JP2010089097A - Method of forging workpiece - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forging a workpiece for easily closing (pressure-bonding) of internal defects of the workpiece. <P>SOLUTION: In the forging method for executing forging while the workpiece 2 is screwed down by an anvil 1 to close internal defects 8 of the workpiece 2, the relationship between the internal defect evaluation index Q and the draft is obtained correspondingly the workpiece 2 to be forged. The position, the size and the shape of the internal defects 8 before the forging are estimated. On the basis of the estimated position, the estimated size and the estimated shape of the defect, the minimum value Qmin for closing the internal defects 8 in the internal defect evaluation index Q is obtained, and the workpiece 2 is screwed down by the anvil 1 with the value equal to or more than the draft corresponding to the minimum value Qmin. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for forging a workpiece by forging the workpiece by reducing the workpiece.

Conventionally, a forging method for forging a workpiece by rolling the workpiece such as a metal-based material with an anvil is disclosed (for example, Patent Document 1).
In the hot forging method of Patent Document 1, an anvil having a width 0.4 to 0.7 times the material width and an axial length 0.3 to 0.5 times the material height is used. Forging is performed while cooling the surface layer of the preheated metal material. In the technique of this patent document 1, while rolling down using the wide anvil according to the shape, the surface layer of material is cooled, the transmission of the rolling load to the inside is promoted, and internal defects are closed (crimping) )It is carried out.

Now, in the rolling field in which a slab (workpiece) cast by continuous casting or the like is rolled, a number of methods have been developed to eliminate voids in the slab after rolling, that is, internal defects (for example, patents). Literature 2, Patent Literature 3).
In the rolling method of Patent Document 2, a gap compression parameter (evaluation parameter) Gm by rolling is defined, and a rolling pass schedule is determined based on the defined Gm value, thereby preventing internal defects in the slab. ing. That is, in Patent Document 2, rolling is performed according to a rolling pass schedule so that the cumulative value ΣGm + i is 0.25 or more.

Moreover, in the rolling method of patent document 3, the pass schedule is determined and rolled so as to include one or more passes satisfying the gap compression parameter Gm ≧ 0.20.
JP-A-6-277783 JP 2005-74487 A JP 2002-346604 A

As described above, in the technique of Patent Document 1, the internal defect of the workpiece is closed by changing the shape of the anvil, but because a wide anvil is used according to the shape of the workpiece, Each time the shape of the workpiece changes, the anvil must also correspond to the shape, and forging is very time-consuming and is not practical.
As shown in Patent Document 2 and Patent Document 3, the gap compression parameter Gm is defined, and the internal schedule is eliminated by determining the pass schedule using this Gm value. In reality, however, rolling techniques cannot be applied to forging due to differences in processing methods.

  Then, an object of this invention is to provide the forging method of the workpiece which can perform the closing (crimping) of the internal defect of a workpiece easily.

In order to achieve the above object, the present invention has taken the following measures.
That is, in the forging method in which the means of the present invention performs forging while reducing the internal defect of the work piece by reducing the work piece with an anvil, the equation (1) corresponds to the work piece to be forged. In addition to obtaining the relationship between the internal defect evaluation index and the reduction ratio, the defect position, the defect size and the defect shape of the internal defect before forging are estimated, and based on the estimated defect position, the defect size and the defect shape, The minimum value of the internal defect evaluation index necessary for closing the internal defects is obtained, and the work material is pressed down with an anvil at a rolling rate corresponding to the minimum value or more.

  It is preferable to obtain the minimum value of the internal defect evaluation index from the formula (2).

  In obtaining the first coefficient (A) and the second coefficient (B) of Expression (2), it is preferable to use Expression (3) to Expression (8).

  When estimating the defect position of the internal defect, the defect size and the defect shape of the internal defect, it is preferable to use flow solidification analysis and to use deformation analysis when obtaining the internal defect evaluation index.

  According to the present invention, it is possible to easily close (crimp) internal defects of a workpiece.

A method for forging a workpiece according to the present invention will be described.
FIG. 1 shows the structure of an anvil that performs the method for forging a workpiece of the present invention.
As shown in FIG. 1, the anvil 1 is forging a workpiece 2 such as a billet, a bloom, an ingot, etc., and an anvil main body 3 that can be moved up and down to reduce the workpiece 2, and this A mounting table 4 is provided below the anvil main body 3 so as to be fixed so as not to move up and down.
The anvil body 3 includes a restraining portion 5 that restrains the movement of the surface of the workpiece 2 when the anvil body 3 is being reduced. Specifically, a restraining portion 5 is provided on the surface 6 (sometimes referred to as an opposing surface) of the anvil main body 3 facing the workpiece 2, and the restraining portion 5 is formed by a plurality of concave and convex portions 7 formed in an arc shape. It is configured.

