JP2011000617A - Device and method for hot press-forming metallic pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and a method for hot press-forming a metallic pipe by which strength in each part of a press formed article is set correctly, optionally and in a short time.SOLUTION: The device for hot press-forming a heated metallic pipe by using a die, is characterized in that a plurality of coolant discharging ports 10 are formed on the forming surface of the die 2, coolant supply tubes 11 which are communicated with respective coolant discharging ports 10 are formed inside the die 2 and a coolant is discharged from a part or the whole of the coolant discharging ports 10 toward the outside of the metallic pipe 1 with the die clamped. In the method for hot press-forming by which the heated metallic pipe is hot press-formed by using the die, the plurality of coolant discharging ports 10 are formed on the forming surface of the die 2, the coolant supply tubes 11 which are communicated with the respective coolant discharging ports 10 are formed in the inside of the die 2 and the coolant is discharged from a part or the whole of the plurality of the coolant discharging parts 10 toward the outside of the metallic pipe 1 with the die clamped.

Description

  The present invention relates to a hot press molding apparatus and method for molding a heated metal tube using a mold or a mold and a shaft pressing device, and in particular, a metal capable of accurately and arbitrarily setting the strength of each part of a press molded product. The present invention relates to a hot press forming apparatus for a tube and a method thereof.

Metal tube 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 technique 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 manufacturing field of automobile parts and the like, the metal tube is filled into the mold, and the metal tube is inflated by applying water pressure, and at the same time, the metal tube is axially pushed in the length direction to make the metal tube complicated. Attention has been focused on hydroform molding technology for molding into various shapes.
Hydroform molding technology has been able to integrally form parts that were previously welded and combined together, leading to a reduction in the number of parts and the elimination of processes and welding. It is an indispensable important technology.

However, hydroforms require complex and advanced control during molding. This is because there are very many parameters to be controlled. Moreover, since hydroforming is performed in a metal mold | die, it is because an actual deformation | transformation cannot be seen.
For example, the metal tube may rupture or buckle if the hydraulic pressure or the shaft pressing timing is incorrect. Furthermore, appropriate conditions change when the material and lubrication change. Specifically, in hydrofoam, there is a problem that wrinkles and cracks occur with molding if the amount of swelling is excessively increased. Similarly, when the amount of bulging is excessively increased, there is a problem that the wall thickness of the bulged portion is reduced, resulting in insufficient strength or breakage.

For this reason, in order to prevent the generation of wrinkles and cracks associated with molding, a method for controlling the width of the bulging cavity by moving the mold is disclosed (for example, see Patent Document 1). Then, means for moving the mold is required, and the apparatus configuration becomes more complicated.
Alternatively, a numerical analysis technique using a finite element method (FEM) for simulating how a material to be deformed in a mold has been developed, and a relatively accurate simulation is possible. However, in order to find appropriate processing conditions, it is necessary to accumulate a large amount of data necessary for the analysis.

  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 in each part of the body to achieve the performance, plate thickness and wall thickness, And it is necessary to set the strength in detail, and the number of parts constituting the body has reached several hundred.

For this reason, in recent automobile parts such as bumpers, pyralin forces, center pillars, and suspension parts, there is a press material that combines and integrates multiple metal pipes with different thicknesses and strengths by welding, that is, tailored tubes. It is used. (For example, refer to Patent Document 2).
The tailored tube has an excellent feature that the characteristics of one metal tube can be partially changed according to the purpose. For example, a high-strength tube is applied only to a portion 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 tube having a thickness and strength suitable for the purpose is selected and joined together by welding, the strength of each part of the press-formed product can be set accurately and arbitrarily 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 tube 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 tube is joined and integrated by welding, The manufacture of tailored tubes requires advanced welding techniques.
That is, unless a high-level welding technique is applied, fractures are likely to occur in the welded portion when formed using hydroform. And if the intensity | strength of a welding part cannot be ensured, the outstanding characteristic of a tailored tube or hydroform cannot also be exhibited. Moreover, in the current situation where the strength of automobile parts is increasing, it is naturally extremely necessary that an increasingly advanced welding technique is required.

  As described above, various improvements have been attempted for the hydroform molding technology, and the hydroform molding technology can achieve both high strength and excellent dimensional accuracy that could not be realized by the conventional cold press molding method. This can be said to be a press molding technology.

  However, all of the above technologies, including tailored tubes, locally change the strength of the press-molded product, that is, the strength of specific parts such as parts that require higher strength and parts that require post-processing. However, it is set in advance before press forming, and the strength of each part of the press-formed product cannot 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.

  In addition, press products in recent years, especially automobile parts, are required to have higher strength from the viewpoint of weight reduction. For example, it is also required to achieve high strength by martensitic transformation or bainite transformation by heating a metal tube to an austenite region and quenching it by a predetermined cooling process. In the hydroform molding technique, a closed section, large R, and simple shape can be molded in the 980 MPa class, but it is currently difficult to secure a higher strength.

  In other words, as described above, the hydroform molding technology can be said to be a molding method that can achieve both high strength and excellent dimensional accuracy, which could not be realized by the conventional cold press molding method, but progress in increasing strength of products has progressed. Today, it is not only necessary to satisfy the above characteristics, but as a new technology to replace hydroform, the strength of each part of the press-formed product can be accurately and arbitrarily set according to the purpose and in a short time without impairing productivity. The development of molding technology that can be set is strongly desired in the industry.

