JP2021062391A - Forging device for steel material and manufacturing method for steel material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a forging load required for forging with various steel types. SOLUTION: A first press machine 20 for compressing and plastically deforming a steel material 100 with a predetermined strain amount ε and a first strain rate ε dot, and a steel material 100 plastically deformed by the first press machine 10 are subjected to a predetermined steel material temperature T or higher. A predetermined strain amount ε and a first strain rate ε so that the softening rate X calculated by Equations 1 to 2 is 0.9 or more, and the transport unit 30 which is conveyed over a predetermined inter-process time δ while keeping warm. A control unit 50 for controlling a dot, a predetermined inter-process time δ, and a predetermined steel material temperature T was provided. [Selection diagram] Fig. 1

Description

The present invention relates to a steel material forging apparatus and a method for manufacturing a steel material.

In recent years, with the response to environmental problems and the diversification of power systems, the mechanical properties required for forged products constituting the power system of automobiles have become more severe. In order to obtain excellent mechanical properties, it is also necessary to adopt a newly developed new alloy. Therefore, a step of forging various raw materials ranging from conventionally used steel materials to newly developed new alloys into a desired shape is indispensable.

For example, the forging method described in Patent Document 1 is disclosed as a method for forging a nickel-based alloy having higher heat resistance at a relatively low temperature. In this method, the crystal grains of the nickel-based alloy are made finer by displacement of the two anvils sandwiching the nickel-based alloy and applying a huge strain to the nickel-based alloy, and the temperature of the nickel-based alloy is lowered to 800 ° C. or lower. While holding, superplastic forging is performed by controlling the strain rate.

Japanese Unexamined Patent Publication No. 2013-173166

By the way, when an alloy having high deformation resistance is used for a forged product, there are problems such as an increase in forging load and an increase in stress acting on the die, which shortens the life of the die and makes it impossible to process a product having a complicated shape. Occurs.

Therefore, it is important to reduce the forging load in forged parts and the like used in automobiles. However, no forging method has been proposed so far that can apply load reduction regardless of the steel type.

The present invention has been made in view of the above points, and an object of the present invention is to make it possible to reduce the forging load required for forging with various steel types.

In order to achieve the above object, the invention according to claim 1 is a first press machine (20) for compressing and plastically deforming a steel material (100) at a predetermined strain amount and a first strain rate, and a first press machine. A transport unit (30) that transports the steel material that has been plastically deformed by the method over a predetermined inter-process time while keeping the temperature above the predetermined steel material temperature, and a second strain that compresses and plastically deforms the steel material that is transported by the transport unit. 2 Press machine (40), the predetermined strain amount is ε, the first strain rate is ε dot, the predetermined inter-process time is δ, the predetermined steel material temperature is T, and R is the gas constant, A, Q', When C1, C2, and p are constants determined by the material of the steel material,

数式１〜数式２で算出される軟化率（Ｘ）が０．９以上となるよう所定のひずみ量、第１ひずみ速度、所定工程間時間および所定鋼材温度を制御する制御部（５０）と、を備えた鋼材の鍛造装置。

A control unit (50) that controls a predetermined strain amount, a first strain rate, a predetermined inter-process time, and a predetermined steel material temperature so that the softening ratio (X) calculated by the formulas 1 to 2 is 0.9 or more. Steel forging equipment equipped with.

According to this, the control unit sets a predetermined strain amount, a first strain rate, a predetermined inter-process time, and a predetermined steel material temperature so that the softening rate (X) calculated by the formulas 1 and 2 is 0.9 or more. Since it is controlled, the forging load required for forging can be reduced with various steel types.

Further, as in the invention of claim 4, the steel material forging device according to claim 1 can be regarded as a method of manufacturing a steel material.

The reference reference numerals in parentheses attached to each component or the like indicate an example of the correspondence between the component or the like and the specific component or the like described in the embodiment described later.

