TW201348452A - Deformation processing method and deformation processing apparatus for metallic material - Google Patents

Abstract

A deformation processing method for a steel material which includes an austenite, the method including: identifying a predicted fracture point in case that the steel material is deformed; analyzing a strain ratio β x of the predicted fracture point; heating the steel material so that Tlocal satisfies a following Equation 1; and deforming the steel material after the heating, wherein T β x in celsius is a strain induced transformation maximum ductility temperature which depends on the strain ratio β x, σ L β x is a standard deviation of a critical equivalent strain fitted curve which depends on the strain ratio β x at lower temperature than T β x, σ H β x is a standard deviation of a critical equivalent strain fitted curve which depends on the strain ratio β x at higher temperature than T β x, and Tlocal in celsius is a local temperature of the predicted fracture point. T β x-2* σ L β x ≤ Tlocal ≤ Tβ x+1.25* σ H<sub> β x...(Equation 1)

Description

Plastic processing method for metal material and plastic processing device Field of invention

The present invention relates to a plastic working method and a plastic working apparatus for suppressing the occurrence of diameter reduction and fracture while forming a steel material containing Vostian iron.

Background of the invention

To date, various plastic processing methods have been proposed which can improve the formability of steel. For example, in the plastic working method disclosed in Patent Document 1, first, before the press forming of the steel material, the steel material is preheated by a heating furnace or the like to a temperature of 750 ° C to 1000 ° C in the field of the single phase of the Worthite iron. ₃ or more points. Further, the steel material in the single-phase state of the Worstian iron is subjected to press forming, and the steel material is quenched and quenched by heat transfer of the steel material to the mold to produce a press-molded product having high strength and good dimensional accuracy.

Further, the plastic working method disclosed in Patent Document 2 heats the die of the mold, cools the punch of the mold, and simultaneously draws the steel material containing the Worthite iron. Thereby, after the forming, the heat of the die can be heated to heat the portion of the steel as the flange portion to reduce the deformation resistance, and the heat transfer between the punches is used to cool the rest of the steel to increase the The deformation resistance is drawn and drawn. Therefore, drawing can be performed to avoid wrinkles and breakage.

Further, the plastic working method disclosed in Patent Document 3 controls the metal structure of the material to be processed as a steel material so that the toughened ferrite iron and/or the granular tough ferrite iron account for 70% or more as a space factor. The mother phase, and the remaining Worthite iron is 5% or more and 30% or less as the second organization, and the above-mentioned residual Worthite iron The C concentration is 1.0% by mass or more. Thereby, the total elongation value of the above steel material at 7% at room temperature is 20% at 250 ° C, and the formability at this temperature is improved.

With these conventional techniques, it is indeed possible to improve the formability of steel containing Vostian Iron. However, at present, the shape of the part has become complicated and thinned, and further improvement in formability is required.

[First technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2005-177805

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2007-111765

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2004-190050

Summary of invention

The present invention has been made in view of the above problems, and an object of the present invention is to provide a plastic working method and a plastic working apparatus which can improve the formability by using a steel material containing Worthite iron as a material to be processed and suppressing occurrence of shrinkage and fracture.

The gist of the present invention is as follows.

(1) The aspect of the present invention is a plastic working method of a steel containing Worthite iron, which comprises the following steps: a physical property analysis step, in which T _β (unit ° C) represents a change in the steel material affected by the strain ratio β processing-induced abnormal temperature ductility greatly to σL _β T _β representative of the more lower temperature side than the ultimate strain by the impact of a considerable strain beta] standard deviation of the approximate curve, by the higher temperature side than the representative of the σH _β to T _β the When the strain ratio β is the limit of the standard deviation of the strain approximation curve, the aforementioned T _β , the σL _β , and the σH _{β are} measured for each of the strain ratios _β ; the deformation form analysis step defines the predicted fracture site when the steel material is plastically deformed. When βx represents the strain ratio of the predicted fracture site, the strain ratio βx is analyzed, and then the strain ratio βx is selected from the strain ratio β; and the heating step represents _Tβx (unit °C) corresponding to the strain ratio βx. The processing-induced metamorphic maximum temperature, σL _βx represents the ultimate strain approximation curve affected by the aforementioned strain ratio βx on the lower temperature side of the aforementioned T _βx The standard deviation, where σH _βx represents the standard deviation of the limit equivalent strain approximation curve affected by the aforementioned strain ratio βx on the higher temperature side of the aforementioned T _βx , and T _local (unit ° C) represents the local temperature of the predicted fracture site, respectively selected from the aforementioned _T β _T βx, selected from the foregoing _σL β _σL βx, selected from the foregoing _σH β _σH βx, then, so that the local temperature T _local at the first of the formula shown in FIG. 1 temperature Heating in a range of manners; and processing steps to plastically deform the steel material after the heating step.

T _βx -2 × σL _βx ≦T _local ≦T _βx +1.25×σH _βx (1)

(2) In the plastic working method disclosed in the above (1), the deformation may be represented by ΔT _local (unit ° C) representing a temperature change of the local temperature T _local changed during plastic deformation of the processing step. The form analysis step further analyzes the temperature change ΔT _local , and the heating step is performed such that the partial temperature T _{local is} within the second temperature range shown by the following formula 2 .

T _{βx -ΔT local} -2 × σL _βx ≦T _local ≦T _βx -ΔT _local +1.25×σH _βx (...)

(3) The plastic working method disclosed in (1) or (2) above, wherein the heating step may heat the steel material, the mold, or the method such that the partial temperature _{Tlocal is} within the first temperature range. At least one of the spaces surrounding the steel material.

(4) The plastic working method according to (1) or (2) above, wherein the heating step is heating the heat medium such that the partial temperature T _{local is} within the first temperature range, and the processing step The steel material is plastically deformed by the pressure of the heat medium.

(5) The plastic working method disclosed in any one of (1) to (4) above, wherein the deformation form analysis step is characterized in that the predicted fracture site, the strain ratio βx, and the foregoing are analyzed by a plastic working simulation Temperature change △T _local .

(6) A plastic working apparatus for performing the plastic working method disclosed in any one of the above (1) to (3) or (5), comprising: a housing portion for accommodating the steel material and the mold The heating unit may heat at least one of the steel material, the mold or the space around the steel material, and the processing portion may plastically deform the steel material heated by the heating unit by the mold.

(7) The plastic working apparatus disclosed in the above (6) may further include a heat insulating member disposed to cover the storage portion.

(8) The plastic working apparatus disclosed in the above (6) or (7), further comprising a temperature measuring unit for measuring a temperature of the steel material, the mold, and a space in the housing portion.

(9) A plastic working apparatus for performing the plastic working method disclosed in any one of the above (1), (2), (4) or (5), comprising: a housing portion, which can be housed The steel material and the mold; the heat medium introduction unit may introduce the heat medium into the mold; and the heating unit may heat at least one of the steel material, the mold, the space surrounding the steel material, or the heat medium; and The working part can plastically deform the steel material heated by the heating portion by the pressure of the heat medium.

(10) The plastic working apparatus disclosed in the above (9) may further include a heat insulating member disposed to cover the storage portion.