Japanese Patent Laid-Open No. 2002-153917 JP 2001-321844 A

The problem to be solved by the present invention is to provide a hot press forming apparatus and method for a metal tube capable of setting the strength of each part of a press-formed product accurately, arbitrarily, and in a short time.
The term “arbitrary” as used herein includes making the strength of the entire press-formed product uniform, and also making the strength of only a portion that needs to be made stronger. Examples of the latter include increasing the strength of pipe ends that have been expanded, bent parts, or parts that are heavily worn. Alternatively, it is also included that the inner surface of the metal tube (hereinafter referred to as the inner surface) and the outer surface of the metal tube (hereinafter referred to as the outer surface) have different strengths.

  In order to solve the above-mentioned problems, the present inventor paid attention to a hot press forming method as a method to replace the conventional cold press forming method and hydroform forming technology, and obtained the following technical knowledge.

(A) Since the hot press molding method press-molds a metal tube as a material to be molded at a high temperature, the metal tube with reduced material strength deforms straight along the molding surface of the mold, Even complex shapes can be molded with excellent dimensional accuracy. In addition, after molding, it is cooled rapidly due to the effect of removing heat from the mold, so that no spring bag is generated, it has excellent shape freezing property, and the dimensional accuracy of the pressed product can be improved.
Therefore, it is difficult to manufacture a press product with a complicated shape due to a decrease in shape freezing due to the occurrence of springback, etc., numerical analysis using a finite element method (FEM), etc. It is possible to sufficiently replace the hydroform molding technology that requires complex and advanced control of the above, and the following technical effects are expected.

(B) When the hot press forming method is adopted as the forming method of the metal tube, when the metal tube is a steel tube, the metal tube is heated to the austenite region and held in the mold after the press forming. Strengthening by martensitic transformation or bainite transformation can be achieved by rapid cooling.
Therefore, in order to increase the strength further and shorten the mold holding time from the viewpoint of productivity, a plurality of refrigerant discharge ports are formed on the molding surface of the mold, and each refrigerant discharge port is formed inside the mold. By forming a communicating refrigerant supply pipe and discharging the refrigerant from the refrigerant outlet toward the outer surface of the metal tube while being clamped after molding, the strength of the outer surface of the metal tube can be increased in a short time.

(C) Although one end of the metal tube may be expanded using a shaft pressing device in addition to the mold, a plurality of refrigerant discharge ports are formed on the molding surface of the shaft pressing device, and the shaft If a refrigerant supply pipe communicating with each refrigerant outlet is formed inside the pushing device, and the refrigerant is discharged from the refrigerant outlet toward the inner face of the metal pipe while being clamped after molding, the inner surface of the metal pipe is strengthened. Can be achieved in a short time.
In addition, since the material strength of the metal tube heated to a high temperature is reduced, when the end portion is expanded using a shaft pressing device, the end portion can be easily increased in thickness.

(D) Then, a plurality of refrigerant discharge ports are formed on the molding surfaces of both the mold and the shaft pressing device, and a refrigerant supply pipe communicating with each refrigerant discharge port is formed inside both the mold and the shaft pressing device. If the coolant is discharged from both the coolant discharge ports toward the inner surface and the outer surface of the metal tube while being clamped after molding, the strength of the entire metal tube can be increased in a shorter time. If the refrigerant is discharged only on the inner surface or the refrigerant speed on the inner surface is made larger than that on the outer surface, the strength of the inner surface becomes higher than that on the outer surface. Conversely, if the refrigerant is discharged only on the outer surface or the refrigerant speed on the outer surface is made larger than that on the inner surface, the strength of the outer surface becomes higher than that on the inner surface.

  Based on the above knowledge, the present inventor has conceived a hot press forming apparatus and method for a metal tube capable of setting the strength of each part of a press-formed product accurately, arbitrarily, and in a short time. The gist is as follows.

(1) In a hot press molding apparatus for press-molding a heated metal tube using a mold, a plurality of refrigerant discharge ports are formed on the molding surface of the mold, and each refrigerant discharge port is formed inside the mold. A hot press molding apparatus characterized in that a refrigerant supply pipe communicating with the pipe is formed and the refrigerant is discharged from a part or all of the plurality of refrigerant discharge ports toward the outer surface of the metal pipe while being clamped.

(2) In a hot press molding apparatus for press-molding a heated metal tube using a mold and a shaft pressing device, a plurality of refrigerant discharge ports are formed on the molding surface of the shaft pressing device, and the interior of the shaft pressing device is The hot press is characterized in that a refrigerant supply pipe communicating with each refrigerant outlet is formed, and refrigerant is discharged from a part or all of the plurality of refrigerant outlets toward the inner surface of the metal pipe while being clamped Molding equipment.

