Stainless steel seamless tube and manufacturing method thereof

Abstract

The invention discloses a stainless steel seamless tube and a manufacturing method thereof, and belongs to seamless steel tubes and treatment related fields. The stainless steel seamless tube comprises the following components in percentage by mass: 14.5%-15.5% of Cr, 0.03%-0.05% of C, 7.5%-8.5% of Ni, 1.6%-2.0% of Mn, 1.2%-1.4% of Si, 0.8%-1.2% of Mo, 0.3%-0.5% of Cu, 0.25%-0.35% of Nb, 0.08%-0.12% of A1, 0.02%-0.04% of V, less than or equal to 0.03% of P, less than or equal to 0.02% of S, 0.06%-0.10% of rare earth element yttrium and the balance of Fe and other inevitable impurity elements. The preparation cost is reduced, and meanwhile, the prepared seamless steel tube is excellent in mechanical property.

Description

Technical Field

[0001] The invention belongs to the field of seamless steel pipes and related processing, and in particular relates to a stainless steel seamless pipe and a manufacturing method thereof. Background Art

[0002] During the hot piercing process, the stainless steel billet is prone to hard friction with the plug, causing scratches and inclusions on the billet surface, resulting in a significant decrease in the mechanical strength of the steel pipe, affecting product performance. It will also cause a lot of wear and deformation of the plug, affecting its service life and increasing production costs.

[0003] After analysis, the reason for the scratches and inclusions on the surface of the billet is that the stainless steel seamless pipe has a high content of Cr. After the billet is heated, more high-temperature ferrite phase will be produced on the surface. This phase is a brittle phase, which makes it easy for microcracks to form on the surface of the pipe. Under the shear stress of perforation, it is easy to produce hard extrusion and scratches, resulting in the shedding of lubricants and the wear of the plug, which eventually accumulates at the scratches, causing more inclusions in the billet, reducing the mechanical properties of the seamless steel pipe, and easily causing damage to production equipment such as the plug. The above content is the discovery of the inventor during the research and development process and should not be regarded as prior art. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the deficiencies in the prior art, the present invention provides a stainless steel seamless pipe and a method for manufacturing the same.

[0006] (II) Technical solution

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0008] A seamless stainless steel pipe comprises the following components, measured by mass percentage: Cr14.5-15.5%, C 0.03-0.05%, Ni 7.5-8.5%, Mn 1.6-2.0%, Si1.2-1.4%, Mo 0.8-1.2%, Cu 0.3-0.5%, Nb 0.25-0.35%, A1 0.08-0.12%, V 0.02-0.04%, P≤0.03%, S≤0.02%, rare earth element yttrium 0.06-0.10%, and the balance is Fe and other inevitable impurity elements.

[0009] A method for preparing a stainless steel seamless pipe comprises the following steps:

[0010] S1: Vacuum smelting: According to the mass percentage, each raw material is smelted in a vacuum electric furnace to obtain molten steel, which is refined in AOD, LF furnace and VD furnace and then continuously cast or mold cast into steel billets;

[0011] S2: billet forging: heating the billet prepared in S1 to 1200-1240°C, keeping the temperature for 4-6 hours, and then forging the heated billet into a round billet;

[0012] S3: Piercing and rolling: a centering hole is punched on the end face of the round billet prepared in S2, and then the round billet is placed at a temperature of 1120-1160°C for 2-4 hours, and then pierced with a plug coated with a lubricant, and naturally cooled after piercing to obtain a hollow tube billet;

[0013] S4: cold working: placing the hollow tube blank prepared in S3 in a cold rolling unit for cold rolling to obtain a tubular body;

[0014] S5: Quenching and tempering: heat treatment is performed on the tubular body prepared in S4, the normalizing temperature is 950-1050°C, the tempering temperature is between 600-700°C, the holding time is 1.5-2.5h, and the semi-finished steel pipe is taken out of the furnace and cooled to room temperature;

[0015] S6: Finishing treatment: The semi-finished steel pipe prepared in S5 is straightened, cut, shot peened, and flaw detected to obtain a stainless steel seamless pipe.

