JPS62259631A - Deciding method for optimum anvil block width ratio in forge drawing - Google Patents

Abstract

PURPOSE:To decide the optimum anvil block width ratio enabling to secure the inner part quality by clarifying the closing conditions of the inner part gap with the relation with a forge drawing conditions. CONSTITUTION:The optimum upper anvil width ratio Wu/Ho and lower anvil width ratio ZL/Ho are found as per the following, in case of the forge drawing of the steel ingot of its height Ho between the upper anvil 1 of the upper anvil width Wu and the lower anvil 2 of the lower anvil width WL. Now, in case of Q being taken as a gap closing parameter, Pav the mean hydrostatic stress of the steel ingot center part, sigmaeq the corresponding plastic strain amount to the steel ingot center, N the pass times in forge drawing, gamma the compression factor, C1=1/3, C2=2.37, C3=2/3 and C4=7.86, the values of Wu/Ho and WL/Ho which are within the range satisfying the equation 1 are found under the conditions of conditional 4, 5, and the anvil width ratio enabling to secure the sound quality and close the inner part gap is found.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for determining an optimal anvil width ratio when forming a large forged steel product with a sound internal structure by forging process.

(Prior Art) Since voids exist inside a large steel ingot, these internal voids must be crimped (closed) by forging processing to create a healthy structure.

As this forging process method, for example, the ■-■ anvil forging method, the warm forging method, the FM forging method, etc. are known.

However, in conventional methods, the conditions for closing the internal voids, which affect internal quality, were not always clear.
Large steel forgings were manufactured by combining upsetting and forging multiple times (see Figure 1). As a result, not only the forging process becomes redundant, but also the energy loss and scale loss due to the increase in the number of heats are large, which causes an increase in cost. Furthermore, due to the long manufacturing period, the product delivery period from order receipt to delivery was often extremely long.

(Problems to be Solved by the Invention) The problems in the conventional forging and stretching method described above are due to the fact that the conditions for closing the internal voids are not necessarily clear.

The cross-sectional shape of the forged material, the anvil shape, and the anvil width ratio have long been known as factors that have a large effect on the crimping (closing) of the void, but these have not yet been systematically investigated and analyzed.

Therefore, the present invention relates to the anvil width ratio among the above factors, and by clarifying the internal gap closing conditions in relation to the forging processing conditions, the optimum anvil width necessary to ensure internal quality can be determined. The purpose is to present a method to find the shortest forging and stretching method by finding the ratio.

(Means for solving the problems) In order to achieve the above object, the present invention takes the following measures. That is, the feature of the present invention is that the optimum upper anvil width ratio (W□/!Io) and upper anvil width ratio (W□/!Io) and Anvil width ratio (L
/1lo), eq Δεeq=c+ + 1 n (C4・Wu/Ho
) ・r-■Q; Gap closure parameter PavH Average hydrostatic stress eq at the center of the steel ingot; Equivalent stress Δεeq; Average equivalent plastic strain amount N at the center of the steel ingot; Number of forging passes subscript i; Bus N .

γ: compression ratio Wu; upper anvil width HL; upper anvil width ■o; height of steel ingot C+ = 'ASCZ = 2.37, C:l = 2A-
C4 = 7.86Wu/Ho≧0.43 =----
−−−−−−−−−−−−−−−−−−・−■W L
/) io=0.8 −−−−−−−−−−−−−−−
−・−−−−−−−Using the conditional expression ■, set Wu/Ho so that the direction /Ho s Wc /Ho is within the range that satisfies the expression ! to and -, /
The point is to find the value of HO.

(Function) The present invention, as shown in FIG. /1lo) and upper anvil width ratio (
WL /+10). Here, the distance, direction, and Ilo refer to the dimensions shown in FIG.

First, the conditional expressions used in the present invention will be explained.

(1) Internal void closing condition In order for the voids in a steel ingot to close, local hydrostatic stress and equivalent strain are largely involved. Therefore, the present invention attempts to determine the optimum processing conditions by determining the relationship between this hydrostatic pressure stress and the equivalent strain.