(3) In a hot press molding apparatus for press-molding a heated metal tube using a mold and a shaft pressing device, a plurality of refrigerant discharge ports are formed on the molding surface of the mold, and inside the mold A refrigerant supply pipe communicating with each refrigerant discharge port is formed, a plurality of refrigerant discharge ports are formed on the molding surface of the shaft pushing device, and a refrigerant supply pipe communicating with each refrigerant discharge port is formed inside the shaft pushing device. A hot press forming apparatus, wherein the refrigerant is discharged from a part or all of the plurality of refrigerant outlets toward one or both of the outer surface and the inner surface of the metal tube while being clamped.

(4) A plurality of refrigerant recovery ports are formed on the molding surface of the mold, and a refrigerant recovery pipe communicating with each refrigerant recovery port is formed inside the mold. The hot press molding apparatus according to any one of to (3).

(5) A plurality of refrigerant recovery ports are formed on the molding surface of the shaft pressing device, and a refrigerant recovery pipe communicating with each refrigerant recovery port is formed inside the shaft pressing device. The hot press molding apparatus according to 2) or (3).

(6) In a hot press molding method in which a heated metal tube is press-molded using a mold, a plurality of refrigerant discharge ports are formed on the molding surface of the mold, and each refrigerant discharge port is formed inside the mold. A hot press molding method characterized in that a refrigerant supply pipe communicating with the pipe is formed, and the refrigerant is discharged from some or all of the plurality of refrigerant discharge ports toward the outer surface of the metal pipe while being clamped.

(7) In a hot press molding method in which a heated metal tube is press-molded using a mold and a shaft pressing device, a plurality of refrigerant discharge ports are formed on the molding surface of the shaft pressing device, and the interior of the shaft pressing device is The hot press is characterized in that a refrigerant supply pipe communicating with each refrigerant outlet is formed, and refrigerant is discharged from a part or all of the plurality of refrigerant outlets toward the inner surface of the metal pipe while being clamped Molding method.

(8) In a hot press molding method in which a heated metal tube is press-molded using a mold and a shaft pressing device, a plurality of refrigerant discharge ports are formed on the molding surface of the mold, A refrigerant supply pipe communicating with each refrigerant discharge port is formed, a plurality of refrigerant discharge ports are formed on the molding surface of the shaft pushing device, and a refrigerant supply pipe communicating with each refrigerant discharge port is formed inside the shaft pushing device. A hot press forming method, wherein the refrigerant is discharged from a part or all of the plurality of refrigerant outlets toward one or both of the outer surface and the inner surface of the metal tube while being clamped.

(A) According to the hot press molding apparatus and method according to the present invention having a coolant discharge mechanism in the mold, the metal tube as the molding material is press molded in a state of being heated to a high temperature, so that the material strength is reduced. The metal tube deforms straight along the molding surface of the mold, and can be molded with excellent dimensional accuracy even if it has a complicated shape. And after shaping | molding, since it cools rapidly by the refrigerant | coolant discharge from a metal mold | die, a spring bag does not generate | occur | produce, it is excellent in shape freezing property, and it can improve the dimensional accuracy of a press product.

(B) According to the hot press forming apparatus and the method thereof according to the present invention having the refrigerant discharge mechanism in the shaft pressing device, the end portion is expanded in a state where the metal tube as the molding material is heated to a high temperature. The end portion of the metal pipe having a reduced thickness can be easily expanded and the thickening process can be performed. Therefore, even a complicated shape can be formed with excellent dimensional accuracy. And after shaping | molding, since it cools rapidly by the refrigerant | coolant discharge from a shaft pushing apparatus, a spring bag does not generate | occur | produce, it is excellent in shape freezing property, and can improve the dimensional accuracy of a press product.

(C) According to the hot press molding apparatus and method according to the present invention having the refrigerant discharge mechanism in both the mold and the shaft pressing device, the metal tube as the molding material is press-molded in a heated state. The metal tube with reduced material strength can be deformed straight along the molding surface of the mold, and the end of the metal tube with reduced material strength can be easily expanded and the wall thickness increased. Therefore, even a complicated shape can be formed with excellent dimensional accuracy. And since it cools rapidly after shaping | molding by the refrigerant | coolant discharge from a metal mold | die and a shaft pushing apparatus, a spring bag does not generate | occur | produce, it is excellent in shape freezing property, and can improve the dimensional accuracy of a press product.

(D) Since the above refrigerant discharge mechanism has a plurality of refrigerant discharge ports, it is possible to increase the strength of only the discharged portion by discharging the refrigerant from some of the refrigerant discharge ports, or all the refrigerants By discharging the refrigerant from the discharge port, the strength of the entire press-formed product can be increased uniformly.

(E) Since the above-described refrigerant discharge mechanism is formed on the molding surface of one or both of the mold and the shaft pressing device, the metal tube can be rapidly cooled while being clamped. This contributes to shortening of the mold holding time, thereby improving the productivity.

It is a figure which shows the state which has set the metal pipe | tube to the metal mold | die. It is a figure which shows the state which is implementing the bending process by mold clamping. It is a figure which shows the state which is expanding the end part using the axial pushing apparatus. It is a figure which shows the state which has discharged | emitted the refrigerant | coolant from both refrigerant | coolant discharge ports toward the inner surface and outer surface of a metal pipe, after mold-clamping. It is a figure which shows the one aspect | mode of refrigerant | coolant discharge. It is a figure which shows an example of the bending process using a cushion and a pad, (a) is a figure which shows the state after shaping | molding, (b) at the time of the setting of a metal pipe.

