KR102155084B1 - Manufacturing method of hot stamping parts for local multifunctional materials by using three-dimensional lamination technology - Google Patents

Abstract

A method for manufacturing a mold for manufacturing a local multi-physical hot stamping part using a three-dimensional additive manufacturing technology according to the present invention includes the steps of designating a high-strength portion and a low-strength portion of the hot stamping product; Manufacturing a mold body; Manufacturing a hot stamping cooling block that can be combined on the mold body; And assembling the cooling block to the mold body and then processing the surface shape through mechanical processing to finally complete the mold; including, a product shape using metal lamination processing technology on the high-strength part on the hot stamping cooling block. It is characterized by forming the same cooling channel as.

Description

Manufacturing method of hot stamping parts for local multifunctional materials by using three-dimensional lamination technology {Manufacturing method of hot stamping parts for local multifunctional materials by using three-dimensional lamination technology}

The present invention maximizes cooling deviation through a method of selectively applying a cooling channel according to the required strength in order to manufacture a hot stamping part divided into a high-strength portion and a low-strength portion, and at the same time depositing metal powders having different thermal conductivity. Thus, it relates to a technology for manufacturing a mold for molding local multi-physical hot stamping parts.

In general, the method of manufacturing local multi-physical parts using a press mold is largely localized multi-physical hot stamping with heating objects such as electric cartridges in the mold using the rapid cooling characteristics of TWB (Tailor Welded Blank), TRB (Tailor Rolled Blank) and main steel. Component manufacturing technology is widely used.

First, TWB technology makes a blank material by contacting two materials having different material thicknesses or having the same material thickness but different tensile strengths, and then forming a blank material in a mold to make the thickness or tension of each other in one part. It is a technology to manufacture parts with different strengths.

Secondly, TRB technology refers to a technology for forming parts in a mold after manufacturing a steel plate having a continuous thickness change from a single steel plate through the control of a rolling roller during steel plate production.

Thirdly, the technology for manufacturing local multi-physical hot stamping parts with internal heating devices such as electric cartridges in the mold using the rapid cooling characteristics of the main steel is made of boron steel 22MnB5, which improves hardenability by adding elements such as B, Mn, and Cr. It is a technology that produces a local multi-physical hot stamping part by heating it to a high temperature above °C, moving it to a press, forming it at high temperature, and creating a cooling deviation artificially using a heating device in the mold.

However, looking at the conventional local multi-physical plate component manufacturing techniques as described above in terms of productivity, efficiency, and economy, TWB technology has to undergo an additional bonding process in manufacturing local multi-physical parts, and in the case of TRB technology, the thickness of each other. Although it is possible to apply different materials, there is a problem that the application is restricted because materials with different tensile strengths cannot be applied. In addition, the local multi-physical hot stamping part manufacturing technology using an in-mold heating device requires an additional heating device in the mold, so the cost of manufacturing the mold is high, and the efficiency and economy are low in terms of durability of the mold, productivity and maintenance during mass production. Has a drawback.

Republic of Korea Patent Publication No. 10-2102-0016777 "Hot stamping molding apparatus for local strength control and its molding method" (2012.02.27.) Republic of Korea Patent Publication No. 10-1581940 "Hot stamping mold with improved cooling performance" (2015.12.31.)

It is an object of the present invention to determine a high-strength part with high tensile strength and a low-strength part with low tensile strength in order to manufacture a mold for producing hot stamping parts with different strengths for each part, and then apply metal lamination processing technology to the high-strength part. When forming a mold by applying the same cooling channel as the product shape and laminating a metal powder of high thermal conductivity on the area to which the cooling channel is applied, at the same time not applying a cooling channel and laminating metal powder of low thermal conductivity on the low-strength portion. It provides a technical feature of manufacturing a mold for forming local multi-physical hot stamping parts by maximizing the difference in cooling between the high-strength and low-strength parts.

A method for manufacturing a mold for manufacturing a local multi-physical hot stamping component using a three-dimensional additive manufacturing technology according to the present invention for achieving the above object includes: designating a high-strength portion and a low-strength portion of the hot stamping product; Manufacturing a mold body; Manufacturing a hot stamping cooling block that can be combined on the mold body; And assembling the cooling block to the mold body and then processing the surface shape through mechanical processing to finally complete the mold; including, a product shape using metal lamination processing technology on the high-strength part on the hot stamping cooling block. It is characterized by forming the same cooling channel as.

