Internal quality control method of 30Mn tube bloom steel cast blanks

Abstract

The invention relates to the field of ferrous metallurgy and particularly relates to an internal quality control method of 30Mn tube bloom steel cast blanks. The technical problem to be solved is to provide an internal quality control method of 30Mn tube bloom steel cast blanks; the method is capable of effectively controlling crack defects of cast blanks, effectively improving solidification structures of the cast blanks and achieving the internal quality control. The method comprises the following steps: a, firstly carrying out a converter smelting process; b, secondly carrying out an LF furnace molten steel refining process; and c, finally carrying out section continuous casting process, wherein electromagnetic stirring parameters of a crystallizer are characterized in that the stirring current is 300-400A, and the frequency is 2-4Hz; electromagnetic stirring parameters of a solidification end are characterized in that the stirring current is 100-200A, and the frequency is 4.0-7.0Hz; the superheat degree is controlled to be 25-35 DEG C; the pulling rate is controlled to be 0.70-1.00m / min; the cooling rate of the crystallizer is controlled to be 2400-2500L / min; the specific special water flow rate of secondary cooling is controlled to be 0.21-0.30 / kg steel. The internal quality control method of the 30Mn tube bloom steel cast blanks is especially applicable to the internal quality control process of large-size 30Mn tube bloom steel cast blanks produced by phi 350mm section.

Description

technical field

[0001] The invention relates to the field of iron and steel metallurgy, in particular to a method for controlling the internal quality of a 30Mn round billet steel billet. Background technique

[0002] For 30Mn billet steel, the medium carbon and 1.28%-1.42% manganese content in the steel composition itself determine that the slab crack sensitivity is strong in the continuous casting production process. Mainly due to the low thermal conductivity and large linear expansion coefficient of the steel type, large internal stress is generated during cooling and solidification, and surface crack defects are prone to occur; moreover, due to the relatively large cross-section of the billet and the round billet, its specific surface area is smaller. The billet has lower heat transfer efficiency and slow solidification and cooling. After the billet shell is formed, the heat transfer efficiency will decrease, which will lead to a larger radial temperature gradient in the...

Examples

Embodiment 1

[0015] A steelmaking plant adopts 120t converter smelting → LF furnace refining → four-machine four-stream casting machine φ350mm section continuous casting to produce 30Mn round tube billet. At the end of converter blowing, the end point carbon is controlled at 0.10%, and the end point temperature is controlled at 1675°C; the small platform is fed with 1.7m / t steel into the aluminum wire for deoxidation; the outbound composition of the small platform is controlled as: [C]0.27%, [Si] 0.22%, [Mn] 1.24%, [P] 0.013%; after deoxidation and alloying, soft argon blowing and stirring were carried out, the stirring time was 3.7min, and the molten steel did not appear exposed during stirring.

[0016] When the molten steel arrives at the LF refining furnace, the molten steel fluctuates slightly after argon blowing, and there is no major turning phenomenon. After refining, Ti is added at 0.026% of the weight of the molten steel; 7.5 minutes of soft blowing and stirring were carried out ...

Embodiment 2

[0020] A steelmaking plant adopts 120t converter smelting → LF furnace refining → four-machine four-stream casting machine φ350mm section continuous casting to produce 30Mn round tube billet. At the end of the converter blowing, the end point carbon is controlled at 0.15%, and the end point temperature is controlled at 1673°C; the small platform is fed with 1.5m / t steel into the aluminum wire for deoxidation; the outbound composition of the small platform is controlled as: [C]0.25%, [Si] 0.25%, [Mn] 1.20%, [P] 0.013%; after deoxidation and alloying, soft argon blowing and stirring were carried out, the stirring time was 4.5min, and the molten steel did not appear exposed during stirring.

[0021] When the molten steel reaches the LF refining furnace, the molten steel fluctuates slightly after argon blowing, and there is no big turning phenomenon. After the refining is completed, Ti is added at 0.020% of the weight of the molten steel; After feeding the line, 7.3 minutes of sof...

