GB2505048A

GB2505048A - Hot shaping die for manufacture of steel shaped parts

Info

Publication number: GB2505048A
Application number: GB1310880.8A
Authority: GB
Inventors: Manuel Koster; Maik Winderlich; Wolfgang Buhr
Original assignee: GEDIA Gebrueder Dingerkus GmbH
Current assignee: GEDIA Gebrueder Dingerkus GmbH
Priority date: 2012-06-22
Filing date: 2013-06-19
Publication date: 2014-02-19
Anticipated expiration: 2033-06-19
Also published as: FR2992329A1; DE102012012518A1; GB201310880D0; ITMI20131024A1; FR2992329B1; GB2505048B

Abstract

A hot shaping die for the production of steel shaped parts comprises first and second die parts 2,3 which can be moved from a feed position to a shaping position. The working surfaces of the dies have surface portions having different roughnesses. The smoother surface portions provide more rapid cooling and so produce a pressed component zone 5 which is stronger, preferably martensitic. The lesser surface contact area of the rougher surface portions provides slower cooling and so softer more ductile pressed component zones 8, preferably bainitic. The rougher surface may be provided by a linear or punctiform structure or raised areas with a waffle, ribbed or honey-comb structure. The rougher surface may comprise linked channels opening to the edge of the rougher surface. A temperature sensor may be utilised for control of a pump supplying cooling medium to cooling channels of the die. The ductile zones may provide for post production processing such as stamping or drilling. May be used to produce parts requiring differing strengths such as those relating to the crash behaviour of a vehicle.

Description

I

Rot mhping di. for aanuf actur. of shaped iParts The invention concerns a hot shaping die for the manufacture of shaped parts, which have high-strength zones and ductile zones where the cooled hot shaping die consists of parts, in particular a die upper part and a die lower part that can be adjusted from a feed position to a shaping position, where the first working surfaces of the die parts, in particular the die upper part and/or the die lower part, that during the shaping process shape the high-strength zones of the shaped part, have smooth surfaces and are fully in contact with the contours of the part that has been, or will be shaped.

According to the current state of the art, it is possible to manufacture shaped parts with high-strength and ductile zones. Different procedures can be used for this. The EP I 470 81 describes an example manufacturing process for the B-pillar of a vehicle body structure that essentially has a high-strength structure, but a ductile structure in the base of the pillar. For this, the B-pillar is made from a blank or a preformed longitudinal profile, with zones of the blank or preformed longitudinal profile insulated whilst they are brought up to the austenitisation temperature in a furnace. In this way the insulated areas do not reach the austenitisation temperature and consequently do not convert to martensite during the subsequent cooling, producing a ductile zone with a bainitic and/or ferritic-pearlitic structure.

A further possibility is described in DE 102 56 621 83. In this, a shaped component, e.g. a blank or preformed sheet is heated in a tunnel furnace. A dividing wall in the tunnel furnace separates the tunnel furnace into two areas, each at a different temperatuxe. In this way, zones of the shaped component can be heated to different temperatures, and during the subsequent shaping and hardening process can be produced with a high-strength and ductile zone structure The dividing walls required for the different temperature zones can only be replaced at considerable expense.

Furthermore, IDE 197 43 802 C2 30 describes a process for the manufacture of a metallic shaped component, in which partial zones of a blank that must have greater strength than the rest of the component must be brought to a temperature of between 600°C and 900°C in less than 30 seconds. Subsequently the blank is shaped and annealed in a press die.

A second process is described in the publication, in which the blank is first pre-shaped or finally shaped and then partial zones are heat-treated in the manner described above.

The heat treated zones then have greater strength compared to the rest of the component.

This publication also recommends heating the blank completely to 900°C -950°C, shaping it in a press die and then annealing. Subsequently partial zones should be heated, to produce the required ductility in these zones.

