JP2000126856A - Manufacture of slab free from surface defect caused by edging - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent any surface cracks generated in the edging by regulating the composition so as to contain Ti and Mg of specified quantity in a carbon steel having the composition consisting of C, Mn, Si, P, S, Al, N, O, Cu of respectively specified quantity, and the balance substantially Fe. SOLUTION: A molten steel whose composition is regulated to contain, by weight, 0.005-0.06% Ti and 0.0005-0.01% Mg in a carbon steel having the composition consisting of 0.001-0.5% C, 0.1-3% Mn, 0.005-2% Si, 0.001-0.1% P, 0.001-0.05% S, 0.001-0.1% Al, 0.0005-0.01% N, 0.0005-0.005% O, 0.05-2% Cu, and the balance substantially Fe, is continuously cast. This system is effective in a case where the carbon steel contains 0.05-2% one or more kinds of Nb, V, Cr, Mo, Ni, Zr, B and Ca. It is also effective in a case where the carbon steel contains <=0.1 % Sn.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a slab by reducing the width of a slab produced by a continuous casting method, and more particularly to a method for producing a slab having no surface defects.

[0002]

2. Description of the Related Art For mass production of steel, a process in which a continuous casting machine and a width reduction mill are combined is known. This process involves changing the width of the slab by changing the width of the slab by reducing the width of the slab in a continuous caster and then reducing the width in a subsequent rolling mill. It can be expected that productivity is improved due to the absence of the gap, and that the yield of the width changing portion is improved.

[0003] However, Cu or Cu-Sn
Alternatively, when Nb, V, N, or the like is contained, there is a problem that cracks occur at the time of width reduction, leading to surface defects.
The occurrence of these cracks is due to the embrittlement of steel, and Cu
For steel containing Cu and Cu-Sn, when scale is generated on the slab surface in a heating furnace, Cu or Cu that is hardly oxidized
It has been found that -Sn alloys gather at the interface between the slab and the scale, and that these are embrittlements caused by infiltration into the γ grain boundaries at temperatures near 800 to 1200 ° C. It has been known that embrittlement of a cast slab containing Nb-VN is caused by precipitation at austenite crystal grain boundaries at a temperature near 700 to 1000 ° C.

As means for preventing such embrittlement, it is desirable to reduce the amounts of Cu and Sn in the slab as much as possible.
In many cases, u and Sn are mixed from scrap, and there is a limit to the reduction. In addition, there is a steel type in which Cu is positively contained in the material, and a method that does not cause cracking when the width is reduced even in steel containing Cu or Cu—Sn is desired. In addition, for a slab containing Nb-N or Nb-V-N, it is effective to keep the slab temperature before applying deformation strain to the slab due to width reduction to a temperature higher than the embrittlement region near 700 to 1000 ° C. Is known. However, in the case of width reduction, there is a limitation on the amount of reduction per operation, and in order to obtain the required width reduction amount, multiple passes are reduced, so that the slab temperature does not enter the embrittlement zone during the multipass reduction. As described above, it is necessary to keep the slab temperature before the reduction very high, and it is difficult to achieve economically. Therefore, there has been a demand for a measure that does not have a restriction on the temperature history or a restriction on the content.

[0005]

SUMMARY OF THE INVENTION The present invention contains elements (Cu, Sn, Nb, V, N) which cause embrittlement by adding appropriate amounts of Ti and Mg in a molten steel stage before continuous casting. It is an object of the present invention to provide a manufacturing method capable of preventing surface cracks even when the steel to be rolled is reduced in width.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has the following configuration. Means 1 is as follows: C: 0.001 to 0.5% by weight, Mn: 0.1 to 3.0% by weight, Si: 0.005%
To 2.0% by weight, P: 0.001 to 0.1% by weight, S:
0.001-0.05% by weight, Al: 0.001-0.
1% by weight, N: 0.0005 to 0.01% by weight, containing 0.0005 to 0.005% by weight of oxygen and 0.05% of Cu
The composition is such that the content of Ti is 0.005 to 0.06% by weight and the content of Mg is 0.0005 to 0.01% by weight based on carbon steel containing iron and unavoidable impurities. This is a method of producing a steel slab in which surface defects do not occur by continuously casting molten steel that has been adjusted and reducing the width of the cast slab.

