JP2011523375A - Press hardening mold cooling device - Google Patents

Abstract

In the present invention, the structure is improved so that the cooling rate of the trimming cut site can be delayed during the pressing process of the steel sheet blank for producing the press hardening component. The cooling device for the press-curing mold according to the present invention includes a cooling water supply unit disposed inside so as to press the steel plate blank from above and below, and a press-curing mold composed of a lower mold. And it arrange | positions between the cooling water supply part of an upper and lower metal mold | die, and the contact surface of a steel plate blank, and is divided roughly into the cooling water temperature adjustment means which adjusts the temperature of the cooling water transmitted to the steel plate blank side. According to this, the present invention delays the cooling rate transmitted from the cooling water supply part of the upper and lower molds to prevent rapid cooling of the trimming cutting site and prevents the formation of a highly hard martensite structure. Therefore, it is possible to reduce the wear of the trimming mold during the trimming process, and to have a useful effect of improving durability and increasing productivity.
[Selection] Figure 2

Description

  The present invention relates to a cooling device for a press hardening mold, and more particularly to a press hardening whose structure is improved so as to adjust a cooling rate in order to adjust a surface structure hardness of a portion cut by a trimming mold of a steel plate blank. The present invention relates to a mold cooling apparatus.

  Generally, the manufacturing method of press-hardened parts is the method of heating a steel material with improved hardening ability by adding B, Mo, Cr, etc. at a high temperature of about 900 ° C., which is higher than the Ac3 transformation point, to complete austenite. This is a method of manufacturing a high-strength product by rapidly forming the steel sheet into a product shape at once with a press die and then martensite through rapid cooling.

  As is well known, steel sheets become very easy to form when heated at high temperatures, which makes the steel produced through the press hardening process not only slightly better than the workability of general steel sheets, but also high. Much better than strength steel.

  Moreover, since the steel sheet manufactured through the press hardening process has a very high strength (1,400 MPa or more), it is very excellent in terms of specific strength obtained by dividing the yield strength by density and greatly contributes to weight reduction of automobiles. In addition, since there is almost no shape deformation (Springback) after processing, it is applied to ultra-high strength required parts that are difficult to form.

  In the press hardening process, in order to transform the steel sheet into complete austenite, conditions of heating at about 900 ° C. or more for several minutes or more are necessary, and automation must be performed for the efficiency of the process.

  The conventional press hardening process is composed of a process in which a blank before being hardened from a wound steel sheet coil is heated through a linear heating furnace and then transferred to the press side by a robot and press formed.

The press employs a lower mold on the press hardening mold, and cooling water is supplied to the upper and lower molds for the surface texture hardening of the steel sheet blank, respectively. The blank is allowed to cool.
The existing steel plate blank is divided into an intermediate portion used as an actual part and a double-side scrap portion that is cut and discarded by scrap, and the both-side scrap portion is actually cut by a trimming die in a post-processing step.
However, the above-mentioned hardening phenomenon due to the cooling of the press die also occurs at the trimming cutting site cut by the existing trimming die, and the trimming die is worn heavily during the trimming process, which reduces the workability of the trimming process. There is a problem in that productivity is reduced due to work loss caused by the replacement work of the trimming mold.

  The present invention has been proposed in order to solve the above-mentioned problems, and the object thereof is to improve the structure of the press hardening mold so that one part of the steel plate blank is different from the other part. An object of the present invention is to provide a cooling device for a press hardening mold in which trimming is easily performed through different cooling processes.

  In order to achieve the above object, the present invention comprises upper and lower molds, and a press hardening mold for pressing a steel sheet blank,

  A plurality of cooling water supply units arranged to be spaced apart from each other in the upper and lower molds and serving as a passage through which cooling water flows;

  Cooling water temperature adjusting means for adjusting the temperature of the cooling water supplied to the cooling water supply unit for each part.

  The cooling water temperature adjusting means supplies cooling water having a temperature higher than the cooling water supplied to the other cooling water supply units to the cooling water supply unit adjacent to the trimming cut portion of the steel sheet blank in the cooling water supply unit. Equipped with a controller that controls the difference

  The controller includes a heater that heats the cooling water supplied to the cooling water supply unit adjacent to the trimming cutting site.

  The controller controls the operation of the heater so that the temperature of the cooling water supplied to the cooling water supply unit adjacent to the trimming cutting site is maintained at 45 to 80 ° C.

