JPS6130270A - Continuous casting method - Google Patents

Abstract

PURPOSE:To continue smooth continuous casting in continuous casting while powder is intervened between an oscillated casting mold and a molten metal by detecting the alumina value of the powder and changing the powder to low- alumina powder or decreasing the drawing speed of a billet when the detected value is above the limiting value. CONSTITUTION:The powder having an adequate viscosity value is intervened between the oscillated casting mold and the molten metal and the molten metal is cast continuously by moving smoothly the molten metal and solidified layer. The alumina value of the powder increases gradually to decrease the viscosity as a result of the alumina migration from the molten metal or slag. When the viscosity exceeds the limiting value, the powder is exchanged with the powder having the lower viscosity value or the low-viscosity powder is added thereto to maintain adequate viscosity value. The film bareakage is prevented and the continuous casting is made possible as well even if the drawing speed of th billet is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a continuous casting method for molten metal, and more particularly to a continuous casting method that is carried out by controlling the Al2O3 value of a powder molten layer in a mold.

(Prior Art) Generally, in continuous casting of molten metal, molten metal 13 is injected into a mold having a predetermined cross-sectional shape through a tongue tube 10 as shown in FIG.
It is drawn out continuously as 2. Slab 1 from mold 11
In the process of drawing out the mold 11, as shown in FIGS. 3 and 4, a separate vibration device is used to vibrate the mold 11 at a period suitable for the operating conditions. The powder 14 on the slab 12 in the mold 11 is melted by the heat of the molten metal in the tundish 10, forming a sintered layer 15 and a powder bath melt layer 16 in the mold 1, Fluorescent metal flows between the mold 11 and the slab 12 while controlling mold vibration (7) and plays the role of a lubricant.Depending on the lubrication state between the mold 11 and the slab 12, scratches and cracks may occur on the surface of the slab 12. breakout (hereinafter referred to as BO) 7 may occur.These causes are said to be due to the quality of the powder inflow condition.However, powder between the mold 11 and the slab 12 may The reality is that there is no effective means for measuring and evaluating the inflow state (measuring the lubrication state), for measuring information on the occurrence of surface scratches, and for preventing them.

In other words, the lubrication state between the mold 11 and the slab 12 was
As in '7-32866, the amount of strain in the mold on-nonlation mechanism is measured and detected by frictional force, or as in Japanese Patent Application Laid-Open No. 5'''i'-109554, changes in the current of the oscillation motor are detected. However, if such a change in force occurs, it is because sticking has already occurred, and it is already too late to predict breakout, and there is no practical way to prevent breakout. above is impossible.

(Problems to be Solved by the Invention) The present invention solves the problem of deterioration of the powder viscosity, which affects the lubrication state between the mold and the slab, in the molten powder long before the sticking that induces breakout occurs. Detect and predict the Al2O3 value, change the powder or reduce the slab drawing speed according to the change, etc.
By controlling the casting conditions, it prevents the deterioration of powder viscosity, thereby preventing breakage and quality defects caused by inclusions caused by deterioration of powder properties, and is also advantageous in determining the suitability of mold powder. This is what we are trying to achieve.

(Means for Solving the Problems) In order to achieve the above object, the present invention is constructed as follows.

In other words, a continuous casting method for molten fluorite in which powder is charged onto the free surface of molten metal in a mold, and the powder is melted by the heat of molten steel to serve as a lubricant between the casting pot metal and the inner wall surface of the mold. , the Al-203 value in the molten powder is detected and compared with a preset limit value, and if it is higher than the set value, change to low A7203 powder or reduce the slab drawing speed. The continuous casting method is characterized in that the continuous casting method is performed in a continuous casting manner, or in combination of either one or both.

The misfired i94 will be explained in more detail below.

The low AIAos powder in the present invention refers to one having a content AtzCh value of 2'y or less, for example. In addition, the reduction in the slab drawing speed is defined as 80% or less of the steady drawing speed, but it is 80% or less from increasing the mechanical strength by increasing the shell thickness.
The above areas may be considered as the scope of control.

In the present invention, the charge of low AL203 powder is added to the top layer of the already charged powder. Al2 is obsessed with hiding things.
The old powder whose O3 value has reached the specified limit value continues to flow down from between the mold and the slab and is consumed, so the amount of AIAO3 contained in the powder in the mold will not exceed that amount.

According to the findings of the present inventors, the initial viscosity of the powder once determined increases during use, which is determined by the increase in A and e'203 contained in the powder due to absorption and production from the molten copper and inflow from other sources. . Therefore, the initial AO203 for each powder
Even if there is a difference in the content, the present invention can be achieved by controlling the amount of increase in initial ALz 03 when a predetermined viscosity is satisfied at the beginning of use.