Hereinafter, the best mode for carrying out the present invention will be described with reference to FIGS.
First, the molding material used in the present invention will be described. The material to be molded used in the present invention is a metal pipe 1 and can be applied to any steel pipe such as an Al-plated steel pipe, a Zn-plated steel pipe, a GI-plated steel pipe, a high-strength steel pipe, a normal steel pipe, and a stainless steel pipe.
In addition, if a steel pipe undergoes martensitic transformation or bainite transformation, the strength can be increased by quenching by refrigerant discharge, and therefore, a steel pipe 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.

Further, as the metal pipe 1 used in the present invention, (a) an electric-welded steel pipe in which a steel plate / strip steel is formed into a cylindrical shape and welded in parallel to the pipe axis direction, and (b) a thick plate is formed into a U shape by a U press (B) a spiral steel pipe that is formed into a tubular shape with an O-press and welded from the inside and outside surfaces, and (c) a spiral steel pipe that is formed by winding a wide strip steel in a spiral shape and then continuously welding the inside and outside of the seam; ) Even after the steel strip is heated, even forged welded steel pipes that have been crimped at the edge of the plate while being drawn by roll forming, (e) after heating the billet to make a hole in the center, it was subjected to a rolling mill or drawing machine A seamless steel pipe may be used.
Further, the cross-sectional shape of the metal tube 1 can be applied not only to a circle but also to any metal tube such as an ellipse or a square. Further, the present invention can also be applied to a metal tube whose cross-sectional shape changes along the longitudinal direction. Or it can apply also about a tailored tube.

Next, the heating method and heating temperature of the metal tube 1 before being set in the mold 2 will be described. The method for heating the metal tube is not particularly limited, as long as the metal tube can be heated to the A1 transformation point or higher, heating in a heating furnace, electric furnace, gas furnace, flame heating, electric heating, Any heating method such as high-frequency heating or induction heating may be used.
Moreover, even if it is an aspect which heats the whole metal tube uniformly, the aspect which heats a part of metal tube may be sufficient. Here, the heating temperature of the metal tube is preferably 600 to 1000 ° C.

  The refrigerant used in the present invention, that is, the refrigerant discharged to the metal tube 1 from the refrigerant discharge port 10 formed on the molding surface of the mold 2 or the molding surface of the shaft pushing device 3 to be described later, is flame retardant and corrosive. Water, polyhydric alcohols, polyhydric alcohol aqueous solution, polyglycol, mineral oil with a flash point of 120 ° C or higher, synthetic ester, silicone oil, fluorine oil, grease with a dropping point of 120 ° C or higher, mineral oil, synthetic ester Any of water emulsions containing a surfactant 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 cases where the processing is not relatively severe, or when martensitic transformation or 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 mold, so that there is an effect that unnecessary dirt and rust are hardly generated.

  1 to 6 are perspective views for explaining a hot press forming apparatus according to the present invention. The hot press molding apparatus according to the present invention has a plurality of coolant discharge ports 10 for discharging a coolant toward the outer surface of the metal tube 1 after being molded, as shown in FIGS. It is desirable to form on 2 molding surfaces. Similarly, as shown in FIGS. 4 to 5, it is desirable to form a refrigerant supply pipe 11 communicating with each refrigerant discharge port 10 inside the mold 2.

  The coolant discharge port 10 may be formed on the upper mold or the lower mold, but is preferably formed on both molding surfaces. Moreover, it is desirable to form a plurality of refrigerant discharge ports along the longitudinal direction so as to cover the entire longitudinal direction of the metal tube 1. Furthermore, it is desirable to form a plurality of refrigerant discharge ports so as to cover the outer surface of the metal tube so that the entire outer surface of the metal tube can be covered, that is, in the circumferential direction of the metal tube.

In this way, a plurality of refrigerant discharge ports 10 are formed on the molding surface of the mold 2, the refrigerant supply pipes 11 communicating with the respective refrigerant discharge ports are formed inside the mold, and the metal tube 1 remains clamped after molding. If the refrigerant is discharged from the refrigerant discharge port 10 toward the outer surface, the strength of the outer surface of the metal tube can be increased in a short time.
That is, according to the hot press molding apparatus according to the present invention having a coolant discharge mechanism in the mold, the metal tube, which is a material to be molded, is press-molded in a state of being heated to a high temperature. It deforms straight along the molding surface of the mold and can be molded with excellent dimensional accuracy even if it has a complicated shape. And after shaping | molding, since it cools rapidly by the refrigerant | coolant discharge from a metal mold | die, a spring bag does not generate | occur | produce, it is excellent in shape freezing property, and it can improve the dimensional accuracy of a press product. In addition, since the metal tube is rapidly cooled while being clamped, the productivity is excellent.

  As shown in FIGS. 3 to 5, as one of the metal tube forming modes, there is a case where the end portion is expanded using the shaft pressing device 3 in addition to the mold 2. It is desirable to form a plurality of refrigerant discharge ports 10 for discharging refrigerant toward the inner surface of the tube 1 on the molding surface of the shaft pressing device 3 as shown in FIG. Similarly, although not shown, it is desirable to form a refrigerant supply pipe 11 communicating with each refrigerant discharge port 10 in the shaft pushing device 3. The shaft pushing device may be arranged at both ends of the metal tube or at one end.

