KR102157735B1 - Hot stamping method - Google Patents

Abstract

The present invention includes a mold design and mold manufacturing step of designing and manufacturing a cold forming mold for cold forming a blank supplied to manufacture a product; A cold forming step of injecting the blank into a manufactured cold forming mold and forming a temporary product having a shape of a product to be manufactured; A mold trim step of inserting the temporary product molded through the cold forming into a manufactured mold trim and trimming it; A heating step of heating the temporary product trimmed in the mold trim to a high temperature in a heating furnace; A heat treatment step of heat treatment while cooling the temporary product by putting the temporary product through the heating step into a press mold; And a mold trim design and mold trim manufacturing step of designing and manufacturing a mold for trimming the temporary product produced through the cold forming step, wherein the mold trim design and mold trim manufacturing steps include the mold design and mold manufacturing steps. After that, it proceeds before the mold trim step. Provides a hot stamping method including a thermal expansion analysis step to predict the amount of shrinkage and a curve surface shape error analysis step to predict the amount of shrinkage of the corner rounds of the temporary product when the heated temporary product is heat treated in a press mold do.
Therefore, cutting of the product can be smoothly performed by trimming the raw material before heat treatment to change it into ultra-high-strength steel, and harmful gases generated when cutting the ultra-high-strength steel can be blocked, and the productivity of the product is improved by shortening the process time. I can make it.

Description

Hot stamping method

The present invention relates to a hot stamping method, and more particularly, a center pillar or rail roof, which is a component that is directly connected to personal injury if the rigidity is insufficient during an accident of a vehicle, is made of ultra-high strength steel using a blank. It relates to a hot stamping method capable of performing heat treatment while forming.

As a technology development trend in the automotive industry, weight reduction is the main issue for low carbon emissions and energy efficiency, and representative technologies for this are carbon fiber reinforced plastic (CFRP) material technology and hot stamping technology. There is this.

Among them, the hot stamping technique is a general purpose by putting a steel material heated to a high temperature of 950°C into a mold, forming it with a press, and then rapidly cooling it in the mold to heat-treat the material. It is a technology that allows you to have the same strength performance with less weight than steel materials.

The advantage of hot stamping technology is that raw materials can be made of ultra-high strength steel, can be processed into complex shapes, and have excellent dimensional accuracy. In addition, due to the weight reduction effect of the vehicle body, the number of parts to which the hot stamping method technology is applied is gradually increasing worldwide.

The existing hot stamping method proceeds in the order of heating, hot forming, and laser cutting, and the existing hot stamping method requires expensive auxiliary facilities, the problem of low productivity due to a long fixed time, and the laser cutting process proceeds after hot forming. Accordingly, as a product made of ultra-high-strength steel is cut using a laser, the cutting of the ultra-high-strength steel product does not proceed smoothly, and harmful gases are generated during cutting.

The technology behind the present invention is disclosed in Korean Patent Publication No. 10-1581940 (announced on December 31, 2015).

The present invention was created to solve the above problems, excluding the laser cutting process of cutting the heat-treated product, and trimming the temporary product before the heating step after the cold forming step so that the cutting of the product proceeds smoothly. Its purpose is to provide a stamping method that can prevent gas generation.

In order to achieve the above object, the present invention provides a mold design and mold manufacturing step of designing and manufacturing a cold forming mold for cold forming a blank supplied to manufacture a product; A cold forming step of injecting the blank into a manufactured cold forming mold and forming a temporary product having a shape of a product to be manufactured; A mold trim step of inserting the temporary product molded through the cold forming into a manufactured mold trim and trimming it; A heating step of heating the temporary product trimmed in the mold trim to a high temperature in a heating furnace; A heat treatment step of heat treatment while cooling the temporary product by putting the temporary product through the heating step into a press mold; And a mold trim design and mold trim manufacturing step of designing and manufacturing a mold for trimming the temporary product produced through the cold forming step, wherein the mold trim design and mold trim manufacturing steps include the mold design and mold manufacturing steps. After that, it proceeds before the mold trim step, and the mold trim design step includes a hot forming prediction step for predicting the amount of expansion when the trimmed temporary product is heated in a heating furnace, and when the heated temporary product is heat treated in a press mold. Provides a hot stamping method including a thermal expansion analysis step to predict the amount of shrinkage, and a curve surface shape error analysis step to predict the amount of shrinkage of the corner rounds of the temporary product when the heated temporary product is heat treated in a press mold. do.