  A hollow part is formed between the cooling water supply part which adjoins the trimming cutting site | part of the said steel plate blank, and the contact surface of the said steel plate blank.

  The press hardening mold has a heat insulating material disposed therein.

  There is further provided a temperature detection sensor that is disposed between the trimming cut portion of the steel plate blank and the steel plate blank, detects the temperature of the press hardening mold, and outputs the detected signal to the controller side.

  The cooling water temperature adjusting means controls the temperature of the cooling water so that the trimming cut portion of the steel plate blank has a mixed structure of ferrite, pearlite, and bainite.

  Another feature of the present invention is that a heat-insulating material is disposed inside, a lower mold, and a press hardening mold for pressing a steel plate blank,

  A plurality of cooling water supply units arranged to be spaced apart from each other in the upper and lower molds and serving as a passage through which cooling water flows;

  Cooling water temperature adjusting means for adjusting the temperature of the cooling water supplied to the cooling water supply unit for each part based on a temperature detection sensor disposed inside the press hardening mold.

  The structure of the present invention has been improved so that the cooling rate of the trimming cut site can be delayed during the pressing process of the steel sheet blank for producing the press hardening component. Trimming mold during the trimming process, because the cooling rate transmitted from the cooling water supply part of the mold is delayed to prevent rapid cooling of the trimming cutting part and prevent the formation of a hard martensite structure. It has a useful effect that can reduce the wear and improve the durability and increase the productivity.

It is a lineblock diagram showing a 1st embodiment of a cooling device of a press hardening die concerning the present invention. It is a perspective view which shows 2nd Embodiment of this invention. It is a block diagram which shows 3rd Embodiment of the cooling device of the press hardening metal mold | die which concerns on this invention. It is a block diagram which shows 4th Embodiment of the cooling device of the press hardening metal mold | die which concerns on this invention. It is a block diagram which shows 5th Embodiment of the cooling device of the press hardening metal mold | die which concerns on this invention. It is a block diagram which shows 6th Embodiment of the cooling device of the press hardening metal mold | die which concerns on this invention. It is a graph which shows the hourly cooling process of the steel plate blank which concerns on this invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  If the 1st Embodiment of the cooling device of the press hardening metal mold | die which concerns on this invention is described with reference to FIG. 1, the steel plate blank S will be press-processed from the upper part and the lower part, and the cooling water supply part 12, inside, 22 and the press hardening mold P constituted by the lower molds 10 and 20, the cooling water supply parts 12 and 22 of the upper and lower molds 10 and 20, and the contact surface of the steel plate blank S. It is roughly divided into cooling water temperature adjusting means that is arranged between them and adjusts the temperature of the cooling water transmitted to the steel plate blank S side.

  More specifically, the cooling water temperature adjusting means includes a controller 100 for supplying the temperature of the cooling water supplied to the plurality of cooling water supply units 12 and 22 to the difference and the like. Is provided with a heater 150 for heating the cooling water supplied to the cooling water supply units 12 and 22 at a position close to the trimming cutting site T1.

  The controller 100 controls on / off of the operation of the heater 150 so as to maintain the temperature of the cooling water supplied to the cooling water supply units 12 and 22 adjacent to the trimming cutting site T1 at 45 to 80 ° C. The cooling water supply units 12 and 22 are supplied with 10 to 25 ° C. cooling water, which is the same temperature as the existing one.

  That is, the controller 100 supplies cooling water of 10 to 25 ° C. to the cooling water supply parts 12 and 22 side close to the intermediate part that is a part of the steel plate blank S, and is close to the trimming cutting part T1 located on both sides. Control is performed so that the cooling water supply units 12 and 22 are heated by a heater 150 and 45 to 80 ° C. cooling water is supplied.

  At this time, the temperature of the cooling water is adjusted to 45 to 80 ° C. because the structure of the steel sheet blank S corresponding to the trimming cut site T1 is mixed with ferrite, pearlite, and bainite whose toughness and ductility are superior to the martensitic structure This is to transform the organization.

  The operation of the present invention having such a configuration will be described as follows.

  The apparatus for cooling a press hardening mold according to the present invention transfers a steel sheet blank S heated at 900 ° C. or higher through a heating furnace to a press hardening mold P using a robot in order to produce press hardened parts. In the process of performing the pressing process after the cooling process, the cooling rate transmitted from the cooling water supply units 12 and 22 to the trimming cutting part T1 which is the boundary part between the intermediate part and the scrap part on both sides of the steel sheet blank S is set. It has a lower thermal conductivity than other parts of the steel plate blank S.

