JP2002102987A - Heat forging method for billet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat forging method for a billet capable of forging a material, whose cross-sectional shape is polygonal or circular, into a billet small in the depth of recesses and having a polygonal or circular shape. SOLUTION: In the heat forging method for forging the material into the billet whose cross-sectional shape is circular or polygonal by feeding the material, whose cross-sectional shape is polygonal or circular, in the longitudinal axial direction at the opening time of a pair of round-grooved anvils or V- grooved anvils making opening/closing operation, and rotating the material around its axial center, performing the forging for pressing down the material a plurality of times at the closing time of the round-grooved anvils or the V- grooved anvils, the rotation angle around the axial center of the material at each opening time of the anvils is made larger than 45 deg. and not more than 75 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to carbon steel, alloy steel,
The present invention relates to a hot forging method for a steel slab which is made of stainless steel or a high alloy and has a polygonal or circular cross section to forge a steel slab having a circular or polygonal cross section.

[0002]

2. Description of the Related Art Generally, the following three methods are used to produce round steel slabs by hot forging.

[0003] The first method is a method of performing rough molding using a flat metal sheet. That is, the opposite surface of a rectangular material (steel ingot, bloom, etc.) having a square or rectangular cross section is pressed down alternately using a pair of flat anvils to have a small size, for example, a cross section having a substantially square shape. Form into intermediate material. Next, similarly to the above, the cross-sectional shape is substantially regular hexagonal or more through a process of forming the cross-sectional shape into a substantially regular octagon by alternately pressing down the corner portions of the intermediate material using a pair of flat anvils. Is roughly formed into a polygonal coarse round material. Thereafter, using a pair of anvils having round grooves formed thereon (hereinafter referred to as “round groove anvils”), finish round forming is performed by spiral forging into round steel pieces having a predetermined outer diameter and a circular cross section.

[0004] A second method is a method of performing rough molding using an anvil provided with a V-groove (hereinafter referred to as a V-groove anvil).
Specifically, for the intermediate material whose cross-sectional shape is formed into a substantially square or regular octagon in the first method,
After performing spiral forging for roughly forming a rounded material having a polygonal cross section of approximately a regular hexagon or more using a pair of V-groove anvils, similarly to the above, using a round-groove anvil, A round steel slab having an outer diameter and a circular cross section is finish-formed by spiral forging.

A third method is to use a large round cast slab having a circular cross section manufactured by continuous casting as a material, and a pair of V
Using a grooved anvil or a flat anvil, after performing a spiral forging to roughly form a cross section of a roughly round hexagonal or larger polygonal round material, in the same manner as described above, using a circular anvil A round steel slab having an outer diameter and a circular cross section is finish-formed by spiral forging.

In the above-mentioned method, spiral forging means that when a pair of anvils that open and close are opened, the material is fed in the axial direction and is rotated around its axis by a predetermined angle, and Is a forging method in which the forging for rolling down the material is performed a plurality of times during the closing operation of the forging. In the following description, each forging in the above-mentioned multiple forgings is called a shot.

[0007] In the hot forging method through the above-described steps, in any of the first to third methods, a round groove anvil described below is used for finish molding. Used.

FIG. 1 is a view showing an example of a commonly used round groove anvil, wherein FIG. 1 (a) is a plan view, FIG. 1 (b) is a sectional view taken along the line II--II of FIG. FIG. 4C is a cross-sectional view taken along the line VII-VII of FIG.

As shown in FIG. 1, a round groove anvil 1 has a groove bottom 1 a having a radius of curvature Rg and a width H formed with an offset amount G such that the depth at the center of the groove bottom is D, and It is a semicircular hole type having a relief portion 1b formed with a radius of curvature Rc on both sides of the bottom portion 1a, and has a circular groove having a constant depth D except for both longitudinal ends of the anvil. Also, chamfered portions 1c having a radius of curvature Rb are provided at both ends in the longitudinal direction of the anvil.
Perch surfaces 1f are formed on both sides in the width direction. Then, the hot finished outer diameter of the round slab to be obtained is set by adjusting the offset amount G.

