CN114086074B - High-corrosion-resistance cold forging steel for ocean island reef and production method and heat treatment method thereof - Google Patents
High-corrosion-resistance cold forging steel for ocean island reef and production method and heat treatment method thereof Download PDFInfo
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Abstract
The invention provides high-corrosion-resistance cold forging steel for ocean island reef and a production method and a heat treatment method thereof, and the cold forging steel comprises the following components: 0.08 to 0.15 percent of C, 0.20 to 0.40 percent of Si, 0.20 to 0.30 percent of Mn, 5.0 to 7.0 percent of Cr, 0.90 to 1.20 percent of Ni, 0.020 to 0.040 percent of Al, 0.015 to 0.025 percent of Y, 0.010 to 0.020 percent of Ce, less than or equal to 0.0015 percent of T.O and less than or equal to 2.0ppm of H; the balance of Fe and other inevitable impurities. I is controlled to be more than or equal to 0.052, I = (Y + Ce)/(Si +8.1 xAl). Compared with the prior art, the cold forging steel provided by the invention has excellent comprehensive performance, especially Cl resistance ‑ The corrosion performance can reach 6 times of that of common 10.9 grade cold heading steel, and the high-strength fastening piece is very suitable for manufacturing high-strength fastening pieces in the ocean island and reef environment.
Description
Technical Field
The invention belongs to the technical field of cold forging steel, and particularly relates to high-corrosion-resistance cold forging steel for ocean island rocks, a production method and a heat treatment method thereof.
Background
Due to the development and construction of marine reefs, there is an increasing demand for steel for marine reefs. However, since the island is in a severe corrosion environment of high temperature, high humidity and salt mist, the steel for common bolts and even weather-resistant cold heading steel are corroded seriously and need to be replaced regularly. In order to meet the requirements of island reef development and construction, the research and development of the high-corrosion-resistance cold heading steel is urgent.
Chinese patent CN108070796A published in 2018, 5, 25 and discloses a 1040 MPa-grade weather-resistant bolt resistant to delayed fracture, which comprises the following chemical components in percentage by mass: c:0.21-0.32, si:0.10 to 0.50, mn:0.60-1.00, P:0.008-0.020, S: less than or equal to 0.005, cr:0.82 to 1.20, ni:0.25 to 0.50, cu:0.25 to 0.50, mo:0.05 to 0.20, nb:0.015-0.060, V:0.015 to 0.090, ti:0.008-0.035, B:0.0008 to 0.0035, al:0.015-0.040, ca:0.003-0.007, zr:0.015 to 0.045, re:0.010 to 0.045, and the balance being Fe and unavoidable impurities; the preparation method of the bolt mainly adopts the conventional high-purity melting-continuous casting-rolling technology, and the manufactured bolt is resistant to delayed fracture and atmospheric corrosion; however, the material is added with alloy elements such as Cu, nb, V, ti, zr and the like, so that the cost is higher; and is mainly resistant to industrial atmosphere corrosion and not suitable for marine island and reef environments.
Chinese patent CN101215676A published in 9.2008, a month discloses a steel for a high-strength corrosion-resistant fastener, which is characterized in that the chemical components (weight percentage) of the material are as follows: 0.14 to 0.17 percent of C, 0.17 to 0.24 percent of Si, 0.50 to 0.70 percent of Mn, 0.85 to 0.95 percent of Cr, 0.25 to 0.35 percent of Ni, 0.20 to 0.25 percent of Cu, 0.25 to 0.35 percent of Al, and the balance of Fe. The fastener made of steel produced by the method has better oxidation resistance and corrosion resistance; but can not meet the use requirement of the marine island environment.