It is a figure which showed the whole structure of the forging apparatus of a steel material. It is a figure which showed the flow of the low load forging process. It is the figure which showed the state which changed into the form which the dislocation was accumulated in the structure of a steel material by press working. It is the figure which showed the state that the dislocation accumulated in the structure of a steel material recovered and recrystallization occurred. It is a figure which showed the relationship between the deformation resistance and the strain amount when the strain rate in the 1st forging step was changed. It is a figure which showed the measurement result of the deformation resistance in the 1st and 2nd forging steps of a test piece when the compressibility of the 1st forging step was 10%, and the time δ between predetermined steps was 30 seconds. It is a figure which showed the measurement result of the deformation resistance in the 1st and 2nd forging steps of a test piece when the compressibility of the 1st forging step was 30%, and the time δ between predetermined steps was 30 seconds. It is a figure which showed the measurement result of the deformation resistance in the 1st and 2nd forging steps of a test piece when the compressibility of the 1st forging step was 50%, and the time δ between predetermined steps was 30 seconds. It is a figure which showed the measurement result of the resistance of the 1st and 2nd forging steps when the compressibility of the 1st forging step was 45%, and the time δ between predetermined steps was 0.1 second. It is a figure which showed the measurement result of the deformation resistance when the time δ between predetermined steps was set to 1 second. It is a figure which showed the measurement result of the deformation resistance when the time δ between a predetermined process is 10 seconds. It is a figure which plotted the softening rate of a test piece by changing the time between predetermined steps. It is a figure which showed the structure which carries out the 1st forging process and 2nd forging process by one press machine.

The steel material forging apparatus according to this embodiment will be described with reference to FIGS. 1 to 13. The steel material processed by the forging device according to the present embodiment is used for products and the like constituting the power system of an automobile.

As shown in FIG. 1, the steel forging apparatus includes an induction heating furnace 10, a first press machine 20, a transport unit 30, a second press machine 40, and a control unit 50. In the present embodiment, the steel material 100 is deformed in two forging steps. The steel material 100 of the present embodiment is made of steel containing carbon and manganese.

The induction heating furnace 10 has a heating coil for heating the steel material 100 in a non-contact manner. The steel material 100 is heated in a non-contact manner by passing a high-frequency alternating current through the heating coil. By heating the steel material 100, the deformation resistance of the steel material 100 is reduced and the deformation is facilitated. The steel material heated by the induction heating furnace 10 is conveyed to the first press machine 20 by a conveyor.

The first press machine 20 has a die for forming the steel material 100, and pressure is applied to the steel material 100 with this die to form the steel material 100 into a desired shape. The first press machine 20 applies pressure to the steel material at a predetermined strain amount and a predetermined strain rate to plastically deform it. The amount of strain, the strain rate, and the like can be adjusted by a signal from the control unit 50. The steel material 100 compressed by the first press machine 20 is conveyed to the second press machine 40 by the conveying unit 30.

The transport unit 30 transports the steel material 100 transported from the first press machine 20 over a predetermined inter-process time while keeping the temperature of the steel material 100 at a predetermined steel material temperature or higher. Further, the transport unit 30 can heat the steel material 100 plastically deformed by the first press machine 20 at a temperature equal to or higher than the transformation point of the steel material 100. The heating temperature of the transport unit 30, the time between predetermined processes, and the like can be adjusted by a signal from the control unit 50.

The second press machine 40 has a die for forming the steel material 100 conveyed by the conveying unit 30, and the steel material 100 is compressed with this die to form the steel material 100 into a desired shape. The second press machine 40 applies compression to the steel material at a predetermined strain amount and a predetermined strain rate to plastically deform it. The amount of strain, the strain rate, and the like can be adjusted by a signal from the control unit 50.

The control unit 50 is configured as a computer equipped with a CPU, a memory, an I / O, and the like, and the CPU executes various processes according to a program mechanism in the memory.

Next, the forging process of the steel material 100 of the present embodiment will be described with reference to FIG. In the present embodiment, first, the induction heating step of the steel material 100 is carried out in S100. In this induction heating step, S100 is heated at a high temperature by the induction heating furnace 10.

Next, the first forging step is carried out in S200. In this first forging step, the steel material 100 heated by the induction heating step of S100 is compressed by using the first press machine 20 to form the steel material 100 into a desired shape.

