JP2006198666A - Method and apparatus for hot press forming metallic sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for hot press forming by which the strength in each part of a press formed article are set correctly and optionally by controlling the temperature of a heated metallic sheet. <P>SOLUTION: In the hot press forming method by which the strength of the press formed article is adjusted by a hot forming and a cooling process of the heated metallic sheet by using a die, in the hot press forming method, the press forming is started after measuring the temperature in each part of the metallic sheet and setting the temperature in each part of the metallic sheet to the temperature in accordance with the strength in each part of the press forming article by either or both of a heating means and a cooling means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hot press molding method and apparatus for molding a heated metal plate material using a mold, and in particular, a hot press molding method for a metal plate material capable of accurately and arbitrarily setting the strength of each part of a press molded product. And to the device.

Metal sheet press molding is highly productive, excellent in dimensional accuracy, and stable in quality with little variation in strength between pressed products, making it suitable for manufacturing automobiles, machinery, electrical equipment, transportation equipment, etc. It is the most common processing method widely used.
However, press products in recent years, especially automobile parts, are required to have high strength from the viewpoint of weight reduction, etc., and this leads to a decrease in formability, particularly a decrease in shape freezing due to the occurrence of a springback, It has become difficult to manufacture a press product having a complicated shape.

  For this reason, in the press industry of a metal plate material, the hot press molding method which shape | molds the heated metal plate material using a metal mold attracts attention. In the hot press forming method, since the metal plate material is press-formed while being heated to a high temperature, the metal plate material with reduced material strength is deformed straight along the molding surface of the mold, even if it has a complicated shape. It can be molded with excellent dimensional accuracy. In addition, since the mold is rapidly cooled by the heat removal effect of the mold, no springback is generated, the shape has a good freezing property, and the dimensional accuracy of the pressed product can be improved. Furthermore, when the metal plate material is steel, the steel plate is heated to an austenite region, and is held in a mold, for example, held in a mold and rapidly cooled by a mold contact heat removal effect, resulting in high strength due to martensitic transformation. Can be achieved.

However, although it is a hot press molding method that is advantageous in terms of molding as described above, there is a problem that the strength variation between the pressed products is large compared to the conventional cold press molding method. This is because in a hot press, a metal plate material to be molded is heated to a high temperature in a heating furnace or the like, and this is conveyed to a press molding device by a conveying device having a support portion such as an arm. In the contact portion with the support portion, the temperature is lowered due to contact heat removal, resulting in uneven temperature of the metal plate, and this is caused by pressing the metal plate with the temperature unevenness occurring. is there.
For this reason, in order to prevent unevenness in temperature of the metal plate material due to conveyance, and in turn, variation in strength between the pressed products due to the temperature unevenness, the metal plate material is not heated and conveyed by a heating device such as a heating furnace. A method of heating a metal plate inside the mold has been proposed. For example, a plurality of electrodes are attached to a metal plate set between a punch and a die, electric power is supplied between the opposing electrodes to generate Joule heat, and the metal plate heated uniformly by this method is hot pressed A method is disclosed (for example, see Patent Document 1).
However, this method can solve the problem of uneven temperature in the metal plate during transportation, but each time it is set in the mold, multiple electrodes must be attached to the metal plate, and the Joule heat It is not difficult to imagine that productivity will be significantly reduced. Therefore, there is a considerable practical problem in applying the method to press forming of a metal plate material that requires productivity.

Further, the hot press molding method has a problem that productivity is lowered as compared with the conventional cold press molding method. This is due to the fact that the holding time in the mold at the bottom dead center has to be set long in order to eliminate the problem that the shape freezing property decreases with the increase in strength of the pressed product as described above. It is.
For this reason, not only the cooling process by the mold contact heat removal effect as described above, but also a new cooling process is provided with a coolant introduction groove on at least one of the molding surfaces of the die and the punch, and the coolant is introduced into the coolant introduction groove. A method for shortening the holding time in the mold by the cooling effect of the refrigerant and improving the productivity is also disclosed (for example, see Patent Document 2).

Furthermore, as another issue related to the hot press forming method, a metal plate material is heated to an austenite region, and this is held in a mold and rapidly cooled to achieve high strength by martensitic transformation. However, there is a problem in that post-processing such as drilling (piercing) or cutting (trim) becomes difficult due to excessive increase in quenching hardness.
For this reason, by introducing a new cooling process that reduces the quenching hardness of the parts that require post-processing by changing the contact area of the mold forming surface and the mold temperature for each molding part, A method for facilitating the disclosure is disclosed (for example, see Patent Document 3).

As described above, various improvements have been attempted for the problems caused by the hot press characteristics of heating the metal plate material to a high temperature and the problems caused by the high strength, which is an excellent feature of the hot press, The hot press forming method can be said to be a press forming method that can achieve both high strength and excellent dimensional accuracy that could not be realized by the conventional cold press forming method.
However, all of the above-described techniques can locally increase the strength of a press-molded product, that is, the strength of a specific portion such as a portion requiring high strength or a portion requiring post-processing by a predetermined cooling process. However, the strength of each part of the press-formed product could not be arbitrarily set. Also, the strength of the specific part is not excellent in accuracy, and the strength of each part of the press-formed product cannot be accurately set or adjusted.

On the other hand, the characteristics required for automobile parts and the like are not limited to lightening and increasing strength as described above. For example, in recent years, the body of automobiles has become more demanding of product design and collision safety, so the thickness and strength of each part of the body are detailed in order to achieve the performance. The number of parts constituting the body has reached several hundred.
For this reason, press materials, that is, tailored blanks in which a plurality of metal plate materials having different plate thicknesses and strengths are joined and integrated, are widely used in recent automobile parts and the like. Tailored blanks have an excellent feature that the characteristics of one metal plate can be partially changed according to the purpose. For example, a high-strength steel plate is applied only to parts where strength is required. While maintaining the necessary strength, it is possible to reduce the weight of the portion that does not require strength. In addition, since a metal plate material having a thickness and strength suitable for the purpose is selected and joined together by welding, it is possible to accurately and arbitrarily set the strength of each part of the press-formed product according to the purpose. . For this reason, it is possible to manufacture a body excellent in collision safety while satisfying a design with a strong product, and to reduce the number of parts.
However, although it is a tailored blank that contributes not only to reducing the weight and strength of the automobile body but also to improving design and collision safety, as described above, the metal plate materials are joined and integrated by welding, The production of tailored blanks requires advanced welding techniques. In other words, if advanced welding technology is not applied, the welded portion is likely to break when it is press-molded, and if the strength of the welded portion cannot be secured, the excellent characteristics of the tailored blank as described above may be exhibited. Can not. Moreover, in the current situation where the strength of automobile parts is increasing, an increasingly advanced welding technique is required.

  That is, as described above, the hot press forming method can be said to be a press forming method that can achieve both high strength and excellent dimensional accuracy that could not be realized by the conventional cold press forming method. In today's environment, it is not only satisfying the above characteristics, but as a new technology that replaces tailored blanks, the hot press that can set the strength of each part of the press-formed product accurately and arbitrarily according to the purpose. The development of molding technology is highly desired in the industry.