In the rough forming by the spiral forging in the second and third methods, a V-groove anvil described below is used.

2A and 2B show an example of a commonly used V-groove anvil. FIG. 2A is a plan view, FIG. 2B is a sectional view taken along the line II-II of FIG. FIG. 3C is a cross-sectional view taken along the arrowed line of FIG.

As shown in FIG. 1, a V groove anvil 2 has a groove bottom 2a having a radius of curvature Rg formed with an offset G so that the depth at the center of the groove bottom is D, and a groove bottom 2a.
V formed by an inclined portion 2d having an apex angle α formed on both sides of the inclined portion and a relief portion 2b having a radius of curvature Rc formed on both sides of the inclined portion.
It has a V-shaped groove having a constant depth D except for both ends in the longitudinal direction of the anvil. A chamfer 2c having a radius of curvature Rb is formed at both ends in the longitudinal direction of the anvil, and a perch surface 2f is formed at both sides in the width direction. Then, the diagonal distance of the coarse round material of the polygon to be obtained is set by adjusting the offset amount G.

FIG. 3 is a view for explaining a method of finish forming by spiral forging using a round groove anvil, and FIG.
Is a sectional view showing a state after forging of the first shot, FIG. 4B is a sectional view showing a state before starting forging of the second shot, and FIG. It is sectional drawing which shows a state.

In FIG. 1A, a round groove anvil 1 having the shape shown in FIG. 1 is used. One pair of the round groove anvils 1 is arranged to face a press (not shown) and opens and closes by driving the press. For example, the material 3 having a substantially regular hexagonal cross section is subjected to the first shot forging on the entry side by the closing operation of the pair of round groove anvils 1. By this forging, the material 3 is filled in the groove bottom 1a of the round grooved anvil 1, and a part of the material 3 bites between the escape portions 1b of the round grooved anvil 1, thereby forming a biting portion 3a.

[0015] Forging of the first shot is completed,
Is opened, the transport unit (not shown) feeds the material 3 in the axial direction by a predetermined amount and rotates the material 3 around its axis by, for example, a rotation angle θ = 40 degrees, as shown in FIG. As described above, the protruding portion 3a of the material 3 is attached to the groove bottom 1 of the round groove anvil 1.
Rotate to a side.

After that, the forging of the second shot is performed by the closing operation of the round groove anvil 1. In the second shot forging,
The protruding portion 3a generated by the first shot forging is the groove bottom 1
a, the biting portion 3a becomes the groove bottom 1a.
It flows along and disappears. At this time, the starting portion 3a
In the vicinity of the portion where is formed, a dent 3c is generated and a new biting portion 3b is generated. This state is shown in FIG.

The dents 3c formed by the second shot forging remain until the end of the subsequent spiral forging, thereby deteriorating the roundness of the finished round steel slab. In particular, when the cross-sectional dimension of the coarse round material becomes larger than a predetermined size due to abrasion of the flat anvil or the V-groove anvil and a change in friction coefficient at the time of the rough forming in the previous process, the first shot forging is performed. The resulting protruding portion 3a becomes large, the dent 3c produced in the second shot also becomes large, and the roundness after forging becomes worse.

In order to avoid the occurrence of the large biting portion 3a, a slightly underfill state is set in anticipation of the dimensional variation of the coarse round material, that is, the rolling allowance in the finish molding is reduced, and the material is removed from the groove bottom 1a. When the forging is carried out in a state where is not completely filled, the round steel slab after finish forming has a local flat surface in the circumferential direction and the axial length direction, and a round steel slab with satisfactory roundness is obtained. There was a problem that it could not be obtained.
The problem is that when forging ferritic stainless steel, duplex stainless steel, etc., which have a large width spread during rolling,
It becomes particularly noticeable. In addition, the above problem is caused by a spiral forging in which a material having a polygonal or circular cross section is roughly formed into a roughly round hexagonal or larger polygonal cross section using a V-groove anvil. Also occurs.

In addition to the spiral forging method using the circular grooved anvil 1 shown in FIG. 1 or the V-groove anvil shown in FIG. 2, a spiral forging method using an anvil provided with grooves is disclosed in Japanese Patent Laid-Open No. 6-71377. Gazette and JP-A-11-5792
No. 4 discloses this.