Chinese patent CN 10139634B at 4/1/2009 discloses air corrosion resistant 08CrNiCu low-alloy high-strength annealing-free cold forging steel and a production process, which are characterized in that the steel comprises the following chemical components in percentage by weight: 0.05-0.90%, si:0.15-0.25%, mn:0.55-0.65%, P:0.005-0.025%, S:0.005-0.02%, cr:0.65-0.75%, ni:0.25-0.30%, cu:0.35-0.40%, and the balance of Fe and inevitable impurities; can be used for processing 8.8-grade bolts and matched nuts. But it is mainly resistant to industrial atmospheric corrosion and is not suitable for marine island and reef environments.
At present, corrosion-resistant construction steel such as plates and section steel is researched more, and products are relatively mature. Although corrosion-resistant cold heading steel has certain research accumulation, the corrosion-resistant cold heading steel is still in the starting stage and is not widely applied, and the research on the steel for the high-corrosion-resistant fastener for the island is almost blank. With the development of the island, the development of the cold forging steel with high corrosion resistance suitable for the environment of the ocean island is urgently needed.
Disclosure of Invention
The invention aims to provide high-corrosion-resistance cold forging steel for ocean island reefs and a production method thereof, wherein the cold forging steel has excellent comprehensive performance and Cl resistance - The corrosion performance can reach 6 times of that of common 10.9 grade cold heading steel, and the high-strength fastening piece is very suitable for manufacturing high-strength fastening pieces in the ocean island and reef environment.
The invention also provides a heat treatment method of the high-corrosion-resistance cold forging steel for the ocean island, and the heat treatment mechanical property reaches 8.8-10.9 grades according to different heat treatment processes.
The specific technical method of the invention is as follows:
the high-corrosion-resistance cold forging steel for the ocean island comprises the following components in percentage by mass:
0.08 to 0.15 percent of C, 0.20 to 0.40 percent of Si, 0.20 to 0.30 percent of Mn, 5.0 to 7.0 percent of Cr, 0.90 to 1.20 percent of Ni, 0.020 to 0.040 percent of Al, 0.015 to 0.025 percent of Y, 0.010 to 0.020 percent of Ce, less than or equal to 0.0015 percent of T.O, less than or equal to 2.0ppm of H, and the balance of Fe and other inevitable impurities.
The composition of the high-corrosion-resistance cold forging steel for the ocean island reef meets the following conditions: i is not less than 0.052, I = (Y + Ce)/(Si +8.1 xAl).
The design principle of the components of the invention is as follows:
c: c is the most basic effective strengthening and hardenability element in steel. However, if the C content is too high, ductility is reduced and corrosion resistance of the steel is lowered. The content of C is controlled to be 0.08-0.15 percent.
Si: si is an important element for strengthening in steel, and the strength and hardness of the steel are improved through solid solution. However, the formation of Si in steel forms hard inclusions in the steel, which jeopardize the plasticity and toughness of the steel. The Si content is controlled between 0.20 percent and 0.40 percent.
Mn: mn and Fe form a solid solution, so that the hardness and strength of ferrite and austenite in the steel are improved, and meanwhile, mn is used for improving the stability of an austenite structure and remarkably improving the hardenability of the steel. However, excessive Mn may reduce the plasticity of the steel. The addition of Mn is also beneficial to forming a rust layer on the surface of steel, the corrosion resistance of steel is improved, excessive Mn can cause the growth of corrosion product particles, and the corrosion rate is improved. The Mn content is controlled to be 0.20-0.30%.
Cr: cr is an element which has great influence on the corrosion resistance of steel, can form a compact and complete oxide film between a rust layer on the surface of the steel and a steel matrix, can refine the crystal grains of alpha-FeO (OH) in the rust layer, and can effectively inhibit corrosive anions, particularly Cl - Invasion of ions. Meanwhile, the rust layer can be prevented from being reduced during drying in the dry-wet alternating process, and the corrosion resistance of the steel is improved. The Cr content is controlled to be 5.0-7.0 percent.