That is, the content of A t203 in the powder used in the present invention
The amount may be controlled by the A t203 value obtained when the viscosity obtained from the initial Al2O3 content of the powder reaches the control limit, and it corresponds to the increased viscosity during use when the viscosity reaches the control limit. The increase A4031 may be managed directly. The slab drawing speed is not particularly limited, as long as it is selected based on the slab cooling solidification ability to increase the mechanical strength of the shell to a level considered necessary.

(Function) The present invention described above is based on the following findings. That is, according to the experiments and studies conducted by the present inventors, there is a relationship between A403, viscosity, and restrictive breakout (hereinafter referred to as BO) as shown in FIG. In other words, in region a where the Al2O3 value in the molten powder increases and the viscosity is high, restrictive BO occurs, while A
2. , 03 and in the low viscosity range, it became clear that normal casting without BO generation could be performed. Furthermore, B.O.
As a result of examining various causes of occurrence of Al
As O3 becomes more concentrated, the viscosity increases as shown in Figure 6. As a result, oxidized inclusions or other At
When the ZOE source is absorbed into the molten powder, the viscosity increases and the powder lubrication between the mold and the slab becomes uneven, forming sticking, which eventually leads to BO.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 4, the powder 14 charged onto the molten phosphor 13 in the mold 11 is heated by the heat of the molten metal 13 in the mold 11 to form a sintered layer 5. FIG. 1 shows the operational flow of the present invention carried out under such conditions for forming each layer of the molten layer 16. 1, one piece of the molten powder in the mold 11 is periodically sampled, a component analysis 2 is performed, and the values are input into the computer 3. The value is quickly displayed simultaneously on the operator display panel 4 and the control room display panel 5.
, it is judged in step 7 whether or not it is in the restrictive breakout occurrence region a shown in FIG. Change to low Al2O3 powder and return to normal operation range of Al2
Breakout due to sticking is prevented in advance by changing one or both of the casting conditions 1, such as lowering the O3 value or lowering the casting speed to, for example, 8.]% or less to encourage shell formation.

Meanwhile, on the control room side, A 7203ill! If it is in the restrictive breakout danger region, monitor 9 is performed to see if the casting conditions are quickly changed to prevent restrictive breakout. These data p-1
d, Ko, O, '5 R Curved continuous slab caster with drawing speed 1.2 mfin X Cast slab size 280M+lm
This is data at X1800m.

The above embodiment is just an example, and when detecting A & 03 or viscosity in the molten powder that affects the lubrication of the mold instantly or continuously, the restrictive block/kout danger area a shown in Section 7. By changing the casting conditions in the same manner as in the embodiment using the ink with which the detected values are compared, the effect of preventing restraint breakout can be obtained.

(The effect of the invention is that when the present invention'tr% is applied, the frequency of occurrence of restrictive breakout, which used to be 2 to 3 cases per 1500 heats, has disappeared. Many benefits are brought about, such as the ability to determine the applicability of each powder by grasping the probability that the Al2O3 value falls within the aSiJt range shown in FIG.

[Brief explanation of the drawing]

Fig. 1 is a flow diagram showing an embodiment of the present invention, Fig. 2 is a sectional view showing an outline of continuous casting equipment, Fig. 3 is a schematic diagram of a mold vibration device, and Fig. 4 is a state of distribution of powder in the mold. 5 is a schematic diagram showing Al in the molten powder during casting.
Figure 6 shows the changes in the viscosity η when the Al2O3 value increases, and Figure 7 shows the changes in the 2O3 value.
A diagram showing the relationship between value, viscosity, and constraint breakout. ■... Melted powder collection work - 2 - Analysis 3... Total 'j4 - Iso 4... Display to operator Cδ position 5...
Display device to command room 6... Recording device 7... ・A Comparison with reference value of 403fI 8...
・・BO prevention measures 9・・Monitoring work 10・・Tundish work】 Powder 15... Powder sintered layer 16... Molten powder

Claims (1)

[Claims] In a continuous casting method for molten metal in which powder is charged onto the free surface of the molten metal in the mold and is melted by the heat of the molten metal to serve as a lubricant between the cast metal and the inner wall surface of the mold, Detect the Al_2O_3 value of the powder, compare it with a preset limit value, and if it is higher than the set value, change to a low Al_2O_3 powder or reduce the slab drawing speed, or both. A continuous casting method characterized by a combination of