(11) The plastic working apparatus disclosed in (9) or (10) above, further comprising a temperature measuring unit for measuring a temperature of the steel material, the mold, the space in the housing portion, and the temperature of the heat medium.

According to the above aspect of the present invention, in the plastic deformation of the steel containing the Worthite iron, the plastic working is performed in a temperature range including the strain ratio corresponding to the predicted fracture point of the steel material, and the processing-induced metamorphic maximum temperature. Therefore, the metamorphism-induced plasticity phenomenon exhibited by the aforementioned steel can be applied to the maximum extent. As a result, it is possible to provide a plastic working method and a plastic working apparatus which can suppress the occurrence of shrinkage and breakage and improve the formability.

Simple illustration

Figure 1 is a schematic diagram showing the phenomenon of abnormal induced plasticity.

Fig. 2 is a schematic view showing uniaxial stretching, plane strain stretching, and isotropic biaxial stretching.

Fig. 3 is a graph showing the temperature dependence of the strain of each strain ratio of the low carbon steel.

Fig. 4 is a graph showing an approximation of the normal distribution of the ultimate strain temperature dependence of β = 0 in Fig. 3.

Fig. 5 is a partially cutaway front view showing the schematic structure of a plastic working apparatus according to an embodiment of the present invention.

Fig. 6 is a partially cutaway front elevational view showing the schematic structure of a plastic working apparatus according to another embodiment of the present invention.

Figure 7 is a schematic view showing the processing of the square tube drawing.

Form for implementing the invention

Hereinafter, the plastic working method and the plastic working apparatus according to the embodiment of the present invention will be described in detail. However, the present invention is not limited to the embodiments described below, and various modifications can be made without departing from the spirit and scope of the invention.

First, a plastic working method according to an embodiment of the present invention will be described. In the plastic working method of the present embodiment, a steel material containing Vostian iron is used as a material to be processed, and the deformation-induced plasticity phenomenon exhibited by the steel material is applied to the maximum extent.

Here, the transformation induced plasticity phenomenon (TRIP phenomenon) will be described. Figure 1 is a schematic diagram showing the TRIP phenomenon. As shown in Fig. 1, when the steel containing the Worthite iron (TRIP steel) is subjected to tensile deformation, for example, after a certain degree of deformation, the diameter reduction phenomenon occurs. When the diameter reduction occurs, the stress acting on the reduced diameter portion is enhanced, and the residual Worstian iron metamorphosis is caused by the stress-induced metamorphosis of the granulated iron (shown as A in Fig. 1). Compared with other microstructures, the Ma Tian loose iron has higher strength, so the reduced diameter portion is strengthened more than other parts due to the processing induced metamorphosis, and the deformation of the reduced diameter portion is prevented. As a result, the portion having a relatively low strength near the reduced diameter portion continues to be deformed. As described above, the phenomenon of the occurrence of the reduction of the diameter caused by the processing-induced metamorphism and the suppression of the deformation is called the allergy-induced plastic phenomenon (TRIP phenomenon). Thereby, it can be deformed evenly within the material, and Excellent extensibility.

However, the above-mentioned TRIP phenomenon has a temperature dependence. The increase in ductility caused by the above TRIP phenomenon (process induced metamorphosis) is only manifested in a specific temperature range. Moreover, the temperature at which the TRIP phenomenon (process-induced metamorphism) maximizes ductility (hereinafter referred to as the process-induced metamorphic maximum temperature) is affected by the chemical composition and metal structure of the above-mentioned TRIP steel. Further, as a result of intensive review by the present inventors, it has been confirmed that the above-described processing-induced metamorphic maximum temperature also has a strain ratio β (plastic deformation) which is affected by plastic deformation and changes its strain ratio β (plasticity) Deformation form correlation).

Here, the strain ratio β is represented by β = ε ₂ ÷ ε ₁ when the strain in the two-axis direction in the two-axis stress state is set to the maximum principal strain ε ₁ and the minimum principal strain ε ₂ , respectively. However, ε ₁ ≧ ε ₂ . In particular, a state of β=-0.5 is referred to as a uniaxially stretched state, a state of β=0 is referred to as a plane strain tensile state, and a state of β=1.0 is referred to as an isotropic biaxial stretching state. Fig. 2 is a schematic view showing uniaxial stretching, plane strain stretching, and isotropic biaxial stretching. As illustrated in FIG. 2, β = -0.5 uniaxial means extending toward the _direction shown in FIG stretching ε, ε toward the _second direction is shortened form of modification, which corresponds to the plastic working such as drawing. β = 0 the plane strain stretch extending towards the [epsilon] refers to the direction shown in FIG. _1, the deformation mode of the deformation [epsilon] not occurred _in the _second direction, bending and other plastic working which corresponds. The isotropic biaxial stretching of β = 1.0 means a deformation form extending in the ε ₁ direction and extending in the ε ₂ direction as shown in the drawing, and corresponds to plastic working such as stretch forming.

In order to effectively apply the TRIP phenomenon to enhance the plastic deformation ability, it is necessary to simultaneously consider the maximum temperature of the processing-induced metamorphic ductility for each of the various steels, and the strain ratio β for the plastic deformation of the above-mentioned processing-induced metamorphic maximum temperature. Both sides of the (plastic deformation form). However, the above-mentioned prior art does not take the above considerations. In addition, the processing-induced metamorphic maximum temperature system is affected by the strain ratio β, so the processing-induced metamorphic maximum temperature is denoted as _Tβ . For example, when the strain ratio is β=-0.5, the processing-induced metamorphic maximum temperature is recorded as T _-0.5 .

Figure 3 shows the temperature dependence of the ultimate strain ε _{eq-critical for} each strain ratio β obtained from a low carbon steel survey. In Fig. 3, the four-cornered mark and the broken line represent the result of β = -0.5, the △ mark and the two-dot chain line represent the result of β = 0, and the circular mark and the solid line represent the result of β = 1.0. Further, the strain ε _eq is a strain calculated by the following formula A when the strain in the two-axis direction in the two-axis stress state is the maximum principal strain ε ₁ and the minimum principal strain ε ₂ , respectively. The above-described equivalent strain ε _{eq is} obtained by converting the stress-strain component in the multiaxial stress state into a uniaxial stress-strain equivalent thereto. The above-mentioned equivalent strain ε _eq is used to compare the plastic deformation ability (ductility) of different plastic deformation forms, that is, different strain ratios β. Secondly, the limit equivalent strain ε _eq-critical refers to the equivalent strain ε _eq when the steel material to be processed is broken.

ε _eq = {4 ÷ 3 × ( ε ₁ ² + ε ₂ ² + ε ₁ ε ₂ )} ^1/2 ... (Formula A)

As shown in Figure 3, the value of the limit equivalent strain ε _eq-critical (extensibility) increases over a specific temperature range. As mentioned above, the increase in ductility is due to the TRIP phenomenon. Thus, the increase in ductility due to the TRIP phenomenon is temperature dependent. For example, when β=-0.5, the processing-induced metamorphic maximum temperature T _-0.5 is 150 ° C, and the limit equivalent strain ε _eq-critical is the maximum at this temperature.