[0016] Furthermore, the start forging temperature of the round billet in S2 is 1050-1150°C, and the final forging temperature is 900-1000°C.

[0017] Furthermore, the outer diameter expansion rate of the round steel billet in S3 during piercing is 10%.

[0018] Furthermore, the lubricant coating method in S3 is: uniformly coating the lubricant on the surface of the perforating head, keeping the temperature at 1300-1340° C. for 2-4 hours, and cooling to room temperature.

[0019] Furthermore, the method for preparing the lubricant comprises the following steps:

[0020] A1: Take the following components by mass percentage: 3-5% water glass, 2-4% dextrin powder, and the balance water, mix them evenly, heat to 90-100°C, stir for 20-40 minutes, and cool to room temperature to obtain a wet component;

[0021] A2: Take the following components by mass percentage: 30-40% silicon carbide, 15-20% potassium feldspar powder, 8%-12% graphite, and the balance glass powder, mix well, and obtain a lubricating component;

[0022] A3: The wetting component obtained in A1 and the lubricating component obtained in A2 are mixed evenly, wherein the mass of the wetting component is 5.5-6.5% of the mass of the lubricating component, to obtain a lubricant.

[0023] Furthermore, the particle size of silicon carbide in A2 is 1000-2000 mesh, and the particle size of potassium feldspar powder and glass powder is 200-2000 mesh.

[0024] Furthermore, the cold working deformation control amount of the hollow tube blank during the cold rolling treatment in S4 is 40-50%.

[0025] After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0026] 1. The present invention improves the plastic deformation ability of ferrite structure under high temperature conditions by adding rare earth element yttrium, so that the ferrite phase and the austenite phase produce coordinated deformation, thereby reducing the formation of fine cracks in the ferrite at the junction of the plug.

[0027] In addition, by improving the plasticity of the pipe, reducing the hard friction and scratches between it and the plug, and reducing the degree of plug wear, the large plastic deformation during the perforation process can improve the shape and distribution of inclusions, indirectly reducing the impact of inclusions on the mechanical strength of the pipe.

[0028] 2. The silicon carbide of the present invention has high strength and hardness, can improve the shear and wear resistance of the lubricating material, reduce the loss of the lubricating material, and protect the ferrite plug to the greatest extent.

[0029] In addition, potassium feldspar powder has extremely high bonding strength at high temperatures and can react with silicon carbide to form an alumina-silicon dioxide film, which makes the lubricating material have both strength and toughness, and keeps the surface of the plug smooth under extrusion and thermal effects, reducing the scratches and inclusions on the pipe, thereby greatly reducing the loss of the plug during the perforation process and reducing the impact on the mechanical strength of the pipe.

[0030] 3. The use of lubricants in the preparation process of the seamless steel pipe of the present invention reduces the damage to the plug during the piercing process, thereby extending the service life of the plug and reducing the preparation cost in the preparation process of the seamless steel pipe of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Embodiment 1: A stainless steel seamless pipe comprises the following components, measured by mass percentage: Cr 15.0%, C 0.04%, Ni 8.0%, Mn 1.8%, Si 1.3%, Mo 1.0%, Cu 0.4%, Nb 0.30%, A1 0.10%, V 0.03%, P 0.0153%, S 0.01%, rare earth element yttrium 0.08%, and the balance Fe and other inevitable impurity elements.

[0033] A method for preparing a stainless steel seamless pipe comprises the following steps:

[0034] S1: Vacuum smelting: According to the mass percentage, each raw material is smelted in a vacuum electric furnace to obtain molten steel, which is refined in AOD, LF furnace and VD furnace and then continuously cast or mold cast into steel billets;

[0035] S2: billet forging: heating the billet prepared in S1 to 1220°C, keeping the temperature for 5 hours, and then forging the heated billet into a round billet;

[0036] S3: Piercing and rolling: a centering hole is punched on the end face of the round billet prepared in S2, and then the round billet is placed at 1140°C for 3 hours, and then pierced with a plug coated with a lubricant, and naturally cooled after piercing to obtain a hollow tube billet;

[0037] S4: cold working: placing the hollow tube blank prepared in S3 in a cold rolling unit for cold rolling to obtain a tubular body;

[0038] S5: Quenching and tempering: heat treatment is performed on the tubular body prepared in S4, the normalizing temperature is 1000℃, the tempering temperature is between 650℃, the holding time is 2h, and the semi-finished steel pipe is taken out of the furnace and cooled to room temperature;

[0039] S6: Finishing treatment: The semi-finished steel pipe prepared in S5 is straightened, cut, shot peened, and flaw detected to obtain a stainless steel seamless pipe.