Means 2 comprises C: 0.001 to 0.5% by weight, Mn: 0.1 to 3.0% by weight, Si: 0.005 to 5% by weight.
2.0% by weight, P: 0.001 to 0.1% by weight, S:
0.001-0.05% by weight, Al: 0.001-0.
1% by weight, N: 0.0005 to 0.01% by weight, containing 0.0005 to 0.005% by weight of oxygen.
One or more of Nb, V, Cr, Mo, Ni, Zr, B, and Ca are contained in an amount of 0.1% by weight or less, and Cu is contained in an amount of 0.05% or less.
The composition is such that the content of Ti is 0.005 to 0.06% by weight and the content of Mg is 0.0005 to 0.01% by weight based on carbon steel containing iron and unavoidable impurities. This is a method for producing a steel slab in which the molten steel that has been adjusted is continuously cast, and the cast slab is subjected to a width reduction in which the surface defect does not occur due to the width reduction.

Means 3 comprises C: 0.001 to 0.5% by weight, Mn: 0.1 to 3.0% by weight, Si: 0.005 to 5% by weight.
2.0% by weight, P: 0.001 to 0.1% by weight, S:
0.001-0.05% by weight, Al: 0.001-0.
1% by weight, N: 0.0005 to 0.01% by weight, containing 0.0005 to 0.005% by weight of oxygen and 0.05% of Cu
To 2.0% by weight and a carbon steel containing 0.1% by weight or less of Sn and the balance of iron and unavoidable impurities,
0.005 to 0.06% by weight and Mg
A method of manufacturing a steel slab in which the molten steel whose composition is adjusted to 0.01% by weight is continuously cast, and the cast slab is reduced in width by a width reduction does not cause surface defects due to the width reduction.

Means 4 is as follows: C: 0.001 to 0.5% by weight, Mn: 0.1 to 3.0% by weight, Si: 0.005 to
2.0% by weight, P: 0.001 to 0.1% by weight, S:
0.001-0.05% by weight, Al: 0.001-0.
1% by weight, N: 0.0005 to 0.01% by weight, containing 0.0005 to 0.005% by weight of oxygen.
One or more of Nb, V, Cr, Mo, Ni, Zr, B, and Ca are contained in an amount of 0.1% by weight or less, and Cu is contained in an amount of 0.05% or less.
To 2.0% by weight and a carbon steel containing 0.1% by weight or less of Sn and the balance of iron and unavoidable impurities,
0.005 to 0.06% by weight and Mg
This is a method of manufacturing a steel slab in which molten steel whose composition is adjusted to be 0.01% by weight is continuously cast, and the cast slab is reduced in width by a width reduction without surface defects.

Means 5 are: C: 0.001 to 0.5% by weight, Mn: 0.1 to 3.0% by weight, Si: 0.005 to
2.0% by weight, P: 0.001 to 0.1% by weight, S:
0.001-0.05% by weight, Al: 0.001-0.
1-5% by weight, 0.0005-0.005% by weight of oxygen, and 0.005-0.06% by weight of Ti and 0. 0% by weight of Mg based on carbon steel consisting of iron and unavoidable impurities.
This is a method for producing a steel slab in which surface defects do not occur by continuously casting molten steel whose components are adjusted to be 0005 to 0.01% by weight and reducing the width of the cast slab.

Means 6 are: C: 0.001 to 0.5% by weight, Mn: 0.1 to 3.0% by weight, Si: 0.005 to 5% by weight.
2.0% by weight, P: 0.001 to 0.1% by weight, S:
0.001-0.05% by weight, Al: 0.001-0.
1% by weight, 0.0005 to 0.005% by weight of oxygen, 0.002 to 0.015% by weight of N, and the balance of carbon steel consisting of iron and unavoidable impurities,
0.005 to 0.06% by weight and Mg
This is a method for producing a steel slab in which surface defects do not occur by continuously casting molten steel whose composition is adjusted to be 0.01% by weight and reducing the width of the cast slab.

Means 7 are: C: 0.001 to 0.5% by weight, Mn: 0.1 to 3.0% by weight, Si: 0.005 to 5% by weight.
2.0% by weight, P: 0.001 to 0.1% by weight, S:
0.001-0.05% by weight, Al: 0.001-0.
1 wt%, 0.0005 to 0.005 wt% oxygen, 0.02 to 0.1 wt% Nb and 0.0
Ti in a carbon steel containing 0.002 to 0.015% by weight, the balance being iron and unavoidable impurities.
A method for producing a steel slab in which a molten steel having a composition adjusted to be 0.6% by weight and Mg in a range of 0.0005 to 0.01% by weight is continuously cast, and the cast slab is reduced in width by a width reduction to prevent surface defects. is there.

