Continuous casting method for reducing segregation of 42CrMo steel

Abstract

The invention discloses a continuous casting method for reducing segregation of 42CrMo steel. In the continuous casting process, the pulling speed is controlled to be 0.30-0.32 m / min; the superheat degree of the tundish is 15-25 DEG C; the water quantity of the crystallizer is 5200-5600L / min. Flow; the specific water flow of the secondary cooling area is 0.13-0.15 L / kg; the electromagnetic stirring at the head end is 50-80 A / 2.0-8.0 HZ, the electromagnetic stirring at the secondary cooling is 50-80 A / 2.0-8.0 HZ, and the electromagnetic stirring at the tail end is 100-150 A / 2.0-8.0 HZ. According to the method, by controlling the pulling speed, the superheat degree, the specific water flow and the electromagnetic stirring parameters, carbon segregation of the 42CrMo steel is effectively reduced, and the mechanical properties such as end quenching, tensile strength, yield strength and impact energy of the steel are effectively improved; the carbon segregation of the obtained 42CrMo steel casting blank is less than or equal to 0.02%; after hot rolling, the end quenching value is 52-55 HRC at 9 mm, the end quenching value is 51-54 HRC at 15 mm, the tensile strength is 1293-1399 MPa, the yield strength is 1055-1200 MPa, the ductility is larger than or equal to 16%, the expansion and contraction rate is larger than or equal to 58%, and the U-shaped opening impact value at 23 DEG C is 98.6-107.2 J.

Description

Technical Field

[0001] The present invention belongs to the field of metallurgical technology, and particularly relates to a continuous casting method for reducing segregation of 42CrMo steel. Background Art

[0002] With the development of economy and society, the requirements for the properties of steel are gradually becoming stricter, requiring a narrow range of mechanical properties, high hardness, high wear resistance, good impact toughness, fracture toughness, narrow end-quench requirements, etc. Therefore, it is required to strictly control the element segregation of steel and make it as low as possible.

[0003] Generally, it is required that the C segregation of 42CrMo steel ≤ 0.02%. By using conventional methods to control the slab specifications and reduce segregation, the carbon segregation can only be controlled below ≤ 0.04%, and it is impossible to control the carbon segregation below ≤ 0.02%, thus affecting the properties such as end-quench, tensile strength, yield strength, impact energy, etc. of the steel. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a continuous casting method for reducing segregation of 42CrMo steel so as to control the carbon segregation below ≤ 0.02%.

[0005] To solve the above technical problem, the technical solution adopted by the present invention is: during continuous casting, control: casting speed 0.30 - 0.32 m / min; tundish superheat 15 - 25 °C; mold water volume 5200 - 5600 L / min·strand; specific water volume in secondary cooling zone 0.13 - 0.15 L / kg; electromagnetic stirring at the head end 50 - 80 A / 2.0 - 8.0 HZ, electromagnetic stirring in secondary cooling 50 - 80 A / 2.0 - 8.0 HZ, electromagnetic stirring at the end 100 - 150 A / 2.0 - 8.0 HZ.

[0006] Further, the continuous casting process produces continuous casting billets with a diameter of φ500 - 600 mm.

[0007] Further, the chemical composition and weight percentage of the 42CrMo steel are: C 0.38 - 0.40%, Si 0.22 - 0.28%, Mn 0.55 - 0.60%, P ≤ 0.020%, S ≤ 0.010%, TAl 0.010 - 0.025%, Cr 0.95 - 1.00%, Mo 0.15 - 0.17%, and the balance is iron and unavoidable impurities.

[0008] The beneficial effects of adopting the above technical solutions are as follows: By controlling the casting speed, superheat, specific water volume, and electromagnetic stirring parameters, the present invention effectively reduces the carbon segregation of 42CrMo steel and effectively improves the mechanical properties such as end quenching, tensile strength, yield strength, and impact energy of the steel. The carbon segregation of the 42CrMo steel slab obtained by the present invention is ≤0.02%; after hot rolling, the end quenching values are 9 mm: 52 - 55 HRC, 15 mm: 51 - 54 HRC, the tensile strength is 1293 - 1399 MPa, the yield strength is 1055 - 1200 MPa, the elongation is ≥16%, the shrinkage rate is ≥58%, and the U-notch impact value at 23°C is 98.6 - 107.2 J. Specific Embodiments

[0009] The present invention will be further described in detail below in conjunction with specific embodiments.