The volumetric strain rate of a material whose density changes, for example, a powder sintered body, is expressed by the following equation.

Here, dεV; volumetric strain increment ρ; relative density ratio (density after forging/true density) p; hydrostatic stress feqH equivalent stress dεeq; equivalent plastic strain increment a, m, n high material parameter ρi 0 of the above formula ■ The left side is a quantity that depends on the material conditions determined by the initial density ratio ρ1, and the right side is a quantity that depends on the stress load path determined by the processing conditions.

Now, when ρ becomes ρ, if the internal void of the forged steel product is substantially closed, then from the left side of equation 0, ρ r ρ.

The limit value Q can be found by

Therefore, by setting the right side of ■2 as follows, the internal void of the steel forging is substantially closed. That is, by matching the stress load path determined by the processing conditions to (2), the internal voids of the steel forging are closed. In other words, the internal void is closed by processing conditions that match equation 0. Here, Q is named the void closure parameter.

Now, in order to use the 0 formula, Q by the 0 formula.

In order to obtain Qf, it is necessary to obtain the material parameter a+ IIl+ n+ and ρ assuming that the internal void is closed.

Therefore, first, each forging and stretching method A and B shown in Fig. 3.

For C, the relationship between the equivalent strain εeq and the hydrostatic stress P at each rolling reduction rate is determined by theoretical analysis, and the void closing parameter Q is calculated for each rolling reduction rate using the right side of Equation 0.

Next, a rolling experiment of the sintered body is performed in each forging method A, B, and C, and the density ratio ρ at each rolling reduction rate is determined.

FIGS. 4 and 5 show the relationship between the gap closure parameter Q determined by theoretical analysis in this manner and the density ratio ρ determined by experiment of the sintered body.

As is clear from FIGS. 4 and 5, it can be seen that the relationship between the density ratio ρ and the gap closure parameter Q is kept almost constant even with various forging methods and rolling reductions. Therefore, from FIGS. 4 and 5, the material parameter a on the left side of equation 0,
Determining m and n, a −2,7m =0.5 n
=2.0. However, ρ = 0.85 (initial density ratio at the center of the steel ingot).

Next, find the relative density ratio ρ when the internal void is closed.

When the internal void is closed, it means a state in which no defects are detected when internal defects in a forged steel product are detected by ultrasonic waves. Therefore, the distribution of remaining internal voids was investigated in a sintered body experiment, and the characteristics shown in FIG. 6 were obtained.

According to Fig. 6, the area ratio of voids with a grain size of 20 μm or more is 0.09χ when the initial density ratio is 0.85, but decreases as processing progresses, and becomes 0χ when the density ratio is 0.97 or more. As a result, the void disappears. In ultrasonic flaw detection, uniform flaw defects of 20 μm or more are detected as defective, so a judgment can be made based on the case of particle size 20 μm in the above experiment. Therefore, in the present invention, the relative density ratio ρ when the internal void is closed is ρ, =0.97・・・−・−−−−−−−−−−−
−−−−〜−−−−−−−−1・・−・−・−・−・・
−・− [phase].

Therefore, the above equation 0 and a = 2.7 m = 0.5
By substituting n=2.0 ρi =0.85 into equation 0, Qf #0.16−・−・−・−−−−−−−・・
−・−・−・・−１−−−−−・−・・−・・−・−・
-■ Therefore, from ■2, the closing condition formula % formula % However, it is difficult to calculate the gap closing parameter Q using formula 0 depending on the actual forging process, so for practical purposes, it can be replaced with the following formula. .

Here, N is the number of forging passes, which is added for the bus whose purpose is to press the internal voids in the entire process. Furthermore, Pav is the average value of the hydrostatic stress during the time when the processing strain Δεeq is applied in the i-bath, and each is evaluated by the value at the center of the steel ingot where the internal voids are most densely packed.