  In such an anvil 1, after placing the workpiece 2 on the flat mounting table 4, the anvil main body 3 is lowered and the surface of the workpiece 2 on the opposite surface 6 of the anvil main body 3 at a predetermined reduction rate. Forging can be performed by pressing. When the work piece 2 is rolled down by the anvil body 3, the surface of the work piece 2 moves in a direction perpendicular to the direction of the roll down (for example, the left and right direction in FIG. 1), and the material (work piece 2) flows. However, the restraint portion 5 of the present invention, that is, the uneven portion 7 suppresses the flow of the material at the time of rolling down, and gives a large distortion to the inside of the workpiece 2, thereby compressing the internal defect 8 of the workpiece 2 by pressure bonding. It is decreasing.

Hereinafter, the forging method of the workpiece of the present invention will be described.
In the method for forging a workpiece according to the present invention, as shown in FIG. 2, first, the workpiece 2 to be forged is selected (S1). For the selected workpiece 2, the internal defect evaluation index Q shown in Equation (1) when the workpiece 2 is rolled down is obtained, and the rolling reduction is obtained (S 2).
That is, in S2, the reduction rate of the anvil 1 with respect to the workpiece 2 is changed little by little, and the workpiece 2 is reduced at the center position O (see FIG. 2) when the workpiece 2 is reduced at a predetermined reduction rate. An internal defect evaluation index Q shown in the equation (1) is obtained by deformation analysis in computer simulation for hydrostatic stress or equivalent stress. Then, a relationship (table) between each internal defect evaluation index Q and the rolling reduction is created. Here, the deformation analysis when calculating the internal defect evaluation index Q can faithfully reproduce the state of plastic deformation and elastic deformation in the material and can simulate the internal stress state, and is a software for performing deformation analysis. Uses, for example, general-purpose products such as ABAQUS.
For example, for a predetermined material with conditions: cold upset, shape: Φ100 × H150, elastic modulus: E = 2.05E + 05, Poisson's ratio: ε = 0.29, each internal defect evaluation index as shown in Table 1 Create a relationship (table) between Q and rolling reduction.

However, this Table 1 shows the relationship (correspondence table) between the internal defect evaluation index Q and the reduction ratio for the materials shown above, and is not limited to this. It is preferable to obtain the relationship (correspondence table) between the internal defect evaluation index Q and the rolling reduction for each workpiece 2 by the material, shape, temperature, and friction.
Next, with respect to the selected workpiece 2, the state of occurrence of internal defects 8 after the production of the steel ingot of the workpiece 2 (before forging) is estimated (S 3). That is, before forging, that is, before reduction, the position (defect position) where the internal defect 8 occurs in the workpiece 2, the defect size of the internal defect 8, and the defect shape are estimated using fluidized solidification analysis. In this fluidized solidification analysis, computer simulation is performed using various conditions when ingoting into an ingot or the like, and thereby a defect position, a defect size, and a defect shape can be estimated. For example, fluidized solidification analysis is described in "Kobe Steel Technique vol.56 No1 Apr.2006 Application of Solidification / Flow Simulation Technology to Cast Forged Steel Products" and "Kobe Steel Technique Vol.51 No1 Dec.2001". As software that is the same as the technology and performs flow solidification analysis, for example, products such as ADSTEFN and JSAST are used.
As shown in FIG. 3, the defect position refers to the distance from the rolling surface 2 a squeezed by the anvil to the center of the nearest internal defect (sometimes referred to as the uppermost internal defect 8 a) 8 a and the height of the workpiece 2. This is expressed using H. That is, the distance from the reduction surface 2a to the center of the uppermost internal defect 8a is the defect position. A defect position of 1/2 indicates that the uppermost internal defect 8a exists at a distance of 1 / 2H from the rolling surface 2a, and a defect position of 1/3 indicates that 1% from the rolling surface 2a. This means that the uppermost internal defect 8a exists at a distance of / 3H, and that the defect position is 1/4 means that the uppermost internal defect 8a exists at a distance of 1 / 4H from the rolling surface 2a. It shows that. As can be seen from the above, the present invention is based on the uppermost internal defect 8a that is closest to the reduction surface 2a and is difficult to close by reduction.

