Method for improving corner cracks and middle cracks of plate blank

Abstract

The invention provides a method for improving corner cracks and middle cracks of a plate blank. The method comprises the step of setting two temperature control intervals for the corner temperature of a casting blank. According to the method, the distance between the rollers in the bending section of the casting blank is small, the bulging stress of the casting blank is relatively small, the cooling strength is reduced in the area, the temperature of the bending section of the corner of the casting blank is in a high-temperature section, and corner cracks and middle cracks caused by the influence of bending stress in the bending area are avoided; the cooling strength of the arc-shaped section is increased, so that the temperature of the arc-shaped section entering the straightening area enters the low-temperature area, the middle cracks of the casting blank are effectively reduced, the corners of the casting blank are prevented from entering the brittle area of steel in the straightening area, and corner cracks are avoided; and meanwhile, in cooperation with bending section positioning parameter optimization, straightening area cooling partition and nozzle parameter optimization, the corner temperature of the casting blank is more uniform, corner temperature fluctuation is reduced, and the method has the obvious improvement effect on control over corner cracks and middle cracks of the casting blank.

Description

technical field

[0001] The invention belongs to the technical field of steelmaking, and in particular relates to a method for improving slab corner cracks and middle cracks, more specifically a method for improving slab corner cracks and middle cracks based on dual-temperature process control at the corner of a slab. Background technique

[0002] The main mechanisms for the generation of transverse cracks at the corners are: 1) the coarse austenite grains at the vibration marks at the corners of the slab reduce the high-temperature plasticity of the steel; 2) during the phase transformation process, the second phase particles (A1N, Nb(C, N), VN, BN, etc.) precipitate at the austenite grain boundary, which increases the brittleness of the grain boundary; 3) The slab is bent (inner arc under pressure, outer arc under tension) and straightened (inner arc under tension) during operation. Tension, external arc pressure) and bulging, the slab is just in the low-temperature brittle...

Examples

Embodiment 1

[0077] A medium-high carbon steel billet is prepared by a continuous casting machine, and the composition of the medium-high carbon steel is:

[0078] steel type C(2) Si(2) Mn(2) P(3) S(3) Al S (3)

Medium and high carbon steel (wt%) ≤0.48 ≤0.30 0.50～1.30 ≤0.020 ≤0.010 ≤0.020

[0079] The setting of the continuous casting machine is: the gap between the trunnion on the east side of the bending section and the "U"-shaped seat is measured with a feeler gauge to be 0.2mm, and the gap between the trunnion on the west side and the "U"-shaped seat is measured to be 0.3mm with a feeler gauge;

[0080] Casting speed during pouring is 1.1m / min~1.4m / min, tundish temperature is 1535℃~1545℃;

[0081] Set the target temperature at the corner of the billet in the bending area to 910°C, and use an infrared temperature measuring gun to measure the actual temperature at 900°C to 908°C; set the target temperature at the corner of the billet in the straightening...

Embodiment 2

[0090] A continuous casting machine is used to prepare a boron-containing steel billet, and the composition of the boron-containing steel is:

[0091] steel type C(2) Si(2) Mn(2) P(3) S(3) Al S (3)

B(4) Boron-containing steel (wt%) ≤0.20 ≤0.30 0.30～0.90 ≤0.020 ≤0.010 ≤0.025 ≤0.0020

[0092] The setting of the continuous casting machine is: the gap between the trunnion on the east side of the bending section and the "U"-shaped seat is measured with a feeler gauge to be 0.5mm, and the gap between the trunnion on the west side and the "U"-shaped seat is measured to be 0.6mm with a feeler gauge;

[0093] Casting speed during pouring is 1.1m / min~1.6m / min, tundish temperature is 1545℃~1555℃;

[0094] Set the target temperature at the corner of the billet in the bending area to 900°C, and use an infrared temperature measuring gun to measure the actual temperature at 902°C to 915°C; set the target temperature at the corner of the billet in the stra...

