JP3089381B2 - Continuous casting method of Ti-containing steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting method for stably producing a Ti-containing steel having a Ti concentration of 0.1 to 0.5% used for a solid wire for welding or the like.

[0002]

2. Description of the Related Art Conventionally, this steel type has been manufactured by an ingot-making method, but has been manufactured by continuous casting in order to improve productivity, yield, and save energy.

In continuous casting, mold powder (hereinafter, referred to as powder) is used to control heat removal lubrication in a mold.

[0004] For powders for Ti-containing steel, Ti
For molten steel whose concentration is less than 0.1 mass%, C / S
However, a powder having a composition of about 0.6 is used.

Further, a powder having a composition of C / S of about 0.2 made of Ti-containing stainless steel having a Ti concentration of about 0.5% is used (Steel Making Research No. 324, p. 10 (198)).
7)).

[0006]

When a powder having the above composition is used for molten steel having a Ti content of 0.1 to 0.5 mass%, the reaction represented by the formula (1) and the Ti suspended in the molten steel occur.
The powder composition during continuous casting changes significantly due to absorption of O ₂ -based inclusions into the powder and the like.

[0007]

[Ti] + (SiO ₂ ) = (TiO ₂ ) 10 [Si] (1)

Here, [Ti] and [Si] represent Ti and Si in molten steel, respectively, and are (SiO ₂ ), (TiO ₂ )
Represents SiO ₂ and TiO ₂ in the powder, respectively.

The present inventor has revealed from a detailed investigation that the composition change of the powder is mainly caused by the above reaction (1).

Further, depending on the composition of the powder, perovskite, which is a high melting point compound, is crystallized, so that the physical properties of the powder such as viscosity, melting temperature, heat removal characteristics and the like are remarkably changed, and stable casting such as occurrence of breakout is hindered. .

Therefore, in order to realize stable casting of the steel type, it is an object to suppress a change in powder composition during continuous casting and to prevent crystallization of a high melting point phase.

[0012]

SUMMARY OF THE INVENTION The present invention is to advantageously solve the above-mentioned problems, and its gist is to continuously cast molten steel containing 0.1 to 0.5 mass% of Ti. , Ca concentration, SiO ₂ concentration, F concentration,
Concentration of Na ₂ O, _{respectively% Ca,% SiO 2,%} F,% N
a ₂ O,

[0013]

C / S = 1.4 · (% Ca−0.53 ·% F)
/% SiO ₂

Then,

[0015]

## EQU5 ## 0.2 ≦ C / S ≦ 0.6

And

[0017]

[Formula 6] 10 mass% ≦% F +% Na ₂ O ≦ 30 mass%

A continuous casting method for Ti-containing steel, characterized by using a mold powder having a composition in the range of:

[0019]

Hereinafter, the present invention will be described in detail.

As described above, the change in the composition of the powder is caused by the reaction of the formula (1).

In order to prevent the reaction of the formula (1) from occurring, the activity a _TiO2 ^P of TiO _{2 in} the powder is increased,
It is important to reduce the activity a _SiO2 ^P of iO ₂ .

Therefore, the activities of TiO ₂ and SiO _{2 in} the powder were measured and are shown on the ternary phase diagram of CaO—SiO ₂ —TiO ₂ .

[0023] Figure 1 shows the equal a _TiO2 ^P curve CaO-SiO ₂ -TiO ₂ ternary phase diagram on.

In the region where C / S exceeds 0.6, a _TiO2 ^P sharply decreases as C / S increases. That is, the solubility of TiO _{2 in} the powder increases, and the composition change increases.

Therefore, the upper limit of C / S is set to 0.6 in order to suppress a change in the composition of the powder.

[0026] Figure 2 shows the equivalent a _SiO2 ^P curve on the CaO-SiO ₂ -TiO ₂ ternary phase diagram.

The value of a _SiO2 ^P increases with increasing SiO ₂ concentration, Therefore, it becomes easy to progress the reaction of (1). Further, when the SiO ₂ concentration increases, the viscosity of the powder increases, and the casting characteristics deteriorate. Therefore,
The lower limit of C / S is 0.2.

Next, the reasons for limiting the Na ₂ O concentration and the F concentration will be described. Usually, Na ₂ O and F are added to the powder in order to secure lubrication characteristics and heat removal characteristics.

In order to realize stable continuous casting, it is necessary that% Na ₂ O +% F is 10 mass% or more.

On the other hand, Na ₂ O, F are expensive, there is an upper limit to the content of these in terms of economic efficiency,% Na ₂ O +
The upper limit of% F is 30 mass%.

FIG. 3 shows a crystallized solid phase on a ternary phase diagram of CaO—SiO ₂ —TiO ₂ . At this time,% N
a ₂ O +% F is 10~30mass%.

In the range of C / S ≦ 0.6, solid phase crystallization does not occur even if the TiO ₂ concentration is increased up to 30 mass%.

