Low-compression-ratio Q460C-grade angle steel and production method thereof

Abstract

The invention discloses Q460C-grade angle steel with a low compression ratio and a production method of the Q460C-grade angle steel. The angle steel comprises the following chemical components in percentage by weight: 0.17 to 0.20 percent of C, 0.30 to 0.40 percent of Si, 1.35 to 1.55 percent of Mn, 0.070 to 0.085 percent of V, less than or equal to 0.020 percent of P, less than or equal to 0.020 percent of S, 0.41 to 0.46 percent of CEV, 0.0120 to 0.0150 percent of N and the balance of Fe and inevitable impurities. The production method comprises the steps of KR pretreatment, converter smelting, LF refining, continuous casting, heating and profile steel rolling. The Q460C-grade angle steel with the compression ratio ranging from 4.7 to 6.0 can be produced, the yield strength ReH of the angle steel is larger than or equal to 470 MPa, the tensile strength Rm is larger than or equal to 630 MPa and smaller than or equal to 680 MPa, the impact property KV2 at the temperature of 0 DEG C is larger than or equal to 34 J, and the percentage elongation after fracture A is larger than or equal to 18%.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a low compression ratio Q460C grade angle steel and a production method thereof. Background Art

[0002] With the development of economy and technology, angle steel has been applied to various fields of national economy with its advantages of economic applicability, environmental friendliness and fast construction, and has received extensive attention from various industries. With the development of the industry, Q355C and Q420C grade angle steel can no longer meet all needs, and it is necessary to develop angle steel products with higher strength levels.

[0003] Especially in recent years, with the rapid development of China's economy, the demand for angle steel in the power industry has increased. Towers, as an important part of power transmission and transformation lines, are generally composed of angle steels of various specifications. Therefore, the more specifications that can be produced when receiving orders, the stronger the order-taking capacity. Generally speaking, the larger the specifications of angle steel, the higher the economic benefits; for this, steel companies need to develop production line capabilities, give full play to equipment capabilities, improve market competitiveness, and produce angle steels of various specifications to the maximum extent. Summary of the invention

[0004] The purpose of the present invention is to provide a low compression ratio Q460C grade angle steel and a production method thereof, by adopting precise composition control and inclusion control, optimizing the toughness of the ingot and improving the impact toughness; by optimizing the electromagnetic stirring of the crystallizer, improving the internal quality of the ingot, reducing rolling defects under low compression ratio conditions, and realizing the production of Q460C grade angle steel in the compression ratio range of 4.7-6.0.

[0005] To achieve the above purpose, the technical solution of the present invention is as follows: A low compression ratio Q460C grade angle steel, whose chemical composition calculated by weight percentage is: C: 0.17-0.20%, Si: 0.30-0.40%, Mn: 1.35-1.55%, V: 0.070-0.085%, P≤0.020%, S≤0.020%, CEV: 0.41-0.46%, N: 0.0120-0.0150%, and the balance is Fe and unavoidable impurities.

[0006] The production method of the low compression ratio Q460C grade angle steel of the present invention comprises KR pretreatment, converter smelting, LF refining, continuous casting, heating and section steel rolling.

[0007] Furthermore, the KR pretreatment of the present invention uses lime powder + fluorite powder as a desulfurizing agent, stirring desulfurization, the molten iron temperature is ≥1280°C, and the S of the molten iron entering the furnace is ≤0.020%.

[0008] Furthermore, in the converter smelting of the present invention, the converter double blowing adopts argon mode, and silicon-aluminum alloy deoxidation is added in sequence when 1 / 4 of the converter is tapped; argon is used as the ladle bottom blowing gas source; and the converter slag basicity is 3.0-3.8.

[0009] Furthermore, in the converter smelting of the present invention, the aluminum content of the silicon-aluminum alloy is 35.0-38.0%, and the silicon content is 15.0-18.0%.

[0010] Furthermore, in the LF refining described in the present invention, 75 silicon carbide is used for diffusion deoxidation to produce reducing slag, the reducing slag is kept for 10 to 15 minutes, the FeO content in the slag is ≤1.0%, the soft blowing time is 8 to 12 minutes, the nitrogen content in the molten steel after soft blowing is: 0.0120 to 0.0150%, and the active oxygen content of the steel grade is 0.0022 to 0.0035%.

[0011] Furthermore, in the LF refining of the present invention, the SiC content in the 75 silicon carbide is 73.0-76.0%, and the free carbon content is 4.0-8.0%.

