JPS62196331A - Slab for round bar steel - Google Patents

Abstract

PURPOSE:To obtain the titled slab from which large diameter round bar steel having stable quality is obtd. without using continuously cast bloom of large section, by respectively specifying ratio of diameter of round bar steel to slab thickness and ratio of width to thickness in slab. CONSTITUTION:In the invention, a ratio (D/t) of a diameter D of round bar steel manufactured from slab to a thickness (t) of slab is prescribed to <=0.9. In this way, draft in slab thickness direction can be approached to that in slab width direction. As the result, occurrence of wrinkles flaw on round bar steel surface due to smaller draft in slab thickness direction compared with that in slab width direction can be prevented. By ensuring percentage of reduction in area (r) to <=3.5 at rolling to round bar steel from slab while prescribing a ratio (B/t) of a width B of slab to the thickness (t) to >=2.2, deterioration of inner part quality of round bar product can be prevented. Further, by prescribing the ratio (B/t) to 3.0, deformation, etc., due to buckling of round bar can be prevented.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to round bar consumption slabs, and in particular to improvement of round bar slabs for manufacturing round steel bars using slab materials.

[Conventional technology]

Conventionally, when manufacturing large-diameter round steel bars, it is necessary to supply a continuous bloom with a large cross section, and a continuous bloom casting machine is required. In addition, when large cross-section continuously cast blooms cannot be supplied, large diameter round steel bars are manufactured using ingot material.

[Problems to be solved by the invention]

However, when producing a large-diameter round steel bar from the large-section MI Fr bloom, a continuous bloom caster is required, which poses a problem in that it leads to an increase in equipment costs. In addition, when large cross-section continuously cast blooms cannot be supplied, ingot material is used, which poses a problem in that the manufacturing cost of large-diameter nine-piece molds increases. In addition, the continuously cast bloom material supplied from the bloom continuous caster has a ratio CB/of the bloom width B to the bloom thickness t.
t) is 1.0 to 1. /I becomes I12, that is,
Since the cross-sectional shape of the material is a square or a rectangle approximating a square, there is a problem in that internal defects such as center 1q analysis and center porosity are likely to occur at the center of the material.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned conventional problems, and it is possible to manufacture a large I1 round steel bar without using a continuous casting bloom with a large cross section. The purpose of the present invention is to provide a slab for a round bar 1 that can obtain stable quality. (Means for Solving the Problems) The present invention establishes the relationship between the dimensions of a slab and a round steel bar manufactured by this slab, such that the ratio of the diameter of the round steel bar to the thickness t of the slab (D/t) is 0.90 or less, and the ratio of slab width B to slab thickness [<
The above object is achieved by setting B/t) to be 2.2 or more and n times 3.0 or less.

[Effect]