The processes described are relatively time-consuming and costly. They require several work steps to produce the required shaped component, which generally results in extended cycle times. In order to bring zones of the components to the required temperatures before the shaping process, or to heat them after the shaping process and thus achieve the desired effect, requires the increased consumption of energy that can lead to increased production costs. In addition these processes can lead to thermal distortion of the shaped component. Heating to different temperatures before the shaping process can produce transition zones, having art adverse effect on the desired result, with the possibility of no clear demarcation between high-strength and low-strength zones.

According to the the current state-of-the art, the basic task of the invention is to create a hot shaping die for the production of steel shaped parts with high-strength and ductile zones, which, having moderate energy consumption and a high cycle rate, is suitable for the production of shaped parts with several different strength zones and thus enables limited transition boundaries between the zones and avoids thermal distortion, To solve this problem, it is proposed that second working surfaces of the hot shaping die, which produce the ductile zone of the shaped part during the shaping process, have a rough surface, different from a smooth texture. In this way the shaped part can be moulded to its intended contours, but the contact cooling involved is slowed down so that the formation of martensite is almost completely prevented.

The outcome is a hot shaping die that is suitable for the manufacture of shaped parts, such as body structure components, with differing strength zones. In the process, a send-finished product, such as a blank that is heated to austenitisation temperature, is placed in the hot shaping die and moulded into a shaped part and hardened. During the shaping and hardening process, the differing strengths are produced. According to the invention, this is accomplished in a single work step by the hot shaping die having differing working surfaces. The first working surface, which shapes the high-strength zone of the shaped part, should have a smooth surface and be fully in contact with the contours of the part that has been, or will be shaped.

Through contact between the hot shaping die and the shaped part, the heat of the shaped part is drawn into the cooled hot shaping die, where the hot shaping die is completely cooled to achieve the heat dissipation. As a result of the rapid cooling in this zone of the shaped part, which is in contact with the first working surfaces, a high-strength, martensitic structure is achieved.

Some areas of the hot shaping die have a second working surface that differs from the first working surface described. These have a different surface structure, where the rough structure is not fully in contact with the contours of the shaped part, thus achieving a slower rate of cooling as a result of the slower heat dissipation and a consequently ductile structure. For example, the rate of cooling can be around 15 to 20 K/s.

The ductile structure can also be introduced into areas of the parts that are to be processed after production, e.g. by driflings or stamping. In addition, the zones of shaped parts that are relevant to the crash behaviour of a vehicle can be optirnised by the introduction of differing strengths.

Preferably, it is envisaged that the second working surfaces, that shape the ductile zones of the shaped part have a linear or punctifo.nn surface structure, where this structure is preferably made up of a pattern of raised areas with a waffle, honey-comb or ribbed structure and the structure edges that touch the shaped part lie closely together.

As a result of the surface structure according to the invention, the contact points between the second working surface and the shaped part are reduced to enable controlled slower heat dissipation. For this, the structure edges can touch the shaped part in either a liner or punctifonu manner so that along with the reduced heat dissipation, dimensional stability is guaranteed and thermal distortion is prevented. As a result of the waffle, honey-comb or ribbed structure, between the contact edges there are surfaces that create the spaces necessary for the delay in heat transfer.

The structure edges lie close together to mould the shaped part into the desired shape.

From the configuration of the second working surfaces, in the corresponding areas it is possible to achieve hardening in the ductile areas, which can be between 150 HV and 400 HV.

Preferably, it is envisaged that the recessed structure surfaces opposite the protruding structure edges form channels with the structure edges, which are linked to each other.

The structure surfaces are formed between the structure edges in contact with the shaped part. These form contact edges and spaces, so that the cooling effect of the hot shaping die is diminished and hence there is slower heat dissipation from the shaped part to the hot shaping die. Each surface structure leads into another surface structure, so that a type of channel system is formed that links the spaces to each other.

Preferably it is envisaged that the channels open onto the edge of the working surfaces.

The openings on the edge of the working surface ensure that there is no accumulation of heat, but rather the heat can escape to the surroundings, e.g. by air flow. This prevents a build-up of heat in the hot shaping die that could potentially damage it.

Preferably it is envisaged that the die parts have cooling channels that open onto the second working surfaces, to which cooling medium supply lines are connected.

