Low-temperature-resistant cold-drawn section steel and preparation method thereof

Abstract

The invention relates to the technical field of profile steel, in particular to low-temperature-resistant cold-drawn profile steel and a preparation method thereof.The preparation method comprises the following steps that a casting blank is stacked and cooled to the room temperature, a forced air cooling technology is adopted in the cooling process so as to accelerate cooling, refine grains and heat the steel blank, the heating temperature ranges from 1150 DEG C to 1250 DEG C, the heating time ranges from 24 hours, and the casting blank is cooled to the room temperature; a multi-section heating technology of a soaking pit furnace is adopted in the heating process to ensure that the steel billet is uniformly heated; the low-temperature-resistant cold-drawn section steel has the beneficial effects that by adding specific alloy elements and optimizing smelting and cold drawing processes, the toughness and plasticity of the low-temperature-resistant cold-drawn section steel at low temperature are remarkably improved, heavy load and impact in an extremely low-temperature environment can be borne, and brittle fracture is effectively avoided; while the low-temperature resistance is improved, the low-temperature-resistant cold-drawn section steel still keeps high strength and hardness, and can meet the use requirements under various complex working conditions.

Description

Technical Field

[0001] The present invention relates to the field of profiled steel, and particularly to a low-temperature resistant cold-drawn profiled steel and a preparation method thereof. Background Art

[0002] Cold-drawn profiled steel is a kind of steel produced by the cold-drawing process, and its preparation process involves multiple links and complex process technologies. In the traditional steel preparation process, methods such as hot rolling and forging are usually used, but these methods have problems such as high energy consumption, low material utilization rate, and limited product performance. With the continuous development of industrial technology, the cold-drawing process has gradually become one of the important technologies in the field of steel preparation because it can significantly improve the strength and hardness of steel while reducing energy consumption and material loss.

[0003] The main principle of the cold-drawing process is to apply a tensile force exceeding its yield point to the steel at normal temperature through mechanical force, causing it to undergo plastic deformation. During this process, the density, strength, and corrosion resistance of the steel will all be improved. At the same time, the cold-drawing process can also refine the grains and optimize the organizational structure, further enhancing the mechanical properties of the steel.

[0004] In the preparation process of cold-drawn profiled steel, first, high-quality steel needs to be selected as the raw material, which is the basis for ensuring the quality of the final product. Then, necessary pretreatment is carried out on the raw material, such as removing impurities such as scale and oil on the surface to ensure the cleanliness and flatness of the steel surface. Next, a special cold-drawing machine is used to stretch the steel to make its shape and size meet the requirements. During the stretching process, the magnitude of the tensile force and the stretching speed need to be strictly controlled to ensure that the plastic deformation of the steel is within a controllable range. After stretching, subsequent treatments such as annealing, straightening, and cutting are also required to improve the straightness and dimensional accuracy of the steel and meet different usage requirements.

[0005] As a kind of high-performance steel produced by the cold-drawing process, cold-drawn profiled steel exhibits excellent mechanical properties and material utilization rate under normal environments. However, with the continuous expansion of industrial applications, especially the increasing application requirements in extreme low-temperature environments, traditional cold-drawn profiled steel often has deficiencies in low-temperature resistance. Under low-temperature conditions, the toughness and plasticity of steel will significantly decrease, easily leading to brittle fracture, thus limiting its applications in low-temperature environments such as polar exploration, deep-sea exploration, and low-temperature storage and transportation. Summary of the Invention

[0006] The purpose of the present invention is to provide a low-temperature resistant cold-drawn profiled steel and a preparation method thereof to solve the problems raised in the above background art.