  For this purpose, the cooling water supply parts 12 and 22 adjacent to the trimming cutting part T1 of the cooling water supply parts 12 and 22 arranged on the lower molds 10 and 20 on the press hardening mold P are arranged on the cooling water supply parts 12 and 22 side. By supplying cooling water having a higher cooling water temperature than the part, the cooling rate of the trimming cutting part T1 is delayed from the other part during the trimming process, and the hardenability can be lowered from the other part of the steel plate blank S. It is.

  Thereby, the trimming cutting site | part T1 of the steel plate blank S has a late | slow cooling rate compared with another site | part during a press process, and, thereby, a structure | tissue with low hardness compared with another site | part is formed.

  After that, during the trimming process, the remaining portion of the steel sheet blank S excluding the trimming cutting portion T1 is formed into a martensite structure with high hardness, whereas the trimming cutting portion has a lower hardness than the martensite structure and has good workability. It is converted into + pearlite + bainite structure.

  At this time, the curing ability of the trimming cutting portion T1 varies depending on the cooling water temperature. For example, the correlation is such that the cooling rate is slower when the cooling water temperature is increased and the cooling rate is higher when the cooling water temperature is lowered. Have.

  Hereinafter, the overlapping description is abbreviate | omitted with respect to the component demonstrated in previous embodiment among other embodiments of this invention, and drawing code | symbol is attached | subjected the same.

  On the other hand, FIG. 2 is a diagram showing a second embodiment of the present invention, in which a hollow is formed in the upper and lower molds between the cooling water supply parts 12 and 22 adjacent to the trimming cut site T1 and the contact surface of the steel plate blank S. A portion 210 is formed.

  This is to reduce the thermal conductivity of the cooling water transmitted from the cooling water supply units 12 and 22, and to make the trimming cut portion T1 of the steel plate blank S described above into a mixed structure of ferrite + pearlite + bainite structure.

  That is, the heat transmitted from the cooling water supply parts 12 and 22 is conducted to the trimming cutting part T1 side through the hollow part 210, thereby lowering the cooling function of the cooling water from other parts, and the steel plate blank. The S trimming cut portion T1 is prevented from being rapidly cooled.

  At this time, the hollow portion 210 is shown here as being formed on both sides of the upper and lower molds 10 and 20, but may be formed only in the upper mold or the lower mold.

  Moreover, it is preferable that the hollow part 210 has a square or circular cross-sectional shape so that the heat transfer efficiency is lowered.

  FIG. 3 is a block diagram showing a third embodiment of the present invention. The configuration constitutes a press-curing die P in addition to the components of the above-described embodiment, and also inside the lower dies 10 and 20. The heat insulating material 300 is arranged vertically.

  The heat insulating material 300 is vertically arranged on both sides of the press-curing mold P so as to divide the upper mold with the trimming cut site T1 as a reference and the lower mold.

  This is for differentiating the temperature of the cooling water transmitted to the trimming cutting part T1 of the steel plate blank S from the temperature of the cooling water transmitted to other parts.

  That is, the temperature of the cooling water transmitted through the cooling water supply units 12 and 22 is supplied as different temperatures by dividing the press hardening mold P into the central part and the both side parts through the heat insulating material 300. Thus, different cooling performance can be provided for each part of the steel plate blank.

  FIG. 4 is a block diagram showing a fourth embodiment of the present invention, which includes the components of the above-described embodiment, is arranged inside a press hardening mold P, and detects the internal temperature of the mold. Further, a temperature detection sensor 155 that outputs the detected signal to the controller 100 side is further provided.

  The temperature detection sensor 155 measures the mold temperature in real time, and when the temperature of the mold becomes lower than the temperature set in advance in the controller 100 by the supply of the cooling water, the cooling water is heated by the heater 150 and the mold is heated. It functions to heat or maintain the temperature of a specific part of the mold.

  FIG. 5 is a block diagram showing a fifth embodiment of the present invention. The configuration is such that the diameter of the cooling water supply units 12 and 22 adjacent to the trimming cutting site T1 is larger than the diameter of the other cooling water supply units 12 and 22. It is formed to have a small diameter.