If required, after initial slow cooling, a cooling medium, e.g. air, can be fed via the cooling channels into channels of the second working surface structure, thereby enabling a more rapid cooling of the shaped part. For this, both the cooling medium as well as the time the cooling medium is applied can vary, enabling differing hardnesses to be introduced.

After an initial slow cooling phase, which ensures that a bainitic or even ferritic-pearlitic structure forms, by forcing the cooling medium into the structure channels, the shaped part in the area of the second working surfaces is rapidly cooled to a temperature that is preferably between 150°C and 180°C, before the hot shaping die is opened and the shaped part can be removed from the hot shaping die. This prevents thermal distortion in the shaped part and reduces the cycle time.

Preferably it is envisaged that the components of the hot shaping die that have the second working surfaces are attached either permanently or temporarily to the hot shaping die.

Of advantage here could be that the second working surfaces are produced initially with the structure according to the invention and only then assembled into the hot shaping die. This could simplify the production process for the manufacture of the hot shaping die.

In addition, damaged second working surfaces could be easily replaced and/or repaired.

Furthermore, the removable second working surfaces could be assembled into different hot shaping dies, possibly for use with different component geometries.

Preferably it is also envisaged that a temperature sensor is provided to determine the temperature of the area of the second working surfaces or the shaped part that is present there. Preferably, this should be linked to a control unit for a cooling medium pump, by means of which, if a desired temperature is not reached, supply of cooling material to the cooling channels takes place.

The temperature sensor connected to the control unit ensures that after an initial slow cooling to a temperature, preferably below 500°C, a cooling medium is fed into the working surface structure via the cooling medium pump to speed up the remaining cooling.

An example of a hot shaping die variant in accordance with the invention is shown in the drawings and described in more detail below.

It shows: Fig. 1 A side view of the hot shaping die; Fig. 2 A side view of the hot shaping die rotated through 90°, partially sectioned; Fig. 3 A possible variant in accordance with the invention of the surface structure of the second working surface; Fig. 4 Graphs of the structure changes dependent upon time and temperature.

Figs, 1 and 2 show a side view of the hot shaping die. The cooled hot shaping die 1. consisting of a combination of die parts that can be adjusted from a feed position to a shaping position, in particular of a die upper part 2 and a die lower part 3, where the first working surfaces of the die parts, in particular of the die upper part 2 and/or the die lower part 3, that during the shaping process shape the high-strength zones 5 of the shaped part 6, which are of smooth construction and is fully in contact with the contour of the shaped part 6 that has been, or will be shaped. In addition, the hot shaping die 1 has second working surfaces 7, which during the shaping process produce the ductile zone 8 of the shaped part 6 and have a rough surface 9, different from a smooth texture. In this way the shaped part 6 can be given its intended contours, but the contact cooling involved is si.owed down so that the formation of martensite is almost completely prevented. The die parts have cooling drillings 16, so that during shaping, the hot shaping die 1, and consequently the shaped part 6 is cooled and hardened. The die parts also have cooling channels 14 that open onto the working surfaces 7, to which cooling medium supply lines 15 are connected. f temperature sensor is envisaged to determine the temperature of the shaped part 6 in the area of the second working surfaces 7. Preferably, this should be linked to a control unit for a cooling medium pump, by means of which, if a desired temperature is not reached, supply of cooling material to the cooling channels 14 takes place.

Fig. 3 shows a possible structure of the second working surfaces 7 that shape the ductile zone 8 of the shaped part 6. The second working surfaces 7 have a linear and/or punctiform surface structure, where this structure is preferably made up of a pattern of raised areas with a waffle, honey-comb or ribbed structure and the structure edges 10 that touch the shaped part 6 lie closely together.

The recessed structure surfaces 11 opposite the protruding structure edges 10 form channels 12 with the structure edges 10, which are l:Lnked to each other.

The channels 12 open onto the edge 13 of the second working surfaces 7, so that the cooling medium, in particular air or also a gas, that is fed through the cooling channels 14 can flow out.

