KR102125385B1 - Heating method for hot stamping - Google Patents

Abstract

The present invention relates to a blank heating method. Introduced is the blank heating method which can improve productivity and reduce cost. A blank is heated by using a heating device in which a heating chamber into which the blank is input is arranged in a multistage vertically. Equal to or more than two heating devices are arranged in parallel in the width direction, and blanks are fed to heating devices arranged in parallel in the width direction at different times so that the blanks are discharged from the heating devices arranged in parallel at different times.

Description

Blank heating method {HEATING METHOD FOR HOT STAMPING}

The present invention relates to a blank heating method for hot stamping, and particularly to a blank heating method using a heating device in which a plurality of heating chambers are vertically arranged in multiple stages.

The demand for weight reduction and high strength of vehicle parts is very high due to the regulation of fuel efficiency and strengthening of safety regulations. As a result, 1-giga Pascal (GPa) grade ultra-high-strength steel parts have been commercialized, and recently, 2 giga-grade steel has been promoted.

In general, when the strength of the steel sheet increases, the elongation decreases, resulting in poor workability. Hot stamping is proposed to solve this problem. Hot stamping is excellent in workability since the steel sheet is heated at a temperature of at least austenitizing temperature, for example, 900°C or higher, and rapidly cooled at the same time as press forming.

In the conventional hot stamping, an electric furnace for heating while continuously transporting a steel sheet was mainly used. Such an electric furnace requires a large space, the process speed is slow, and the maintenance cost is high. Korean Patent Registration No. 1045839 introduces a hybrid heating furnace that combines high-frequency induction heating with an electric furnace.

The above hybrid heating furnace ensures a reduction in process time, a reduction in facility space, and a reduction in maintenance costs compared to a conventional electric furnace. However, hybrid heating furnaces also have limitations. Despite the significant process improvement and cost reduction, the length of the electric furnace used as the secondary heating furnace is still long, and there is still a need to increase productivity and reduce costs.

The application of hot stamping parts is expanding due to the increasing demand for lighter vehicles. In order to improve the productivity of blank heating for hot stamping, it is necessary to shorten the heating time or to extend the heating furnace for a long time to inject more blanks to heat treatment. The shortening of the heating time is limited and the long extension of the heating furnace causes an increase in initial equipment cost and operating cost.

In addition to continuous heating furnaces such as electric furnaces, batch heating furnaces can be used for hot stamping. The batch type occupies less space than the continuous type, and is superior to the continuous type in terms of production cost and maintenance cost. However, even if the batch type is provided with a multi-stage heating chamber, only one steel plate is put into one heating chamber and the productivity is deteriorated because it must wait until heating is completed.

The present invention is based on the recognition of the prior art as described above, and to provide a blank heating method capable of improving productivity and reducing costs.

The problems to be solved in the present invention are not necessarily limited to the above-mentioned matters, and other problems not already mentioned may be understood by the matters described below.

The present invention for achieving the above object is to heat the blank by using a heating device that is arranged in multiple steps up and down heating chambers partitioned from each other in the housing. This multi-stage heating device can be arranged in parallel in two or more rows in the width direction. When the heating devices are arranged in two rows in the width direction, the blanks are alternately input and taken out from the first heating device on the left and the second heating device on the right. The blank transfer speed of the first heating device and the second heating device may be the same.

A heater in the heating chamber of the heating device; A door provided at one end in the longitudinal direction and at the other end; Supports extending in the longitudinal direction and spaced apart in the width direction; And a work beam extending in the longitudinal direction and alternately arranged with the support in the width direction.

According to the present invention, the work beam is connected to a rotation bar arranged in the width direction, and the rotation bar rotates in a circle around a rotation axis in the width direction, and is supported by rotational motion of the work beam by rotational motion of the rotation bar. The blank placed on can be transferred from the inlet side to the outlet side. The work beam can be placed above the support at the top dead center of rotational behavior and below the support at the bottom dead center.