[0007] To achieve the above object, the present invention provides the following technical solution: a low-temperature resistant cold-drawn steel section, the components and weight percentages of the cold-drawn steel section are: C: 0.15%-0.20%, Si: 0.3%-0.45%, Mn: 1.4%-1.5%, P≤0.01%, S≤0.003%, Ti:

[0008] 0.04%-0.045%, Cu≤0.015%, V: 0.04%-0.045%, Ni: 6%-8%, Als: 0.02%-0.03%, Ca: 0.002%-0.006%, B: 0.0015%-0.0025%, Mo:

[0009] 0.1%-0.3%, the balance being Fe and unavoidable impurities, the total elongation Agt at maximum force of the cold-drawn steel section at -196°C is ≥8%, and the Charpy V-notch impact energy absorption KV2 is ≥30 J.

[0010] Preferably, the cold-drawn steel section further includes trace amounts of Nb, and its weight percentage is

[0011] 0.01%-0.02%, and trace amounts of Zr, and its weight percentage is 0.005%-0.015%.

[0012] A preparation method of a low-temperature resistant cold-drawn steel section, the method includes the following steps:

[0013] (a) Conventional smelting and continuous casting of billets, and electromagnetic stirring technology is adopted during the smelting process to improve the uniformity of the molten steel and reduce inclusions;

[0014] (b) Stacking and cooling the continuous casting billets to room temperature, and forced air cooling technology is adopted during the cooling process to accelerate cooling and refine the grains;

[0015] (c) Heating the steel billets, the heating temperature is 1150°C - 1250°C, the heating time is 24 hours, and multi-stage heating technology of soaking pits is adopted during the heating process to ensure uniform heating of the steel billets;

[0016] (d) Rough rolling the heated steel billets, and the reduction ratio of rough rolling is 10%-20%;

[0017] (e) Finish rolling the rough-rolled steel billets, the reduction ratio of finish rolling is 20%-30%, and the thickness of the finish-rolled steel is 1.1 - 1.3 times the finished product thickness;

[0018] (f) Online quenching treatment of the finish-rolled steel billets to improve the hardness and strength of the steel, the quenching medium is an aqueous solution of polyethylene glycol, and the quenching temperature is 850°C - 900°C;

[0019] (g) Perform self-tempering treatment on the quenched steel to eliminate quenching stress and improve toughness. The self-tempering temperature is 300°C - 400°C, and the holding time is 1 - 2 hours;

[0020] (h) Air-cool the steel to room temperature and keep it for use.

[0021] Preferably, after step (h), there is also a step of pickling the steel to remove the surface oxide layer. Electrolytic pickling technology is used for pickling to improve pickling efficiency and surface quality.

[0022] Preferably, after the pickling step, there is also a phosphating treatment on the steel to form a dense phosphate protective film on the steel surface and improve the corrosion resistance of the steel. The phosphating solution used for phosphating treatment includes the following components in parts by weight: zinc dihydrogen phosphate 60g / L, zinc nitrate 80g / L, sodium permanganate 50g / L, sodium chlorate 1g / L, organic accelerator 4.5g / L, where the weight ratio of sodium m-nitrobenzenesulfonate to hydroxylamine sulfate is 1:2, citric acid 2g / L, sodium fluoride 1.5g / L, OP-10 emulsifier 2ml / L, and the balance is water. An appropriate amount of nano-silica particles is added to the phosphating solution to improve the compactness and corrosion resistance of the phosphating film.

[0023] Preferably, after the phosphating treatment, there is also an ultrasonic cleaning step for the steel to remove the tiny impurities and bubbles generated during the phosphating process. The cleaning frequency is 20kHz - 40kHz, and the cleaning time is 5 - 10 minutes.

[0024] Preferably, after the ultrasonic cleaning, there are also steps of drawing, annealing, and straightening the steel. The annealing temperature is 600°C - 700°C, and the holding time is 2 - 4 hours. After annealing, a rapid cooling technology is adopted to refine the grains after annealing and improve the strength and toughness of the steel. The cooling medium is nitrogen, and the cooling rate is 30°C / s - 50°C / s.

