JP3757800B2 - Anvil for free forging and hot forging method using this anvil - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an anvil for free forging, more specifically, an anvil used for free forging by pressing a work material such as carbon steel, alloy steel, stainless steel and high alloy multiple times hot. The present invention relates to a hot free forging method using an anvil.
[0002]
[Prior art]
When forging steel ingots, slabs or ingots by free hot forging, the workpieces are generally opposed by a pair of flat anvils arranged at opposite positions while feeding the workpiece. The two surfaces are sequentially reduced. Then, when the entire length is reduced, the workpiece is rotated by 90 ° around the axis, for example, around the conveying direction, and the two different surfaces are sequentially reduced by a pair of opposing flat anvils while feeding the workpiece again Repeat several times.
[0003]
Here, the flat anvil used for the above free forging has a width larger than the width of the work material, and the surface that mainly squeezes the work material is flattened, and the work material of this flattened surface A tapered surface or a circular arc surface having a predetermined angle of inclination is formed at the front and rear ends in the transport direction.
[0004]
When forging using a flat metal having a flat surface, the surface layer of the workpiece that contacts the flat surface of the flat metal is restrained in plastic flow due to friction with the flat metal, during forging. In the center of the contact area with the flat metal lay, a dead metal region where almost no plastic strain is applied is generated.
[0005]
In general, when hot working is performed on a steel ingot, slab or ingot, the structure is refined by applying plastic strain, and the mechanical properties are improved. However, if the structure of the workpiece is not refined in the initial process of free forging and a rough structure of the steel ingot, slab or ingot remains, large strain and stress are generated in the subsequent process of free forging. When loaded, cracks greatly develop along coarse crystal grains having low ductility, and defects such as forging cracks are generated.
[0006]
Therefore, when free forging is performed using the above-described conventional flat metal laying, the structure is not refined in the region where the plastic strain in the initial process hardly occurs. There is a possibility that a coarse structure with inferior properties is mixed. As a result, in order to prevent the occurrence of defects in the area where the rough structure remains, in the subsequent process of free forging, the reduction amount and feed amount of the work material are reduced, or the work material is removed during forging. Production efficiency had to be reduced, such as by reheating.
[0007]
In the hot free forging process using such a flat anvil, for example, in Japanese Patent Application Laid-Open No. 7-116766, a corner surface inclined at a predetermined angle from both ends of a flat surface to the front and rear in the material conveying direction is formed into a taper surface inclined in multiple steps It has been proposed to form a taper surface and an arc surface, and to make it difficult to break even difficult-to-process materials by loosening the inclination.
[0008]
[Problems to be solved by the invention]
However, even if a flat metal mat proposed in Japanese Patent Laid-Open No. 7-116766 is used during hot free forging, since the flat metal mat still has a flat surface, the mechanical properties due to the dead metal region are inferior and rough. Needless to say, there is a possibility that organizations may coexist.
[0009]
The present invention has been made in view of the above-described problems, and in hot free forging, in particular, forging to reduce a flat surface of a material having a polygonal cross-sectional shape typified by a rectangle, a work material It is an object to provide an anvil shape that can apply uniform strain to the surface layer of the metal and prevent the occurrence of defects such as cracks by not causing a dead metal region, and a forging method using the anvil. .
[0010]
[Means for Solving the Problems]
In order to achieve the above-described object, the anvil for free forging according to the present invention has a height that satisfies the condition defined by the following formula 2 on the processed surface, where b is the width of the workpiece before forging. The ridges of h are formed so as to extend in the same direction in a plurality of strips at a pitch w that satisfies the condition defined in the following Equation 1. And by doing in this way, in free forging, it becomes possible to give a uniform distortion to the surface layer of a work material.
[0011]
[Expression 1]
(1/35) b ≦ w ≦ (1/5) b
[0012]
[Expression 2]
(1/8) w ≦ h ≦ (1/2) w
[0013]
The hot free forging method according to the present invention is a method for forging a workpiece having an n-square cross-sectional shape in a plurality of steps. Forging is performed so that the crossing angle of the ridges of the ridges is 40 to 140 ° with respect to the same surface of the workpiece, and the last n / 2 times or more are forged using a flat anvil. I am going to do that. And by doing in this way, the area which a workpiece and an anvil contact simultaneously can be reliably made small.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
As a result of investigating the shape of an anvil where the dead metal area does not occur on the surface layer of the workpiece that contacts the anvil using numerical analysis as a basic study, the inventors shifted the time for the workpiece to start contacting the anvil. It has been found that the generation of the dead metal region can be suppressed by reducing the area where the work piece and the anvil simultaneously contact each other, that is, by making the processed surface of the anvil uneven.
[0015]
Based on this knowledge, the present inventors further developed a concavo-convex shape formed on the processing surface of the anvil for uniformly distributing plastic strain on the surface layer of the workpiece, and a forging method using the anvil made of stainless steel. We examined by free forging.
