JPH11179489A - Production of steel wire rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To unnecessitate blooming, to surely prevent the bulging of a wire rod caused by hydrogen accumulated to porous cavity (pore part) developed in small cross sectional cast slab and to improve the quality by using molten steel having a specific composition, continuously casting it into the small cross sectional cast slab in the cross sectional area in the width direction of the cast slab, regulating the hydrogen concn. in the cast slab to a specific value or lower and successively, rolling in a hot rolling process. SOLUTION: The molten steel composed by wt.% of 0.01-0.35 C, 0.02-0.50 Si, 0.1-1.7 Mn and the balance Fe is used and continuously cast into the small cross sectional cast slab in the cross sectional area in the width direction of the cast slab and the hydrogen concn. in the cast slab is regulated to <=3.5 ppm and successively, this cast slab is rolled in the hot-rolling process. Successively, the hot-rolled steel can be shifted to wire rod rolling and the working efficiency is improved and the production cost can be reduced. Then, as the dimension, in which the cross sectional area in the width direction of the cast slab is set to the small cross sectional area, this is different from the kind of mill in the hot-rolling mill, the kind of steel, etc., but as the one example, the productivity of the hot-rolling into the wire rod can be improved by casting into the square of 0.006-0.027 m<2> .

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 steel wire.

[0002]

2. Description of the Related Art When cooling a wire rod by hot rolling, 550 to 550 are used.
Japanese Patent Application Laid-Open No. Sho 62-50414 discloses a method for producing a high-strength wire having excellent cold drawability in which the wire is dehydrogenated under the condition that the average cooling rate in a temperature range of 200 ° C. is 40 ° C./sec or less. ing. In addition, 50 to 50 for steel wire and steel wire
Japanese Patent Application Laid-Open No. 8-337844 discloses a method for producing a high-strength, high-toughness steel wire or steel wire by performing a predetermined heat treatment in a 0 ° C. region to remove hydrogen causing brittleness. . Furthermore, by maintaining a specific relationship between the molten steel temperature and the casting speed, the hydrogen content in the molten steel immediately before casting maintains a high-quality continuous steel strip with a flat surface and few defects such as pinholes. A casting method is disclosed in Japanese Patent No. 2543909.

[0003]

As described above, the hydrogen content in a steel wire or a steel wire is controlled by the cooling conditions after the heat treatment or the rolling of the steel wire to improve the drawability of the wire in the cold. In the method, it is necessary to prevent the wire swelling during hot rolling due to hydrogen accumulated in the zigzag (void) generated at the center of the slab, which is unique to the slab having a small cross-sectional area in the slab width direction. Extremely difficult. That is, the hydrogen content specified in the former is for the wire after hot rolling. In addition, in the latter, since it is not possible to consider the effects of segregation and diffusion when slab slabs are formed from molten steel, it is necessary to predict swelling at the wire rod stage during hot rolling of slabs and prevent this swelling. Was difficult. Therefore, cast a slab having a large cross-sectional area in the slab width direction as a slab that is unlikely to have a zuck at the center of the slab, and then rolled as a wire in the subsequent process of slab rolling and hot rolling. Therefore, there is a problem that it is not preferable in terms of a reduction in work efficiency and an increase in manufacturing cost associated with slab rolling. The method of the present invention has been made to advantageously solve such problems, and the cross-sectional area in the slab width direction is cast into a small-section slab (billet), and the subsequent step of slab rolling is omitted. It is another object of the present invention to provide a method of manufacturing a steel wire rod capable of reliably preventing swelling of a wire rod due to hydrogen accumulated on a zigzag generated in a small-section slab and improving quality.

[0004]

The method of the present invention is characterized in that, by weight%, C: 0.01 to 0.35%, S
i: 0.02 to 0.50%, Mn: 0.1 to 1.7%,
Using a molten steel comprising the remaining Fe and unavoidable impurities, the slab is continuously cast into a slab having a small cross-sectional area in the width direction of the slab to reduce the hydrogen concentration in the slab to 3.5 ppm or less. This is a method for producing a steel wire, characterized by rolling.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the steel component according to the method of the present invention is necessary for satisfying the function as a wire rod, and the reasons for the limitation will be described. C is a basic element that most stably improves the strength of steel, and it is necessary to contain 0.01% or more to ensure the strength. If it exceeds 0.35%, it is difficult to secure toughness, which is not preferable.

[0006] Si is an element for improving the strength.
The content should be not less than 02%, but the upper limit content should be 0.50% for ensuring toughness.

Mn is also an element necessary for securing the strength and should be contained in an amount of 0.10% or more, but the upper limit should be 1.7% for securing the weldability or the toughness. The adjustment of the molten steel component consisting of the remaining Fe and unavoidable impurities in such basic components can be performed, for example, by primary refining by oxygen blowing refining and vacuum degassing or simple ladle refining (generally CAS
This is performed by secondary refining according to the following. In such a simple ladle refining, it is preferable to remove moisture adhering to a processing material such as a heating material to suppress the introduction of hydrogen.

[0008] In the simple ladle refining, the lower part of the reaction vessel is immersed under the surface of the molten steel tapped into the ladle after the primary refining, and Ar gas is blown into the molten steel from the bottom of the ladle to remove the molten steel in the ladle. While stirring, this is one of the refining methods that adjusts the steel composition by blowing oxygen gas into the reaction vessel and introducing heat-generating material, and if necessary, by adding alloyed iron, and at the same time, adjusts the molten steel temperature to be suitable for continuous casting. is there.