Means 8 are: C: 0.001 to 0.5% by weight, Mn: 0.1 to 3.0% by weight, Si: 0.005 to 5% by weight.
2.0% by weight, P: 0.001 to 0.1% by weight, S:
0.001-0.05% by weight, Al: 0.001-0.
1 wt%, oxygen 0.0005 to 0.005 wt%, Nb 0.02 to 0.1 wt% and V 0.0
1 to 0.1% by weight and 0.002 to 0.015% by weight of N, and 0.005 to 0.06% by weight of Ti and 0 to 0% by weight of the carbon steel consisting of iron and unavoidable impurities. This is a method for producing a steel slab in which surface defects do not occur by continuously casting molten steel whose composition is adjusted to be 0.0005 to 0.01% by weight and reducing the width of the cast slab.

Means 9 are as follows: C: 0.001 to 0.5% by weight, Mn: 0.1 to 3.0% by weight, Si: 0.005 to
2.0% by weight, P: 0.001 to 0.1% by weight, S:
0.001-0.05% by weight, Al: 0.001-0.
1 wt%, oxygen 0.0005 to 0.005 wt%, and others, such as Cr, Mo, Ni, B,
When rolling down a slab produced by continuous casting to carbon steel containing one or more of Zr and Ca in an amount of 0.1% by weight or less and the balance of iron and unavoidable impurities, , Continuous casting of molten steel in which the composition is adjusted so that Ti is 0.005 to 0.06% by weight and Mg is 0.0005 to 0.01% by weight, and the cast slab is reduced in width to reduce surface defects. This is a method for producing a billet in which no slag occurs.

Means 10 are: C: 0.001 to 0.5% by weight, Mn: 0.1 to 3.0% by weight, Si: 0.005 to
2.0% by weight, P: 0.001 to 0.1% by weight, S:
0.001-0.05% by weight, Al: 0.001-0.
1 wt%, oxygen 0.0005 to 0.005 wt%, and others, such as Cr, Mo, Ni, B,
A carbon steel containing one or more of Zr and Ca in an amount of 0.1% by weight or less and N in an amount of 0.002 to 0.015% by weight and a balance of iron and inevitable impurities is produced by continuous casting. When the resulting slab is reduced in the width direction, 0.005 to 0.06% by weight of Ti and 0.0005 to
This is a method for producing a steel slab in which surface defects do not occur by continuously casting molten steel whose composition is adjusted to 0.01% by weight and reducing the width of the cast slab.

Means 11 are: C: 0.001 to 0.5% by weight, Mn: 0.1 to 3.0% by weight, Si: 0.005 to 5% by weight.
2.0% by weight, P: 0.001 to 0.1% by weight, S:
0.001-0.05% by weight, Al: 0.001-0.
1 wt%, oxygen 0.0005 to 0.005 wt%, and others, such as Cr, Mo, Ni, B,
0.1% by weight or less of one or more of Zr and Ca, 0.02 to 0.1% by weight of Nb and 0.0% by weight of N
Ti in a carbon steel containing 0.002 to 0.015% by weight, the balance being iron and unavoidable impurities.
A method for producing a steel slab in which surface defects do not occur by continuously casting molten steel having a composition adjusted to be 0.6% by weight and Mg being 0.0005% to 0.01% by weight, and reducing the width of the cast slab. It is.

Means 12 are as follows: C: 0.001 to 0.5% by weight, Mn: 0.1 to 3.0% by weight, Si: 0.005 to 5% by weight.
2.0% by weight, P: 0.001 to 0.1% by weight, S:
0.001-0.05% by weight, Al: 0.001-0.
1 wt%, oxygen 0.0005 to 0.005 wt%, and others, such as Cr, Mo, Ni, B,
One or more of Zr and Ca are contained in an amount of 0.1% by weight or less, Nb is contained in an amount of 0.02 to 0.1% by weight, and V is contained in an amount of 0.1 to 0.1% by weight.
01 to 0.1% by weight, and N is 0.002 to 0.015
0.005 to 0.06% by weight of Ti and M with respect to carbon steel containing iron and inevitable impurities.
This is a method for producing a steel slab in which surface defects do not occur by continuously casting molten steel whose components are adjusted so that the g becomes 0.0005 to 0.01% by weight, and reducing the width of the cast slab.

The present inventors first set Cu or Cu in a slab.
Embrittlement when containing Sn or Nb, V, N, etc.,
Focusing on the embrittlement of austenite grain boundaries in all cases, as a means of preventing these embrittlements, the crystal grain size is reduced from the casting stage, and C
Means for reducing the crystal grain size in order to prevent embrittlement even if the liquid phase of u or Cu-Sn alloy enters or precipitates such as Nb, V, and N precipitate. As a result, the idea of utilizing fine inclusions in steel has been conceived.

