JP3780839B2 - Hot forging method for billets - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for hot forging a steel slab that is made of carbon steel, alloy steel, stainless steel or high alloy and has a cross-sectional shape of a polygon or a circle and is forged into a circular or polygonal steel slab. .
[0002]
[Prior art]
Usually, the following three methods are used to produce round steel pieces by hot forging.
[0003]
The first method is a method of rough forming using a flat metal mat. That is, the opposing surface of a rectangular or rectangular material (steel ingot, bloom, etc.) having a small cross-sectional shape is alternately squeezed using a pair of flat metal lays and has a small size. Mold into an intermediate material. Next, in the same manner as described above, the cross-sectional shape is substantially a regular hexagonal shape or more through a process of forming the cross-sectional shape into a substantially regular octagon by alternately reducing the corner portions of the intermediate material using a pair of flat metal mats. Roughly molded into a polygonal round material. Thereafter, a pair of anvils (hereinafter referred to as “circular groove anvil”) in which round grooves are formed is finished by spiral forging into round steel pieces having a predetermined outer diameter and a circular cross section.
[0004]
The second method is a method of rough forming using an anvil having a V-groove (hereinafter referred to as a V-groove anvil). Specifically, the cross-sectional shape is approximately a regular hexagon or more using a pair of V-groove anvils with respect to the intermediate material formed into a substantially square or regular octagonal cross-section in the first method. After the rough forging of the polygonal round material is spirally forged, as in the above, it is finish-formed by spiral forging into a round steel piece having a predetermined outer diameter using a round groove anvil.
[0005]
In the third method, a round slab having a circular cross-sectional shape manufactured by continuous casting is used as a raw material, and a pair of V-groove or flat anvils is used as the raw material. After applying spiral forging to coarsely round more polygonal round material, as above, finish forming by round forging into round steel pieces with a predetermined outer diameter using round groove anvil To do.
[0006]
In the above method, spiral forging means that when a pair of anvils that open and close is opened, the material is fed in the axial direction and rotated by a predetermined angle around the axis to close the anvil. It is a forging method in which forging is sometimes performed a plurality of times to reduce the material. In the following description, each forging in the above multiple forgings is called a shot.
[0007]
In the hot forging method that undergoes the above-described steps, the round groove anvil as described below is used for finish forming, regardless of which of the first to third methods is employed.
[0008]
1A and 1B are diagrams showing an example of a commonly used round groove anvil, in which FIG. 1A is a plan view, FIG. 1B is a cross-sectional view taken along the line II in FIG. 1A, and FIG. ) Is a cross-sectional view taken along the line of FIG.
[0009]
As shown in the figure, the round groove anvil 1 includes a groove bottom portion 1a having a radius of curvature Rg and a width H formed so as to have a depth D at the center of the groove bottom, and a groove bottom portion 1a. It is a semi-circular hole type consisting of a relief portion 1b formed with a radius of curvature Rc on both sides, and has round grooves with a constant depth D except for both ends in the longitudinal direction of the anvil. Further, chamfered portions 1c having a radius of curvature Rb are formed at both ends in the longitudinal direction of the anvil, and perch surfaces 1f are formed at both sides in the width direction. And the hot finish outer diameter of the round steel piece to be obtained is set by adjusting the offset amount G.
[0010]
In addition, a V-groove anvil as described below is used for rough forming by spiral forging in the second and third methods.
[0011]
2A and 2B are diagrams showing an example of a commonly used V-groove anvil, in which FIG. 2A is a plan view, FIG. 2B is a cross-sectional view taken along the line II in FIG. ) Is a cross-sectional view taken along the arrow line in FIG.
