Preparation method of Q460NE high-strength steel plate with thickness of less than 40mm for strip mine equipment

Abstract

The invention discloses a preparation method of a Q460NE high-strength steel plate for strip mine equipment with the thickness of 40 mm or below. The steel plate comprises the following chemical components in percentage by weight: 0.16 to 0.18 percent of C, 0.20 to 0.30 percent of Si, 1.45 to 1.65 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, 0.04 to 0.05 percent of Nb, 0.035 to 0.045 percent of V, 0.010 to 0.020 percent of Ti, 0.017 to 0.027 percent of Als and the balance of Fe and impurities. The invention further discloses specific preparation steps and process parameters. The steel plate prepared through the method meets the requirements that the yield strength is larger than 460 MPa, the tensile strength is 540-720 MPa, the ductility is larger than 17%, the low-temperature impact energy at the temperature of-40 DEG C is higher than 50 J, and meanwhile good cold forming performance and welding performance are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of high-strength steel manufacturing, and in particular relates to a method for preparing a high-strength steel plate with a thickness of less than 40 mm for Q460NE open-pit mining equipment. Background Art

[0002] Q460NE is a grade specified in GB / T1591-2018 "Low Alloy High Strength Steel". It requires normalizing rolling or normalizing process production. It is widely used in the construction of many fields such as marine engineering, ships, high-rise buildings, pressure vessels, energy and chemical industry, engineering machinery, coal mining machinery, etc., but there are few related patents.

[0003] Normalizing rolling refers to a rolling process in which the final deformation is carried out by rolling within a certain temperature range, so that the steel reaches a normalized state so that the specified mechanical properties can be achieved even after normalizing. As far as the production and processing of hot-rolled steel plates are concerned, it will have more advantages if this state is achieved directly during the rolling process without normalizing heat treatment.

[0004] It can make the final state of the material similar to that of normalizing heat treatment, and the specified values ​​of its mechanical properties are also the same as those of normalizing. The solution of normalizing rolling replaces normalizing heat treatment, thereby reducing the production link of normalizing steel plates, shortening the realization cycle, reducing energy costs, and increasing its own competitiveness. However, it is difficult to strengthen and refine the structure through water cooling in normalizing rolling, and the requirements for chemical composition and rolling process will become more stringent.

[0005] Chinese patent CN103614608 A discloses "a method for producing Q460C grade high-strength steel". The VN microalloying process is used to produce Q460C grade angle steel for transmission towers. The disadvantages are that it is not suitable for steel plates and the quality grade is C.

[0006] Chinese patent CN 113249641 B discloses "a 100-120mm Q460D ultra-thick high-strength steel and its preparation method", chemical composition and mass percentage C: 0.10-0.13%, Si: 0.30-0.50%, Mn: 1.40-1.60%, P: ≤0.0070%, S: ≤0.0020%, Nb: 0.020-0.050%, Ti: 0.008-0.020%, Al: 0.020-0.040%, Cu: 0.10-0.20%, Cr: 0.10-0.20%, Ni: 0.10-0.20%, the balance is Fe and unavoidable impurity elements. Production process: converter-LF refining-RH vacuum degassing-Ca treatment-continuous casting-ingot dehydrogenation treatment-heating-normalizing rolling-air cooling-steel plate stacking and slow cooling-destacking. The yield strength of the steel plate is between 430-470MPa, the tensile strength is between 550-570MPa, the elongation is ≥20%, and the Charpy impact energy at 1 / 4 and 1 / 2 of the thickness at -20℃ is ≥200J. The disadvantage is that it is suitable for thicknesses above 100mm and the quality grade is D.