Next, the transfer process is carried out in S300. In this transfer step, the steel material 100 taken out from the first press machine 20 is conveyed to the second press machine 40 over a predetermined time while keeping the temperature of the steel material 100 higher than the predetermined steel material temperature by the transfer unit 30.

Next, the second forging step is carried out in S400. In this second forging step, pressure is applied to the steel material 100 conveyed by the conveying unit 30 using the second press machine 40 to form the steel material 100 into a desired shape. When the above-mentioned process is completed, the main forging process is completed.

In forming the steel material 100 by forging, the present inventors have focused on forming the steel material 100 by dividing it into a plurality of steps as described above, instead of forming the steel material 100 by only one press working. .. That is, after heating the steel material 100 in the induction heating furnace 10, the steel material 100 is press-processed by the first press machine 20 in the first forging process, and the steel material 100 pressed in the transfer process is second-pressed by the transfer unit 30. Transport to machine 40. Then, the steel material 100 conveyed by the transfer unit 30 in the second forging step is pressed by the second press machine 40.

By the way, when the steel material 100 is press-processed, the metal structure constituting the steel material 100 is plastically deformed to cause crystal lattice defects called dislocations. When dislocations are accumulated, the deformation resistance of the steel material 100 increases due to a phenomenon called work hardening.

FIG. 3 shows a state in which the structure of the steel material 100 before being pressed is changed to a form in which dislocations D are accumulated in the structure of the steel material 100 by the press working. (A) represents a polycrystal which is a structure of the steel material 100 before the steel material 100 is pressed. The line means the grain boundary. In (b), as shown in the figure showing the state in which dislocations D are accumulated in the structure of the steel material 100 by press working, the crystal grains constituting the steel material 100 are plastically deformed and elongated by press working, and are elongated. A new dislocation D has occurred.

When the steel material 100 having a large deformation resistance is press-processed by the second press machine 40 in this way, the stress acting on the die increases, and there are problems such as shortening the life of the die and deteriorating the processing accuracy. Occurs.

The present inventors can recover the dislocations accumulated in the steel material 100 by appropriately controlling the conditions for pressing the steel material 100 with the first press machine 20 and the conditions for transporting the steel material 100 with the transport unit 30. It was noted that recrystallization was promoted and the steel material 100 could be softened. If the steel material 100 can be softened in this way, it is possible to accurately enable the steel material 100 when the steel material 100 is pressed by the second press machine 40.

FIG. 4 schematically shows how the dislocation D accumulated in the structure of the steel material 100 is restored and recrystallization occurs. (A) shows a state in which a part of the dislocations D accumulated in the structure of the steel material 100 is recovered, and recrystallized grains R containing no dislocations are newly generated and grown inside. (B) shows a state in which almost all dislocations D accumulated in the structure of the steel material 100 are recovered and a large number of recrystallized grains R are grown. It is known that the progress rate of such recrystallization changes depending on the amount of dislocations given to the steel material due to plastic deformation. Therefore, if the period for transporting the steel material 100 pressed by the first press machine 20 to the second press machine 40 can be appropriately provided according to the process, the dislocation density is reduced by recrystallization and the steel material 100 is softened. It becomes possible to make it.

In order to verify the possibility of load reduction by forging, the present inventors press work with a first press machine 20 using a steel test piece containing 0.3% carbon and 1.5% manganese. The relationship between the deformation resistance and the strain amount ε when the strain rate ε dot was changed was measured. In this specification, a symbol with a dot above ε is referred to as a strain rate ε dot. The unit of the strain rate ε dot is 1 / sec. The test piece used was a small cylinder having a diameter of 8 mm and a height of 12 mm.

First, the relationship between the deformation resistance and the strain amount ε when the strain rate ε dots are changed to 50 / s, 10 / s, 1 / s, and 0.1 / s after heating the test piece to 900 ° C. It was measured.

FIG. 5 shows the relationship between the deformation resistance and the amount of strain when the strain rate ε dot in the first forging step is changed. It was confirmed that the smaller the strain rate ε dot, that is, the slower the press working speed of the test piece, the smaller the deformation resistance.

