Large-diameter stainless steel pipe and manufacturing process thereof

Abstract

This invention relates to the field of steel pipe technology, specifically to a large-diameter stainless steel pipe and its manufacturing process. The invention involves subjecting raw materials to electric furnace primary refining, ladle refining, and vacuum oxygen blowing decarburization before casting to obtain steel ingots, thus improving the purity and reliability of the molten steel. A tube blank is then produced through heated forging and heated piercing. Finally, the large-diameter stainless steel pipe is manufactured through a combination of heat treatment, pickling, lubrication, heated expansion, and cold drawing processes. This invention also incorporates hyperbranched polysiloxane and graphene into a polyalphaolefin base oil to achieve a synergistic effect, providing better lubrication and producing a lubricant. The manufacturing process of this invention enables large-diameter stainless steel pipes to possess higher purity, better mechanical properties, and better dimensional accuracy.

Description

Technical Field

[0001] This invention relates to the field of steel pipe technology, specifically to a large-diameter stainless steel pipe and its manufacturing process. Background Technology

[0002] With rapid industrialization and urbanization, the demand for pipeline systems is constantly increasing. Traditional pipeline materials such as iron and copper are susceptible to corrosion and rust in certain environments, leading to problems such as pipeline aging and leaks. To solve these problems, stainless steel pipes have become a widely used new type of pipeline material.

[0003] However, most stainless steel pipes on the market currently have relatively small diameters, which cannot meet the needs of some specialized industries for large-diameter pipelines. In large-scale industrial sectors such as petroleum, chemical, and power, pipeline systems capable of handling greater flow rates and pressures are required. Compared to small-diameter pipes, large-diameter stainless steel pipes have a more robust structure, capable of withstanding greater pressure and impact, thus improving the safety of the pipeline system. Furthermore, stainless steel pipes themselves have excellent corrosion resistance, allowing for long-term use in harsh environments without being affected by corrosion or rust. Compared to large-diameter pipes made of other materials, large-diameter stainless steel pipes have lower maintenance costs and a longer lifespan, saving companies on repair and replacement costs.

[0004] Therefore, we propose a large-diameter stainless steel pipe and its manufacturing process. Summary of the Invention

[0005] The purpose of this invention is to provide a large-diameter stainless steel pipe and its manufacturing process to solve the problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A manufacturing process for a large-diameter stainless steel pipe includes the following steps:

[0008] Step S1: The raw materials are successively subjected to electric furnace primary refining, ladle refining and vacuum oxygen blowing decarburization, and then cast into steel ingots;

[0009] Step S2: Heat and forge the steel ingot to obtain a forging billet; heat and pierce the forging billet to obtain a tube blank;

[0010] Step S3: After heat treatment, pickling, and lubrication, the tube blank is heated to expand the hole and cold-drawn in 1-3 passes, and then solution treatment is performed to obtain a large-diameter stainless steel tube.

[0011] Furthermore, the raw materials in step S1 include the following elements by weight percentage: C: 0.04-0.08%, Si: 0.15-0.35%, Mn: 1.0-1.8%, Cr: 17-18%, Ni: 18-25%, Mo: 2.5-2.7%, Ti: 0.12-0.16%, Ir: 0.05-0.15%, Re: 0.16-0.32%, with the balance being iron.

[0012] Furthermore, the process conditions for the initial electric furnace refining in step S1 are as follows: a DC electric arc furnace is used, C is adjusted to 0.04-0.08% before tapping, and the tapping temperature is 1610-1650℃.

[0013] Furthermore, the process conditions for ladle refining in step S1 are: refining temperature 1550-1610℃, refining time 35-45min, and soft blowing 15-20min.

[0014] Furthermore, the process conditions for vacuum oxygen blowing decarburization in step S1 are: vacuum degree 30-60 Pa, maintained for 20-30 min.