To summarize the above, when performing forging and stretching N times, if processing conditions are selected that take a stress load path that satisfies the conditional expression, the internal voids will be closed and a sound forged steel product can be obtained. It can be done.

(II) Relationship between closure condition equation ■ and processing conditions By the way, equation 0 can be calculated by theoretical analysis or experiment, but in practice,
It would be convenient if it could be evaluated based on processing conditions such as anvil dimensions.

Therefore, in the present invention, the anvil width ratio (Wu/l(o, W
The relationship between Pav/eq and Δεeq was investigated. The results are shown in FIGS. 7 and 8.

That is, as mentioned above, the anvil width ratio is a factor that has a large effect on the internal gap crimping, but in the present invention, the anvil width ratio and Paν/(7eq, Δ
We investigated the relationship between εeq and obtained the results shown in Figures 7 and 8.

The following relational expression was determined from the above figures 7 and 8.

Pav ==c, ' in (Cz ' WL /HO)'
−−−−−'−”−”−'−■feq Δεeq=C3HIln (C4・Wu/Ho) ・r
-'---- ■Here, parameters C+, Ct, C5
, C6 have the following values.

C+=Z C2 depth 2.37 C:l-% C4,=7.86 In other words, formula 0 is derived from Fig. 7, and from Fig. 8 Wu/J
Equation 0 is derived except when io is small.

From the above, the closing condition formula (■) can be calculated by substituting the 0 and 0 expressions to obtain the anvil width ratio (1) L/Ho, Wu/Ho
) can be evaluated.

That is, by optimally selecting the anvil width ratio, the internal void can be effectively closed.

(I [I) Scope of Application of Closure Conditional Formula Furthermore, the results of examining the anvil width ratio and training effect are shown in FIGS. 9 and 10.

That is, in anvil forging, the strain distribution and stress distribution inside the steel ingot are not uniform and differ in each part. Therefore, in order to clarify the characteristics of stress and strain distribution in anvil forging, we investigated the maximum value and peak position of equivalent strain.

Figure 9 shows the relationship between the maximum value of equivalent strain and the ratio of upper and lower anvil widths. The maximum value of the equivalent strain at Wu/loo = 0.3 increases rapidly until the upper anvil width ratio -L/Ho reaches about 0.8, but hardly changes when Wt/lio becomes 0.8 or more. Upper anvil width ratio Wu/H.

The same tendency is observed when =0.57.

Therefore, from Fig. 9, the conditions for efficiently applying considerable strain are as follows: Wt, /llo≧0.8 −−−−−−−−−−−−
−−−−−−−−−−−−−−−■■ is obtained.

FIG. 10 shows the influence of the upper and lower anvil width ratios on the peak position of equivalent strain. The peak position is the upper anvil width ratio Wu/I
'AHo when lo = 0.3, %ll when 0.57.

and! 'G1) between o and 'y at the center of the steel ingot when 0.8
Becomes AHo. That is, as the upper anvil width ratio -u/Ha increases, the peak position shifts to the center of the steel ingot where internal voids are dense, and it hardly depends on the upper anvil width ratio. From this, the conditions for the rolling effect to start acting on the center where the internal voids are densely packed are as follows: Wu/llo ≧0.43 −−−−−−−−−−−
−−−−−−−−−−−−■ is obtained.

By using the above (1) and (2), it is possible to efficiently close the internal void in the center of the steel ingot.

To summarize the above, under the conditions of formula ■, 0, use formula By determining this, it is possible to efficiently close the internal void.

Figure 1 is a graph of the above relationship.

FIG. 1 shows that, for example, when the number of buses N=4, the value of WL/llo SWu/)to can be selected within the range indicated by dots. A straight line with an inclination of 45° that passes through the origin in Figure 1 has W
This is to exclude this range because u<Wl, and the anvil becomes unstable. Theoretically, an area above the same straight line may be selected.

Moreover, from FIG. 1, it is clear that it is meaningless to adopt N>6. Therefore, the forging process bath for the purpose of internal gap compression bonding is limited to a maximum of six times.

