JPH0663601A - Round steel sizing rolling method - Google Patents

Abstract

(57) [Abstract] [Purpose] In a method of sizing and rolling a round steel bar by a 4-roll rolling mill, the sizing possible range by the same roll is widened while maintaining the high dimensional accuracy that is characteristic of the 4-roll. [Structure] Of the two 4-roll rolling mills 1 and 2 arranged in series on a pass line P, each roll pair of the 4-roll rolling mill 1 on the upstream side is arranged as follows. I.e. roll 1
The distance L between the first reference line O ₁ based on the center line of A (1B) and the second reference line O ₂ based on the line connecting the centers of the rolls 1C (1D) is set to the upstream roll pair 1C, Hold at 5 times the projected contact length in 1D.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for sizing and rolling a rod or wire having a round cross section by a 4-roll rolling mill, and in particular, it maintains high dimensional accuracy, which is a feature of the 4-roll type. The present invention relates to a method capable of widening the sizable range.

[0002]

2. Description of the Related Art The conventional sizing rolling method for round bar steel is based on the number of roll pairs used in one stand.
There are two-roll method, three-roll method, and four-roll method. In each method, for example, as shown in FIGS.
3 is rolled in a plurality of passes while changing the rolling direction by a pair of rolls 12A to 14C having grooves 12a to 14c having a predetermined cross-sectional shape on the peripheral surface.

The same material 1 is produced by each method shown in FIGS.
Sizing rolling is applied to 3 and the performance of each method is compared.
The experiment was done. Here, the diameter r of the material 13 is 50 mm
And the grooves 14a, 14 of each roll used for the final pass
The shapes of b and 14c are as shown in FIGS.
And groove radius R₁= R₂= R₃= 25 mm, the center angle of the groove
θ ₁= 90 °, θ₂= 60 °, θ₃= 45 °.

The cross section of the obtained round bar steel is, as shown in FIG. 11, a circle that is slightly close to a quadrangle in the two-roll method, a circle that is slightly close to a hexagon in the three-roll method, and a slightly octagon in the four-roll method. Although the circles are close to each other, the relationship between the difference between the maximum diameter d ₁ and the minimum diameter d _{2 of} each cross section (diameter deviation) and the amount of reduction was examined. Further, when the amount of reduction becomes large and the material to be rolled sticks out from the roll gap, it becomes defective as a product, but the linear portions 14d and 14e of the grooves in the adjacent rolls (for example, 14D and 14E) as shown in FIG. The intersecting point t was set as a baring limit, that is, a rolling limit, and the amount of reduction until reaching the baring limit was also examined. These results are shown graphically in FIG. In FIG. 13, the limit of protrusion is indicated by ↓.

As can be seen from FIG. 13, the four-roll method can be sized with high dimensional accuracy with the same amount of reduction, but the amount of reduction to the limit of the protrusion is small (that is, the protrusion immediately occurs). The sizing range becomes narrow. On the contrary, in the two-roll method, the dimensional accuracy is poor, but since a considerable amount can be pressed down to the limit of the protrusion, the sizing range becomes the widest.

FIG. 14 shows the relationship between the width expansion ratio and the rolling reduction of the round steel bar obtained by each method. The width expansion ratio is represented by [(width of material after rolling−width of material before rolling) / width of material before rolling] × 100. As can be seen from the results of FIG. 14, the width expansion ratio at the same reduction ratio is highest in the two-roll method and decreases in the order of the three-roll method and the four-roll method.

If the width expansion due to the reduction is large,
Even if rolling is performed with the same reduction amount, variations in width change amount increase depending on rolling conditions such as steel type of the material to be rolled, temperature, speed, etc., so that dimensional accuracy of the product deteriorates. That is, also in this respect, the 4-roll method is advantageous in terms of dimensional accuracy.

[0008]

Considering the above results, in the conventional sizing rolling method for round bar steel, in the case of producing only those which are not required to have a high dimensional accuracy, it is necessary to
It is advantageous to adopt the roll method to obtain a large sizing range for the same roll, and the 4-roll method is adopted when manufacturing a product requiring high dimensional accuracy. However, in the 4-roll method, it is necessary to frequently change the rolls because the sizing range of the same roll is narrow. Since it is necessary to stop the rolling when exchanging the rolls, if the number of times of exchanging the rolls is large, the work efficiency is significantly reduced.

The present invention is intended to solve such a problem and provides a method capable of widening the sizing range by the same roll while maintaining the high dimensional accuracy which is a feature of the 4-roll method. The purpose is to do.