The details of the present invention are described below. The present inventors firstly, as means for preventing embrittlement during width reduction, by reducing the crystal grain size from the casting stage, the liquid phase of Cu or Cu-Sn alloy enters the crystal grain boundary. Also Nb
It has been conceived to prevent embrittlement from occurring even when precipitates such as V, N and the like precipitate. If the crystal grain size is made smaller, the area of the crystal grain boundary becomes larger, but C or Cu-Sn
If the amount of the alloy liquid phase is constant, on the contrary, the penetration depth per grain boundary becomes shallower, and in the case of Nb, V, N, etc., on the contrary, the number of precipitates per unit area becomes smaller. It is considered that embrittlement can be suppressed even if the amount of the substance does not change.

As a means for achieving this, the inventors of the present invention will be able to reduce the solidification structure from which the crystal grains are formed and to suppress the growth of the crystal grains by using inclusions in the steel. Thought. There are many oxide-based inclusions originally formed during deoxidation in steel. Such an oxide is relatively large in size, so that the effect of suppressing the growth of crystal grains by pinning cannot be expected. However, if the oxide can be made finer, the growth of crystal grains can be suppressed. I thought.

[0021] First, a method of refining the solidification structure when the steel solidifies was studied. As a method of refining the solidification structure, it was considered to add Mg to molten steel.
Next, a deoxidation method for forming a fine oxide was examined. Various methods have been known for making oxides in steel finer, and one of them is disclosed in JP-A-5-4397.
No. 7 shows that an appropriate amount of Mg should be added after deoxidation of Ti. What is mentioned in this is the effect that the toughness after welding is improved, but the present inventors have found that this method is not only effective for suppressing the grain growth of the slab but also for the slab. I expected there was. Based on this expectation, the present inventors have concluded that it would be possible to apply Ti-Mg deoxidation to the prevention of embrittlement of a slab at the time of width reduction.

[0022]

[Table 1]

[0023]

[Table 2]

First, Ti-Mg deoxidation is performed to obtain Ti oxide.
A laboratory experiment was conducted to determine whether embrittlement can be prevented by generating fine particles or Mg oxide to refine the structure. Tensile test pieces were cut out of steel having the components shown in Tables 1 and 2, and an experiment was performed using a heat cycle tester capable of pulling. An experiment was performed in which the temperature at which the tension was applied was changed, and the cross-sectional shrinkage during the tension was examined. In addition, the fracture surface of the sample piece was examined with a scanning electron microscope and a transmission electron microscope. FIG. 1 shows the state of infiltration into crystal grains and the boundaries of Cu and Cu-Sn alloy into crystal grains. FIG. 2 shows precipitates such as Nb (CN) and V (CN) in crystal grains and in crystal grain boundaries. The distribution situation was investigated.

FIG. 1 shows the results of investigations on steels mainly containing Cu and Sn (corresponding to claims 1 to 4, the same applies hereinafter), and shows the effects of Ti concentration and Mg concentration on the embrittlement behavior. Here, white circles and white triangles indicate cases where embrittlement did not occur, and black circles and black triangles indicate cases where embrittlement occurred. It was determined that the steel produced by changing the concentrations of Ti and Mg by a grease-type tensile tester was brittle when the drawing value of the fractured surface when pulled at a predetermined temperature was less than 60%. The test was performed in air to generate scale on the sample surface.

In FIG. 1, the most severe condition was selected as the test condition. That is, the temperature was set to 900 ° C., which is the most brittle. From FIG. 1, white circles or white triangles are obtained by adding 0.005% by weight or more of Ti and 0.0005% by weight or more of Mg. That is, it can be understood that embrittlement has been eliminated because the aperture value of the fractured surface exceeds 60%.
However, when Ti is added in an amount of more than 0.06% by weight or Mg is added in an amount of more than 0.01% by weight, conversely, embrittlement occurs.

FIG. 2 is a survey of steels mainly containing Nb, V, and N (corresponding to claims 5 to 12, the same applies hereinafter), and shows the effects of Ti concentration and Mg concentration on the embrittlement behavior. . Here, open circles, open squares, and open triangles indicate cases where embrittlement did not occur, and open circles, open squares, and open triangles indicate cases where embrittlement occurred. It was determined that the steel produced by changing the concentrations of Ti and Mg with a grease-type tensile tester was brittle when the drawing value of the fractured surface was less than 60% when the steel was pulled at a predetermined temperature.

