JPH0124563B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a circular cross-section metal material such as a round steel bar using an inclined rolling mill.

Round steel bars are generally manufactured through a rolling process using caliber rolls, but a method using an inclined rolling mill is being tried for the purpose of reducing equipment costs.

The "inclined roll rolling mill" disclosed in Japanese Patent Publication No. 46-43980 is well-known as a high-workability rolling mill that can reduce a solid material to a high degree in one pass. FIG. 1 is a front view of the rolled material 10 as seen from the exit side, FIG. 2 is a sectional view taken along the line --- in FIG. 1, and FIG. 3 is a side view showing the inclination angle β. Three cone-shaped rolls 11, 12, 13 (roll axes indicated by Y-Y) supported at one end, whose entrance diameter is sufficiently larger than the exit diameter of the rolled material 10, form the pass line. It is designed to rotate together with a roll housing (not shown) about X--X. The intersecting angle γ (referred to as α in the above publication), which is an important element in the present invention, is not specified in the publication, but it is -50° to -60° (the intersecting angle γ is defined as when the end of the roll shaft is the material to be rolled). 10
The angle of inclination β is 3° to 6°. As an effect, it is said that the surface twist of the rolled material 10 is small, but according to experiments conducted by the present inventors, no improvement effect on internal defects such as porosity was observed, and shear strain in the circumferential direction was not observed. is unsuitable for manufacturing high-quality round steel bars.

Also, “Plasticity and Processing” Vol. 7 No. 67 and Vol. 10 No.
In No. 104, papers entitled "Research on helical roll processing" are published as the first and second reports, respectively, and the technology related to this paper is shown in Figures 4-6 (similar to Figures 1-3). However, as shown in FIG. 4 (shown from the entry side), the material to be rolled 20 is rotated by rotating three cone-shaped rolls 21, 22, and 23 supported at both ends arranged around the material to be rolled 20. The cross angle γ is 0° and the inclination angle β is 0° ~ 0°.
The experimental results for the case of 14° are reported. According to this method, the shear strain in the circumferential direction is thought to be reduced compared to the above-mentioned known technique, but the surface torsion becomes large. According to the results of experiments conducted by the inventors of the present invention using this technique, a sufficient improvement effect on internal defects such as porosity cannot be obtained. It is also reported that rolling efficiency is poor and it is desirable to apply forward tension.

As mentioned above, there are many unresolved problems in the conventional round steel manufacturing technology using an inclined rolling mill, and the reality is that it has not been put to practical use.

The present invention was made against this technical background, and its purpose is to provide a method for manufacturing a circular cross-section metal material that can be rolled with a high degree of workability in one pass and has extremely high production efficiency. be.

Another object of the present invention is that the shear strain in the circumferential direction is extremely small, and even when rolling difficult-to-process materials (those with poor hot deformability), internal cracks occur from inclusions due to shear stress. An object of the present invention is to provide a method for manufacturing a metal material with a circular cross section.

A further object of the present invention is to make it possible to produce circular cross-section metal materials with high efficiency from billets (generally having center porosity) produced by continuous casting, i.e., by circumferential shearing. In addition to reducing strain and preventing internal fractures originating from porosity, so-called Mannesmann fractures, sufficient rolling is performed to compress porosity and reduce it itself. An object of the present invention is to provide a method that enables the production of a metal material having a circular cross section.

In the method for manufacturing a circular cross-section metal material according to the present invention, three or four rolls are arranged facing around the pass line, and the axis of each roll is arranged in the same direction around the pass line so that the center line thereof is non-parallel to the pass line. The roll is tilted in the direction, and the shaft end on the entrance side or the exit side of the roll can be tilted (crossed) so as to approach or move away from the pass line side, and supports the roll at each end. Using a cross-type inclined rolling mill, the inclination angle β and the crossing angle γ of the rolls satisfy the following conditions: 0° < γ < 15° 3° < β < 20° 5° < γ + β < 30° It is characterized by including the steps of reducing the outer diameter of the rod-shaped material in the state and stretching and rolling it.

Next, the method of the present invention will be specifically explained based on the drawings showing its implementation state.

FIG. 7 is a front view showing the rolling state from the entry side of the material to be rolled 30 when the method of the present invention is carried out with three rolls, FIG. 8 is a sectional view taken along the line - in FIG. 7, and FIG. 9 is an inclination angle. It is a side view showing β. The three rolls 31, 32, 33 have gorge portions 31a, 32a, 33a at the exit end of the rolled material 30,
With the gorge as a boundary, the diameter of the inlet side of the rolled material 30 is gradually reduced toward the shaft end, and the outlet side is enlarged to form inlet surfaces 31b, 32b, and 33b in the shape of a truncated cone.
and outlet surfaces 31c, 32c, and 33c. Such cone-shaped rolls 31, 32, 3
3 are the entrance surfaces 31b, 32b, 33b.
is located on the upstream side in the moving direction of the rolled material 30, and the axis YY and the gorge portion 31a,
32a, 33a (hereinafter referred to as the roll setting center; similarly shown in FIGS. 1 to 6) is passed on the same plane orthogonal to the pass line XX of the rolled material 30. They are arranged at approximately equal intervals around the line XX. The axial center line Y-Y of each roll 31, 32, 33 is aligned with the pass line X of the rolled material 30 around the roll setting center.
- As shown in FIG. 8, in relation to
As shown in Fig. 9, the front shaft end is the material 3 to be rolled.
0 toward the same side in the circumferential direction by an inclination angle β. The rolls 31, 32, and 33 are connected to a drive source (not shown) and are driven to rotate in the same direction as shown by arrows in FIG. 7, and the hot rolled material 30 caught between these rolls is While being driven to rotate around its axis, it is moved in the axial direction, that is, it is moved in a spiral manner, while its outer diameter is reduced and it is subjected to high pressure.

The cross-sectional shape of the hot-rolled material 30 is preferably circular, but may be a hexagonal or more polygonal shape. This is because the material to be rolled is rolled while being rotated, so if the material has few corners, the impact on the rolling mill will be large, which is undesirable, and a rectangular cross section is not suitable.

Now, as mentioned above, in the method of the present invention, γ,
The conditions described above are imposed on β and γ+β. The upper limit of γ is set to 15° because if it exceeds this value, interference will occur between the roll end face and the portion of the roll chock closest to the pass line on the downstream side in the moving direction of the rolled material. In addition, the lower limit value was set to 0° because if it is less than that, that is, γ = 0 or negative, shear deformation in the circumferential direction near the center of the rolled material can be eliminated and dimensional accuracy in the longitudinal direction can be ensured. Because it becomes impossible.

The reason for setting the upper limit value of β to 20° is the same as the reason for specifying the upper limit value of γ. The lower limit was set at 3° because if it is less than that, it is impossible to reduce the shear deformation in the circumferential direction near the center of the rolled material and obtain a sufficient porosity crimping effect in the continuously cast rolled material. It is.

The reason why we set the upper limit value of γ + β to 30 degrees is that if it exceeds 30 degrees, not only will the interference between the roll chock and the roll become significant as described above, but it will also become difficult to keep the bearing that supports the roll in the roll chock, and the This is because the holding structure cannot be maintained. The lower limit value of γ + β was set at 5° because below this, practical rolling efficiency (speed) cannot be secured.
Moreover, it becomes difficult to press the porosities of the continuously cast rolled material.

The upper limit values of γ, β, and γ+β mentioned above will be explained in more detail.

Figures 20 to 23 are partial cross-sectional front views of an inclined rolling mill equipped with rolls 31, 32, and 33, and Q in Figure 20.
- Q-line sectional view, side view, and rear view, and as shown, the roll shaft 2b on the pass line exit side F is supported by the fixed housing 7 via the chock 5, and
A roll shaft 2a on the pass line entry side E is supported by a rotary housing 8 via a chock 6. Each chock 5, 6 is moved along the radial direction of the pass line XX by the operation of the lowering means 9, 91.
- It is configured so that it can approach or leave X. The rotating housing 8 has a pass line XX
is the center of rotation, and the guide surface 7a of the fixed housing 7
is guided by the arrows H and I by the rotation operation means 92.
It is configured so that it can be rotated in forward and reverse directions. Then, the inclined rolling mill 1 determines the material and outer diameter of the material to be rolled.
When conditions such as temperature and area reduction rate are given, the outer diameter of the gorge portion of each roll 31, 32, 33, each roll 3
The intersection angles γ and inclination angles β of 1, 32, and 33 are selected, and the positions of the chucks 5 and 6 and the rotational position of the rotary housing 8 corresponding to the selections are set to predetermined positions. Each role 31, 3 set in this way
The axes YY of 2 and 33 intersect (incline) with the pass line XX at a predetermined intersection angle γ and are also inclined at a predetermined inclination angle β. At this time, the bearing cases 5a and 6a, which house the bearings that directly support the roll shafts 2a and 2b, are spherically received within the chock 5 and 6 (see Fig. 21), so that the roll shafts can cross each other arbitrarily and It is designed to be able to follow tilting movements.

Although the inclination rolling mill having three rolls has been described above, the structure of the inclination rolling mill having four rolls is basically the same as the structure of the inclination rolling mill having three rolls. In other words, if the rolls are arranged at 120° intervals around the pass line, there will be 3 rolls, and if the rolls are arranged at 90° intervals around the pass line, there will be 4 rolls. The supporting method and structure are the same. Therefore, the reason for limiting the upper limit values of γ, β, and γ+β, which are determined in relation to the interference between the roll and the roll chock, will be explained by focusing on one roll axis.

24 and 25 are schematic diagrams showing the roll intersection angle γ. FIG. 24 shows the state immediately after the rolls are assembled, and FIG. 25 shows the state where the roll intersection angle γ is set to 15°. As understood from Fig. 25, γ=
If the angle is 15°, the roll end face and chock 5 will interfere. 26 and 27 are schematic diagrams showing the roll inclination angle β. FIG. 26 shows the state immediately after the roll is assembled, and FIG. 27 shows the state in which the roll inclination angle β is set to 20°. As can be seen from Figure 27, β=
If the angle is 20°, the end face of the roll and chock 5 will interfere with each other.

Furthermore, if the crossing angle γ and the inclination angle β are set at the same time, the above-mentioned interference is likely to occur, and unless γ+β<30°, the above-mentioned interference will occur. Also, if you try to set the roll axis at such a high crossing angle and high inclination angle, the roll axis will be inclined at a large angle with respect to the vertical direction of the chock. It will no longer be possible to hold it in the shaded area.

From the above, the upper limit values of γ, β, and γ+β are determined.

Next, the lower limit values of γ, β, and γ+β will be explained. When a metal material with a circular cross section is rolled with two rolls, a tensile stress called secondary tension is generated in the central region as shown by hatching in FIG. This tensile stress causes shear deformation.

In the case of using three rolls, the above tensile stress is generated in the annular region of the central part excluding the central part as shown in FIG. Although this area is smaller than in the case of two rolls, it still causes shear deformation.

However, in the present invention, γ>0°, β>3°, γ+β
When the condition of >5° is satisfied, the above-mentioned tensile stress is suppressed and it becomes possible to eliminate shear deformation.

When using four rolls, the area where the above tensile stress occurs is even smaller, and the lower limit values of γ, β, and γ+β are each
It is also good if it is larger than 0°, 3°, or 5°.

Comparing the conditions of γ and β with the values of γ and β of the conventional technology described above, there is a noticeable difference in that the value of γ is positive. It is effective in suppressing
The purpose of providing the roll with a support structure at both ends is to strengthen the mill rigidity and prevent the occurrence of spiral marks, and the support structure itself is known from the above-mentioned "Research on helical roll processing."

Next, the results of various experiments carried out to clarify the effects of the method of the present invention will be explained. All materials to be rolled were S45C carbon steel, and were heated and rolled at 1200°C.

Example 1 Shear strain in the circumferential direction Five pins 40 were inserted in parallel to the axial direction as shown in Fig. 10 for a base material with a diameter of 70 mm and a length of 300 mm.
(2.5mmφ) are embedded so that they are located on the same radius, and the pin 4 after rolling as shown in Figure 11.
The shear strain in the circumferential direction in the cross section of the rolled material was investigated using a flow of 0 (representing metal flow).

The rolling conditions are that the inclination angle β is fixed at 7°, and the crossing angle γ is set in three ways: 9°, which is within the scope of the present invention, and 0° and -9°, which are outside the scope of the present invention. The area reduction was varied in four ways: 90%, 70%, 75%, and 80%. The results are shown in FIG. 12, where the flow of pins is connected with solid lines. This result shows that when the area reduction is small, there is no big difference in the effect of the intersection angle γ, but as the area reduction becomes larger, there is a difference in the shear strain in the circumferential direction, and it is the smallest when γ = 9°. it is obvious. And γ=
When γ=9°, no shear strain in the circumferential direction appears at the center of the cross section of the rolled material (metal flow exhibits a straight shape), but when γ=-9°, the cross section including the center of the cross section Clear circumferential shear deformation appears throughout the interior.
Note that when γ=0°, the state is intermediate between the two. In other words, by setting γ>0° and increasing the value of γ, shear strain at the center of the cross section of the rolled material can be prevented. The absence of shear strain in the circumferential direction means that there is no shear stress field in the circumferential direction, and therefore, in the case of the present invention, cracks from the center porosity do not occur, and so-called Mannesmann fracture does not occur. .

Example 2 Crimping performance of center porosity 2mmφ, 4
mmφ, 6mmφ hole (simulating center porosity)
The inclination angle β=
The degree of crimping due to rolling was examined by changing the angle in six ways between 3° and 13°. As in Example 1, the intersection angle γ was set to three values: γ = 9°, which is within the range of the present invention, and γ = 0°, -9°, which are outside the range of the present invention. The area reduction was 53% (70mmφ→33mmφ). 13th
Figures a, b, and c show the results.

The following points are clear from this result. That is, γ=
In the case of 9 degrees, artificial holes up to 4 mmφ are crimped at β = 13 degrees, but in the case of γ = -9 degrees, even the smallest artificial holes of 2 mmφ are not crimped even if β = 13 degrees. When γ=0°, it is between the two, and when β=13°, an artificial hole of 2 mmφ is crimped. In addition, regardless of the crossing angle γ, the inclination angle β affects the diameter reduction function of the artificial hole.
The larger β is, the greater the diameter reduction effect is.

From this, it can be said that the crimp performance of the center porosity becomes higher as γ>0°, and the higher the crossing angle and the higher the inclination angle are set.

Example 3 Crimping performance of center porosity Next, the crimp performance of actual center porosity was investigated using a base material obtained by continuous casting.

The material to be rolled is a round steel machined into a diameter of 70 mm and a length of 300 mm using the center part of a 380 mmφ large cross-section continuously cast slab.
φ→33mmφ). The rolling conditions are inclination angle β=
4 degrees, 8 degrees, 12 degrees, intersection angle γ = 9 degrees, 0 degrees, -9 degrees.
There were a total of 9 streets. Then, the rolling mill was stopped during rolling, a stopper was made, and the rolling condition of the porosity was investigated by cutting it in half. The photograph in FIG. 14 shows this condition. The following points became clear from these results.

) When the intersection angle γ = -9°, there is a so-called Mannesmann fracture phenomenon in which the defect starts from the porosity of the base material and expands due to shear stress in the circumferential direction. This tendency is improved as the inclination angle β becomes larger, but it is difficult to obtain sound internal properties.

) When the crossing angle γ = 9°, the porosity is completely crimped even if the inclination angle β is low.

) When the crossing angle γ = 0°, the state is intermediate between the two, and when the inclination angle is large, the porosity crimping condition is good.

From these results, when continuously cast slabs are used as rolled material, it is difficult to press porosity and γ
A high crossing angle of >0° and a high inclination angle are desirable.

Example 4 Surface Twist The present invention is inferior to the two known techniques described above in terms of surface twist. Figure 15 a, b
As shown in the figure, a groove 41 with a depth of 1 mm and a width of 1 mm is formed in the axial direction on the surface of a base material with a diameter of 70 mm and a length of 300 mm, resulting in an area reduction of 78% (70 mmφ → 33 mmφ).
It was rolled at FIG. 17 shows the results of measuring the twist angle of the groove 41 after rolling in this case (the angle formed by the groove trace and a straight line on the surface parallel to the axis line as shown in FIG. 16). The rolling conditions are that the inclination angle β is 3°~
There are 6 different angles of 13° and 3 different angles of intersection γ of 9°, 0°, and -9° for a total of 18 different angles. The following points are clear from this result.

) When γ=-9°, the surface twist is small.

) When γ=9°, the surface twist is large. However, this drawback can be compensated for by increasing the inclination angle β.

) When γ=0°, it is between the two.

In other words, when implementing the present invention, it is desirable to set the inclination angle β to a high value in order to reduce the surface twist.

Example 5 Dimensional accuracy in the longitudinal direction A base material with a diameter of 70 mm and a length of 300 mm was rolled at an area reduction of 67% (70 mmφ→40 mmφ), and dimensional changes in the longitudinal direction were investigated. There are three rolling conditions: the inclination angle β is 4°, and the crossing angle γ is 9°, 0°, and −9°. Figures 18a, b, and c show the results. According to this, when γ = 9°, ±0.10%, when γ = -9°, ±0.75%,
At γ=0°, it shows about ±0.17% between the two, and γ＞
It is clear that 0° is effective in ensuring dimensional accuracy.

Example 6 Rolling speed A base material with a diameter of 70 mm was subjected to an area reduction of 78% (70 mm
The rolling speed was investigated when rolling from φ to 33 mmφ). Rolling conditions are roll rotation speed: 130R.PM,
The diameter of the gorge part of the roll is 190 mmφ, and there are 6 inclination angles β from 3° to 13°, and 3 crossing angles γ of 9°, 0°, and -9°.
There were a total of 18 streets. FIG. 19 shows the results, showing that the rolling speed is the highest when γ=9°, and that the rolling speed tends to increase as the inclination angle β increases. Therefore, in order to improve rolling efficiency, it is preferable that γ>0°, preferably a high crossing angle, and a high inclination angle.

As described above, in the case of the method of the present invention, it is possible to perform inclined rolling without causing the so-called Mannesman fracture, which is caused by porosities, and therefore it is possible to realize a rolling line with an innovative high processing rate, and thereby, round steel bars, etc., can be rolled in a circular shape. It becomes possible to dramatically increase the production efficiency of cross-sectional metal materials. Furthermore, even when a continuous cast material with center porosity is used as the base material, the porosity can be crimped, and it is possible to realize a rolling line that is continuous with the continuous casting machine without causing cracks. However, production efficiency can be improved and thermoeconomic benefits can be enjoyed.

Furthermore, in the case of the present invention, since the shear strain in the circumferential direction is small, there is no possibility of internal cracks starting from inclusions, making it possible to manufacture with high efficiency even when using difficult-to-process materials. The invention has excellent effects.

[Brief explanation of drawings]

FIG. 1 is a front view schematically showing the structure of a conventional inclined roll rolling mill, FIG. 2 is a sectional view taken along the line - in FIG. 1, FIG. 3 is a side view showing the inclination angle β, and FIG.
The figure is a front view schematically illustrating the conventional method for inclined rolling of round steel materials, FIG. 5 is a cross-sectional view taken along the line - in FIG. 4, FIG. 6 is a side view showing the inclination angle β, and FIG. 7 is the present invention. A front view schematically showing the structure of an inclined rolling mill used for carrying out the method, FIG. 8 is a sectional view taken along the line - - of FIG. 7, FIG.
Figure 0 is a cross-sectional view of the sample for shear strain measurement, No. 11.
The figure is a cross-sectional view showing an example of the shape after rolling.
Figure 2 is a display diagram of the measurement results of shear strain, Figure 13a,
b, c are graphs showing the inner diameter of the artificial hole after rolling, Fig. 14 is a photograph of the longitudinal cross-sectional structure of the material to be rolled after rolling, Fig. 15 a, b is a front view showing the sample for surface twist measurement; 16 is a side view showing the groove form after rolling; FIG. 17 is a graph showing the surface torsion measurement results; FIGS. FIG. 19 is a graph showing the rolling speed measurement results. Figure 20 is a partial cross-sectional front view of the inclined rolling mill, and Figure 21 is the second
22 is a side view, 23 is a back view, 24 and 25 are illustrations of the intersection angle, and 26 and 27 are inclination angles. 28 and 29 are explanatory diagrams of shear deformation. 31, 32, 33...roll, 31a, 32a,
33a...gorge part, 31b, 32b, 33b...inlet surface, 31c, 32c, 33c...exit surface, 30...
Rolled material.

[Claims]

1. In a housing that rotates around the pass line of the material to be rolled, three or four rolls each rotated around their respective axes are placed in the same direction around the pass line so that their axes are not parallel to the pass line. Using an inclined rolling mill, which is tilted by an inclination angle β to A metal with a circular cross section, comprising the step of setting the angle γ to satisfy 3° < β < 45°, 0° < γ < 60°, and stretching and rolling the material to be rolled without rotating it around its axis. Method of manufacturing wood.