After that, the model of the hot rolling mill in continuous casting,
Depending on the type of steel, etc., the cross section in the slab width direction where slab rolling can be omitted is continuously cast into a slab having a small cross-sectional area. By casting into a slab having a small cross-sectional area in this way, it is possible to omit slab rolling in the next step and to shift to wire rod rolling, thereby improving work efficiency and reducing manufacturing costs. Many effects can be obtained.

[0010] When cast into a slab having a small cross-sectional area that can be omitted in slab rolling, the final solidified portion at the center of the slab is located immediately below the surface of the molten steel meniscus in the mold, and the static pressure of molten steel is ensured. Is insufficient, and a zaku (void) is easily generated at the center of the slab. When a back gap (void) is generated at the center of the slab, hydrogen in the steel accumulates on the back, causing swelling of the wire during hot rolling and deteriorating the quality.

In the method of the present invention, as described above, the hydrogen concentration in the steel is reduced to reduce the partial pressure of hydrogen gas accumulated in the Zaku, thereby reliably preventing swelling of the wire during hot rolling. is there. That is, in the method of the present invention, by performing hot rolling on a slab having a small cross-sectional area, it is possible to omit slab rolling and shift to wire rod rolling, and to improve work efficiency and reduce production costs. In addition, swelling of the wire at the time of hot rolling by forming a slab having a small cross-sectional area is prevented by reducing hydrogen in the slab, and a steel wire is manufactured while maintaining high quality.

Next, the sectional area in the slab width direction is reduced to a small sectional area.
Dimensions vary depending on the type of hot rolling mill, steel type, etc.
However, one example is 0.006 to 0.027 m^TwoFour
Casting into a square shape increases the productivity of hot rolling of wire rods
Etc. can be improved. Therefore, the cross-sectional area is 0.0
27m^TwoWhen it becomes excessive, the final solidification part at the center of the slab during casting
Is located sufficiently below the surface of the molten steel meniscus in the mold.
The molten steel static pressure can be secured, and supply of molten steel to the final solidification
So there is almost no backlash in the center of the slab
However, slab rolling is required, which is not preferable. Then cross section
0.027m ^TwoBlob rolling by
Can be omitted. In addition, 0.006m^TwoLess than
Supply of molten steel from the tundish to the mold becomes unstable
This makes stable operation of continuous casting difficult, which is not preferable.
On the other hand, the cross-sectional area is 0.027 m^TwoLess than
Zack is likely to occur in the center of the slab and the hot pressure of the wire
It causes swelling when extended. Hot of such wire rod
In order to prevent swelling during rolling, the hydrogen concentration in
Reduce to less than 3.5 ppm and accumulate on Zaku
Hydrogen gas partial pressure to ensure the wire swells during hot rolling.
Indeed, it can be prevented. Such slab width direction cross section
As shown in FIG. 1, the product refers to the slab length direction of the slab 1 (casting direction).
Direction) in the width direction (perpendicular direction).

[0013]

Next, examples of the method of the present invention will be described together with comparative examples. In Comparative Examples 1 to 3, the amount of hydrogen in steel is outside the scope of the present invention, and in Comparative Example 4, the slab size is outside the scope of the present invention.

[0014]

[Table 1]

Note 1: The continuous casting machine is a curved casting machine. Note 2: The size of the slab size is the size of one side of the square in the cross section in the slab width direction. Note 3: For steel type A, C: 0.02%, Si: 0.02%,
Mn: 0.1%: Remaining Fe and inevitable impurities. B is
C: 0.20%, Si: 0.30%, Mn: 0.5%:
Remaining Fe and inevitable impurities. C is C: 0.35%,
Si: 0.50%, Mn: 1.7%: remaining Fe and inevitable impurities. Note 4: Refining of the above steel types is performed by vacuum degassing or simple ladle refining of molten steel after primary refining by oxygen top-blowing converter refining.
The following refining was performed. Note 5: In the analysis of hydrogen, a sample of 5 × 5 × 50 mm in size was collected from a １ ／ thick portion (half) in the longitudinal direction of the slab. In order to prevent the release of non-diffusible hydrogen in the slab, the sample was cut out and analyzed for the total of non-diffusible and diffusible hydrogen while cooling with dry ice. Note 6: For the occurrence of the sag, the center of the slab in the longitudinal direction was cut, and the cross section was visually observed. Note 7: The swelling of the wire was visually observed after hot rolling to a wire having a diameter of 5 mm. Note 8: The presence or absence of slab rolling was determined in Examples and Comparative Examples 1 to 3 in that the cross section in the slab width direction was a small slab, and the slab was directly rolled into a wire without slab rolling. Comparative Example 4
The slab had a large cross-sectional area, and was made into a small-section slab by slab rolling, and then rolled into a wire.

[0016]

According to the method of the present invention, it is possible to reliably prevent swelling occurring during hot rolling of a wire rod of a small cross-sectional area billet (slab) in the slab width direction, in which a zag is likely to occur at the center of the slab. Therefore, it is possible to improve work efficiency by omitting slab rolling and reduce manufacturing costs. Also,
An excellent effect is obtained such that the swelling of the wire can be prevented and the quality can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a cross-sectional area in a width direction of a slab.

Claims (2)

[Claims] (1) C: 0.01 to 0.35% by weight,
Si: 0.02 to 0.50%, Mn: 0.1 to 1.7
%, The remaining cross section in the width direction of the slab is continuously cast into a slab having a small cross-sectional area using molten steel comprising Fe and unavoidable impurities, the hydrogen concentration in the slab is reduced to 3.5 ppm or less, and then hot rolling is performed. A method for producing a steel wire, comprising rolling in a process. 2. A slab width direction sectional area of 0.006 to 0.0
^2. The method for producing a steel wire according to claim 1, wherein the steel is continuously cast into a square slab of 27 m < ² >.