[0015] Furthermore, the casting process conditions in step S1 are: superheat 10-20℃, casting machine speed 0.8-1.2m / min.

[0016] Furthermore, the process conditions for heating and forging in step S2 are as follows: heating temperature 1220-1250℃, holding temperature 2-3h, initial forging temperature 1200-1250℃, and final forging temperature 950-1050℃.

[0017] Furthermore, in step S2, before the forging billet undergoes heating and piercing treatment, it is first held at 1080-1160℃ for 1-2 hours, and then cooled to 25-45℃ at a cooling rate of 1.5-3.0℃ / min.

[0018] Furthermore, the process conditions for the heating and piercing treatment in step S2 are as follows: heating to 1155-1185℃ at a heating rate of 2.2-3.2℃ / min, holding at that temperature for 1.5-2.5h, and piercing is performed using a three-roll skew rolling mill.

[0019] Furthermore, in step S2, the outer diameter of the tube blank is 360-640mm, the wall thickness is 80-120mm, and the length is 2400-4200mm.

[0020] Furthermore, the heat treatment process conditions in step S3 are as follows: the tube blank is heated to 840-860℃ at a heating rate of 2.4-3.2℃ / min, then heated to 1150-1220℃ at a heating rate of 4.5-5.0℃ / min, held at that temperature for 1-2 hours, and then cooled to 25-45℃ at a cooling rate of 3.0-4.0℃ / min.

[0021] Furthermore, the pickling process conditions in step S3 are as follows: the tube blank is immersed in a pickling solution at 40-60℃ for 10-30 minutes; the pickling solution formula is: 40-60g / L sulfuric acid, 20-40g / L hydrofluoric acid, 10-30g / L hydrogen peroxide, 10-20g / L ferric chloride hexahydrate, and the balance is pure water.

[0022] Furthermore, the lubrication process conditions in step S3 are as follows: the lubricant is applied to the inner and outer walls of the tube blank by brushing, and the amount of lubricant applied is 100-150 g / m. 2 Dry at 120-150℃ for 30-50 minutes; the preparation process of the lubricant is as follows:

[0023] Step (1): Under nitrogen protection, 2,5-hexanediol and 4-aminobutyltriethoxysilane are mixed evenly, p-toluenesulfonic acid is added, the temperature is raised to 70-80℃, and the mixture is refluxed for 1-2 hours. The temperature is then raised to 100-120℃ and refluxed for 2-3 hours. After rotary evaporation and drying, hyperbranched polysiloxane is obtained.

[0024] Step (2): Mix three-dimensional graphene and deionized water, ultrasonically disperse for 30-40 min, add hyperbranched polysiloxane, stir and disperse for 20-30 min, then add polyα-olefin base oil and deionized water, adjust the pH to 8-9 with NaOH solution, stir and disperse for 10-20 min to obtain the lubricant.

[0025] In the above technical solution, 2,5-hexanediol and 4-aminobutyltriethoxysilane are reacted under acidic conditions to generate hyperbranched polysiloxane. Three-dimensional graphene and hyperbranched polysiloxane are then added to polyα-olefin base oil to obtain a lubricant with excellent lubrication performance.

[0026] Furthermore, in step (1), the mass ratio of 2,5-hexanediol and 4-aminobutyltriethoxysilane is 1:(1-1.2).

[0027] Furthermore, in step (1), the mass of p-toluenesulfonic acid is 0.4-0.6% of the total mass of 2,5-hexanediol and 4-aminobutyltriethoxysilane.

[0028] Furthermore, in step (2), the mass ratio of three-dimensional graphene to deionized water is 1:(20-40).

[0029] Furthermore, in step (2), the mass ratio of three-dimensional graphene to hyperbranched polysiloxane is 1:(20-40).

[0030] Furthermore, in step (2), the mass ratio of poly-α-olefin base oil to deionized water is 1:(14-16).