The manufacturing of the cooling block includes forming a cooling channel groove of a semicircular shape on the upper surface of the hot stamping cooling block: forming a cooling channel having a circular cross section by assembling a semicircular shape on the upper surface of the cooling channel groove. ; Laminating and processing high thermal conductivity metal powder on the surface of the cooling block on which the cooling channel is formed; And completing the mold by assembling the cooling block on which the additive processing of the high thermal conductivity metal powder has been completed on the mold body.

After the high thermal conductivity metal powder lamination processing is performed, the step of heat-treating the cooling block to improve thermal conductivity and hardness; further includes.

The high thermal conductivity metal powder is HTCS-150 or HTCS-choftool material.

The cooling block employs any one of the low-cost Fe-based parent material group including S45C material, FC300, FCD550, 23F85, and H13 material.

According to the present invention, all the objects of the present invention described above can be achieved.

The present invention provides a method for manufacturing a mold for manufacturing a local multi-physical hot stamping part using a three-dimensional additive manufacturing technology, which enables removal of a heating device in the mold and cooling compared to the conventional local multi-physical hot stamping manufacturing technology. By optimizing the channel and applying high thermal conductivity metal powder, productivity is improved by shortening the pressing time during product molding.

The present invention lowers the manufacturing cost of the mold, and has improved durability and convenience in maintenance during mass production.

The present invention uses metal lamination processing technology for high-strength parts after determining a high-strength part with high tensile strength and a low-strength part with low tensile strength in order to manufacture a mold for producing hot stamping parts with different strengths for each part. The same cooling channel as the product shape is applied, and high thermal conductivity metal powder is laminated and processed on the area where the cooling channel is applied, and at the same time, the cooling channel is not applied and low thermal conductivity metal powder is laminated on the low-strength part. It maximizes the deviation of cooling between parts and parts that require low strength.

The present invention enables the production of local multi-physical parts having a tensile strength of 1500 MPa class and a 600 MPa class of tensile strength at the same time by applying the same plate product to molding in a mold.

The present invention utilizes the characteristics of boron steel having improved hardenability when cooling at a critical cooling rate (30°C/S) or higher after heating at 900°C or higher while applying the 3D metal additive processing technology.

1 shows a manufacturing process diagram of a cooling block applied to a portion requiring high strength among the cooling blocks for manufacturing local multi-physical hot stamping parts using a three-dimensional additive manufacturing technique according to the present invention.
2 shows a design concept of an MBR DASH CROSS mold applicable to the present invention.
3 shows the manufacturing sequence of the MBR DASH CROSS mold to which the present invention is applied.
Figure 4 shows the oil-treated heat treatment process of HTCS-150 material after surface lamination processing.
5 shows an oil-cohftool heat treatment process of HTCS-cohftool material after surface lamination processing.
Figure 6 shows the final production finished mold of the MBR DASH CROSS mold to which the present invention is applied.
7 is a prototype cooling in the mass production condition of the MBR DASH CROSS mold to which the present invention is applied.
It shows the evaluation of each performance and the tensile strength of the molded product.

Hereinafter, the configuration and operation of the embodiment of the present invention will be described in detail with reference to the drawings.

Prior to the description of the present invention, a device that prints a three-dimensional object using metal powder as a toner is referred to as a three-dimensional metal printer, and the direct energy deposition (DED) technology is one of three-dimensional metal printing (additive processing) technologies. .

The hot stamping technology to which the present invention is applied is a technology that can simultaneously satisfy the weight reduction of the vehicle and the improvement of the collision characteristics, and a boron steel plate 22MnB5 material with improved hardenability by adding elements such as B, Mn, and Cr to a high temperature of 900°C or higher. A molding method that produces high-temperature molding in the mold by moving it to a press after heating, and at the same time quenching at a critical cooling rate (30℃/S) or higher to produce an existing tensile strength 600MPa class material into a tensile strength 1500MPa class ultra-high strength part. to be.

The material to which the hot stamping technology is applied has superior weight reduction and safety improvement effect compared to the existing high-strength materials, and is mainly applied to parts such as side impact beams, bumpers, A and B pillars, roof rails, and Mbr dash cross of automobiles.

The present invention provides a technique for a method of manufacturing a mold for manufacturing a local multi-physical hot stamping part using a three-dimensional additive manufacturing technique.