Moreover, Fig. 3 shows that the processing induced metamorphic ductility maximum temperature _{Tβ is} affected by the strain ratio β. For example, as described above, when β = -0.5, the processing-induced metamorphic maximum temperature T _-0.5 is 150 ° C, but when β = 0, the processing induced metamorphic maximum temperature T ₀ is 200 ° C, β When =0, the processing induced metamorphic ductility maximum temperature T _1.0 is 250 °C. As described above, the processing-induced metamorphic maximum temperature _Tβ has a strain ratio β correlation.

In Fig. 4, the two-point chain line represents the temperature dependence of the limit equivalent strain ε _eq-critical of β = 0 in Fig. 3, and the broken line represents the approximate curve when it is assumed to conform to the normal distribution curve. As described above, when the strain ratio β = 0, the temperature at which the limit equivalent strain ε _eq-critical is most enhanced by the TRIP phenomenon is 200 ° C of the processing-induced metamorphic maximum temperature T ₀ . However, as shown in Fig. 4, the temperature at which the limit equivalent strain ε _{eq-critical is} raised has a specific range. The temperature range in which the above-described limit equivalent strain ε _{eq-critical is} increased can be obtained from the assumption that the assumption shown by the broken line in Fig. 4 conforms to the approximate curve of the normal distribution curve.

Hereinafter, a method of obtaining the temperature range in which the limit is equivalent to the strain ε _eq-critical by the TRIP phenomenon from the approximate curve (approximation function) will be described. First, assume that the temperature dependence of the limit equivalent strain ε _eq-critical conforms to the normal distribution curve, and the above temperature dependence is close to the probability density function shown by Equation B and Equation C below. Here, of the following Formula B, the strain ratio beta], and which represents the ultimate cause rather than the lifting of the most processing strain ε _eq-critical temperatures induce abnormal temperature _T β ductility greatly lower temperature limit of the quite side strain ε _eq the correlation of temperature _-critical approximation function (strained lower temperature side than the limit beta] Effect of T _β ratio of approximately considerable strain curve). In the following formula C, the strain ratio is β, and it represents the limit-equivalent strain ε _{eq-critical of the} higher temperature side of the processing-induced metamorphic maximum temperature T _{β which} is the temperature at which the limit is equivalent to the strain ε _eq-critical . the temperature dependence of the approximation function (the higher temperature side than the strained than T _β beta] influence of considerable strain limit curve approximation). In addition, in Equations B and C, ε _eq-critical : ultimate strain, T: temperature, T _β : processing induced metamorphic maximum temperature, σL _β : the limit of the strain ratio β on the lower temperature side of T _β The standard deviation of the approximate strain approximation curve, σH _β : the standard deviation of the strain-to-strain approximation curve affected by the strain ratio β on the higher temperature side of T _β , e: natural logarithm, π: pi, C ₁ ~ C ₄ : constant.

If the mathematical definition of the probability density function is taken into consideration, the temperature range in which the limit equivalent strain ε _{eq-critical is} increased by the TRIP phenomenon can be represented by the above-mentioned σL _β and σH _β . That is, the above temperature range can be described as (T _β -3 × σL _β ) ~ (T _β + 3 × σH _β ), (T _β - 2 × σL _β ) ~ (T _β + 2 × σH _β ) or ( T _β -σL _β )~(T _β +σH _β ) and the like. Here, mathematically means that when the above range is (T _β -3 × σL _β )~(T _β +3 × σH _β ), the integral value of the probability density function is 0.9974, and the above range is (T _β -2 × σL) _{When β} )~(T _β +2×σH _β ), the integral value of the probability density function is 0.9544, and the integral of the probability density function when the above range is (T _β -σL _β )~(T _β +σH _β ) The value is 0.6826.

As described above, the temperature range in which the limit equivalent strain ε _{eq-critical is} increased by the TRIP phenomenon can be assumed to be represented by σL _β and σH _β of the standard deviation of the approximate curve (limit equivalent strain approximation curve) of the normal distribution curve. These σL _β and σH _β are influenced by the strain ratio β. Hereinafter, the σL _β and σH _β will be referred to as σL ₀ and σH ₀ when the strain ratio is β = 0, for example. When the strain ratio shown in Fig. 4 is β = 0, the processing-induced metamorphic maximum temperature T ₀ is 200 ° C, and the analytical result of the approximate curve shows that σL ₀ is 55 ° C and σH ₀ is 19 ° C. In addition, the analysis of the approximate curve for obtaining σL _β and σH _β can be performed by a spreadsheet software having general data analysis, graph creation software, and general chart creation functions.

In Fig. 4, for example, the temperature range in which the limit equivalent strain ε _{eq-critical is} increased by the TRIP phenomenon can be expressed as 35 when (T ₀ -3 × σL ₀ )~(T ₀ +3×σH ₀ ) °C~257°C, from 90°C to 238°C at (T ₀ -2×σL ₀ )~(T ₀ +2×σH ₀ ), or at (T ₀ -σL ₀ )~(T ₀ +σH ₀ ) is 145 ° C ~ 219 ° C and so on. However, the inventors of the present invention conducted a review of various steel materials and various strain ratios, and confirmed that it is appropriate to adopt a temperature range of (T _β -2 × σL _β ) to (T _β + 1.25 × σH _β ). _Determine the temperature range by which the limit is equivalent to ε _eq-critical by the TRIP phenomenon, without being too large or too small. Therefore, in the plastic working method of the present embodiment, the temperature range in which the extreme strain ε _eq-critical is raised by the TRIP phenomenon is (T _β - 2 × σL _β ) ~ (T _β + 1.25 × σH _β ). Further, the lower limit of the above temperature range may be set to (T _{β -} 1.75 × σL _β ), (T _{β -} 1.5 × σL _β ) or (T _{β -} 1.25 × σL _β ) as needed. Similarly, the upper limit of the above temperature range may be (T _β +1.20 × σH _β ), (T _β + 1.15 × σH _β ) or (T _β - 1.10 × σL _β ).

When the strain ratio is β=0, and the temperature range is (T ₀ -2×σL ₀ )~(T ₀ +1.25×σH ₀ ), the temperature range of the equivalent strain ε _eq-critical is increased by the TRIP phenomenon. 90 ° C ~ 223.75 ° C. That is, it is understood that when the above-mentioned low carbon steel is used, the plastic deformation ability can be improved by the plastic deformation form of the strain ratio β = 0, and plastic working can be performed in the temperature range of 90 ° C to 223.75 ° C.