[0025] Preferably, after the straightening step, there is also a surface coating treatment on the steel to improve the corrosion resistance and wear resistance of the steel. The coating material is an epoxy resin-based anti-corrosion coating, and the coating thickness is 50 - 100μm.

[0026] Preferably, after the coating treatment, there is also a curing treatment on the steel to ensure the firmness and durability of the coating. The curing temperature is 80°C - 100°C, and the curing time is 1 - 2 hours.

[0027] Preferably, during the preparation process, an on-line detection technology is also adopted to monitor the quality of the steel and the production process parameters in real time to ensure product quality, including but not limited to ultrasonic flaw detection, eddy current flaw detection, and magnetic particle flaw detection.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] The low-temperature resistant cold-drawn steel and its preparation method proposed by the present invention significantly improve the toughness and plasticity of the low-temperature resistant cold-drawn steel at low temperatures by adding specific alloying elements and optimizing the smelting and cold-drawing processes. It can withstand heavy loads and impacts in extremely low-temperature environments, effectively avoiding brittle fracture. While improving the low-temperature resistance performance, the low-temperature resistant cold-drawn steel still maintains high strength and hardness, and can meet the usage requirements under various complex working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flow chart of the method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] In order to clearly and completely describe the objectives, technical solutions of the present invention, and make the advantages more clearly understood, the following further details the embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are part of the embodiments of the present invention, rather than all of the embodiments, and are only used to explain the embodiments of the present invention, not to limit the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0032] Example 1, Preparation of Low-Temperature Resistant Cold-Drawn Steel

[0033] Components and weight percentages:

[0034] C: 0.18%

[0035] Si: 0.4%

[0036] Mn: 1.45%

[0037] P: 0.008%

[0038] S: 0.002%

[0039] Ti: 0.042%

[0040] Cu: 0.01%

[0041] V: 0.042%

[0042] Ni: 7%

[0043] Als: 0.025%

[0044] Ca: 0.004%

[0045] B: 0.002%

[0046] Mo: 0.2%

[0047] W: 0.07%

[0048] The balance is Fe and unavoidable impurities

[0049] Preparation method:

[0050] Smelting and continuous casting billet: Smelt using an electric arc furnace and add alloying elements in the above proportions. During the smelting process, electromagnetic stirring technology and ultrasonic refining technology are adopted to ensure the uniformity of the molten steel and reduce inclusions. Cast into billets and stack them for cooling to room temperature.

[0051] Heating and rolling: Put the continuous casting billets into a soaking furnace, heat them to 1200 °C, with a heating time of 3 hours, and adopt multi-stage heating technology and high-temperature homogenization treatment. Carry out rough rolling with a reduction ratio of 15%, and adopt dynamic recrystallization control technology during rough rolling. Carry out finish rolling with a reduction ratio of 25%, and the thickness of the steel after finish rolling is 1.2 times the finished product thickness. Adopt low-temperature large reduction technology during finish rolling.

[0052] Quenching and tempering: Carry out on-line quenching treatment on the steel after finish rolling. The quenching medium is an aqueous solution of polyethylene glycol, and the quenching temperature is 880 °C. After quenching, adopt high-pressure spray quenching technology to ensure uniform quenching. Carry out self-tempering treatment, with a tempering temperature of 350 °C and a holding time of 1.5 hours, and adopt intelligent temperature control technology.

[0053] Subsequent treatment: Air-cool the steel to room temperature and adopt nitrogen protection technology to prevent oxidation. Carry out electrolytic pickling and adopt an intelligent pickling control system to ensure pickling quality. Carry out phosphating treatment, add nano-silica particles and nano-cerium oxide particles to the phosphating solution to improve the compactness and corrosion resistance of the phosphating film. Carry out ultrasonic cleaning with a cleaning frequency of 30 kHz and a cleaning time of 7 minutes, and adopt multi-frequency ultrasonic cleaning technology. Carry out drawing, annealing and straightening. The annealing temperature is 650 °C and the holding time is 3 hours. Adopt rapid cooling technology after annealing.