In the process of manufacturing a cooling block for hot stamping parts that require differential cooling, the present invention determines a high-strength portion with a tensile strength of 1500 MPa and a low-strength portion with a tensile strength of 600 MPa, and then applies metal lamination processing technology to the high-strength portion. By using the same cooling channel as the product shape, the cooling effect is maximized during molding by laminating and processing materials such as HTCS-150 and HTCS-Choftool, which are commonly used high thermal conductivity metal powders, on the surface of the cooling block.

On the other hand, in the area corresponding to the low-strength part of the cooling block, the cooling channel applied to the high-strength part is not applied to minimize the cooling effect, and the GTCS material, which is a commercial low thermal conductivity metal powder, is laminated and formed on the surface of the cooling block. In this case, a mold for molding local multi-physical hot stamping parts is manufactured by maximizing the difference in cooling between the high-strength required part and the low-strength required part.

HTCS-150 material, a high thermal conductivity metal powder material applied to the cooling block for hot stamping parts, is C 0.32~0.42, Cr 0.07~0.1, Cu 0.01~0.1, Mn 0.5 or less, Mo 4.0~4.30, Ni 0.1 by weight %. It is characterized in that ~0.01, P 0.03 or less, Si 0.1 to 0.8, W 2.5 to 3.0, S0.03 or less and the balance is composed of Fe.

The metal powder of HTCS-cohftool material is C 1.5~1.8, Cr 0.05~0.1, Cu 13~14, Mn 0.20 or less, Mo 5.5~6.0, Ni 0.03~0.10, Si 1.0~1.5, W 3.3~3.8, It is characterized in that S 0.03 or less and the balance consist of Fe.

HTCS-150 material and HTCS-cohftool material, which are applied to high-strength parts, are subjected to oil quenching in each heat treatment process to improve thermal conductivity after lamination on the cooling channel formed in the cooling block, and then the cooling block of the hot stamping mold is manufactured. .

First, as a first step, high-strength and low-strength areas are designated in the hot stamping product.

The mold body is manufactured in two steps.

In the third step, a cooling block constituting the hot stamping mold is manufactured.

The high-strength portion of the cooling block is manufactured with a cooling channel having the same shape as the hot stamping product by using an additive manufacturing technique.

The cooling channel is formed on the cooling block body by processing a semicircular channel groove shape, and then separately fabricating a semicircular coupon and assembling and adjoining the cooling block body on the basis of the channel groove.

As described above, for example, after manufacturing a cooling channel having the same conformal shape as the shape of the cylindrical hot stamping product, the surface of the cooling channel that directly contacts the hot stamping product during molding has a high thermal conductivity of 10 mm in thickness. The cooling block is manufactured by laminating metal material, and the cooling block is manufactured through an oil quenching heat treatment process and surface machining, centering on the laminated metal material of high thermal conductivity.

On the other hand, in the case of manufacturing the cooling block, the low-strength required part is applied by using a low thermal conductivity material with a thickness of 10 mm on the surface that directly contacts the hot stamping product during molding without processing a separate cooling channel. To manufacture the cooling block.

In step 4, the manufactured cooling blocks are assembled to the mold body, and the surface shape is processed through mechanical processing to finally complete the mold manufacturing.

Referring to FIG. 1, a manufacturing process diagram of a cooling block applied to a portion requiring high strength among the cooling blocks for manufacturing local multi-physical hot stamping parts using a three-dimensional additive manufacturing technique according to the present invention will be described.

The method of manufacturing the cooling block corresponding to the high strength required part of the hot stamping product is as follows.

First, the first step is fabricated by processing a semicircular cooling groove on the cooling block body. That is, a cooling channel groove having a semicircular cross-sectional shape is formed on the upper surface of the hot stamping cooling block using a low-cost metal material.

In the second step, a coupon is produced to make a circular shape in the shape of a cooling channel.

In step 3, a cooling channel having a circular cross-sectional shape is implemented by assembling a coupon on the main body of a cooling block having a cooling groove in a semicircular shape, and it is temporarily bonded and fixed to prevent deformation during metal lamination.

In step 4, metal powder of high thermal conductivity is laminated on the surface of the cooling channel. That is, the high thermal conductivity metal powder is laminated on the surface of the cooling block on which the circular cooling channel is formed.

In step 5, the surface of the laminated metal is machined on the cooling channel to finally produce a block.

Thereafter, the cooling block on which the lamination process is completed is finally machined and bonded to the mold body to complete the mold.

2 shows a design drawing of an MBR DASH CROSS mold capable of manufacturing a local multi-physical hot stamping part to which the present invention is applied, and shows a specific application example of the technology according to the present invention.