Furthermore, in recent years, a hot press molding technique that can perform draw molding or foam molding with a severe curvature is newly desired. This is because, in cold press, the deformation resistance of the stretched part is improved by work hardening, but in hot press, the metal plate material is heated to a high temperature, so the deformation resistance of the metal plate material is low. It is.
That is, with the recent increase in strength of press products, the conventional cold press forming technique has a problem that shape freezeability is reduced, and it is a hot press forming method that has been attracting attention to deal with this. In the hot press forming technology that heats a metal sheet to a high temperature, once the elongation associated with forming occurs, the cross-sectional area of the part decreases, so the strength of the part where the sheet thickness decreases due to the elongation becomes lower and lower. When press molding with a strong material flow accompanying the molding process represented by deep drawing is performed, there is a problem that local thinning or breakage occurs in the stretched part, and so-called draw molding cannot be performed. It was. Further, even in the foam molding in which the material flow accompanying the processing is not severe as compared with the deep drawing molding, there is a problem that the fracture occurs when the curvature is severe.
JP 2002-248525 A JP 2002-282951 A JP 2003-328031 A

The problem to be solved by the present invention is not to set the strength of each part of the press-formed product by joining a plurality of metal plate materials having different thicknesses and strengths by welding, but to control the temperature distribution and cooling rate of the metal plate material. Thus, it is to provide a hot press molding method and apparatus capable of accurately and arbitrarily setting the strength of each part of the press molded product.
Further, another problem to be solved by the present invention is to provide a hot press molding method and apparatus capable of draw molding and form molding with severe curvature, which could not be realized by conventional hot press molding technology. It is.

As a result of numerous theoretical and experimental studies, the present inventor first obtained the following knowledge in order to solve the problem of accurately and arbitrarily setting the strength of each part of the press-formed product according to the purpose.
(A) When press forming is performed while controlling the temperature distribution and cooling rate of a metal plate material to be formed by a predetermined means, the strength of each part of the press-formed product can be set accurately and arbitrarily. Specifically, before starting the press, the temperature of each part of the metal plate material, for example, the part corresponding to each part of the press-formed product is measured, and the temperature of each part of the metal plate material is press-formed by one or both of the heating means and the cooling means. When press molding is started after setting the temperature according to the strength of each part of the product, the strength of each part of the press-molded product can be set accurately and arbitrarily. Furthermore, the strength of each part of the press-formed product can be set more accurately and arbitrarily by controlling the cooling rate of each part of the metal plate material after the start of forming as well as the temperature setting before the start of pressing by the above method. .

  This will be described below with reference to FIG. 1 schematically showing the principle of the present invention. FIG. 1 is an example of a CCT curve of carbon steel indicating that when the metal plate is a steel plate, the structure of the steel plate can be controlled by controlling the cooling start temperature and the cooling rate of the steel plate. For example, when the steel sheet is cooled from the cooling start temperature T1, if it is cooled according to the cooling curve 1, it passes through the outside of the nose (borderline of transformation), so that most of the steel material becomes martensite and a high strength structure is obtained. On the other hand, when cooled according to the cooling curve 2, ferrite and cementite are precipitated to pass through the inside of the nose, so that the martensite ratio in the steel material obtained after cooling is reduced, and a relatively low strength structure is obtained. Further, when cooling is performed in accordance with the cooling curve 3 having the same cooling rate as the cooling curve 2 with the cooling start temperature T2 lower than T1, ferrite and cementite are precipitated at a lower rate than in the cooling curve 2, and thus obtained after cooling. The ratio of martensite in the steel material is larger than that in the case of the cooling curve 2 and smaller than that in the case of the cooling curve 1, and a medium strength structure is obtained.

  That is, the cooling process which is one of the features of the present invention or the present invention is in line with the CCT curve of carbon steel indicating that the structure of the steel sheet can be controlled by controlling the cooling start temperature and cooling rate of the steel sheet, Before starting the press, the cooling start temperature of each part of the metal plate material is set according to the strength of each part of the press-formed product by a predetermined means, for example, one or both of the heating means and the cooling means. The essence is to control the strength of each part of the press-formed product by controlling the cooling rate of each part of the metal sheet by means. Then, by independently controlling the cooling start temperature and the cooling rate for any part of the metal plate material, it is possible to obtain press-formed products having different mechanical properties in any part, that is, press molding. The essence is to freely control the strength of each part according to the purpose. Note that rapid cooling is not required as the refrigerant is used, the processing is not severe, and if sufficient cooling speed can be obtained by heat removal by contact with the mold, press molding processing may be performed without discharging the refrigerant. Needless to say.

(B) And, as means for cooling the temperature of each part of the metal plate material before the start of molding, or means for controlling the cooling rate of each part of the metal plate material during or after molding, productivity and controllability From the viewpoint of cooling, cooling by refrigerant discharge from a plurality of refrigerant discharge ports provided on the mold surface is desirable. In addition, by sequentially collecting the refrigerant from a plurality of refrigerant collection ports provided on the mold surface, the cooling efficiency and controllability by the refrigerant discharge are further improved.
(C) Further, the refrigerant discharge is controlled by controlling one or more parameters selected from the refrigerant discharge amount, the discharge flow rate, the discharge pressure, the discharge time, and the discharge timing, and for each refrigerant discharge port or a plurality thereof. If the refrigerant discharge from the refrigerant discharge ports is grouped and controlled for each group, it is possible to freely change the heat transfer coefficient of cooling by refrigerant discharge, thereby freely controlling the strength of each part of the molded product Be possible.

Next, in order to prevent local thinning and breakage of a metal plate material as a molding material, the present inventor is responsible for the cause of breakage and thinning due to draw molding and severe form forming, and a method for solving this. As a result of many theoretical and experimental studies, the following findings were obtained.
(D) In the cold press, the deformation resistance of the stretched part is improved by work hardening, but in the hot press, the metal plate material is press-formed in a heated state, so the deformation resistance of the metal plate material is low. Once the elongation due to molding occurs, as shown in Fig. 9 (c), the cross-sectional area of the stretched portion becomes smaller, so the strength of the portion where the plate thickness decreases due to the elongation becomes even lower. In fact, breakage occurs. FIG. 9A schematically shows a metal plate material that is a uniformly heated material, and FIG. 9B schematically shows a press-formed product when cylindrical drawing is performed using the metal plate material.

(E) However, as shown in FIG. 9 (d), if the temperature of the part having a high degree of processing, that is, the part where the plate thickness decreases due to the elongation accompanying the molding, is lowered in advance, and the strength of the part is increased. As shown in FIG. 9 (f), the other portion having a lower strength than the portion is extended, so that the load on the portion with a high degree of processing can be reduced and the breakage can be prevented.
(F) Further, not only the temperature distribution in the form as shown in FIG. 9D, but also the temperature distribution in the form as shown in FIG. The above effect can also be obtained by forming a temperature distribution in which low-temperature parts appear alternately.
(G) Further, the position of the portion where the plate thickness decreases due to elongation, that is, the position of the metal plate material to be temperature-set according to the degree of processing can be specified by an experiment conducted in advance.
(H) Therefore, the temperature of each part of the metal plate material is measured in advance before the start of press molding, and the temperature of each part of the metal plate material is determined according to the degree of processing of each part of the press-formed product by one or both of the heating means and the cooling means. If you start press forming after setting the temperature to the desired temperature, it will be possible to perform hot stamping and form forming with severe curvature without causing local thinning and breakage of the metal plate material. To be possible.