[0040] The starting forging temperature of the round billet in S2 is 1100°C, and the final forging temperature is 950°C.

[0041] The outer diameter expansion rate of the round steel billet in S3 during piercing is 10%.

[0042] The lubricant coating method in S3 is: uniformly coating the lubricant on the surface of the punch head, keeping the temperature at 1320° C. for 3 hours, and cooling to room temperature.

[0043] The preparation method of the lubricant comprises the following steps:

[0044] A1: Take the following components by mass percentage: 4% water glass, 3% dextrin powder, and the balance water, mix well, heat to 95°C, stir for 30 minutes, and cool to room temperature to obtain a wet component;

[0045] A2: Take the following components by mass percentage: 35% silicon carbide, 18% potassium feldspar powder, 10% graphite, and the balance glass powder, mix them well to obtain a lubricating component.

[0046] A3: The wetting component obtained in A1 and the lubricating component obtained in A2 are mixed evenly, wherein the mass of the wetting component is 6.0% of the mass of the lubricating component, to obtain a lubricant.

[0047] The particle size of silicon carbide in A2 is 1500 mesh, and the particle size of potassium feldspar powder and glass powder is 500 mesh.

[0048] The cold working deformation control amount of the hollow tube blank during the cold rolling treatment in S4 is 40%.

[0049] Embodiment 2: A stainless steel seamless pipe comprises the following components, measured by mass percentage: Cr 14.5%, C 0.03%, Ni 7.5%, Mn 1.6%, Si 1.2%, Mo 0.8%, Cu 0.3%, Nb 0.25%, A1 0.08%, V 0.02%, P 0.01%, S 0.008%, rare earth element yttrium 0.06%, and the balance Fe and other inevitable impurity elements.

[0050] A method for preparing a stainless steel seamless pipe comprises the following steps:

[0051] S1: Vacuum smelting: According to the mass percentage, each raw material is smelted in a vacuum electric furnace to obtain molten steel, which is refined in AOD, LF furnace and VD furnace and then continuously cast or mold cast into steel billets;

[0052] S2: billet forging: heating the billet prepared in S1 to 1200°C, keeping the temperature for 4 hours, and then forging the heated billet into a round billet;

[0053] S3: piercing and rolling: a centering hole is punched on the end face of the round steel billet prepared in S2, a lubricant is coated on the head of the round steel billet, and then the round steel billet is placed at 1120°C for 2 hours, and then pierced, and naturally cooled after piercing to obtain a hollow tube billet;

[0054] S4: cold working: placing the hollow tube blank prepared in S3 in a cold rolling unit for cold rolling to obtain a tubular body;

[0055] S5: Quenching and tempering: heat treatment is performed on the tubular body prepared in S4, the normalizing temperature is 950℃, the tempering temperature is between 600℃, the holding time is 1.5h, and then the semi-finished steel pipe is taken out of the furnace and cooled to room temperature;

[0056] S6: Finishing treatment: The semi-finished steel pipe prepared in S5 is straightened, cut, shot peened, and flaw detected to obtain a stainless steel seamless pipe.

[0057] The starting forging temperature of the round billet in S2 is 1050°C, and the final forging temperature is 900°C.

[0058] The outer diameter expansion rate of the round steel billet in S3 during piercing is 10%.

[0059] The lubricant coating method in S3 is: uniformly coating the lubricant on the surface of the punch head, keeping the temperature at 1300° C. for 2 hours, and cooling to room temperature.