The forging method disclosed in Japanese Patent Application Laid-Open No. 6-71377 uses an anvil having a tapered round groove in which the diameter of the groove continuously decreases from the entry side to the exit side, and has a rotation angle of 45 degrees. / This is a forging method in which a material having a square cross section is directly finish-formed into a round steel piece having a circular cross section by spiral forging of shots.

In addition, the forging method disclosed in Japanese Patent Application Laid-Open No. 11-57924 discloses a forging portion having a V-groove on the entry side,
Finished by spiral forging with a rotation angle of 45 degrees / shot, using a metal finish with a connecting part formed by a groove that changes from a V-groove to a round groove in the middle, with a finish made of a round groove on the exit side. This is a forging method for molding.

However, in any of these forging methods, the offset amount G (see FIG.
(Refer to (b)), there is a gap between the pair of anvils, and it is inevitable that a forging of the first shot causes a biting portion. After that, the material is rotated 45 degrees around its axis, and then the second shot is forged, so that the occurrence of a large dent cannot be prevented.

[0023]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for hot forging a steel slab which can minimize the depth of a locally formed dent in both rough forming and finish forming. To provide.

[0024]

SUMMARY OF THE INVENTION The gist of the present invention is that a material having a polygonal or circular cross section is fed in the axial direction at the time of opening a pair of round groove anvils or V-groove anvils that open and close, and the shaft thereof is rotated. Rotate around the center,
In the hot forging method of performing forging to reduce the material a plurality of times during the closing operation of the grooved anvil and forging into a steel slab having a circular or polygonal cross section, the forging of the material at each opening operation of the anvil is performed. A hot forging method for a steel slab, wherein the rotation angle is more than 45 degrees and not more than 75 degrees.

In the present invention, the time of the opening operation means the time when the anvil opening and closing operation is not in contact with the material.

[0026] The present inventors have found that when a material having a substantially hexagonal cross section is formed into a round steel slab having a circular cross section by spiral forging using a round groove anvil, the anvil is opened. The following findings were obtained by investigating the effect of the rotation angle about the axis of the material during operation. The present invention is an invention made based on this finding.

1) When the material is spirally forged, the largest portion is formed when the material is first forged on the entry side of the round groove anvil. A local dent is formed in the vicinity of the biting portion.

2) This dent has a great influence on the roundness of the forged round steel piece remaining until the completion of the spiral forging.

3) This dent occurs regardless of the rotation angle of the material, but the depth of the dent depends on the rotation angle around the axis of the material, and the rotation angle is more than 45 degrees and 75 degrees. It is small in the following cases.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for hot forging a billet according to the present invention will be described in detail with reference to the drawings.

The hot forging method of the present invention is, for example, a hot forging method on the premise of a method of finish forming by spiral forging using a round groove anvil as described with reference to FIG.

That is, as shown in FIG. 1A, a pair of round groove anvils 1 which are arranged opposite to a press (not shown) and open / close by driving the press, have a substantially hexagonal cross section. Forging of the first shot of the material 3 is performed.

After the forging of the first shot is completed, the round groove anvil 1
Is opened, as shown in FIG. 2B, the transport unit (not shown) feeds the material 3 in the axial direction by a predetermined amount, and
Is rotated around its axis by a rotation angle θ, and FIG.
As shown in the figure, forging of the second shot is performed. By repeating the above forging a plurality of times, a material having a substantially regular hexagonal cross section is finish-formed into a round steel slab.

In the forging of the second shot, the dent 3
The reason why c occurs is as described above, and the reason will be described with reference to FIGS.

FIG. 4 shows that the rotation angle around the material axis is 40 degrees.
(A) is a diagram showing a state before the start of forging of the second shot, and (b) of FIG. It is a figure which shows the state after forging of a shot. FIG. 5 is an upper half sectional view for explaining a dent caused by the second shot forging when the rotation angle around the axis of the material is 90 degrees, and FIG. 5A shows the second shot forging. FIG. 4B shows a state before the start, and FIG. 4B shows a state after forging of the second shot.