Further, in order to verify the possibility of load reduction by forging, the present inventors measured the change in the deformation resistance of the test piece when the strain amount ε in the first forging step was variously changed. Here, the first press machine 20 in the first forging step has a predetermined transfer time of 30 seconds for the transfer unit 30 to transfer the steel material 100 from the first press machine 20 to the second press machine 40, and the strain rate ε dot is 1 / s. The strain amount ε of was changed to 10%, 30%, and 50%. The measurement results are shown in FIGS. 6 to 8.

FIG. 6 shows that the first forging by the first press machine 20 deforms the material to a compression rate of 10%, and then the transfer time is held for 30 seconds, and then the second forging by the second press machine 40 causes the compression rate to reach 55%. It shows the change in deformation resistance when deformed. In FIG. 6, it is described as "10%-> 30 sec-> 55%".

FIG. 7 shows that the first forging by the first press machine 20 deforms the material to a compression ratio of 30%, and after holding the material for a predetermined transfer time of 30 seconds, the second forging by the second press machine 40 causes the compression rate to reach 55%. It shows the change in deformation resistance when deformed. In FIG. 7, it is described as "30%-> 30 sec-> 55%".

FIG. 8 shows that the first forging by the first press machine 20 deforms the material to a compression ratio of 50%, and after holding the material for a predetermined transfer time of 30 seconds, the second forging by the second press machine 40 causes the compression rate to reach 55%. It shows the change in deformation resistance when deformed. In FIG. 8, it is described as "50%-> 30 sec-> 55%".

The value of each deformation resistance T2e in FIGS. 6 to 8 is the value of the deformation resistance when the compression ratio in the second forging is 55% and the strain amount is 0.8. The smaller the value of each deformation resistance T2e, the smaller the load of the second forging.

The value of the deformation resistance T2e is smaller in the result shown in FIG. 8 than in the result shown in FIG. That is, the smaller the compression ratio of the first forging, that is, the strain amount ε during press working with the first press machine 20, the more recrystallization progresses during transportation, and the load of the second forging becomes smaller. Do you get it.

Further, in order to verify the possibility of load reduction by forging, the inventors set the strain amount ε, the strain rate ε dot and the predetermined steel material temperature T in the transport portion 30 in the first forging step to be constant, and the time δ between the predetermined steps. The change in the deformation resistance of the test piece when was changed was measured.

The strain amount ε in the first forging step is 45%, and the strain rate is 1 / s. The predetermined steel material temperature T in the transfer step was 900 ° C. Further, in the second forging step, the strain amount ε was changed from 45% to 75%. The strain rate in the second forging step is 1 / s.

9 to 11 show changes in deformation resistance when the time δ between predetermined steps is 0.1 seconds, 1 second, and 10 seconds, respectively.

Here, the softening rate is defined as _{X = (σ m} −σ _0.2 ) / (σ _m −σ _0). However, σ ₀ is the yield stress in the first forging step, σ _m is the final deformation resistance in the first forging step is σ _m , and σ _0.2 is the yield stress in the second forging step. The yield stress is the stress at which the plastic deformation of the steel material 100 starts.

When the softening rate X is calculated based on the data shown in FIGS. 9 to 11, when the predetermined inter-process time δ = 0.1 seconds, X = 0.12, and when the predetermined inter-process time δ = 1 second. , X = 0.68, and when the predetermined inter-process time δ = 10 seconds, X = 0.95.

FIG. 12 is a plot of the softening rate X calculated by changing the time δ between predetermined steps. The longer the time δ between predetermined steps, the larger the time, and the closer to 1. The softening ratio X = 1 means that the dislocations generated in the first forging step have been recovered to form a completely recrystallized structure.

Here, the time between predetermined steps at which the recrystallization rate of the steel material 100 is 0.5 is determined to be δ _0.5 . δ _0.5 is generally referred to as the recrystallization time. In the embodiment shown here, when the predetermined strain amount is ε, the first strain rate is ε dot, and the predetermined steel material temperature is T, the predetermined inter-process time δ _0.5 can be expressed using Equation 1. And said.