Ni: ni can reduce the self-corrosion potential of steel, make the self-corrosion potential of steel move forward, increase stability. At the same time, ni tends to accumulate in the rust layer and is somewhat resistant to Cl - Promotes the formation of a protective rust layer, thereby reducing the corrosion rate of the steel. The Ni element in the steel can also obviously improve the impact toughness of the steel. Too much Ni element increases the cost and the effect is no longer significant. The Ni content is controlled to be 0.90-1.20%.
Al: al is a strong deoxidizing element, and simultaneously, the oxidation resistance of the steel is improved. Al is also an important element in cold heading steel, can refine structure grains and ensure cold heading performance. However, as the Al content increases, the amount of coarse carbonitride-based inclusions increases. The content of Alt is controlled to be 0.020-0.040%.
Y and Ce: the right amount of rare earth Y and Ce is added into the steel, and one of the functions is to wrap the rare earth Y and Ce in SiO 2 、A1 2 O 3 Around the inclusion, it is changed into rare earth inclusion, so that it possesses good deoxidation and desulfurization action. In the invention, Y and Ce large atoms are used for partializing the rust layer, so that after the rust layer is formed on the steel surface, protection is formed at the position of a matrix close to the rust layerThe sexual atomic layer can prevent the rust layer from expanding to the interior of the substrate, and can effectively slow down the corrosion rate. Excessive Y and Ce may cause the formation of nodules during the casting of molten steel. The content of Y is controlled to be 0.015-0.025 percent and the content of Ce is controlled to be 0.010-0.020 percent.
In the present invention, in order to obtain sufficient corrosion resistance, it is necessary to ensure that Y and Ce elements act on SiO in addition to low C and high Cr and Ni 2 、A1 2 O 3 Besides the modified coating of the inclusions, enough free atoms of Y and Ce can be used for improving the corrosion resistance of the steel in the rust layer, so the proportion of Y, ce, si and A1 is limited, and according to the weight ratio of each element of the modified inclusions and the requirement of the steel on the corrosion resistance, the I value is more than or equal to 0.052, the I value is not less than (= (Y + Ce)/(Si +8.1 xAl), and more preferably not less than 0.054.
T.O: T.O is easy to cause oxidation of Y and Ce in steel to form inclusions, and the T.O is controlled to be less than or equal to 0.0015 percent.
H: the high-strength fastener is easy to generate hydrogen-induced delayed fracture, so that the content of H in steel is controlled, the delayed fracture resistance of the steel is improved, and H is controlled to be less than or equal to 2.0ppm.
The invention provides a production method of high-corrosion-resistance cold heading steel for ocean island rocks, which comprises the following process flows of:
preparing materials → smelting in an electric arc furnace → refining in an LF furnace → RH vacuum degassing → continuous casting → square billet heating → high-speed wire rolling → stelmor cooling line cooling → finished products of 5.5-30mm wire rods.
Wherein:
the electric arc furnace smelting is specifically controlled as follows: the C content of the steel liquid after tapping is less than or equal to 0.06 percent, bottom argon blowing is carried out before tapping, and the argon blowing flow is adjusted based on the fact that the steel ladle does not tumble due to the steel liquid;
the LF furnace refining is specifically controlled as follows: deoxidizing and desulfurizing, and selecting CaO-SiO as white slag 2 -Al 2 O 3 -MgO series slag sample, white slag comprises the following main components in percentage by mass: caO 55-60%, siO 2 :15-25％、Al 2 O 3 Less than or equal to 15 percent; mgO is less than or equal to 4 percent, white slag is kept for more than 20min, the balance of molten steel and steel slag can be fully realized by the white slag system and the white slag system, the appearance of inclusions is improved, and the later period is facilitatedModification of the inclusion; while controlling (FeO) + (MnO) in the refining slag<l.0%, thereby effectively reducing the oxygen content in the steel.