As described above, in order to form the steel material by using a steel material (TRIP steel) containing Worthite iron and to minimize the diameter reduction and fracture, the following plastic working method can be employed. It is possible to (1) pre-measure the process-induced metamorphic maximum temperature T _β of each strain ratio β of the steel material to be processed, and the limit equivalent strain approximation curve of the strain ratio β on the low temperature side based on the above T _β . The standard deviation σL _β , the standard deviation σH _β of the ultimate strain approximation curve affected by the strain ratio β on the high temperature side based on the above T _β , (2) predefining the steel that is most prone to shrinkage and fracture during forming The plastic deformation form of the local domain, that is, the strain ratio βx of the above-mentioned local domain, (3) controlling the temperature of the above-mentioned local domain to a temperature range suitable for the strain ratio βx (T _βx - 2 × σL _βx ) ~ (T _βx Within +1.25 × σH _βx ), and (4) plastic working is performed under the conditions that the temperature of the above-mentioned partial field is within the above temperature range. Here, the representative βx strain ratio β = x, T _βx represents a strain inducing abnormal ductile than β = maximum temperature of the processing time of x, T _βx representative of σL _βx in reference to the influence of the low-temperature side strained ratio βx The limit is the standard deviation of the strain approximation curve, and σH _βx represents the standard deviation of the limit equivalent strain approximation curve affected by the strain ratio βx on the high temperature side based on T _βx . Further, T _βx , σL _{βx ,} and σH _βx are values included in T _β , σL _{β ,} and σH _β measured in advance for each strain ratio β. Therefore, T _βx , σL _{βx ,} and σH _βx are the same as the measurement and analysis methods of T _β , σL _{β ,} and σH _β .

Specifically, the plastic working method according to the present embodiment uses a steel material containing Worthite iron as a material to be processed, and includes the following steps: a physical property analysis step in which T _β (unit ° C) represents a change in the strain ratio β. the processing of steel ductility significantly induce abnormal temperature T _β, to σL _β representing said strain limit than beta] Effects of strain rather than the standard deviation of the approximated curve by lower temperature side of the above T _β, to σH _β representative of a higher temperature than the above T _β When the side is subjected to the standard deviation of the limit-strain approximate curve affected by the strain ratio β, the above-described strain ratio β is measured for the above-mentioned T _β , the above-mentioned σL _β , and the above-mentioned σH _β ; and the deformation form analysis step is used to define the plastic deformation of the steel material. The predicted fracture site, when βx represents the strain ratio of the predicted fracture site, analyzes the strain ratio βx, and selects the strain ratio βx from the strain ratio β; and the heating step represents the strain ratio by T _βx (unit ° C) the corresponding work-induced abnormal βx maximum ductility temperature T _β, to σL _βx than by the foregoing representative of the lower temperature side than the strain T _βx βx Movies The ultimate considerable strain standard approximate curve of the deviation to the σH _βx both represent by the above the higher temperature side of the T _βx the strain ratio limit βx Effect of considerable strain approximate standard deviation curve of order T _local (unit ℃) representative of the predicted cleavage site when the local temperature, respectively, from above _T β selected from the above-described _T βx, from said _σL β selected from the above-described _σL βx, from said _σH β selected from the above-described _σH βx, and so that the local temperature T _local below the formula D in Heating is performed in a manner shown in the first temperature range; and the processing step is to plastically deform the steel material after the heating step.

T _βx -2 × σL _βx ≦T _local ≦T _βx +1.25×σH _βx ... (Formula D)

In the physical property analysis step described above, the processing-induced metamorphic maximum temperature T _β of each strain ratio β can be measured by using the steel material as the material to be processed. The method for measuring the processing-induced metamorphic maximum temperature _Tβ is not particularly limited, and the longitudinal and transverse dimensions of the test piece can be changed, and a spherical stretch forming test for fixing the end of the test piece can be carried out at each temperature. Next, the temperature at which the limit equivalent strain ε _eq-critical (extension) is most improved is set as the processing-induced metamorphic maximum temperature T _{β of} the strain ratio β described above. Then, for each of the strain ratio by the above-described approximation curve is determined by parsing the strain of the lower temperature side than the above T _β rather than limit beta] Effects of strain curve of the approximated standard deviation, and more strained than the higher temperature side of the above T _β The limit of the beta effect is the standard deviation of the strain approximation curve.

In the above-mentioned deformation form analysis step, the local area (predicted fracture site) where the steel material is most likely to undergo shrinkage and fracture at the time of plastic deformation of the steel material can be defined, and the strain ratio βx is defined as the plastic deformation form of the local field. Next, the above strain ratio βx is selected from the strain ratio β measured in the above physical property analysis step. The method for measuring the strain ratio βx of the fracture site and the portion is not particularly limited, and plastic mesh measurement can be performed. The so-called plastic mesh measurement is to draw a circular pattern or a lattice pattern on the surface of the material to be processed before processing, and define a partial field (predicted fracture site) which is susceptible to plastic deformation and which is reduced in diameter and fracture, and then measured. The above-described pattern shape of the partial field, and a method of defining the plastic deformation form (strain ratio βx) of the local field. As a result of the plastic grid measurement, the plastic deformation form of the local domain can be classified into uniaxial stretching (β=-0.5), drawing field (-0.5<β<0), plane strain stretching (β=0). ), stretching field (0 < β < 1.0) and isotropic biaxial stretching (β = 1.0).

As described above, the measured fracture ratio and the strain ratio βx of the portion can be analyzed by actual measurement. However, other analytical methods for the above-described deformation form analysis step can also be simulated by the finite element method. At this time, it is possible to use a plastic deformation simulation program for a computer that is sold in the market. When the plastic deformation simulation is used, even if the inside of the material to be processed which is difficult to measure is the predicted fracture site, the definition of the fracture location and the strain ratio βx of the portion can be analyzed. Secondly, the appropriateness of the above simulation results can only be confirmed by experiments, so the fracture site and the part can be predicted by the least number of tests. The strain ratio of the bit is βx.

In the above heating step, temperature control may be performed such that the local temperature T _local of the predicted fracture site of the steel is within the temperature range of the strain ratio βx of the corresponding portion (T _βx -2 × σL _βx )~(T _βx +1.25 ×σH _βx ). As described above, the temperature range may be (T _βx - 3 × σL _βx ) ~ (T _βx + 3 × σH _βx ) or (T _βx - 2 × σL _βx ) ~ (T _βx + 2 × σH _βx ), However, in the plastic working method of the present embodiment, (T _βx - 2 × σL _βx ) - (T _βx + 1.25 × σH _βx ) is used as the first temperature range in which the plastic deformation ability can be improved. In order to appropriately obtain the effect of improving the ductility, the first temperature range may be set to be, for example, (T _βx -σL _βx )~(T _βx +σH _βx ) or (T _βx -0.5×σL _βx )~(T _βx ) as _needed. +0.5 × σH _βx ) and the like.

In order to obtain a better ductility improvement effect, in the above-described deformation form analysis step, the local temperature T _local of the predicted fracture site which is changed by heat exchange or processing heat generation during plastic working may be analyzed in advance according to the unit °C. Temperature change ΔT _local , and then in the heating step described above, temperature control is performed such that the local temperature T _{local is} within the second temperature range indicated by the formula E below the temperature change ΔT _local has been considered, instead of the above The first temperature range shown by Formula D.