According to the present invention, protrusions spaced apart along the longitudinal direction may be provided on the upper surface of the work beam. Protrusions spaced apart along the longitudinal direction may also be provided on the upper surface of the support. Furthermore, protrusions arranged spaced apart along the longitudinal direction may be provided on the lower surface of the work beam and/or the lower surface of the support.

According to the present invention, the work beam and the support may be hollow in a longitudinally elongated shape.

According to the present invention, the work beam is connected to a rotating bar via a bracket, and the bracket comprises a base fixed to the rotating bar; Legs extending from the base so that both right and left sides of the work beam are in close contact; And a support connecting the legs so that the lower surface of the work beam is supported. The work beam can be fastened and fixed between the legs by a first fastener penetrating the leg and the work beam. In addition, the base is fixed to the rotating bar by the second fastener, it can be configured to be adjusted to the fixed height of the bracket by the operation of the second fastener.

In addition, according to the present invention, the heating chamber is partitioned by a heat-resistant beam, and the heat-resistant beam is extended in the longitudinal direction so that both ends thereof are fixed to the housing and arranged closely in the width direction to form the bottom of the heating chamber.

In addition, according to the present invention, the support can be fixed by fitting both ends of the support block provided on the inlet side and the outlet side of the heating chamber, respectively. The support block has a seating groove through which the support is fitted and a recess through which the work beam passes, and the recess is formed deeper and wider than the seating groove, and the fork can be inserted into the support block from the outside against the corresponding part of the other support block. A horizontal extension is provided to form the opening, and the door can be provided to open and close the opening.

According to the present invention as described above, the heating device is configured in a batch type, so that the occupied space is small and it is possible to reduce manufacturing and maintenance costs.

Further, according to the present invention, the blank inputted to the inlet side of the heating chamber is heated while being transferred to the outlet side, and thus productivity is excellent. In the heating chamber, the blank is transported while repeating transport and stop by a rotating work beam. Transfer and stop of the blank can be adjusted in consideration of the target heating temperature and the length of the heating chamber.

In addition, according to the present invention, since the heated blanks can be alternately discharged from the first heating device and the second heating device, the waiting time of the press molding mold disposed at the rear end of the heating devices is shortened and productivity is improved.

In addition, according to the present invention, the life of the work beam and the support is long, heat loss from the heating chamber is small, and repair and correction are easy.

1 shows an example of a blank heating device for hot stamping.
FIG. 2 shows a blank transfer method of the heating device shown in FIG. 1.
3 and 4 show the damaged work beam and the support, respectively, after being used in the heating device shown in FIG. 1.
5 shows a blank heating device according to an embodiment.
FIG. 6 shows the inlet side of the heating device shown in FIG. 5.
7 shows a work beam according to an embodiment, a rotating bar and a bracket that combines them.
8 shows the bottom of the heating chamber according to the embodiment.
9 shows a support beam and a work beam installed in a heating chamber according to an embodiment.
10 shows a support block according to an embodiment.
11 is a schematic diagram showing the structure of a projection according to an embodiment.
12 shows a support on which a projection is formed according to an embodiment.
13 shows a blank heating device according to another embodiment.

Hereinafter, examples will be described in more detail to understand various characteristic aspects of the present invention. In the accompanying drawings, identical or equivalent components or parts may be denoted with the same reference numerals as possible for convenience of description, and the drawings are exaggerated and schematically illustrated for a clear understanding and explanation of the features of the present invention. Can be.

In the description of the present invention, unless otherwise specified, the second element is disposed on the first element'on' or that the two elements are'connected' to each other, as well as the two elements directly contact each other, the first and the first It needs to be understood to mean that a third element is interposed between the elements of the two elements. It is also necessary to understand that the direction expressions such as front and rear, left and right or up and down are for convenience of explanation.