[0031] Furthermore, in step (2), the amount of three-dimensional graphene used is 0.01-0.04% of the total mass of polyalphaolefin base oil and deionized water.

[0032] Furthermore, the process conditions for heating and expanding the hole in step S3 are: temperature 950-1050℃, and expansion ratio 1.1-1.6.

[0033] Furthermore, the cold drawing process conditions in step S3 are as follows: cold drawing speed 30-50 mm / min, cold drawing diameter reduction 4-8 mm / pass, wall reduction 1.5-3.0 mm / pass, and heat treatment, pickling, and lubrication of the tube blank after each cold drawing.

[0034] Furthermore, the process conditions for the solution treatment in step S3 are: temperature 1050-1150℃, time 1-2h.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] 1. This invention relates to a large-diameter stainless steel pipe and its preparation process. Under acidic conditions, 2,5-hexanediol and 4-aminobutyltriethoxysilane are reacted to generate hyperbranched polysiloxane. Hyperbranched polysiloxane possesses excellent lubricating properties, not only improving the dispersibility of three-dimensional graphene but also reducing friction and wear, thereby increasing the working efficiency and lifespan of mechanical equipment. Furthermore, the dispersion stability of three-dimensional graphene far surpasses that of carbon-based nanomaterials such as graphite, graphene nanosheets, and carbon black, and it exhibits superior lubricating performance. Adding three-dimensional graphene and hyperbranched polysiloxane together to polyα-olefin base oil can achieve a synergistic effect, resulting in a lubricant with excellent lubricating properties. This lubricant not only provides better anti-wear effects and reduces drawing energy consumption but also increases the tensile strength of steel and protects the pipe blank surface from damage, thus achieving energy saving, emission reduction, and cost savings.

[0037] 2. The present invention discloses a large-diameter stainless steel pipe and its manufacturing process. The raw materials are initially refined in an electric furnace to remove impurities and undesirable elements, improving the purity and quality of the molten steel. The refined molten steel is then transferred to a ladle for further refining, with the furnace temperature adjusted to further improve its purity and quality. Vacuum oxygen blowing decarburization is then performed to remove carbon elements from the molten steel, improving its purity and reliability. The molten steel is subsequently cast into ingots. A tube blank is obtained through heated forging and heated piercing. The tube blank undergoes heat treatment, altering the steel's microstructure through heating and cooling processes to improve its mechanical properties and corrosion resistance. The heat-treated tube blank is then pickled to remove surface oxides and contaminants. The pickled tube blank undergoes lubrication treatment to reduce friction and wear, improving processing efficiency and quality. The lubricated tube blank undergoes multiple passes of heated expansion and cold drawing, gradually thinning and lengthening it through stretching and extrusion, improving its mechanical properties and dimensional accuracy. Finally, a solution treatment is performed to obtain the large-diameter stainless steel pipe. By combining the above processes, this invention can produce high-quality large-diameter stainless steel pipes, meeting the industrial sector's requirements for high purity, excellent mechanical properties, and precise dimensions. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0039] In this embodiment, Si: ferrosilicon alloy, grade FeSi75A, Si content 74-80%, sourced from Henan Huijin Metallurgical Technology Co., Ltd.; Mn: ferromanganese alloy, grade FeMn68C7.0, Mn content 65-72%, sourced from Henan Huijin Metallurgical Technology Co., Ltd.; Cr, Ni: iron-nickel-chromium alloy, grade NS113, Cr content 24-26%, Ni content 34.0-37.0%, sourced from Shanghai Yili Metal Materials Co., Ltd.; Mo: iron-molybdenum alloy, grade FeMo60, Mo content 60%, Fe content 40%, sourced from Beijing October New Materials Technology Co., Ltd.; Ti: Titanium-iron alloy, grade FeTi30-A, titanium content 20%-27%, sourced from Shenyang Jiabei Trading Co., Ltd.; Ir: iridium tube, content ≥99.95%, sourced from Zhongrui Metal Technology (Wuxi) Co., Ltd.; Re: rhenium bar, content ≥99.95%, sourced from Zhuzhou Kaitai Industrial Co., Ltd.; Iron: cast iron, grade Z14, iron content 95%, sourced from Anyang Jinyao Metallurgy Co., Ltd.; Three-dimensional graphene: 3-4 layers, thickness 1.3-1.4nm, sourced from Sichuan Kenye Technology Development Co., Ltd.; Polyalphaolefin base oil: model PAO20, sourced from Beijing Xirunte Trading Co., Ltd.