T _{βx -ΔT local} -2 × σL _βx ≦T _local ≦T _βx -ΔT _local +1.25×σH _βx (...E)

As described above, considerations of the local temperature T _local temperature of the steel during heat exchange due to plastic working or machining heat-like change of change △ T _local, of the following effects induced available. For example, in the plastic working with a slower strain rate, even when the plastic working at the beginning of the plastic working is reduced with the steel and the plastic processing at the end of the fracture, the temperature of the steel material changes greatly, and the plastic working at the end of the plastic forming ability is most needed. The local temperature T _{local of the} predicted fracture site is controlled within a temperature range in which the ductility improvement effect can be obtained. Or, for example, even if the plastic working with a faster strain rate cannot ignore the influence of the heat of processing, the local temperature T _local can be controlled within a temperature range in which the ductility improving effect can be obtained. In order to obtain the best ductility improvement effect, the second temperature range may be set to (T _βx - ΔT _{local -} σL _βx ) to (T _βx - ΔT _local + σH _βx ) or (T _βx ) as needed. - ΔT _local - 0.5 × σL _βx ) ~ (T _βx - ΔT _local + 0.5 × σH _βx ) and the like.

The analysis of the temperature change ΔT _{local in} the above-described deformation form analysis step can be performed by mounting a thermocouple or the like at the predicted fracture site and actually measuring the local temperature T _local of the predicted fracture site at the time of plastic deformation. Alternatively, the temperature change ΔT _{local may} be analyzed in addition to the analysis of the strain ratio βx of the predicted fracture site and the portion using the plastic deformation simulation of the finite element method described above.

In the above heating step, at least one of the surrounding space of the steel material, the mold or the steel material is preferably heated so that the local temperature T _{local of} the predicted fracture site is within the first temperature range or the second temperature at which the ductility improving effect can be obtained. Within the scope. For example, in the deformation form analysis step, it is confirmed that there is a plurality of portions at the predicted fracture site, and when it is confirmed that the strain ratio β is different between the predicted fracture portions of the plurality of plural, it is preferable to heat the steel material, the mold, or the heating step in the above heating step. At least one of the surrounding spaces of the steel material is subjected to temperature control so that the individual temperature of the predicted fracture portion existing in the plural is within the first temperature range or the second temperature range to which the strain ratio β is applied. As a result, the ductility improvement effect of the corresponding portion can be obtained in each of the plurality of predicted fracture sites. Further, in the heating step, at least one of the space around the steel material, the mold, or the steel material may be cooled as needed.

In the above processing step, the steel having been subjected to the temperature control in the heating step to cause the local temperature T _{local of the} predicted fracture site to be plastically processed into the target in the first temperature range or the second temperature range in which the ductility improving effect is obtained is achieved. The shape is sufficient, and the plastic working method is not particularly limited. The plastic working method can be free forging, die forging, press working using a mold, and the like.

Further, in the heating step described above, an oil such as oyster oil, air or a heat medium such as a blower gas, a water vapor mist or an oil mist may be heated so that the local temperature T _{local of} the predicted fracture portion is within the first temperature range or the second In the temperature range, then, in the above processing step, the steel material as the workpiece is plastically deformed by the pressure of the heat medium. As a result, it is possible to obtain the effect of delaying the occurrence of fracture and improving the formability, uniformly heating the plastic deformation portion of the material to be processed, and heating in a state where the plastic deformation is more uniform.

The plastic working method of the present embodiment described above can be summarized as follows.

(1) The present embodiment is a plastic working method using a steel material containing Vostian iron as a material to be processed, and includes the following steps: a physical property analysis step in which T _β (unit ° C) represents a change in strain ratio β; the steel material of the stress-induced abnormal temperature ductility greatly to σL _β representative of the strain rather than the ultimate strain beta] influence of the standard deviation of the approximate curve than by the foregoing lower temperature side of T _β to σH _β representative of a higher temperature than the above T _β side When the standard deviation of the approximate strain approximation curve affected by the strain ratio β is measured, the T _β , the σL _β , and the σH _{β are} measured for each strain ratio _β ; and the deformation form analysis step is to define the plastic deformation of the steel material. In the predicted fracture site, when β1 represents the strain ratio of the predicted fracture site as βx, the strain ratio βx is analyzed, and then the strain ratio βx is selected from the strain ratio β; and the heating step is _Tβx (unit °C) ) represents the ratio of the strain corresponding to the stress-induced abnormal βx maximum ductility temperature ,, representatives to σL _βx lower temperature than the above-mentioned receiving side of the strain T _βx ratio βx The limit of influence is the standard deviation of the strain approximation curve, σH _βx represents the standard deviation of the limit equivalent strain approximation curve affected by the above strain ratio βx on the higher temperature side of the above T _βx , and the above predicted fracture is represented by T _local (unit ° C) when the local temperature of the portion of, respectively, from above _T β selected from the above-described _T βx, from said _σL β selected from the above-described _σL βx, from said _σH β selected from the above-described _σH βx, then, so that the local temperature T _local formula D in Heating is performed in a manner shown in the first temperature range; and the processing step is to plastically deform the steel material after the heating step.

(2) Then, when ΔT _local (unit ° C) represents the temperature change of the local temperature T _local changed in the plastic deformation of the processing step, the deformation form analysis step further analyzes the temperature change ΔT _local, said heating step so that the local temperature T _local heating in the temperature range of the first embodiment shown in FIG. 2 of the above-described formula E.

(3) Secondly, in the heating step, the local temperature T _local may be heated in the space around the steel material, the mold, or the steel material so that the local temperature T _{local is} within the first temperature range or the second temperature range. At least one of them.

(4) Thereafter, the heating step may be such that the heat medium is heated such that the partial temperature T _{local is} within the first temperature range or the second temperature range, and the processing step is performed by the pressure of the heat medium. The steel is plastically deformed.

(5) Then, the deformation form analysis step may analyze the predicted fracture site and the strain ratio βx by a plastic working simulation. Further, the temperature change ΔT _local can be analyzed by plastic working simulation.

Hereinafter, a plastic working apparatus according to an embodiment of the present invention will be described.

[First Embodiment]

A plastic working apparatus according to a first embodiment of the present invention will be described below. Fig. 5 is a partially cutaway front view showing a schematic structure of a plastic working apparatus according to a first embodiment of the present invention.

The structure of the processed portion of the plastic working device 1 of the present embodiment will be described below. The main body frame 11 is attached to each of the components of the plastic working device 1 for constituting a group of the molds 21, etc., and the inner lower portion is provided with a socket 12, and the inner upper portion thereof is provided with a slider 13. The slider 13 is configured to be driven in the vertical direction by a slider driving device 14 such as a motor or a cylinder disposed on the upper portion of the main body frame 11. The slider 13 is mounted with an upper die 21 underneath, and the carrier 12 has a lower die 21 mounted thereon. Thereby, the plastic working apparatus 1 is configured such that the main body frame 11 is attached with a set of the molds 21 arranged to face each other, and the plastic processing of the workpiece 3 can be performed between the set of the molds 21 by the slider 13 moving up and down. . As described above, if the plastic working of the workpiece 3 can be performed by a set of the molds 21, the structure of the main body frame 11 of the plastic working apparatus 1 or the like is not particularly limited.