[0060] The preparation method of the lubricant comprises the following steps:

[0061] A1: Take the following components by mass percentage: 3% water glass, 2% dextrin powder, and the balance water, mix well, heat to 90°C, stir for 20 minutes, and cool to room temperature to obtain a wet component;

[0062] A2: Take the following components by mass percentage: 30% silicon carbide, 15% potassium feldspar powder, 8% graphite, and the balance glass powder, mix well, and obtain a lubricating component;

[0063] A3: The wetting component obtained in A1 and the lubricating component obtained in A2 are mixed evenly, wherein the mass of the wetting component is 5.5% of the mass of the lubricating component, to obtain a lubricant.

[0064] The particle size of silicon carbide in A2 is 1000 mesh, and the particle size of potassium feldspar powder and glass powder is 200 mesh.

[0065] The cold working deformation control amount of the hollow tube blank during the cold rolling treatment in S4 is 40%.

[0066] Example 3: A stainless steel seamless pipe, comprising the following components, in percentage by mass: Cr 15.5%, C 0.05%, Ni 8.5%, Mn 2.0%, Si 1.4%, Mo 1.2%, Cu 0.5%, Nb 0.35%, A1 0.12%, V 0.04%, P 0.03%, S 0.02%, rare earth element yttrium 0.10%, and the balance Fe and other inevitable impurity elements.

[0067] A method for preparing a stainless steel seamless pipe comprises the following steps:

[0068] S1: Vacuum smelting: According to the mass percentage, each raw material is smelted in a vacuum electric furnace to obtain molten steel, which is refined in AOD, LF furnace and VD furnace and then continuously cast or mold cast into steel billets;

[0069] S2: billet forging: heating the billet prepared in S1 to 1240°C, keeping the temperature for 6 hours, and then forging the heated billet into a round billet;

[0070] S3: piercing and rolling: a centering hole is punched on the end face of the round steel billet prepared in S2, a lubricant is coated on the head of the round steel billet, and then the round steel billet is placed at 1160°C for 4 hours, and then pierced, and naturally cooled after piercing to obtain a hollow tube billet;

[0071] S4: cold working: placing the hollow tube blank prepared in S3 in a cold rolling unit for cold rolling to obtain a tubular body;

[0072] S5: Quenching and tempering: heat treatment is performed on the tubular body prepared in S4, the normalizing temperature is 1050°C, the tempering temperature is between 700°C, the holding time is 2.5h, and the semi-finished steel pipe is taken out of the furnace and cooled to room temperature;

[0073] S6: Finishing treatment: The semi-finished steel pipe prepared in S5 is straightened, cut, shot peened, and flaw detected to obtain a stainless steel seamless pipe.

[0074] The starting forging temperature of the round billet in S2 is 1150°C, and the final forging temperature is 1000°C.

[0075] The outer diameter expansion rate of the round steel billet in S3 during piercing is 10%.

[0076] The lubricant coating method in S3 is: the lubricant is evenly coated on the surface of the punch head, kept at a high temperature of 1340° C. for 4 hours, and then cooled to room temperature.

[0077] The preparation method of the lubricant comprises the following steps:

[0078] A1: Take the following components by mass percentage: 5% water glass, 4% dextrin powder, and the balance water, mix well, heat to 100°C, stir for 40 minutes, and cool to room temperature to obtain a wet component;

[0079] A2: Take the following components by mass percentage: 40% silicon carbide, 20% potassium feldspar powder, 12% graphite, and the balance glass powder, mix well, and obtain a lubricating component;

[0080] A3: Mix the wetting component obtained in A1 and the lubricating component obtained in A2, wherein the mass of the wetting component is 6.5% of the mass of the lubricating component, to obtain a lubricant.

[0081] The particle size of silicon carbide in A2 is 2000 mesh, and the particle size of potassium feldspar powder and glass powder is 2000 mesh.

[0082] The cold working deformation control amount of the hollow tube blank during the cold rolling treatment in S4 is 50%.

[0083] Example 4: A stainless steel seamless pipe, comprising the following components, in percentage by mass: Cr 14.8%, C 0.035%, Ni 7.8%, Mn 1.7%, Si 1.25%, Mo 0.9%, Cu 0.35%, Nb 0.28%, A1 0.09%, V 0.025%, P 0.008%, S 0.007%, rare earth element yttrium 0.07%, and the balance Fe and other inevitable impurity elements.

[0084] A method for preparing a stainless steel seamless pipe comprises the following steps:

[0085] S1: Vacuum smelting: According to the mass percentage, each raw material is smelted in a vacuum electric furnace to obtain molten steel, which is refined in AOD, LF furnace and VD furnace and then continuously cast or mold cast into steel billets;

[0086] S2: billet forging: heating the billet prepared in S1 to 1210°C, keeping the temperature for 4.5 hours, and then forging the heated billet into a round billet;

[0087] S3: Piercing and rolling: a centering hole is punched on the end face of the round billet prepared in S2, a lubricant is coated on the head of the round billet, and then the round billet is placed at 1130°C for 2.5 hours, and then pierced, and naturally cooled after piercing to obtain a hollow tube billet;

[0088] S4: cold working: placing the hollow tube blank prepared in S3 in a cold rolling unit for cold rolling to obtain a tubular body;

[0089] S5: Quenching and tempering: heat treatment is performed on the tubular body prepared in S4, the normalizing temperature is 980°C, the tempering temperature is between 620°C, the holding time is 1.7h, and the semi-finished steel pipe is taken out of the furnace and cooled to room temperature;

[0090] S6: Finishing treatment: The semi-finished steel pipe prepared in S5 is straightened, cut, shot peened, and flaw detected to obtain a stainless steel seamless pipe.

[0091] The starting forging temperature of the round billet in S2 is 1090°C, and the final forging temperature is 910°C.

[0092] The outer diameter expansion rate of the round steel billet in S3 during piercing is 10%.

[0093] The lubricant coating method in S3 is: the lubricant is evenly coated on the surface of the perforating head, kept at a high temperature of 1310° C. for 2.5 hours, and then cooled to room temperature.

[0094] The preparation method of the lubricant comprises the following steps:

[0095] A1: Take the following components by mass percentage: 3.5% water glass, 2.5% dextrin powder, and the balance water, mix well, heat to 94°C, stir for 25 minutes, and cool to room temperature to obtain a wet component;

[0096] A2: Take the following components by mass percentage: 33% silicon carbide, 16% potassium feldspar powder, 9% graphite, and the balance glass powder, mix well, and obtain a lubricating component;

[0097] A3: The wetting component obtained in A1 and the lubricating component obtained in A2 are mixed evenly, wherein the mass of the wetting component is 5.7% of the mass of the lubricating component, to obtain a lubricant.

[0098] The particle size of silicon carbide in A2 is 1200 mesh, and the particle size of potassium feldspar powder and glass powder is 400 mesh.

[0099] The cold working deformation control amount of the hollow tube blank during the cold rolling treatment in S4 is 42%.

[0100] Example 5: A stainless steel seamless pipe, comprising the following components, in percentage by mass: Cr 15.2%, C 0.045%, Ni 8.2%, Mn 1.9%, Si 1.35%, Mo 1.1%, Cu 0.45%, Nb 0.32%, A1 0.11%, V 0.035%, P 0.028%, S 0.018%, rare earth element yttrium 0.08%, and the balance Fe and other inevitable impurity elements.

[0101] A method for preparing a stainless steel seamless pipe comprises the following steps:

[0102] S1: Vacuum smelting: According to the mass percentage, each raw material is smelted in a vacuum electric furnace to obtain molten steel, which is refined in AOD, LF furnace and VD furnace and then continuously cast or mold cast into steel billets;

[0103] S2: billet forging: heating the billet prepared in S1 to 1230°C, keeping the temperature for 5.5h, and then forging the heated billet into a round billet;

[0104] S3: piercing and rolling: a centering hole is punched on the end face of the round billet prepared in S2, a lubricant is coated on the head of the round billet, and then the round billet is placed at 1150°C for 3.5 hours, and then pierced, and naturally cooled after piercing to obtain a hollow tube billet;

[0105] S4: cold working: placing the hollow tube blank prepared in S3 in a cold rolling unit for cold rolling to obtain a tubular body;

[0106] S5: Quenching and tempering: heat treatment is performed on the tubular body prepared in S4, the normalizing temperature is 1030°C, the tempering temperature is between 690°C, the holding time is 2.3h, and the semi-finished steel pipe is taken out of the furnace and cooled to room temperature;

[0107] S6: Finishing treatment: The semi-finished steel pipe prepared in S5 is straightened, cut, shot peened, and flaw detected to obtain a stainless steel seamless pipe.