[0040] Example 1: A manufacturing process for a large-diameter stainless steel pipe, comprising the following steps:

[0041] Step S1: The raw materials are sequentially subjected to primary refining in an electric furnace (using a DC electric arc furnace, adjusting C to 0.04% before tapping, and tapping temperature of 1610℃), ladle refining (refining temperature of 1550℃, refining time of 35min, soft blowing for 15min), and vacuum oxygen blowing decarburization (vacuum degree of 30Pa, held for 20min), and then cast (superheat of 10℃, casting machine speed of 0.8m / min) to obtain steel ingots;

[0042] Step S2: The steel ingot is heated and forged (heating temperature 1220℃, holding temperature 2h, initial forging temperature 1200℃, final forging temperature 950℃) to obtain a forging billet; the forging billet is heated and pierced (heated to 1155℃ at a heating rate of 2.2℃ / min, held for 1.5h, and pierced by three-roll skew rolling) to obtain a tube billet;

[0043] Step S3: The tube blank is subjected to heat treatment in sequence (heating the tube blank to 840℃ at a heating rate of 2.4℃ / min, then to 1150℃ at a heating rate of 4.5℃ / min, holding at that temperature for 1 hour, and then cooling to 25℃ at a cooling rate of 3.0℃ / min), pickling (immersing the tube blank in a 40℃ pickling solution for 10 minutes; the pickling solution formula is: 40g / L sulfuric acid, 20g / L hydrofluoric acid, 10g / L hydrogen peroxide, 10g / L ferric chloride hexahydrate, with the remainder being pure water), and lubrication (applying lubricant to the inner and outer walls of the tube blank by brushing, with an application amount of 100g / m). 2 The tube blank is then heated and expanded (temperature 950℃, expansion ratio 1.1, expansion speed 35mm / min) and then cold-drawn once (cold drawing speed 30mm / min, cold drawing diameter reduction 4mm / pass, wall reduction 1.5-3.0mm / pass, after each cold drawing the tube blank is heat-treated, pickled and lubricated in sequence), and then solution treated (temperature 1050℃, time 1h) to obtain a large-diameter stainless steel tube;

[0044] The raw materials consist of the following elements by weight percentage: C: 0.04%, Si: 0.15%, Mn: 1.0%, Cr: 17%, Ni: 18%, Mo: 2.5%, Ti: 0.12%, Ir: 0.05%, Re: 0.16%, with the balance being iron;

[0045] The preparation process of the lubricant is as follows:

[0046] Step (1): Under nitrogen protection, 2 kg of 2,5-hexanediol and 2 kg of 4-aminobutyltriethoxysilane were mixed evenly, 0.016 kg of p-toluenesulfonic acid was added, the temperature was raised to 70°C, and the mixture was refluxed for 1 h. The temperature was then raised to 100°C and refluxed for 2 h. After rotary evaporation and drying, hyperbranched polysiloxane was obtained.

[0047] Step (2): Mix 0.075 kg of three-dimensional graphene and 1.5 kg of deionized water, ultrasonically disperse for 30 min, add 1.5 kg of hyperbranched polysiloxane, stir and disperse for 20 min, then add 50 kg of polyα-olefin base oil and 700 kg of deionized water, adjust the pH to 8 with NaOH solution, stir and disperse for 10 min to obtain the lubricant.