In FIG. 2, the severest conditions were selected as the test conditions. That is, the temperature was set to 800 ° C., which is the most brittle. As shown in FIG. 2, by adding 0.005% by weight or more of Ti and 0.0005% by weight or more of Mg, the aperture value of the fractured surface exceeds 60% and becomes a white circle, white square or white triangle. That is, it is understood that embrittlement has been eliminated. However, when more than 0.06% by weight of Ti or more than 0.01% by weight of Mg is added, embrittlement occurs on the contrary.

Next, in order to confirm that such an effect is due to the reduction in the crystal grain size, the crystal structure near the fractured surface was examined. In each case, it was confirmed that the crystal grains were fine. That is, as expected, even if the liquid phase of Cu or Cu—Sn alloy penetrates into the crystal grain boundaries due to the fine crystal grain size, Nb (CN) or V
Embrittlement could be prevented even when precipitates such as (CN) were present.

The reason for defining the conditions of the present invention will be described below. The target steel types are carbon steel containing Cu, containing Cu and Sn, or containing N, containing Nb and N, and further containing Nb,
Any steel containing V and N may be used. However, considering the steel composition range of the steel material actually used, the following composition range is obtained.

Since C is an indispensable element for imparting the strength of steel, the lower limit is set to 0.001% by weight, and the upper limit is set to 0.5% by weight as the maximum amount of carbon used in the sheet material. Also, Mn is necessary for obtaining strength and the lower limit is set to 0.1% by weight in order to exert its effect, and the upper limit is set to the maximum value of 3.0% by weight when used for special applications. Although Si may be unnecessary depending on the use, it is unavoidably mixed, so the lower limit is 0.005% by weight, and the upper limit is 2.0% by weight used for special purposes.

Since P is an element harmful to steel, its upper limit is preferably set to 0.1% by weight and is as small as possible. However, since P is inevitably mixed, the lower limit of 0.001% by weight is practical. Similarly, S also often impairs the product characteristics, and is desirably as low as possible. However, since it is inevitably mixed, the lower limit of 0.001% by weight is practical. The upper limit is set to 0.05% by weight to prevent cracking during continuous casting.

Cu and Sn are target elements of the present invention, and Cu and Sn are mixed in from scrap, which is a raw material of steel. Cu is also used to increase the strength of the material. The lower limit of Cu is the lowest concentration that causes embrittlement,
It was 0.05% by weight. The upper limit of Cu was set to 2.0% by weight as a concentration that adversely affects the material. on the other hand,
The upper limit of Sn is 0.1 at which the effect of the present invention is stabilized.
% By weight.

Nb, V, and N are also elements related to the present invention, and are used to increase the strength and toughness of the material. However, the effects of steel mainly containing Nb, V, and N are not significant. To obtain it, the upper limits of Nb, V, and N are limited. Further, the lower limits of Nb, V, and N were defined as values at which embrittlement did not occur. From this viewpoint, Nb,
The range of V and N is Nb: 0.02 to 0.10% by weight, V:
0.01 to 0.10% by weight, N: 0.002 to 0.01
It was 5% by weight. Further, for steel mainly containing Cu and Sn, the N content was set to 0.0005 to 0.010% by weight.

Although Al is generally used as a deoxidizing element, the lower limit of Ti is set to 0.1% by weight because the effect of suppressing embrittlement does not appear in this experiment. The lower limit is 0.001 as a value that is inevitably mixed.
% By weight.

[0036] Ti and Mg are important elements of the present invention. The lower limit of Ti was set to 0.005% by weight at which the effect of suppressing embrittlement appeared in this experiment. The upper limit was defined as 0.06% by weight at which embrittlement appeared again. Similarly, for Mg, the lower limit is 0.0005% by weight, and the upper limit is 0.0% by weight.
1% by weight.

[0037] Oxygen is also an important element of the present invention.
Oxygen is required for Mg and Ti to become oxides, but if the oxygen concentration is less than 0.0005% by weight, the number of oxides becomes insufficient. Further, too much oxide adversely affects embrittlement, so the upper limit was made 0.0050% by weight.

In addition, mainly Cu, Sn
In the contained steel, Nb, V, Cr, Mo, Ni, Zr, B,
One or two or more kinds of Ca, mainly Nb, V, and N-containing steels, may contain one or more kinds of Cr, Mo, Cu, Ni, Zr, B, and Ca in an amount of 0.1% by weight or less. .
In the actual manufacturing process, the added element is 100
% Is not necessarily contained in the molten steel, so it is necessary to add extra in consideration of the yield. There is no particular limitation on the method of addition. Any method may be used as long as it can be contained in steel so as to satisfy the above conditions.