The central portion corresponds to the low-strength portion, and does not apply a cooling channel. On the surface of the cooling block, metal powder of low thermal conductivity is laminated.

The right and left portions are regions corresponding to the high-strength portion, and metal powders of high thermal conductivity are laminated and processed, and cooling channels having the same conformal shape as the product shape are applied.

3 shows the manufacturing procedure of the MBR DASH CROSS mold to which the present technology is applied.

4 shows an oil treatment process of HTCS-150 material, a high thermal conductivity metal powder, on the surface of a cooling block having a cooling channel.

The heat treatment process proceeds in the order of Austenzation, Quenching and Tempering.

First, the Austenzation process will be described.

Before introducing the HTCS-150 material, keep the furnace temperature below 100℃. After inputting the HTCS-150 material, heat it to 100℃~650℃ for 4 hours at 150℃/h.

Homogenization treatment at 650° C. for 2 hours, and heating at 150° C./h to 650° C. to 750° C. for 45 minutes.

It is homogenized at 750°C for 2 hours, and heated to 750°C to 900°C at 50°C/h for 3 hours.

Heat from 900°C to 1120°C at 150°C within 1 hour and 30 minutes, and homogenize at 1120°C for 45 minutes.

Next, the quenching process will be described.

Rapid cooling treatment using oil, preheating the oil to 60℃, and then rapid cooling treatment (30 minutes).

Do the maximum agitation of the oil (stirring).

During quenching, maintain a pressure of at least 1 bar in the vacuum chamber.

Finally, the tempering process is explained.

After homogenization treatment at 590℃ for 210 minutes, it is furnace cooled or air cooled.

FIG. 5 shows a heat treatment process of oil and water after surface lamination processing of HTCS-cohftool material, which is a high thermal conductivity metal powder, on the surface of a cooling block having a cooling channel.

First, the Austenzation process will be described.

Before introducing the HTCS-cohftool material, keep the temperature of the electric furnace below 100℃. After inputting the HTCS-150 material, heat it to 100℃~650℃ for 5 hours and 30 minutes at 100℃/h.

Homogenization treatment at 650°C for 1 hour, and heating at 150°C/h to 650°C to 750°C for 40 minutes.

Homogenized treatment at 750° C. for 1 hour, and heated to 750° C. to 920° C. at 30° C./h for 5 hours and 40 minutes.

Heat from 920°C to 1080°C at 100°C within 1 hour and 30 minutes, and homogenize at 1080°C for 45 minutes.

Next, the quenching process will be described.

Rapid cooling treatment using oil, preheating the oil to 80℃ and then rapid cooling treatment.

Do the maximum agitation of the oil (stirring).

When quenching, maintain a pressure of at least 1 bar in the vacuum chamber.

Finally, the tempering process is explained.

The first tempering is heated from 100℃ to 540℃ for 3 hours and 15 minutes at 150℃/h, and then kept at 540℃ for 2 hours. After aging to 80℃~100℃, when the material reaches 80℃~100℃, 2 Start tempering the car.

Secondary tempering is heated from 100℃ to 590℃ for 3 hours at a heating rate of 150℃/h and maintained at 590℃ for 2 hours. After furnace cooling or air cooling, the third tempering starts when the material reaches 100℃.

The 3rd tempering is heated from 100℃ to 600℃ at a heating rate of 150℃/h, maintained at 600℃ for 2 hours, and cooled by furnace or air.

6 shows the final fabrication of the MBR DASH CROSS mold to which the technology according to the present invention is applied.

7 shows the cooling performance evaluation and tensile strength evaluation of the molded product during mass production conditions of the hot stamping mold for molding MBR DASH CROSS parts to which the technology according to the present invention is applied.

From the evaluation results, it was verified that it is possible to manufacture a mold for manufacturing local multi-physical hot stamping parts using only the optimization of the cooling channel and the thermal conductivity of the material without a separate heating device in the mold.

In addition, it has been verified that the cooling performance is excellent, and it is possible to improve the pressing time during molding by more than 40% compared to the mold using the existing touch reel, so that there is a remarkable effect in increasing the production volume during mass production.

In the technology according to the present invention, when boron steel is cooled faster than the critical speed during molding, most of the austenite structure inside the material is transformed into a martensitic structure and has a high tensile strength of 1500 MPa, while a speed slower than the critical speed. In the case of cooling, it focuses on the feature of lowering the strength along with the formation of a structure such as bainite, ferrite, and pearlite.