[0010] Example 1: The continuous casting method for reducing the segregation of 42CrMo steel adopts the following process.

[0011] During continuous casting, the following are controlled: the casting speed of φ600 mm continuous casting is 0.30 m / min; the superheat in the tundish is 23°C; the water volume in the mold is 5400 L / min·strand; the specific water volume in the secondary cooling zone is 0.14 L / kg; the electromagnetic stirring at the head end is 60 A / 8.0 HZ, the electromagnetic stirring in the secondary cooling is 60 A / 8.0 HZ, and the electromagnetic stirring at the end is 120 A / 8.0 HZ.

[0012] The chemical composition and weight percentage of the 42CrMo steel slab obtained in this example are shown in Table 1, and the macro carbon segregation of the slab is shown in Table 2; after the slab is hot rolled according to the conventional process, the properties such as end quenching, tensile strength, yield strength, and impact energy of the obtained steel are shown in Table 3.

[0013] Example 2: The continuous casting method for reducing the segregation of 42CrMo steel adopts the following process.

[0014] During continuous casting, the following are controlled: the casting speed of φ500 mm continuous casting is 0.32 m / min; the superheat in the tundish is 15°C; the water volume in the mold is 5200 L / min·strand; the specific water volume in the secondary cooling zone is 0.15 L / kg; the electromagnetic stirring at the head end is 80 A / 2.0 HZ, the electromagnetic stirring in the secondary cooling is 70 A / 2.0 HZ, and the electromagnetic stirring at the end is 130 A / 2.0 HZ.

[0015] The chemical composition and weight percentage of the 42CrMo steel slab obtained in this example are shown in Table 1, and the macro carbon segregation of the slab is shown in Table 2; after the slab is hot rolled according to the conventional process, the properties such as end quenching, tensile strength, yield strength, and impact energy of the obtained steel are shown in Table 3.

[0016] Example 3: The continuous casting method for reducing the segregation of 42CrMo steel adopts the following process.

[0017] Control during continuous casting: For a continuous caster with a diameter of φ500mm, the casting speed is 0.32m / min; the superheat in the tundish is 25°C; the water volume in the mold is 5600L / min per strand; the specific water volume in the secondary cooling zone is 0.13L / kg; the electromagnetic stirring at the head end is 50A / 7.0HZ, the electromagnetic stirring in the secondary cooling is 50A / 7.0HZ, and the electromagnetic stirring at the tail end is 100A / 3.0HZ.

[0018] The chemical composition and weight percentage of the 42CrMo steel billets obtained in this example are shown in Table 1, and the macro carbon segregation of the billets is shown in Table 2; after the billets are hot-rolled according to the conventional process, the properties of the obtained steel such as end-quench, tensile strength, yield strength, and impact energy are shown in Table 3.

[0019] Example 4: The continuous casting method for reducing the segregation of 42CrMo steel adopts the following process.

[0020] Control during continuous casting: For a continuous caster with a diameter of φ600mm, the casting speed is 0.31m / min; the superheat in the tundish is 23°C; the water volume in the mold is 5300L / min per strand; the specific water volume in the secondary cooling zone is 0.14L / kg; the electromagnetic stirring at the head end is 70A / 3.0HZ, the electromagnetic stirring in the secondary cooling is 80A / 3.0HZ, and the electromagnetic stirring at the tail end is 150A / 4.0HZ.

[0021] The chemical composition and weight percentage of the 42CrMo steel billets obtained in this example are shown in Table 1, and the macro carbon segregation of the billets is shown in Table 2; after the billets are hot-rolled according to the conventional process, the properties of the obtained steel such as end-quench, tensile strength, yield strength, and impact energy are shown in Table 3.

[0022] Example 5: The continuous casting method for reducing the segregation of 42CrMo steel adopts the following process.

[0023] Control during continuous casting: For a continuous caster with a diameter of φ600mm, the casting speed is 0.31m / min; the superheat in the tundish is 21°C; the water volume in the mold is 5400L / min per strand; the specific water volume in the secondary cooling zone is 0.14L / kg; the electromagnetic stirring at the head end is 80A / 4.0HZ, the electromagnetic stirring in the secondary cooling is 60A / 4.0HZ, and the electromagnetic stirring at the tail end is 140A / 5.0HZ.

[0024] The chemical composition and weight percentage of the 42CrMo steel billets obtained in this example are shown in Table 1, and the macro carbon segregation of the billets is shown in Table 2; after the billets are hot-rolled according to the conventional process, the properties of the obtained steel such as end-quench, tensile strength, yield strength, and impact energy are shown in Table 3.