[0039]

EXAMPLES Carbon steels having the components shown in Tables 3 and 4 and 5 were subjected to continuous casting and width reduction under the production conditions shown in Tables 6 and 7, and cracks were adjusted with the obtained steel slabs. As a method for checking cracks, scarf cutting was performed on the upper and lower surfaces of the slab by 2 to 10 mm.
The surface was visually observed. Further, a sample was cut out from the steel slab and the state of cracks in the cross section was examined by color check. In this experiment, Ti and Mg were added in a vacuum secondary refining device (RH).

[0040]

[Table 3]

[0041]

[Table 4]

[0042]

[Table 5]

[0043]

[Table 6]

[0044]

[Table 7]

Table 8 shows the results of working the steel mainly containing Cu and Sn. From the table, when the conditions in the case of the present invention were satisfied, no cracks were detected by visual observation and color check. Examples of the present invention will be specifically described with reference to Tables 3 and 8. In the table, A2 and B2 are examples corresponding to claim 1, and G2 is an example corresponding to claim 2. H2 is an embodiment corresponding to claim 3,
C2, D2, E2, and F2 are embodiments corresponding to claim 4. In each case, the slab did not crack at the time of width reduction, and was good.

On the other hand, in Comparative Examples D1 and E1, cracks occurred because Mg was not added. Comparative Example A1 is T
Cracking occurred because neither i nor Mg was added. Comparative Example C1 is Ti, H1 is Mg, and G1 is T
Cracks occurred because i and Mg were too high from the range of the present invention. Comparative Examples B1 and F1 were Cu and Sn, respectively.
Was higher than the range of the present invention. G3 of the conventional example is an example in which the Cu concentration was out of the range of the present invention and was lower than the concentration at which cracking occurred, so that no cracking occurred.

[0047]

[Table 8]

Also, without containing Cu and Sn, mainly Nb, V,
Table 8 shows the execution results of the steel containing N. From the table, when the conditions in the case of the present invention were satisfied, no cracks were detected by visual observation and color check. Examples of the present invention will be specifically described with reference to Tables 4, 5 and 9 in the same manner as described above. In the table, O2 is an embodiment corresponding to claim 5, M2 is an embodiment corresponding to claim 6, and B2 and C2 are claims 7
A2 is an embodiment corresponding to claim 8. Further, L2 is an embodiment corresponding to claim 9, D2,
K2 is an embodiment corresponding to claim 10, J2 is an embodiment corresponding to claim 11, E2, F2, G2, H2, I
2 is an embodiment corresponding to claim 12. In each case, no cracks occurred in the slab at the time of width reduction, and good results were obtained.

On the other hand, in Comparative Examples A1, G1, and K1, cracks occurred because Ti and Mg were not added. In Comparative Examples B1, E1, F1, H1, J1, and L1, cracks occurred because Mg was not added. In Comparative Example O1, cracking occurred because Ti was not added.
In Comparative Examples D1 and I1, cracks occurred because Ti and Mg exceeded the upper limit of the range of the present invention, respectively. In Comparative Example C1, cracks occurred because Nb exceeded the appropriate range. V in Comparative Example P and N in Comparative Examples M1 and Q
, Respectively, were out of the proper range, and cracks occurred. In Comparative Example R, since Ti was less than the range of the present invention, cracks occurred. In the conventional examples S, T, and U, N
Since b, V, and N were out of the range of the present invention and were lower than the concentration at which cracking occurred, the example did not crack without using the present invention.

[0050]

[Table 9]

[0051]

As described above, according to the present invention, Cu or Cu
-Even in steel containing predetermined concentrations of Sn, Nb, V, and N, cracking during width reduction does not occur, and a good steel piece without surface flaws can be obtained. It is possible to achieve the effects such as the ability to go straight to and the improvement of the yield, and the effect in this field is great.

[Brief description of the drawings]

FIG. 1 is a graph showing the influence of the amounts of Ti and Mg added on the prevention of embrittlement in steel containing Cu and Sn.