[0048] Example 2: A manufacturing process for a large-diameter stainless steel pipe, comprising the following steps:

[0049] Step S1: The raw materials are sequentially subjected to primary refining in an electric furnace (using a DC electric arc furnace, adjusting C to 0.05% before tapping, and tapping temperature of 1630℃), ladle refining (refining temperature of 1580℃, refining time of 40min, soft blowing for 18min), and vacuum oxygen blowing decarburization (vacuum degree of 40Pa, held for 25min), and then cast (superheat of 15℃, casting machine speed of 1.0m / min) to obtain steel ingots;

[0050] Step S2: The steel ingot is heated and forged (heating temperature 1230℃, holding temperature 2.5h, initial forging temperature 1220℃, final forging temperature 1000℃) to obtain a forging billet; the forging billet is heated and pierced (heated to 1170℃ at a heating rate of 2.8℃ / min, held for 2h, and pierced by three-roll skew rolling) to obtain a tube billet;

[0051] Step S3: The tube blank is subjected to heat treatment in sequence (heating the tube blank to 850℃ at a heating rate of 2.8℃ / min, then to 1200℃ at a heating rate of 4.8℃ / min, holding at that temperature for 1.5h, and then cooling to 30℃ at a cooling rate of 3.5℃ / min), pickling (immersing the tube blank in a 50℃ pickling solution for 20min; the pickling solution formula is: 50g / L sulfuric acid, 30g / L hydrofluoric acid, 20g / L hydrogen peroxide, 15g / L ferric chloride hexahydrate, with the remainder being pure water), and lubrication (applying lubricant to the inner and outer walls of the tube blank by brushing, with an application amount of 125g / m). 2 The tube blank is then heated and expanded (temperature 1000℃, expansion ratio 1.4, expansion speed 45mm / min) and then cold-drawn in two passes (cold drawing speed 40mm / min, cold drawing diameter reduction 6mm / pass, wall reduction 2mm / pass, after each cold drawing, the tube blank is heat-treated, pickled and lubricated in sequence), and then solution treated (temperature 1100℃, time 1.5h) to obtain a large-diameter stainless steel tube.

[0052] The raw materials consist of the following elements by weight percentage: C: 0.06%, Si: 0.25%, Mn: 1.4%, Cr: 17.5%, Ni: 20%, Mo: 2.6%, Ti: 0.14%, Ir: 0.10%, Re: 0.24%, with the balance being iron;

[0053] The preparation process of the lubricant is as follows:

[0054] Step (1): Under nitrogen protection, 5 kg of 2,5-hexanediol and 5.5 kg of 4-aminobutyltriethoxysilane were mixed evenly, and 0.525 kg of p-toluenesulfonic acid was added. The mixture was heated to 75°C and refluxed for 1.5 h. The mixture was then heated to 110°C and refluxed for 2.5 h. After rotary evaporation and drying, hyperbranched polysiloxane was obtained.

[0055] Step (2): Mix 0.16 kg of three-dimensional graphene and 4.8 kg of deionized water, ultrasonically disperse for 35 min, add 4.8 kg of hyperbranched polysiloxane, stir and disperse for 25 min, then add 50 kg of polyα-olefin base oil and 750 kg of deionized water, adjust the pH to 8.5 with NaOH solution, stir and disperse for 15 min to obtain the lubricant.