Embodiment 3

[0025] A steelmaking plant adopts 120t converter smelting → LF furnace refining → four-machine four-stream casting machine φ350mm section continuous casting to produce 30Mn round tube billet. At the end of converter blowing, the end point carbon is controlled at 0.05%, and the end point temperature is controlled at 1680°C; the small platform is fed with 2.0m / t steel into the aluminum wire for deoxidation; the outbound composition of the small platform is controlled as: [C]0.30%, [Si] 0.18%, [Mn] 1.30%, [P] 0.009%; after deoxidation and alloying, soft argon blowing and stirring were carried out, and the stirring time was 4.0min, and the molten steel did not appear exposed during stirring.

[0026] When the molten steel reaches the LF refining furnace, the molten steel fluctuates slightly after argon blowing, and there is no big turning phenomenon. After refining, Ti is added at 0.035% of the weight of the molten steel; After feeding the line, soft blowing and stirring were perf...

technical field

[0001] The invention relates to the field of iron and steel metallurgy, in particular to a method for controlling the internal quality of a 30Mn round billet steel billet. Background technique

[0002] For 30Mn billet steel, the medium carbon and 1.28%-1.42% manganese content in the steel composition itself determine that the slab crack sensitivity is strong in the continuous casting production process. Mainly due to the low thermal conductivity and large linear expansion coefficient of the steel type, large internal stress is generated during cooling and solidification, and surface crack defects are prone to occur; moreover, due to the relatively large cross-section of the billet and the round billet, its specific surface area is smaller. The billet has lower heat transfer efficiency and slow solidification and cooling. After the billet shell is formed, the heat transfer efficiency will decrease, which will lead to a larger radial temperature gradient in the...

Examples

Embodiment 1

[0015] A steelmaking plant adopts 120t converter smelting → LF furnace refining → four-machine four-stream casting machine φ350mm section continuous casting to produce 30Mn round tube billet. At the end of converter blowing, the end point carbon is controlled at 0.10%, and the end point temperature is controlled at 1675°C; the small platform is fed with 1.7m / t steel into the aluminum wire for deoxidation; the outbound composition of the small platform is controlled as: [C]0.27%, [Si] 0.22%, [Mn] 1.24%, [P] 0.013%; after deoxidation and alloying, soft argon blowing and stirring were carried out, the stirring time was 3.7min, and the molten steel did not appear exposed during stirring.

[0016] When the molten steel arrives at the LF refining furnace, the molten steel fluctuates slightly after argon blowing, and there is no major turning phenomenon. After refining, Ti is added at 0.026% of the weight of the molten steel; 7.5 minutes of soft blowing and stirring were carried out ...

Embodiment 2

[0020] A steelmaking plant adopts 120t converter smelting → LF furnace refining → four-machine four-stream casting machine φ350mm section continuous casting to produce 30Mn round tube billet. At the end of the converter blowing, the end point carbon is controlled at 0.15%, and the end point temperature is controlled at 1673°C; the small platform is fed with 1.5m / t steel into the aluminum wire for deoxidation; the outbound composition of the small platform is controlled as: [C]0.25%, [Si] 0.25%, [Mn] 1.20%, [P] 0.013%; after deoxidation and alloying, soft argon blowing and stirring were carried out, the stirring time was 4.5min, and the molten steel did not appear exposed during stirring.

[0021] When the molten steel reaches the LF refining furnace, the molten steel fluctuates slightly after argon blowing, and there is no big turning phenomenon. After the refining is completed, Ti is added at 0.020% of the weight of the molten steel; After feeding the line, 7.3 minutes of sof...

Embodiment 3

[0025] A steelmaking plant adopts 120t converter smelting → LF furnace refining → four-machine four-stream casting machine φ350mm section continuous casting to produce 30Mn round tube billet. At the end of converter blowing, the end point carbon is controlled at 0.05%, and the end point temperature is controlled at 1680°C; the small platform is fed with 2.0m / t steel into the aluminum wire for deoxidation; the outbound composition of the small platform is controlled as: [C]0.30%, [Si] 0.18%, [Mn] 1.30%, [P] 0.009%; after deoxidation and alloying, soft argon blowing and stirring were carried out, and the stirring time was 4.0min, and the molten steel did not appear exposed during stirring.

[0026] When the molten steel reaches the LF refining furnace, the molten steel fluctuates slightly after argon blowing, and there is no big turning phenomenon. After refining, Ti is added at 0.035% of the weight of the molten steel; After feeding the line, soft blowing and stirring were perf...