[0108] The starting forging temperature of the round billet in S2 is 1130°C, and the final forging temperature is 980°C.

[0109] The outer diameter expansion rate of the round steel billet in S3 during piercing is 10%.

[0110] The lubricant coating method in S3 is: uniformly coating the lubricant on the surface of the punch head, keeping the temperature at 1330° C. for 3.5 hours, and cooling to room temperature.

[0111] The preparation method of the lubricant comprises the following steps:

[0112] A1: Take the following components by mass percentage: 4.5% water glass, 3.4% dextrin powder, and the balance water, mix well, heat to 980°C, stir for 35 minutes, and cool to room temperature to obtain a wet component;

[0113] A2: Take the following components by mass percentage: 38% silicon carbide, 19% potassium feldspar powder, 11% graphite, and the balance glass powder, mix well, and obtain a lubricating component;

[0114] A3: The wetting component obtained in A1 and the lubricating component obtained in A2 are mixed evenly, wherein the mass of the wetting component is 6.3% of the mass of the lubricating component, to obtain a lubricant.

[0115] The particle size of silicon carbide in A2 is 1900 mesh, and the particle size of potassium feldspar powder and glass powder is 1500 mesh.

[0116] The cold working deformation control amount of the hollow tube blank during the cold rolling treatment in S4 is 48%.

[0117] Comparative Example 1: The only difference from Example 1 is that the rare earth element yttrium is not added to the stainless steel seamless pipe component.

[0118] A stainless steel seamless pipe comprises the following components, measured by mass percentage: Cr 15.0%, C 0.04%, Ni 8.0%, Mn 1.8%, Si 1.3%, Mo 4.0%, Cu 0.4%, Nb 0.30%, A1 0.10%, V 0.03%, P 0.015%, S 0.01%, and the balance is Fe and other inevitable impurity elements.

[0119] Comparative Example 2: The only difference from Example 1 is that, in the preparation of the lubricant, no silicon carbide is added to the lubricating component.

[0120] The preparation method of the lubricant comprises the following steps:

[0121] A1: Take the following components by mass percentage: 4% water glass, 3% dextrin powder, and the balance water, mix well, heat to 95°C, stir for 30 minutes, and cool to room temperature to obtain a wet component;

[0122] A2: Take the following components by mass percentage: 18% potassium feldspar powder, 10% graphite, and the balance glass powder, mix well, and obtain a lubricating component;

[0123] A3: The wetting component obtained in A1 and the lubricating component obtained in A2 are mixed evenly, wherein the mass of the wetting component is 6.0% of the mass of the lubricating component, to obtain a lubricant.

[0124] Comparative Example 3: The only difference from Example 1 is that, in the preparation of the lubricant, no potassium feldspar powder is added to the lubricating component.

[0125] The preparation method of the lubricant comprises the following steps:

[0126] A1: Take the following components by mass percentage: 4% water glass, 3% dextrin powder, and the balance water, mix well, heat to 95°C, stir for 30 minutes, and cool to room temperature to obtain a wet component;

[0127] A2: Take the following components by mass percentage: 35% silicon carbide, 10% graphite, and the balance glass powder, mix well, and obtain a lubricating component;

[0128] A3: The wetting component obtained in A1 and the lubricating component obtained in A2 are mixed evenly, wherein the mass of the wetting component is 6.0% of the mass of the lubricating component, to obtain a lubricant.

[0129] Comparative Example 4: The only difference from Example 1 is that, in the preparation of the lubricant, no potassium feldspar powder is added to the lubricating component, and no silicon carbide is added.

[0130] The preparation method of the lubricant comprises the following steps:

[0131] A1: Take the following components by mass percentage: 4% water glass, 3% dextrin powder, and the balance water, mix well, heat to 95°C, stir for 30 minutes, and cool to room temperature to obtain a wet component;

[0132] A2: Take the following components by mass percentage: 10% graphite and the balance glass powder, mix well to obtain a lubricating component;

[0133] A3: The wetting component obtained in A1 and the lubricating component obtained in A2 are mixed evenly, wherein the mass of the wetting component is 6.0% of the mass of the lubricating component, to obtain a lubricant.