The RH vacuum degassing is specifically controlled as follows: RH continuously carries out circulation degassing operation to remove gas and impurities in the molten steel, and pure degassing time is controlled to be more than or equal to 15min so as to ensure that the [ H ] is treated in vacuum]≤1.5×10 -6 、O≤0.001％。
The continuous casting specifically comprises the following steps: the Y line and the Ce line are added into the crystallizer by adopting electromagnetic stirring, and the Y line and the Ce line are added at the positions to avoid oxidation, thereby improving the contribution of the Y line and the Ce line to the corrosion resistance to the maximum extent. The whole process adopts protective casting, a crystallizer liquid level control system is adopted, and the fluctuation of the liquid level is controlled to be less than or equal to +/-3 mm. The size of the continuous casting square billet is 140mm multiplied by 140mm-300mm multiplied by 300mm, and slow cooling is carried out for more than or equal to 24 hours in a pit entering mode.
The high speed wire rolling is specifically controlled as follows: controlling the soaking temperature of square billet heating to be 1080-1180 ℃, and if the soaking temperature is lower than 1080 ℃, alloy elements such as Cr, ni and the like cannot be uniformly diffused, so that the steel has composition segregation; if the temperature is higher than 1180 ℃, surface tissues can be coarsened; controlling the spinning temperature to be 760-800 ℃, and if the spinning temperature is lower than 760 ℃, entering a phase change stage before entering a heat-preserving cover to generate abnormal tissues; if the temperature is higher than 800 ℃, the phase transition temperature is not reached before the coil enters the heat-insulating cover, the complete phase transition on the stelmor line is difficult to complete, and a large amount of phase transition is abnormal tissue during coil collection, so that the brittle fracture of the wire rod is caused.
And cooling the stelmor cooling line, controlling the cover of the heat preservation section to be completely closed, and controlling the cooling speed of the wire rod to be not higher than 0.15 ℃/s.
The steel with the formula is produced by the method, so that an ideal structure of 70-85% of ferrite and 15-30% of Maoeryan with an area ratio is obtained, and the grain size reaches more than 10 grades. In addition, because of inclusion modification, the steel contains less non-metal inclusions, and especially the number of long-strip-shaped inclusions is less than or equal to 2/mm 2 And the grades are all below 0.5 grade. The excellent drawing performance of the wire rod can be ensured through the structure, the grain size and the impurities.
The invention provides a heat treatment method of high-corrosion-resistance cold forging steel for ocean island rocks, which comprises the following steps: quenching, oil cooling, tempering and air cooling.
The quenching is carried out at 920-950 ℃, alloy elements in the steel can not be fully dissolved in austenite below the temperature, and austenite grains are coarse due to the temperature above the temperature; the oil cooling means that: cooling the oil to the normal temperature at 45-65 ℃/s.
Tempering at 540-600 ℃; and air cooling after tempering.
After the heat treatment method is adopted, the mechanical property of the product reaches 8.8-10.9 grades; impact toughness of more than or equal to 100J at minus 20 ℃, especially Cl resistance - The corrosion performance can reach 6 times of that of common 10.9 grade cold heading steel.
Wherein the tempering temperature is controlled at 570-600 ℃, and the mechanical property of the product reaches 8.8 grade: rm is more than or equal to 830MPa, rp0.2 is more than or equal to 660MPa, A is more than or equal to 12 percent, Z is more than or equal to 52 percent, and the yield ratio is more than or equal to 0.8;
wherein the tempering temperature is controlled at 540-560 ℃, and the mechanical property of the product reaches 10.9 grade: r m ≥1040MPa，R p0.2 940MPa or more, A is or more than 9 percent, Z is or more than 48 percent, and the yield ratio is or more than 0.9.
The tempering temperature is 560-570 ℃, partial performance of the product reaches 8.8 grades, and partial performance reaches 10.9 grades.