[0012] Furthermore, the continuous casting of the present invention adopts large ladle long shroud protection pouring, uses low-carbon middle ladle covering agent, and the continuous casting furnace superheat is 15-45°C; crystallizer electromagnetic stirring is adopted, and the parameters are set to 350A, 3-4Hz, and continuous.

[0013] Furthermore, in the heating of the present invention, the temperature of the soaking section of the heating furnace is 1180-1250°C.

[0014] Furthermore, the steel section rolling of the present invention adopts a post-furnace high-pressure water descaling process, with a descaling pressure of 15-25 MPa, a rolling temperature of 1080-1120° C., and a rolling compression ratio of 4.7-6.0.

[0015] The inventive principle and beneficial effects of the present invention are: The present invention improves the plasticity of steel by optimizing the composition design and adopting precise nitrogen content control technology; by adjusting the alloy composition and precipitation strengthening, the impact performance of angle steel under low compression ratio range of 4.7-6.0 is improved, and the impact performance KV under 0°C condition is achieved. 2 ≥34J. By optimizing the electromagnetic stirring parameters, the surface quality and internal quality of the ingot are improved, the surface defects of the angle steel are eliminated, and the upper yield strength ReH≥470MPa, the tensile strength 630 MPa≤Rm≤680 MPa, and the elongation after fracture A≥18% are achieved.

[0016] The present invention adopts low compression ratio ingot rolling technology to give full play to the potential of the equipment, expand the rolling specifications of angle steel without changing the continuous casting section, improve the order-taking production capacity of angle steel series products with a larger range and more specifications, realize the production of Q460C grade angle steel, and improve market competitiveness and product profitability. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is further described in detail below through embodiments. Example 1

[0018] The chemical composition of the low compression ratio Q460C grade angle steel in this embodiment is calculated by weight percentage as follows: C 0.17%, Si 0.30%, Mn 1.35%, V 0.072%, P 0.013%, S 0.006%, CEV 0.41%, N 0.0138%, and the balance is Fe and unavoidable impurities; the production method thereof comprises the following steps: 1) KR pretreatment: lime powder + fluorite powder are used as desulfurizers, the ratio of lime powder to fluorite powder is 9:1, stirring desulfurization, molten iron temperature is 1280℃, and the S content of molten iron after molten iron pretreatment is: 0.020%.

[0019] 2) Converter smelting: The converter double blowing adopts argon mode, and silicon-aluminum alloy is added in sequence for deoxidation when 1 / 4 of the converter is discharged. The aluminum content of the silicon-aluminum alloy is 35.0%, and the silicon content is 18.0%. Argon is used as the gas source for ladle bottom blowing; the converter slag basicity is 3.0.

[0020] 3) LF refining: 75% silicon carbide is used for diffusion deoxidation to produce reducing slag, wherein the SiC content of the 75% silicon carbide is 73.0%, the free carbon content is 8.0%, the reducing slag is kept for 15 minutes, the FeO content in the slag is 1.0%, and the soft blowing time is 12 minutes. The nitrogen content in the outgoing steel is 0.0138%, and the outgoing oxygen content is 0.0035%.

[0021] 4) Continuous casting: Use large ladle with long nozzle for protection casting, use low-carbon middle ladle covering agent, and the continuous casting furnace overheating degree is 15°C. The continuous casting billet is 165mm*280mm rectangular billet; use crystallizer electromagnetic stirring, and the parameters are set to 350A, 3Hz, and continuous.

[0022] 5) Heating: The temperature of the heating furnace soaking section is 1180℃.

[0023] 6) Steel rolling: the descaling pressure after the furnace is 15Mpa, the rolling temperature is 1080℃; the specifications of the rolled angle steel are 200mm*200mm*26mm equal-leg angle steel, and the compression ratio is 4.7.

[0024] The Q460C grade angle steel of this embodiment has an upper yield strength of 483 MPa, a tensile strength of 617 MPa, an impact resistance of 111 J at 0° C., and an elongation after fracture of 25.5%. Example 2

[0025] The chemical composition of the low compression ratio Q460C grade angle steel in this embodiment is calculated by weight percentage as follows: C 0.17%, Si 0.40%, Mn 1.55%, V 0.070%, P 0.020%, S 0.008%, CEV 0.45%, N 0.0120%, and the balance is Fe and unavoidable impurities; the production method thereof comprises the following steps: 1) KR pretreatment: lime powder + fluorite powder are used as desulfurizers, the ratio of lime powder to fluorite powder is 9:1, stirring desulfurization, molten iron temperature is 1351℃, and the S content of molten iron after molten iron pretreatment is 0.016%.