1 shows a blank heating device in which a batch type and a continuous type are mixed. In FIG. 1, the length direction corresponding to the blank transfer direction is indicated by L, and the left and right width directions are indicated by W.

Referring to FIG. 1, the heating device has a structure in which the heating chambers 10 partitioned from each other in the housing 100 are stacked and arranged in multiple stages.

On the bottom side of the heating chamber 10, a support 20 and a work beam 30 extending in the longitudinal direction are alternately arranged in the width direction, and a heater 40 extending in the width direction is spaced along the length direction on the ceiling side. do. The blank introduced into the heating chamber 10 from the inlet side is transferred to the outlet side by the work beam 30.

On the inlet and outlet sides of the heating chamber 10, rotation bars 50 extending in the width direction are provided. One end of the work beam 30 is connected to the rotating bar 50 on the inlet side and the other end is connected to the rotating bar 50 on the outlet side. Each rotary bar 50 rotates in a circular motion around a rotation axis in the width direction, and the work beam 30 is rotated by the rotary bar 50.

On the inlet side of the heating device, an electric motor 110 for rotational movement of the rotating bar 50 is provided. The driving force of the electric motor 110 may be transmitted to the rotating bar 50 through the gear box 120 and a rotating body (not shown). The rotation of the rotating bar 50 can be by various methods. As one example, the rotational movement of the rotating bar 50 may be by an electric driven crankshaft.

The exit side rotation bar 50 may be driven simply by the rotational movement of the entrance side rotation bar 50 or may be actively rotated by the electric motor 110 like the entrance side rotation bar 50.

In Figure 2, the rotational motion of the work beam 30 and the blank transfer process thereby are shown in order.

As shown in FIG. 2, the work beam 30 connected to the rotational bar 50 arranged in the width direction exhibits a rotational motion of drawing a circle similarly by the rotational motion of the rotational bar 50. The driving force of the electric motor 110 is transmitted to the rotating body 130 via the gear box 120, and the rotational motion of the rotating body 130 is transmitted to the work beam 30 eccentrically connected to the rotating body 130.

2(a) shows a state in which the work beam 30 is placed at the bottom dead center of the rotational behavior, and at the bottom dead center, the work beam 30 is placed below the support 20. The blank 1 introduced into the inlet side of the heating chamber 10 is placed on the support 20.

2(b) shows a state in which the work beam 30 is rotated by the driving force of the electric motor 110 and placed at the top dead center, and the work beam 30 is placed above the support at the top dead center. In the process from the bottom dead center to the top dead center, the blank 1 placed on the support 20 is moved to the work beam 30 and moved.

As shown in (c) and (d) of FIG. 2, the blank 1 placed on the work beam 30 in the process from the top dead center to the bottom dead center is transferred to the exit side, and the blank placed on the work beam 30 (1) is moved back to the support (20).

As can be seen in FIG. 2, the blank 1 in the heating chamber 10 is conveyed while repeating conveying and stopping by the work beam 30 rotating. The electric motor 110 operates at a predetermined interval to rotate the work beam 30. By adjusting the size, rotation speed and period (or rotation interval) of the rotational trajectory of the work beam 30, the residence time of the blank 1 or the average transfer speed in the heating chamber 10 can be adjusted.

The heating device as described above can shorten the length of the heating chamber 10, that is, the length of the heating device, and heat it as in a continuous furnace by introducing several blanks into the heating chamber 10. This not only reduces installation and maintenance costs, but also ensures considerable productivity.

In spite of the above many advantages, the heating device needs to be improved.

3A shows a damaged work beam 30 after being used in the heating device shown in FIG. 1.

As a hot stamping blank, Al plated steel sheet is mainly used. The heating device is controlled to form an oxide film before the Al plating melts in the heating chamber 10. However, a part of the Al plating is melted and a phenomenon occurs on the work beam 30, and as the process continues, odour of Al plating accumulates and diffusion into the work beam 30 progresses. Al plating penetrates into the work beam 30 of the ceramic material to form a hard structure A having a high hardness (see FIG. 3B).