[0010]

In order to achieve the above object, the present invention provides two 4-roll rolling mills for rolling a material from two directions orthogonal to each other with two-to-four rolls between two rolling mills. In the method of sizing rolling round bar steel by a rolling mill train that is arranged in series with the rolling direction shifted by 45 °, a four-roll rolling mill of the first stand arranged upstream of the two rolling mills. , A first reference line obtained by projecting the center line of the axis of one pair of rolls onto a plane parallel to the end face of the other pair of rolls, and the center connecting the centers of the rolls of the other pair in the plane A method for sizing and rolling a round steel bar, characterized in that the distance from the two reference lines is larger than 0 and is maintained at 5 times or less of the projected contact length of the roll pair positioned on the upstream side of both roll pairs. .

The most preferable range of the distance is 30
mm to twice the projected contact length.

[0012]

When the above distance is L, if L = 0, it becomes the same as the conventional 4-roll method, but in the method of the present invention, L> 0.
By doing so, the position of the rolled material that is rolled down by two rolls forming a pair shifts between each pair. Therefore, by appropriately setting the value of L, both the conventional four-roll method and the two-roll method can be used. The combined action of the good points of. That is, due to the advantage of the two-roll method, the sizing possible range by the same roll is larger than that of the conventional four-roll method
Due to the advantage of the 4-roll method, the dimensional accuracy is higher than that of the conventional 2-roll method.

If the distance L is too large, the distance from the conventional 4-roll method becomes closer to that of the conventional 2-roll method. A large number of experiments in which L was changed by the method of the present invention were carried out, and the width expansion ratio of the obtained round bar steel was measured. Then, the relationship between the width expansion ratio and the ratio of L to the projected contact length l _d (L / l _d ) in the roll pair located on the upstream side was examined.
The results are shown graphically in FIG. As can be seen from this result, when L / l _d exceeds 5, the degree of deterioration of the width expansion ratio becomes severe. Therefore, it is necessary to keep the value of L greater than 0 and 5 times or less of the projected contact length l _d .

That is, in the graph of FIG. 4, in a region E ₁ of L / l _d ≦ 5 which is the range of the present invention, a pair of rolls on the upstream side for biting the material to be rolled first and a downstream for biting on the material to be rolled later. Since the material to be rolled is rolled down at a position relatively close to the pair of rolls on the side, the restraining force is large, and the feature of the conventional 4-roll method can be used to suppress the width expansion ratio to be small. In the region E ₂ of L / l _d > 5 which is outside the scope of the present invention,
The restraint force is reduced because the distance between the front and rear roll pairs is too large, and the width expansion ratio is increased due to the characteristics of the conventional two-roll method.

On the other hand, according to the method of the present invention, the amount of reduction that can be rolled (the amount of reduction until reaching the above-mentioned bite limit) and L
The result of examining the relationship with is shown in the graph of FIG. Solid line a ₁
Is the radius of curvature of the roll hole type [R ₃ in FIG. 10 (c)]
Is 25 mm and the broken line a ₂ shows the results when R ₃ is 15 mm. Straight b _1, b ₂ in FIG. 5 was found in the experiment conducted for comparison, a line indicating the rollable reduction amount by the conventional 3-roll method, each of the a _1, a ₂
Corresponds to the results when using a roll hole type with the same radius of curvature as. It can be seen from FIG. 5 that if L ≧ 30 mm, the method of the present invention can achieve a sizing range that is equal to or greater than that of the conventional three-roll method.

The distance L is determined to be an appropriate value within the above range in consideration of the required dimensional assurance level of the product and the target rolling efficiency. From the actual rolling result of No. 3, the most suitable range of the distance L is 3
It has been found to be between 0 mm and twice the projected contact length.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram for explaining the configuration of the present invention, FIG. 2 is an enlarged view showing a hole-shaped portion in the AA line cross section of FIG. 1, and FIG. 3 is a BB line cross section of FIG. It is an enlarged view which shows the hole type part in.

As shown in FIG. 1, two 4-roll rolling mills 1 and 2 are arranged in series in a pass line P. Of these, a 4-roll rolling mill 1 arranged on the upstream first stand P1
Is composed of two to four rolls 1A, 1B, 1C and 1D, and the material 3 to be rolled is formed by one pair of rolls 1C and 1D from the vertical direction in FIG. 1 to the other pair of rolls 1A and 1B. Thus, the pressure is reduced in the left-right direction in FIG.

Each roll pair has a roll 1A (1
The first reference line O _{1 obtained} by projecting the center line of B) onto a surface parallel to the end surface of the roll 1C (1D) (for example, on this paper surface) and the centers C ₁ and C _{2 of the} rolls 1C and 1D on the above surface. It is arranged with a distance L held between it and the connected second reference line O ₂ . Therefore, although this 4-roll rolling mill 1 is a 4-roll rolling mill, it has a two-roll rolling mill 21 including a pair of rolls 1C and 1D as shown in FIG.
It can be considered that a two-roll rolling mill 22 including a pair of rolls 1A and 1B as shown in (b) is arranged at a position displaced by L.