Compared with the prior art, the high-corrosion-resistance cold forging steel for the ocean island reef has excellent comprehensive performance, the hot-rolled structure is ferrite accounting for 70-85% of the area ratio and martensite-austenite-island structure accounting for 15-30%, the grain size reaches more than 10 grade, and particularly, the number of long-strip-shaped impurities is less than or equal to 2/mm 2 And the grades are all below grade 0.5. The hot-rolled wire rod can be directly drawn without annealing, so that the cost is saved, and the energy and the time are saved. According to different heat treatment processes, the mechanical property of the heat treatment reaches 8.8 grade to 10.9 grade, the impact toughness at the temperature of minus 20 ℃ is more than or equal to 100J, and the Cl resistance is particularly realized - The corrosion performance can reach 6 times of that of common 10.9 grade cold heading steel. The high-strength fastener is very suitable for manufacturing high-strength fasteners in the marine island reef environment.
Drawings
FIG. 1 is a microscopic image of the segregation of Y and Ce macro atoms in the rust layer of No. 1;
FIG. 2 shows inclusions in No.2 modified with Y and Ce;
FIG. 3 is a photograph of No.3 as a hot rolled structure.
Detailed Description
Example 1 to example 6
The high-corrosion-resistance cold forging steel for the ocean island comprises the following components in percentage by mass: as shown in table 1, the balance not shown in table 1 is Fe and inevitable impurities.
Comparative examples 1 to 3
The high-corrosion-resistance cold forging steel for the ocean island comprises the following components in percentage by mass: as shown in table 1, the balance not shown in table 1 is Fe and inevitable impurities.
TABLE 1 ingredients of examples and comparative examples
| Examples | Steel grade | C | Si | Mn | Cr | Ni | Cu |
| Example 1 | A | 0.08 | 0.2 | 0.30 | 5.0 | 1.20 | / |
| Example 2 | B | 0.15 | 0.33 | 0.20 | 7.0 | 0.90 | / |
| Example 3 | C | 0.10 | 0.40 | 0.23 | 5.6 | 1.14 | / |
| Example 4 | D | 0.13 | 0.25 | 0.28 | 6.6 | 1.03 | / |
| Example 5 | E | 0.12 | 0.28 | 0.25 | 6.2 | 0.97 | / |
| Example 6 | F | 0.11 | 0.36 | 0.26 | 5.3 | 1.09 | / |
| Comparative example 1 | G | 0.13 | 0.39 | 0.26 | 5.7 | 1.04 | / |
| Comparative example 2 | H | 0.35 | 0.28 | 0.82 | / | / | / |
| Comparative example 3 | I | 0.32 | 0.25 | 0.75 | 0.87 | 0.35 | 0.34 |
| Examples | Steel grade | Al | Y | Ce | T.O | H | Value of I |
| Example 1 | A | 0.020 | 0.015 | 0.020 | 0.0015 | 1.5×10 -6 | 0.097 |
| Example 2 | B | 0.040 | 0.025 | 0.010 | 0.0011 | 1.0×10 -6 | 0.054 |
| Example 3 | C | 0.025 | 0.020 | 0.013 | 0.0009 | 1.5×10 -6 | 0.055 |
| Example 4 | D | 0.034 | 0.018 | 0.017 | 0.0009 | 1.5×10 -6 | 0.067 |
| Example 5 | E | 0.031 | 0.022 | 0.015 | 0.0009 | 1.0×10 -6 | 0.070 |
| Example 6 | F | 0.037 | 0.020 | 0.014 | 0.0012 | 1.5×10 -6 | 0.052 |
| Comparative example 1 | G | 0.038 | 0.016 | 0.011 | 0.0012 | 2.0×10 -6 | 0.039 |
| Comparative example 2 | H | 0.033 | / | / | 0.0008 | 1.5×10 -6 | / |
| Comparative example 3 | I | 0.032 | / | / | 0.0009 | 1.5×10 -6 | / |
The production method of the high-corrosion-resistance cold heading steel for the marine island in each embodiment and each comparative example comprises the following process flows of:
preparing materials → smelting in an electric arc furnace → refining in an LF furnace → RH vacuum degassing → continuous casting → square billet heating → high-speed wire rolling → stelmor cooling line cooling → finished products of 5.5-30mm wire rods.
