Post-treating a hardened metal formed part

Abstract

A formed and hardened component made from a metallic material is post-treated by a device for electric resistance heating that has at least one first pair of contact pieces and at least one second pair of contact pieces; contacting a first partial region of the component with the contact pieces of the first pair such that the first partial region is arranged between the contact pieces of the first pair; contacting the second partial region of the component with the contact pieces of the second pair such that the second partial region is arranged between the contact pieces of the second pair; heating of the first partial region of the component to a first temperature by conducting electric current through the component by the first pair of contact pieces; setting the second partial region of the component to a second temperature by the second pair of contact pieces, which is set independently of the first temperature.

Claims

1. A method for post-treating a formed and hardened component made of a metallic material by a device for electric resistance heating, the device having at least one first pair of contact pieces and at least one second pair of contact pieces, the method comprising: contacting the contact pieces of the first pair with a to be heated first partial region of the component such that the to be heated first partial region is arranged between the first pair of contact pieces in a thickness direction of the component; contacting the contact pieces of the second pair with a second partial region of the component such that the second partial region is arranged between the second pair of contact pieces in the thickness direction of the component; heating the first partial region of the component to a first temperature (T1) by conducting electric current through the component using the first pair of contact pieces, wherein the first partial region is heated to the first temperature (T1) of at most of 900 C., and setting the second partial region of the component to a second temperature (T2) using the second pair of contact pieces, wherein the second temperature (T2) is set independently of the first temperature (T1), so that the first partial region obtains a higher ductility than the second partial region; wherein the formed and hardened component is produced by: flexible rolling of a strip material; cutting a blank from the strip material, wherein the blank has a varying thickness across the length; and hot-forming and hardening the blank.

2. The method of claim 1, wherein the step of heating the first partial region of the component further comprises at least one of the following: the first partial region is heated to the first temperature (T1) of at least 500 C.; and the first partial region is heated for a period of at least 30 seconds.

3. The method of claim 1, wherein the step of contacting comprises at least one of the following: that an upper contact piece of the first pair and an upper contact piece of the second pair are brought into contact with the component at a same time, that a lower contact piece of the first pair and a lower contact piece of the second pair are brought into contact with the component at a same time.

4. The method of claim 1, wherein the first pair of contact pieces and the second pair of contact pieces are configured to be individually controlled with respect to at least one parameter influencing the degree of heating.

5. The method of claim 1, wherein the step of setting the second partial region of the component to the second temperature (T2) is a heating process that is achieved by conducting electric current from one of the second pair of contact pieces through the component to another one of the second pair of contact pieces.

6. The method of claim 5, wherein heating the first partial region and the second partial region of the component comprises at least one of the following: conducting electric current between the first pair of contact pieces and the second pair of contact pieces through the component with a timely offset, conducting electric current between the first pair of contact pieces and the second pair of contact pieces through the component with at least a partial timely overlap, and conducting electric current between the first pair of contact pieces and the second pair of contact pieces through the component with different electric currents.

7. The method of claim 1, wherein the step of setting the second partial region of the component to a second temperature (T2) is a cooling process that is achieved by cooling the contact pieces of the second pair.

8. The method of claim 1, wherein the first pair of contact pieces and the second pair of contact pieces are arranged directly next to each other and are brought into contact with the component directly next to each other.

9. The method of claim 1, further comprising at least one of the following steps before the post-treating: cleaning of the component; and scaling the component.

10. The method of claim 1, wherein at least one of the contact pieces of the first pair of contact pieces are arranged such that the to be heated first partial region of the component is arranged between the contact pieces of the first pair of contact pieces in a thickness direction of the component, and the contact pieces of the second pair of contact pieces are arranged such that the second partial region of the component is arranged between the contact pieces of the second pair of contact pieces in a thickness direction of the component.

11. A method for producing a component made of a metallic material, comprising: providing a blank made of metallic material; forming and hardening the blank so as to obtain a formed and hardened component that has a greater hardness than the blank; and post-treating the formed and hardened component by a device for electric resistance heating that has at least one first pair of contact pieces and at least one second pair of contact pieces, the post-treating comprising: contacting the contact pieces of the first pair with a to be heated first partial region of the component such that the to be heated first partial region is arranged between the first pair of contact pieces in a thickness direction of the component; contacting the contact pieces of the second pair with a second partial region of the component such that the second partial region is arranged between the second pair of contact pieces in the thickness direction of the component; and heating the first partial region of the component to a first temperature (T1) by conducting electric current through the component by the first pair of contact pieces, and setting the second partial region of the component to a second temperature (T2) by the second pair of contact pieces, wherein the second temperature (T2) is set independently of the first temperature (T1) such that the first partial region of the component obtains a higher ductility than the second partial region.