As shown in FIG. 3, the defect size represents the size of the internal defect 8 (the uppermost internal defect 8a) using the width D of the workpiece 2 and the width d of the internal defect 8. In other words, the defect size is the ratio (d / D) of the width of the internal defect 8 to the width of the workpiece 2.
The defect shape represents the shape of the internal defect 8 using the width d of the internal defect 8 and the height h of the internal defect 8. The closer the h / d value is to 1, the more the shape of the internal defect 8 is. It becomes substantially the same as a circle, and the larger the value of h / d, the more the shape of the internal defect 8 becomes elliptical or tapered.

  Next, after estimating the defect position, the defect size (d / D), and the defect shape (h / d) by the flow solidification analysis, using these, the equations (2) to (8) A minimum value Qmin for closing the defect is calculated.

  Specifically, the coefficients α, β, γ, and ζ are obtained by substituting the defect positions into the equations (5) to (8) (S4). For example, if the defect position is 1/2, 0.5 is substituted for each equation, and if the defect position is 1/4, 0.25 is substituted for each equation. Next, the obtained coefficients α, β, γ, ζ and defect size (d / D) are substituted into the equations (5) and (6), and a coefficient A (sometimes referred to as a first coefficient) and a coefficient B (Sometimes referred to as a second coefficient) (S5). The calculated first coefficient A, second coefficient B, and defect shape (h / d) are substituted to determine the minimum value Qmin (S6). Then, the reduction rate at the minimum value Qmin is selected from the correspondence table between the internal defect evaluation index Q and the reduction rate obtained in advance, and the workpiece 2 is reduced by the anvil at least above the selected reduction rate. (S7).

For example, as shown in Table 1, when the minimum value Qmin is 0.4159, the reduction ratio is 57%. Therefore, when the workpiece 2 is actually reduced, the reduction is performed at 57% or more.
However, if there is no rolling reduction that matches the minimum value Qmin in the correspondence table, the lowest value Qmin that is the next higher value than the calculated minimum value Qmin is selected, and the rolling reduction corresponding to the minimum value Qmin is selected. .
As shown in Table 1, when the minimum value Qmin is 0.4233, a numerical value (0.430734) next higher than the minimum value Qmin is selected and corresponds to the minimum value Qmin (0.430734). Select the reduction ratio (58%).

The process of deriving equations (2) to (8) will be described.
First, the inventor performs reduction on a material (sample) having a defect as shown in FIG. 4, and the internal defect evaluation index Q when the reduction is performed, and the void area ratio of the defect (defect crushing degree). Various experiments were conducted to investigate the relationship. Then, after dividing each defect position (P / H) and each defect shape (h / d), the relationship between the internal defect evaluation index Q and the void area ratio of the defects is arranged as shown in FIG. As a result, it was found that the internal defect evaluation index Q and the void area ratio differ depending on the position of each defect (P / H) and each defect shape (h / d).

Therefore, the inventor conducted further verification and conducted various experiments on the minimum value Qmin when the internal defect was closed and the defect shape (h / d). By this experiment, the minimum value Qmin and the defect shape (h / D) is summarized as shown in FIG.
As a result, as shown in FIG. 6, it was found that the minimum value Qmin and the defect shape (h / d) have a linear relationship. As shown in Expression (2), the relationship between the minimum value Qmin and the defect shape (h / d) is expressed by using a coefficient A (sometimes referred to as a first coefficient) and a coefficient B (sometimes referred to as a second coefficient). I decided to represent it.

Here, as shown in FIG. 6, even if the defect shape (h / d) is the same value, the minimum value Qmin for closing the internal defect 8 is different if the defect size (d / D) is different. I understood.
Therefore, the first coefficient A, the second coefficient B, and the defect size (d / D) are summarized by experimental data.
FIG. 7 summarizes the relationship between the first coefficient A and the second coefficient B and the defect size (d / D) based on data from experiments and the like. As a result, as shown in FIG. 7, the first coefficient A can be expressed by the defect size (d / D) and the coefficients α and β as shown in Expression (3), and the second coefficient B can be expressed by Expression (4). As shown, the defect size (d / D) and the coefficients γ and ζ can be expressed.

Looking at FIG. 7 in detail, it was found that the first coefficient A and the second coefficient B differ depending on the defect position even with the same defect size (d / D). That is, it was found that even if the defect shape (h / d) is the same value, the minimum value Qmin for closing the internal defect 8 is different if the defect position is different.
Specifically, as shown in FIG. 7A, the values of the first coefficient A and the second coefficient B with respect to the defect size (d / D) at the defect position 1 / 2H, and FIG. As shown, the values of the first coefficient A and the second coefficient B for the defect size (d / D) at the defect position 1 / 3H are different.