[0056] Example 3: A manufacturing process for a large-diameter stainless steel pipe, comprising the following steps:

[0057] Step S1: The raw materials are sequentially subjected to primary refining in an electric furnace (using a DC electric arc furnace, adjusting C to 0.08% before tapping, and tapping temperature of 1650℃), ladle refining (refining temperature of 1610℃, refining time of 45min, soft blowing for 20min), and vacuum oxygen blowing decarburization (vacuum degree of 60Pa, held for 30min), and then cast (superheat of 20℃, casting machine speed of 1.2m / min) to obtain steel ingots;

[0058] Step S2: The steel ingot is heated and forged (heating temperature 1250℃, holding temperature 3h, initial forging temperature 1250℃, final forging temperature 1050℃) to obtain a forging billet; the forging billet is heated and pierced (heated to 1185℃ at a heating rate of 3.2℃ / min, held for 2.5h, and pierced by three-roll skew rolling) to obtain a tube billet;

[0059] Step S3: The tube blank is subjected to heat treatment in sequence (heating the tube blank to 860℃ at a heating rate of 3.2℃ / min, then to 1220℃ at a heating rate of 5.0℃ / min, holding for 2 hours, and then cooling to 45℃ at a cooling rate of 4.0℃ / min), pickling (immersing the tube blank in a 60℃ pickling solution for 30 minutes; the pickling solution formula is: 60g / L sulfuric acid, 40g / L hydrofluoric acid, 30g / L hydrogen peroxide, 20g / L ferric chloride hexahydrate, with the remainder being pure water), and lubrication (applying lubricant to the inner and outer walls of the tube blank by brushing, with an application amount of 150g / m). 2 The tube blank is then heated and expanded (temperature 1050℃, expansion ratio 1.6, expansion speed 55mm / min) and then cold-drawn in 3 passes (cold drawing speed 50mm / min, cold drawing diameter reduction 8mm / pass, wall reduction 3.0mm / pass, heat treatment is performed on the tube blank after each cold drawing, and pickling and lubrication are performed in sequence after each heat treatment), and then solution treatment is performed (temperature 1150℃, time 2h) to obtain a large-diameter stainless steel tube.

[0060] The raw materials consist of the following elements by weight percentage: C: 0.08%, Si: 0.35%, Mn: 1.8%, Cr: 18%, Ni: 25%, Mo: 2.7%, Ti: 0.16%, Ir: 0.15%, Re: 0.32%, with the balance being iron.

[0061] The preparation process of the lubricant is as follows:

[0062] Step (1): Under nitrogen protection, 2,5-hexanediol and 4-aminobutyltriethoxysilane were mixed evenly, p-toluenesulfonic acid was added, the temperature was raised to 80°C, and the mixture was refluxed for 2 hours. The temperature was then raised to 120°C and refluxed for 3 hours. After rotary evaporation and drying, hyperbranched polysiloxane was obtained.

[0063] Step (2): Mix three-dimensional graphene and deionized water, ultrasonically disperse for 40 min, add hyperbranched polysiloxane, stir and disperse for 30 min, then add 50 kg of polyα-olefin base oil and 800 kg of deionized water, adjust the pH to 9 with NaOH solution, stir and disperse for 20 min to obtain the lubricant.

[0064] Comparative Example 1: Compared with Example 1, Comparative Example 1 does not include the preparation process of the lubricant. In step S3, the lubricant is replaced with the same mass of ordinary lubricant (brand name L-AN32, sourced from Henan Runxing Lubricating Oil Co., Ltd.). Other steps and processes are the same as in Example 1.

[0065] Comparative Example 2: Compared with Example 1, Comparative Example 2 replaced the hyperbranched polysiloxane with the same mass of oleic acid (from Nanjing Sifanke Chemical Co., Ltd.), and the other steps and processes were the same as in Example 1.

[0066] Comparative Example 3: A manufacturing process for a large-diameter stainless steel pipe, comprising the following steps:

[0067] The preparation process of the lubricant is as follows:

[0068] Step (1): Under nitrogen protection, 5 kg of 2,5-hexanediol and 15 kg of 4-aminobutyltriethoxysilane were mixed evenly, 0.525 kg of p-toluenesulfonic acid was added, the temperature was raised to 75°C, and the mixture was refluxed for 1.5 h. The temperature was then raised to 110°C and refluxed for 2.5 h. After rotary evaporation and drying, hyperbranched polysiloxane was obtained.

