Method for preparing alloy structural steel through rare earth treatment and alloy structural steel

Abstract

The invention discloses a method for preparing alloy structural steel through rare earth treatment and the alloy structural steel. The method comprises the steps that calcium carbide or aluminum is added into LF station entering molten steel for deoxidation treatment, the mass content of FeO in slag is controlled to be smaller than or equal to 1%, and the LF station entering molten steel meets the conditions that [S] is smaller than 0.02%, [P] is smaller than 0.02%, [Als] in the molten steel is smaller than or equal to 200 ppm, and the [Ca] content is smaller than 15 ppm; 3-5 min after LF station entering and slag adjusting, under the condition that the exposed surface of the molten steel surface is larger than 50%, rare earth alloy is added, electrification and soft blowing are carried out, LF station exiting is carried out, and refined molten steel is obtained; performing protective casting on the refined molten steel under protective measures to obtain an alloy structural steel casting blank; and carrying out subsequent processes on the alloy structural steel casting blank to prepare the alloy structural steel. By means of the method, the balance of the transverse performance and the longitudinal performance of the alloy structural steel can be improved, and the alloy structural steel has good mechanical performance.

Description

Technical Field

[0001] The present application belongs to the technical field of steel smelting, and specifically relates to a method for preparing alloy structural steel by using rare earth treatment and the alloy structural steel. Background Art

[0002] Due to factors such as crystal structure and inclusions, alloy structural steel has large differences in the horizontal and vertical directions, which affects the use of materials, especially in alloy structural steel. At present, the performance of domestic alloy steel in the horizontal and vertical directions is generally quite different, the scrap rate in the molding process of structural parts is high, and the service life is short.

[0003] Therefore, improvement is urgently needed.

[0004] To this end, the present invention proposes a method for improving the transverse impact performance of steel, wherein rare earth is added during the refining process to promote the combination of sulfur elements in the steel with rare earth to form rare earth sulfide inclusions, thereby reducing manganese sulfide inclusions and improving the transverse impact performance of the material. In the process, by controlling the timing and amount of rare earth addition, pinning deoxidation treatment, molten steel composition, etc., the transverse impact performance of the steel can be significantly improved, and the ratio of the transverse impact energy to the longitudinal impact energy of the steel is above 0.8. Summary of the invention

[0005] In view of this, the present application provides a method for preparing alloy structural steel using rare earth treatment and alloy structural steel, aiming to provide a preparation method that can improve the lateral and longitudinal properties of alloy structural steel. The present application provides an alloy structural steel with balanced lateral and longitudinal properties and good mechanical properties.

[0006] In a first aspect, an embodiment of the present application provides a method for preparing alloy structural steel by rare earth treatment, comprising:

[0007] Add calcium carbide or aluminum to the LF incoming steel for deoxidation treatment, and control the mass content of FeO in the slag to be ≤1%, wherein the LF incoming steel meets the following requirements: [S] < 0.02%, [P] < 0.02%, [Als] ≤ 200ppm, and [Ca] content < 15ppm;

[0008] 3-5 minutes after LF enters the station and slag is adjusted, rare earth alloy is added and power is turned on and soft blowing is performed under the condition that the exposed surface of the molten steel is greater than 50%, and LF exits the station to obtain refined molten steel;

[0009] The refined molten steel is cast under protective measures to obtain alloy structural steel ingots;

[0010] The alloy structural steel ingot is subjected to subsequent processes to obtain the alloy structural steel.

[0011] According to an embodiment of one aspect of the present application, the chemical composition of the LF incoming steel includes, by mass percentage: C: 0.10%-0.30%, Mn: 0.2%-1.2%, Si: 0.10%-0.50%, S<0.020%, P<0.02%, and the remainder is Fe and unavoidable impurities.

[0012] According to an embodiment of one aspect of the present application, before adding calcium carbide or aluminum to the LF incoming molten steel for deoxidation treatment, the method further includes:

[0013] Open the ladle with 15~30Nm 3 Bottom blowing of protective gas is carried out at a flow rate of / h so that the exposed area of ​​the molten steel surface is 10-30%.

[0014] According to an embodiment of one aspect of the present application, the binary basicity of the slag is 3-6.