As shown in FIG. 4, when the rotation angle about the axis of the material 3 is as small as about 40 degrees, the biting portion 3a shown in FIG.
As the fluid flows in the direction b, a recess 3c as shown in FIG. 3B is formed at the base 3d of the protruding portion 3a on the groove bottom 1a side.

On the other hand, as shown in FIG. 5, when the rotation angle of the material 3 around the axis is as large as 90 degrees, the biting portion 3a shown in FIG.
The base 3 on both sides of the protrusion 3a
The recesses 3c, 3d as shown in FIG.
c occurs.

As described above, when the rotation angle about the axis of the material 3 is 40 degrees, the root 3d on the side of the groove bottom 1a of the biting portion 3a is attached to the root 3d when the rotation angle is 90 degrees.
A dent 3c is formed in the roots 3d, 3d on both sides of a. The recess 3c is formed at one of the roots 3d of the protrusion 3a or at both of the roots 3d, 3d even when the rotation angle around the axis of the material is more than 40 degrees and less than 90 degrees.

FIG. 6 shows the rotation angle around the axis of the material 3 between the first shot and the second shot when the finish molding is performed using the round groove mold, and the dent after the completion of the forging of the second shot. FIG. 5 is a diagram showing a relationship with the depth of the image. As shown in the figure, when the rotation angle is 30 degrees to 45 degrees, the depth of the dent is largest. However, when the rotation angle exceeds 45 degrees, the depth of the dent sharply decreases, and when the rotation angle is 50 degrees, the depth of the dent becomes minimum. When the rotation angle is larger than 50 degrees,
The depth of the depression is slightly increased but is almost stable, and when it exceeds 75 degrees, the depth of the depression is increased again.

As described above, the depth of the dent is affected by the rotation angle about the axis of the material 3. If the rotation angle of the material is more than 45 degrees and not more than 75 degrees, the depth of the dent can be reduced. Can be. Therefore, in the forging method of the present invention, the material 3
Must be greater than 45 degrees and less than or equal to 75 degrees. In order to further reduce the depth of the recess, the lower limit of the rotation angle is desirably set to 47 degrees, and more desirably 50 degrees.

The material 3 in which the extruded portion generated by the forging of the first shot has disappeared by the forging of the second shot has a small dent 3c shown in FIG. The part 3b is generated. This material 3 is sent in a predetermined amount in the axial direction in the same manner as described above, and 45
After rotating over 75 degrees and below 75 degrees, forging of the third shot is performed. The biting portion 3b generated by the second shot forging is smaller than the biting portion 3a generated by the first shot forging. Therefore, the depth of the dent caused by the third shot forging is also small.

In this way, the raw material 3 is continuously forged by spiral forging and finish-formed into a round steel piece having a substantially perfect cross section.

In the above description, a round groove anvil is used.
Although a case where a material having a cross-sectional shape of a regular hexagon is finish-formed into a round steel piece has been described, a V-groove anvil may be used as the metal anvil, and the material has a polygonal shape other than a regular hexagon. You may. Further, the forging method of the present invention is also applied to a case where a material having a polygonal or circular cross-section is roughly formed into a coarse round material having a polygonal cross-section smaller than the material by using a V-groove anvil. be able to.

[0044]

EXAMPLE A rectangular ingot 40 made of SUS316 and having a length of about 2000 mm and an average side length of 490 mm and a rectangular cross section.
Using the book as a material, this material was heated to 1290 ° C and forged into a round steel piece with an outer diameter of 178 mm in one heat. It was roughly formed and finish-formed into a round steel slab using a round groove anvil.

The round groove anvil has a hot finished diameter of 172 to 184.
1 mm, G = 11 mm, D = 81
mm, Rg = 92 mm, H = 159.3 mm, Rc = 7
0 mm, Rb = 40 mm, and a total length of 300 mm were used, and the distance between the perch surfaces 1f at the time of reduction was set to 19.5 mm. The finish forming is a spiral forging with a feed amount of 23 mm / shot and a hot finish outer diameter of 18
A 1.5 mm round steel slab having a length of 15000 mm was finish-formed.