One set of the molds 21 is used for plastic working such as bending, drawing, flange forming, burring, and drawing processing of the workpiece 3 disposed between the two, and can correspond to the type of plastic working and The shape of the molded article is adjusted to its shape, and a known structure is employed. A set of the molds 21 is configured to drive the upper mold 21, and the convex portion 21b of the upper mold 21 feeds the workpiece 3 placed on the lower mold 21 into the concave portion 21a provided in the lower mold 21, The bending process is performed on the material 3 to be processed. A set of molds 21 may also be provided with a press plate such as that used for drawing. A set of molds 21 can also be formed on the upper mold 21 and Both of the lower molds 21 are provided with concave portions 21a, and the workpiece 3 can be swaged.

The plastic working apparatus 1 of the present embodiment includes a heater 31 capable of heating an environment including a workpiece 3 and a group of molds 21, and a heater 32 capable of heating a group of molds 21 as a heating unit. Further, the heating unit includes a heating furnace 33 that is disposed outside the plastic working apparatus 1 and that can heat the workpiece 3. The plastic working device 1 may also include at least one of the heater 31, the heater 32, and the heating furnace 33. The structure including the heater 31 can be heated to deliberately make the temperature difference between the workpiece 3 and the space 16 small or to make the temperature difference large to heat the environment in the space 16 by the heater 31. The structure including the heater 32 can be heated to deliberately make the temperature difference between the workpiece 3 and the mold 21 small or to make the temperature difference large to heat the set of the molds 21 by the heater 32. The structure including the heating furnace 33 can control the temperature of the workpiece 3 to a target temperature before being fed into the space 16 of the plastic working apparatus 1. As described above, at least one of the heater 31, the heater 32, or the heating furnace 33 is used, and even if the plurality of predicted fracture sites are present in the workpiece 3, the plurality of predicted fracture sites may be individually controlled to correspond to the portions thereof. temperature. Further, the heating unit may cool at least one of the workpiece 3, the mold 21, or the space 16 as needed.

Further, the plastic working device 1 further includes a cover 41 (warm cover, heat insulating member) disposed to cover the space 16. The space 16 covered by the cover 41 is used as a housing for housing the workpiece 3.

The heater 31 heats the environment in the space 16 including the workpiece 3 and the set of the molds 21. The heater 32 heats the mold 21 to heat the predicted fracture portion of the workpiece 3 to the first temperature range or The second temperature range is sufficient. Therefore, the position and structure thereof are not particularly limited, and may be constituted by, for example, an induction heating coil, a burner, or the like in addition to the electric heater. The heater 31 is attached to the inside of the mold 21 such as the above-described body frame 11 mounter. Further, the heater 31, the heater 32, and the heating furnace 33 may be provided with a cooling function of cooling to a temperature lower than room temperature as needed. In this case, even if the processing-induced metamorphic maximum temperature T _{β of} the workpiece 3 is less than room temperature, the temperature of the predicted fracture portion of the workpiece 3 can be controlled to the first temperature range or the second temperature range. More suitable.

The cover 41 is configured to surround the space 16 containing the workpiece 3 and the set of molds 21, and the environment inside the space 16 can be prevented from radiating heat to the outside and the atmosphere entering the space 16. The cover 41 is composed of a heat insulating member made of a material having excellent heat insulating properties, and a glass wool or aluminum film laminate or the like is attached as a heat resistant material to the inside of a metal case having a water-cooling function. Further, the cover 41 has an opening portion and a door portion (not shown) through which the workpiece can be taken in and out. In the present embodiment, the cover 41 is formed in a box shape, and the body frame 11 is attached to cover the side portion and the upper portion of the body frame 11, but if it is at least surrounding the space 16 including the set of the molds 21, its shape and position are provided. There are no special restrictions on the installation method. Further, in the present embodiment, the cover 41 is formed with a through hole 41a through which the slider driving device 14 that protrudes from the upper portion of the main body frame 11 is inserted, and an blunt gas for introducing the blunt gas to be inserted later. The insertion portion of the introduction portion 41b.

The plastic working device 1 of the present embodiment further includes an inert gas introduction portion 51. The inert gas introduction portion 51 includes a gas cylinder and a metal conduit, such as those not shown, for replacing the environment in the space 16 with an blunt gas such as Ar or N ₂ . By the blunt gas introduction part 51, the surface oxidation of the to-be-processed material 3 can be suppressed to the minimum. The shape, position, and mounting method of the blunt gas introduction portion 51 are not particularly limited. Further, in the present embodiment, the metal conduit formed in the insertion hole 41b formed in the cover 41 is blown into the air, such as Ar or N ₂ . When it is desired to further suppress oxidation of the surface of the workpiece 3, the inert gas introduction portion 51 may further include a vacuum exhaust pump (not shown).

Further, the plastic working device 1 of the present embodiment further includes a temperature measuring unit. The temperature measuring unit includes a thermometer and a display device (not shown) that are attached to the workpiece 3, the mold 21, and the space 16, respectively, to independently measure the temperature of the workpiece 3, the mold 21, and the space 16 independently. . There is no particular limitation on the shape, position, and installation method of the temperature measuring unit. The thermometer can use a contact thermocouple thermometer or an infrared radiation thermometer. Further, in the present embodiment, a thermocouple is used as the temperature measuring portion.

The plastic working apparatus of the present embodiment described above can be summarized as follows.

(6) The plastic working apparatus according to the first embodiment of the present invention includes: a housing for accommodating the workpiece 3 (steel material) and the set of the molds 21; and a member for heating the workpiece 3 (steel) At least one of the mold 21 or the space 16 (the space around the steel material) is a heating portion in which the local temperature T _local of the predicted fracture portion of the workpiece 3 (steel material) is within the first temperature range or the second temperature range; A processed portion in which the workpiece 3 (steel material) heated by the heating portion is plastically deformed by a set of the molds 21.

(7) Next, the cover 41 (heat insulating member) disposed to cover the storage portion is further included.

(8) Next, it further includes a temperature measuring unit for measuring the temperature of the workpiece 3 (steel material), the set of the mold 21, and the space 16 (the space in the housing portion).

[Second Embodiment]

Hereinafter, a plastic working apparatus according to a second embodiment of the present invention will be described. Fig. 6 is a partially cutaway front view showing a schematic structure of a plastic working apparatus according to a second embodiment of the present invention.

In the present embodiment, the structure of the mold 21 is different from that of the above-described first embodiment. Therefore, the differences are mainly described, and the other structures are the same as those of the above-described first embodiment, and the overlapping description will be omitted.

The plastic working device 1 of the present embodiment can plastically process the workpiece 3 disposed between the plastic sheet processing apparatus 1 and the heat medium. For example, the heat medium introduction hole 21c provided in the lower mold 21 can be introduced into the heat medium having the pressure and temperature controlled by the heat medium introduction unit 71 via the pipe 71a. Next, the workpiece 3 which has been fixed between the upper mold 21 and the lower mold 21 by the slider driving device 14 is pressed into the concave portion 21a provided in the upper mold 21 by the pressure of the heat medium. As a result, the workpiece 3 can be formed into a target shape.

As the heat medium, an oil such as eucalyptus oil, air such as air, a blower gas, a steam mist, or an oil mist can be used. Further, the heat medium introduction unit 71 is not particularly limited, and any pressure and temperature of the heat medium can be controlled.