[0134] The tensile strength was tested according to ASTM standards, and the number of plug perforations of the plug during the preparation of the seamless steel pipe was measured as shown in Table 1:

[0135] Table 1

[0136] Seamless pipe tensile strength / MPa Number of holes per head Example 1 533.2 581 Example 2 524.6 574 Example 3 539.1 577 Example 4 528.7 588 Example 5 541.4 562 Comparative Example 1 517.6 496 Comparative Example 2 489.3 459 Comparative Example 3 441.4 525 Comparative Example 4 456.7 418

[0137] The tensile strength of the seamless steel pipes prepared in Examples 1 to 5 indicates that the preparation method of the present invention is feasible and the seamless steel pipes prepared by the technical solution of the present invention are of excellent quality.

[0138] The number of plug perforations of the seamless steel pipe in the preparation process of Examples 1 to 5 indicates that the plug quality in the preparation process of the seamless steel pipe of the present invention is superior, the service life is long, and the preparation cost of the seamless steel pipe is reduced.

[0139] The only difference between Comparative Example 1 and Example 1 is that the rare earth element yttrium is not added to the stainless steel seamless pipe component.

[0140] The tensile strength of the seamless steel pipe in Example 1 is greater than the tensile strength of the seamless steel pipe prepared in Comparative Example 1, indicating that the rare earth element yttrium can improve the mechanical properties of the seamless steel pipe.

[0141] The number of plug perforations of the plug during the preparation of the seamless steel pipe in Example 1 is greater than the number of plug perforations of the plug during the preparation of the seamless steel pipe in Comparative Example 1, indicating that the rare earth element yttrium can reduce the damage to the plug caused by the perforation process in the preparation of the seamless steel pipe, thereby extending the service life of the plug.

[0142] The only difference between Comparative Example 2 and Example 1 is that, in the preparation of the lubricant, no silicon carbide is added to the lubricating component.

[0143] The tensile strength of the seamless steel pipe in Example 1 is greater than the tensile strength of the seamless steel pipe prepared in Comparative Example 2, and the number of head perforations of the plug during the preparation of the seamless steel pipe in Example 1 is greater than the number of head perforations of the plug during the preparation of the seamless steel pipe in Comparative Example 2.

[0144] It is shown that the lubricant prepared by adding silicon carbide and coating it on the plug for perforation is more conducive to improving the tensile strength of the seamless steel pipe; and it can reduce the damage to the plug during the perforation process, thereby extending the service life of the plug.

[0145] The only difference between Comparative Example 3 and Example 1 is that, in the preparation of the lubricant, no potassium feldspar powder is added to the lubricating component.

[0146] The tensile strength of the seamless steel pipe in Example 1 is greater than the tensile strength of the seamless steel pipe prepared in Comparative Example 3, and the number of head perforations of the plug in the preparation process of the seamless steel pipe in Example 1 is greater than the number of head perforations of the plug in the preparation process of the seamless steel pipe in Comparative Example 3.

[0147] The results show that the lubricant prepared by adding potassium feldspar powder and coating it on the plug for perforation is more conducive to improving the tensile strength of the seamless steel pipe; and it can reduce the damage to the plug during the perforation process, thereby extending the service life of the plug.

[0148] The only difference between Comparative Example 4 and Example 1 is that, in the preparation of the lubricant, no potassium feldspar powder is added to the lubricant, and no silicon carbide is added.

[0149] The tensile strength of the seamless steel pipe in Example 1 is greater than the tensile strength of the seamless steel pipe prepared in Comparative Example 4, and the number of head perforations of the plug during the preparation of the seamless steel pipe in Example 1 is greater than the number of head perforations of the plug during the preparation of the seamless steel pipe in Comparative Example 4.