なお、Ｒは気体定数（８.３１４［Ｊ／（ｍｏｌ・Ｋ）］）、Ａ、Ｑ’、Ｃ１、Ｃ２は鋼材１００の材料によって決まる定数である。所定工程間時間δ_０．５を用いてＪＭＡＫ（Johnson-Mehl-Avrami-Kolmogorov)の式に回帰させると、鋼材１００の軟化率Ｘは、数式２のように表すことができる。ＪＭＡＫの式とは温度や時間と再結晶率の相関に関する実験データを整理する際にしばしば用いられる式である。

R is a gas constant (8.314 [J / (mol · K)]), and A, Q', C1 and C2 are constants determined by the material of the steel material 100. Regressing to the formula of JMAK (Johnson-Mehl-Avrami-Kolmogorov) using the predetermined inter-process time δ _0.5 , the softening ratio X of the steel material 100 can be expressed as in the formula 2. The JMAK formula is a formula often used when organizing experimental data on the correlation between temperature and time and the recrystallization rate.

ただし、所定工程間時間δは変数であり、ｐは鋼材１００の材料によって決まる定数である。

However, the time δ between predetermined steps is a variable, and p is a constant determined by the material of the steel material 100.

By using the above formulas 1 and 2, the softening rate of the steel material 100 of various materials can be calculated. The steel material 100 of the present embodiment has A = 9.7E-07 [sec], Q'= 141 [kJ / mol], C1 = 1.91 [no unit], and C2 = −0.27 [no unit]. ], P = 0.7 [no unit].

The constants A, Q', C1, C2, and p determined by the material of the steel material 100 change the predetermined strain amount ε, the first strain rate ε dot, the predetermined steel material temperature T, and the predetermined inter-process time δ, which are variables. It can be determined from the experimental results at the time.

If the constants determined by the materials are determined in advance by experiments, the inventors can use Equations 1 to 2 to obtain the desired softening rate X or more, which is the predetermined process time δ and the minimum required. I noticed that the required predetermined process temperature can be calculated. In the present embodiment, the softening ratio X is 0.9 or more as a criterion for determining that the work hardening generated in the first forging step is almost completely removed and the deformation resistance is softened to the limit achieved by recrystallization. The predetermined strain amount ε, the first strain rate ε dot, the predetermined inter-process time δ, and the predetermined steel material temperature T are controlled so as to be.

For example, as shown in FIG. 12, the softening rate X of the steel material 100 can be made 0.9 or more by setting the time δ between predetermined steps to 3 seconds or more.

The control unit 50 of the steel material forging device of the present embodiment specifies the material of the steel material 100 in the induction heating step S100 shown in FIG. Specifically, when the operator operates an operation unit (not shown) to input the material of the steel material 100, the operation unit notifies the control unit 50 of information indicating the material of the steel material 100. The control unit 50 specifies the material of the steel material 100 based on this information.

Further, the control unit 50 specifies constants A, Q', C1, C2, and p based on the material of the steel material 100. The memory of the control unit 50 stores the values of the constants A, Q', C1, C2, and p corresponding to the material of the steel material 100. The control unit 50 reads out each value stored in the memory and specifies the constants A, Q', C1, C2, and p.

Further, the control unit 50 uses Equations 1 and 2 to set a predetermined strain amount ε, a first strain rate ε dot, a predetermined inter-process time δ, and a predetermined steel material temperature T so that the softening ratio X becomes 0.9 or more. Identify.

In the first forging step S200, the control unit 50 presses the steel material 100 heated by the induction heating step of S100 against the first press machine 20 with a predetermined strain amount ε and a first strain rate ε dot. Instruct. Here, the first strain rate ε dot = V1. The first press machine 20 presses the steel material 100 with a predetermined strain amount ε and a first strain rate ε dot.

Further, in the transfer process S300, the control unit 50 transfers the steel material 100 taken out from the first press machine 20 to the second press machine 40 over a predetermined time δ while heating at the predetermined steel material temperature T. Instruct the transport unit 30. The transport unit 30 transports the steel material 100 taken out from the first press machine 20 to the second press machine 40 over a predetermined time δ while heating the steel material 100 at a predetermined steel material temperature T.