[0007] Chinese patent CN 106086647 B discloses "a low alloy high strength steel Q460C and its production method". Chemical composition and mass percentage C: 0.11-0.15, Si: 0.20-0.40, Mn: 1.30-1.50, Nb: 0.01-0.02, Ti: 0.050-0.070, Als: 0.020-0.040, Q460C steel plate is produced by controlled rolling and controlled cooling process. The disadvantage is that the quality grade is C grade. Summary of the invention

[0008] The purpose of the present invention is to provide a method for preparing a Q460NE open-pit mining equipment high-strength steel plate with a thickness of less than 40 mm. The steel plate has the following properties: yield strength greater than 460 MPa, tensile strength 540-720 MPa, elongation greater than 17%, and low-temperature impact energy of -40°C greater than 50 J. At the same time, it has good cold forming performance and welding performance, and the production method is stable and reliable with low cost.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0010] The present invention discloses a method for preparing a Q460NE open-pit mining equipment high-strength steel plate with a thickness of less than 40 mm, comprising the following steps:

[0011] S1 Hot metal pretreatment: After the hot metal is desulfurized and dephosphorized by KR stirring method, S≤0.005% and P≤0.015% are ensured;

[0012] S2 converter smelting: The converter smelting stage uses molten iron and high-quality scrap steel that have been pre-treated with desulfurization as raw materials. The molten iron temperature is ≥1260℃. The phosphorus and carbon content are reduced through three technologies: efficient top and bottom re-blowing, automatic furnace gas analysis, and dynamic and static automatic steelmaking, ensuring that the molten steel P≤0.010%, S≤0.004%;

[0013] S3 LF refining outside the furnace: During the refining stage outside the furnace, the composition of the molten steel is precisely controlled, deoxidation and alloying are carried out, and the non-metallic inclusions and harmful impurities in the molten steel are further reduced through calcium treatment and soft blowing process, S≤0.003%, and clean molten steel is obtained;

[0014] S4 RH vacuum treatment: reduce the content of hydrogen, oxygen and nitrogen in molten steel, keep the vacuum degree below 67Pa, and keep the vacuum time for more than 20 minutes;

[0015] S5 slab continuous casting: adopt dynamic soft pressure at the end of solidification, electromagnetic stirring, weak cooling in the second cooling stage and correction technology, strictly control the billet drawing speed during continuous casting at 0.8-1.0m / min, molten steel temperature, and superheat at 15-28℃, use medium carbon protective slag, strictly control liquid level fluctuation, reduce defects such as center segregation and center looseness of continuous casting billet, continuously cast high-quality slab with a thickness of 250mm, and slow cooling time of slab for more than 36 hours;

[0016] S6 Heating: The slab is heated in a walking beam heating furnace. The atmosphere in the furnace is strictly controlled to ensure the heating temperature and heating time of the slab. The heating temperature is controlled at 1210℃~1240℃. The total time in the furnace is greater than 220min to ensure sufficient solid solution of alloy elements and uniform temperature in the thickness and width of the slab.

[0017] S7 normalizing rolling: the starting rolling temperature is 1160-1200℃, the relative reduction rate of a single pass is controlled at least 18% for two passes; the starting rolling temperature of the finishing rolling is ≤930℃, the starting rolling thickness is 2-4 times the finished product thickness, the cumulative reduction is more than 60%, and the final rolling temperature is 800-850℃; after rolling, the steel plate enters the cooling bed for air cooling;

[0018] The chemical composition of the steel plate is C: 0.16-0.18%, Si: 0.20-0.30%, Mn: 1.45-1.65%, P: ≤0.015%, S: ≤0.005%, Nb: 0.04-0.05%, V: 0.035-0.045%, Ti: 0.010-0.020%, Als: 0.017-0.027%, and the balance is Fe and unavoidable impurities.

[0019] Furthermore, the chemical composition of the steel plate is C: 0.162%, Si: 0.23%, Mn: 1.56%, P: 0.010%, S: 0.002%, Nb: 0.042%, V: 0.039%, Ti: 0.009%, Als: 0.021%, and the remainder is Fe and unavoidable impurities.

[0020] Furthermore, the chemical composition of the steel plate is C: 0.163%, Si: 0.22%, Mn: 1.57%, P: 0.012%, S: 0.003%, Nb: 0.045%, V: 0.040%, Ti: 0.012%, Als: 0.022% by weight, and the remainder is Fe and inevitable impurities.