(I) Furthermore, not only the temperature setting before the press start by the above method but also the moldability is further improved by controlling the cooling rate of each part of the metal plate material after the start of forming. That is, the temperature of each part of the metal plate material is measured in advance before the start of press molding, and the temperature of each part of the metal plate material is set to a temperature corresponding to the degree of processing of each part of the press-formed product by one or both of the heating means and the cooling means. After the setting, press molding is started, and after the molding is started, the cooling rate of each part of the metal plate material is controlled by a predetermined cooling means to further improve the draw moldability and form moldability by hot pressing.
(G) And as a predetermined cooling means for controlling the cooling rate of each part of the metal plate material after the start of molding, it is desirable to cool by discharging refrigerant from a plurality of refrigerant discharge ports provided on the surface of the mold. In addition, by sequentially collecting the refrigerant from a plurality of refrigerant collection ports provided on the mold surface, the cooling efficiency and controllability by the refrigerant discharge are further improved.

  Based on the above knowledge, the present inventor has established a hot press molding method and apparatus capable of accurately and arbitrarily setting the strength of each part of the press molded product, which could not be realized by the prior art, and draw molding and curvature. The present inventors have conceived a hot press molding method and apparatus capable of forming a severe form. The gist is as follows.

(1) In a hot press forming method in which the strength of a press-formed product is adjusted by a hot forming and cooling process using a mold with a heated metal plate material, the temperature of each part of the metal plate material is measured, and the heating means and the cooling means A hot press forming method characterized in that the press forming is started after the temperature of each part of the metal plate material is set to a temperature corresponding to the strength of each part of the press molded product by either one or both.
(2) In a hot press forming method in which the strength of a press-formed product is adjusted by a hot forming and cooling process using a mold for a heated metal plate material, the temperature of each part of the metal plate material is measured, and the heating means and the cooling means A hot press forming method characterized in that press forming is started after setting the temperature of each part of the metal plate material to a temperature corresponding to the degree of processing of each part of the press molded product by either one or both.

(3) In a hot press forming method in which the strength of a press-formed product is adjusted by a hot forming and cooling process using a mold for a heated metal plate material, the temperature of each part of the metal plate material is measured, and the heating means and the cooling means Either one or both sets the temperature of each part of the metal plate material to a temperature corresponding to the strength of each part of the press-molded product, and then starts press molding. After molding starts, either or both during molding and after molding Cooling of each part of the metal plate material by discharging refrigerant from a plurality of refrigerant discharge ports provided on the mold surface, or discharging refrigerant from a plurality of refrigerant discharge ports provided on the mold surface and collecting refrigerant from the refrigerant recovery port A hot press molding method characterized by controlling the speed.
(4) In a hot press forming method in which the strength of a press-formed product is adjusted by a hot forming and cooling process using a mold with a heated metal plate material, the temperature of each part of the metal plate material is measured, and the heating means and the cooling means Either or both, the temperature of each part of the metal plate material is set to a temperature corresponding to the degree of processing of each part of the press-molded product, and then press molding is started, and after molding starts, either during molding or after molding or In both cases, by discharging refrigerant from a plurality of refrigerant discharge ports provided on the mold surface, or by discharging refrigerant from a plurality of refrigerant discharge ports provided on the mold surface and collecting refrigerant from the refrigerant recovery port, A hot press forming method characterized by controlling a cooling rate.

(5) The refrigerant discharge is controlled by one or more parameters selected from a refrigerant discharge amount, a discharge flow rate, a discharge pressure, a discharge time, and a discharge timing, and each refrigerant discharge port or a plurality of refrigerants The hot press molding method according to (3) or (4), wherein the refrigerant discharge from the discharge ports is grouped and controlled for each group.
(6) The hot press forming method according to any one of (1) to (5), wherein the metal plate material is a steel plate.
(7) The hot press forming method according to (6), wherein the steel sheet is a steel sheet that undergoes martensitic transformation or bainite transformation.

(8) In a hot press forming apparatus for forming a heated metal plate material using a mold, a means for measuring the temperature of each part of the metal plate material, and the temperature of each part of the metal plate material according to the strength or degree of processing of each part of the press molded product Heating means for raising the temperature to a predetermined temperature, cooling means for cooling the temperature of each part of the metal plate material to a temperature according to the strength or degree of processing of each part of the press-formed product, and a mold for forming the metal plate material A hot press molding device.
(9) In a hot press forming apparatus for forming a heated metal plate material using a mold, means for measuring the temperature of each part of the metal plate material, and the temperature of each part of the metal plate material according to the strength or degree of processing of each part of the press molded product Heating means for raising the temperature to a predetermined temperature, cooling means for cooling the temperature of each part of the metal plate material to a temperature according to the strength or degree of processing of each part of the press-formed product, and a plurality of refrigerant discharge ports on the surface, A mold communicating with the discharge port and provided with a refrigerant supply pipe provided with at least one of an on-off valve, a flow rate adjustment valve and a pressure adjustment valve; an on-off valve, a flow rate adjustment valve and a pressure provided on the refrigerant supply pipe A hot press molding apparatus comprising: an apparatus for controlling refrigerant discharge from each refrigerant discharge port by controlling at least one of the regulating valves.

(10) The hot press molding apparatus according to (9) above, wherein an opening / closing valve, a flow rate adjustment valve, and a pressure adjustment valve of the refrigerant supply pipe are installed in a die set.
(11) The mold according to (9) or (10), wherein the mold is a mold having a plurality of refrigerant recovery ports on a surface thereof, and a refrigerant recovery pipe communicating with each of the refrigerant recovery ports. The hot press molding apparatus described in 1.
(12) The mold (8), wherein the mold has a plurality of protrusions having an area ratio of 1 to 90%, a diameter or a circumscribed circle diameter of 10 μm to 5 mm, and a height of 5 μm to 1 mm. The hot press molding apparatus according to any one of to (11).

(A) According to the present invention, the temperature management of the metal plate material before the start of pressing can be performed accurately, so that the strength variation between the pressed products can be reduced.
(B) Also, before starting the press, each part of the metal plate material to be molded, specifically, the temperature of the part corresponding to each part of the press-formed product is measured, and by either one or both of the heating means and the cooling means, Since press molding is started after the temperature of each part of the metal plate material is set to a temperature corresponding to the strength of each part of the press-formed product, the strength of each part of the press-formed product can be set accurately and arbitrarily according to the purpose.
(C) Furthermore, not only the temperature setting of each part of the metal plate material before the start of pressing by the above method, but also after the start of press molding, each part of the metal plate material is discharged by refrigerant discharge from a plurality of refrigerant discharge ports provided on the mold surface. Since the cooling rate can be freely changed, the strength of each part of the press-formed product can be set more accurately and arbitrarily. That is, according to the present invention, the strength of each part of the press-formed product can be set accurately and arbitrarily according to the purpose without joining a plurality of metal plate materials having different thicknesses and strengths as in the tailored blank by welding. it can. Needless to say, the strength of the press-formed product can be made uniform. Specifically, for parts that require strength, increasing the cooling start temperature and cooling rate can increase the strength by martensitic transformation or bainite transformation, while drilling (piercing) or cutting. For parts that require post-processing such as processing (trim), that is, parts that do not require strength, the cooling start temperature is lowered before the start of pressing, or cooling is performed during or after molding. By reducing the speed, the strength can be reduced. In addition, if press molding is started after changing the temperature of the metal plate material for each part of the molded product, it is possible to obtain a press molded product having a different strength for each part of the molded product, and either during molding or after molding. If the cooling rate of the metal plate material in one or both is made different for each part of the molded product, press molded products having different strengths for each part of the molded product can be obtained.