In the present invention, the relationship between the slab and the round steel bar produced by this slab is such that the ratio of the diameter of the round steel bar to the thickness t of the slab (D/t) is 0°90 or less. This makes it possible to bring the rolling reduction rate in the slab thickness direction closer to the rolling reduction rate in the slab width direction.This reduces the roundness that occurs due to the rolling reduction rate in the slab thickness direction being smaller than the rolling reduction rate in the slab width direction. It is possible to prevent the occurrence of wrinkles on the surface of the steel bar.Also, by setting the relationship between the slab dimensions such that the ratio of the slab width B to the slab thickness (Pt/t) is 2.2 or more. When rolling from a slab to a round bar, the reduction ratio of the cross-sectional area can be maintained at 3.5 or more.This prevents deterioration of the internal quality of the round bar product.
can do. In addition, by setting the relationship between the slab dimensions such that the ratio of the slab width 8 to the slab ν mm t (<B/t) is 3.0 or less, when rolling from a slab to a round bar, it is possible to In addition, it is possible to prevent deformation due to buckling and a defective cross-sectional shape caused by a depression in the center caused by widening only at both ends in the width direction of the slab. Example 1 An example of the present invention will be described below with reference to the drawings. In this embodiment, as shown in FIGS. 1 and 2, a slab 10 and a round steel bar 12 made from the slab 10
The relationship between the dimensions of the slab 10 is such that the ratio (D/t) of the diameter of the round steel bar 12 to the diameter of the slab 10 is 0.90 or less, and the width of the slab 10 is set to the thickness of the slab 10. B ratio (B/t) is 2.2 or more and D3.
The slab 10 is formed in such a manner that the number of particles is 0 or less. The width B of the slab 10 and the thickness of the slab 10 (
The appropriate range of the relationship between the diameter of the round steel bar 12 and the diameter of the round steel bar 12 that becomes the product is set based on the following conditions. First, in order to prevent wrinkles 16 from occurring on the surface of the conventional round bar fM14 as shown in FIG. 5, the thickness t of the slab 10 is limited as shown in the following equation. D≦0.90t (1) Thereby, the rolling reduction ratio in the thickness direction of the slab 10 can be increased compared to the conventional one. Therefore, compared to the conventional method, the rolling reduction ratio in the thickness direction of the slab 10 can be made closer to the rolling reduction ratio in the width direction of the slab 10. This makes it possible to prevent the wrinkle flaws 14 from occurring due to the reduction ratio in the thickness direction of the slab 10 being smaller than the reduction ratio in the width direction of the slab 10. In addition, in order to prevent deterioration of the internal quantity '11 of the round steel bar 12 as a product, the cross-sectional area reduction ratio from the slab 10 ((17i then faB-t) to the round steel bar 12 cross-sectional area πD'/4), In other words, the reduction ratio is limited to 3.5 or more.
The restriction is based on the relationship between the reduction ratio r and the pass rate based on defective products by ultrasonic flaw detection. That is, this is based on the fact that, as shown in FIG. 3, when the rolling reduction ratio r is 3.5 or less, the pass rate is significantly reduced. Therefore, if the relationship in which the rolling ratio r is 3.5 or more is replaced with the relationship between the width B and thickness t of the slab 10 and the diameter of the round bar to be the product, the following equation is obtained. B[/(πD 2/4)≧3,5...(2>
If we rearrange the above equation 2), we get the following equation. Bt≧0.87πD2...(3) Next,
Based on equation (1) above, the maximum permissible diameter [ Find the formula: Bt≧0.87Xπ×DIIl
a×2 Bt≧0.87πx (0,90t)'B≧2.2, that is, B/t≧2.2 (4) Set the slab dimension to satisfy the condition of this equation (4). This makes it possible to prevent deterioration of the internal quality of the round steel bar 12 as a product. Also, during rolling of the slab 10 in the width direction, deformation due to buckling,
In addition, as shown in FIG. 6, in order to prevent defects in the cross-sectional shape due to the concave portion 18B in the center caused by the widening of only the widthwise ends 18A of the conventional slab 18, the width B of the slab 10 is increased. The thickness is limited to 3.0 times or less the thickness t of the slab 10. That is, B≦3. Ot Modifying the above equation, 3.0≧B/t (5) Note that the buckling deformation and defective cross-sectional shape during rolling occur due to inappropriate slab dimensions. Next, the above equations (4) and (5) are combined to form the following equation. 2.2≦B/t≦3.0 (6) By forming the slab 10 with dimensions that satisfy the condition (6) above, deterioration of internal quality and forming defects during rolling forming can be prevented. It can be prevented. In Figure 4, the horizontal axis is the slab thickness t, and the vertical axis is the slab width B. FIG. This appropriate area P is