[0025] Example 6: The continuous casting method for reducing the segregation of 42CrMo steel adopts the following process.

[0026] Control during continuous casting: The casting speed of the φ500mm continuous caster is 0.32 m / min; the superheat of the tundish is 23°C; the water volume in the mold is 5400 L / min·strand; the specific water volume in the secondary cooling zone is 0.13 L / kg; the electromagnetic stirring at the head end is 60 A / 5.0 HZ, the electromagnetic stirring in the secondary cooling is 60 A / 5.0 HZ, and the electromagnetic stirring at the end is 110 A / 6.0 HZ.

[0027] The chemical composition and weight percentage of the 42CrMo steel billets obtained in this example are shown in Table 1, and the macrosegregation of carbon in the billets is shown in Table 2; after hot rolling the billets according to the conventional process, the properties of the obtained steel such as end quenching, tensile strength, yield strength, and impact energy are shown in Table 3.

[0028] Example 7: The continuous casting method for reducing the segregation of 42CrMo steel adopts the following process.

[0029] Control during continuous casting: The casting speed of the φ600mm continuous caster is 0.32 m / min; the superheat of the tundish is 23°C; the water volume in the mold is 5600 L / min·strand; the specific water volume in the secondary cooling zone is 0.15 L / kg; the electromagnetic stirring at the head end is 70 A / 6.0 HZ, the electromagnetic stirring in the secondary cooling is 70 A / 6.0 HZ, and the electromagnetic stirring at the end is 130 A / 7.0 HZ.

[0030] The chemical composition and weight percentage of the 42CrMo steel billets obtained in this example are shown in Table 1, and the macrosegregation of carbon in the billets is shown in Table 2; after hot rolling the billets according to the conventional process, the properties of the obtained steel such as end quenching, tensile strength, yield strength, and impact energy are shown in Table 3.

[0031] Example 8: The continuous casting method for reducing the segregation of 42CrMo steel adopts the following process.

[0032] Control during continuous casting: The casting speed of the φ600mm continuous caster is 0.31 m / min; the superheat of the tundish is 21°C; the water volume in the mold is 5500 L / min·strand; the specific water volume in the secondary cooling zone is 0.14 L / kg; the electromagnetic stirring at the head end is 60 A / 2.0 HZ, the electromagnetic stirring in the secondary cooling is 60 A / 8.0 HZ, and the electromagnetic stirring at the end is 130 A / 6.0 HZ.

[0033] The chemical composition and weight percentage of the 42CrMo steel billets obtained in this example are shown in Table 1, and the macrosegregation of carbon in the billets is shown in Table 2; after hot rolling the billets according to the conventional process, the properties of the obtained steel such as end quenching, tensile strength, yield strength, and impact energy are shown in Table 3.

[0034] Table 1: Chemical composition content of 42CrMo steel in each example (wt%)

[0035] In Table 1, the balance is iron and unavoidable impurities.

[0036] Table 2: Analysis of the macrosegregation of carbon in the 42CrMo steel continuous casting billets of each example, carbon content (wt%)

[0037] Table 3: Test results of the mechanical properties of the 42CrMo steel after hot rolling in each example 。

Claims

1. A continuous casting method for reducing segregation of 42CrMo steel, characterized in that: Control during continuous casting: casting speed 0.30~0.32m / min; tundish superheat 15~25℃; crystallizer water volume 5200~5600L / min·flow; secondary cooling zone water volume 0.13~0.15L / kg; head end electromagnetic stirring 50~80A / 2.0~8.0HZ, secondary cooling electromagnetic stirring 50~80A / 2.0~8.0HZ, end end electromagnetic stirring 100~150A / 2.0~8.0HZ.

2. A continuous casting method for reducing segregation of 42CrMo steel according to claim 1, characterized in that: The continuous casting process produces continuous casting billets of φ500-600 mm.

3. A continuous casting method for reducing segregation of 42CrMo steel according to claim 1 or 2, characterized in that: The chemical composition and weight percentage of the 42CrMo steel are: C 0.38-0.40%, Si 0.22-0.28%, Mn 0.55-0.60%, P≤0.020%, S≤0.010%, TAl 0.010-0.025%, Cr 0.95-1.00%, Mo 0.15-0.17%, and the balance is iron and inevitable impurities.

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