  As the refrigerant discharge ports 10 formed on the molding surface of the shaft pushing device 3, the refrigerant discharge directions of the respective refrigerant discharge ports 10 are set so that the refrigerant discharged from the plurality of refrigerant discharge ports can cool the entire inner surface of the metal tube 1. It is desirable to form them differently. In other words, it is desirable to form the refrigerant outlets so that their directions are different from each other.

In this way, a plurality of refrigerant discharge ports 10 are formed on the molding surface of the shaft pushing device 3, a refrigerant supply pipe 11 communicating with each refrigerant discharge port is formed inside the shaft pushing device, and the metal tube 1 is kept clamped. If the refrigerant is discharged from the refrigerant discharge port toward the inner surface of the metal tube, the strength of the inner surface of the metal tube can be increased in a short time. Further, when expanding the end portion, the material strength of the metal tube heated to a high temperature is reduced, so that the end portion can be easily increased in thickness. In addition, since the metal tube is rapidly cooled while being clamped, the productivity is excellent.
1 is a diagram showing a state in which the metal tube 1 is set in the mold 2, FIG. 2 is a diagram showing a state in which bending is performed by clamping, and FIG. FIG. 4 is a diagram showing a state in which the end portion is expanded, and FIG. 4 is a diagram showing a state in which refrigerant is discharged from both the refrigerant discharge ports 10 toward the inner surface and the outer surface of the metal tube 1 while being clamped after molding. It is. In FIG. 4, since it is complicated to show all of the drawings, a part of the refrigerant supply pipe 11 formed inside the mold 2 and the refrigerant supply pipe 11 formed inside the shaft pushing device are omitted. Yes.

  In the hot press molding apparatus that press-molds the heated metal tube 1 using the mold 2 and the shaft pressing device 3, unlike the above embodiment, a plurality of refrigerant discharge ports 10 are provided only on the molding surface of the shaft pressing device 3. It is also possible to form the refrigerant supply pipe 11 that communicates with each refrigerant discharge port only inside the shaft pushing device 3 and discharge the refrigerant only toward the inner surface of the metal pipe while being clamped. In this case, the strength of the inner surface of the metal tube can be increased in a short time.

However, in a hot press molding apparatus that press-molds a heated metal tube 1 using a mold 2 and a shaft pressing device 3, a plurality of refrigerant discharge ports 10 are formed on the molding surfaces of both the mold 2 and the shaft pressing device 3. The refrigerant supply pipes 11 communicating with the respective refrigerant discharge ports are formed inside both the mold and the shaft pressing device, and both the refrigerant discharge ports 10 are directed toward the inner surface and the outer surface of the metal tube 1 while being clamped. If the refrigerant is discharged from above, the strength of the entire metal tube can be increased in a shorter time, and this aspect is desirable.
However, also in this case, if the refrigerant is discharged only on the inner surface or the refrigerant speed on the inner surface is made larger than the outer surface, the strength of the inner surface becomes higher than the outer surface, and the refrigerant is discharged only on the outer surface or the refrigerant velocity on the outer surface is made larger than the inner surface. Needless to say, the strength of the outer surface is higher than that of the inner surface.

It is desirable to form a plurality of refrigerant discharge ports 10. For example, as described above, a plurality of refrigerant discharge ports are formed along the longitudinal direction so as to cover the entire longitudinal direction of the metal tube, and the outer surface of the metal tube is covered so as to cover the entire outer surface of the metal tube. If a plurality of refrigerant discharge ports are formed, the strength of the entire press-formed product can be made uniform by discharging the refrigerant from all the refrigerant discharge ports.
On the other hand, in order to increase the strength of the pipe end portion, the bent portion, or the heavily worn portion, the refrigerant may be discharged from a part of the refrigerant discharge ports corresponding to the portion. For example, FIG. 5 shows an embodiment in which the bent portion is made stronger, and bending and expanding are performed on an Al-plated steel pipe having a wall thickness of 2 mm and 440 MPa, and the bent portion as shown in FIG. When the refrigerant is discharged from a part of the refrigerant discharge ports corresponding to (A part), the A part of the molded product is 440 Hv and the pipe end part (B part) is 390 Hv.

The coolant discharge port 10 and the coolant supply pipe 11 communicating with the coolant discharge port 10 can be formed by mechanical drilling by a drill or drilling by electric discharge machining. In this case, it is desirable to use die steel for hot working as the material of the mold in view of hot strength.
In addition, since the refrigerant supply pipe fulfills the refrigerant discharge function if it communicates with the refrigerant discharge port, it has pores penetrating from the inside of the mold to the outer surface instead of drilling the refrigerant discharge port and the refrigerant supply pipe in the mold. A refrigerant supply pipe may be connected to the porous metal. 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.
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.