Straight line Q (8-2, 2t) and straight line R (B-3, Ot
) is the area indicated by diagonal lines in the figure. According to this embodiment, the slab series Vi! Since it is possible to supply raw materials, there is no need to provide continuous bloom casting equipment, etc., and equipment costs can be reduced. In addition, it is possible to share the material with the plate material, and the material inventory can be reduced. In addition, since the raw material can be supplied by the plate slab continuous #R machine, it is possible to continuously cast round bars with large cross sections, which has been difficult in the past. In addition, the ratio of the slab width B to the slab thickness (B/1) is within the range of 2.2 to 3.0, and as the ratio becomes larger, it is advantageous for segregation and crimping of 17'. Become. Next, with reference to the table below, the actual IM results of this embodiment will be explained in comparison with the conventional one. First, in the first embodiment of the present invention, the dimensions of the slab 10 are such that the thickness t is 260πm1, the width B is 70On, and the diameter of the round bar W412 as a product is 210u. At this time, the ratio of the width B to the thickness t (B/t) is about 2.7, and the ratio of the diameter of the round steel bar 12 to the thickness t (D/t) is about 0.81. In this example, there was no deformation in the rolled shape during rolling, no wrinkle defects occurred, and the pass rate by ultrasonic flaw detection was 100%.
Met. Further, in the second embodiment of the present invention, the dimensions of the slab 10 are such that the thickness t is 310 mm, the width B is 930 um, and the diameter of the round steel bar 12 as a product is 27 On. In the JQ case of this second embodiment, the ratio (B/t) of the width B of the slab 10 to the thickness of the slab 10 is 3.
．． The ratio (D/t) of the diameter of the round steel bar 12 to the thickness t of the 01 slab 10 is approximately 0.87. In this second example, no deformation was observed in the rolled shape during rolling, no wrinkles occurred, and the pass rate by ultrasonic flaw detection was 100%. On the other hand, the dimensions of the slab 10 are 310 mm in thickness and 1000 mm in width B, and the diameter of the round steel bar as a product is 29 mm.
In the case of M;A of the first conventional example set to 0-, the ratio of the slab width B to the slab thickness t<B, /t) is approximately 3.2,
Round (steel) straightness (yi D) ratio (D/T) tit i9'70, 94% to slab thickness t
Ru. In the third case of this first conventional example, a defective product with a concave cross-sectional shape occurred during rolling, and wrinkles were observed on the surface of the round bar. Also, the passing rate by ultrasonic testing is 100.
%Met. Also, the slab dimensions and thickness t are 310x! ! , the width B is 600u, and the diameter of the round steel bar as a product is 280f.
In the case of the second conventional example where f1v is set, the ratio (B/t
) is approximately 1.9, the ratio (D/t) G, tF) is 0°9
It becomes 0. In the case of this second conventional example, although there was no deformation in the cross-sectional shape during rolling and no scratches occurred,
The pass rate for ultrasonic flaw detection has dropped to 50%. As is clear from the above results, according to the present invention, there is no deformation in the cross-sectional shape of the rolled material during rolling, no scratches occur, and the total one-person rate according to ultrasonic detection (b) is 100%. It can be seen that the !17 result was reduced by 1!1. [Effect of the invention] Since the present invention is configured as described above, it is possible to use a continuous cast slab for plates without using a continuous cast bloom with a large cross section. By manufacturing large diameter round bars, we can reduce equipment costs and manufacturing costs, and reduce material inventory by sharing plate steel materials and round bar cable materials. In addition, it has the advantage of being able to maintain stable quality.

[Brief explanation of drawings]

Fig. 1 is a front view showing one method of producing a round steel slab according to the present invention, Fig. 2 is a front view showing dimensions of a round steel bar manufactured according to the invention, and Fig. 3 is a reduction ratio of 43 according to the present invention. Fig. 4 is a diagram showing the relationship between the f'; FIG. 5 is a perspective view showing edge flaws that occur in a conventional round steel bar product, and FIG. 6 is a front view showing a product with a defective cross-sectional shape during rolling due to inappropriate slab dimensions in J5 in the conventional round bar manufacturing process. 10... Slab, 12... Round steel bar. Agent Kei Matsuyama Ya Yamataka Theory Figure 1 Figure 2

Claims (1)

[Claims] (1) The relationship between the dimensions of the slab and the round steel bar manufactured by this slab is expressed as the diameter D of the round steel bar relative to the thickness t of the slab.
(D/t) is 0.90 or less, and the ratio of the slab width B to the slab thickness t (B/t)
A slab for a round steel bar, characterized in that: is 2.2 or more and 3.0 or less.