[0015] According to an embodiment of one aspect of the present application, 3-5 minutes after the LF enters the station and slag is adjusted, under the condition that the exposed surface of the molten steel surface is greater than 50%, rare earth alloy is added and power is turned on and soft blowing is performed, including:

[0016] 3-5 minutes after LF enters the station to adjust the slag, the pressure is 35-50Nm 3 Bottom blowing of protective gas is carried out at a flow rate of / h, with the exposed surface of the molten steel being greater than 50%, rare earth alloy is added, and power is turned on and soft blowing is carried out.

[0017] According to an embodiment of one aspect of the present application, the rare earth alloy includes one or more rare earth elements of Re, Ce, and La. Based on the total mass of the rare earth alloy, the rare earth alloy includes ≥15% of the rare earth elements.

[0018] According to an embodiment of one aspect of the present application, the mass ratio of the rare earth alloy to the LF incoming molten steel is (0.3 to 0.5):10000.

[0019] According to an embodiment of one aspect of the present application, the gas flow rate of the soft blow is 10-12 Nm 3 / h; the total power-on and soft-blowing time is 20 to 50 minutes.

[0020] According to an embodiment of one aspect of the present application, the refined molten steel is protected and cast under any one or more protective measures of protective slag, long casting nozzle or introducing inert gas around the nozzle to obtain alloy structural steel ingot.

[0021] In the second aspect, an embodiment of the present application provides an alloy structural steel, which is prepared by the preparation method of the first aspect, and the ratio of the transverse impact energy to the longitudinal impact energy of the alloy structural steel is 0.8 to 1; the transverse KV2 impact energy of the alloy structural steel at room temperature is 80J to 120J, and the longitudinal KV2 impact energy of the alloy structural steel at room temperature is 80J to 150J.

[0022] This application has at least the following beneficial effects:

[0023] The method provided in the present application adopts the method of adding rare earths during the refining process to promote the combination of sulfur elements and rare earths in the steel to form rare earth sulfide inclusions, thereby reducing manganese sulfide inclusions, improving and significantly improving the transverse impact performance of the material, and making the ratio of transverse impact energy to longitudinal impact energy of the alloy structural steel above 0.8. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solution of the implementation regulations of this application, the following is a brief introduction to the drawings required for use in the embodiments of this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0025] Figure 1 A micrograph of MnS inclusions of the alloy structural steel according to an example of the present application is shown.

[0026] Figure 2 A micrograph of MnS inclusions of the alloy structural steel of the comparative example of the present application is shown.

[0027] Figure 3 The impact energy curves of the alloy structural steels of the embodiments and comparative examples of the present application are shown. DETAILED DESCRIPTION

[0028] In order to make the application purpose, technical solution and beneficial technical effect of this application clearer, the application is further described in detail below in conjunction with the embodiments. It should be understood that the implementation regulations described in this specification are only for explaining this application, not for limiting this application.

[0029] For simplicity, the present application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unclearly recorded range; and any lower limit can be combined with other lower limits to form an unclearly recorded range, and any upper limit can be combined with any other upper limit to form an unclearly recorded range. In addition, although not clearly recorded, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unclearly recorded range.

[0030] In the description of the present application, it should be noted that, unless otherwise specified, “above” and “below” are inclusive of the number, and the “multiple” in “one or more” means two or more than two.

[0031] The above application content of the present application is not intended to describe each disclosed embodiment or each implementation in the present application. The following description more specifically illustrates exemplary embodiments. In many places throughout the application, guidance is provided through a series of embodiments, and these implementation regulations can be used in various combinations. In each example, enumeration is only used as a representative group and should not be interpreted as exhaustive.

[0032] Preparation method of alloy structural steel

[0033] In a first aspect, an embodiment of the present application provides a method for preparing alloy structural steel by rare earth treatment, comprising:

[0034] Add calcium carbide or aluminum to the LF incoming steel for deoxidation treatment, and control the mass content of FeO in the slag to be ≤1%, wherein the LF incoming steel meets the following requirements: [S] < 0.02%, [P] < 0.02%, [Als] ≤ 200ppm, and [Ca] content < 15ppm;

[0035] 3-5 minutes after LF enters the station and slag is adjusted, rare earth alloy is added and power is turned on and soft blowing is performed under the condition that the exposed surface of the molten steel is greater than 50%, and LF exits the station to obtain refined molten steel;

[0036] The refined molten steel is cast under protective measures to obtain alloy structural steel ingots;

[0037] The alloy structural steel ingot is subjected to subsequent processes to obtain the alloy structural steel.