Fig. 4 shows the structure development in the different areas of the shaped part. In the area of the second working surfaces 7 the shaped part 6 is cooled from a temperature At,,, that corresponds to the austenitisation temperature, according to the dotted line 17, so that a ductile structure, in particular a bainitic structure results. When a temperature of approx. 400°C is reached, the second working surfaces 7 and the shaped part 6 in the area of the second working surfaces 7 are rapidly reduced to a removal tenlperattare, e.g. 200°C by air cooling.

In the area of the first working surfaces 4, the cooling of the hot shaping die 1 is fully effective, so that the shaped part 6 in this area is cooled very rapidly from A,3 to below 400ac as per the solid line 18. This enables a martensitic structure to be achieved that forms the high-strength zone 5 of the shaped part 6, The heating of the shaped part 6 to Aa temperature can be done in a tunnel furnace.

The invention is not limited to the variant given as the example, but is infinitely variable within the scope of the

disclosure.

The invention resides in all novel and inventive features or combinations of features disclosed by the description and/or drawings. Osims

Claims

l A shaping die for the production of steel shaped parts, wherein the shaping die comprises a combination of die parts adjustable from a feed position to a shaping position, the combination of die parts comprising a die upper part and a die lower part; wherein the die upper part and/or die lower part comprise first and second working surfaces having different surface roughnesses.
2. A method of using a shaping die for the production of steel shaped parts, which have one or more first zones and one or more second zones, the one or more first zones to have higher strength than the one or more second zones; wherein the shaping die comprises a combination of die parts adjustable from a feed position to a shaping position, the combination of die parts comprising a die upper part and a die lower part, wherein the die upper part and/or of the die lower part comprise one or more first working surfaces that shape the one or more first zones of the shaped part during the shaping process, and one or more second working surfaces which shape the one or more second zones of the shaped part during the shaping process, wherein the one or more second working surfaces have a rougher texture than the one or more second working surfaces, which rougher texture functions to slow contact cooling of the one or more second zones.
3. Hot shaping die for the production of steel shaped parts, which have high-strength zones and ductile zones where the cooled hot shaping die has a combination of die parts that can be adjusted from a feed position to a shaping position, in particular a die upper part and a die lower part, where the first working surfaces of the die parts, in particular of the die upper part and/or of the die lower part that shape the high-strength zones of the shaped part during the shaping process, are of smooth construction and fully in contact with the part that has been or will be shaped, characterised in that second working surfaces of the hot shaping die, which shape the ductile zone of the shaped part during the shaping process, have a rough surface that is different from a smooth texture, so that the shaped part can be given its intended contours, but the contact cooling is slowed down so that the formation of martensite is almost completely prevented.
4. A shaping die or method according to any preceding claim, wherein the second working surfaces have a linear and/or punctiform surface structure.
5. A shaping die or method according to any preceding claim, wherein the surface structure of the second working surfaces, comprises a pattern of raised areas with a waffle, honey-comb or ribbed structure.
6. A shaping die or method according to any preceding claim, wherein the second working surfaces comprises structure edges that are adjacent to each other.
7. A shaping die or method according to any preceding claim, wherein the second working surfaces comprise recessed structure surfaces opposite protruding structure edges forming channels with the structure edges, which are linked to each other.
8. A hot shaping die or method according to Claim 7, wherein the channels open to the edge of the second working surfaces.
9. A shaping die or method according to any preceding cl.aim, wherein the die parts having cooling channels that open onto the second working surfaces, to which cooling medium supply lines are attached.
10. A shaping die or method according to any preceding claim, wherein components of the shaping die comprising the second working surfaces are attached either permanently or temporarily to the shaping die
II. A shaping die or method according to any preceding claim, wherein a temperature sensor is provided to determine the temperature of the second working surface or a shaped part that is present there.
12. A shaping die or method according to any preceding claim, wherein a temperature sensor is connected to a control unit for a cooling medium pump by means of which, if a desired temperature is not reached, the supply of cooling medium to cooling channels takes place.
13. A shaping die or method substantially as described herein with reference to any one or more of Figures 3. to 3 of the accompanying drawings.