Method and device for the heat treatment of a metal component

Abstract

Disclosed are implementations for heat treatment of a metal component, and a use of a furnace for heating a metal component. The implementations can be used in the partial hardening of optionally pre-coated components made of a high-strength manganese-boron steel. An example method for heat treatment of a metal component comprises at least the following steps: a) heating the component in a first furnace; b) moving the component into a temperature control station; c) cooling at least one first sub-region of the component in the temperature control station, wherein a temperature difference is set between the at least one first sub-region and at least one second sub-region of the component; d) moving the component from the temperature control station into a second furnace; and e) heating at least the at least one first sub-region of the component in the second furnace by at least 200 K.

Claims

1. A method for heat treating a metal component, comprising at least the following steps: a) heating the component in a first furnace; b) moving the component into a temperature control station; c) cooling at least one first sub-region of the component in the temperature control station, wherein a temperature difference is set between the at least one first sub-region and at least one second sub-region of the component; d) moving the component from the temperature control station into a second furnace; and e) heating at least the at least one first sub-region of the component in the second furnace by at least 200 K.

2. The method according to claim 1, further comprising at least the following steps: f) moving the component from the second furnace into a press hardening tool; and g) forming and cooling the component in the press hardening tool.

3. The method according to claim 1, wherein the component is heated in step a) to a temperature below the Ac3 temperature.

4. The method according to claim 1, wherein the component is heated in step a) to a temperature above the Ac3 temperature.

5. The method according to claim 1, wherein the at least one first sub-region is cooled in step c) by way of convection to a temperature below the Ac1 temperature.

6. A method for heat treating a metal component, comprising at least the following steps: a) heating the component by way of radiant heat and/or convection by at least 500 K; b) cooling at least one first sub-region of the component, wherein a temperature difference of at least 100 K is set between the at least one first sub-region and at least one second sub-region of the component (1); and c) heating at least the at least one first sub-region of the component by way of radiant heat and/or convection by at least 100 K.

7. The method according to claim 6, wherein the component is simultaneously formed and cooled in step d).

8. The method of claim 1, further comprising using a furnace for heating at least sub-regions of the metal component, comprising the first and second sub-regions that have been controlled to differing temperatures, by way of radiant heat by at least 100 K.

Description

(1) The invention and the technical environment will be described in more detail hereafter based on the figures. It should be noted that the invention shall not be limited by the shown exemplary embodiments. In particular, it is also possible, unless explicitly described otherwise, to extract partial aspects of the subject matter described in the figures, and to combine these with other components and/or findings from other figures and/or the present description. In the schematic drawings:

(2) FIG. 1 shows a diagram of a device according to the invention;

(3) FIG. 2 shows a detailed view of a temperature control station usable in a device according to the invention;

(4) FIG. 3 shows a time-temperature curve achievable by means of a device according to the invention and/or a method according to the invention; and

(5) FIG. 4 shows a time-temperature curve achievable by means of a further device according to the invention and/or a method according to the invention.

(6) FIG. 1 schematically shows a device 8 according to the invention for heat treating a metal component 1, comprising a first furnace 2, a temperature control station 3, a second furnace 6, and a press hardening tool 7. The device 8 represents a hot forming line for press hardening here. The temperature control station 3 is located (directly) downstream of the first furnace 6, so that a component 1 to be treated by means of the device 8 can be transferred directly into the temperature control station 3 upon leaving the first furnace 6. Furthermore, the second furnace 6 of the temperature control station 3 and the press hardening tool 7 are located (directly) downstream of the second furnace 6.

(7) FIG. 2 schematically shows a detailed view of a temperature control station 3, which can be used in a device 8 according to the invention, such as is shown in FIG. 1, for example. A nozzle 9, which is provided and configured for discharging a fluid 10 for cooling a first sub-region 4 of a component 1, is disposed in the temperature control station 3. Moreover, a heating unit 11, which is provided and configured for inputting thermal energy into a second sub-region 5 of the component 1, is disposed in the temperature control station 3. For this purpose, the heating unit 11 is designed as an electrically operated heating wire, for example.

(8) FIG. 3 schematically shows a time-temperature curve achievable by means of a device 8 according to the invention and/or a method according to the invention. The temperature T of the metal component is, or the temperatures T of the at least one first sub-region and of the at least one second sub-region of the component are, plotted against the time t.

(9) According to the time-temperature curve shown in FIG. 3, the metal component 1 is first uniformly heated to a temperature below the Ac1 temperature up until the point in time t.sub.1. By way of example, this heating takes place in a first furnace 2 here. Between the points in time t.sub.1 and t.sub.2, the metal component is transferred from the first furnace into a temperature control station. The component temperature may decrease slightly during this process, for example due to heat emission to the surrounding area.