Although not shown, the refrigerant supply pipe 11 is desirably provided with three types of valves, that is, an on-off valve, a flow rate adjustment valve, and a pressure adjustment valve. Each function of the on-off valve, the flow rate adjustment valve, and the pressure adjustment valve 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)

From the above equation, the refrigerant discharge amount Q, the discharge flow rate U, the discharge pressure P, the discharge time T, and the discharge timing are selected by at least one of the on-off valve, the flow rate adjustment valve, and the pressure adjustment valve of the refrigerant supply pipe. One or more parameters can be controlled, thereby controlling the heat transfer coefficient.
Therefore, in the present invention, it is not always necessary to provide three types of valves, that is, an on-off valve, a flow rate adjusting valve, and a pressure adjusting valve, and the function can be achieved by one valve. Since the control of the parameters is facilitated by providing three types of valves, that is, a pressure regulating valve, it is desirable to provide three types of valves, an on-off valve, a flow rate regulating valve, and a pressure regulating valve, in the refrigerant supply pipe.

Control of one or two or more parameters selected from the three types of valves, or at least one of the valves, the discharge amount Q of refrigerant, the discharge flow rate U, the discharge pressure P, the discharge time T, and the discharge timing, that is, refrigerant discharge The control of the heat transfer coefficient α by is desirably performed for each refrigerant outlet. As a result, the heat transfer coefficient α due to refrigerant discharge from the plurality of refrigerant discharge ports can be freely varied, so that the strength of the metal tube can be arbitrarily controlled.
For example, the plurality of refrigerant discharge ports formed on the molding surface of the shaft pushing device is one of the purposes for cooling the entire inner surface of the metal tube, but the heat transfer coefficient α depends on the distance from the molding surface of the shaft pushing device. It is desirable to control the heat transfer coefficient α for each refrigerant discharge port so as not to cause a difference.
On the other hand, regarding the plurality of refrigerant discharge ports formed on the molding surface of the mold, a plurality of refrigerant discharge ports are formed along the longitudinal direction so as to cover the entire longitudinal direction of the metal tube, and the outer surface of the metal tube A plurality of refrigerant discharge ports are formed so as to cover the outer surface of the metal tube so that the entire surface can be covered, and the refrigerant is discharged from all the refrigerant discharge ports to uniformly increase the strength of the entire metal tube. In this case, it is not necessary to control the heat transfer coefficient α by discharging the refrigerant for each refrigerant discharge port.

The above is a description of the refrigerant discharge mechanism including the refrigerant discharge port 10 and the refrigerant supply pipe 11. However, a plurality of refrigerant recovery ports are formed on the molding surface of the mold or the shaft pressing device, and A refrigerant recovery pipe communicating with the refrigerant recovery port may be formed inside. Thereby, the refrigerant discharged to the inner surface or the outer surface of the metal tube can be efficiently recovered. Furthermore, the cooling efficiency can be improved by recovering the refrigerant from the refrigerant recovery pipe by suction means such as a vacuum generator. This is because the refrigerant that has not been vaporized adheres or accumulates along the molding surface of the mold or the shaft pressing device, for example, at the bottom of the protrusion described later, and contributes to cooling at the adhesion portion. Or when the refrigerant remains in the accumulated state, the heat transfer coefficient α at the adhering portion or the like when the refrigerant is newly discharged is lower than when 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. Furthermore, it is possible to efficiently recover the solid lubricant that has not been fixed or has been separated from the lubricant.
The coolant recovery port and the coolant recovery tube can be formed by the same method as the coolant discharge port 10 and the coolant supply tube 11 described above.

Further, if a plurality of protrusions are formed on the molding surface of a mold or a shaft pressing device (hereinafter referred to as a mold or the like), the contact area between the mold or the like and the metal tube is reduced, and the mold during press molding is reduced. Since overcooling of the metal tube due to heat removal from the mold can be suppressed, it is desirable to form a plurality of protrusions on the molding surface of a mold or the like. Conversely, by increasing the contact area between the metal tube and the refrigerant, there is an effect that 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 after completion of molding, it becomes easy to circulate the refrigerant in the gap between the protrusion and the metal tube, and the cooling efficiency between the mold and the metal tube can be improved. In addition to this, it is possible to reduce the thermal distortion of the mold or the like and increase the processing accuracy.
In addition, by forming a plurality of protrusions on the molding surface of the mold or the like, the solid lubricant contained in the lubricating liquid supplied to the sliding portion between the mold or the like and the metal tube is formed on the molding surface of the mold or the like. It becomes easy to adhere to the film and the moldability is improved.

  The shape of the protrusions formed on the molding surface of the mold or the like at a predetermined interval is preferably a cylindrical shape, but the horizontal cross-sectional shape is preferably one of a circular shape, a polygonal shape, and a star shape. The shape of the vertical cross section is preferably rectangular or trapezoidal, and may be hemispherical.

The projecting portion can exert the above-described effect if it is formed on at least one molding surface such as a mold, but it may be formed on both molding surfaces. Moreover, you may provide in a part of molding surfaces, such as a metal mold | die, or the whole surface.
In addition, since the shape of the protruding portion may be transferred to the press-molded product and harm the surface property of the molded product, the mold portion around the protruding portion may be removed to form a recess, or at the protruding portion forming position. It is desirable to form a recess having a depth that matches the height of the protrusion in the mold portion, and to form the protrusion in the recess.