(D) Moreover, according to the hot press molding method according to the present invention, it is possible to perform draw molding or form molding with severe curvature, which cannot be realized by the conventional hot press molding method. Specifically, when the conventional hot press molding technique is used to perform the draw molding represented by deep drawing, etc., there is a problem that local thinning or breakage occurs in the stretched portion. In the hot press forming method according to the present invention, the temperature of each part of the metal plate material is measured in advance before the start of press forming, and the temperature of each part of the metal plate material is pressed by one or both of the heating means and the cooling means. Since the press molding is started after setting the temperature according to the processing degree of each part of the molded product, it is possible to increase the strength of the part where the elongation occurs and the fracture occurs, and as a result, the elongation is increased. It is possible to achieve load distribution in the generated portion and prevent breakage. Furthermore, not only the temperature setting before the press start by the said method but the formability can be further improved by controlling the cooling rate of each part of the metal plate material after the start of forming. Specifically, the temperature of each part of the metal plate material is measured in advance before the start of press molding, and the temperature of each part of the metal plate material is determined according to the degree of processing of each part of the press-formed product by one or both of the heating means and the cooling means. Press forming is started after the temperature has been set, and after the start of forming, by controlling the cooling rate of each part of the metal plate by a predetermined cooling means, the load distribution in the part where elongation occurs can be controlled more accurately As a result, it is possible to further improve draw moldability and foam moldability by hot pressing.
(E) Furthermore, since cooling by refrigerant discharge is performed, it goes without saying that a press product having excellent shape freezing property and good dimensional accuracy can be manufactured. In addition, productivity can be improved by shortening the holding time in the mold.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to FIGS. 2A and 2B are schematic explanatory views of a hot press forming apparatus according to the present invention, in which FIG. 2A shows a die holder and a punch holder, and FIG. 2B shows a die holder and a punch for clarifying the structure of the apparatus. It is the figure which abbreviate | omitted and showed the holder. FIG. 3 is a schematic explanatory view schematically showing the principle of the present invention. FIG. 4 is an explanatory view showing a mold having a refrigerant discharge function according to the present invention, and is a cross-sectional view when the punch has the function. FIG. 5 is an explanatory view showing an example of a mold according to the present invention, and is a view showing a surface of the mold on which a refrigerant discharge port, a refrigerant recovery port, and a protrusion are formed. FIG. 6 is a cross-sectional view showing an example of a mold according to the present invention, and is a view showing a cross section of a mold in which a refrigerant discharge port, a refrigerant recovery port, and a protrusion are formed. FIG. 7 is a cross-sectional view illustrating another example of the mold according to the present invention, and is a view illustrating a cross-section of the mold in which the refrigerant discharge port, the refrigerant recovery port, and the protrusion are formed.

One of the problems to be solved by the present invention is a hot press forming method in which the strength of the press-formed product 30 is adjusted by a hot forming and cooling process for a heated metal sheet 1 using a mold, which is realized in the prior art. It is to accurately and arbitrarily set the strength of each part of the press-formed product, which has been impossible. That is, the present invention forms the metal plate 1 heated to the A1 transformation point or higher using a mold, and the greatest feature thereof is to measure the temperature of each part of the metal plate before starting the press, The temperature of is set to a temperature corresponding to the strength of each part of the press-formed product by one or both of the heating means and the cooling means, and then press molding is started, and after molding starts, either during molding or after molding Or, by controlling the cooling rate of each part of the metal plate using a mold that has a refrigerant discharge function in both, it is possible to set the strength of each part of the press-formed product that was impossible to achieve with the prior art accurately and arbitrarily. It is what.
Note that the mold having the refrigerant discharge function not only controls the cooling rate of each part of the metal plate material during or after molding, but also before the start of molding, as shown in FIG. Note that the temperature of the can be controlled. FIG. 3 is a schematic explanatory view schematically showing the principle of the present invention. In this figure, it schematically shows that the refrigerant is discharged from the refrigerant discharge port 12 at the position indicated by the black circle. .
Hereinafter, (1) a molding material used in the present invention and a heating method thereof, (2) measuring means for setting the temperature of each part of the metal plate material to a temperature according to the strength or degree of processing of each part of the press-molded product, A heating means, (3) a mold having a refrigerant discharge function, and (4) a control method and apparatus for refrigerant discharge will be described in order.

(1) First, the heating method and heating temperature of the molding material used in the present invention and the molding material before being set in the mold will be described.
The molding material used in the present invention is a metal plate 1 and can be applied to any steel plate such as an Al-plated steel plate, a Zn-plated steel plate, a high-strength steel plate, and ordinary steel.
Further, a steel sheet that undergoes martensitic transformation or bainite transformation can be increased in strength by quenching by refrigerant discharge, and therefore, a steel plate that undergoes martensitic transformation or bainite transformation is desirable. It is not always necessary to transform the refrigerant when it is discharged, and it may be transformed after molding.
The method of heating the metal plate 1 is not particularly limited, and any method that can heat the metal plate 1 to the A1 transformation point or higher, heating in an electric furnace, gas furnace, flame heating, current heating, high frequency Any method such as heating or induction heating may be used.

(2) In the present invention, the metal plate 1 heated to the A1 transformation point or higher by the above method is set in a mold, and the temperature of each part of the heated metal plate 1 is measured by the temperature measuring means 24. The temperature measuring means 24 is not particularly limited as long as it can measure the temperature of each part of the metal plate 1 as a molding material, but a radiation thermometer is desirable.
If the temperature does not reach the temperature corresponding to the strength of each part of the press-formed product, the temperature is raised to the temperature by the heating means 25. If the temperature exceeds the temperature corresponding to the strength of each part of the press-formed product, the temperature is cooled to the temperature by the cooling means 26. Then, when the temperature of each part of the metal plate material is set to the above temperature, pushing is started. That is, the temperature corresponding to the strength of each part of the press-formed product is the cooling start temperature shown in FIG. 1, for example, the cooling start temperature of each part of the metal plate material is made constant, and the cooling rate of each part of the metal plate material after the start of pressing is When controlled to be constant, a press-formed product 30 having a uniform strength can be obtained. Further, even if the cooling start temperature of each part of the metal plate material is kept constant, if the cooling rate of each part of the metal plate material after the start of press is controlled to be different, the press-formed product 30 having different mechanical characteristics in any part is obtained. be able to.
As the heating means 25, there are energization heating, infrared heat beam, laser beam, induction heating and the like, but an electric heater is desirable. The cooling means 26 may be cooled using the mold having the refrigerant discharge function according to the present invention as described above, or may be masked in advance in a heating furnace or the like to obtain a predetermined temperature distribution. You may form. Or in the step which conveys the metal plate 1 heated to the metal mold | die from heating apparatuses, such as a heating furnace, you may form predetermined temperature distribution by contact heat removal with a conveying apparatus.