[0016]
As a result, it is effective to form a crest composed of a ridge line having a predetermined angle θ with respect to the center line on the processing surface of the anvil. Rotating a predetermined angle around the axis and performing the reduction after the next process, the ridgeline of the processing surface of the other anvil arranged opposite to the other anvil is processed in the previous process When the angle of intersection with the ridgeline formed on the material is 40 to 140 °, the overlapping of both ridgelines can be prevented, and the area in contact with each other can be surely reduced, and the covering process occurs in the subsequent process. It turned out to be difficult.
[0017]
The present invention has been made on the basis of the knowledge obtained as a result of the examination and analysis by the inventors described above. When the width of the workpiece before forging is b, For free forging with the gist of forming a ridge having a height h satisfying the conditions specified in 2 to extend in the same direction in a plurality of strips at a pitch w satisfying the conditions specified in the above-mentioned formula 1. It is an anvil.
[0018]
In the anvil for free forging according to the present invention, the pitch w of the ridges is in the range of 1/35 to 1/5 of the width b of the workpiece before forging. This is because if the width is larger than 1/5 of the width b, the contact area increases almost simultaneously and a dead metal region is generated on the surface layer. Moreover, if it is smaller than 1/35 of the width b of the workpiece before forging, a dead metal region is generated as in the case where the valley is not filled with the material and the flat surface is pressed.
[0019]
That is, when the pitch w of the ridge is outside the range of 1/35 to 1/5 of the width b of the workpiece before forging, a rough structure remains in the workpiece, forging cracks, etc. This is because there is a risk of the occurrence of defects.
[0020]
In addition, in the anvil for free forging according to the present invention, the height h of the ridges is set to 1/8 or more of the pitch w. There is a risk that a rough structure will remain directly under the surface layer and defects such as forging cracks may occur, and the anvil will be smoothed early due to wear and plastic deformation due to changes over time, resulting in the effect of surface refinement This is because it will disappear completely.
[0021]
According to various experiments conducted by the present inventors , the upper limit of the height h of the mountain portion is larger than 1/2 of the pitch w. since there is a possibility of generating scratches Komure the workpiece, the height h of the crest portion you 1/2 or less of the pitch w. The peak r may be 0, but it is preferably 1/10 or more of the pitch w in order to make it difficult for the cover to be covered during rolling.
[0022]
The hot free forging method according to the present invention is a method for forging a workpiece having an n-square cross-sectional shape in a plurality of steps. Forging is performed so that the crossing angle of the ridges of the ridges is 40 to 140 ° with respect to the same surface of the workpiece, and the last n / 2 times or more are forged using a flat anvil. Is.
[0023]
In the hot free forging method according to the present invention, forging is performed by using the anvil for free forging according to the present invention so that the crossing angle of the ridge lines of the ridges is 40 to 140 ° with respect to the same surface of the workpiece. This is because, even if the angle is smaller than 40 ° or larger than 140 °, the end of the intersection becomes an acute angle, and the work material is covered with flaws in the forging by the flat metal laying in the subsequent stage.
[0024]
【Example】
Hereinafter, the present invention will be described based on the embodiments shown in FIGS.
1A and 1B are schematic views showing an example of an anvil according to the present invention, wherein FIG. 1A is a plan view shown with a workpiece, FIG. 1B is a cross-sectional view taken along line AA in FIG. FIGS. 3A to 3D are cross-sectional shrinkage steps when forging a rectangular workpiece. FIGS. It is the figure which showed the first 4 processes of from the front (back) side of the conveyance direction.
[0025]
1 is an anvil according to the present invention, and a rough structure represented by columnar crystals existing in a workpiece 2 such as a steel ingot or ingot produced by a normal method is made into a fine structure by hot free forging. It is used when doing.
[0026]
As shown in FIG. 1, the processed surface of the anvil 1 according to the present invention includes a peak portion 1 a composed of a pitch w, a height h, and a ridge line having an angle θ with respect to the center line. For example, the pitch w of the peak 1a is, for example, 1/20 of the width b of the workpiece 2 before forging, and the height h of the peak 1a is, for example, 1/3 of the pitch w. To do. Further, r of the peak portion 1a is, for example, 1/10 of the pitch w.
[0027]
In the anvil 1 according to the present invention, the angle θ with respect to the center line does not need to be specified in particular. However, as shown in FIG. Free forging while feeding parallel to the center line of the anvil 1 and when moving from one process to the next, as shown in (a) to (d) of FIG. When the material 2 is rotated 90 degrees, for example, and the same surface is repeatedly squeezed twice or more, the ridgeline of the processing surface of the other anvil 1 arranged opposite to the other anvil 1 arranged opposite to the front The angle of the two anvils 1 to be opposed to each other is adjusted so that the intersection angle with the ridge line formed on the workpiece 2 in the process is 40 to 140 °.
[0028]
As described above, forging is performed while feeding the workpiece 2 parallel to the center line of the anvil 1, and when moving from one process to the next, the workpiece 2 is 90 ° around the feed direction. Conventionally, when a workpiece 2 having a flat surface with a polygonal cross-sectional shape typified by a rectangle is freely forged, the processing surface is flat in all steps from the beginning to the end of forging. It was done using a flat anvil.