Wherein:
the electric arc furnace smelting is specifically controlled as follows: the C content of the steel liquid after tapping is less than or equal to 0.06 percent, bottom argon blowing is carried out before tapping, and the argon blowing flow is adjusted based on the fact that the steel ladle does not tumble due to the steel liquid;
the LF furnace refining is specifically controlled as follows: deoxidizing and desulfurizing, and selecting CaO-SiO as white slag 2 -Al 2 O 3 -MgO series slag sample, white slag comprises the following main components in percentage by mass: 55-60% of CaO and SiO 2 :15-25％、Al 2 O 3 Less than or equal to 15 percent; mgO is less than or equal to 4 percent, and the white slag is kept for more than 20 min; simultaneous controlled refiningSlag of (FeO) + (MnO)<l.0 percent, thereby effectively reducing the oxygen content in the steel.
The RH vacuum degassing is specifically controlled as follows: RH continuously carries out circulation degassing operation to remove gas and impurities in the molten steel, and pure degassing time is controlled to be more than or equal to 15min so as to ensure that the [ H ] is treated in vacuum]≤1.5×10 -6 、O≤0.001％。
The continuous casting specifically comprises the following steps: electromagnetic stirring is adopted, Y lines and Ce lines are added into a crystallizer, protective casting is adopted in the whole process, a crystallizer liquid level control system is adopted, and liquid level fluctuation is controlled to be less than or equal to +/-3 mm. The size of the continuous casting square billet is 140mm multiplied by 140mm-300mm multiplied by 300mm, and the slow cooling is carried out for more than or equal to 24 hours by adopting a pit entering mode.
The high-speed wire rolling is specifically controlled as follows: controlling the soaking temperature of square billet heating to be 1080-1180 ℃; controlling the spinning temperature to be 760-800 ℃; the cover of the heat preservation section is controlled to be totally closed, and the cooling speed of the wire rod is controlled to be below 0.15 ℃/s.
The steel grades corresponding to the examples and the comparative examples are produced according to the method, and the specific process parameters are shown in table 2:
TABLE 2 specific Process parameters for examples of the invention and comparative examples
The performance detection method comprises the following steps:
hot rolled texture, grain size and non-metallic inclusions: taking a sample with the length of 15mm from a hot-rolled wire rod, polishing the cross section, corroding by using 4% nitric acid alcohol, performing texture evaluation according to GB/T13298 & lt & ltMetal microstructure inspection method & gt & lt, performing grain size rating according to GB/T6394 & lt & gt Metal average grain size determination method & lt, carrying out grain size rating; taking a sample with the length of 20mm from a hot-rolled wire rod, polishing the longitudinal section, grading nonmetallic inclusions according to GB/T10516 method for measuring the content of nonmetallic inclusions in steel, and grading nonmetallic inclusions according to the structure, the grain size and the nonmetallic inclusionsInclusion can determine whether the wire rod can be directly processed into a fastener without annealing. Tensile properties after heat treatment: the wire rods produced in the above examples and comparative examples were subjected to the following quenching and tempering heat treatment process without annealing: quenching at 920-950 ℃, oil cooling to normal temperature at 45-65 ℃/s, tempering at 540-600 ℃, and air cooling. The heat treatment process parameters of each example and comparative example are specifically shown in table 3. Straightening after heat treatment, performing a tensile test, and testing R m 、R p0.2 A and Z values, and calculating the yield ratio.
-20℃KV 2 Impact work: and (3) carrying out heat treatment on the sample according to the heat treatment process, processing the V-shaped groove impact sample, and carrying out an impact test at the temperature of-20 ℃ according to GB/T229 (method for testing impact of Charpy pendulum mass of metal material) to obtain an impact toughness value.