  FIG. 6 is a block diagram showing a sixth embodiment of the present invention. The configuration is arranged on both sides of the press-curing die P, and the cooling water supply units 12 and 22 close to the trimming cutting site T1. It has the structure where the space | interval with the contact surface of a steel plate blank is arrange | positioned further far than the space | interval of the cooling water supply parts 12 and 22 arrange | positioned in another site | part, and the contact surface of a steel plate blank.

  That is, when viewed from the drawing, the cooling water supply unit 12 disposed in the upper mold and adjacent to the trimming cutting site T1 is disposed above the cooling water supply unit 12 disposed in the other part of the upper mold, and the lower part. The cooling water supply unit 22 arranged in the mold and in the vicinity of the trimming cutting site T1 has a structure arranged below the cooling water supply unit 22 2 arranged in the other part of the lower mold.

  Therefore, 5th Embodiment and 6th Embodiment of this invention show that even if it does not change the supply temperature of cooling water, it can change cooling performance according to the site | part of a steel plate blank.

  That is, in the embodiment of the present invention, during the pressing process of the steel sheet blank S, the cooling rate transmitted from the cooling water supply units 12 and 22 of the lower molds 10 and 20 to the trimming cutting site T1 is different for each site. By this, the rapid cooling of the trimming cutting part T1 of the steel plate blank S can be prevented, and the martensite structure with high hardness can be prevented.

  Thereby, as shown in FIG. 7, the steel plate blank S after the pressing process according to the present invention has an “A” section indicating the hourly cooling rate of the intermediate portion in contact with the steel plate blank S, and the time of the trimming cut portion T1. Since it is composed of “B” sections showing different cooling rates and the cooling rates of the respective portions of the steel sheet blank S are different, the structure corresponding to the “A” section is 800 at 17 to 24 ° C. per second at 950 ° C. After being cooled to 0 ° C., it is hardened by rapid cooling to form a martensite structure, and in the “B” section, it is gradually cooled at 800 ° C. to form a mixed structure.

Claims (8)

It is composed of upper and lower molds, and a press hardening mold for pressing steel plate blanks,
A plurality of cooling water supply units arranged to be spaced apart from each other in the upper and lower molds and serving as a passage through which cooling water flows;
And a cooling water temperature adjusting means for adjusting the temperature of the cooling water supplied to the cooling water supply section for each part. The cooling water temperature adjusting means is a cooling water having a temperature higher than that of the cooling water supplied to the other cooling water supply unit in the cooling water supply unit adjacent to the trimming cut portion of the steel sheet blank in the cooling water supply unit. Equipped with a controller that controls to supply the difference
The said controller is equipped with the heater which heats the cooling water supplied to the cooling water supply part close | similar to the said trimming cutting | disconnection site | part, The cooling device of the metal mold | die for press hardening of Claim 1 characterized by the above-mentioned.   3. The controller according to claim 2, wherein the controller controls the operation of the heater so that a temperature of the cooling water supplied to the cooling water supply unit adjacent to the trimming cutting portion is maintained at 45 to 80 ° C. 3. A cooling device for the press-curing mold as described.   2. The press hardening mold cooling according to claim 1, wherein a hollow portion is formed between a cooling water supply portion adjacent to a trimming cut portion of the steel plate blank and a contact surface of the steel plate blank. apparatus.   The apparatus for cooling a press-curing mold according to claim 1, wherein a heat-insulating material is disposed inside the press-curing mold.   A temperature detection sensor is further provided between the trimming cut part of the steel plate blank and the steel plate blank, detects a temperature of the press hardening mold, and outputs a detected signal to the controller side. The press hardening die cooling apparatus according to claim 2.   The said cooling water temperature control means controls the temperature of a cooling water so that the trimming cutting site | part of the said steel plate blank may become a mixed structure of a ferrite, a pearlite, and a bainite, The any one of the Claims 1-4 characterized by the above-mentioned. A cooling device for a press-curing mold according to claim 1. A heat-insulating material is arranged inside, and is composed of a lower mold, and a press-curing mold for pressing a steel plate blank,
A plurality of cooling water supply units arranged to be spaced apart from each other in the upper and lower molds and serving as a passage through which cooling water flows;
A cooling water temperature adjusting means for adjusting the temperature of the cooling water supplied to the cooling water supply unit for each part based on a temperature detection sensor disposed inside the press hardening mold. Cooling device for press hardening mold.

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