet and the uniformity of the internal structure;

[0012] S5 heat treatment: The tube billet after hot extrusion is heat treated. The heat treatment process includes solution treatment and aging treatment. The solution treatment temperature is 1050-1150℃ and the holding time is 1-2 hours. Then it is quickly water quenched to fully dissolve the alloy elements in the matrix and obtain a uniform single-phase austenite structure. The aging treatment temperature is 450-550℃ and the holding time is 4-6 hours. The aging treatment allows the alloy elements to precipitate, strengthens the matrix structure, and improves the strength and hardness of the material.

[0013] S6 pore forming treatment: The heat-treated tube is placed in a high-temperature furnace for pore forming treatment. The pore forming treatment temperature is 200-300°C and the holding time is 2-4 hours. During the heating process, the pore forming agent ammonium bicarbonate decomposes to produce carbon dioxide, ammonia and water vapor, forming pores inside the tube. After the pore forming treatment is completed, it is slowly cooled to room temperature.

[0014] S7 post-treatment: Surface treatment is performed on the pipe after hole making, including pickling and polishing to remove surface oxide scale and impurities, improve the surface quality and corrosion resistance of the pipe, and then carry out dimensional inspection and performance testing to ensure that the pipe meets the design requirements.

[0015] Furthermore, the structural design of the mold is as follows: the inner cavity of the mold adopts a gradual cross-section design, the cross-sectional area at the entrance is larger, and the cross-sectional area gradually decreases with the flow direction of the molten steel, and the cross-sectional shape smoothly transitions from a circle to a circle that matches the outer diameter of the final seamless porous tube; a plurality of spiral guide grooves are arranged on the inner wall of the mold, the guide groove depth is 1-3mm, the width is 2-5mm, the spacing between adjacent guide grooves is 5-10mm, and the spiral angle of the guide groove is 15-30°, so as to guide the molten steel to flow evenly and reduce eddy currents and dead zones; a plurality of evenly distributed exhaust holes are arranged at the bottom of the mold, the exhaust hole diameter is 0.5-1.5mm, and the spacing between adjacent exhaust holes is 10-20mm, so as to facilitate the discharge of gas inside the molten steel during the casting process and ensure the solidification quality.

[0016] 5 Furthermore, the cooling rate of the slow cooling is no more than 50°C per hour.

[0017] The material formula and preparation method of the high-performance stainless steel seamless porous tube of the present invention have the following beneficial effects:

[0018] Excellent material properties: The present invention adopts a special material formula and rationally adds alloy elements such as chromium, nickel, molybdenum, and nitrogen to make the stainless steel seamless porous tube have excellent corrosion resistance, high strength and good toughness; it can still maintain stable performance under harsh working conditions such as strong acid, strong alkali, high temperature and high pressure, greatly extending the service life of the pipe.

[0019] Uniform pore distribution and precise porosity control: By optimizing the preparation process, especially the pore-forming process, the porosity can be precisely controlled and the pores can be evenly distributed inside the pipe. Uniform pore distribution helps improve the filtration performance and fluid transmission efficiency of the pipe, enabling it to perform better in high-precision application scenarios.

[0020] The preparation process is simple and feasible: the preparation method of the present invention has a relatively simple process flow, is easy to operate and control, has a low production cost, and is suitable for large-scale industrial production. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0022] (1) Example 1

[0023] Material formula: iron (Fe) 65%, chromium (Cr) 20%, nickel (Ni) 10%, molybdenum (Mo) 3%, nitrogen (N) 0.2%, carbon (C) 0.02%, silicon (Si) 0.8%, manganese (Mn) 1.5%, phosphorus (P) 0.02%, sulfur (S) 0.02%, pore-forming agent (ammonium bicarbonate) 10%.

[0024] Preparation process:

[0025] Accurately weigh various raw materials according to the above formula and pre-treat the metal raw materials;

[0026] The pretreated raw materials were placed in a vacuum induction melting furnace and smelted at 1550°C for 2.5 hours. Nitrogen was added in the later stage of smelting for nitriding treatment.

[0027] The molten steel was poured into the mold at 1450℃ with a casting speed of 8mm / s;

[0028] After the cast billet is cooled to room temperature, it is heated to 1050°C for hot extrusion with an extrusion ratio of 10 and an extrusion speed of 8 mm / s to obtain a seamless tube billet;

[0029] The tube was solution treated at 1100°C for 1.5 hours and then water quenched; then aged at 500°C for 5 hours;

[0030] The heat-treated tube was subjected to pore forming treatment at 250°C, kept at this temperature for 3 hours, and then slowly cooled to room temperature;

[0031] The pipes after hole making treatment are pickled and polished, and then subjected to size inspection and performance test.