Further, as shown in FIG. 7C, the values of the first coefficient A and the second coefficient B at the defect position 1 / 2H and the defect position 1 / 3H are also different from the defect position 1 / 4H.
Therefore, since the first coefficient A and the second coefficient B differ depending on the defect position, the coefficients α and β shown in the equation (2) for obtaining the defect position and the first coefficient A, the defect position, and the second coefficient B The coefficients γ and ζ shown in Equation (3) for obtaining the above are summarized.
FIG. 8 summarizes the defect positions and the coefficients α, β, γ, and ζ for obtaining the first coefficient A and the second coefficient B.

FIG. 8A shows the influence (change) of the coefficients α and β on the defect position, and FIG. 8B shows the influence (change) of the coefficient γ on the defect position. FIG. 8C shows the influence (change) of the coefficient ζ on the defect position.
As shown in FIG. 8, the minimum value Qmin varies depending on the defect position. The coefficient α is obtained from the equation (5) according to the defect position, and the coefficient β is determined from the equation (6) according to the defect position. ). Further, the coefficient γ is obtained from the equation (7) according to the defect position, and the coefficient ζ is obtained from the expression (8) according to the defect position.

Therefore, the minimum value Qmin for closing the internal defect can be obtained based on the defect position, defect size, and defect shape of the internal defect.
As described above, according to the present invention, in the forging method in which forging is performed while the internal defect 8 of the workpiece 2 is closed, first, the interior represented by the formula (1) corresponding to the workpiece 2 to be forged is shown. Obtain the relationship between the defect evaluation index Q and the reduction ratio, estimate the defect position, defect size, and defect shape of the internal defect before forging, and evaluate the internal defect based on the estimated defect position, defect size, and defect shape. A minimum value Qmin for closing an internal defect is obtained at an index Q, and the workpiece is rolled down with an anvil at a rolling reduction rate corresponding to the minimum value Qmin or higher.

  As a result, forging can be performed by reducing the anvil considering the characteristics (defect position, defect size, defect shape) of the internal defects 8 inherent in the workpiece 2 before forging, and the internal defects 8 are securely closed. Can be made. That is, the internal defect 8 can be reliably closed and extinguished only by changing the rolling reduction actually reduced according to the characteristics of the internal defect 8. Further, according to the present invention, the minimum value Qmin is obtained with reference to the defect position, defect size, and defect shape in the uppermost internal defect 8a, and forging is performed by determining the reduction ratio that is actually reduced at the obtained minimum value Qmin. Is going. Therefore, even if there are many internal defects 8 apart from the uppermost internal defect 8a, if the reduction is performed on the basis of the reduction ratio determined in this way, it is not necessary to perform complicated reduction control or the like. The internal defect 8 inherent in the place can also be reliably closed.

Now, even if the rolling reduction is the same, if the shape, material, temperature, friction, etc. (forging conditions) of the workpiece 2 are different, the stress generated in the workpiece 2 may be different. For example, even if the rolling reduction is the same, if the material is easily deformable, the stress (e.g., equivalent stress) and strain (equivalent strain) generated inside will be large.
As described above, the internal stress / strain state has various effects to close the internal defect 8, and according to the present invention, the stress generated in the work piece 2 during the reduction. -It is considered by the internal defect evaluation index Q that can show strain. And according to this invention, after calculating | requiring the minimum value Qmin of the internal defect evaluation index Q which can close the internal defect 8 reliably, an appropriate rolling reduction rate is calculated | required from the minimum value Qmin of the internal defect evaluation index Q, Since the reduction is performed at the reduction rate, the internal defect 8 can be reliably closed.

  Table 2 summarizes an example in which forging was performed by the forging method of the workpiece 2 of the present invention and a comparative example in which forging was performed by a method different from the forging method of the workpiece 2 of the present invention. It is.

As shown in Table 2, in the example and the comparative example, the internal defect 8 of the workpiece 2 was evaluated by UT evaluation (ultrasonic measuring device). As shown in Table 2, when the internal defect 8 was less than a predetermined value (not present), it was determined as “good”. Further, as shown in Table 2, if the internal defect 8 is greater than or equal to a predetermined value (existing), the defect is “x”.
In the first to sixth embodiments, the defect position, the defect size, and the defect shape are estimated, and the minimum value Qmin of the internal defect evaluation index for closing the internal defect 8 based on the estimated defect position, defect size, and defect shape. (Calculated Qmin), and the workpiece 2 is rolled down with an anvil at a rolling reduction (applied rolling reduction) larger than the rolling reduction (calculated rolling reduction) corresponding to this minimum value Qmin (calculated Qmin). Internal defect 8 was not found (Table 2, evaluation “◯”).