(3) Next, a mold constituting the cooling means, that is, a mold that is a direct cooling means for controlling the cooling start temperature of the metal plate before the start of pressing and the cooling rate after the start of pressing is shown in FIG. Will be described in detail. The term “directly” is intended to realize the refrigerant discharge function by controlling the mold having the refrigerant discharge function by a control device 23 described later.
As shown in FIG. 2, the mold constituting the hot press molding apparatus 2 according to the present invention includes an upper die including a die 3, a pad 5, a die holder 9 and a die base 7, a punch 4, a plate presser 6, It is comprised from the lower mold | type provided with the punch holder 10 and the die base 8. FIG. The die holder 9 also serves as a pad holder, and the punch holder 10 serves as a plate holding holder. Hereinafter, these sets are referred to as a die set 11. FIG. 2B is a diagram in which the die holder and the punch holder are omitted in order to clarify the configuration of the apparatus.

FIG. 4 is an explanatory view showing a mold having a refrigerant discharge function according to the present invention, and is a cross-sectional view when the punch 4 has the function. The refrigerant discharge function includes the die 3, the pad 5, and the punch 4. It is desirable that at least one of the plate holders 6 has a refrigerant discharge function. Hereinafter, the case where the punch 4 has a refrigerant discharge function will be described.
As shown in FIG. 4, a mold having a refrigerant discharge function according to the present invention has a plurality of refrigerant discharge ports 12 for discharging a refrigerant to a metal plate 1 as a molding material on the surface, and the refrigerant discharge port is provided inside. A refrigerant supply pipe 13 that communicates with the outlet 12 and includes at least one of an on-off valve 14, a flow rate adjustment valve 15, and a pressure adjustment valve 16 is disposed.
4 shows an example in which the coolant discharge port 12 is provided in the vertical wall portion of the punch 4, but it may be provided in the top portion or in both the vertical wall portion and the top portion. The same applies to the case where the refrigerant outlet 12 is provided in the plate holder 6. On the other hand, when the coolant discharge port 12 is provided in the upper die 3 or the pad 5, it may be provided at the bottom or at both the vertical wall and the bottom.

The refrigerant discharge port 12 and the refrigerant supply pipe 13 communicating with the refrigerant discharge port 12 can be formed by mechanical drilling by a drill or drilling by electric discharge machining. In this case, the die material is preferably hot working die steel from the viewpoint of hot strength.
In addition, since the refrigerant supply pipe 13 fulfills the refrigerant discharge function as long as it communicates with the refrigerant discharge port 12, it penetrates from the inside of the mold to the outer surface instead of drilling the refrigerant discharge port 12 and the refrigerant supply pipe 13 in the mold. The refrigerant supply pipe 13 may be connected to a porous metal having pores. In this case, it is desirable to use a porous metal having a plurality of holes having a diameter of 100 μm to 1 mm and a pitch of 100 μm to 10 mm penetrating in the thickness direction. For example, in the punch having the configuration shown in FIG. 3, if the core 20 is made of die steel and the punch 4 is made of a porous metal, the coolant discharge ports 12 and the coolant supply pipes 13 that are fine and have a small pitch can be formed. Such a porous metal can be produced by unidirectional solidification in which the direction of the solidified structure is made constant by temperature control after sintering the powder after molding or by melting the metal.
When press molding is performed by discharging the coolant with such a mold, but rapid cooling is not required as the coolant is used, processing is not severe, and sufficient cooling rate can be obtained by heat removal by contact with the mold Alternatively, press molding may be performed without discharging the refrigerant.

Next, functions of the on-off valve 14, the flow rate adjustment valve 15 and the pressure adjustment valve 16 of the refrigerant supply pipe 13 will be described.
In general, the cooling capacity by the refrigerant can be expressed using a heat transfer coefficient α, and the relationship between the heat transfer coefficient α, the refrigerant discharge amount Q, the discharge flow rate U, the discharge pressure P, and the discharge time T is expressed by the following equation. Can be represented. Note that f, g, and h represent functions, for example, that the heat transfer coefficient α is established as a function of the refrigerant discharge amount Q.
Heat transfer coefficient α = f (refrigerant discharge amount Q) (1)
Refrigerant discharge amount Q = g (discharge flow velocity U, discharge time T) (2)
Discharge flow rate U = h (discharge pressure P) (3)

That is, according to the present invention, the refrigerant discharge amount Q, the discharge flow velocity U, the discharge pressure P, the discharge time T, and the at least one of the on-off valve 14, the flow rate adjusting valve 15 and the pressure adjusting valve 16 of the refrigerant supply pipe 13 are One or more parameters selected from the discharge timing are controlled, thereby controlling the heat transfer coefficient. That is, in the present invention, it is not always necessary to provide three types of valves, that is, the on-off valve 14, the flow rate adjusting valve 15, and the pressure adjusting valve 16, and the function can be achieved by one valve. However, by providing three types of valves, that is, the on-off valve 14, the flow rate adjusting valve 15, and the pressure adjusting valve 16, the parameters can be easily controlled. It is desirable to provide a type of valve.
The valve may be built in the mold close to the refrigerant discharge port 12 in order to keep the responsiveness good. However, it takes time to disassemble the mold every time the valve is adjusted. It is desirable to install in.

Further, as described above, the present invention controls one or more parameters selected from the refrigerant discharge amount Q, the discharge flow rate U, the discharge pressure P, the discharge time T, and the discharge timing by at least one valve. Thus, the heat transfer coefficient α by the refrigerant discharge is controlled. If this control is performed for each refrigerant discharge port, the heat transfer of the cooling by the refrigerant discharge from the plurality of refrigerant discharge ports provided on the mold surface is performed. The coefficient α can be freely changed, and the strength of each part of the material to be molded can be arbitrarily controlled. Therefore, the metal plate material 1 is successively reduced in strength without causing local thinning or breaking. Thus, the elongation and thickness of each part of the metal plate material can be freely controlled.
Furthermore, when forming a columnar press product, moldability can be improved by grouping and controlling the refrigerant discharge from a plurality of refrigerant discharge ports in a positional relationship where the punch push-in amount is the same. It is possible.

Further, as shown in FIGS. 5 and 6, by forming a plurality of refrigerant recovery ports 17 on the molding surface of the mold and disposing a refrigerant recovery pipe 18 communicating with the refrigerant recovery port 17 inside the mold. The refrigerant discharged to the metal plate 1 can be efficiently recovered. Furthermore, the cooling efficiency can be improved by recovering the refrigerant from the refrigerant recovery pipe 18 by suction means such as a vacuum generator. This is because the refrigerant that has not been vaporized adheres to or accumulates along the molding surface of the mold, for example, on the bottom of the protrusion 19 described later, and contributes to cooling in the adhering part. This is because, when the refrigerant is newly discharged, the heat transfer coefficient α at the adhering portion or the like is lowered as compared with the case where the refrigerant does not remain. For this reason, after the refrigerant is discharged, it is desirable to collect the refrigerant that has not been vaporized by a suction means such as a vacuum generator, thereby improving the control of the cooling efficiency and the heat transfer coefficient α.
The refrigerant recovery port 17 and the refrigerant recovery tube 18 can be formed by a method similar to the method of forming the refrigerant discharge port 12 and the refrigerant supply tube 13 described above. Moreover, the refrigerant | coolant collection | recovery port 17 may be provided in the top part of the punch 4, and may be provided in both a vertical wall part and a top part. The same applies to the case where the refrigerant recovery port 17 is provided in the plate holder 6. On the other hand, when the coolant recovery port 17 is provided in the upper die 3 or the pad 5, it may be provided at the bottom or at both the vertical wall and the bottom, but is provided at the vertical wall. Thus, the refrigerant discharged to the molding material can be efficiently recovered.