[0150] Further, by comparing Comparative Example 4 with Comparative Example 2 and Comparative Example 3, it can be obtained that the combined use of potassium feldspar powder and silicon carbide in the lubricant can work synergistically to reduce the damage to the plug during the perforation process, thereby extending the service life of the plug. In addition, the tensile strength test data of the seamless pipe of Comparative Example 3 is 441.4MPa, which is lower than the tensile strength test data of the seamless pipe of Comparative Example 4, which is 456.7MPa, indicating that when there is no potassium feldspar powder in the lubricant and silicon carbide is added alone, the tensile strength of the seamless steel pipe obtained will decrease instead of increase.

[0151] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A stainless steel seamless pipe, characterized in that: Calculated by mass percentage, it includes the following components: Cr 14.5-15.5%, C 0.03-0.05%, Ni 7.5-8.5%, Mn 1.6-2.0%, Si 1.2-1.4%, Mo 0.8-1.2%, Cu 0.3-0.5%, Nb 0.25-0.35%, A10.08-0.12%, V 0.02-0.04%, P≤0.03%, S≤0.02%, rare earth element yttrium 0.06-0.10%, and the balance is Fe and other inevitable impurity elements.

2. A method for preparing a stainless steel seamless pipe as claimed in claim 1, characterized in that: The following steps are involved: S1: Vacuum smelting: According to the mass percentage, each raw material is smelted in a vacuum electric furnace to obtain molten steel, which is refined in AOD, LF furnace and VD furnace and then continuously cast or mold cast into steel billets; S2: billet forging: heating the billet prepared in S1 to 1200-1240°C, keeping the temperature for 4-6 hours, and then forging the heated billet into a round billet; S3: Piercing and rolling: a centering hole is punched on the end face of the round billet prepared in S2, and then the round billet is placed at a temperature of 1120-1160°C for 2-4 hours, and then pierced with a plug coated with a lubricant, and naturally cooled after piercing to obtain a hollow tube billet; S4: cold working: placing the hollow tube blank prepared in S3 in a cold rolling unit for cold rolling to obtain a tubular body; S5: Quenching and tempering: heat treatment is performed on the tubular body prepared in S4, the normalizing temperature is 950-1050°C, the tempering temperature is between 600-700°C, the holding time is 1.5-2.5h, and the semi-finished steel pipe is taken out of the furnace and cooled to room temperature; S6: Finishing treatment: The semi-finished steel pipe prepared in S5 is straightened, cut, shot peened, and flaw detected to obtain a stainless steel seamless pipe.

3. The method for preparing a stainless steel seamless pipe according to claim 2, characterized in that: The starting forging temperature of the round billet in S2 is 1050-1150°C, and the final forging temperature is 900-1000°C.

4. The method for preparing a stainless steel seamless pipe according to claim 2, characterized in that: The outer diameter expansion rate of the round steel billet in S3 during piercing is 10%.

5. The method for preparing a stainless steel seamless pipe according to claim 2, characterized in that: The lubricant coating method in S3 is: uniformly coating the lubricant on the surface of the plug, keeping the temperature at 1300-1340° C. for 2-4 hours, and cooling to room temperature.

6. The method for preparing a stainless steel seamless pipe according to claim 2 or 5, characterized in that: The preparation method of the lubricant comprises the following steps: A1: Take the following components by mass percentage: 3-5% water glass, 2-4% dextrin powder, and the balance water, mix them evenly, heat to 90-100°C, stir for 20-40 minutes, and cool to room temperature to obtain a wet component; A2: Take the following components by mass percentage: 30-40% silicon carbide, 15-20% potassium feldspar powder, 8%-12% graphite, and the balance glass powder, mix well, and obtain a lubricating component; A3: The wetting component obtained in A1 and the lubricating component obtained in A2 are mixed evenly, wherein the mass of the wetting component is 5.5-6.5% of the mass of the lubricating component, to obtain a lubricant.

7. The method for preparing a stainless steel seamless pipe according to claim 6, characterized in that: The particle size of silicon carbide in A2 is 1000-2000 mesh, and the particle size of potassium feldspar powder and glass powder is 200-2000 mesh.

8. The method for preparing a stainless steel seamless pipe according to claim 2, characterized in that: During the cold rolling treatment in S4, the cold working deformation of the hollow tube blank is controlled to be 40-50%.