Embodiment 3

[0103]A continuous casting machine is used to prepare microalloyed steel slabs, and the composition of the microalloyed steel is:

[0104]

[0105] The setting of the continuous casting machine is: the gap between the trunnion on the east side of the bending section and the "U"-shaped seat is measured with a feeler gauge to be 0.3mm, and the gap between the trunnion on the west side and the "U"-shaped seat is measured to be 0.35mm with a feeler gauge;

[0106] Casting speed during pouring is 1.0m / min~1.3m / min, tundish temperature is 1540℃~1550℃;

[0107] Set the target temperature at the corner of the billet in the bending area to 920°C, and use an infrared temperature measuring gun to measure the actual temperature at 925°C to 930°C; set the target temperature at the corner of the billet in the straightening area to 700°C, and use an infrared temperature measuring gun to measure the temperature at the entrance of the straightening area. The corner temperature of the slab i...

technical field

[0001] The invention belongs to the technical field of steelmaking, and in particular relates to a method for improving slab corner cracks and middle cracks, more specifically a method for improving slab corner cracks and middle cracks based on dual-temperature process control at the corner of a slab. Background technique

[0002] The main mechanisms for the generation of transverse cracks at the corners are: 1) the coarse austenite grains at the vibration marks at the corners of the slab reduce the high-temperature plasticity of the steel; 2) during the phase transformation process, the second phase particles (A1N, Nb(C, N), VN, BN, etc.) precipitate at the austenite grain boundary, which increases the brittleness of the grain boundary; 3) The slab is bent (inner arc under pressure, outer arc under tension) and straightened (inner arc under tension) during operation. Tension, external arc pressure) and bulging, the slab is just in the low-temperature brittle...

Examples

Embodiment 1

[0077] A medium-high carbon steel billet is prepared by a continuous casting machine, and the composition of the medium-high carbon steel is:

[0078] steel type C(2) Si(2) Mn(2) P(3) S(3) Al S (3)

Medium and high carbon steel (wt%) ≤0.48 ≤0.30 0.50～1.30 ≤0.020 ≤0.010 ≤0.020

[0079] The setting of the continuous casting machine is: the gap between the trunnion on the east side of the bending section and the "U"-shaped seat is measured with a feeler gauge to be 0.2mm, and the gap between the trunnion on the west side and the "U"-shaped seat is measured to be 0.3mm with a feeler gauge;

[0080] Casting speed during pouring is 1.1m / min~1.4m / min, tundish temperature is 1535℃~1545℃;

[0081] Set the target temperature at the corner of the billet in the bending area to 910°C, and use an infrared temperature measuring gun to measure the actual temperature at 900°C to 908°C; set the target temperature at the corner of the billet in the straightening...

Embodiment 2

[0090] A continuous casting machine is used to prepare a boron-containing steel billet, and the composition of the boron-containing steel is:

[0091] steel type C(2) Si(2) Mn(2) P(3) S(3) Al S (3)

B(4) Boron-containing steel (wt%) ≤0.20 ≤0.30 0.30～0.90 ≤0.020 ≤0.010 ≤0.025 ≤0.0020

[0092] The setting of the continuous casting machine is: the gap between the trunnion on the east side of the bending section and the "U"-shaped seat is measured with a feeler gauge to be 0.5mm, and the gap between the trunnion on the west side and the "U"-shaped seat is measured to be 0.6mm with a feeler gauge;

[0093] Casting speed during pouring is 1.1m / min~1.6m / min, tundish temperature is 1545℃~1555℃;

[0094] Set the target temperature at the corner of the billet in the bending area to 900°C, and use an infrared temperature measuring gun to measure the actual temperature at 902°C to 915°C; set the target temperature at the corner of the billet in the stra...

Embodiment 3

[0103]A continuous casting machine is used to prepare microalloyed steel slabs, and the composition of the microalloyed steel is:

[0104]

[0105] The setting of the continuous casting machine is: the gap between the trunnion on the east side of the bending section and the "U"-shaped seat is measured with a feeler gauge to be 0.3mm, and the gap between the trunnion on the west side and the "U"-shaped seat is measured to be 0.35mm with a feeler gauge;

[0106] Casting speed during pouring is 1.0m / min~1.3m / min, tundish temperature is 1540℃~1550℃;

[0107] Set the target temperature at the corner of the billet in the bending area to 920°C, and use an infrared temperature measuring gun to measure the actual temperature at 925°C to 930°C; set the target temperature at the corner of the billet in the straightening area to 700°C, and use an infrared temperature measuring gun to measure the temperature at the entrance of the straightening area. The corner temperature of the slab i...

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