In the hot stamping method according to the present invention, the mold design and mold manufacturing step may proceed with the mold manufacturing step when the mold design step is completed, and the mold design step includes forming a 2D-shaped blank into a 3D-shaped temporary product. A cold forming prediction step to predict the amount of blank required during the cold forming step, a spring back analysis step of analyzing the spring back of the temporary product generated after the cold forming step, and the temporary product generated after the cold forming step The forming surface shape error analysis step of analyzing the thickness reduction of the corner round portion may be included. In the forming surface shape error analysis step, the forming surface error data map may be used to decrease the thickness of the corner round portion of the temporary product.

The mold design step may further include an inspection step of inspecting the strength and quality of a product manufactured after sequentially passing through the cold forming step, the mold trimming step, the heating step, and the heat treatment step.

The mold design step may further include a database storing step of database-setting the modified contents when the final cold forming mold passed the inspection step, the mold trim and cold forming mold, and the mold trim.

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In the mold trim design and mold trim manufacturing steps, when the mold trim design step is completed, the mold trim manufacturing step may be performed.

In the hot forming prediction step and the thermal expansion analysis step, the amount of expansion and contraction of the temporary product can be predicted using palm stamp software, and the amount by which the corner round part of the temporary product is contracted in the curve surface shape error analysis step is a curved surface. You can use an error date map.

The hot stamping method according to the present invention can smoothly proceed the cutting of the product by trimming the raw material before the heat treatment to change it to the ultra-high-strength steel, can block harmful gases generated when cutting the ultra-high-strength steel, and shorten the process time. To improve the productivity of the product.

1 is a flowchart schematically illustrating a hot stamping method according to an embodiment of the present invention.
FIG. 2 is a diagram schematically showing a sequence of a mold design step in the mold design and mold manufacturing steps shown in FIG. 1.
FIG. 3 is a diagram schematically illustrating a sequence of a mold trim design step in the mold trim design and mold trim manufacturing steps shown in FIG. 1.
4 and 5 are views schematically showing a procedure of the hot stamping method shown in FIG. 1.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the present specification and claims should not be construed as limited to their usual or dictionary meanings, and the inventors appropriately explain the concept of terms in order to describe their own invention in the best way. Based on the principle that it can be defined, it should be interpreted as a meaning and concept consistent with the technical idea of the present invention.

1, the hot stamping method according to an embodiment of the present invention includes a mold design and mold manufacturing step (S100), a cold forming step (S200), a mold trim step (S300), and a heating step (S400). , Including the heat treatment step (S500), may further include a mold trim design and mold trim manufacturing step (S600).

In the mold design and mold manufacturing step (S100), a blank 10 supplied to manufacture a center pillar or rail roof, which is a part of a vehicle, is cold formed into a temporary product having a shape of a component. This is a step of designing the cold forming mold 20 and then manufacturing the designed cold forming mold 20.

1, 2, 4 and 5, the mold design and mold manufacturing step (S100) includes a mold design step (S120) and a mold manufacturing step (140), and the mold design step (S120) When is completed, the mold manufacturing step (S140) proceeds.

The mold design step (S120) includes a cold forming prediction step (S121), a spring back analysis step (S122), a forming surface shape error analysis step 123, an inspection step (S124), and a database storage step (S125). It may contain more.

The cold forming prediction step (S121) is a step of predicting the amount of the blank 10 required when forming the blank 10, which is a raw material in a 2D form, into a temporary product in a 3D form, and the cold forming prediction step (S121) In the 3D shape, an approximate amount of the blank 10 required for molding into a temporary product is predicted.

The spring back analysis step (S122) is a step of analyzing the spring back phenomenon of the temporary product cold-formed through the cold forming step (S200) to be described later. Here, the spring back phenomenon refers to a phenomenon that the material is bent in the bending process of the plastic material and then returns to its original state when the pressure is removed, and in the spring back analysis step (S122), the 3D shaped temporary product is 2D. This is the step of analyzing the amount of deformation to return to its original shape, and it is preferable to analyze the springback of the temporary product using "Autoform" or "Pamstamp2g", and "Autoform", a program that analyzes the springback of the temporary product. Alternatively, "Pamstamp2g" is a program widely used in the relevant field, and a detailed description thereof will be omitted.