Further, in the second forging step S400, the control unit 50 transfers the steel material 100 conveyed by the transfer unit 30 to the second press machine 40 at a predetermined strain amount and at a strain rate higher than that of the first strain rate ε dot. Instruct to press at the second strain rate, which is a low speed. Here, it is preferable that the second strain rate ε dot = V2 <V1, and the deformation resistance in the second forging step can be further reduced. This is because there is a positive correlation between deformation resistance and strain rate in metal materials in general, regardless of the presence or absence of work hardening and the progress of recrystallization. It is also a feature of the present invention that recrystallization between steps can be taken to reduce the deformation resistance by reducing the strain rate in the second forging step. The second press machine 40 presses the steel material 100 at a predetermined strain amount and second strain rate. When the above-mentioned process is completed, the main forging process is completed.

As described above, in the present embodiment, the steel material 100 is formed by dividing into two forgings. The steel material 100 is heated in the induction heating furnace 10 and then pressed by the first press machine 20. Until the steel material 100 pressed by the first press machine 20 is conveyed to the second press machine 40. , The steel material 100 is held in a high temperature state. By sufficiently providing the predetermined inter-step time δ during this period, dislocations are restored in the steel material 100 and recrystallization is promoted, and the steel material 100 can be softened in the second forging step using the second press machine 40.

Further, the transport unit 30 heats the steel material 100 plastically deformed by the first press machine 20 at a temperature equal to or higher than the transformation point of the steel material 100. That is, the transport unit 30 heats the predetermined steel material temperature T at a temperature equal to or higher than the transformation point of the steel material 100.

By the way, conventionally, as shown in FIG. 13, the first forging step and the second forging step are carried out by one press machine. However, in such a configuration, the strain rates of the first forging step and the second forging step cannot be made different.

However, the steel forging device of the present embodiment includes a first press machine 20 and a second press machine 40. Therefore, the strain rate when forging the steel material 100 can be controlled separately.

In the present embodiment, the strain rate when the steel material 100 is forged by the second press machine 40 is set to be lower than the strain rate when the steel material 100 is forged by the first press machine 20. As a result, the deformation resistance of the steel material 100 can be reduced, and the deformation of the steel material 100 during the second forging step can be facilitated.

As described above, the steel material forging apparatus of the present embodiment includes a first press machine 20 that compresses and plastically deforms the steel material 100 at a predetermined strain amount and the first strain rate. In addition, a transport unit 30 is provided for transporting the steel material plastically deformed by the first press machine over a predetermined time between processes while keeping the temperature of the steel material above a predetermined temperature. Further, it is provided with a second press machine 40 that compresses and plastically deforms the steel material conveyed by the conveying unit at the second strain rate. Here, the predetermined strain amount is ε, the first strain rate is ε dot, the predetermined inter-process time is δ, and the predetermined steel material temperature is T, and A, Q', C1, C2, and p are determined by the material of the steel material. It is a constant to be determined.

The steel forging device controls a predetermined strain amount, a first strain rate, a predetermined inter-process time, and a predetermined steel material temperature so that the softening ratio X calculated by the above formulas 1 and 2 is 0.9 or more. The part 50 is provided.

According to this, the control unit controls a predetermined strain amount, a first strain rate, a predetermined inter-process time, and a predetermined steel material temperature so that the softening rate X calculated by Equations 1 and 2 is 0.9 or more. Therefore, the forging load required for forging can be reduced with various steel types.

Further, the transport unit 30 keeps the steel material 100 plastically deformed by the first press machine 20 at a predetermined steel material temperature equal to or higher than the transformation point of the steel material 100. As a result, recrystallization can be generated in a short time as compared with the case where the predetermined steel material temperature T is heated at a temperature lower than the transformation point of the steel material 100.

The second strain rate is lower than the first strain rate. As a result, the deformation resistance of the steel material 100 can be reduced, and the deformation of the steel material 100 during the second forging step can be facilitated.

Further, as described above, it can be regarded as a method for manufacturing the steel material 100. That is,
This includes compressing and plastically deforming a steel material with a predetermined strain amount and a first strain rate by a first press machine 20.