Furthermore, as shown in FIGS. 5 and 6, if a plurality of protrusions 19 are formed on the molding surface of the mold, the contact area between the mold and the metal plate 1 is reduced, and due to heat removal from the mold during press molding. It is possible to suppress overcooling of the metal plate material that is the molding material. Conversely, by increasing the contact area between the material to be molded and the refrigerant, a large amount of refrigerant can be brought into contact with the portion to be rapidly cooled, and the cooling rate can be increased as required. Furthermore, when the refrigerant is discharged at the bottom dead center after the completion of molding, it becomes easy to circulate the refrigerant in the gap between the protrusion 19 and the metal plate 1, and the cooling efficiency between the mold and the metal plate 1 is improved. Can be increased. In addition to this, the thermal distortion of the mold can be reduced and the processing accuracy can be increased.
5 and 6 is a cylindrical shape provided at a predetermined interval on the molding surface of the mold, but the horizontal cross section has a circular shape, a polygonal shape, or a star shape. It is desirable that the shape of the vertical cross section is either rectangular or trapezoidal, and may be hemispherical.

The protrusion 19 can exert the above-described effect if it is formed on at least one of the molding surfaces of the mold, but may be formed on both molding surfaces. Further, it may be provided on a part of the molding surface of the mold or on the entire surface.
The protrusion 19 may be formed as it is on the surface of the molding surface. However, depending on the molding conditions, the shape of the protrusion may be transferred to the molded product, which may impair the surface properties of the molded product. The mold part around the part is removed to form a dent, or as shown in FIG. 7, a dent having a depth matching the height of the projection part is formed in the mold part at the projecting part forming position, and the dent is projected into the dent. It is desirable to form the portion 19.

The area ratio of the protrusions 19 is preferably 1 to 90% of the molding surface of the mold. If it is less than 1%, the shape of the protrusions can be easily transferred to the material to be molded, and if it exceeds 90%, the gap between the protrusions 19 is narrow, the pressure loss increases, and the refrigerant cannot be charged or flown.
When the horizontal cross-sectional shape of the protrusion is circular, the diameter of the protrusion 19 is preferable. When the protrusion is a polygonal shape or a star shape, the diameter of the circumscribed circle of the protrusion is preferably 10 μm to 5 mm. When the diameter of the protrusion or the circumscribed circle is less than 10 μm, the wear of the protrusion is great, and the effect cannot be exhibited over a long period of time, and when it exceeds 5 mm, cooling cannot be performed uniformly.
As for the height of the projection part 19, it is desirable that they are 5 micrometers-1 mm. If the height of the protrusion is less than 5 μm, the gap between the molding material and the molding material is too small, so that it is difficult to circulate the refrigerant between the mold and the molding material, and if it exceeds 1 mm, the gap becomes excessive. The amount of processing increases and is not economical.

The protrusion 19 can be formed by electrolytic processing, chemical etching, electric discharge processing, plating, or the like.
In chemical etching, a visible light curable photosensitive resin is applied to the mold surface, dried, then covered with a mask that blocks visible light, irradiated with visible light, the irradiated part is cured, and a resin other than the cured part is applied. This is a method of removing with an organic solvent. For example, the mold surface may be immersed in an etching solution such as a sodium chloride aqueous solution for about 1 to 30 minutes and etched. The diameter or pitch of the protrusions can be appropriately selected depending on the shape of the mask that blocks visible light, and the height of the protrusions can be appropriately adjusted depending on the etching time.
Electric discharge machining is a machining method in which a copper electrode having a concave portion in which a target protrusion shape is inverted as a surface pattern is placed facing a mold, a current peak value and a pulse width are changed, and a DC pulse current is passed. . A preferable current value is 2 to 100 A, a pulse width is 2 to 1000 μsec, and the current value may be appropriately adjusted according to the mold material and the desired protrusion shape.
In the case of the plating method, in order to make the diameter of the hemispherical protrusion 10 μm or more, the thickness of the plating is preferably 10 μm or more, and the upper limit is preferably 80 μm or less in order to prevent peeling. The plating layer can be formed at a predetermined bath temperature and current density after alkaline degreasing and electrolytic etching in which a mold is used as an anode in a plating solution. In the case of chromium plating, the current density is about 1 to 200 A / dm ^{2 in the} chromium plating solution, and the bath temperature is about 30 to 60 ° C. In the case of NiW plating, the current density is 1 to 100 A / dm ^{2 in the} NiW plating solution. When the bath temperature is about 30 to 80 ° C., a plating layer having a thickness of 10 to 80 μm can be provided. In order to form a plating layer having a hemispherical projection shape, for example, after increasing the current density stepwise, plating may be performed at a constant current density.

(4) Next, the control device 23 that controls at least one of the on-off valve 14, the flow rate adjustment valve 15 and the pressure adjustment valve 16 provided in the refrigerant supply pipe 13 will be described.
The control device 23 is not particularly limited as long as it can control the opening / closing of the on / off valve 14, the flow rate adjusting valve 15 and the pressure adjusting valve 16 provided in the refrigerant supply pipe 13, and can be mechanical or electronic. Regardless of the target means, or a means in which these are combined. For example, by employing a relay switch for these valve mechanisms and controlling the opening and closing (on / off) of the relay switch by a computer (computer), the refrigerant discharge from the refrigerant discharge port 12 communicating with the refrigerant supply pipe 13 Specifically, the heat transfer coefficient α at the refrigerant discharge port 12 can be adjusted.

Further, since it is desirable to synchronize the refrigerant discharge timing from the refrigerant discharge port 12 with the punch push-in amount (also referred to as stroke position), measurement data indicating the punch push-in amount or a signal corresponding thereto is input to the control device 23. It is desirable to do. Thereby, it is possible to control the on-off valve 14, the flow rate adjustment valve 15, and the pressure adjustment valve 16 provided in the refrigerant supply pipe 13 in synchronization with the punch push-in amount, and communicate with the refrigerant supply pipe 13. The refrigerant discharge from the refrigerant discharge port 12 can be synchronized with the punch push-in amount.
In the case of forming a columnar press product, the formability is improved by making the refrigerant discharge at the plurality of refrigerant discharge ports 12 in the positional relationship where the punch push-in amount is the same, in this case, It is desirable to make the control of the on-off valves and the like of the refrigerant supply pipe 13 communicating with the plurality of refrigerant discharge ports 12 in the positional relationship where the punch push-in amount is the same.