In Comparative Examples 1 to 6, the estimation work for the defect position, the defect size, and the defect shape is not performed, and the minimum value Qmin of the anvil that closes the internal defect 8 is not obtained based on the defect position, the defect size, and the defect shape. In addition, when it was crushed with an anvil, an internal defect 8 was observed (Table 2, evaluation “×”).
In Comparative Examples 1 to 10, as in the present invention, the defect position, defect size, and defect shape are estimated to obtain the minimum value Qmin (calculated Qmin), and the applied value of the actually applied internal defect evaluation index Is calculated, the applied Qmin applied is lower than the calculated Qmin, and the actual reduction ratio (applied reduction ratio) is the reduction ratio (calculated reduction) required for closing internal defects. Rate) was also low.

The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. For example, in the above embodiment, the defect position, the defect size, and the defect shape are estimated by the flow solidification analysis, but the present invention is not limited to this.
For example, in a model experiment, a sample cut out at a predetermined length (for example, cut out by 1 mm in the width direction and the height direction) before the work material 2 melted and solidified in advance is cut out as shown in FIG. The weight is measured from 2A and the density in the height direction and the width direction is measured. The low density portion is considered to have an internal defect, and the defect position, the size of the defect and the defect are determined from the density distribution in the height direction and the width direction. The shape may be estimated. In the example shown in FIG. 9, in the density distribution in the height direction and the width direction, it is assumed that the defect exists in a range where the density is lower than the threshold value, and the length of the range is the width d of the internal defect 8 and the internal defect 8. The height is h.

  Further, when a plurality of internal defects exist in the workpiece 2, the following may be performed. First, a defect shape, a defect position, and a defect size generated during solidification are estimated by simulation or the like, and a defect position with the same defect shape (h / d) is obtained. At this time, a defect position is obtained for each defect shape (h / d). That is, when there are a plurality of internal defects, a defect position is obtained for each defect shape of the internal defect. Then, for each defect shape, the minimum value Qmin is obtained using the defect position and the defect size, and the largest of the obtained minimum values Qmin is forged (reduced). adopt.

  The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a block diagram of an anvil. It is a flowchart which shows the forge method of a workpiece. It is a figure which shows the definition of a defect position, a defect size, and a defect shape. It is a sample figure of the material for calculating | requiring the relationship between an internal defect evaluation index | exponent and the void | hole area ratio of a defect. It is a figure which shows the relationship between the internal defect evaluation index | exponent Q and the void | hole area ratio of a defect. It is a related figure of rolling reduction (minimum value Qmin) and defect shape (h / d). FIG. 4 is a relationship diagram between a defect shape (h / d) and a defect size (d / D), where (a) shows a defect shape (h / d) and a defect size (d / D) at a defect position 1 / 2H. (B) is a relationship diagram between a defect shape (h / d) and a defect size (d / D) at a defect position 1 / 3H, and (c) is a diagram at a defect position 1 / 4H. It is a related figure of defect shape (h / d) and defect size (d / D). FIG. 4 is a relationship diagram between a defect size (d / D) and a defect position, where (a) is a relationship diagram between the defect position and a coefficient α and a coefficient β, and (b) is a relationship between the defect position and the coefficient γ. It is a relationship figure, (c) is a relation figure of a defect position and coefficient ζ. It is the figure which showed another method of estimating a defect position, the size of a defect, and a defect shape.

Explanation of symbols

1 Anvil 2 Work material 3 Anvil body

Claims (4)

In the forging method in which forging is performed while closing the internal defect of the workpiece by reducing the workpiece with an anvil,
Corresponding to the work material to be forged, the relationship between the internal defect evaluation index and the reduction ratio expressed by the formula (1) is obtained, and the defect position, defect size and defect shape of the internal defect before forging are estimated, and this estimation is performed. Based on the defect position, the size of the defect and the defect shape, the minimum value of the internal defect evaluation index necessary to close the internal defect,
A method for forging a workpiece, wherein the workpiece is rolled down with an anvil at a rolling reduction corresponding to the minimum value or more.
The method for forging a workpiece according to claim 1, wherein a minimum value of the internal defect evaluation index is obtained from equation (2).
The forging of the workpiece according to claim 2, wherein the first coefficient (A) and the second coefficient (B) of the expression (2) are obtained by using the expressions (3) to (8). Method.
  The solidification analysis is used when estimating the defect position of the internal defect, the defect size and the defect shape of the internal defect, and the deformation analysis is used when obtaining the internal defect evaluation index. The forging method of the workpiece of any one of 1-3.