[0012]
As shown in the figure, the V-groove anvil 2 is formed on the groove bottom 2a having a radius of curvature Rg formed with an offset amount G so that the depth at the center of the groove is D, and on both sides of the groove bottom 2a. The V-shaped hole shape is composed of the inclined portion 2d having the apex angle α and the relief portion 2b having the radius of curvature Rc formed on both sides of the inclined portion, and the depth D is excluding both ends in the longitudinal direction of the anvil. It has a constant V groove. Further, chamfered portions 2c having a radius of curvature Rb are formed at both ends in the longitudinal direction of the anvil, and perch surfaces 2f are formed at both sides in the width direction. The diagonal distance of the polygonal round material to be obtained is set by adjusting the offset amount G.
[0013]
FIG. 3 is a diagram for explaining a method of finish forming by spiral forging using a round groove anvil. FIG. 3 (a) is a cross-sectional view showing a state after forging of the first shot, and FIG. Sectional drawing which shows the state before the forging start of the 2nd shot, The same figure (c) is sectional drawing which shows the state after the forging of the 2nd shot.
[0014]
In FIG. 2A, the round groove anvil 1 having the shape shown in FIG. 1 is used. The circular groove anvil 1 is disposed in a pair facing a press (not shown) and opens and closes by driving the press. For example, the material 3 having a substantially regular hexagonal cross-sectional shape is subjected to the forging of the first shot 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 portion 1a of the round groove anvil 1 and a part of the material 3 is bitten between the escape portions 1b of the round groove anvil 1 to generate the biting portion 3a.
[0015]
When the forging of the first shot is completed and the round groove anvil 1 is opened, the conveyance unit (not shown) feeds the material 3 in the axial direction by a predetermined amount, and rotates the material 3 around its axis, for example, a rotation angle θ = 40 degrees. And the biting portion 3a of the material 3 is rotated to the groove bottom portion 1a side of the round groove anvil 1 as shown in FIG.
[0016]
Thereafter, forging of the second shot is performed by the closing operation of the round groove anvil 1. In the second shot forging, the biting portion 3a generated by the first shot forging is squeezed by the groove bottom portion 1a, so that the biting portion 3a flows along the groove bottom portion 1a and disappears. At this time, in the vicinity of the portion where the biting portion 3a is formed, a recess 3c is generated and a new biting portion 3b is generated. This state is shown in FIG.
[0017]
Thus, the dent 3c generated by the forging of the second shot remains until the end of the subsequent spiral forging, and there is a problem that the roundness of the round steel piece that has been finish-formed is deteriorated. In particular, during rough forming, which is the previous process, if the cross-sectional dimension of the rough round material becomes larger than a predetermined dimension due to wear of flat metal or V-groove metal and changes in the friction coefficient, The generated biting portion 3a becomes large, and the dent 3c generated in the second shot also becomes large, and the roundness after forging becomes worse.
[0018]
In order to avoid the occurrence of the large biting portion 3a described above, the underfill state, that is, the reduction allowance in the finish molding is slightly reduced in anticipation of the dimensional variation of the rough round material, so that the material is completely with respect to the groove bottom portion 1a. When forging is performed without filling, the round steel slab after finish forming has a locally flat surface in the circumferential direction and the axial length direction, and a round steel slab with satisfactory roundness cannot be obtained. There was a problem. This problem becomes particularly prominent when forging ferritic stainless steel, duplex stainless steel, and the like, which have a large amount of spread during rolling.
In addition, the above problem is caused by spiral forging, in which a material having a polygonal or circular cross-sectional shape is roughly formed into a rough round material having a cross-sectional shape of approximately a regular hexagon or more using a V-groove anvil. Also occurs.
[0019]
In addition to the spiral forging method using the round groove anvil 1 shown in FIG. 1 or the V groove anvil shown in FIG. 2, a spiral forging method using an anvil with a groove is disclosed in Japanese Patent Laid-Open No. 6-71377 and This is disclosed in Japanese Utility Model Publication No. 11-57924.
[0020]
The forging method disclosed in Japanese Patent Laid-Open No. 6-71377 uses an anvil with a tapered round groove in which the diameter of the groove continuously decreases from the entry side to the exit side, with a rotation angle of 45 degrees / shot. This is a forging method in which a material having a square cross-sectional shape is directly finish-formed into a round steel piece having a circular cross-sectional shape by spiral forging.