As described above, the present invention provides a method for manufacturing a mold for manufacturing local multi-physical hot stamping parts using a three-dimensional additive manufacturing technology, and it is possible to remove the heating device in the mold compared to the conventional local multi-physical hot stamping manufacturing technology. In addition, by optimizing the cooling channel and applying high thermal conductivity metal powder, productivity is improved by shortening the pressing time during product molding. In addition, since there is no application of a heating device in the mold, it is possible to reduce mold manufacturing cost, improve durability, and secure maintenance convenience.

Although the present invention has been described through the above embodiments, the present invention is not limited thereto. The above embodiments may be modified or changed without departing from the spirit and scope of the present invention, and those skilled in the art will recognize that such modifications and changes also belong to the present invention.

Claims (5)

Designating a high-strength portion and a low-strength portion of the hot stamping product;
Manufacturing a mold body;
Manufacturing a hot stamping cooling block that can be combined on the mold body; And
Assembling the cooling block to the mold body and then machining the surface shape through machining to finally complete the mold; Including,
The step of manufacturing the cooling block,
Forming a semicircular cooling channel groove on the upper surface of the hot stamping cooling block:
Forming a cooling channel having a circular cross section by assembling a semicircular shape on the upper portion of the cooling channel groove;
Laminating and processing high thermal conductivity metal powder on the surface of the cooling block on which the cooling channel is formed;
After the high thermal conductivity metal powder lamination processing is performed, heat treatment of the cooling block to improve thermal conductivity and hardness; And
Comprising the step of assembling the cooling block in which the additive processing of the high thermal conductivity metal powder has been completed on the mold body to complete the mold,
In the step of improving the thermal conductivity and hardness, an oil quenching heat treatment process is performed around the laminated metal powder of high thermal conductivity,
The oil quenching heat treatment process,
Austenitization, Quenching and Tempering are performed sequentially,
The Austenitization process
Keep the temperature of the electric furnace below 100℃ before putting the high thermal conductivity metal powder material, and heat it to 100℃~650℃ for 4 hours at 150℃/h or 100℃~650℃ after putting the high heat conductivity metal powder material Heating at 100°C/h for 5 hours and 30 minutes, homogenizing treatment at 650°C for 1 hour or 2 hours, and heating at 150°C/h to 650°C to 750°C for 40 minutes or 45 minutes, 750 Homogenizing treatment at ℃ for 1 hour or 2 hours, heating to 750 ℃ ~ 900 ℃ 50 ℃ / h for 3 hours or heating at 30 ℃ / h for 5 hours 40 minutes, 100 ℃ to 920 ℃ ~ 1080 ℃ Or heating at 150° C. within 1 hour and 30 minutes, and homogenizing at 1080° C. or 1120° C. for 45 minutes,
Quenching process is a step of rapid cooling treatment using oil, preheating the oil to 60℃ or 80℃, and then quenching (30 minutes), performing the maximum agitation of the oil (agitating), and in the vacuum chamber during quenching. Including the step of maintaining a pressure of at least 1 bar or more,
The tempering process is furnace-cooled or air-cooled after homogenization in single or multiple stages,
The hot stamping cooling block, characterized in that to form the same cooling channel as the product shape by using a metal lamination processing technology in the high-strength area,
A method of manufacturing a mold for manufacturing local multi-physical hot stamping parts using 3D additive manufacturing technology.
delete delete The method of claim 1,
The high thermal conductivity metal powder adopts HTCS-150 or HTCS-choftool material,
The HTCS-150 material is C 0.32~0.42, Cr 0.07~0.1, Cu 0.01~0.1, Mn 0.5 or less, Mo 4.0~4.30, Ni 0.1~0.01, P 0.03 or less, Si 0.1~0.8, W 2.5~ 3.0, S0.03 or less and the balance consists of Fe,
The HTCS-cohftool material is C 1.5~1.8, Cr 0.05~0.1, Cu 13~14, Mn 0.20 or less, Mo 5.5~6.0, Ni 0.03~0.10, Si 1.0~1.5, W 3.3~3.8, S 0.03 by weight% The following and the balance consist of Fe,
A method of manufacturing a mold for manufacturing local multi-physical hot stamping parts using 3D additive manufacturing technology.
The method of claim 1,
The cooling block adopts any one of the low-cost Fe-based parent material group including S45C material, FC300, FCD550, 23F85, and H13 material,
A method of manufacturing a mold for manufacturing local multi-physical hot stamping parts using 3D additive manufacturing technology.

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