As shown in FIG. 3A, the hard tissue A due to the diffusion of Al plating is formed as a wave pattern, and cracks are mainly generated in the boundary area A2 between the areas A1 deeply penetrated by Al plating. In the process of thermal expansion and contraction of the work beam 30 due to the interruption of operation and resumption, it is believed that cracks are generated due to a difference between the region A1 where the hardening has progressed and the region A2 which is relatively soft. Due to such cracks and breaks, the life of the work beam 30 is very short and frequent operation stoppage is caused.

4 shows a damaged support 20 after being used in the heating device shown in FIG. 1.

The support 20 is formed in a ⊥ shape with a wide base and a blank support extending vertically. The support 20 is made of ceramic, like the work beam 30, which has a slightly longer life than the work beam 30, but is damaged due to its own weight and hard structure due to penetration of Al plating.

5, the front side of the blank heating apparatus according to the embodiment, that is, the inlet side is shown. Parts that are not specifically described below may be understood to be the same as the heating device described above, and reference numerals are used as they are.

As shown in FIG. 5, the heating device has a structure in which seven heating chambers 10 partitioned from each other in the housing 100 are stacked. The entrance of the heating chamber 10 is provided with a fork entrance 11 for introducing a blank. The fork is mounted on the robot arm, and the blank is put on it and transferred to be input into the heating chamber 10.

6 is an enlarged view of a part of the front surface of the heating apparatus shown in FIG. 5. The entrance of the first chamber 10a is closed by the door 140, and the entrances of the second and third chambers 10b and 10c are open.

Referring to FIG. 6, the work beams 30 are arranged spaced apart in the width direction of the heating chamber 10, and although not shown, a support 20 is provided between the work beams 30 and the work beams 30 adjacent thereto. Is placed. The entrance of the heating chamber 10 is provided with a fork entrance 11 in the longitudinal direction, and the door 140 provided at the entrance side opens and closes the fork entrance 11. The door 140 is opened for the introduction of the blank, and the entrance of the heating chamber 10 is closed by the door 140 after inserting the blank. The opening and closing operation of the door 140 is caused by the rotational operation of the rod 141 extending in the width direction.

7 shows the work beam 30 fixed to the rotating bar 50 using the bracket 60.

The work beam 30 is formed in a longitudinally elongated shape when viewed in cross section, and is hollow inside the hollow in the longitudinal direction. For example, the work beam 30 can be understood as a hollow pipe having a rectangular cross section with rounded corners. The work beam 30 is lightweight and reduces the possibility of cracks or breakage due to thermal expansion and contraction.

The bracket 60 includes a base 61 fixed to the rotating bar 50, legs 62 extending from the base 61 so that both right and left sides of the work beam 30 are in close contact, and a bottom surface of the work beam 30 The support 63 is provided to horizontally connect the legs 62 so as to be supported.

The work beam 30 is fastened and fixed between the legs 62 by the first fastener 64 passing through the leg 62 and the work beam 30 in the horizontal direction. The base 61 is fixed to the rotating bar 50 by a second fastener 65. As the second fastener 65, a headless bolt may be used to easily adjust the height of the bracket 60, that is, the height of the work beam 30.

8 is a view showing that the heat-resistant beams 70 constituting the bottom of the heating chamber 10 are closely arranged in the width direction.

Since the temperature in the heating chamber 10 is very high at 900° C. or higher, it is not possible to install a steel plate to partition between adjacent heating chambers. On the other hand, if the neighboring heating chambers are not partitioned from each other, it is difficult to control and maintain the temperature in the heating chamber 10.