[0021] Furthermore, the chemical composition of the steel plate is C: 0.164%, Si: 0.26%, Mn: 1.60%, P: 0.010%, S: 0.002%, Nb: 0.046%, V: 0.043%, Ti: 0.014%, Als: 0.021% by weight, and the balance is Fe and inevitable impurities.

[0022] Furthermore, the chemical composition of the steel plate is C: 0.171%, Si: 0.30%, Mn: 1.61%, P: 0.011%, S: 0.002%, Nb: 0.047%, V: 0.043%, Ti: 0.016%, Als: 0.024% by weight, and the remainder is Fe and inevitable impurities.

[0023] Furthermore, the metallographic structure of the steel plate is ferrite + pearlite + a small amount of bainite, and the grain size is level 9.

[0024] Furthermore, the properties of the high-strength steel plate for open-pit mining equipment meet the following requirements: yield strength greater than 460 MPa, tensile strength 540-720 MPa, elongation greater than 17%, -40°C low-temperature impact energy greater than 50 J, and good cold forming and welding properties.

[0025] Compared with the prior art, the beneficial technical effects of the present invention are:

[0026] 1 Through the design of medium carbon-Nb-V-Ti chemical composition, the above normalizing rolling process is adopted to obtain a high-strength steel plate for open-pit mining equipment with a thickness of less than 40mm, a yield strength greater than 460MPa, a tensile strength of 540-720MPa, an elongation greater than 17%, a low-temperature impact energy of -40℃ greater than 50J, and good cold forming performance and welding performance.

[0027] 2 The metallographic structure of normalized rolled high-strength steel plate for open-pit mining equipment is ferrite + pearlite + a small amount of bainite, and the grain size is level 9. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the metallographic structure diagram of the normalizing rolled steel plate of Example 2 of the present invention.

[0029] Figure 2 This is a bending specimen of the steel plate under normalizing rolling according to Example 2 of the present invention.

[0030] Figure 3 This is a -40°C impact specimen of the steel plate under normalizing rolling in Example 2 of the present invention. DETAILED DESCRIPTION

[0031] The present invention is described in more detail below with examples. These examples are merely descriptions of the best mode for carrying out the present invention and are not intended to limit the scope of the present invention in any way.

[0032] The chemical composition of the steel plate of the present invention is C: 0.16-0.18%, Si: 0.20-0.30%, Mn: 1.45-1.65%, P: ≤0.015%, S: ≤0.005%, Nb: 0.04-0.05%, V: 0.035-0.045%, Ti: 0.010-0.020%, Als: 0.017-0.027%, and the balance is Fe and inevitable impurities.

[0033] The present invention provides a normalizing rolling production method for a Q460NE wind power steel plate, the main steps and process parameters of which are as follows:

[0034] S1 Hot metal pretreatment: After the hot metal is desulfurized and dephosphorized by KR stirring method, S≤0.005% and P≤0.015% are ensured;

[0035] S2 converter smelting: In the converter smelting stage, molten iron and high-quality scrap steel that have undergone desulfurization pretreatment are used as raw materials. The molten iron temperature is ≥1260℃. The phosphorus and carbon content are reduced through three technologies such as high-efficiency top and bottom blowing, automatic furnace gas analysis, and dynamic and static automatic steelmaking to ensure that the molten steel P≤0.010% and S≤0.004%.

[0036] S3 LF refining outside the furnace: During the refining stage outside the furnace, the composition of the molten steel is precisely controlled, deoxidation and alloying are carried out, and the non-metallic inclusions and harmful impurities in the molten steel are further reduced through calcium treatment and soft blowing process, S≤0.003%, and clean molten steel is obtained.

[0037] S4 RH vacuum treatment: This treatment method is used to reduce the hydrogen, oxygen and nitrogen gas contents in molten steel, keep the vacuum degree below 67Pa, and keep the vacuum time for more than 20 minutes.