[0026] 2) Converter smelting: The converter double blowing adopts argon mode, and silicon-aluminum alloy is added in sequence for deoxidation when 1 / 4 of the converter is discharged. The aluminum content of the silicon-aluminum alloy is 38.0%, and the silicon content is 15.0%. Argon is used as the gas source for ladle bottom blowing; the converter slag basicity is 3.8.

[0027] 3) LF refining: 75% silicon carbide is used for diffusion deoxidation to produce reducing slag, wherein the SiC content of the 75% silicon carbide is 76.0%, the free carbon content is 4.0%, the reducing slag is kept for 10 minutes, the FeO content in the slag is 0.66%, and the soft blowing time is 8 minutes. The nitrogen content in the outgoing steel is 0.0120%, and the outgoing oxygen content is 0.0022%.

[0028] 4) Continuous casting: Use large ladle with long nozzle for protection casting, use low-carbon middle ladle covering agent, and the continuous casting furnace overheating temperature is 45°C. The continuous casting billet is 165mm*165mm rectangular billet; use crystallizer electromagnetic stirring, and the parameters are set to 350A, 4Hz, and continuous.

[0029] 5) Heating: The temperature of the heating furnace soaking section is 1250℃.

[0030] 6) Steel section rolling: the descaling pressure after the furnace is 25Mpa, the rolling temperature is 1120℃; the specifications of the rolled angle steel are 150mm*150mm*16mm equal-leg angle steel, and the compression ratio is 6.0.

[0031] The Q460C grade angle steel of this embodiment has an upper yield strength of 511 MPa, a tensile strength of 653 MPa, an impact resistance of 50 J at 0° C., and an elongation after fracture of 25%. Example 3

[0032] The chemical composition of the low compression ratio Q460C grade angle steel in this embodiment is calculated by weight percentage as follows: C 0.20%, Si 0.33%, Mn 1.44%, V 0.085%, P 0.012%, S 0.020%, CEV 0.46%, N 0.0150%, and the balance is Fe and unavoidable impurities; the production method thereof comprises the following steps: 1) KR pretreatment: lime powder + fluorite powder are used as desulfurizers, the ratio of lime powder to fluorite powder is 9:1, stirring desulfurization, molten iron temperature is 1295℃, and the S content of molten iron after molten iron pretreatment is 0.008%.

[0033] 2) Converter smelting: The converter double blowing adopts argon mode, and silicon-aluminum alloy is added in sequence for deoxidation when 1 / 4 of the steel is discharged from the converter. The aluminum content of the silicon-aluminum alloy is 35.9%, and the silicon content is 16.5%. Argon is used as the gas source for the bottom blowing of the ladle; the basicity of the converter slag is 3.2.

[0034] 3) LF refining: 75% silicon carbide is used for diffusion deoxidation to produce reducing slag, wherein the SiC content of the 75% silicon carbide is 74.3%, the free carbon content is 5.7%, the reducing slag is kept for 11 minutes, the FeO content in the slag is 0.41%, and the soft blowing time is 10 minutes. The nitrogen content in the outgoing steel is 0.0150%, and the outgoing oxygen content is 0.0029%.

[0035] 4) Continuous casting: Use large ladle with long nozzle for protection casting, use low-carbon middle ladle covering agent, and the continuous casting furnace overheating degree is 23°C. The continuous casting billet is 165mm*280mm rectangular billet; use crystallizer electromagnetic stirring, and the parameters are set to 350A, 3Hz, and continuous.

[0036] 5) Heating: The temperature of the heating furnace soaking section is 1200℃.

[0037] 6) Steel rolling: descaling pressure after furnace is 20Mpa, rolling temperature is 1091℃; the specifications of rolled angle steel are 200mm*200mm*24mm equal-leg angle steel, and the compression ratio is 5.1.

[0038] The Q460C grade angle steel of this embodiment has an upper yield strength of 525 MPa, a tensile strength of 680 MPa, an impact resistance of 88 J at 0° C., and an elongation after fracture of 24.8%. Example 4

[0039] The chemical composition of the low compression ratio Q460C grade angle steel in this embodiment is calculated by weight percentage as follows: C 0.18%, Si 0.34%, Mn 1.38%, V 0.075%, P 0.016%, S 0.014%, CEV 0.43%, N 0.0131%, and the balance is Fe and unavoidable impurities; the production method thereof comprises the following steps: 1) KR pretreatment: lime powder + fluorite powder are used as desulfurizers, the ratio of lime powder to fluorite powder is 9:1, stirring desulfurization, molten iron temperature is 1311℃, and the S content of molten iron after molten iron pretreatment is 0.016%.