32h salt spray test: samples were taken from the billets and 150mm by 57mm by 0.8mm specimens were processed and tested in a circulating corrosive salt spray cabinet. The salt spray test was carried out in accordance with GB/T10125 salt spray test for Artificial atmosphere Corrosion test, with the corrosion medium being 5% NaCl solution, the temperature in the test chamber being (35. + -. 2). Degree.C, and with the continuous spray method. Every 80cm 2 The amount of the salt mist sedimentation of (2) is about 1.5mL/h. The test is carried out for 32h, after the test is finished, corrosion products are removed according to a physical and chemical method specified by ISO8407, then the materials are cleaned, dried and weighed, and the unit weight loss rate W is calculated according to the following formula:
in the formula: w-weight loss per unit, g/m 2 ；G 0 -sample original weight, g; g 1 -the post-test weight of the sample, g; a-specimen length, mm; b-sample width, mm; c-specimen thickness, mm.
The test results of the above-described respective examples and comparative examples are shown in tables 3 and 4.
TABLE 3 hot rolled state test of examples of the present invention and comparative examples
TABLE 4 Heat treatment Performance test of inventive and comparative examples
The chemical composition and production method of steel of test No.1-No.6 are properly controlled according to the method of the invention, and during the refining of molten steel, caO-SiO is selected as white slag 2 -Al 2 O 3 -MgO series slag sample, and controlling the main components and the mass content of the white slag as follows: 55-60% of CaO and SiO 2 :15-25％、Al 2 O 3 Less than or equal to 15 percent; mgO is less than or equal to 4 percent, the obtained hot rolled wire rod has ideal structure, fine grains and high purity, and a user can directly draw and cold-heading without annealing. The chemical composition of the rust inhibitor ensures that the I value is more than 0.052, so that the strong corrosion resistance of Cr and Ni elements is utilized, and Y and Ce large atoms are also utilized to be segregated to the interface of the rust layer and the matrix, so that after the rust layer is formed on the surface of steel, a protective atomic layer is formed on the matrix close to the rust layer, the rust layer is prevented from spreading to the interior of the matrix, and the corrosion rate is effectively reduced (FIG. 1 is a microscopic image of segregation of Y and Ce large atoms in the rust layer in No. 1). And then according to different heat treatment processes, the mechanical property of the steel reaches 8.8-10.9 grades, the impact toughness at the temperature of minus 20 ℃ is more than 100J, and the corrosion resistance of a 32h salt spray test is more than 6 times of that of 8.8-grade cold forging steel SWRCH35KE commonly used in the current market. Customers can adjust the heat treatment process according to the needs of the customers, and the high-corrosion-resistance 8.8-10.9-grade high-strength fastener for the ocean reefs is processed.
FIG. 2 shows inclusions in No.2 modified by Y and Ce; y and Ce are wrapped outside the brittle inclusion, the inclusion is changed from the shape and the property, the shape is elongated into a round shape or an oval shape, and the brittle inclusion is changed into a ductile inclusion in the property. Reducing the damage of the original brittle inclusion.
Test No.7 is suitable for controlling chemical components, but in the production method, because the proportion of (FeO) + (MnO) is not properly controlled during smelting, the white slag retention time and the RH pure degassing time are insufficient during LF, so that the purity of molten steel is poor, the gas contents of [ H ], O and the like in steel are high, and more nonmetallic inclusions exist, so that the plasticity after heat treatment is poor, the standard requirement is not met, and the impact toughness of the steel is also insufficient;
test No.8 shows that the chemical composition and the production method of the steel are properly controlled, but because the quenching temperature is lower than the requirement of the invention during the heat treatment, the alloy elements are not fully dissolved in the steel, although the tempering temperature of the subsequent pass is properly controlled, carbides still cannot be fully precipitated, and a large amount of alloy elements are segregated in the grain boundary, but the plasticity and the toughness of the steel are poor;
test No.9 shows that the production method is properly controlled, the chemical components are in the required range, but the I value does not meet the requirement, so that the corrosion resistance of the steel is lower than that of the steel in the embodiment of the invention;
test No.10 is 8.8 grade cold forging steel SWRCH35K which is generally used in the market, has good strength and plasticity, reaches 8.8 grade requirements after proper heat treatment, but has poor impact toughness and no corrosion resistance;
test No.11 is a widely used Cr-Ni-Cu weathering steel resistant to industrial atmospheric corrosion, but resistant to Cl - The corrosion performance is insufficient, and the method is not suitable for being used in the marine island reef environment.