[0021]
In addition, the forging method disclosed in Japanese Patent Application Laid-Open No. 11-57924 is changed from an introduction portion constituted by a V groove on the inlet side, a finish portion constituted by a round groove on the outlet side, and a V groove to a round groove in the middle. This is a forging method in which finish forming is performed by spiral forging at a rotation angle of 45 degrees / shot, using an anvil formed with a connecting portion constituted by a groove having a shape to be formed.
[0022]
However, in any of these forging methods, an offset amount G (see FIG. 1B) is set in the anvil at the time of forging, so there is a gap between the pair of anvils, It is inevitable that a biting portion will occur due to the forging of the first shot. In addition, after the material is rotated 45 degrees around its axis, forging for the second shot is performed, generation of a large dent cannot be prevented.
[0023]
[Problems to be solved by the invention]
The subject of this invention is providing the hot forging method of the steel piece which can make the depth of the dent which arises locally in any case of rough shaping | molding and finishing shaping | molding as much as possible.
[0024]
[Means for Solving the Problems]
Gist of the present invention, the material of the cross-sectional shape when the opening operation is polygonal or circular pair of gold insole which opened and closed by rotating its axis around with feed in the axial direction, during closing operation of the front Kikin insole In the hot forging method in which forging to reduce the material is performed a plurality of times and forging into a steel piece having a circular or polygonal cross-sectional shape , rough forming is performed using a flat metal or V-groove metal, and then rounding in finish molding It is a hot forging method of a steel slab characterized in that the rotation angle around the axis of the material at the time of each opening operation using a grooved metal is not less than 50 degrees and not more than 75 degrees.
[0025]
In the present invention, the time of opening operation means the time when the anvil that opens and closes is not in contact with the material.
[0026]
The inventors of the present invention at the time of opening operation of the anvil when a material having a substantially regular hexagonal cross-sectional shape is finish-formed into a round steel piece having a circular cross section by spiral forging using a round groove anvil. The following knowledge was obtained by investigating the influence of the rotation angle around the axis of the material. The present invention is based on this finding.
[0027]
1) When spirally forging a material, the biting portion that occurs when the material is first forged on the entry side of the round groove anvil is the largest, and this biting occurs when the biting portion is reduced by the next forging. A local dent occurs in the vicinity of the part.
[0028]
2) This dent greatly affects the roundness of the round steel slab that remains until the end of spiral forging.
[0029]
3) Although this dent occurs regardless of the rotation angle of the material, the depth of the dent varies depending on the rotation angle around the axis of the material, and the rotation angle is greater than 45 degrees and less than 75 degrees. Is small.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the hot forging method of the steel piece concerning this invention is demonstrated in detail based on drawing.
[0031]
The hot forging method of the present invention is a hot forging method premised on a method of finish forming by spiral forging using a round groove anvil as described with reference to FIG.
[0032]
That is, as shown in FIG. 5 (a), a pair of round groove anvils 1 disposed opposite to a press (not shown) and opened / closed by driving the press make the material 3 having a substantially regular hexagonal cross section. The first shot is forged.
[0033]
When the forging of the first shot is completed and the round groove anvil 1 is opened, as shown in FIG. 5B, the conveyance unit (not shown) feeds the material 3 in the axial direction by a predetermined amount and feeds the material 3 to its axis. The second shot is forged as shown in FIG. 4C by rotating around the center by the rotation angle θ. By repeating the above forging a plurality of times, a material having a substantially regular hexagonal cross-sectional shape is finish-formed into a round steel piece.
[0034]
As described above, the dent 3c is generated during the forging of the second shot as described above. The reason will be described with reference to FIGS.