[0040] 2) Converter smelting: The converter double blowing adopts argon mode, and silicon aluminum alloy is added in sequence for deoxidation when 1 / 4 of the converter is discharged. The aluminum content of the silicon aluminum alloy is 37.7%, and the silicon content is 16.9%. Argon is used as the gas source for the bottom blowing of the ladle; the basicity of the converter slag is 3.5.

[0041] 3) LF refining: 75% silicon carbide is used for diffusion deoxidation to produce reducing slag, wherein the SiC content of the 75% silicon carbide is 73.6%, the free carbon content is 6.3%, the reducing slag is kept for 12 minutes, the FeO content in the slag is 0.69%, and the soft blowing time is 8 minutes. The nitrogen content in the outgoing steel is 0.0131%, and the outgoing oxygen content is 0.0027%.

[0042] 4) Continuous casting: Use large ladle with long nozzle for protection casting, use low-carbon middle ladle covering agent, and the continuous casting furnace overheating degree is 27°C. The continuous casting billet is 165mm*225mm rectangular billet; use crystallizer electromagnetic stirring, and the parameters are set to 350A, 4Hz, and continuous.

[0043] 5) Heating: The temperature of the heating furnace soaking section is 1210℃.

[0044] 6) Steel rolling: descaling pressure after furnace is 20Mpa, rolling temperature is 1109℃; the specifications of rolled angle steel are 200mm*200mm*16mm equal-leg angle steel, and the compression ratio is 5.4.

[0045] The Q460C grade angle steel of this embodiment has an upper yield strength of 492 MPa, a tensile strength of 657 MPa, an impact resistance of 61 J at 0° C., and an elongation after fracture of 23.6%. Example 5

[0046] The chemical composition of the low compression ratio Q460C grade angle steel in this embodiment is calculated by weight percentage as follows: C 0.18%, Si 0.36%, Mn 1.36%, V 0.074%, P 0.011%, S 0.013%, CEV 0.43%, N 0.0137%, and the balance is Fe and unavoidable impurities; the production method thereof comprises the following steps: 1) KR pretreatment: lime powder + fluorite powder are used as desulfurizers, the ratio of lime powder to fluorite powder is 9:1, stirring desulfurization, molten iron temperature is 1364℃, and the S content of molten iron after molten iron pretreatment is: 0.017%.

[0047] 2) Converter smelting: The converter double blowing adopts argon mode, and silicon-aluminum alloy is added in sequence for deoxidation when 1 / 4 of the steel is discharged from the converter. The aluminum content of the silicon-aluminum alloy is 36.5%, and the silicon content is 17.1%. Argon is used as the gas source for the bottom blowing of the ladle; the basicity of the converter slag is 3.2.

[0048] 3) LF refining: 75% silicon carbide is used for diffusion deoxidation to produce reducing slag, wherein the SiC content of the 75% silicon carbide is 73.0%, the free carbon content is 7.9%, the reducing slag is kept for 12 minutes, the FeO content in the slag is 0.55%, and the soft blowing time is 10 minutes. The nitrogen content in the outgoing steel is 0.0137%, and the outgoing oxygen content is 0.0026%.

[0049] 4) Continuous casting: Use large ladle with long nozzle for protection casting, use low-carbon middle ladle covering agent, and the continuous casting furnace overheating temperature is 38°C. The continuous casting billet is 180mm*180mm rectangular billet; use crystallizer electromagnetic stirring, and the parameters are set to 350A, 3Hz, and continuous.

[0050] 5) Heating: The temperature of the heating furnace soaking section is 1190℃.

[0051] 6) Steel section rolling: the descaling pressure after the furnace is 20Mpa, the rolling temperature is 1105℃; the specifications of the rolled angle steel are 200mm*200mm*16mm equal-leg angle steel, and the compression ratio is 4.7.

[0052] The Q460C grade angle steel of this embodiment has an upper yield strength of 484 MPa, a tensile strength of 630 MPa, an impact resistance of 59 J at 0° C., and an elongation after fracture of 23.3%. Example 6

[0053] The chemical composition of the low compression ratio Q460C grade angle steel in this embodiment is calculated by weight percentage as follows: C 0.19%, Si 0.32%, Mn 1.51%, V 0.083%, P 0.015%, S 0.011%, CEV 0.46%, N 0.0146%, and the balance is Fe and unavoidable impurities; the production method thereof comprises the following steps: 1) KR pretreatment: lime powder + fluorite powder are used as desulfurizers, the ratio of lime powder to fluorite powder is 9:1, stirring desulfurization, molten iron temperature is 1337℃, and the S content of molten iron after molten iron pretreatment is 0.013%.