[0069] Step (2): Mix 0.16 kg of three-dimensional graphene and 4.8 kg of deionized water, ultrasonically disperse for 35 min, add 4.8 kg of hyperbranched polysiloxane, stir and disperse for 25 min, then add 50 kg of polyα-olefin base oil and 750 kg of deionized water, adjust the pH to 8.5 with NaOH solution, stir and disperse for 15 min to obtain the lubricant;

[0070] Compared with Comparative Example 2, in step (1) of Comparative Example 3, the mass ratio of 2,5-hexanediol and 4-aminobutyltriethoxysilane is 1:3; the other steps are the same as in Example 2.

[0071] Comparative Example 4: A manufacturing process for a large-diameter stainless steel pipe, comprising the following steps:

[0072] Compared with Example 2, in step S3 of Comparative Example 4, the tube blank is not subjected to heat treatment, pickling, or lubrication after each cold drawing, while the other steps are the same as in Example 2.

[0073] experiment

[0074] Large-diameter stainless steel pipes obtained in Examples 1-3 and Comparative Examples 1-4 were used to prepare samples, and their properties were tested and the test results were recorded:

[0075] The tensile strength was determined according to GB / T 228.1-2010 "Metallic materials, tensile testing - Part 1: Test method at room temperature". The experimental procedure was as follows: Take a round bar with a diameter of 12 mm and a length of 60 mm from the middle part of the large-diameter stainless steel pipe obtained in Examples 1-3 and Comparative Examples 1-4, along the cross-section of the steel pipe near the outer wall. Clamp the specimen on the testing machine, start the tensile testing machine, and gradually increase the tensile load at a loading rate of 1 mm / s until the specimen breaks. Record the data.

[0076] The surface hardness was tested using a Brinell hardness tester. The experimental procedure was as follows: eight points were taken at intervals of 10 mm from the head, middle and tail of a large-diameter stainless steel pipe with an outer diameter of 550 mm and a wall thickness of 45 mm. The hardness was tested, the time was recorded, and the average value was taken.

[0077] Tribological test: A reciprocating ball-and-disc mode was used. The test duration was 1 hour, the amplitude was 6 mm, the frequency was 10 Hz, the load was 50 N, the steel block used was 316ASS, the length was 100 mm × 100 mm, and the steel ball used was GCrl5 standard steel ball with a hardness of 59 HRC and a diameter of 6 mm. Tribological tests were performed on the lubricants in Examples 1-3 and Comparative Examples 1-4. Each test was repeated three times. The wear rate of the steel block was obtained by calculating the ratio of wear volume (V) to load (F) and total stroke (S).

[0078] Test Results

[0079]

[0080]

[0081] Based on the data in the table above, the following conclusions can be clearly drawn:

[0082] 1. Compared with the products of Comparative Example 1, the tensile strength and hardness of the product obtained by Comparative Example 1 decreased, and the anti-wear performance of the lubricant decreased. It can be seen that compared with ordinary lubricants, the lubricant prepared by the present invention can improve the tensile strength of the material and help reduce the drawing energy consumption.

[0083] 2. Compared with Examples 1-3, the anti-wear properties of the lubricants prepared in Comparative Examples 2 and 3 decreased, indicating that the hyperbranched polysiloxane prepared in this invention has better dispersibility and lubrication properties than oleic acid, thereby improving the anti-wear properties of the lubricant and reducing wear. At the same time, the performance of the lubricant prepared in this invention is affected by the ratio of its reagents. By selecting the component ratio within the range described above, a lubricant with excellent lubrication properties can be prepared.

[0084] 3. Compared with Examples 1-3, the tensile strength and hardness of the product obtained in Comparative Example 4 have decreased. It can be seen that heat treatment, pickling and lubrication of the tube blank after cold drawing can improve the mechanical properties of the material and increase the tensile strength and hardness.