It also includes transporting the plastically deformed steel material to the second press machine 40 over a period of time between predetermined steps while keeping the temperature of the plastically deformed steel material above a predetermined steel material temperature.

It also includes compressing the conveyed steel material with a second press machine at a second strain rate to plastically deform it.

Here, the predetermined strain amount is ε, the first strain rate is ε dot, the predetermined inter-process time is δ, and the predetermined steel material temperature is T, and A, Q', C1, C2, and p are determined by the material of the steel material. It is a constant to be determined.

In the method for manufacturing the steel material 100, the predetermined strain amount, the first strain rate, the predetermined inter-process time, and the predetermined steel material temperature are controlled so that the softening ratio X calculated by the above formulas 1 to 2 is 0.9 or more. To.

(Other embodiments)
(1) In the above embodiment, the steel material 100 is deformed by dividing it into two forging steps, but the steel material 100 may be deformed by dividing it into three or more forging steps.

(2) In the above embodiment, an example in which a steel material 100 composed of steel containing carbon and manganese is pressed is shown, but the present invention is not limited to the steel material 100 made of such a material, and is newly developed, for example. It can also be applied to the press working of the steel material 100 composed of the new alloy.

The present invention is not limited to the above-described embodiment, and can be appropriately modified within the scope of the claims. Further, the above-described embodiments are not unrelated to each other, and can be appropriately combined unless the combination is clearly impossible. Further, in each of the above embodiments, it goes without saying that the elements constituting the embodiment are not necessarily essential except when it is clearly stated that they are essential and when they are clearly considered to be essential in principle. No. Further, in each of the above embodiments, when numerical values such as the number, numerical values, amounts, and ranges of the constituent elements of the embodiment are mentioned, when it is clearly stated that they are particularly essential, and in principle, the number is clearly limited to a specific number. It is not limited to the specific number except when it is done. Further, in each of the above embodiments, when referring to the material, shape, positional relationship, etc. of the constituent elements, etc., except when specifically specified or when the material, shape, positional relationship, etc. are limited to a specific material, shape, positional relationship, etc. in principle. , The material, shape, positional relationship, etc. are not limited.

10 Induction heating furnace 20 1st press machine 30 Transport unit 40 2nd press machine 50 Control unit 100 Steel material

Claims (4)

A first press machine (20) that compresses and plastically deforms a steel material (100) at a predetermined strain amount and first strain rate.
A transport unit (30) that transports the steel material plastically deformed by the first press machine over a predetermined time while keeping the steel material at a predetermined steel material temperature or higher.
A second press machine (40) that compresses and plastically deforms the steel material transported by the transport unit at a second strain rate.
Let R be the gas constant, A, Q', C1, C2, where the predetermined strain amount is ε, the first strain rate is ε dot, the predetermined inter-process time is δ, and the predetermined steel material temperature is T. When p is a constant determined by the material of the steel material,

A control unit that controls the predetermined strain amount, the first strain rate, the predetermined inter-process time, and the predetermined steel material temperature so that the softening rate (X) calculated by Equations 1 to 2 is 0.9 or more. 50) and a steel forging device. The steel forging device according to claim 1, wherein the transport unit keeps the steel material plastically deformed by the first press machine at a temperature equal to or higher than the predetermined steel material temperature equal to or higher than the transformation point of the steel material. The steel forging apparatus according to claim 1 or 2, wherein the second strain rate is lower than the first strain rate. The first press machine (20) compresses and plastically deforms the steel material at a predetermined strain amount and first strain rate.
The steel material plastically deformed by the plastic deformation is conveyed to the second press machine (40) over a predetermined time while keeping the temperature of the steel material above a predetermined temperature.
The conveyed steel material is compressed by the second press machine at a second strain rate to be plastically deformed.
Let R be the gas constant, A, Q', C1, C2, where the predetermined strain amount is ε, the first strain rate is ε dot, the predetermined inter-process time is δ, and the predetermined steel material temperature is T. When p is a constant determined by the material of the steel material,

A steel material whose predetermined strain amount, the first strain rate, the time between predetermined steps, and the predetermined steel material temperature are controlled so that the softening rate (X) calculated by the formulas 1 to 2 is 0.9 or more. Production method.

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