The plastic working apparatus 1 of the present embodiment includes a heater 31 capable of heating an environment including a workpiece 3 and a group of molds 21, a heater 32 capable of heating a group of molds 21, and heating of a heatable medium. The device 34 serves as a heating portion. Further, the heating unit includes a heating furnace 33 that is disposed outside the plastic working apparatus 1 and that can heat the workpiece 3. Using at least one of the heater 31, the heater 32, the heater 34, or the heating furnace 33, the predicted fracture site of the workpiece 3 can be controlled to correspond to the temperature of the portion thereof. Even if there are a plurality of predicted fracture sites in the material to be processed 3, by controlling the above four heat sources, it is possible to more appropriately control the plurality of predicted fracture sites existing in the respective portions to a temperature corresponding to the portions thereof. Further, the heater 31, the heater 32, the heater 34, and the heating furnace 33 may be provided with a cooling function of cooling to a temperature lower than room temperature as needed. In this case, even if the processing-induced metamorphic maximum temperature T _{β of} the workpiece 3 is less than room temperature, the temperature of the predicted fracture portion of the workpiece 3 can be controlled to the first temperature range or the second temperature range. More suitable.

Further, the plastic working device 1 of the present embodiment includes a cover 41 (warm cover, heat insulating member) disposed to cover the space 16. The space 16 covered by the cover 41 is used as a housing for housing the workpiece 3.

Further, the plastic working device 1 of the present embodiment further includes a temperature measuring unit. The temperature measuring unit includes a thermometer and a display device (not shown) that are attached to the workpiece 3, the mold 21, the space 16, and the heat medium introduction unit 71, respectively, so as to independently form the workpiece 3, the mold 21, and the above. The space 16 and the heat medium are individually temperature-measured. The shape, position, and mounting method of the temperature measuring portion are not particularly limited. The thermometer can use a contact thermocouple thermometer or an infrared radiation thermometer.

The plastic working apparatus of the present embodiment described above can be summarized as follows.

(9) The plastic working apparatus according to the second embodiment of the present invention includes: a housing for accommodating the workpiece 3 (steel material) and the set of the molds 21; and a heat medium introduction unit capable of introducing the heat medium into the mold 21 The at least one of the workpiece 3 (steel), the set of the mold 21, the space 16 (the space around the steel), or the heat medium may be heated so that the local temperature T _local of the predicted fracture portion of the workpiece 3 (steel) is a heating portion in the first temperature range or in the second temperature range; and a processing portion that plastically deforms the workpiece 3 (steel material) heated by the heating portion by the pressure of the heat medium.

(10) Next, the cover 41 (heat insulating member) disposed to cover the storage portion is further included.

(11) Next, the temperature measuring unit for measuring the temperature of the workpiece 3 (steel material), the set of the mold 21, the space 16 (the space in the housing portion), and the heat medium is further included.

[First Embodiment]

Hereinafter, the examples of the present invention will be described, but the conditions of the examples are examples of conditions for confirming the possibilities and effects of the present invention, and the present invention is not limited to the examples. The present invention can adopt various conditions within the limits of the gist of the invention and the scope of the invention.

In the physical property analysis step, steels containing Vostian iron (Examples) and steels without Vostian iron (Comparative Examples) were used, and the respective strain ratios β and the respective temperatures of the respective strains ε _eq-critical were measured. The measurement method of the strain ratio β and the limit of each temperature equivalent strain ε _eq-critical was carried out at each temperature by performing a spherical stretch forming test in which the longitudinal and lateral dimensions of the test piece were changed to fix the end of the test piece. The ultimate equivalent strain ε _{eq-critical is} calculated from the strain at which the diameter is reduced and the fracture.

Table 1 shows the measurement results of the respective strain ratios β and the limit equivalent strain ε _eq-critical of each temperature. For example, in the first embodiment, when β=-0.5, the limit equivalent strain ε _{eq-critical is} expressed as a maximum processing-induced metamorphic ductility maximum temperature T _{-0.5 is} 75 ° C, β = 1.0, processing induced metamorphic extension The maximum temperature T _1.0 is 150 °C. In the third embodiment, when β = -0.5, the processing-induced metamorphic maximum temperature T _{- 0.5} is 150 ° C, and when β = 1.0, the processing-induced metamorphic maximum temperature T _1.0 is 250 °C. As described above, in the steel material containing the Worthite iron (Example), the ultimate equivalent strain ε _eq-critical is changed by the influence of the steel type, the processing temperature, and the strain ratio β. On the other hand, in the sixth comparative example, as shown in Table 1, the temperature at which the limit equivalent strain ε _eq-critical is most increased is not affected by the strain ratio β. That is, the processing-induced metamorphic maximum temperature _Tβ does not have a strain ratio β correlation. This is because it does not contain the steel of Worthite Iron (comparative example), but does not represent the TRIP phenomenon.

In Table 2, the results shown in Table 1 σL _β approximated using the representative curve (approximation function) and each resolved to obtain the ratio of strain in the strained more than the stress-induced abnormal temperature side of the temperature T _β great ductility than beta] The limit of influence is the standard deviation of the strain approximation curve, and the standard deviation of the limit equivalent strain approximation curve of σH _β representing the strain ratio β of the higher temperature side of T _β . As described above, by analyzing σL _β and σH _{β for} each strain ratio, the temperature range in which the plastic deformation ability can be improved in each strain ratio can be determined. For example, in the third embodiment, when β = 0, then 2 × σL ₀ = 110 ° C and 1.25 × σH ₀ = 24 ° C, so that the maximum temperature T _β of the induced metamorphic ductility can be processed as a reference, and the decision can be borrowed. The TRIP phenomenon increases the temperature range of the equivalent strain ε _eq-critical from 90 ° C to 224 ° C.

Next, in the deformation form analysis step, the strain ratio β of the predicted fracture portion of the workpiece and the predicted fracture portion is analyzed in the square tube drawing process. Fig. 7 is a schematic view showing the processing of the square tube drawing forming process. As shown in Fig. 7, a square tube punch 62 having a corner of 80 mm, a square tube punch 62 having a 75 mm angle, and a bracket 63 are used, and the billet 64 is processed by the billet 64 (material to be processed). The correlation analysis of the square tube drawing process is performed by plastic mesh measurement. According to the analysis result of the above-described plastic mesh measurement, when the square tube is formed into a shape, the B portion of the blank 64 (the material to be processed) shown in Fig. 7 is a predicted fracture portion, and the plastic deformation of the B portion. Form strain ratio β is β = -0.5 Axial tension state.

Then, in the heating step, the steel material of the third embodiment shown in Table 1 is used as the material to be processed, and at least one of the steel material, the mold or the surrounding space is heated to increase the local temperature T _{local of} the predicted fracture site from 25 ° C. Temperature control was carried out up to 250 °C. Next, the processing step is performed by drawing the steel tube of the third embodiment which has been subjected to temperature control in the above heating step.

Table 3 shows the results of the square tube drawing process in which the steel material of the third embodiment was used as the material to be processed, and the local temperature T _{local of the} predicted fracture site was heated from 25 ° C to 250 ° C. The height of the draw forming shown in Table 3 represents the height at which the material to be processed can be formed without shrinkage and breakage, and the larger the value, the higher the formability.