Description

(1) Example embodiments are described in the following using the drawings, which show:

(2) FIG. 1; a formed and hardened metal component for post-treating partial regions in a top view,

(3) FIG. 2; a device in a first embodiment for post-treating the component of FIG. 1, in cross-section,

(4) FIG. 3; a formed and hardened metal component for post-treating partial regions in a top view,

(5) FIG. 4: a device in a second embodiment for post-treating the component of FIG. 3, schematically in a perspective view,

(6) FIG. 5: a formed and hardened metal component for post-treating partial regions in a top view,

(7) FIG. 6: a device in a further embodiment for post-treating the component of FIG. 5, in a cross-section,

(8) FIG. 7: a device for post-treating partial regions of a formed and hardened component in a further embodiment in a top view,

(9) FIG. 8: the device of FIG. 7 in a cross-sectional view through a first pair of contact pieces,

(10) FIG. 9: the device of FIG. 7 in a cross-sectional view through a second pair of contact pieces, and

(11) FIG. 10: the component of FIG. 7 with post-treated partial regions in a top view.

(12) FIGS. 1 and 2, which are described jointly below, show a device 2 for post-treating a formed and hardened component 3, which is manufactured from a metallic material, in a first embodiment.

(13) The device 2 comprises a first pair of contact pieces 4, 5 that are configured as form electrodes for transmitting an electric current through a first partial region 6 of the component 3. The contact faces 7, 8 of the contact pieces 4, 5, which can also be referred to as function faces, are adapted to outer faces 9, 10 of the first partial region 6. This means that the geometry of the contact faces 7, 8 is formed corresponding to the geometry of the first partial region 6, wherein especially also different sheet thicknesses of the component can be considered by shaping of the contact pieces accordingly. The form electrodes 4, 5 are brought into surface contact with the component 3, which is clamped between an upper and a lower form electrode 4, 5. By closing the electric circuit between the two form electrodes 4, 5 an electric current is passed through the first partial region 6, so that this partial region 6 is heated to a first temperature T1 because of the electric resistance. The first partial region 6 is shown hatched in FIG. 1. In a top view, the contact pieces 4, 5 have a contact face that is formed correspondingly to the outline of the first area 6.

(14) A special feature of the present embodiment is that the component 3 is arranged between the two contact pieces 4, 5 in a thickness direction thereof. A lower contact piece 5 is brought into contact with the lower side of the component 3, while an upper contact piece 4 is brought into contact with the upper side of the component. Thus, the component 3 is held or clamped between the contact pieces 4, 5. An unwished distortion because of heating the component can thus be prevented. The contact faces 7, 8 of the contact pieces 4, 5 of the first pair are preferably smaller than 400 mm.sup.2 for a good current introduction, wherein in principle also larger faces are possible. In the present embodiment the electric current flows substantially vertically relative to the contact faces 7, 8, i.e., substantially in a thickness direction of the component 3. Thus, a quick heating is achieved.

(15) Preferably, the first partial region 6 is heated to a first temperature T1, which is at least 500 C., preferably at least 700 C. The upper limit for the first temperature T1 can be, for example, 900 C. The higher the temperature T1 is selected for heating the first partial region 6, the shorter the exposure time can be selected at which the component has to be heated to achieve the required softening. Preferably, the first partial region 6 is heated for a period of at least 30 seconds, thus reducing the production of unwished hardening distortions. Concerning the relation between heating temperatures and respective heating exposure times for softening the first partial region, the following embodiments can be used, not being limited thereto: at up to 700 C. heating temperature at least 5 minutes exposure time, at up to 750 C. at least 2.5 minutes exposure time, at up to 800 C. at least 1.25 minutes exposure time and at above 850 C. at least 30 seconds exposure time.

(16) The device 2 further comprises a second pair of contact pieces 44, 45 for setting a second partial region 46 of the component 3 to a second temperature T2. Also for the second pair it applies that the contact faces 17, 18 of the contact pieces 44, 45 are correspondingly adapted to the outer faces 19, 20 of the second partial region 46. The contact pieces 44, 45 of the second pair are presently formed as cooling contact pieces, with which the second partial region 46 is adjustable to a temperature T2 below the temperature T1. For this, the cooling contact pieces 44, 45 have a temperature setting mechanism that can comprise integrated cooling circuits 22, 23 (represented in a dashed line), through which a cooling medium, like water or steam, can be passed. By this design, i.e., providing cooling contact pieces 44, 45, it is achieved that the heat introduced into the component 3 by the electrodes 4, 5 remains spatially limited to the first partial region 6 and leads to a softening only there, while the second partial region 46 keeps its initial strength because of the cooling. For cooling, the contact pieces 44, 45 of the second pair can be adjusted to a temperature T2 of below 300 C., in particular to below 200 C. or even less than 100 C.