Then, in the first pass of FIG.
Second reference line O₂Pressed rolled in the rolling direction indicated by
In the second pass of FIG. 2B, the rolled material 3 is the line O₂
Line O orthogonal to₃(Ie θ₁= 90 °)
Second stand P2 on the downstream side after being rolled in the rolling direction
Head to. 4-roll rolling arranged on the second stand P2
Machine 2 consists of 2 to 4 rolls 2A, 2B, 2C and 2D.
And the rolling direction by one pair of rolls 2A and 2D
O _FourAnd the pressing direction O of the first stand P1₂Angle θ with
₂, And rolling by the other pair of rolls 1B and 1C
Direction O_FiveAnd the pressing direction O of the first stand P1₃Angle between
Degree θ₃Both are set to 45 °.

By means of the method of the present invention, various raw materials having a substantially circular cross section were sized and rolled under the following conditions by the rolling mill train thus constructed. Rolling conditions Steel type S45C Rolling temperature 850-900 ° C Material diameter (mm) 21, 33, 44, 55 Roll diameter 380mm Roll hole type (see Fig. 10 (c)) Center angle θ ₁₃ = 45 ° Curvature radius R ₃ (mm) 10.0, 16.0, 21.5, 2
Against 7.0 rolling reduction (mm) 1.0 to 5.0 the distance _{L 40~60mm (L / l d 1.5~4.4} ) of each diameter material was 1.0~5.0mm pressure As a result, as shown in Table 1, products having a wide range of diameters were obtained by the same roll hole type as compared with the conventional 4-roll method.

[0022]

[Table 1]

The eccentricity difference was measured for each of the obtained round bar steels, and the relationship between the eccentricity difference and the product diameter is shown in a graph in FIG. In FIG. 6, a broken line T indicates the tolerance defined in JIS. As can be seen from FIG. 6, according to the method of the present invention, J
It can be seen that sizing rolling can be performed with a dimensional accuracy higher than twice the tolerance defined by IS.

[0024]

As described above, according to the present invention, the distance L is maintained between the two pairs of rolls forming the 4-roll rolling mill, and the value of L is set to an appropriate range. As a result, the combined effects of the conventional two-roll method and four-roll method are exerted, and while maintaining high dimensional accuracy,
The sizing range of the same roll can be widened.

As a result, it is possible to roll a product with good dimensional accuracy without secondary processing such as drawing or peeling, to a wide size range, and to reduce the number of roll replacements, resulting in a significant rolling stop time. It also has the effect of shortening the work efficiency.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining a configuration of the present invention.

FIG. 2 is an enlarged view showing a hole-shaped portion in a cross section taken along the line AA of FIG.

3 is an enlarged view showing a hole-shaped portion in a cross section taken along the line BB of FIG.

FIG. 4 is a graph showing a relationship between a width expansion ratio and a ratio (L / l _d ) of L to a projected contact length l _d in a roll pair located on the upstream side.

FIG. 5 is a graph showing a relationship between a rollable reduction amount and L according to the method of the present invention.

FIG. 6 is a graph showing the relationship between the deviation in diameter and the product diameter of round steel bars obtained according to the examples of the present invention.

FIG. 7 is a schematic diagram showing an example of a conventional two-roll method.

FIG. 8 is a schematic diagram showing an example of a conventional three-roll method.

FIG. 9 is a schematic diagram showing an example of a conventional 4-roll method.

FIG. 10 is a schematic diagram showing a groove shape of a roll used in an experiment.

FIG. 11 is a schematic diagram for explaining a difference in diameter deviation.

FIG. 12 is a schematic diagram showing the limit of sticking out set in the experiment.

FIG. 13 is a graph showing the relationship between the diameter deviation and the amount of reduction in the conventional example.

FIG. 14 is a graph showing the relationship between the width expansion ratio and the rolling reduction in the conventional example.

[Explanation of symbols]

1 4-roll rolling mill 1A-1D roll 2 4-roll rolling mill 2A-2D roll O ₁ 1st reference line O ₂ 2nd reference line P1 1st stand

Claims (1)

[Claims] 1. A rolling mill comprising two four-roll rolling mills for rolling the material from two directions orthogonal to each other with two to four rolls, and the rolling directions of the rolling mills are shifted by 45 ° and arranged in series. In the method for sizing rolling round steel bars by rows, in the four-roll rolling machine of the first stand arranged on the upstream side of the two rolling mills, the center line of the axis of one pair of rolls is set to the other pair. The distance between the first reference line projected on a plane parallel to the end face of the roll and the second reference line connecting the centers of the other pair of rolls on the surface is greater than 0, and the two roll pairs are A method for sizing and rolling a round steel bar, characterized in that the rolling contact length is kept at 5 times or less of the projected contact length of the roll pair located on the upstream side.