As shown in Table 1, the steel material of the third embodiment has a processing-induced metamorphic maximum temperature T _{- 0.5 of} 150 ° C at a strain ratio of β = -0.5. Further, as shown in Table 2, in the steel material of the third embodiment, when β _{- 0.5} , 2 × σ L _{- 0.5} is 110 ° C and 1.25 × σ H _{- 0.5} is 69 ° C. That is, when the square tube drawing processing is predicted, if the local temperature T _local of the fracture portion is predicted to be 40 ° C to 219 ° C (first temperature range), the drawing height is high, and when T _local is 150 ° C The height of the pull forming is the highest. Actually, as shown in Table 3, it can be confirmed that the local temperature T _{local of the} predicted fracture site is very high at a draw height value of 50 ° C to 200 ° C in the first temperature range. Secondly, when the local temperature T _local of the fracture site is predicted to be 150 ° C, the draw height is the highest. Compared with the square tube drawing forming process at 25 ° C and 250 ° C outside the above temperature range, even if the same material to be processed is used, once the square tube is formed into the above-mentioned temperature range, the formability is improved. 2 times. As described above, according to the plastic working method of the above aspect of the invention, the occurrence of the diameter reduction and the fracture can be suppressed, and the formability can be improved.

Industrial availability

According to the above aspect of the present invention, it is possible to provide a plastic working method and a plastic working apparatus which can suppress the occurrence of shrinkage and breakage and improve the formability, and thus the industrial applicability is extremely high.

1‧‧‧Plastic processing equipment

3‧‧‧Processed materials

11‧‧‧ body structure

12 ‧ ‧ 承

13‧‧‧ Slider

14‧‧‧ Slider drive

16‧‧‧ Space

21‧‧‧Mold

21‧‧‧上模

21‧‧‧Down

21a‧‧‧ recess

21b‧‧‧ convex

21c‧‧‧Hot media import hole

31,32,34‧‧‧heater

33‧‧‧heating furnace

41‧‧‧ Cover

41a‧‧‧through jack

41b‧‧‧through jack

51‧‧‧Inflatable gas introduction

61‧‧‧ die

62‧‧‧ square tube punch

63‧‧‧ bracket

64‧‧‧Bullet

71‧‧‧The Ministry of Thermal Media Introduction

71a‧‧‧Pipe

Figure 1 is a schematic diagram showing the phenomenon of abnormal induced plasticity.

Fig. 2 is a schematic view showing uniaxial stretching, plane strain stretching, and isotropic biaxial stretching.

Fig. 3 is a graph showing the temperature dependence of the strain of each strain ratio of the low carbon steel.

Fig. 4 is a graph showing an approximation of the normal distribution of the ultimate strain temperature dependence of β = 0 in Fig. 3.

Figure 5 is a schematic view showing a plastic working apparatus according to an embodiment of the present invention. A partial cut of the front view of the slightly constructed structure.

Fig. 6 is a partially cutaway front elevational view showing the schematic structure of a plastic working apparatus according to another embodiment of the present invention.

Figure 7 is a schematic view showing the processing of the square tube drawing.

Claims (11)

A plastic working method, which is a plastic working method comprising a steel of Vostian Iron, comprising the following steps: a physical property analysis step, wherein T _β (unit ° C) represents a process-induced metamorphic ductility of the steel material which is changed by the strain ratio β; maximum temperature to σL _β indicates higher the T _β a lower temperature by the strained side ratio limit beta] influence of considerable strain standard deviation of the approximate curve of order σH _β Representative than the foregoing strain by the higher temperature side of T _β affect the ratio beta] limit considerable strain approximate standard deviation curve of, for each the strain ratio beta] the T _β measurement, the σL _β, the σH _β; deformation mode analysis step, defining plastically deform the steel predicted cleavage site of time to βx representative of the When predicting the strain ratio of the fracture site, the strain ratio βx is analyzed, and then the strain ratio βx is selected from the strain ratio β; and the heating step is performed, and _Tβx (unit °C) represents the processing-induced metamorphic ductility corresponding to the strain ratio βx. The maximum temperature, σL _βx represents the ultimate strain approximation curve of the lower temperature side of the aforementioned T _βx affected by the aforementioned strain ratio βx The standard deviation, σH _βx represents the standard deviation of the limit equivalent strain approximation curve affected by the aforementioned strain ratio βx on the higher temperature side of the aforementioned T _βx , and T _local (unit ° C) represents the local temperature of the predicted fracture site, respectively selected from the aforementioned _T β _T βx, selected from the foregoing _σL β _σL βx, selected from the foregoing _σH β _σH βx, then, so that the local temperature T _local of the following formula in the first temperature range shown in FIG. The inner method is heated; and the processing step is to plastically deform the steel material after the heating step; T _βx −2×σL _βx ≦T _local ≦T _βx +1.25×σH _βx (Expression 1). In the plastic working method of claim 1, the ΔT _local (unit ° C) represents the temperature change of the local temperature T _local changed in the plastic deformation of the processing step, and the deformation form analysis step further analyzes the temperature The change ΔT _local , the heating step is performed such that the local temperature T _{local is} within the second temperature range shown by the following formula 2, T _{βx −ΔT local} −2×σL _βx ≦T _local ≦T _βx - ΔT _local + 1.25 × σH _βx (...). The plastic working method according to claim 1, wherein the heating step heats at least one of the steel material, the mold, or the space around the steel material so that the local temperature T _{local is} within the first temperature range. The plastic working method according to claim 1, wherein the heating step is to heat the heat medium such that the partial temperature T _{local is} within the first temperature range, and the processing step is performed by the pressure of the heat medium Plastic deformation of steel. In the plastic working method according to the second aspect of the patent application, the deformation form analysis step analyzes the predicted fracture site, the strain ratio βx, and the temperature change ΔT _local by a plastic working simulation. A plastic working device for performing a plastic working method according to claim 1 of the patent application scope, comprising: a collecting portion for accommodating the steel material and the mold; The heating unit may heat at least one of the steel material, the mold or the space around the steel material, and the processing unit, and the steel material heated by the heating unit may be plastically deformed by the mold. A plastic working apparatus according to claim 6 of the invention, further comprising a heat insulating member disposed to cover the receiving portion. A plastic working apparatus according to claim 6, wherein the temperature measuring unit for measuring the temperature of the steel material, the mold, and the space in the housing portion is included. A plastic working apparatus for performing a plastic working method according to the fourth aspect of the patent application, comprising: a collecting portion for accommodating the steel material and the mold; and a heat medium introducing portion for introducing the heat into the mold a heating unit capable of heating at least one of the steel material, the mold, the space surrounding the steel material, or the heat medium; and the processing portion, wherein the steel material heated by the heating portion is plasticized by the pressure of the heat medium Deformation. A plastic working apparatus according to claim 9 which further comprises a heat insulating member disposed to cover the receiving portion. The plastic working apparatus according to claim 9, wherein the temperature measuring unit for measuring the temperature of the steel material, the mold, the space inside the housing portion, and the heat medium is included.