[0032] (II) Example 2

[0033] Material formula: iron (Fe) 60%, chromium (Cr) 18%, nickel (Ni) 12%, molybdenum (Mo) 4%, nitrogen (N) 0.3%, carbon (C) 0.01%, silicon (Si) 0.5%, manganese (Mn) 1.0%, phosphorus (P) 0.01%, sulfur (S) 0.01%, pore-forming agent (ammonium bicarbonate) 15%.

[0034] Preparation process: Similar to Example 1, except that the melting temperature is controlled at 1500°C and the melting time is 3 hours; the casting temperature is 1400°C and the casting speed is 5 mm / s; the hot extrusion temperature is 1000°C, the extrusion ratio is 8, and the extrusion speed is 5 mm / s; the solution treatment temperature is 1050°C and the holding time is 2 hours; the aging treatment temperature is 450°C and the holding time is 6 hours; the pore-forming treatment temperature is 200°C and the holding time is 4 hours.

[0035] (III) Example 3

[0036] Material formula: iron (Fe) 70%, chromium (Cr) 22%, nickel (Ni) 8%, molybdenum (Mo) 2%, nitrogen (N) 0.1%, carbon (C) 0.03%, silicon (Si) 1.0%, manganese (Mn) 2.0%, phosphorus (P) 0.035%, sulfur (S) 0.03%, pore-forming agent (ammonium bicarbonate) 5%.

[0037] Preparation process: melting temperature is 1600℃, melting time is 2 hours; casting temperature is 1500℃, casting speed is 10mm / s; hot extrusion temperature is 1100℃, extrusion ratio is 12, extrusion speed is 10mm / s; solution treatment temperature is 1150℃, holding time is 1 hour; aging treatment temperature is 550℃, holding time is 4 hours; pore-making treatment temperature is 300℃, holding time is 2 hours.

[0038] Among them, the structural design of the above-mentioned mold is as follows: the inner cavity of the mold adopts a gradual cross-section design, the cross-sectional area at the entrance is larger, and the cross-sectional area gradually decreases with the flow direction of the molten steel, and the cross-sectional shape smoothly transitions from a circle to a circle that matches the outer diameter of the final seamless porous tube; a plurality of spiral guide grooves are arranged on the inner wall of the mold, the depth of the guide groove is 1-3mm, the width is 2-5mm, the spacing between adjacent guide grooves is 5-10mm, and the spiral angle of the guide groove is 15-30°, so as to guide the molten steel to flow evenly and reduce eddy currents and dead zones; a plurality of evenly distributed exhaust holes are arranged at the bottom of the mold, the diameter of the exhaust holes is 0.5-1.5mm, and the spacing between adjacent exhaust holes is 10-20mm, so as to facilitate the discharge of gas inside the molten steel during the casting process and ensure the solidification quality.

[0039] (4) Performance testing

[0040] Test items and test methods

[0041]

[0042] The high performance stainless steel seamless porous tubes prepared in the above three embodiments were subjected to performance tests, and the results are shown in the following table:

[0043]

[0044] The test results show that the high-performance stainless steel seamless porous tubes prepared in all three examples exhibit good corrosion resistance, high strength, and toughness. Furthermore, the porosity can be precisely controlled, and the pore distribution is relatively uniform. Example 2 exhibits the best corrosion resistance and tensile strength, while Example 3 achieves the best elongation. Overall, the high-performance stainless steel seamless porous tubes of the present invention exhibit excellent comprehensive properties, and the appropriate example can be selected for preparation based on specific needs.

[0045] The above description of the present invention and its embodiments is non-limiting and the actual implementation is not limited thereto. In short, if a person skilled in the art is inspired by the above description and, without departing from the purpose of the present invention, designs similar to the technical solution without creatively designing, they shall fall within the scope of protection of the present invention.

Claims

1. A material formula of a high-performance stainless steel seamless porous pipe, characterized in that: By mass percentage, it is composed of the following components: iron 60-70%, chromium 18-22%, nickel 8-12%, molybdenum 2-4%, nitrogen 0.1-0.3%, carbon ≤0.03%, silicon ≤1.0%, manganese ≤2.0%, phosphorus ≤0.035%, sulfur ≤0.03%, pore-forming agent 5-15%, and the sum of the contents of each component is 100%.