The partition between neighboring heating chambers 10 is made using a heat-resistant beam 70 of ceramic material. The heat-resistant beam 70 is extended in the longitudinal direction, and both ends thereof are mounted and fixed to the housing 100. It would be nice if there was a member for supporting it in the middle of the longitudinal direction of the heat-resistant beam 70, but due to the high temperature environment in the heating chamber 10, the intermediate support member is limited. At high temperatures, the heat-resistant beam 70 is broken by its own weight. The broken heat-resistant beam 70 can be replaced with a relatively new one, and can be used upside down if the damage is not severe.

8 and 9, the support block 80 is arranged in the width direction in close contact with the bottom of the heating chamber 10 on the inlet and outlet sides. The support 20 is fixed to both ends of the support block 80 on the inlet and outlet sides. The support block 80 facilitates replacement or repair as well as installation of the support 20. The support 20 only has both ends fixed to the support block 80. In the middle of the support 20 or the work beam 30, a member for supporting them is not provided.

10 shows an example of a support block 80 according to an embodiment.

9 and 10, the support block 80 includes a seating groove 81 into which the support 20 is fitted and a recess 82 through which the work beam 30 passes. The recess 82 is deeper and wider than the seating groove 81 to allow rotational movement of the work beam 30. The support block 80 is provided with a horizontal extension 83 for forming an entrance 11 through which a fork can be entered from the outside by facing a corresponding part of another support block.

In FIG. 11, projections 31 formed on the work beam 30 are schematically illustrated to prevent cracks due to penetration of Al plating.

9 and 11, the projections 31 are arranged along the lengthwise direction on the upper surface of the work beam 30 to which the blank 1 is contacted. The projection 31 is preferably formed to a width of 2.0 to 3.0 mm (or a thickness in the longitudinal direction) and a height of 2.0 to 3.0 mm. And it is preferably formed at a distance of 80.00mm. When the projections 31 are formed in this way, the life of the work beam 30 increases by an average of 2 times or more.

The width of the projection 31 less than 2.0 mm or more than 3.0 mm in height causes difficulties in processing and does not guarantee an effect beyond that obtained from 2.0 to 3.0 mm. When the width of the projection 31 is greater than 3.0 mm or less than 2.0 mm, the tendency for the amount of dyeing and penetration depth of the Al plating to increase is increased or the variability of the obtained state becomes large. The spacing between the projections 31 needs to be adjusted according to the shape or size of the blank, but the spacing between about 80.00 mm is preferred based on the blank being applied.

The projection 31 may be formed on the lower surface as well as the upper surface of the work beam 30. After using the upper surface of the work beam 30 to support the blank, if there is still no problem of cracking or breaking, it can be used in such a way that the lower surface of the work beam supports the blank, and helps to extend the life of the work beam 30. do.

In FIG. 12, a support 20 fitted to the support block 80 is shown.

9 and 12, the projections 21 are spaced apart along the longitudinal direction on the upper surface of the support 20 to which the blank 1 is contacted. The projections 21 are formed in the same numerical range as the projections 31 of the work beam 30. The projection 31 may be formed on the lower surface as well as the upper surface of the support 20, and may be used upside down after a certain period to extend the life.

The support 20 is similar to the work beam 30, and may be formed in a hollow shape with an empty inside in the longitudinal direction as an elongated shape in the longitudinal direction when viewed in cross section. The support 20 is lightweight and reduces the possibility of cracks or breakage due to thermal expansion and contraction.

13 shows a blank heating device according to another embodiment.

Referring to FIG. 13, the blank heating device includes a first heating device 101 and a second heating device 102 arranged in parallel in the width direction. The first and second heating devices 101 and 102 may be configured in the same manner as the heating devices according to the above-described embodiment.

A partition wall 103 may be provided between the first heating device 101 and the second heating device 102, and each heating device may be provided with an electric motor 110 for rotational movement of the rotating bar 50, respectively. You can. Blank transfer speeds of the first heating device 101 and the second heating device 102 may be the same. Of course, it would not be impossible to set the feed rate differently.