[0038] According to the embodiments of the present application, the molten steel entering the LF station meets the above requirements, the amount of slag discharged during the converter tapping can be reduced as much as possible, the composition of the molten steel can be controlled, and the subsequent mixing reaction with the rare earth elements in the rare earth alloy can be facilitated to achieve pinning deoxidation, and the sulfur element in the steel is promoted to combine with the rare earth to form rare earth sulfide inclusions, thereby reducing manganese sulfide inclusions, improving and significantly improving the lateral impact performance of the material, and making the ratio of the lateral impact energy to the longitudinal impact energy of the alloy structural steel above 0.8.

[0039] 3-5 minutes after LF enters the slag station, when the exposed surface of the molten steel is greater than 50%, adding rare earth alloy can further improve the rare earth recovery rate, making the rare earth element recovery rate reach 65% or even above 75%.

[0040] In some optional embodiments, after adding the rare earth alloy and conducting power-on and soft blowing, the method further comprises: bottom blowing inert gas to 5-10 Nm3 / h, so that the exposed surface of the molten steel is ≤5%. Such operation reduces the secondary oxidation of the molten steel, but cannot be too small to avoid the soft blowing effect being too weak, so as to promote the sulfur element in the steel to combine with the rare earth to form rare earth sulfide inclusions, thereby reducing manganese sulfide inclusions and improving and significantly improving the lateral impact performance of the material.

[0041] In some optional embodiments, the chemical composition of the LF incoming steel includes, by mass percentage: C: 0.10%-0.30%, Mn: 0.2%-1.2%, Si: 0.10%-0.50%, S<0.020%, P<0.02%, and the remainder is Fe and unavoidable impurities.

[0042] According to the embodiment of the present application, controlling the chemical composition of the molten steel entering the LF station within the above-mentioned range is beneficial to controlling the chemical composition of the alloy structural steel and facilitating the control of the mechanical properties of the alloy structural steel.

[0043] In some optional embodiments, before adding calcium carbide or aluminum to the LF incoming molten steel for deoxidation treatment, the method further comprises:

[0044] Open the ladle with 15~30Nm 3 / h flow rate for bottom blowing of protective gas, so that the exposed area of ​​molten steel surface is 10-30%. Factor, can achieve effective deoxidation treatment, as far as possible to efficiently use calcium carbide or aluminum to achieve deoxidation, to achieve pinning deoxidation, to promote the sulfur element in the steel to combine with rare earth to form rare earth sulfide inclusions, thereby reducing manganese sulfide inclusions, improving and significantly improving the lateral impact performance of the material.

[0045] In some optional embodiments, the binary basicity of the slag is 3 to 6. The binary basicity refers to the mass percentage ratio of CaO to SiO2, that is, w(CaO%):w(CaO%)=(3-6):1.

[0046] In some optional embodiments, the chemical composition of the slag includes, by mass percentage, CaO 55-65%, SiO2 10-20%, Al2O3 3-6%, FeO≤1.0%, and MgO 3-7%. Controlling the binary basicity and chemical composition of the slag can make the slag have better fluidity and desulfurization ability, can make sulfur elements combine with rare earths to form rare earth sulfide inclusions, fully float and remove impurities, can also reduce manganese sulfide inclusions, and improve and significantly improve the lateral impact performance of the material.

[0047] In some optional embodiments, 3-5 minutes after the LF enters the station and slag is adjusted, under the condition that the exposed surface of the molten steel surface is greater than 50%, adding rare earth alloy and conducting power-on and soft blowing include:

[0048] 3-5 minutes after LF enters the station to adjust the slag, the pressure is 35-50Nm 3 The bottom is blown with protective gas at a flow rate of / h to make the exposed surface of the molten steel greater than 50%, rare earth alloy is added, and power is turned on and soft blowing is performed.