[0035]
FIG. 4 is an upper half sectional view for explaining a dent generated by forging the second shot when the rotation angle around the axis of the material is 40 degrees, and FIG. The figure which shows the state of this, The figure (b) is a figure which shows the state after the forge of the 2nd shot. FIG. 5 is an upper half sectional view for explaining a dent generated by forging the second shot when the rotation angle around the axis of the material is 90 degrees. FIG. 5A shows the forging of the second shot. The figure which shows the state before a start and the figure (b) are figures which show the state after the forge of the 2nd shot.
[0036]
As shown in FIG. 4, when the rotation angle around the axis of the material 3 is as small as about 40 degrees, the biting portion 3 a shown in FIG. 4 (a) flows in the direction of the relief portion 1 b by forging the second shot. As a result, a recess 3c as shown in FIG. 5B is formed at the base 3d of the bite 3a on the groove bottom 1a side.
[0037]
On the other hand, as shown in FIG. 5, when the rotation angle around the axis of the material 3 is as large as 90 degrees, the biting portion 3a shown in FIG. 5A is pushed into the material 3 by forging the second shot. As a result, recesses 3c and 3c as shown in FIG. 5B are generated at the bases 3d and 3d on both sides of the biting portion 3a.
[0038]
Thus, when the rotation angle around the axis of the material 3 is 40 degrees, the base 3d on the groove bottom portion 1a side of the biting portion 3a, and when the rotation angle is 90 degrees, both sides of the biting portion 3a are provided. A recess 3c is formed at the bases 3d and 3d. Even when the rotation angle around the axis of the material is more than 40 degrees and less than 90 degrees, the dent 3c is generated at one root 3d of the biting portion 3a or the roots 3d, 3d on both sides.
[0039]
FIG. 6 shows the rotation angle around the axis of the material 3 between the first and second shots and the depth of the dent after completion of the second shot forging in the case of finish forming using a round groove anvil . It is a figure which shows a relationship. As shown in the figure, the depth of the dent is the largest when the rotation angle is 30 degrees to 45 degrees. However, when the rotation angle exceeds 45 degrees, the depth of the dent rapidly decreases, and when the rotation angle is 50 degrees, the depth of the dent becomes the smallest. When the rotation angle is larger than 50 degrees, the depth of the dent becomes slightly larger but is almost stable, and when it exceeds 75 degrees, the depth of the dent increases again.
[0040]
Thus, the depth of the dent is influenced by the rotation angle around the axis of the material 3, and the depth of the dent can be reduced if the rotation angle of the material is set to 50 degrees or more and 75 degrees or less. Accordingly, the forging method of the present invention, the rotation angle around the axis of the material 3 and 50 degrees, Ru needs to be 75 degrees or less.
[0041]
The material 3 from which the biting portion generated by the forging of the first shot has disappeared due to the forging of the second shot has a small recess 3c shown in FIG. 3C and a biting portion 3b of the forging of the second shot. Arise. The material 3 is fed in a predetermined amount in the axial direction in the same manner as described above, and is rotated more than 45 degrees and less than 75 degrees around the axis, and then forging for 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 generated by the forging of the third shot is also small.
[0042]
In this way, the material 3 is continuously spirally forged and finish-formed into round steel pieces having a substantially round cross-sectional shape.
[0044]
【Example】
Made of SUS316, with a steel ingot with a length of about 2000 mm and an average dimension of 490 mm on one side and a rectangular cross section, the material is forged into round steel pieces with an outer diameter of 178 mm by heating to 1290 ° C. In this case, a flat metal was used to roughly form a rough round bar having a cross-sectional dimension of 184 mm and a hexagonal cross section, and a round grooved metal was used to finish to round steel pieces.
[0045]
The round groove anvil has the shape shown in FIG. 1 which is used for hot finish diameters of 172 to 184 mm, G = 11 mm, D = 81 mm, Rg = 92 mm, H = 159.3 mm, Rc = 70 mm, Rb = 40 mm, and the total length is 300 mm. The distance between the perch surfaces 1f during the reduction was set to 19.5 mm. The finish forming was spiral forging under the condition of a feeding amount of 23 mm / shot, and finish forming into a round steel piece having a hot finish outer diameter of 181.5 mm and a length of 15000 mm.