(Example) Using the 0 to 0 formula according to the present invention, the upper and lower anvil width ratio (Wu/
Find Ho, WL/)io).

In actual forging and drawing, in order to exert a forging effect on the center of the forged material, the compression ratio T applied in one rolling is usually 1.
5% or more is required. Therefore, by setting γ=0.15 and determining the number of passes from the relationship between the upper and lower anvil width ratios and the number of passes shown in FIG. 1, an appropriate upper and lower anvil width ratio can be selected for gap crimping. An example selected in this way is shown in Table 1.

Table 1 Example of combination of anvil width ratio (compression ratio 15χ) 1st
) shows the difference between the conventional process and the forging process to which the present invention is applied. By applying the present invention,
Since reliable gap crimping can be achieved with a predetermined number of baths, the conventional 5th and 6th steps can be shortened. This is approximately 15χ
It saves energy.

(Effects of the Invention) By designing a forging pass schedule based on the present invention, it is possible to sufficiently ensure internal quality and at the same time select the most efficient forging processing conditions. The process can be shortened by omitting the mixing process, which greatly contributes to cost reduction and sugar content reduction.

[Brief explanation of drawings]

Fig. 1 is a graph showing the conditional expression of the present invention, and is a graph showing the relationship between the upper and lower anvil width ratio and the number of passes; Fig. 2 is a perspective view for explaining the forging process according to the present invention; FIG. 3 is a cross-sectional view showing various forging and drawing methods, and FIGS. 4 and 5 are graphs showing the relationship between density ratio and gap closing parameter according to various forging and drawing methods. Figure 6 is a graph showing the relationship between void density ratio and area ratio, Figure 7 is a graph showing the influence of anvil width ratio on the average hydrostatic stress in the center, and Figure 8 is a graph showing the effect of the anvil width ratio on the equivalent strain in the center. Graph showing the influence of the anvil width ratio. Figure 9 is a graph showing the influence of the anvil width ratio on the maximum value of equivalent strain. Figure 10 is a graph showing the influence of the boss anvil width ratio on the peak position of the equivalent strain distribution. FIG. 1) is a comparison diagram of a conventional forging process and a forging process to which the present invention is applied. 1--upper anvil, 2--upper anvil, 3--steel ingot (forged material). Join Kobe Steel Co., Ltd. No. 7 Fig. 9 Graduation CB WL / H. Figure 8 Figure 10 - F Small Income '1) % Wl / H0 Procedures Master Book 1 Issue) June 17, 1985

Claims (1)

[Claims] (1) Optimal upper anvil width ratio (W_U/H_
O) and the lower anvil width ratio (W_L/H_O), Q=Σ^N_i_=_1(Pavi)/(σeqi)Δ
εeqi≧0.16・・・・・・・・・[1] However, (Pa
v)/(σeq)=C_1・ln(C_2・W_L/H
o)・・・・・・・・・[2]Δεeq=C_3・ln(C
_4・W_U/H_O)・γ・・・・・・・[3]Q;
Void closure parameter Pav; average hydrostatic stress σeq at the center of the steel ingot; equivalent stress Δεeq; average equivalent plastic strain amount N at the center of the steel ingot; number of forging passes subscript i; pass No γ; compression ratio W_U; upper Anvil width W_L; Lower anvil width H_O; Steel ingot height C_1=1/3, C_2=2.37, C_3=2/3,
C_4=7.86W_U/H_O≧0.43・・・・・・
・・・・・・・・・・・・・・・［4］W_L/H_O
=0.8・・・・・・・・・・・・・・・・・・［
Using the conditional expressions in [5], W_U/H_O and W_L are adjusted so that W_U/H_O and W_L/H_O are within the range that satisfies the expressions [1] under the conditions of expressions [4] and [5] above. /
A method for determining an optimal anvil width ratio in forging and stretching processing, characterized by determining the value of H_O.