[0033]

Example 1 The component is [C]; 0.01 to 0.1 mass
%, [Si]; 0.01 to 1.0 mass%, [M
n]; 1.0 to 2.5 mass%, [P]: 0.02 m
ass% or less, [S]; 0.02 mass% or less, [A
l]; 0.02 mass% or less, [Ti];
0.5 mass% and 300 tons weight of molten steel
Continuous casting was performed by a continuous casting facility having a mold having a cross section of 300 mm × 500 mm.

At this time, C / S = 0.5,% Na ₂ O = 1
A powder of 0 mass% and% F = 10 mass% was used.

In Comparative Example 1, the composition of the powder was C / S =
0.8,% Na ₂ O = 10 mass%,% F = 10 ma
This is the case where ss% powder is used.

FIG. 4 shows the locus of composition change for 40 minutes from the start of the casting of the method of the present invention and the powder of the comparative example.

In the case of the comparative example, the composition change of the powder was large, and a solid phase having a high melting point was crystallized with the increase of TiO ₂ .
While the heat removal characteristics deteriorated and breakout occurred 50 minutes after the start of casting, in the method of the present invention, the change in the powder composition was small, and the solid phase did not crystallize even when the TiO ₂ concentration increased, Stable casting was realized without breakout.

[0038]

Example 2 Component [C]: 0.01 to 0.1 mass
%, [Si]; 0.01 to 1.0 mass%, [M
n]; 1.0 to 2.5 mass%, [P]: 0.02 m
ass% or less, [S]; 0.02 mass% or less, [A
l]; 0.02 mass% or less, [Ti];
0.5 mass% and 300 tons weight of molten steel
Continuous casting was performed by a continuous casting facility having a mold having a cross section of 300 mm × 500 mm.

At this time, C / S = 0.2,% Na ₂ O = 1
A powder of 0 mass% and% F = 10 mass% was used.

In Comparative Example 2, the composition of the powder was C / S =
0.1,% Na ₂ O = 10 mass%,% F = 10 ma
This is the case where ss% powder is used.

In the case of the comparative example, the viscosity of the powder was high,
The flow of the molten powder was reduced, the heat removal became uneven, and the breakout occurred.On the other hand, in the method of the present invention, the change in the powder composition was small, and the high melting point solid phase was not crystallized. Out casting did not occur and stable casting was realized.

[0042]

Example 3 The component is [C]; 0.01 to 0.1 mass
%, [Si]; 0.01 to 1.0 mass%, [M
n]; 1.0 to 2.5 mass%, [P]: 0.02 m
ass% or less, [S]; 0.02 mass% or less, [A
l]; 0.02 mass% or less, [Ti];
0.5 mass% and 300 tons weight of molten steel
Continuous casting was performed by a continuous casting facility having a mold having a cross section of 300 mm × 500 mm.

At this time, C / S = 0.5,% Na ₂ O = 1
A powder of 0 mass% and% F = 10 mass% was used.

In Comparative Example 3, the composition of the powder was C / S =
0.5,% Na ₂ O = 4 mass%,% F = 4 mass
% Powder is used.

In the case of the comparative example, the viscosity of the powder was high,
The flow of the molten powder was reduced, the heat removal became uneven, and the breakout occurred.On the other hand, in the method of the present invention, the change in the powder composition was small, and the high melting point solid phase was not crystallized. Out casting did not occur and stable casting was realized.

[0046]

According to the method of the present invention, in continuous casting of Ti-containing steel, a change in powder composition is suppressed, and stable operation without breakout or the like can be performed. As a result, productivity, yield improvement and energy saving were realized.

[Brief description of the drawings]

FIG. 1 is a graph showing an isoactivity curve of TiO ₂ in powder.

FIG. 2 is a diagram showing an isoactivity curve of SiO ₂ in powder.

FIG. 3 is a view showing a crystallization region of a solid phase in a powder.

FIG. 4 is a diagram showing a locus of a change in powder composition.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kunihiko Watanabe 1 Kimitsu, Kimitsu-shi Nippon Steel Corporation Kimitsu Works (56) References JP-A-61-176451 (JP, A) JP-A-1- 306057 (JP, A) JP-A-2-220746 (JP, A) JP-A-4-100660 (JP, A) JP-A-62-166092 (JP, A) JP-A-5-185195 (JP, A) JP-A-57-142762 (JP, A) JP-A-64-8216 (JP, A) JP-A-3-226527 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 11/00 B22D 11/108

Claims (1)

(57) [Claims] 1. In continuously casting molten steel containing 0.1 to 0.5 mass% of Ti, the Ca concentration, SiO ₂ concentration, F concentration, and Na ₂ O concentration are set to% Ca and% Si, respectively.
C / S = 1.4 · (% Ca−0.53 ·% F), where O ₂ ,% F and% Na ₂ O are used.
/% SiO ₂ , a mold powder having a composition of 0.2 ≦ C / S ≦ 0.6 and 10 mass% ≦% F +% Na ₂ O ≦ 30 mass% is used. A continuous casting method for a Ti-containing steel, characterized in that: