JP6137080B2 - Slab forging method - Google Patents

Description

  The present invention relates to a slab forging method. In particular, even when a slab having a large slab width / thickness ratio is forged, it is intended to improve the porosity crimping ability of the slab and improve the finished shape.

In general, when the product thickness is large and the total reduction ratio from the slab is small, it is difficult to properly press the porosity defect existing in the center portion of the slab thickness only by hot rolling. Therefore, in such a case, a forging process having a large strain applied to the center portion of the plate thickness is applied.
In particular, when an excellent porosity crimping capability is required, a forging method using a so-called asymmetric anvil with different widths of anvils is used (for example, Patent Documents 1 to 3). Here, the width of the anvil means the length of the anvil parallel to the slab feed direction during forging (l ₁ and l _{2 in} FIG. 1).

Japanese Patent No. 4543980 JP 2011-140043 A Japanese Patent No. 2854215

  Usually, since the width of the slab and the width of the final product are different, at the time of forging, first the width direction is reduced to adjust the width size, and then the thickness direction is reduced. In such forging, if the width direction of the slab is reduced using an asymmetrical anvil, that is, if the width is reduced with the contact length and the contact position of the upper and lower anvils differing from each other, the deformation becomes asymmetrical in the vertical direction and the width warps. Will occur.

  When the slab rolling is performed after the forging process as described above in a state where the width warpage has occurred, meandering and further shape defects are induced, and rolling defects and yield reduction are caused.

  In addition, since the width of an anvil is usually very short relative to the slab length, it is extremely difficult to correct the width warp during forging, and even if it can be corrected, the forging efficiency is greatly increased in that case. descend.

  As a method for solving the above problem, the reduction performed using the upper and lower asymmetric anvils is limited only to the reduction in the thickness direction, and the reduction in the width direction is considered to be performed using the upper and lower symmetrical anvils. It is necessary to reassemble the anvil between the reduction in the width direction and the reduction in the thickness direction, which also causes a significant reduction in forging efficiency.

  The present invention advantageously solves the above-mentioned problem, and even when the slab width direction reduction and the thickness direction reduction are continuously performed using an asymmetrical anvil, the occurrence of width warpage during the width direction reduction is achieved. It aims at providing the slab forging method which suppressed and improved the porosity crimping | compression-bonding capability and the finished shape, without causing the fall of forging efficiency.

Now, in order to solve the above-mentioned problems, the inventors have focused on the contact state of the upper and lower anvils with the slab during the width direction reduction, and as a result of intensive studies, the following knowledge has been obtained.
It was found that the cause of the width warp when the slab was reduced in the width direction was an asymmetrical deformation caused by a shift in the down position of the upper and lower anvils or a difference in contact length between the upper and lower anvils.

Therefore, the reduction in the width direction is performed from the longitudinal end portion of the slab, and the shift of the end position of the upper and lower anvils (slab longitudinal center side) is made relative to the shorter contact length of the upper and lower anvil contact lengths. When it was controlled to a certain value or less, it was found that the vertical asymmetric deformation is suppressed and the width warpage is reduced.
The present invention was developed after further studies based on the above findings.

That is, the gist configuration of the present invention is as follows.
1. In the slab forging method consisting of continuously applying a reduction in the width direction and then in the thickness direction using an asymmetric anvil with different widths of the upper and lower anvils,
The width reduction is performed from the end in the longitudinal direction of the slab. At that time, the amount of deviation of the end position of the upper and lower anvils at the longitudinal center side of the slab is ΔL, and the contact length of the upper and lower anvils with the slab is A slab forging method characterized by limiting the ratio ΔL / B to 0.20 or less when the shorter contact length is B.

2. 2. The slab forging method according to 1 above, wherein a width / thickness ratio of the slab is 2.0 or more.

  According to the present invention, the forging using the upper and lower asymmetric anvils with high porosity crimping capability can be improved not only in the thickness direction reduction but also in the width direction reduction, and the finished shape of the slab after forging can be improved, It is extremely useful in industry.

It is the figure which showed the state which performs the width direction reduction of a slab using the asymmetrical anvil from which the width | variety of an upper anvil and a lower anvil differ. It is the figure which showed the evaluation point of the width curvature of a slab.

Hereinafter, the present invention will be specifically described with reference to FIG.
FIG. 1 shows a state in which the slab is reduced in the width direction using an asymmetrical anvil with different widths of the upper and lower anvils. In the figure, reference numeral 1 is an upper anvil, 2 is a lower anvil, and 3 is a slab. In this example, the upper anvil 1 has a shorter anvil M ₁ , while the lower anvil 2 has a longer anvil M. ₂ is shown. In the figure, l ₁ indicates the width of the anvil M ₁ and l ₂ indicates the width of the anvil M ₂ . B ₁ represents the contact length of the anvil M ₁ with respect to the slab, and B ₂ represents the contact length of the anvil M ₂ with respect to the slab. Therefore, in this example, the contact length B with the shorter contact length with the slab among the upper and lower anvils refers to B ₁ . Further, ΔL indicates the amount of deviation of the end positions of the upper and lower anvils on the slab longitudinal center side.

Now, in the case shown in FIG. 1, when the reduction in the width direction is performed from the end in the longitudinal direction of the slab, the shift amount ΔL of the end position (slab longitudinal center side) of the upper and lower anvils is gradually reduced. As a result, by reducing this ΔL, specifically, ΔL is set to 0.20 or less with respect to the contact length B (B _{1 in} this example) of the upper and lower anvils with the shorter contact length to the slab. In this case, it was found that the vertical asymmetric deformation is effectively suppressed and the width warpage is reduced. A more preferable range of ΔL is 0.10 or less with respect to the contact length B of the shorter contact length.

At this time, the contact length B ₁ of the anvil M ₁ towards the contact length is short, it is preferable to set the the (0.60 to 1.00) times the width l ₁ of the anvil M _1. This is because if B ₁ is less than 0.60 times l _1, the number of buses increases and the forging efficiency decreases. A more preferred B ₁ / l ₁ ratio is in the range of 0.80 to 0.95.

  As described above, even if the widths of the upper and lower anvils are different, and the center position of the upper and lower anvils is shifted, the reduction in the width direction against the slab is preferably performed under an appropriate contact length and still By controlling the shift amount of the end position of the anvil (slab longitudinal center side) within a specified range, the deformation position by the upper and lower anvils is equal to the surface pressure, effectively suppressing the width warpage during the reduction. It was determined that it could be done.

In FIG. 1, the shift amount ΔL of the end positions of the upper and lower anvils is larger in the contact length B ₁ of the upper anvil M _{1 having} a shorter width than the contact length B ₂ of the lower anvil M ₂ having a larger width. Although shown for a short case, when the relationship of the contact length of the opposite, namely even when towards the contact length B ₂ of the lower anvil M ₂ is shorter than the contact length B ₁ of the upper anvil M _1, Similar effects can be obtained.

  The present invention is particularly suitable by applying a slab having a width / thickness ratio of 2.0 or more, which has been concerned about the occurrence of width warpage in the past in the width direction reduction.

In addition, in order to adjust the deviation | shift amount of the edge part position of an up-and-down anvil, the method of sliding an up-and-down each anvil position is mentioned.
Further, the present invention is not affected by the component composition of the slab to be pressed, and thus can be applied to a slab having any component composition.

Table 1 also shows the results of investigating the amount of warpage of the slab after the reduction when the slab is reduced in the width direction under various conditions shown in Table 1.
As shown in FIG. 2, the slab width warpage amount is represented by L as the length of the slab after reduction in the width direction, and ΔW _{max as} the distance from the line connecting both width ends of the slab to the deepest portion of the warp. In this case, ΔW _max / L × 100 (%) was evaluated, and the case where this value was 0.8% or less was regarded as acceptable.

As shown in the table, No. 1 in which the slab was reduced in the width direction under the conditions according to the present invention. In all of Nos. 1 to 7, the amount of displacement of the end portion of the upper and lower anvils at the longitudinal center side of the slab was sufficiently small with respect to the anvil contact length, so that the amount of width warp produced was small.
On the other hand, No. 1 in which the width direction reduction was performed under conditions deviating from the present invention. In Nos. 8 to 13, since the shift amount of the end position on the slab longitudinal center side of the upper and lower anvils is large, as a result of the asymmetrical deformation in the vertical direction, the width warpage is large.

1 Upper anvil 2 Lower anvil 3 Slab

Claims (2)

In the slab forging method consisting of applying a reduction in the width direction and then in the thickness direction continuously using an asymmetric anvil with different widths of the upper and lower anvils,
Shall perform a reduction of the width direction from one end of the slab length side direction, time, the shift amount of the edge position of the upper and lower anvil at the other end side of the slab longitudinal direction [Delta] L, the vertical Anvil A slab forging method characterized by limiting the ratio ΔL / B to 0.20 or less, where B is the contact length of the shorter contact length with the slab.   The slab forging method according to claim 1, wherein the width / thickness ratio of the slab is 2.0 or more.

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