[0085] 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 a process method article or apparatus.

[0086] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A manufacturing process for large-diameter stainless steel pipes, characterized in that: Includes the following steps: Step S1: The raw materials are successively subjected to electric furnace primary refining, ladle refining and vacuum oxygen blowing decarburization, and then cast into steel ingots; Step S2: Heat and forge the steel ingot to obtain a forging billet; heat and pierce the forging billet to obtain a tube blank; Step S3: After heat treatment, pickling, and lubrication, the tube blank is heated to expand the hole and cold-drawn in 1-3 passes, and then solution treatment is performed to obtain a large-diameter stainless steel tube. The lubrication process conditions are as follows: apply the lubricant to the inner and outer walls of the tube blank by brushing, with a lubricant application rate of 100-150 g / m. 2 Dry at 120-150℃ for 30-50 minutes; the preparation process of the lubricant is as follows: Step (1): Under nitrogen protection, 2,5-hexanediol and 4-aminobutyltriethoxysilane are mixed evenly with a mass ratio of 1:(1-1.2). p-Toluenesulfonic acid is added, the temperature is raised to 70-80℃, and the mixture is refluxed for 1-2 hours. The temperature is then raised to 100-120℃ and refluxed for 2-3 hours. After rotary evaporation and drying, hyperbranched polysiloxane is obtained. Step (2): Mix three-dimensional graphene and deionized water, ultrasonically disperse for 30-40 min, add hyperbranched polysiloxane, stir and disperse for 20-30 min, then add polyα-olefin base oil and deionized water, adjust the pH to 8-9 with NaOH solution, stir and disperse for 10-20 min to obtain the lubricant.

2. The manufacturing process of a large-diameter stainless steel pipe according to claim 1, characterized in that: The raw materials in step S1 include the following elements by weight percentage: C: 0.04-0.08%, Si: 0.15-0.35%, Mn: 1.0-1.8%, Cr: 17-18%, Ni: 18-25%, Mo: 2.5-2.7%, Ti: 0.12-0.16%, Ir: 0.05-0.15%, Re: 0.16-0.32%, with the balance being iron.

3. The manufacturing process of a large-diameter stainless steel pipe according to claim 1, characterized in that: The process conditions for ladle refining in step S1 are: refining temperature 1550-1610℃, refining time 35-45min, and soft blowing 15-20min.

4. The manufacturing process of a large-diameter stainless steel pipe according to claim 1, characterized in that: The process conditions for heating and forging in step S2 are as follows: heating temperature 1220-1250℃, holding temperature 2-3h, initial forging temperature 1200-1250℃, and final forging temperature 950-1050℃.

5. The manufacturing process of a large-diameter stainless steel pipe according to claim 1, characterized in that: The process conditions for the heating and piercing treatment in step S2 are as follows: heating to 1155-1185℃ at a heating rate of 2.2-3.2℃ / min, holding at that temperature for 1.5-2.5h, and piercing is performed using a three-roll skew rolling process.

6. The manufacturing process of a large-diameter stainless steel pipe according to claim 1, characterized in that: The heat treatment process conditions in step S3 are as follows: the tube blank is heated to 840-860℃ at a heating rate of 2.4-3.2℃ / min, then heated to 1150-1220℃ at a heating rate of 4.5-5.0℃ / min, held at that temperature for 1-2 hours, and then cooled to 25-45℃ at a cooling rate of 3.0-4.0℃ / min.

7. The manufacturing process of a large-diameter stainless steel pipe according to claim 1, characterized in that: The cold drawing process conditions in step S3 are as follows: cold drawing speed 30-50 mm / min, cold drawing diameter reduction 4-8 mm / pass, wall reduction 1.5-3.0 mm / pass, and after each cold drawing, the tube blank is subjected to heat treatment, pickling and lubrication in sequence.

8. A large-diameter stainless steel pipe prepared according to any one of claims 1-7.

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