The area ratio of the protrusions is desirably 1 to 90% of the molding surface of a mold or the like. If it is less than 1%, the shape of the protrusion is easily transferred to the material to be molded, and if it exceeds 90%, the gap between the protrusions is narrow, the pressure loss increases, and the refrigerant cannot be charged or flown, so that the cooling efficiency is lowered. Further, since the supplied lubricating liquid cannot be filled or flowed, it is difficult to fix the solid lubricant to the sliding portion between the mold and the metal tube.
When the horizontal cross-sectional shape of the protrusion is circular, the diameter of the protrusion is preferably 10 μm to 5 mm when the diameter of the protrusion is a polygonal shape or a star shape. 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 a projection part, it is desirable that they are 5 micrometers-1 mm. If the height of the protrusion is less than 5 μm, the gap with the material to be molded is too small, and it is difficult to circulate the coolant or lubricant between the mold or the like and the metal tube. If the height exceeds 1 mm, the gap is excessive. Thus, the cooling rate due to the heat conduction of the refrigerant decreases.

The protrusions can be formed by electrolytic processing, chemical etching, electric discharge processing, plating method, 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 convex shape, for example, after increasing the current density stepwise, plating may be performed at a constant current density.

  In the present invention, a solid lubricant can be used. As the solid lubricant, one or a mixture of two or more of graphite, molybdenum disulfide, titania, tungsten sulfide, and mica can be used. If such a solid lubricant is pre-fixed to a part of a metal tube with a high degree of processing and then hot press forming is started, the lubrication effect by the solid lubricant, that is, deformation concentration and frictional heat generation in a part with a high degree of processing is avoided As a result, local metal thinning, breakage, and scratching of the metal tube can be prevented, and press formability can be improved.

  As a timing for fixing the solid lubricant to the metal tube, it is desirable to fix the solid lubricant immediately after starting the press molding, for example, immediately after setting the heated metal tube between the upper die and the lower die. At the stage where the metal tube is set between the molds and positioned, the heated metal tube is still in a high temperature state, so that the solid lubricant can be fixed to the metal tube very easily without any special treatment. be able to. In other words, the solid lubricant exerts its lubricating effect only after it is fixed to the molding surface such as a mold. However, every time the press molding is performed, the operator applies the solid lubricant to the mold or the like to fix it. Time increases and productivity is greatly reduced. Also, in order to shorten the working time, applying a solid lubricant to a metal tube in advance and trying to fix it by heating will cause decomposition of the solid lubricant and binder, and the function of the solid lubricant will be reduced. I can't do it. Alternatively, in the method of mixing the solid lubricant with the refrigerant, the solid lubricant is washed away by the refrigerant and cannot function as a solid lubricant.

  On the other hand, at the stage where the metal tube is set between the molds and positioned, the heated metal tube is still in a high temperature state. At this time, the solid lubricant is dispersed in the portion of the metal tube having a high degree of processing. Alternatively, when the dissolved lubricating liquid is discharged, the solid lubricant contained in the lubricating liquid can be fixed to the metal tube very easily. Therefore, the heated metal tube is positioned between the upper die and the lower die for positioning, and then the solid lubricant is applied to the portion of the metal tube having a high degree of processing, that is, the portion where the metal tube and the mold are slid severely. When the press molding is started after discharging the lubricant in which the lubricant is dispersed or dissolved and fixing the solid lubricant contained in the lubricant, the lubrication effect by the solid lubricant, i.e., processing, is prevented without hindering productivity. It is possible to avoid deformation concentration and frictional heat generation at a high degree of site, thereby preventing local thinning, breakage and scratching of the metal tube.

  As for the method of fixing the solid lubricant to the metal tube, as described above, the lubricating liquid supply port formed on the molding surface of the mold with the lubricating liquid in which the solid lubricant and the binder are dispersed or dissolved in the predetermined liquid, or It is desirable to apply from a spray nozzle for supplying a lubricating liquid. By discharging or spraying the lubricant, the solid lubricant can be uniformly fixed on the surface of the metal tube. Further, since the lubricating liquid supply port or the lubricating liquid supply spray nozzle passes through the lubricating liquid supply pipe and the valve mechanism, an appropriate amount can be supplied to an appropriate portion. Further, since the supply is performed immediately before the press working, it is possible to prevent the occurrence of uneven oxidation in the metal tube. In addition, since the solid lubricant is immediately fixed to the metal tube, there is an effect that the solid lubricant does not have to be washed away by the refrigerant until necessary.

  Further, as a method for preventing the metal tube from being ruptured or buckled at a high degree of processing, as shown in FIG. 6, a cushion 4 or a pad 5 for generating tension in the longitudinal direction of the metal tube 1 may be used. desirable. In this case, the cushion load is 15 t and the pad load is 20 t. 6A is a view showing a state after forming, and FIG. 6B is a view showing a state after forming.

  Next, Example 1 of the present invention will be described. The conditions of this example are one condition adopted to prove the feasibility and remarkable effect of the present invention, and the present invention is based on this one condition. It is not limited to.