FIG. 2 Ti for preventing embrittlement in steel containing Nb, V and N
FIG. 3 is a graph showing the influence of the amount of Mg and the amount of Mg added.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22C 38/16 C22C 38/16 38/58 38/58

Claims (12)

[Claims] 1. C: 0.001 to 0.5% by weight, Mn:
0.1 to 3.0% by weight, Si: 0.005 to 2.0% by weight, P: 0.001 to 0.1% by weight, S: 0.001 to
0.05% by weight, Al: 0.001 to 0.1% by weight,
N: 0.0005 to 0.01% by weight, oxygen is 0.000%
0.005-0.06% by weight of Ti and Mg based on carbon steel containing 5-0.005% by weight and 0.05-2.0% by weight of Cu, and the balance being iron and unavoidable impurities.
Is characterized by continuously casting molten steel whose composition is adjusted to 0.0005 to 0.01% by weight, and reducing the width of the cast slab to produce a steel slab free of surface defects due to width reduction. Method. 2. C: 0.001 to 0.5% by weight, Mn:
0.1 to 3.0% by weight, Si: 0.005 to 2.0% by weight, P: 0.001 to 0.1% by weight, S: 0.001 to
0.05% by weight, Al: 0.001 to 0.1% by weight,
N: 0.0005 to 0.01% by weight, oxygen is 0.000%
5 to 0.005% by weight, and Nb, V,
Carbon steel containing one or more of Cr, Mo, Ni, Zr, B, and Ca in an amount of 0.1% by weight or less and containing 0.05 to 2.0% by weight of Cu, the balance being iron and inevitable impurities. On the other hand, 0.005 to 0.06% by weight of Ti and Mg
Is characterized by continuously casting molten steel whose composition is adjusted to 0.0005 to 0.01% by weight, and reducing the width of the cast slab to produce a steel slab free of surface defects due to width reduction. Method. 3. C: 0.001 to 0.5% by weight, Mn:
0.1 to 3.0% by weight, Si: 0.005 to 2.0% by weight, P: 0.001 to 0.1% by weight, S: 0.001 to
0.05% by weight, Al: 0.001 to 0.1% by weight,
N: 0.0005 to 0.01% by weight, oxygen is 0.000%
5 to 0.005% by weight, 0.05 to 2.0% by weight of Cu and 0.1% by weight or less of Sn, and 0.00% of Ti with respect to carbon steel consisting of iron and unavoidable impurities.
5 to 0.06% by weight and 0.0005 to 0.01% Mg
Continuous casting of molten steel whose composition has been adjusted to be
A method for producing a steel slab which does not cause surface defects due to width reduction of the cast slab. 4. C: 0.001 to 0.5% by weight, Mn:
0.1 to 3.0% by weight, Si: 0.005 to 2.0% by weight, P: 0.001 to 0.1% by weight, S: 0.001 to
0.05% by weight, Al: 0.001 to 0.1% by weight,
N: 0.0005 to 0.01% by weight, oxygen is 0.000%
5 to 0.005% by weight, and Nb, V,
The balance iron containing one or more of Cr, Mo, Ni, Zr, B and Ca in an amount of 0.1% by weight or less, containing 0.05 to 2.0% by weight of Cu and 0.1% by weight or less of Sn. And carbon steel consisting of unavoidable impurities
5 to 0.06% by weight and 0.0005 to 0.01% Mg
Continuous casting of molten steel whose composition has been adjusted to be
A method for producing a steel slab which does not cause surface defects due to width reduction of the cast slab. 5. C: 0.001 to 0.5% by weight, Mn:
0.1 to 3.0% by weight, Si: 0.005 to 2.0% by weight, P: 0.001 to 0.1% by weight, S: 0.001 to
0.05% by weight, Al: 0.001 to 0.1% by weight, oxygen 0.0005 to 0.005% by weight. 005-0.06% by weight and 0.0005-Mg
A method for producing a steel slab free from surface defects due to width reduction, comprising continuously casting molten steel whose composition is adjusted to 0.01% by weight, and reducing the width of the cast slab. 6. C: 0.001 to 0.5% by weight, Mn:
0.1 to 3.0% by weight, Si: 0.005 to 2.0% by weight, P: 0.001 to 0.1% by weight, S: 0.001 to
0.05% by weight, Al: 0.001 to 0.1% by weight, 0.0005 to 0.005% by weight of oxygen, and 0.002 to 0.015% by weight of N, with the balance being iron and inevitable 0.005 Ti for carbon steel consisting of chemical impurities
A surface defect caused by width reduction, characterized by continuously casting molten steel in which the composition is adjusted to be 0.06% by weight and Mg being 0.0005% to 0.01% by weight, and reducing the width of the cast slab. Method for producing billets that does not cause cracks. 7. C: 0.001 to 0.5% by weight, Mn:
0.1 to 3.0% by weight, Si: 0.005 to 2.0% by weight, P: 0.001 to 0.1% by weight, S: 0.001 to