A blank heating method according to an embodiment will be described with reference to FIG. 13.

At each inlet side, the blanks are alternately fed to the first heating device 101 and the second heating device 102. As an example, a blank is introduced into the first heating apparatus 101, and then a blank is injected into the second heating apparatus 102 at a time interval. Blank transfer speeds of the first heating device 101 and the second heating device 102 may be the same, and alternately heated blanks may be discharged in the order in which they are input at each outlet of the devices 101 and 102.

One robot having a fork may be disposed on the inlet side and the outlet side of the heating devices 101 and 102, respectively.

The first and second heating devices 101 and 102 have a structure in which the heating chambers 10 into which blanks are input are arranged vertically. Referring to FIG. 13, the heating chambers 10 of the first and second heating devices 101 and 102 are respectively arranged in seven stages in the vertical direction. According to such a heating device, even if the blank heating time itself in the heating chamber 10 is not shortened, it is possible to heat many blanks at once. Since the blank cooling performance of the press molding machine is improving, it is possible to dramatically improve productivity by appropriately adjusting the input and discharge of the blanks.

Although it has been described and described with respect to specific embodiments of the present invention, it is necessary to understand that the present invention can be variously modified or modified without departing from the technical spirit of the invention described in the following claims.

10: heating chamber 11: fork entrance
20: Support 21, 31: projection
30: work beam 40: heater
50: swivel bar 60: bracket
70: heat-resistant beam 80: support block
100: housing 110: motor

Claims (5)

As a blank heating method using a heating device in which the heating chamber in which the blank is introduced is vertically arranged in multiple steps,
Two or more of the heating devices are arranged in the width direction in parallel, and the blanks are discharged at different times from the heating devices arranged in parallel at different times by inputting the blanks to the heating devices arranged in the width direction in parallel,
The heating chamber includes a heater; A door provided at one end in the longitudinal direction and at the other end; Supports extending in the longitudinal direction and spaced apart in the width direction; And a work beam extending in the longitudinal direction and arranged alternately with the support in the width direction,
The work beam is connected to a rotating bar arranged in the width direction, and the rotating bar rotates in a circle around a rotation axis in the width direction, and is raised on the paper table by the rotational motion of the work beam by the rotational motion of the rotating bar. The blank is transferred from the inlet side to the outlet side, and the work beam lies above the support at the top dead center of the rotational behavior and below the support at the bottom dead center,
Protrusions arranged spaced apart along the longitudinal direction are provided on at least the upper surfaces of the work beams and the support,
The work beam is connected to the rotating bar via a bracket,
The bracket includes a base fixed to a rotating bar; Legs extending from the base so that both right and left sides of the work beam are in close contact; And a support connecting the legs so that the lower surface of the work beam is supported.
The work beam is fastened and fixed between the legs by a first fastener penetrating the leg and the work beam,
The base is fixed to the rotating bar by a second fastener, the blank heating method, characterized in that configured to adjust the fixed height of the bracket by the operation of the second fastener. The method according to claim 1, The work beam and the support is a blank heating method, characterized in that the hollow in the longitudinally elongated shape. The method according to claim 1, The projection is 2.0 ~ 3.0mm width, blank heating method, characterized in that formed in a height of 2.0 ~ 3.0mm. delete The method according to claim 1, The heating chamber is divided by a heat-resistant beam, the heat-resistant beam is extended in the longitudinal direction, both ends are fixed to the housing and arranged in close contact in the width direction to constitute the bottom of the heating chamber,
The support is fitted and fixed at both ends of the support blocks provided on the inlet and outlet sides of the heating chamber,
The support block is provided with a seating groove through which the support is fitted and a recess through which the work beam passes, the recess is formed deeper and wider than the seating groove, and the support block is engaged with a corresponding portion of another support block to enter the fork from the outside. A blank heating method characterized in that a horizontal extension is provided to form a possible opening, and the door is provided to open and close this opening.

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