(10) Between the points in time t.sub.2 and t.sub.3, at least one first sub-region of the component is (actively) cooled in the temperature control station. This is illustrated in FIG. 3 based on the bottom time-temperature curve between the points in time t.sub.2 and t.sub.3. At the same time, at least one second sub-region of the component is (slightly) heated in the temperature control station. This is illustrated in FIG. 3 based on the top time-temperature curve between the points in time t.sub.2 and t.sub.3. In this way, a temperature difference 12 is set in the temperature control station between the at least one first sub-region and at least one second sub-region of the component.

(11) Between the points in time t.sub.3 and t.sub.4, the component is transferred from the temperature control station into a second furnace different from the first furnace. The partially differing temperatures set in the temperature control station may decrease slightly during this process, for example due to heat emission to the surrounding area.

(12) The component is heated in the second furnace from the point in time t.sub.4 to the point in time t.sub.5 in such a way that the temperature of the at least one first sub-region of the component is increased by at least 150 K. Furthermore, the heating in the second furnace takes place in such a way that, at the same time, the temperature of the at least one second sub-region of the component is brought to a temperature above the Ac3 temperature.

(13) Between the points in time t.sub.5 and t.sub.6, the component is transferred from the second furnace into a press hardening tool. The partially differing temperatures set in the second furnace may decrease slightly during this process, for example due to heat emission to the surrounding area.

(14) From the point in time t.sub.6 until the end of the process, the (entire) component is quenched in the press hardening tool. It is possible for a martensitic microstructure to be produced at least partially or even predominantly in the at least one second sub-region of the component, which has comparatively high strength and comparatively low ductility. Essentially no transformation has taken place in the at least one first sub-region of the component since the at least one first sub-region of the component has not exceeded the Ac1 temperature at any point during the process, so that a predominantly ferritic microstructure remains in the at least one first sub-region of the component, which has comparatively low strength and comparatively high ductility.

(15) FIG. 4 schematically shows a further time-temperature curve achievable by means of a device according to the invention and/or a method according to the invention. Initially, the metal component is uniformly heated to a temperature above the Ac3 temperature up until the point in time t.sub.1.

(16) By way of example, this heating takes place in a first furnace here. Between the points in time t.sub.1 and t.sub.2, the metal component is transferred from the first furnace into a temperature control station. The component temperature may decrease slightly during this process.

(17) Between the points in time t.sub.2 and t.sub.3, at least one first sub-region of the component is (actively) cooled in the temperature control station. This is illustrated in FIG. 4 based on the bottom time-temperature curve between the points in time t.sub.2 and t.sub.3. At the same time, the temperature of at least one second sub-region of the component may decrease slightly in the temperature control station. This is illustrated in FIG. 4 based on the top time-temperature curve between the points in time t.sub.2 and t.sub.3. This (passive) decrease in temperature in the at least one second sub-region of the component has a considerably lesser cooling rate than the simultaneous (active) cooling of the at least one first sub-region of the component. It is apparent from FIG. 4 that a temperature difference 12 is set between the at least one first sub-region and at least one second sub-region of the component in the temperature control station.

(18) Between the points in time t.sub.3 and t.sub.4, the component is transferred from the temperature control station into a second furnace different from the first furnace. The partially differing temperatures set in the temperature control station may decrease slightly during this process.

(19) The component is heated in the second furnace from the point in time t.sub.4 to the point in time t.sub.5 in such a way that the temperature of the at least one first sub-region of the component is increased by at least 150 K. Moreover, the heating in the second furnace takes place in such a way that, at the same time, a cooling rate of the at least one second sub-region of the component is reduced compared to a cooling rate during heat emission to the surrounding area.

(20) Between the points in time t.sub.5 and t.sub.6, the component is transferred from the second furnace into a press hardening tool. The partially differing temperatures set in the second furnace may decrease slightly during this process, for example due to heat emission to the surrounding area.

(21) From the point in time t.sub.6 until the end of the process, the (entire) component is quenched in the press hardening tool. It is possible for a martensitic microstructure to be produced at least partially or even predominantly in the at least one second sub-region of the component, which has comparatively high strength and comparatively low ductility. It is possible for a bainitic microstructure to be produced at least partially or even predominantly in the at least one first sub-region of the component, which has comparatively low strength and comparatively high ductility.

LIST OF REFERENCE NUMERALS

(22) 1 component 2 first furnace 3 temperature control station 4 first sub-region 5 second sub-region 6 second furnace 7 press hardening tool 8 device 9 nozzle 10 fluid 11 heating station 12 temperature difference