Claims (10)
1. The high-corrosion-resistance cold forging steel for the ocean island is characterized by comprising the following components in percentage by mass:
0.08 to 0.15 percent of C, 0.20 to 0.40 percent of Si, 0.20 to 0.30 percent of Mn, 5.0 to 7.0 percent of Cr, 0.90 to 1.20 percent of Ni, 0.020 to 0.040 percent of Al, 0.015 to 0.025 percent of Y, 0.010 to 0.020 percent of Ce, less than or equal to 0.0015 percent of T.O and less than or equal to 2.0ppm of H; the balance of Fe and other inevitable impurities;
the components of the high-corrosion-resistance cold forging steel for the ocean island meet the following conditions: i is more than or equal to 0.052, I = (Y + Ce)/(Si +8.1 xAl);
the high-corrosion-resistance cold forging steel for the ocean island comprises the following tissues: ferrite accounting for 70-85% of the area ratio and a martensite-austenite structure accounting for 15-30% of the area ratio, wherein the grain size reaches more than 10 grades; the number of the long-strip-shaped impurities is less than or equal to 2/mm 2 And the grades are all below 0.5 grade.
2. The production method of the high corrosion resistance cold heading steel for the marine island according to claim 1, characterized by comprising the following process flows:
preparing materials → smelting in an electric arc furnace → refining in an LF furnace → RH vacuum degassing → continuous casting → square billet heating → high-speed wire rolling → stelmor cooling line cooling → wire rod finished product.
3. The production method according to claim 2, characterized in that the electric arc furnace smelting is specifically controlled as follows: the C content of the tapped molten steel is less than or equal to 0.06 percent.
4. The production method according to claim 2, characterized in that the LF furnace refining is specifically controlled as follows: deoxidizing and desulfurizing, and selecting CaO-SiO as white slag 2 -Al 2 O 3 -MgO slag sample, white slag retention time is above 20 min; simultaneously controlling (FeO) + (MnO) in the refining slag<l.0%。
5. The production method according to claim 2 or 4, wherein the RH vacuum degassing is specifically controlled as: controlling the pure degassing time to be more than or equal to 15min to ensure that the [ H ] is treated in vacuum]≤1.5×10 -6 、O≤0.001%。
6. The production method according to claim 2, characterized in that the continuous casting is in particular: electromagnetic stirring is adopted, Y lines and Ce lines are added into a crystallizer, protective casting is adopted in the whole process, a crystallizer liquid level control system is adopted, and the fluctuation of the liquid level is controlled to be less than or equal to +/-3 mm.
7. The production method according to claim 2, wherein the high-speed wire rod rolling is specifically: controlling the soaking temperature of square billet heating to be 1080-1180 ℃; controlling the spinning temperature to be 760-800 ℃; the cover of the heat preservation section is controlled to be totally closed, and the cooling speed of the wire rod is controlled to be not higher than 0.15 ℃/s.
8. The heat treatment method of the highly corrosion-resistant cold forging steel for marine island reef according to claim 1, which comprises the following steps: quenching, oil cooling, tempering and air cooling.
9. The heat treatment method according to claim 8, wherein the quenching is performed at 920-950 ℃ and then oil-cooled to normal temperature at 45-65 ℃/s.
10. A heat treatment method according to claim 8 or 9, characterized in that the tempering is performed at 540-600 ℃.
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