[0038] S5 slab continuous casting: adopt dynamic light pressure at the end of solidification, electromagnetic stirring, weak cooling in the second cooling stage and correction technology, strictly control the billet drawing speed (0.8-1.0m / min), molten steel temperature (1527-1542℃), and superheat (15-28℃) during continuous casting, use medium carbon protective slag, strictly control liquid level fluctuations, reduce defects such as center segregation and center porosity of continuous casting billets, and continuously cast high-quality slabs with a thickness of 250mm. The slab slow cooling time is more than 36 hours.

[0039] S6 Heating: Heat the slab in a walking beam heating furnace, strictly control the atmosphere in the furnace, ensure the heating temperature and heating time of the slab, especially the soaking time. The heating temperature is controlled at 1210℃~1240℃, the total time in the furnace is greater than 220min, the heating time is greater than 150min, and the soaking time is greater than 30min. Ensure that the alloy elements are fully dissolved and the temperature of the slab is uniform in thickness and width.

[0040] S7 normalizing rolling: rolling adopts two-stage controlled rolling, usually called rough rolling stage and finishing rolling stage. Rough rolling is carried out in 3800mm rough rolling mill, the starting rolling temperature is 1160~1200℃, and the single-pass relative reduction rate is controlled at more than 18% for at least two passes; the finishing rolling starting temperature is ≤930℃, the starting rolling thickness is 2~4 times the finished product thickness, the cumulative reduction is more than 60%, and the final rolling temperature is 800-850℃. After rolling, the steel plate enters the cooling bed for air cooling.

[0041] The present invention is described in detail below in conjunction with practical embodiments.

[0042] Table 1 lists the chemical composition of the examples, and Table 2 lists the rolling process parameters of the examples.

[0043] Table 1 Chemical composition of Examples 1 to 4 of the present invention (wt%)

[0044] Example C Si Mn P S Nb V Ti Als 1 0.162 0.23 1.56 0.010 0.002 0.042 0.039 0.009 0.021 2 0.163 0.22 1.57 0.012 0.003 0.045 0.040 0.012 0.022 3 0.164 0.26 1.60 0.010 0.002 0.046 0.043 0.014 0.021 4 0.171 0.30 1.61 0.011 0.002 0.047 0.043 0.016 0.024

[0045] Table 2 Normalizing rolling process parameters of Examples 1 to 4 of the present invention

[0046]

[0047] The conventional mechanical properties results of the steel plates of Examples 1 to 4 of the present invention are shown in Table 3.

[0048] Table 3 Mechanical properties of steel plates in Examples 1 to 4 of the present invention

[0049]

[0050] As can be seen from the above table, the present invention adopts reasonable chemical composition combined with a specific normalizing rolling process to produce Q460NE open-pit mine equipment high-strength steel plate. The metallographic structure of the steel plate is ferrite + pearlite + a small amount of bainite, and the grain size is 9. The yield strength of the high-strength steel plate for open-pit mine equipment is greater than 460MPa, the tensile strength is 540-720MPa, the elongation is greater than 17%, and the low-temperature impact energy of -40°C is higher than 50J. At the same time, it has good cold forming performance and welding performance.