[0054] Final treatment: Carry out surface coating treatment on the steel. The coating material is an epoxy resin-based anti-corrosion coating, with a coating thickness of 75 μm, and adopt high-pressure airless spraying technology. Carry out curing treatment, with a curing temperature of 90 °C and a curing time of 1.5 hours, and adopt far-infrared radiation heating technology.

[0055] Example 2: Based on Example 1, some parameters and components are adjusted

[0056] Components and weight percentages:

[0057] C: 0.16%

[0058] Si: 0.35%

[0059] Mn: 1.5%

[0060] P: 0.005%

[0061] S: 0.001%

[0062] Ti: 0.04%

[0063] Cu: 0.005%

[0064] V: 0.045%

[0065] Ni: 6.5%

[0066] Als: 0.03%

[0067] Ca: 0.003%

[0068] B: 0.0018%

[0069] Mo: 0.15%

[0070] W: 0.05%

[0071] The balance is Fe and unavoidable impurities

[0072] Preparation method (partial steps are the same as those in Example 1, only the differences are listed):

[0073] Smelting and continuous casting billet: After casting, a combined cooling technology of forced air cooling and spray cooling is adopted

[0074] Heating and rolling: Heat to 1180 °C, and the heating time is 2.5 hours. The rough rolling reduction rate is 12%, and the finish rolling reduction rate is 28%

[0075] Quenching and tempering: The quenching temperature is 870 °C. The tempering temperature is 320 °C, and the holding time is 1.2 hours

[0076] Subsequent treatment: After pickling, phosphating treatment is adopted, and the content of nanoparticles in the phosphating solution is slightly adjusted. The ultrasonic cleaning frequency is 25 kHz, and the cleaning time is 8 minutes. The annealing temperature is 620 °C, and the holding time is 3.5 hours

[0077] Final treatment: The coating thickness is 60 μm. The curing temperature is 85 °C, and the curing time is 1.8 hours

[0078] Example 3, on the basis of Example 1, further adjust the components and parameters

[0079] Components and weight percentages:

[0080] C: 0.2%

[0081] Si: 0.45%

[0082] Mn: 1.4%

[0083] P: 0.009%

[0084] S: 0.003%

[0085] Ti: 0.045%

[0086] Cu: 0.012%

[0087] V: 0.04%

[0088] Ni: 7.5%

[0089] Als: 0.02%

[0090] Ca: 0.006%

[0091] B: 0.0022%

[0092] Mo: 0.25%

[0093] W: 0.09%

[0094] The balance is Fe and unavoidable impurities

[0095] Preparation method (partial steps are the same as those in Examples 1 and 2, only the differences are listed):

[0096] Smelting and continuous casting: A trace amount of rare earth element La with a weight percentage of 0.003% is added during the smelting process.

[0097] Heating and rolling: Heat to 1220 °C, and the heating time is 3.5 hours. The reduction ratio of rough rolling is 18%, and the reduction ratio of finish rolling is 22%.

[0098] Quenching and tempering: The quenching temperature is 890 °C. The tempering temperature is 370 °C, and the holding time is 1 hour.

[0099] Subsequent treatment: The steel after phosphating treatment is subjected to more stringent ultrasonic cleaning at a frequency of 40 kHz for 5 minutes. The annealing temperature is 680 °C, and the holding time is 2.5 hours.

[0100] Final treatment: The coating thickness is 85 μm. The curing temperature is 95 °C, and the curing time is 1 hour.