2. The material formula of a high-performance stainless steel seamless porous tube according to claim 1 is characterized by: The chromium forms a chromium oxide protective film on the surface of the stainless steel, improving the corrosion resistance of the material; The nickel enhances the toughness and corrosion resistance of the material, especially improving the toughness of the material in a low-temperature environment; the molybdenum further improves the corrosion resistance of the material in a reducing medium and prevents pitting corrosion and crevice corrosion; the nitrogen partially replaces the role of nickel, thereby improving the corrosion resistance while increasing the strength of the material; the carbon content is controlled at a low level to avoid the formation of carbide precipitation and reducing the corrosion resistance of the material; the silicon and manganese act as deoxidizers and alloying elements to improve the fluidity of the molten steel and the quality of the casting; the phosphorus and sulfur are harmful elements, and their contents are strictly controlled to prevent reducing the toughness and corrosion resistance of the material; the pore-forming agent is ammonium bicarbonate, which decomposes at high temperature to produce gas and form pores in the stainless steel matrix.

3. A method for preparing a high-performance stainless steel seamless porous tube, characterized by: The material formulation according to any one of claims 1 to 2 comprises the following steps: S1 Raw material preparation: Accurately weigh various raw materials according to the material formula, pre-treat the above metal raw materials to remove surface impurities, including oxide scale and oil stains; S2 Melting: The pre-treated metal raw materials are placed in a vacuum induction melting furnace for melting. The melting temperature is controlled at 1500-1600℃ and the melting time is 2-3 hours. Nitrogen is added in the later stage of melting for nitriding treatment to make the nitrogen element evenly dissolved in the molten steel. S3 Casting: The molten steel is poured into a pre-prepared mold. The casting temperature is controlled at 1400-1500℃. The casting speed is uniform and stable to avoid defects such as pores and slag inclusions. S4 hot extrusion: After the cast billet cools to room temperature, it is heated to 1000-1100℃ and then hot extruded to obtain a seamless tube billet. During the hot extrusion process, the extrusion ratio is controlled at 8-12 and the extrusion speed is 5-10mm / s to ensure the dimensional accuracy of the tube billet and the uniformity of the internal structure; S5 heat treatment: The tube billet after hot extrusion is heat treated. The heat treatment process includes solution treatment and aging treatment. The solution treatment temperature is 1050-1150℃ and the holding time is 1-2 hours. Then it is quickly water quenched to fully dissolve the alloy elements in the matrix and obtain a uniform single-phase austenite structure. The aging treatment temperature is 450-550℃ and the holding time is 4-6 hours. The aging treatment allows the alloy elements to precipitate, strengthens the matrix structure, and improves the strength and hardness of the material. S6 pore forming treatment: The heat-treated tube is placed in a high-temperature furnace for pore forming treatment. The pore forming treatment temperature is 200-300°C and the holding time is 2-4 hours. During the heating process, the pore forming agent ammonium bicarbonate decomposes to produce carbon dioxide, ammonia and water vapor, forming pores inside the tube. After the pore forming treatment is completed, it is slowly cooled to room temperature. S7 post-treatment: Surface treatment is performed on the pipe after hole making, including pickling and polishing to remove surface oxide scale and impurities, improve the surface quality and corrosion resistance of the pipe, and then carry out dimensional inspection and performance testing to ensure that the pipe meets the design requirements.

4. The method for preparing a high-performance stainless steel seamless porous tube according to claim 3, characterized in that: The structural design of the mold is as follows: the mold cavity adopts a gradual cross-section design, with a larger cross-sectional area at the entrance, and the cross-sectional area gradually decreases as the molten steel flows, and the cross-sectional shape smoothly transitions from a circle to a circle that matches the outer diameter of the final seamless porous tube; a plurality of spiral guide grooves are provided on the wall surface of the mold cavity, with a depth of 1-3 mm, a width of 2-5 mm, a spacing of 5-10 mm between adjacent guide grooves, and a spiral angle of 15-30 degrees, so as to guide the molten steel to flow evenly and reduce eddy currents and dead zones; a plurality of evenly distributed exhaust holes are provided at the bottom of the mold, with a diameter of 0.5-1.5 mm and a spacing of 10-20 mm between adjacent exhaust holes, so as to facilitate the discharge of gas inside the molten steel during the casting process and ensure the solidification quality.

5. The method for preparing a high-performance stainless steel seamless porous tube according to claim 3, characterized in that: The slow cooling process is performed at a cooling rate of no more than 50° C. per hour.

Images