(17) The contact pieces of the first pair 4, 5, respectively of the second pair 44, 45 are made from high-strength, temperature resistant material. Concerning the shape and the size they are adapted, as described above, to the to be heated or cooled partial regions of the component. By arranging the first contact pieces 4, 5 for heating and second contact pieces 44, 45 for cooling adjacent to each other, a short transition region is achieved in an advantageous manner between the softened first partial region 6 and the untreated second partial region 46. The contact pieces 4, 5, loaded with electric current, can be cooled for increasing the durability.

(18) The device can be provided in two part form and can comprise a lower tool part, in which respectively a first contact piece 5, 45 of the first and the second pair are arranged, as well as an upper tool part, in which respectively the corresponding second contact piece 4, 44 of the first and the second pair are arranged. By moving the upper tool part in direction towards the lower tool part or vice versa, the component 3 is clamped between the lower and upper contact pieces 5, 45; 4, 44. For moving the tool part, a suitable mechanism can be provided.

(19) FIGS. 3 and 4, which are jointly described below, show a device according to the invention in a second embodiment. This largely corresponds concerning its design and function to that according to FIGS. 1 and 2, so that concerning the commonalities reference is made to the above description. In this case, the same or one another corresponding details are provided with the same reference numeral as in FIGS. 1 and 2.

(20) A special feature of the present embodiment according to FIGS. 3 and 4 is, that four pairs of contact pieces are provided, wherein it will be understood that also a different number of two, three, five or more pairs can be used. The contact pieces of each pair 4, 5; 14, 15; 24, 25; 34, 35 are configured as form electrodes, with which electric current can be transmitted through the component 3. In this case, a first partial region 6 is heated by the first pair 4, 5, a second partial region 16 is heated by the second pair 14, 15, a third partial region 26 is heated by the third pair 24, 25 and a fourth partial region 36 is heated by the fourth pair 34, 35.

(21) The pairs of contact pieces can be controlled individually with respect to one or more parameters influencing the degree of heating, for example, concerning the amperage or the exposure time. In this manner, the different partial regions 6, 16, 26, 36 can be individually heated. In this case, it is especially possible to consider sheet thickness differences of the partial regions such that overall a targeted heating and thus also a defined softening is achieved.

(22) The first pair of electrodes 4, 5 can be heated to a first temperature T1, while the second pair of electrodes 14, 15 can be heated up to a second temperature T2, deviating therefrom. Also the third and the fourth pair of electrodes 24, 25; 34, 35 can be individually controlled concerning the required temperature, and can be adjusted to one of the temperatures T1 or T2 or to temperatures deviating therefrom.

(23) Incidentally, all features that have been described in connection with the embodiment of FIGS. 1 and 2 for the first pair are likewise valid for each of the four pairs of the present embodiment according to FIGS. 3 and 4. With respect to these features reference is made to the above description.

(24) FIGS. 5 and 6, which are jointly described together below, show a device according to the invention in a third embodiment. This corresponds concerning its design and function to a combination of the embodiments of FIGS. 1 and 2 with that according to FIGS. 3 and 4, so that concerning the commonalities reference is made to the above description. In this case, the same or one another corresponding details are provided with the same reference numerals as in FIGS. 1 to 4.

(25) A special feature of the present embodiment according to FIGS. 5 and 6 is that it has four pairs of contact pieces 4, 5; 14, 15; 24, 25; 34, 35, configured as electrodes for heating, respectively softening the partial regions 6, 16, 26, 36. What has been described in connection with the description of FIGS. 3 and 4 is likewise valid. Additionally, a pair of contact pieces 44, 45 is provided, which are configured as cooling contact pieces, i.e., corresponding to the cooling contact pieces 44, 45 of FIGS. 1 and 2. In so far as the features concerning the cooling contact pieces in the embodiment according to FIGS. 1 and 2, are likewise present in the embodiment according to FIGS. 5 and 6, reference is made to the above description.

(26) An advantage of the present embodiment is, that between the heated, respectively softened partial regions 6, 16, 26, 36 and the cooled partial region 46 only a small transition area is formed. This is achieved in such a way, that the electrodes 4, 5; 14, 15; 24, 25; 35, 36 and the cooling contact pieces 44, 45 are spatially adjoining each other.