[0029]
On the other hand, in the present invention, when forging the workpiece 2 having an n-square cross-sectional shape, the first n times or more steps are performed using the anvil 1 for free forging according to the present invention having the above-described configuration. Forging is performed so that the crossing angle of the ridge line of the peak portion 1a of the anvil 1 is, for example, 90 ° with respect to the same surface of the workpiece 2, and the last n / 2 or more steps are performed using a conventional flat anvil. . The intermediate step may be performed using any anvil.
[0030]
When the anvil 1 of the present invention is used, when each surface (surfaces A to D in FIG. 3) of the workpiece 2 is squeezed at least once by the respective anvil 1 in the initial stage of forging, the entire surface of the surface portion of the workpiece 2 is covered. The plastic strain can be uniformly distributed and the structure can be made finer. This makes it possible to perform forging in the subsequent process without reducing defects such as forging cracks without reducing the feed amount of the workpiece 2.
[0031]
Hereinafter, description will be given of the results of experiments performed to confirm the effects of the present invention described above.
Example 1
Using a SUS316 steel ingot with a rectangular cross section of 2000 mm in length and 500 mm in width b as a raw material, and heating this material to 1200 ° C, changing the rolling direction by 90 ° for each process, a square billet with a side of 210 mm in 8 processes Molded into. At this time, the feed amount of the workpiece in the same forging process was 120 mm.
[0032]
The method of the present invention using a flat anvil with a flat working surface in all steps and the method using a flat anvil with a plurality of ridges extending in the same direction in the first four steps and then using the flat anvil in the remaining four steps Thus, manufacturing comparison was performed by changing the pitch w and height h of the ridges. The centerline direction (workpiece feed direction) length of the anvil processing surface was 120 mm, and r at the peak was 1/3 of the pitch w. The results are shown in Table 1.
[0033]
[Table 1]
[0034]
As is clear from Table 1 above, the billet produced by the method of the present invention using the anvil of the present invention showed no cracking or covering wrinkles under any conditions. The structure was observed to confirm that the entire square billet was refined. On the other hand, in the conventional method using a flat anvil with a flat processed surface in all steps and the comparative example using an anvil where the ridges formed on the processed surface deviate from the scope of the present invention, both cracks and covering wrinkles occur. Occurred.
[0035]
(Example 2)
Using a SUS316 steel ingot with a rectangular cross section of 2000 mm in length and 500 mm in width b as a raw material, and heating this material to 1200 ° C, changing the rolling direction by 90 ° for each process, a square billet with a side of 210 mm in 8 processes Molded into. At this time, the feed amount of the workpiece in the same forging process was 120 mm.
[0036]
The crossover angle was changed using an anvil having a plurality of ridges extending in the same direction in the first four steps, and production comparison was performed by a method using a flat anvil in the remaining four steps. The centerline direction (workpiece conveyance direction) length of the processed surface of the anvil was 120 mm, and the r of the peak portion was 1/3 of the pitch w. The results are shown in Table 2.
[0037]
[Table 2]
[0038]
As apparent from Table 2 above, the square billet produced in the range of 40 to 140 °, which is an embodiment of the method of the present invention using the anvil of the present invention, shows no cracks and no wrinkles at all. It was. As a result of observing the structure, it was confirmed that the entire square billet was a refined structure. On the other hand, in the comparative example of the method of the present invention in which the anvil of the present invention was used but the crossing angle was out of the range of 40 to 140 °, cracks were not seen, but covering wrinkles occurred.
[0039]
【The invention's effect】
As described above, by adopting the method of the present invention using the anvil of the present invention, free forging can be performed at a high production efficiency without causing forging cracks and cracks even in difficult-to-work materials.
[Brief description of the drawings]
1A and 1B are schematic views showing an example of an anvil according to the present invention, in which FIG. 1A is a plan view together with a workpiece, and FIG. 1B is a cross-sectional view taken along line AA in FIG.
FIGS. 2A and 2B are views of two anvils according to the present invention arranged to face each other as viewed from the processing surface side.
FIGS. 3A to 3D are views showing the first four steps of the cross-section shrinking step when forging a rectangular workpiece from the front (back) side in the conveying direction.
[Explanation of symbols]
1 Anvil 1a Yamabe 2 Work material

Claims (2)

When the width of the workpiece before forging is b, the height h that satisfies the conditions specified in the following formula (2) on the processed surface satisfies the conditions specified in the following formula (1). An anvil for free forging characterized by being formed to extend in the same direction with a plurality of strips at a pitch w.
(1/35) b ≦ w ≦ (1/5) b (1)
(1/8) w ≦ h ≦ (1/2) w (2) When forging a workpiece having an n-gonal cross-sectional shape in a plurality of steps, the first n steps or more steps are ridges with respect to the same surface of the workpiece using the free forging anvil according to claim 1. A hot free forging method characterized in that forging is performed so that the ridge line crossing angle is 40 to 140 °, and the last n / 2 or more steps are forged using a flat metal laying.