[0049] Rare earth alloy is added 3-5 minutes after LF enters the station to adjust the slag. The timing of adding this rare earth alloy can be when the slag has good fluidity and desulfurization ability, and it will not affect the function of rare earth alloy and molten steel. 3 Bottom blowing of protective gas at a flow rate of / h is carried out to make the exposed surface of the molten steel greater than 50%, which can improve the utilization rate or yield of rare earths, reduce manganese sulfide inclusions, and improve and significantly improve the lateral impact performance of the material.

[0050] In some optional embodiments, the rare earth alloy includes one or more rare earth elements of Re, Ce, and La, and based on the total mass of the rare earth alloy, the rare earth alloy includes ≥15% of rare earth elements. Re, Ce, and La can better form rare earth sulfide inclusions with sulfur elements, fully float up to remove impurities, and can also reduce manganese sulfide inclusions. Rare earth alloys including ≥15% of rare earth elements can form rare earth sulfide inclusions, reduce manganese sulfide inclusions, and achieve the purpose of removing impurities.

[0051] In some optional embodiments, the mass ratio of the rare earth alloy to the LF incoming molten steel is (0.3 to 0.5): 10000. By controlling the amount of rare earth alloy added, pinning deoxidation can be better achieved, sufficient floating removal of impurities can be achieved, and manganese sulfide inclusions can be reduced, which can significantly improve the transverse impact performance of steel, so that the ratio of transverse impact energy to longitudinal impact energy of steel is above 0.8.

[0052] In some optional embodiments, the gas flow rate of the soft blow is 10-12 Nm 3 / h; the total time of power-on and soft blowing is 20 to 50 minutes. Therefore, the rare earth elements of the rare earth alloy can react more fully with the sulfur element to generate rare earth sulfide inclusions, and the soft blowing can cause large-sized inclusions to float up, reduce manganese sulfide inclusions, and achieve the purpose of removing impurities.

[0053] In some optional embodiments, the refined molten steel is cast under protective casting under any one or more protective measures such as protective slag, long casting nozzle or inert gas around the nozzle to obtain alloy structural steel ingot, which can prevent secondary oxidation and improve the performance of alloy structural steel.

[0054] Generally speaking, alloy structural steel ingots can be produced by processes such as slab heating → high-pressure water rough descaling → rough rolling → head and tail cutting → high-pressure water fine descaling → fine rolling → layer cooling → coiling → packaging and spray printing.

[0055] Alloy structural steel

[0056] In a second aspect, an embodiment of the present application provides an alloy structural steel, which is prepared by the preparation method of the first aspect.

[0057] In some optional embodiments, the ratio of the transverse impact energy to the longitudinal impact energy of the alloy structural steel is 0.8 to 1; the transverse KV2 impact energy of the alloy structural steel at room temperature is 80J to 120J, and the longitudinal KV2 impact energy of the alloy structural steel at room temperature is 80J to 150J.

[0058] In some optional embodiments, the tensile strength of the alloy structural steel is 970 MPa to 1100 MPa, and the elongation is 13.5% to 25%.

[0059] Example

[0060] The following examples describe the disclosure of the present application in more detail, and these examples are intended for illustrative purposes only, as it will be apparent to those skilled in the art that various modifications and variations may be made within the scope of the disclosure of the present application. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0061] Example 1

[0062] The present application provides a method for preparing alloy structural steel by rare earth treatment, comprising:

[0063] (1) Requirements for molten steel entering the LF station: [S] < 0.02%, [P] < 0.02%, [Als] ≤ 200ppm, [Ca] content < 15ppm, and the amount of slag during converter tapping should be reduced as much as possible; the chemical composition of molten steel entering the LF station is C: 0.12%, Mn: 0.65%, Si: 0.23%, S: 0.019%, P: 0.018%.

[0064] (2) During the LF refining process, Al particles are added to the top slag for deoxidation treatment to control the (FeO) content in the slag to ≤1%; before adding calcium carbide or Al particles, the bottom of the ladle is opened to blow argon to expose 10-30% of the molten steel surface.