[0046]
In the above finish forming, the rotation angle in spiral forging is set to 50 degrees / shot and 75 degrees / shot as an example of the present invention, and in the comparative example, the rotation angle is set to 45 degrees / shot and 80 degrees / shot. Finished into round steel pieces. After these round steel pieces were allowed to cool to room temperature, the outer diameter was measured at a pitch of 30 degrees in the circumferential direction at positions spaced 4000 mm from the center and end portions in the longitudinal direction of the round steel pieces. Circularity was measured. Moreover, the full length of each round steel piece was observed visually, and the amount of dents at the most marked 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.
[0047]
As a result, in the present invention example with a rotation angle of 50 degrees / shot, the present invention example with a roundness of 2.0 to 0.6 mm, a dent depth of 1.0 to 0.3 mm, and a rotation angle of 75 degrees / shot. Then, 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, in the comparative example in which the roundness is 4.1 to 3.0 mm, the depth of the recess is 2.1 to 1.5 mm, and the rotation angle is 80 degrees / shot. The roundness was 3.6 to 2.8 mm, and the depth of the recess was 1.8 to 1.4 mm. As described above, the inventive example is superior in roundness compared to the comparative example, and the depth of the recess is small.
[0048]
【The invention's effect】
According to hot forging method of the present invention, it is possible to produce a small slab depths of the recess, producing a good round steel piece roundness by adopting the Finish shaping of round steel piece be able to.
[Brief description of the drawings]
1A and 1B are diagrams showing an example of a commonly used round groove anvil, in which FIG. 1A is a plan view, FIG. 1B is a cross-sectional view taken along line II in FIG. 1A, and FIG. ) Is a cross-sectional view taken along the line of FIG.
FIGS. 2A and 2B are diagrams showing an example of a commonly used V-groove anvil, in which FIG. 2A is a plan view, FIG. 2B is a cross-sectional view taken along the line II in FIG. ) Is a cross-sectional view taken along the line of FIG.
FIG. 3 is a view for explaining a method of finish forming by spiral forging using a round groove anvil. FIG. 3 (a) is a cross-sectional view showing a state after forging of the first shot, and FIG. Sectional drawing which shows the state before the forging start of the 2nd shot, The same figure (c) is sectional drawing which shows the state after the forging of the 2nd shot.
FIG. 4 is an upper half sectional view for explaining a dent generated by forging the second shot when the rotation angle around the axis of the material is 40 degrees, and FIG. The figure which shows the state of this, The figure (b) is a figure which shows the state after the forge of the 2nd shot.
FIG. 5 is an upper half sectional view for explaining a dent generated by forging the second shot when the rotation angle around the axis of the material is 90 degrees, and FIG. The figure which shows the state of this, The figure (b) is a figure which shows the state after the forge of the 2nd shot.
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 completion of the forging of the second shot when performing finish forming using a round groove anvil . FIG.
[Explanation of symbols]
1: Round groove anvil,
1a: groove bottom,
1b: escape part,
1c: chamfered portion,
1f: Perch surface,
2: V groove anvil,
2a: groove bottom,
2b: escape part,
2c: chamfered part,
2d: inclined part,
2f: Perch surface
3: Material,
3a: biting part,
3b: biting part,
3c: dent,
3d: Root.

Claims (1)

Sectional shape when the opening operation of a pair of gold insole for opening and closing rotates on its axis around with feeding a polygonal or circular material in the axial direction, for rolling the material during the closing operation of the front Kikin insole forging In a hot forging method in which the cross-sectional shape is forged into a round or polygonal steel slab,
After rough forming using flat anvil or V-groove anvil, the rotation angle around the axis of the material at the time of each opening operation using round groove anvil in finish forming is set to 50 degrees or more and 75 degrees or less A hot forging method for steel slabs.

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