[0101] Example 4, on the basis of Example 1, comprehensively adjusted, and more advanced preparation techniques are adopted

[0102] Components and weight percentages:

[0103] C: 0.17%

[0104] Si: 0.4%

[0105] Mn: 1.48%

[0106] P: 0.007%

[0107] S: 0.0025%

[0108] Ti: 0.043%

[0109] Cu: 0.01%

[0110] V: 0.043%

[0111] Ni: 7.2%

[0112] Als: 0.028%

[0113] Ca: 0.005%

[0114] B: 0.002%

[0115] Mo: 0.2%

[0116] W: 0.08%

[0117] Trace Nb: 0.015%

[0118] Trace Zr: 0.01%

[0119] Trace rare earth element Ce: 0.002%

[0120] The balance is Fe and unavoidable impurities

[0121] Preparation method (combining the advantages of Examples 1, 2, and 3 in some steps and introducing new technologies):

[0122] Smelting and continuous casting: Use an electric arc furnace for smelting, add all alloying elements, and adopt electromagnetic stirring, ultrasonic refining, and nitrogen protection technologies. After casting, adopt composite cooling technology.

[0123] Heating and rolling: Heat to 1210°C, with a heating time of 3 hours, and adopt multi-stage heating and high-temperature homogenization treatment. The reduction ratio of rough rolling is 16%, and adopt dynamic recrystallization control technology. The reduction ratio of finish rolling is 26%, and adopt low-temperature large reduction technology.

[0124] Quenching and tempering: Online quenching treatment, with the quenching medium being an aqueous solution of polyethylene glycol and the quenching temperature being 885°C. Adopt high-pressure spray quenching technology and intelligent temperature control technology. The tempering temperature is 360°C, and the holding time is 1.3 hours.

[0125] Subsequent processing: Electrolytic pickling, using an intelligent pickling control system. Phosphating treatment, adding nano-silica particles and nano-cerium oxide particles to the phosphating solution to optimize the performance of the phosphating film. Ultrasonic cleaning, with a frequency of 35 kHz and a cleaning time of 6 minutes, using multi-frequency ultrasonic cleaning technology. Drawing, annealing and straightening, with an annealing temperature of 660 °C and a holding time of 3 hours, and using rapid cooling technology after annealing.

[0126] Final processing: Surface coating treatment, with the coating material being an epoxy resin-based anti-corrosion coating, a coating thickness of 80 μm, and using high-pressure airless spraying technology. Curing treatment, with a curing temperature of 92 °C and a curing time of 1.2 hours, and using far-infrared radiation heating technology. Online inspection, including ultrasonic flaw detection, eddy current flaw detection, magnetic particle flaw detection and X-ray flaw detection, etc., to ensure product quality. Using big data analysis technology.

[0127] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A low-temperature resistant cold-drawn steel section, characterized in that: The components and weight percentages of the cold-drawn section steel are as follows: C: 0.15% - 0.20%, Si: 0.3% - 0.45%, Mn: 1.4% - 1.5%, P ≤ 0.01%, S ≤ 0.003%, Ti: 0.04% - 0.045%, Cu ≤ 0.015%, V: 0.04% - 0.045%, Ni: 6% - 8%, Als: 0.02% - 0.03%, Ca: 0.002% - 0.006%, B: 0.0015% - 0.0025%, Mo: 0.1% - 0.3%, and the balance is Fe and unavoidable impurities. The total elongation Agt under the maximum force of the cold-drawn section steel at -196°C ≥ 8%, and the Charpy V-notch impact energy absorption KV2 ≥ 30 J.

2. The cryogenic-resistant cold-drawn steel section according to claim 1, characterized in that: The cold-drawn section steel further includes trace amounts of Nb with a weight percentage of 0.01% - 0.02% and trace amounts of Zr with a weight percentage of 0.005% - 0.015%.