As shown in FIG. 1, an Al-plated steel pipe of the following material is set in the mold 2, and then bending is performed by clamping as shown in FIG. 2, and then two shafts as shown in FIG. Both ends of the steel pipe were expanded using the pushing device 3, and immediately after that, the molded product was cooled under the following cooling conditions 1-5.
Steel pipe size: Outer diameter φ63.5mm × Plate thickness 2.0mm × Length 1000mm
Steel pipe material: STKM440 (YS: 390 MPa, TS: 450 MPa, EL: 40%)
Tube end expansion: ○ → □ (64 × 120) Completed within 2 seconds after mold clamping Initial heating temperature: Furnace heating 950 ° C
Mold: Refrigerant outlet + Refrigerant recovery port (each 1mm in diameter / pitch 10mm)
Shaft pushing device x2: Refrigerant discharge port + Refrigerant recovery port (each 1mm in diameter / pitch 10mm)
Cooling condition 1: Simultaneously discharge refrigerant from mold and shaft pushing device Cooling condition 2: Discharge refrigerant only from die Cooling condition 3: Discharge refrigerant only from shaft pushing device Cooling condition 4: No refrigerant discharge (only heat removal from die)
Cooling condition 5: Immerse in a water bath and cool

Table 1 shows the results of the hardness, shape, and surface damage of the molded product obtained by bending, expanding, and cooling press-molded under the above conditions.
For shape evaluation, if measured with a three-dimensional non-contact measuring machine and the error from CAD is less than 10%, ◎ if it is 10% or more and less than 20%, ○ or 20% or more and less than 30%. △, otherwise evaluated as x.
Regarding the evaluation of the surface damage, the cooling condition 5 was used as a reference, and it was evaluated as ◎ if better, ○ if equivalent, and × if inferior.

DESCRIPTION OF SYMBOLS 1 Metal pipe 2 Mold 3 Axial pushing device 4 Cushion 5 Pad 10 Refrigerant discharge port 11 Refrigerant supply pipe

Claims (8)

In a hot press molding apparatus that press-molds a heated metal tube using a mold,
A plurality of refrigerant discharge ports are formed on the molding surface of the mold, and a refrigerant supply pipe communicating with each refrigerant discharge port is formed inside the mold.
A hot press forming apparatus characterized in that the refrigerant is discharged from some or all of the plurality of refrigerant discharge ports toward the outer surface of the metal tube while being clamped.
In a hot press molding apparatus for press-molding a heated metal tube using a mold and a shaft pressing device,
A plurality of refrigerant discharge ports are formed on the molding surface of the shaft pushing device, and a refrigerant supply pipe communicating with each refrigerant discharge port is formed inside the shaft pushing device,
A hot press forming apparatus, wherein a refrigerant is discharged from a part or all of a plurality of refrigerant discharge ports toward an inner surface of a metal tube while being clamped.
In a hot press molding apparatus for press-molding a heated metal tube using a mold and a shaft pressing device,
A plurality of refrigerant discharge ports are formed on the molding surface of the mold, and a refrigerant supply pipe communicating with each refrigerant discharge port is formed inside the mold.
A plurality of refrigerant discharge ports are formed on the molding surface of the shaft pushing device, and a refrigerant supply pipe communicating with each refrigerant discharge port is formed inside the shaft pushing device,
A hot press forming apparatus, wherein a refrigerant is discharged from a part or all of a plurality of refrigerant discharge ports toward one or both of an outer surface and an inner surface of a metal tube while being clamped.
4. A plurality of refrigerant recovery ports are formed on the molding surface of the mold, and a refrigerant recovery pipe communicating with each refrigerant recovery port is formed inside the mold. The hot press molding apparatus according to claim 1.
4. A plurality of refrigerant recovery ports are formed on a molding surface of the shaft pressing device, and a refrigerant recovery pipe communicating with each refrigerant recovery port is formed inside the shaft pressing device. The hot press molding apparatus described in 1.
In the hot press molding method of press-molding a heated metal tube using a mold,
A plurality of refrigerant discharge ports are formed on the molding surface of the mold, and a refrigerant supply pipe communicating with each refrigerant discharge port is formed inside the mold.
A hot press forming method characterized in that the refrigerant is discharged from some or all of the plurality of refrigerant discharge ports toward the outer surface of the metal tube while being clamped.
In a hot press molding method of press-molding a heated metal tube using a mold and a shaft pressing device,
A plurality of refrigerant discharge ports are formed on the molding surface of the shaft pushing device, and a refrigerant supply pipe communicating with each refrigerant discharge port is formed inside the shaft pushing device,
A hot press forming method, wherein the refrigerant is discharged from some or all of the plurality of refrigerant discharge ports toward the inner surface of the metal tube while being clamped.
In a hot press molding method of press-molding a heated metal tube using a mold and a shaft pressing device,
A plurality of refrigerant discharge ports are formed on the molding surface of the mold, and a refrigerant supply pipe communicating with each refrigerant discharge port is formed inside the mold.
A plurality of refrigerant discharge ports are formed on the molding surface of the shaft pushing device, and a refrigerant supply pipe communicating with each refrigerant discharge port is formed inside the shaft pushing device,
A hot press molding method characterized in that refrigerant discharge is performed from a part or all of a plurality of refrigerant discharge ports toward one or both of an outer surface and an inner surface of a metal tube while being clamped.

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