[0051] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a Q460NE open-pit mining equipment high-strength steel plate with a thickness of less than 40 mm, characterized in that: Ruixia steps include: S1 Hot metal pretreatment: After the hot metal is desulfurized and dephosphorized by KR stirring method, S≤0.005% and P≤0.015% are ensured; S2 converter smelting: The converter smelting stage uses molten iron and high-quality scrap steel that have been pre-treated with desulfurization as raw materials. The molten iron temperature is ≥1260℃. The phosphorus and carbon content are reduced through three technologies: efficient top and bottom re-blowing, automatic furnace gas analysis, and dynamic and static automatic steelmaking, ensuring that the molten steel P≤0.010%, S≤0.004%; S3 LF refining outside the furnace: During the refining stage outside the furnace, the composition of the molten steel is precisely controlled, deoxidation and alloying are carried out, and the non-metallic inclusions and harmful impurities in the molten steel are further reduced through calcium treatment and soft blowing process, S≤0.003%, and clean molten steel is obtained; S4 RH vacuum treatment: reduce the content of hydrogen, oxygen and nitrogen in molten steel, keep the vacuum degree below 67Pa, and keep the vacuum time for more than 20 minutes; S5 slab continuous casting: adopt dynamic soft pressure at the end of solidification, electromagnetic stirring, weak cooling in the second cooling stage and correction technology, strictly control the billet drawing speed during continuous casting at 0.8-1.0m / min, molten steel temperature, and superheat at 15-28℃, use medium carbon protective slag, strictly control liquid level fluctuation, reduce defects such as center segregation and center looseness of continuous casting billet, continuously cast high-quality slab with a thickness of 250mm, and slow cooling time of slab for more than 36 hours; S6 Heating: The slab is heated in a walking beam heating furnace. The atmosphere in the furnace is strictly controlled to ensure the heating temperature and heating time of the slab. The heating temperature is controlled at 1210℃~1240℃. The total time in the furnace is greater than 220min to ensure sufficient solid solution of alloy elements and uniform temperature in the thickness and width of the slab. S7 normalizing rolling: the starting rolling temperature is 1160-1200℃, the relative reduction rate of a single pass is controlled at least 18% for two passes; the starting rolling temperature of the finishing rolling is ≤930℃, the starting rolling thickness is 2-4 times the finished product thickness, the cumulative reduction is more than 60%, and the final rolling temperature is 800-850℃; after rolling, the steel plate enters the cooling bed for air cooling; The chemical composition of the steel plate is C: 0.16-0.18%, Si: 0.20-0.30%, Mn: 1.45-1.65%, P: ≤0.015%, S: ≤0.005%, Nb: 0.04-0.05%, V: 0.035-0.045%, Ti: 0.010-0.020%, Als: 0.017-0.027%, and the balance is Fe and unavoidable impurities.

2. The method for preparing the Q460NE open-pit mining equipment high-strength steel plate with a thickness of less than 40 mm according to claim 1, characterized in that: The chemical composition of the steel plate is C: 0.162%, Si: 0.23%, Mn: 1.56%, P: 0.010%, S: 0.002%, Nb: 0.042%, V: 0.039%, Ti: 0.009%, Als: 0.021% by weight, and the remainder is Fe and inevitable impurities.

3. The method for preparing the Q460NE open-pit mining equipment high-strength steel plate with a thickness of less than 40 mm according to claim 1, characterized in that: The chemical composition of the steel plate is C: 0.163%, Si: 0.22%, Mn: 1.57%, P: 0.012%, S: 0.003%, Nb: 0.045%, V: 0.040%, Ti: 0.012%, Als: 0.022% by weight, and the remainder is Fe and inevitable impurities.

4. The method for preparing the Q460NE open-pit mining equipment high-strength steel plate with a thickness of less than 40 mm according to claim 1, characterized in that: The chemical composition of the steel plate is C: 0.164%, Si: 0.26%, Mn: 1.60%, P: 0.010%, S: 0.002%, Nb: 0.046%, V: 0.043%, Ti: 0.014%, Als: 0.021% by weight, and the remainder is Fe and inevitable impurities.

5. The method for preparing the Q460NE open-pit mining equipment high-strength steel plate with a thickness of less than 40 mm according to claim 1, characterized in that: The chemical composition of the steel plate is C: 0.171%, Si: 0.30%, Mn: 1.61%, P: 0.011%, S: 0.002%, Nb: 0.047%, V: 0.043%, Ti: 0.016%, Als: 0.024% by weight, and the remainder is Fe and inevitable impurities.

6. The method for preparing the Q460NE open-pit mining equipment high-strength steel plate with a thickness of less than 40 mm according to claim 1, characterized in that: The metallographic structure of the steel plate is ferrite + pearlite + a small amount of bainite, and the grain size is level 9.

7. The method for preparing the Q460NE open-pit mining equipment high-strength steel plate with a thickness of less than 40 mm according to claim 1, characterized in that: The high-strength steel plate for open-pit mine equipment has the following properties: yield strength greater than 460 MPa, tensile strength 540-720 MPa, elongation greater than 17%, -40°C low-temperature impact energy greater than 50 J, and good cold forming performance and welding performance.

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