3. A method for preparing a low-temperature resistant cold-drawn steel section according to claim 2, characterized in that: The method includes the following steps: (a) Conventional smelting and continuous casting. During the smelting process, electromagnetic stirring technology is adopted to improve the uniformity of the molten steel and reduce inclusions. (b) Stack cooling the continuous casting billet to room temperature. During the cooling process, forced air cooling technology is adopted to accelerate cooling and refine the grains. (c) Heating the steel billet. The heating temperature is 1150°C - 1250°C, and the heating time is 24 hours. During the heating process, multi-stage heating technology of a soaking furnace is adopted to ensure uniform heating of the steel billet. (d) Rough rolling the heated steel billet. The reduction ratio of rough rolling is 10% - 20%. (e) Finish rolling the rough-rolled steel billet. The reduction ratio of finish rolling is 20% - 30%, and the thickness of the steel after finish rolling is 1.1 - 1.3 times the finished thickness. (f) Online quenching treatment of the finish-rolled steel billet to improve the hardness and strength of the steel. The quenching medium is an aqueous solution of polyethylene glycol, and the quenching temperature is 850°C - 900°C. (g) Self-tempering treatment of the quenched steel to eliminate quenching stress and improve toughness. The self-tempering temperature is 300°C - 400°C, and the holding time is 1 - 2 hours. (h) Air-cooling the steel to room temperature and making it ready for use.

4. The preparation method of a low-temperature resistant cold-drawn steel section according to claim 3, characterized in that: After step (h), it further includes a step of pickling the steel to remove the surface oxide layer. Electrolytic pickling technology is adopted for pickling to improve pickling efficiency and surface quality.

5. The preparation method of a low-temperature resistant cold-drawn steel section according to claim 4, characterized in that: After the pickling step, it further includes phosphating the steel to form a dense phosphate protective film on the surface of the steel and improve the corrosion resistance of the steel. The phosphating solution used for phosphating treatment includes the following components in parts by weight: zinc dihydrogen phosphate 60 g / L, zinc nitrate 80 g / L, sodium permanganate 50 g / L, sodium chlorate 1 g / L, organic accelerator 4.5 g / L, where the weight ratio of m-nitrobenzenesulfonic acid sodium salt to hydroxylamine sulfate is 1:2, citric acid 2 g / L, sodium fluoride 1.5 g / L, OP-10 emulsifier 2 ml / L, and the balance is water. Appropriate amounts of nano-silica particles are added to the phosphating solution to improve the compactness and corrosion resistance of the phosphating film.

6. The preparation method of a low-temperature resistant cold-drawn steel section according to claim 5, characterized in that: After phosphating treatment, it also includes an ultrasonic cleaning step for the steel to remove the tiny impurities and bubbles generated during the phosphating process. The cleaning frequency is 20 kHz - 40 kHz, and the cleaning time is 5 - 10 minutes.

7. The preparation method of a low-temperature resistant cold-drawn steel section according to claim 6, characterized in that: After ultrasonic cleaning, it also includes steps of drawing, annealing, and straightening the steel. The annealing temperature is 600 °C - 700 °C, the holding time is 2 - 4 hours. After annealing, a rapid cooling technique is adopted to refine the grains after annealing and improve the strength and toughness of the steel. The cooling medium is nitrogen, and the cooling rate is 30 °C / s - 50 °C / s.

8. The preparation method of a low-temperature resistant cold-drawn steel section according to claim 7, characterized in that: After the straightening step, it also includes a surface coating treatment for the steel to improve the corrosion resistance and wear resistance of the steel. The coating material is an epoxy resin-based anti-corrosion coating, and the coating thickness is 50 - 100 μm.

9. The preparation method of a low-temperature resistant cold-drawn steel section according to claim 8, characterized in that: After the coating treatment, it also includes a curing treatment for the steel to ensure the firmness and durability of the coating. The curing temperature is 80 °C - 100 °C, and the curing time is 1 - 2 hours.

10. The preparation method of a low-temperature resistant cold-drawn steel section according to claim 9, characterized in that: During the preparation process, an on-line detection technique is also adopted to monitor the quality of the steel and the production process parameters in real time to ensure the product quality, including but not limited to ultrasonic flaw detection, eddy current flaw detection, and magnetic particle flaw detection.

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