[0065] (3) The binary basicity of the slag is controlled at 5, and the chemical composition of the slag is CaO 67.0%, SiO2 13.4%, Al2O3 4.5%, FeO: 0.8%, and MgO 6.5%;

[0066] (4) 3 minutes after LF enters the station to adjust the slag, increase the bottom blowing argon flow rate to ensure that the exposed surface of the molten steel is greater than 50%;

[0067] (5) 3 minutes after the LF enters the station and slag is adjusted, a rare earth alloy is added. The total content of rare earth elements such as Re, Ce and La in the rare earth alloy is 18%. The added amount is based on a mass ratio of rare earth alloy to molten steel of 50 ppm. The rare earth recovery rate is 75%.

[0068] (6) After rare earth is added, the temperature is raised by power, and soft blowing is used to make large inclusions float up. The total power-on and soft blowing time is 21 minutes. Bottom blow inert gas to 8Nm 3 / h, with exposed surface of molten steel ≤5%.

[0069] (7) After leaving the station, the continuous casting process is fully protected to produce alloy structural steel ingots;

[0070] (8) The alloy structural steel ingot is subjected to the following processes: slab heating → high-pressure water rough descaling → rough rolling → head and tail cutting → high-pressure water fine descaling → fine rolling → layer cooling → coiling → packaging, spray printing, etc., to obtain the alloy structural steel.

[0071] Example 2

[0072] The difference between this embodiment and embodiment 1 is that during the LF refining process, calcium carbide or Al particles are added to the top slag for deoxidation, and the (FeO) content in the slag is controlled to be 0.5%.

[0073] Example 3

[0074] The difference between this embodiment and embodiment 1 is that the binary basicity of the slag is 3.

[0075] Example 4

[0076] The difference between this embodiment and embodiment 1 is that: 5 minutes after the LF enters the station to adjust the slag, the slag is adjusted at 40Nm 3 / h flow rate for bottom blowing of argon.

[0077] Example 5

[0078] The difference between this embodiment and embodiment 1 is that after the rare earth alloy is added, the temperature is raised by power-on, the power-on time is 12 minutes, and the soft-blowing time is 13 minutes.

[0079] Example 6

[0080] The difference between this embodiment and embodiment 1 is that after the rare earth alloy is added, the temperature is raised by power-on, the power-on time is 8 minutes, and the soft-blowing time is 8 minutes.

[0081] Example 7

[0082] The difference between this embodiment and embodiment 1 is that the total content of rare earth elements such as Re, Ce and La in the rare earth alloy is 15%, and the added amount is 40 ppm according to the mass ratio of rare earth alloy to molten steel.

[0083] Example 8

[0084] The difference between this embodiment and embodiment 2 is that the total content of rare earth elements such as Re, Ce and La in the rare earth alloy is 15%, and the added amount is 30 ppm according to the mass ratio of rare earth alloy to molten steel.

[0085] Comparative Example 1

[0086] The difference between this embodiment and embodiment 1 is that there is no step (5), that is, no rare earth alloy is added.

[0087] Comparative Example 2

[0088] The difference between this comparative example and Example 2 is that the rare earth alloy is added in step (2), that is, the rare earth alloy is added at the same time as the top slag is deoxidized by calcium carbide or Al particles during the LF refining process.

[0089] Comparative Example 3

[0090] The difference between Comparative Example 3 and Example 1 is that during the LF refining process, calcium carbide or Al particles are added to the top slag for deoxidation treatment, and the (FeO) content in the slag is controlled to be 3%.

[0091] Test Section

[0092] The steel coils of the alloy structural steel obtained in the examples and comparative examples were sampled at their heads (10m from the ends) and tails (10m from the ends) along the length direction; the steel coils of the alloy structural steel obtained in the examples and comparative examples were sampled at the left side (10mm from the edge) and the right side (10mm) of any section of the steel coils along the width direction;

[0093] Tensile strength: Refer to "Tensile test of metallic materials Part 1: Room temperature test method"

[0094] GB / T 228.1 is used for testing.

[0095] Ductility (elongation after fracture A): Tested with reference to "Tensile test of metallic materials Part 1: Room temperature test method" GB / T228.1.

[0096] Impact energy: Tested in accordance with "Charpy pendulum impact test method for metallic materials" GB / T 229.

[0097] Table 1 Test results of alloy structural steel of the embodiment and comparative example.