In the finish forming described above, the rotation angle in the spiral forging is set to 50 ° / shot and 75 ° / shot as an example of the present invention, and is set to 45 ° / shot and 80 ° / shot in the comparative example. , Each 10
Finished into round steel slabs. After allowing these round slabs to cool to room temperature in the atmosphere, the outer diameter was measured at a pitch of 30 degrees in the circumferential direction at a position 4000 mm away from the center and the end in the longitudinal direction of the round slab, and the true diameter at each position was measured. The circularity was measured. Further, the entire length of each round steel slab was visually observed, and the dent amount of the most significant dent portion was measured. The roundness was defined as the difference between the maximum outer diameter and the minimum outer diameter at each position in the longitudinal direction.

As a result, in the example of the present invention in which the rotation angle is 50 degrees / shot, the roundness is 2.0 to 0.6 mm, the depth of the recess is 1.0 to 0.3 mm, and the rotation angle is 75 degrees / shot. In the example of the present invention, the roundness was 2.6 to 1.0 mm and the depth of the dent was 1.3 to 0.5 mm. On the other hand, in the comparative example in which the rotation angle is 45 degrees / shot, the roundness is 4.1 to 3.0.
mm, recess depth 2.1 to 1.5 mm, rotation angle 80
In the comparative example of the degree / shot, the roundness is 3.6 to 2.8 m.
m, the depth of the dent was 1.8 to 1.4 mm. As described above, in the example of the present invention, the roundness is superior and the depth of the recess is smaller than that of the comparative example.

[0048]

According to the hot forging method of the present invention, a steel slab having a small depth of a dent can be manufactured. Round steel slabs can be manufactured.

[Brief description of the drawings]

FIG. 1 is a view showing an example of a commonly used round groove anvil, in which FIG. 1 (a) is a plan view, FIG. 1 (b) is a sectional view taken along the line II in FIG. 1 (a), and FIG. (A) is a cross-sectional view taken along the roll line in (a).

2 (a) is a plan view, FIG. 2 (b) is a sectional view taken along the line II in FIG. 2 (a), and FIG. 2 (c). (A) is a cross-sectional view taken along the roll line in (a).

FIG. 3 is a view for explaining a method of finish forming by spiral forging using a round groove anvil, and FIG. 3 (a) is a cross-sectional view showing a state after forging of a first shot, and FIG. Sectional view showing the state before the start of forging of the second shot, FIG.
FIG. 4 is a sectional view showing a state after forging of a second shot.

FIG. 4 shows a case where the rotation angle around the material axis is 40 degrees.
5A is a top half cross-sectional view for explaining a dent caused by forging of a second shot; FIG. 5A shows a state before starting forging of a second shot; FIG. It is a figure showing the state of.

FIG. 5 shows a case where the rotation angle around the axis of the material is 90 degrees.
5A is a top half cross-sectional view for explaining a dent caused by forging of a second shot; FIG. 5A shows a state before starting forging of a second shot; FIG. It is a figure showing the state of.

FIG. 6 shows the relationship between the rotation angle around the axis of the material between the first shot and the second shot and the depth of the dent after the completion of the forging in the second shot in the case of finish molding using a round groove mold. It is a figure showing a relation.

[Explanation of symbols]

 1: round groove anvil, 1a: groove bottom, 1b: relief, 1c: chamfer, 1f: perch surface, 2: V groove anvil, 2a: groove bottom, 2b: relief, 2c: chamfer, 2d: slope Part, 2f: perch surface, 3: material, 3a: biting part, 3b: biting part, 3c: dent, 3d: base.

Claims (1)

[Claims] When a pair of round groove anvils or V-groove anvils that open and close are opened, a material having a polygonal or circular cross-section is fed in the axial direction and rotated about its axis to rotate. Alternatively, in a hot forging method in which forging is performed a plurality of times to reduce the material at the time of closing operation of the V-groove anvil and forging into a steel slab having a circular or polygonal cross section, the shaft of the material at each opening operation of the anvil is provided. A hot forging method for a steel slab, wherein a rotation angle around a center is more than 45 degrees and 75 degrees or less.