As the refrigerant used in the present invention, water, polyhydric alcohols, polyhydric alcohol aqueous solution, polyglycol, mineral oil having a flash point of 120 ° C. or higher, synthetic ester, silicon oil, fluorine oil, from flame retardancy and corrosiveness, Either a grease having a dropping point of 120 ° C. or higher, mineral oil, or a water emulsion in which a surfactant is blended with a synthetic ester may be used, or a mixture thereof may be used.
The refrigerant may be liquid or gas. When a gas is used as the refrigerant, the heat transfer coefficient is low, so that it is limited to a case where the processing is not relatively severe, or a case where the martensite transformation or the bainite transformation is not performed. Also, it is desirable to use nitrogen, CO ₂ , or inert gas with low activity in order to avoid surface oxidation. Further, when the refrigerant is a gas, it does not remain attached to the molded product or the hot press molding apparatus, so that there is an effect that unnecessary dirt and rust are hardly generated.

As described above, according to the present invention, the temperature of each part of the metal plate material is measured by the temperature measuring means 24 before the press starts, and the temperature of each part of the metal plate material is measured by one or both of the heating means 25 and the cooling means 26. Since the press molding is started after the temperature is set in accordance with the strength of each part of the press-formed product, the strength of each part of the press-formed product that cannot be realized by the prior art can be set accurately and arbitrarily.
Furthermore, since the cooling rate of each part of the metal plate material is controlled by using a mold having a refrigerant discharge function during molding or after molding, or after molding, each part of the press molded product is more accurately Can be set accurately and arbitrarily.

  In addition, another one of the problems to be solved of the present invention is a hot press molding method for adjusting the strength of the press-formed product 30 by a hot molding and cooling process using a mold for the heated metal plate 1, In the hot press forming method according to the present invention, each part of the metal plate material is previously prepared before the start of press forming. Is measured by the temperature measuring means 24, and the temperature of each part of the metal plate material is set to a temperature corresponding to the degree of processing of each part of the press-formed product by one or both of the heating means 25 and the cooling means 26. Since press molding is started, the strength of the portion where elongation occurs and breakage can be increased in advance, and as a result, load distribution in the portion where elongation occurs Rukoto can, it is possible to prevent the break.

The position of the portion where the plate thickness decreases due to elongation, that is, the position of the metal plate material that should be temperature-set according to the degree of processing, can be specified by experiments conducted in advance. Therefore, for example, a temperature distribution having a form as shown in FIG. 9D is formed in a part with a high degree of processing specified by an experiment performed in advance, and the temperature of the part with a high degree of processing is set to the temperature of another part. By lowering the strength further and lowering the strength, as shown in FIG. 9 (f), when the press molding is started, a portion having a lower strength than the portion where the strength is increased is elongated, thereby preventing breakage. be able to.
9D and FIG. 9E, the temperature adjustment region 34 is measured by one or both of the heating unit 25 and the cooling unit 26 after the temperature measurement unit 24 measures the temperature of each part of the metal plate material. For example, if the temperature of the temperature adjustment region 34 is set lower than the surrounding region, the strength in the temperature adjustment region 34 is higher than that of the other portions. When molding is started, as shown in FIG. 9 (f), a portion having a lower strength than the portion where the strength has been increased extends, so that breakage can be prevented.

  Further, the form of the temperature distribution to be applied to the metal plate 1 before the start of pressing is not limited to the form shown in FIG. 9 (d), and a temperature distribution corresponding to the degree of processing of the press-formed product 30 is formed. Is desirable. For example, in the press-formed product 30 shown in FIG. 9B, the vertical wall portion 32 is a portion having the greatest degree of processing, but the metal plate material corresponding to this is shown in FIG. 9E. If the temperature distribution of the form, that is, the temperature distribution in which the high-strength and low-strength portions appear alternately, load concentration on the part with a high degree of processing, in other words, the part where elongation occurs Can be prevented, and breakage can be prevented.

  Furthermore, not only the temperature setting before the press start by the said method but the formability can be further improved by controlling the cooling rate of each part of the metal plate material after the start of forming. Specifically, the temperature of each part of the metal plate material is measured in advance by the temperature measuring unit 24 before the press molding is started, and the temperature of each part of the metal plate material is press-molded by one or both of the heating unit 25 and the cooling unit 26. Press molding is started after setting the temperature according to the processing degree of each part of the product, and after the molding starts, cooling of each part of the metal plate material is performed by coolant discharge from a predetermined cooling means, for example, a mold having a coolant discharge function. By controlling the speed, it is possible to more accurately control the load distribution in the portion where the elongation occurs, and as a result, it is possible to further improve the draw moldability and foam moldability by hot pressing.

Next, an embodiment of the present invention will be described. The conditions of the present embodiment are one condition adopted for demonstrating the feasibility and remarkable effects of the present invention, and the present invention satisfies this one condition. It is not limited.
Table 1 shows the conditions of the examples, and Table 2 shows the results. This example shows an example in which the cylindrical drawn product shown in FIG. 8 (b) is formed using the hot press forming apparatus 2 shown in FIG. A 0.2% C steel plate (equivalent to an initial breaking strength of 500 MPa) having a thickness of 1.6 mm and a radius of 140 mm shown in FIG. 8A heated to 900 ° C. (retention time 5 minutes) was used. The press-formed product 30 includes a top portion 31, a vertical wall portion 32, and a flange portion 33, and the height of the vertical wall portion 32 is 20 mm.

The die uses a die 3 and a plate retainer 4 with a refrigerant discharge function. The die 3 has a vertical wall portion and a bottom portion, and the plate retainer 4 has a hole diameter of 2 mm and a pitch of 5 mm evenly at the top. The arranged refrigerant discharge port 12 is formed.
Further, the mold forming surfaces of Invention Examples 2 to 5 are provided with protrusions 19 having an area ratio of 50%, a height of 1 mm, a diameter of 2 mm, a horizontal cross-sectional shape that is circular, and a vertical cross-sectional shape that is rectangular. Yes. The punch 4 had a diameter of 70 mm and the molding speed was 10 mm / sec.

Regarding the refrigerant discharge capacity, the valve is adjusted so that the heat transfer coefficient α is either 1000 or 3000 kcal / m ² hr ° C. Note that the α heat transfer coefficient of the case without refrigerant discharge, if the mold surface does not form a protrusion 19 1000kcal ^{/ m} 2 hr ℃, when formed is 200kcal ^{/ m} 2 hr ℃.
A radiation thermometer is used to measure the temperature of each part of the steel sheet, the representative points (ac) of each part (A to C) in FIG. 8 (a) are measured, and the temperature at each point is ± 10 ° C. of the specified temperature. At that point, the indentation started.

First, for the comparative example, for the comparative example 1 in which no protrusion is formed on the mold forming surface and the press start temperature is not controlled and the refrigerant is not discharged, the pass rate at the time of manufacturing 500 pieces remains at 80%. I could not satisfy the sex. Further, in Comparative Example 2 in which the press start temperature was controlled, the moldability could be satisfied, but the bottom dead center retention time was long and the productivity could not be satisfied.
On the other hand, Inventive Example 1 is a product in which the press start temperature and the cooling rate after the press start are controlled to be constant in each part of the molded product, but the molded product has a uniform strength that can satisfy the moldability, productivity and strength. Could get.
Inventive examples 2 and 3 are the ones in which the start temperature of each part of the steel sheet is varied and the cooling rate is controlled in the same manner. I was able to confirm. Inventive Example 4, contrary to Inventive Examples 2 and 3, the press start temperature of each part of the steel sheet is kept constant and the cooling rate is controlled to be different. It was confirmed that press-formed products 30 having different sizes were obtained.
From the above, if the press molding is started after changing the temperature of the metal plate 1 for each part of the molded product, it is possible to obtain the press-formed product 30 having different strengths for each part of the molded product, and during and after the molding. It was confirmed that if the cooling rate of the metal plate material 1 in either one or both of them is made different for each part of the molded product, it is possible to obtain press-formed products 30 having different strengths for each part of the molded product.

