Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/10—Supplying or treating molten metal

Definitions

• the present invention relates to a method for continuously manufacturing extremely low carbon aluminum-killed steel. Background technology
• FIG. 1 is a schematic view of the molten steel injection section at the upper part of the continuous cinnabar making machine, and an outline of the continuous sintering method will be described with reference to FIG.
• Ar gas is blown into immersion nozzle 1 from upper nozzle 2 or sliding nozzle 3 and blown.
• the gas bubbles of the Ar gas are trapped by the solidified Schul during the production, and during the annealing after rolling, the Ar gas expands due to the rise in temperature, causing the surface of the cold rolled sheet to bulge.
• Japanese Patent Application Laid-Open No. The method is to arrange a refractory circumference whose lower end is immersed in molten steel of the tundish at a distance within lm from the center position of the tundish nozzle, and place the tundish nozzle in the refractory cylinder. This is a method in which 5 to 20 ppm of Ca is added to the amount of molten steel passing through.
• the method described in Japanese Patent Application Laid-Open No. 7-1276756 discloses a method in which Ca or a Ca alloy is added to molten aluminum steel containing C ⁇ 0.015% by weight. bets to - a method of treating as good Ri C a O- ⁇ ⁇ ⁇ 2 ⁇ 3 based inclusions by residual metal C a of 2 to 4 0 ppm in the steel is produced. Also, the method described in JP-A No. 611-457 in 3 is an aluminum-killed steel or aluminum-silicon chilled steel containing at least 0.05 wt% of Ti and at least 0.0 lwt% of ⁇ . In continuous production of steel, this is a method of adjusting the composition so that the molten steel force in the tundish contains 0.001 to 0.005 wt% of Ca.
• any of the conventional methods (1), (2), and (3) can be used.
• the gas does not intervene between the inner side surface of the immersion nozzle 1 and the molten steel flow, and there is no heat insulation effect, so the molten steel solidifies on the inner wall of the nozzle on the mold surface. Although cohesive adhesion of alumina disappears, nozzle clogging due to solidified iron 6 may occur.
• the ultra-low carbon aluminum-killed steel described in the present invention is a steel type having a carbon concentration of 30 ppm or less at the molten steel stage, which is mainly deoxidized with aluminum and having an oxygen concentration of 4 Oppm or less. Disclosure of the invention
• the present invention solves the above-mentioned problems of the prior art, and eliminates the need for the above-mentioned Ar gas injection, and at the same time, provides a stable continuous low-carbon aluminum-killed steel capable of preventing the cold rolled plate from wiping and generating.
• the task is to provide a manufacturing method.
• the present invention relates to continuous production of extremely low carbon aluminum-killed steel.
• the Ca concentration in steel is 6 to 20 ppm, the S concentration is 0.01% by weight or less, and the oxygen concentration is 30 ppm or less.
• the superheat degree ⁇ T of molten steel in the tandishes 4 shall be 16 ° C or more.
• the average molten steel flow velocity V at the nozzle body 1a should be 1.2 msec or more.
• the present inventors have made it possible to lower the melting point of alumina inclusions by adding Ca to ultra-low carbon aluminum-killed steel, and to stabilize without injecting gas such as Ar gas into the immersion nozzle 1.
• the following three items were examined in order to develop a continually cycling method that could be made by cycling and that could prevent the occurrence of rubbing and ⁇ ⁇ with cold-rolled steel.
• the melting point of the alumina inclusions in the molten steel is reduced by Ca to reduce the melting point so that the inclusion nozzle does not block the immersion nozzle without injecting gas into the immersion nozzle.
• Table 1 shows the experimental conditions. With the Ca concentration in Table 1 varied from 0 to 20 ppm, the relationship between nozzle clogging and C-a concentration in steel was investigated with an actual machine without blowing gas into the immersion nozzle. . Table 1 Experimental conditions for immersion nozzle clogging prevention experiment
• Figure 2 shows the relationship between the amount of Ca in molten steel and the immersion nozzle clogging index when Ar gas is not injected.
• the immersion nozzle clogging index is an index of the degree of opening of the sliding nozzle (a gate for adjusting the amount of molten steel located above the immersion nozzle), which indicates the degree of clogging of the nozzle. The larger the value, the greater the clogging.
• the immersion nozzle clogging index shown in Fig. 2 refers to the index value of the average opening of the first and second sliding nozzles.
• the conventional nozzle It can be seen that a nozzle clogging prevention effect equal to or higher than that of the Ar gas blowing method can be obtained.