The forming surface shape error analysis step (S123) is a step of analyzing an amount by which the thickness of the corner round portion of the cold-formed temporary product is reduced after passing through the cold forming step (S200) to be described later, and the forming surface shape error analysis step In (S123), it is preferable to use the molding surface error data map to reduce the thickness of the corner round portion of the temporary product.

The inspection step (S124) is a step of sequentially performing a cold forming step (S200), a mold trimming step (S300), a heating step (S400) and a heat treatment step (S500) to be described later, and then inspecting the strength and quality of the manufactured product. It is preferable to inspect the product manufactured through the cold forming step (S200), the mold trim step (S300), the heating step (S400) and the heat treatment step (S500) sequentially, but through the above process in advance It is preferable to predict the strength and quality of the manufactured product, and modify the cooling channel (not shown) of the press mold 50 performing the heat treatment step (S500) when the result of the predicted strength and quality is lower than the expected value.

When the inspection step (S124) of the mold design step (S120) is completed, the final cold forming mold 20, the mold trim 30, and the cold forming mold 20 and the mold trim ( When producing 30), it is preferable to perform the database storage step (S125) of converting the modified content into a database.

1 and 5, after passing through the mold design and mold manufacturing step (S100) of designing and manufacturing the cold forming mold 20, and inserting the blank 10 into the manufactured cold forming mold 20 A cold forming step (S200) of forming a temporary product having the shape of the product to be manufactured is performed.

While passing through the cold forming step (S200), the blank 10, which is a raw material having a 2D shape, is formed into a 3D-shaped temporary product, and the temporary product molded through the cold forming step (S200) is mold trimmed (S300). ).

The mold trim step (S300) is a step of cutting and trimming by inserting the molded temporary product into the mold trim 30 manufactured in advance. By inserting the molded temporary product into the mold trim 30 and cutting and trimming, cutting and trimming can be performed evenly, and harmful gas is prevented by cutting and trimming the temporary product that has not been heat treated. do.

The temporary product that has passed through the mold trim step (S300) is supplied to the heating furnace 40 and then heated to a high temperature (S400). The heating step (S400) is a step of heating the temporary product supplied to the inside of the heating furnace 40, and heating the supplied temporary product at a temperature of 930°C for 250 seconds to enter the temporary product into the heating furnace 40 Will expand locally.

The temporary product that has passed the heating step (S400) is subjected to the heat treatment step (S500). In the heat treatment step (S500), the temporary product that has undergone the heating step (S400) is put into the press mold 50 and then cooled to shrink the locally expanded temporary product.

The heat treatment step (S500) locally shrinks the temporary product by cooling it in the press mold 50 for 15 seconds, and the temporary product having a strength of 540 MPa due to the heat treatment step (S500) has a strength of 1500 MPa It will be changed to have.

It is preferable to perform the mold trim designing and manufacturing step (S600) of designing and manufacturing a mold for trimming the temporary product manufactured through the cold forming step (S200), and the mold trim designing and manufacturing step (S600) It is preferable to proceed after the mold design and mold manufacturing step (S100) and before the mold trim step (S300).

1 and 3, the mold trim designing and manufacturing step (S600) includes a mold trim designing step (S620) and a mold trim manufacturing step (S640), and when the mold trim designing step (S620) is completed The mold trim production step (S640) proceeds.

3 and 4, the mold trim design step (S620) includes a hot forming prediction step (S621), a thermal expansion analysis step (S622), and a curved surface shape error analysis step (S623). The hot forming prediction step (S621) is a step of predicting the amount of expansion of the temporary product passed through the mold trim step (S300) when heated in the heating furnace 40, and the thermal expansion analysis step (S622) is the heating furnace This is a step of predicting the amount of shrinkage of the temporary product heated in 40 during heat treatment in the press mold 50.

In the hot forming prediction step (S621) and the thermal expansion analysis step (S622), it is preferable to predict the amount by which the temporary product expands and contracts using palm stamp software, and the palm stamp software is widely used in the field. In bar, detailed descriptions thereof will be omitted.