It is an example of the CCT curve of carbon steel which shows that the structure of a steel plate can be controlled by controlling the cooling start temperature and cooling rate of a steel plate. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic explanatory drawing of the hot press molding apparatus which concerns on this invention, (a) is the figure which described the die holder and the punch holder, (b) abbreviate | omitted the die holder and the punch holder in order to clarify the structure of an apparatus. FIG. It is a schematic explanatory drawing which shows the principle of this invention typically. It is explanatory drawing which shows the metal mold | die which has the refrigerant | coolant discharge function which concerns on this invention, and is sectional drawing at the time of providing the said function in the punch. It is explanatory drawing which shows an example of the metal mold | die which concerns on this invention, and is a figure which shows the surface of the metal mold | die which formed the refrigerant | coolant discharge port, the refrigerant | coolant collection port, and the projection part. It is sectional drawing which shows an example of the metal mold | die which concerns on this invention, and is a figure which shows the cross section of the metal mold | die which formed the refrigerant | coolant discharge port, the refrigerant | coolant collection port, and the projection part. It is sectional drawing which shows another example of the metal mold | die which concerns on this invention, and is a figure which shows the cross section of the metal mold | die which formed the refrigerant | coolant discharge port, the refrigerant | coolant collection port, and the projection part. It is explanatory drawing which shows an example of a press molded product, (a) is explanatory drawing which shows a to-be-molded material, (b) shows the molded product by a cylindrical aperture drawing. It is a mimetic diagram showing one embodiment concerning the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal plate material 2 Hot press molding apparatus 3 Dies 4 Punch 5 Pad 6 Board presser 7 Die base (upper mold) 8 Die base (lower mold)
DESCRIPTION OF SYMBOLS 9 Die holder 10 Punch holder 11 Die set 12 Refrigerant discharge port 13 Refrigerant supply pipe 14 On-off valve 15 Flow rate adjustment valve 16 Pressure adjustment valve 17 Refrigerant recovery port 18 Refrigerant recovery pipe 19 Protrusion part 20 Core 21 Seal 22 Mold whole cooling part 23 Control Device 24 Temperature Measuring Unit 25 Heating Unit 26 Cooling Unit 30 Press Molded Product 31 Top 32 Vertical Wall 33 Flange 34 Temperature Control Region

Claims (12)

In a hot press forming method in which the strength of a press-formed product is adjusted by a hot forming and cooling process using a mold for a heated metal plate material, the temperature of each part of the metal plate material is measured, and either the heating means or the cooling means Alternatively, the hot press forming method is characterized in that the press forming is started after the temperature of each part of the metal plate material is set to a temperature corresponding to the strength of each part of the press molded product.
In a hot press forming method in which the strength of a press-formed product is adjusted by a hot forming and cooling process using a mold for a heated metal plate material, the temperature of each part of the metal plate material is measured, and either the heating means or the cooling means Alternatively, a hot press forming method characterized in that the press forming is started after the temperature of each part of the metal plate material is set to a temperature corresponding to the degree of processing of each part of the press molded product.
In a hot press forming method in which the strength of a press-formed product is adjusted by a hot forming and cooling process using a mold for a heated metal plate material, the temperature of each part of the metal plate material is measured, and either the heating means or the cooling means Or, by both, the temperature of each part of the metal plate material is set to a temperature according to the strength of each part of the press-molded product, and then press molding is started, and after the start of molding, either or both during molding and after molding, Control the cooling rate of each part of the metal plate by discharging refrigerant from multiple refrigerant outlets on the mold surface, or discharging refrigerant from multiple refrigerant outlets on the mold surface and collecting refrigerant from the refrigerant recovery port A hot press molding method characterized in that:
In a hot press forming method in which the strength of a press-formed product is adjusted by a hot forming and cooling process using a mold for a heated metal plate material, the temperature of each part of the metal plate material is measured, and either the heating means or the cooling means Or, by both, the temperature of each part of the metal plate material is set to a temperature according to the degree of processing of each part of the press-molded product, and then press molding is started.After molding, either or both during molding and after molding, The cooling rate of each part of the metal plate material can be adjusted by discharging the refrigerant from the plurality of refrigerant discharge ports provided on the mold surface, or discharging the refrigerant from the plurality of refrigerant discharge ports provided on the mold surface and collecting the refrigerant from the refrigerant recovery port. A hot press molding method characterized by controlling.
The refrigerant discharge is controlled by one or more parameters selected from the refrigerant discharge amount, discharge flow velocity, discharge pressure, discharge time, and discharge timing, and for each refrigerant discharge port or from a plurality of refrigerant discharge ports The hot press molding method according to claim 3 or 4, wherein the refrigerant discharge is grouped and controlled for each group.
The hot press forming method according to any one of claims 1 to 5, wherein the metal plate is a steel plate.
The hot press forming method according to claim 6, wherein the steel sheet is a steel sheet that undergoes martensitic transformation or bainite transformation.
In a hot press forming device that forms a heated metal sheet using a mold, the temperature of each part of the metal sheet is measured, and the temperature of each part of the metal sheet is increased to the temperature corresponding to the strength or degree of processing of each part of the press molded product. It comprises heating means for raising the temperature, cooling means for cooling the temperature of each part of the metal plate material to a temperature corresponding to the strength or degree of processing of each part of the press-molded product, and a mold for forming the metal plate material Hot press forming equipment.
In a hot press forming device that forms a heated metal sheet using a mold, the temperature of each part of the metal sheet is measured, and the temperature of each part of the metal sheet is increased to the temperature corresponding to the strength or degree of processing of each part of the press molded product. Heating means for raising the temperature, cooling means for cooling the temperature of each part of the metal plate material to a temperature corresponding to the strength or degree of processing of each part of the press-formed product, a plurality of refrigerant discharge ports on the surface, and each refrigerant discharge port inside A mold having a refrigerant supply pipe in communication and provided with at least one of an on-off valve, a flow rate adjustment valve and a pressure adjustment valve; and an on-off valve, a flow rate adjustment valve and a pressure adjustment valve provided on the refrigerant supply pipe. A hot press molding apparatus comprising: an apparatus for controlling refrigerant discharge from each refrigerant discharge port by controlling at least one.
The hot press molding apparatus according to claim 9, wherein an opening / closing valve, a flow rate adjustment valve, and a pressure adjustment valve of the refrigerant supply pipe are installed in a die set.
The hot press according to claim 9 or 10, wherein the mold is a mold having a plurality of refrigerant recovery ports on a surface thereof, and a refrigerant recovery pipe communicating with each of the refrigerant recovery ports arranged therein. Molding equipment.
The mold according to any one of claims 8 to 11, wherein the mold has a plurality of protrusions having an area ratio of 1 to 90%, a diameter or a circumscribed circle diameter of 10 µm to 5 mm, and a height of 5 µm to 1 mm on the surface. The hot press molding apparatus according to claim 1.

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