(27) FIGS. 7 to 10, which are described jointly below, show a device according to a further embodiment. This largely corresponds in its design and function to that of FIGS. 1 and 2, so that concerning the commonalities reference is made the above description. In this case, the same or corresponding features are provided with the same reference numerals as in FIGS. 1 and 2.

(28) A special feature of the present embodiment is that the contact pieces 4, 5 of the first pair are arranged in a transversal direction of the component 3 opposite to each other, i.e., only in the edge portions of the component 3. A current flowing between the negative form electrodes 4, 4 and the positive form electrodes 5, 5 heats the component 3 across its width between the negative and positive form electrodes. As a whole, a softened first partial region 6, shown in FIG. 10 and represented hatched, is achieved.

(29) Adjacent to the contact pieces 4, 4; 5, 5 of the first pair, second pairs of contact pieces 44, 45; 54, 55 are arranged, one of which (44, 45) is shown in a cross-sectional view in FIG. 9. The contact pieces of the second pairs are respectively formed as cooling contact pieces. The cooling contact pieces 44, 45; 54, 55 are shown schematically in FIG. 7. The cooling zones 46, 56, which are produced by the cooling contact pieces 44, 45; 54, 55, are shown schematically in FIG. 10. Between the cooling zones 46, 56, the soft zone 6, extending in transversal direction of the component 3, is arranged, which is also referred to as softened partial region.

(30) In FIG. 9 it can be seen that the second pairs have, respectively, a lower contact piece 45 and an upper contact piece 44, which concerning their shape are adapted to the respective geometry of the component 3. The second pairs of contact pieces 44, 45; 54, 55 correspond concerning design and function to the embodiment shown in FIGS. 1 and 2, so that for abbreviation it is referred to the above description. The second pairs are arranged directly neighbouring the first pair during the post-processing, so that the configuration shown in FIG. 10 is achieved with the cooling zones 46, 56 and the soft zone 6 of the component 3 arranged therebetween. Between the cooling zones 46, 56 and the soft zone 6, only a small transition area is formed.

(31) The component 3, which is the lower part of a B-column for a motor vehicle, can have a constant sheet thickness across the length and width, or can have a varying sheet thickness across the length and/or width. This can, for example, be achieved by means of flexible rolling of the strip material used as starting material. For a constant heating and constant softening, respectively, it is advantageous when the first pair of contact pieces 4, 4, 5, 5 is arranged in an area of constant sheet thickness. This would be, in the present embodiment, the partial region 6.

(32) A method according to the invention for post-treating a formed and hardened component made of a metallic material can comprise the following steps.

(33) In a first method step, a to be heated first partial region of the hardened component is brought into contact with the contact pieces of the first pair. At the same time or subsequent thereto the contact pieces of a second pair are brought into contact with a second partial region of the component. Subsequently, the first partial region of the component is heated to a first temperature T1 such that electric current is transmitted through the component by the first pair of contact pieces. Preferably, the first partial region is heated to a first temperature of at least 500 C., especially at least 700 C., at a preferred heating time of at least 30 seconds.

(34) During the heating of the first partial region, a second partial region, which is especially arranged adjacent the first partial region, is set to a second temperature T2 by means of one or more second pairs of contact pieces, i.e., heated or cooled. In this case, the temperature setting of the second partial region of the component is carried out, at least with respect to one parameter influencing the temperature of the second region, independently of heating the first partial region. In an embodiment in which the second pair of contact pieces is formed as form electrodes for resistance heating, the temperature setting (heating) can be carried out by selecting a different current exposure time and/or other amperage, respectively electric current than in the first pair. In an embodiment in which the second pair of contact pieces is formed as cooling elements, the temperature setting (cooling) can be carried out by controlling the flow and/or the temperature of the cooling medium.

(35) The described method can be carried out with any one of the devices of electric resistance heating according to one of FIGS. 1 to 10, which have at least one first pair of contact pieces 4, 5 and a second pair of contact pieces 44, 45.

(36) The above described method for post-processing the hardened component for producing softened partial regions, respectively soft zones, can for example be preceded by the following method steps: flexible rolling of strip material, cutting a blank from the flexible rolled strip material, wherein the blank has a varying thickness across the length, hot-forming of a blank to a component, complete hardening of the component, cleaning the component and/or scaling of the component.

(37) An advantage of the device according to the invention and method is that the component 3, hardened beforehand, can be softened in a targeted manner in partial regions 6, 16, 26, 36, to achieve a higher ductility in said partial areas. By using several pairs of contact pieces, the ductility of the component can be adapted in different partial regions to the individual requirements, or the contact pieces themselves can be adapted to different requirements concerning the geometry of the component.