0.05% by weight, Al: 0.001 to 0.1% by weight, 0.0005 to 0.005% by weight of oxygen, and Nb
0.02 to 0.1% by weight and N
Molten steel containing 15% by weight and the composition adjusted to 0.005 to 0.06% by weight of Ti and 0.0005 to 0.01% by weight of Mg with respect to carbon steel consisting of iron and unavoidable impurities. And continuously reducing the width of the cast slab to produce a steel slab free of surface defects due to the width reduction. 8. C: 0.001 to 0.5% by weight, Mn:
0.1 to 3.0% by weight, Si: 0.005 to 2.0% by weight, P: 0.001 to 0.1% by weight, S: 0.001 to
0.05% by weight, Al: 0.001 to 0.1% by weight, 0.0005 to 0.005% by weight of oxygen, and Nb
0.02 to 0.1% by weight, 0.01 to 0.1% by weight of V and 0.002 to 0.015% by weight of N, and the balance of carbon steel comprising iron and unavoidable impurities, Ti
0.005 to 0.06% by weight and Mg
A method for producing a steel slab that does not cause surface defects due to width reduction, wherein a molten steel whose composition is adjusted to be 0.01% by weight is continuously cast, and the cast slab is reduced in width. 9. C: 0.001 to 0.5% by weight, Mn:
0.1 to 3.0% by weight, Si: 0.005 to 2.0% by weight, P: 0.001 to 0.1% by weight, S: 0.001 to
0.05% by weight, Al: 0.001 to 0.1% by weight, oxygen 0.0005 to 0.005% by weight, etc.
Manufactured by continuous casting for carbon steel containing 0.1% by weight or less of one or more of Cr, Mo, Ni, B, Zr, and Ca depending on the use of the steel and the balance being iron and unavoidable impurities When the slab is rolled down in the width direction, 0.005 to 0.06% by weight of Ti and 0.0005 to
A method for producing a steel slab free from surface defects due to width reduction, comprising continuously casting molten steel whose composition is adjusted to 0.01% by weight, and reducing the width of the cast slab. 10. C: 0.001 to 0.5% by weight, M
n: 0.1 to 3.0% by weight, Si: 0.005 to 2.0
% By weight, P: 0.001 to 0.1% by weight, S: 0.00
1-0.05% by weight, Al: 0.001-0.1% by weight, oxygen 0.0005-0.005% by weight, and others, Cr, Mo, Ni, B, Zr depending on the use of steel ,
It was produced by continuous casting of carbon steel containing 0.1% by weight or less of one or more kinds of Ca and 0.002 to 0.015% by weight of N, the balance being iron and unavoidable impurities. When rolling down the slab in the width direction, Ti
5 to 0.06% by weight and 0.0005 to 0.01% Mg
A method for producing a steel slab which does not cause surface defects due to width reduction, characterized by continuously casting molten steel whose composition is adjusted to be in the range of weight%, and reducing the width of the cast slab. 11. C: 0.001 to 0.5% by weight, M
n: 0.1 to 3.0% by weight, Si: 0.005 to 2.0
% By weight, P: 0.001 to 0.1% by weight, S: 0.00
1-0.05% by weight, Al: 0.001-0.1% by weight, oxygen 0.0005-0.005% by weight, and others, Cr, Mo, Ni, B, Zr depending on the use of steel ,
Containing 0.1% by weight or less of one or more kinds of Ca;
And 0.02 to 0.1% by weight of Nb and 0.002% of N.
To 0.015% by weight, and 0.005 to 0.06 of Ti with respect to carbon steel consisting of iron and unavoidable impurities.
A steel having no surface defects due to width reduction, characterized by continuously casting molten steel in which the composition is adjusted so that the content of Mg is 0.0005 to 0.01% by weight and the cast slab is reduced in width. How to make pieces. 12. C: 0.001 to 0.5% by weight, M
n: 0.1 to 3.0% by weight, Si: 0.005 to 2.0
% By weight, P: 0.001 to 0.1% by weight, S: 0.00
1-0.05% by weight, Al: 0.001-0.1% by weight, oxygen 0.0005-0.005% by weight, and others, Cr, Mo, Ni, B, Zr depending on the use of steel ,
Containing 0.1% by weight or less of one or more kinds of Ca;
And Nb is 0.02 to 0.1% by weight and V is 0.01 to
0.1% by weight and N is 0.002 to 0.015% by weight
Continuously cast molten steel containing Ti and 0.0005 to 0.01% by weight of Ti and 0.0005 to 0.01% by weight of carbon steel containing iron and unavoidable impurities. And a method for producing a steel slab in which surface defects do not occur due to the width reduction of the cast slab.