The curve surface shape error analysis step (S623) is a step for predicting the amount of shrinkage of the corner round portion of the temporary product when the temporary product heated in the heating furnace 40 is heat-treated in the press mold 50. In the curve surface shape error analysis step (S623), it is preferable to use a curve surface error data map for the amount of shrinkage of the corner round portion of the temporary product, and this is also widely used in the relevant field, and a detailed description thereof will be omitted. .

Referring to Figure 1, the blank 10 is put into the cold forming mold 20 manufactured through the mold design and mold manufacturing step (S100) and undergoes a cold forming step (S200) of cold forming into a temporary product, The blank 10 is cold formed in the cold forming mold 20 for 3 seconds, and the blank 10 and the manufactured temporary product that has undergone the cold forming have a strength of 540 MPa.

The temporary product that has passed through the cold forming step (S200) performs the mold trim step (S300), and when the temporary product is put into the mold trim 30, cutting and trimming are performed by the mold trim 30 for 3 seconds. Will perform.

After passing through the mold trim step (S300), the temporary product is heated in the heating furnace 40 to perform the heating step (S400), and the temporary product that has passed the heating step (S400) is cooled in the press mold 50 After passing through the heat treatment step (S500), it is manufactured as an ultra high tensile steel product.

Therefore, cutting of the product can be smoothly performed by trimming the raw material before heat treatment to change it to ultra-high-strength steel, and harmful gases generated when cutting the ultra-high-strength steel can be blocked, and the productivity of the product is improved by shortening the process time. I can make it.

The present invention has been described with reference to the embodiments shown in the drawings, but these are only exemplary, and those of ordinary skill in the art will appreciate that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

10: blank 20: cold forming mold
30: mold trim 40: heating furnace
50: press mold

Claims (8)

A mold design and mold manufacturing step of designing and manufacturing a cold forming mold for cold forming a blank supplied to manufacture a product;
A cold forming step of injecting the blank into a manufactured cold forming mold and forming a temporary product having a shape of a product to be manufactured;
A mold trim step of inserting the temporary product molded through the cold forming into a manufactured mold trim and trimming it;
A heating step of heating the temporary product trimmed in the mold trim to a high temperature in a heating furnace;
A heat treatment step of heat treatment while cooling the temporary product by putting the temporary product through the heating step into a press mold; And
Including a mold trim design and mold trim manufacturing steps for designing and manufacturing a mold for trimming the temporary product produced through the cold forming step,
The mold trim design and mold trim manufacturing steps,
It proceeds after the mold design and mold manufacturing steps and before the mold trim step,
The mold trim design step,
A hot forming prediction step to predict the amount that the trimmed household product expands when heated in the furnace,
A thermal expansion analysis step to predict the amount of shrinkage of the heated temporary product during heat treatment in the press mold,
Hot stamping method including a curve surface shape error analysis step to predict the amount of shrinkage of the corner rounds of the temporary product when the heated temporary product is heat treated in a press mold.
The method according to claim 1,
In the mold design and mold manufacturing step, when the mold design step is completed, the mold manufacturing step proceeds,
The mold design step,
A cold forming prediction step to predict the amount of blank required when forming a 2D-shaped blank into a 3D-shaped temporary product,
A spring back analysis step of analyzing the spring back of the temporary product generated after the cold forming step,
Hot stamping method comprising a forming surface shape error analysis step of analyzing the thickness reduction of the corner round portion of the temporary product generated after the cold forming step.
The method according to claim 2,
In the forming surface shape error analysis step, the thickness of the corner round portion of the temporary product is reduced using a forming surface error data map.
The method according to claim 2,
The mold design step,
The hot stamping method further comprising an inspection step of inspecting the strength and quality of a product produced after sequentially passing through the cold forming step, the mold trimming step, the heating step and the heat treatment step.
The method of claim 4,
The mold design step,
The hot stamping method further comprising a database storage step of database storage of the final cold forming mold that has passed the inspection step, the mold trim and the cold forming mold, and the modified content when the mold trim is produced.
delete The method according to claim 1,
In the mold trim design and mold trim manufacturing steps, a mold trim manufacturing step is performed when the mold trim design step is completed.
The method according to claim 1,
The hot forming prediction step and the thermal expansion analysis step predict the amount by which the temporary product expands and contracts using palm stamp software,
The hot stamping method, characterized in that the amount of shrinkage of the corner round portion of the temporary product in the curve surface shape error analysis step uses a curve surface error data map.

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