[0098]

[0099] Note: Each test sample shall be repeated at least three times and the average value shall be taken.

[0100] The above measured performance parameters are taken as average values.

[0101] In addition, the product has been tested for performance. The tensile strength Rm of the alloy structural steel of Example 1 at room temperature is 1040 MPa, the elongation after fracture A is 16.5%, and the KV2 impact (converted to standard sample) at room temperature is 112 J to 120 J.

[0102] Figure 1 The figure shows the MnS morphology of the alloy structural steel of comparative example 1 of the present application. Figure 2 The MnS morphology of the alloy structural steel of Example 1 of the present application is shown. Figure 1 and Figure 2 It can be seen that the method of the present application can refine the grains of alloy structural steel and improve the performance uniformity of the steel plate.

[0103] Figure 3 The impact energy curves of the alloy structural steels of the embodiments and comparative examples of the present application are shown. The alloy structural steels prepared by the method of the present application have relatively balanced transverse and longitudinal impact energy performances.

[0104] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto, and any familiarity with the present technology or replacement should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing alloy structural steel by rare earth treatment, characterized in that: include: Add calcium carbide or aluminum to the LF incoming steel for deoxidation treatment, and control the mass content of FeO in the slag to be ≤1%, wherein the LF incoming steel meets the following requirements: [S] < 0.02%, [P] < 0.02%, [Als] ≤ 200ppm, and [Ca] content < 15ppm; 3-5 minutes after LF enters the station and slag is adjusted, rare earth alloy is added and power is turned on and soft blowing is performed under the condition that the exposed surface of the molten steel is greater than 50%, and LF exits the station to obtain refined molten steel; The refined molten steel is cast under protective measures to obtain alloy structural steel ingots; The alloy structural steel ingot is subjected to subsequent processes to obtain the alloy structural steel.

2. The method according to claim 1, characterized in that The chemical composition of the LF incoming steel liquid includes, by mass percentage, C: 0.10%-0.30%, Mn: 0.2%-1.2%, Si: 0.10%-0.50%, S<0.020%, P<0.02%, and the balance is Fe and unavoidable impurities.

3. The method according to claim 1, characterized in that Before adding calcium carbide or aluminum to the LF incoming molten steel for deoxidation treatment, the method further comprises: Open the ladle with 15~30Nm 3 Bottom blowing of protective gas is carried out at a flow rate of / h so that the exposed area of ​​the molten steel surface is 10-30%.

4. The method according to claim 1, characterized in that: The binary basicity of the slag is 3-6.

5. The preparation method according to claim 1, characterized in that: The method comprises: 3-5 minutes after the LF enters the station and slag is adjusted, adding rare earth alloy and conducting power-on and soft blowing under the condition that the exposed surface of the molten steel is greater than 50%. 3-5 minutes after LF enters the station to adjust the slag, the pressure is 35-50Nm 3 The bottom is blown with protective gas at a flow rate of / h to make the exposed surface of the molten steel greater than 50%, rare earth alloy is added, and power is turned on and soft blowing is performed.

6. The method according to claim 1, characterized in that The rare earth alloy includes one or more rare earth elements selected from Re, Ce and La. Based on the total mass of the rare earth alloy, the rare earth alloy includes ≥15% of the rare earth elements.

7. The method according to claim 1, characterized in that The mass ratio of the total amount of rare earth elements in the rare earth alloy to the LF incoming molten steel is (0.3 to 0.5):10000.

8. The method according to claim 1, characterized in that: The gas flow rate of the soft blow is 10-12 Nm 3 / h; the total power-on and soft-blowing time is 20 to 50 minutes.

9. The method according to claim 1, characterized in that: The refined molten steel is cast under protective casting conditions using any one or more protective measures including protective slag, a long casting nozzle or an inert gas introduced around the nozzle to obtain alloy structural steel ingots.

10. An alloy structural steel, characterized in that: The alloy structural steel is prepared by the preparation method described in any one of claims 1 to 9, wherein the ratio of the transverse impact energy to the longitudinal impact energy is 0.8 to 1; the transverse KV2 impact energy of the alloy structural steel at room temperature is 80J to 120J, and the longitudinal KV2 impact energy of the alloy structural steel at room temperature is 80J to 150J.

Images