[0054] 2) Converter smelting: The converter double blowing adopts argon mode, and silicon aluminum alloy is added in sequence for deoxidation when 1 / 4 of the converter is discharged. The aluminum content of the silicon aluminum alloy is 35.1%, and the silicon content is 17.7%. Argon is used as the gas source for the bottom blowing of the ladle; the basicity of the converter slag is 3.7.

[0055] 3) LF refining: 75% silicon carbide is used for diffusion deoxidation to produce reducing slag, wherein the SiC content of the 75% silicon carbide is 73.6%, the free carbon content is 4.9%, the reducing slag is kept for 14 minutes, the FeO content in the slag is 0.73%, and the soft blowing time is 11 minutes. The nitrogen content in the outgoing steel is 0.0146%, and the outgoing oxygen content is 0.0033%.

[0056] 4) Continuous casting: Use large ladle with long nozzle for protection casting, use low-carbon middle ladle covering agent, and the continuous casting furnace overheating degree is 41°C. The continuous casting billet is 180mm*180mm rectangular billet; use crystallizer electromagnetic stirring, and the parameters are set to 350A, 3Hz, and continuous.

[0057] 5) Heating: The temperature of the heating furnace soaking section is 1235℃.

[0058] 6) Steel section rolling: the descaling pressure after the furnace is 23Mpa, the rolling temperature is 1164℃; the specifications of the rolled angle steel are 200mm*200mm*16mm equal-leg angle steel, and the compression ratio is 5.7.

[0059] The Q460C grade angle steel of this embodiment has an upper yield strength of 522 MPa, a tensile strength of 680 MPa, an impact resistance of 34 J at 0° C., and an elongation after fracture of 18%.

[0060] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A low compression ratio Q460C grade angle steel, characterized in that: The chemical composition of the angle steel is calculated by weight percentage as follows: C 0.17-0.20%, Si 0.30-0.40%, Mn 1.35-1.55%, V 0.070-0.085%, P≤0.020%, S≤0.020%, CEV 0.41-0.46%, N 0.0120-0.0150%, and the balance is Fe and unavoidable impurities.

2. The low compression ratio Q460C grade angle steel according to claim 1, characterized in that: The angle steel has an upper yield strength ReH≥470MPa, a tensile strength of 630MPa≤Rm≤680MPa, an impact performance at 0°C KV2≥34J, and an elongation after fracture A≥18%.

3. A method for producing the low compression ratio Q460C grade angle steel according to claim 1 or 2, characterized in that: Including KR pretreatment, converter smelting, LF refining, continuous casting, heating and section steel rolling.

4. The method for producing low compression ratio Q460C grade angle steel according to claim 3, characterized in that: The KR pretreatment uses lime powder + fluorite powder as a desulfurizing agent, stirring desulfurization, the molten iron temperature is ≥1280°C, and the S of the molten iron entering the furnace is ≤0.020%.

5. The method for producing low compression ratio Q460C grade angle steel according to claim 3, characterized in that: In the converter smelting, the converter re-blowing adopts argon mode, and silicon-aluminum alloy is added in sequence for deoxidation when 1 / 4 of the converter is tapped; argon is used as the ladle bottom blowing gas source; and the converter slag basicity is 3.0-3.

8.

6. The method for producing low compression ratio Q460C grade angle steel according to claim 3, characterized in that: The LF refining adopts 75 silicon carbide for diffusion deoxidation to produce reducing slag, the reducing slag is kept for 10 to 15 minutes, the FeO content in the slag is ≤1.0%, the soft blowing time is 8 to 12 minutes, the nitrogen content in the molten steel after soft blowing is: 0.0120 to 0.0150%, and the active oxygen content of the steel grade is 0.0022 to 0.0035%.

7. According to the method for producing a low compression ratio Q460C grade angle steel according to claim 3, it is characterized in that: The continuous casting adopts large ladle with long shroud for protection pouring, uses low-carbon middle ladle covering agent, and the continuous casting furnace overheating degree is 15-45° C.; and adopts crystallizer electromagnetic stirring.

8. The method for producing low compression ratio Q460C grade angle steel according to claim 3, characterized in that: The heating is carried out at a temperature of 1180-1250°C in the soaking zone of the heating furnace.

9. The method for producing low compression ratio Q460C grade angle steel according to claim 3, characterized in that: The steel section rolling adopts a post-furnace high-pressure water descaling process, the descaling pressure is 15-25Mpa, and the starting rolling temperature is 1080-1120°C.

10. The method for producing low compression ratio Q460C grade angle steel according to claim 3, characterized in that: The steel section is rolled with a rolling compression ratio of 4.7-6.0.