• Ca ⁇ 6 ppm clogging of the immersion nozzle was remarkable, and the production was sometimes interrupted.
• the Ca in Table 1 was set to 6 to 20 ppm, and a more detailed study was conducted on clogging of the immersion nozzle under the condition that the Ar gas was not blown into the immersion nozzle.
• the T'0 concentration in the steel in Table 1 was varied from 10 to 40 ppm, and the relationship between the immersion nozzle clogging index and the TO concentration was investigated.
• Figure 3 shows the results.
• Other experimental conditions except for the Ca concentration and the T ⁇ 0 concentration in the steel are the same as in Table 1.
• the flow rate of molten steel in the body of the immersion nozzle straight v Investigated the relationship with
• the rate of surface defect occurrence due to mold powder is lower than that of cold-rolled steel sheets manufactured under mirroring conditions with ⁇ T force s' of less than 16 ° C. 1 Z3 or less.
• the present inventors can add Ca to ultra-low carbon aluminum-killed steel, prevent gas from being blown into the immersion nozzle, prevent clogging of the immersion nozzle, and prevent the occurrence of breakage. It was clarified that the conditions for maintaining the rate of surface defects caused by mold powder at a low rate are as shown in equation (2).
• a mackerel test of an ultra-low carbon cold-rolled steel sheet to which Ca was added was performed on a cold-rolled steel sheet obtained by the following two methods.
• Table 2 shows the compositions of the steels used in the experiments of b) and b).
• Table 2 Composition of steel subjected to power generation test
• a £ 2 03 is While generating a low by Ri A 2 0 a by Ri melting point C a C a O- A ⁇ 2 0 3 based mixed engagement compounds, C a S is precipitated around the compound, the C a S is Since it is hydrolyzable, it dissolves in water, and water accumulates in that part to form a local battery and generate heat.
• the S content in steel is closely related to the generation of ⁇ after cold rolling, and in the case of cold rolled sheets with a Ca content of 6 ppm or more and 15 ppm or less, As shown in Fig. 6, the S content in steel must be less than 0.01% by weight.
• Fig. 7 shows the relationship between the ⁇ occurrence index and the Ca concentration in steel in the range of 0.055 to 0.009% by weight of S in the water-water spray test.
• the amount of Ca increases, the generation of cold rolled sheets increases. ⁇ ⁇ In order to keep the generation below the allowable level, it is desirable that the amount of Ca be 20 ppm or less, more preferably 15 ppm or less.
• the ⁇ generation allowable level region is 6 ppm ⁇ Ca ⁇ 20 ppm, S ⁇ 0.01 wt%.
• the addition of Ca to the molten steel can be performed using a suitable material such as a Ca metal, a Ca—Si alloy, or the like using a ladle or a tundish.
• Fig. 1 is a schematic diagram of the continuous cinnabar making method and a schematic diagram of the adhesion of solidified iron to the inner surface of the immersion nozzle when gas injection into the immersion nozzle is stopped.
• Figure 2 is a graph showing the relationship between the immersion nozzle clogging index and the amount of Ca in molten steel.
• Fig. 3 is a graph showing the relationship between the immersion nozzle clogging index and the T0 concentration in molten steel.
• Fig. 4 shows the relationship between successive nozzles and ⁇ and ⁇ .
• Fig. 5 shows the relationship between the breakfart generation index and ⁇ .
• Fig. 6 is a graph showing the relationship between the ⁇ generation index and the S concentration in steel by the steam spray test.
• Fig. 7 is a graph showing the relationship between the ⁇ generation index and the Ca concentration in steel by the water spray test
• Fig. 8 is a diagram showing the C a-S region of the allowable generation level.
• Table 5 shows the area ratio of the nozzle opening, the rate of occurrence of defects in cold rolling, and the area ratio of hot water spray test after the cycling. Where the nozzle outlet area after fabrication
• Nozzle opening area ratio XI 00 (%) This is the nozzle outlet area before fabrication.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Continuous Casting (AREA)
• Treatment Of Steel In Its Molten State (AREA)

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• 1991
  • 1991-11-27 CA CA002074371A patent/CA2074371C/en not_active Expired - Fee Related
  • 1991-11-27 DE DE69125823T patent/DE69125823T2/de not_active Revoked
  • 1991-11-27 WO PCT/JP1991/001625 patent/WO1992009387A1/ja not_active Ceased
  • 1991-11-27 JP JP4500067A patent/JP2928382B2/ja not_active Expired - Fee Related
  • 1991-11-27 US US07/915,708 patent/US5297614A/en not_active Expired - Fee Related
  • 1991-11-27 EP EP91920806A patent/EP0512118B1/en not_active Revoked
• 1992
  • 1992-07-28 KR KR1019920701789A patent/KR100189259B1/ko not_active Expired - Fee Related

Patent Citations (3)

Non-Patent Citations (1)

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