METHOD AND DEVICE FOR PRODUCING A PRESS-QUENCHED PART

Abstract

A method and device for producing a press-quenched part having a rim hole with a collar formed at the periphery of the rim hole includes inserting a temperature-controlled die into the rim hole of the part. The temperature of the temperature-controlled die is controlled such that the temperature of the part in a region of the collar is held above the martensite start temperature of the material from which the part is made. While the temperature of the collar is being held above the martensite start temperature, the remainder of the part is press quenched.

Claims

1.-8. (canceled)

9. A method for producing a press-quenched part having a rim hole with a collar formed at the periphery of the rim hole, the method comprising: providing a part to be press-quenched, having a rim hole with a collar formed at the periphery of the rim hole; inserting a temperature-controlled die into the rim hole of the part; controlling the temperature of the temperature-controlled die such that the temperature of the part in the region of the collar is held above the martensite start temperature of the material from which the part is made; press-quenching the part either during or after said inserting and controlling steps.

10. The method of claim 9, further comprising maintaining the insertion of the temperature-controlled die in the rim hole during the entire press quenching step.

11. The method of claim 9, further comprising cooling a remaining portion of the part, except for the collar, during the press quenching step.

12. The method of claim 9, wherein said press quenching step is performed by a press-quenching tool having a top tool with a first opening defined therein that is configured to permit the temperature-controlled die to extend there through in a form fitting manner.

13. The method of claim 12, wherein said press quenching step is performed by a press-quenching tool having a bottom tool with a second opening defined therein that is coaxial with the first opening defined in the top tool, and which second opening has a larger diameter than the first opening, the bottom tool configured to permit the temperature-controlled die to extend there through in a form fitting manner.

14. The method of claim 9, wherein a specific geometry of the rim hole and a height of the collar that is formed is determined by a geometry of the temperature-controlled die and the amount of extension of the temperature-controlled die into the rim hole, during said step of inserting the temperature-controlled die into the rim hole.

15. A device for producing a press-quenched part having a rim hole defined therein with a collar formed at a periphery of the rim hole, comprising: a press-quenching tool configured to press-quench the part; and a temperature-controlled die configured to be inserted into the rim hole defined in the press-quenched part, either prior to or during the press-quenching of the part by said press-quenching tool, and maintain a temperature in a region of the collar of the part above a martensite start temperature of the material from which the part is made.

16. The device of claim 15, wherein said press quenching tool comprises: a top tool having a first opening defined therein that is configured to permit said temperature-controlled die to be installed therein in an extendable and form fitting manner; and a bottom tool having a second opening defined therein that is configured to permit said temperature-controlled die to extend from said first opening in said top tool into said second opening in a form fitting manner.

Description

BRIEF DESCRIPTION OF THE FIGURE

[0020] FIG. 1 shows a diagram of a device for press-quenching a part

EMBODIMENTS OF THE INVENTION

[0021] FIG. 1 shows, schematically, a device 100 for hot forming, in particular for press-quenching, a part 106. The device consists of a top tool 102 and a bottom tool 104, between which is arranged the part 106 that is to be shaped during the hot forming process, in particular press-quenching. The part 106 that is to be shaped can be introduced into the device 100 as a planar, pre-perforated sheet metal cutout in the hot state (single-stage hot forming) or as an already cold, pre-shaped semi-finished product (two-stage hot forming) in the hot state.

[0022] A die 108 is installed in a first opening 116 of the top tool 102. The die 106 has means 110 for controlling the temperature of the die 106. The bottom tool 104 has a second opening 118 for receiving both the die 108 and a drawn collar 112 of the part 106. It is thus necessary for the second opening 118 to have a greater radius or diameter than the first opening 116.

[0023] Another prerequisite for collar drawing is a first opening 116 in the part 106, through which the temperature-controlled die 108 can be driven prior to or during the hot forming process. The rim hole 114 can be introduced, prior to hot forming, into the still-cold shaped plate of the part 106 or by means of a hot step immediately prior to collar drawing in the hot forming tool 100.

[0024] In a shaping step, the geometry of the rim hole 114 and of the collar 112 of the part 106 are drawn and/or calibrated, by means of the extending temperature-controlled die 108, into the hot part 106 that is to be press-quenched. Alternatively, the top tool and the die are designed as one unit. In that portion of the part 106 in which the maximum material hardness is to be achieved by transition to martensite, the pressing tool 100 is cooled conventionally, for example by active cooling or by tool mass.

[0025] The inventive method for producing break-resistant collars of a press-quenched part is characterized in that the die 108 that is inserted into the part prior to or during the hot forming process is temperature-controlled during the entire shaping process such that no martensite formation takes place in the region of the collar, with the result that there forms, here locally, a soft mixed structure having greater elongation at break and greater ductility, while the remaining region of the part 106 is given maximum hardness by high cooling rates. The collar-drawing die 108 remains in the rim hole 114 during the entire hardening process and is actively temperature-controlled by the temperature-control means 110. By means of constant, suitable temperature control of the die 108, the temperature in the part 106, in the local region of the collar 112, always remains above the martensite start temperature, thus making it possible to have a localized region of high ductility and elongation at break, and collar drawing without edge cracks. Preferably, a region 124 encircling the rim hole 114 is not fully hardened, in order to create a continuous transition between the fully hardened region and the lower-strength region. The encircling region 124 is for example at most twice and preferably at most 1.5 times the diameter D of the rim hole. This region 124 can be set by the means 120, 122 integrated into the top and bottom tools 102, 104. The means 120, 122 may be temperature-controlled or be made of a material having poor thermal conductivity, for example a ceramic. Preferably, at least the means 120 has insulation for thermal separation between the temperature-controlled die 108 and the preferably actively cooled top tool 102.

[0026] The locally different material hardness can effectively counteract material wear phenomena that are caused by repeated alternating loads from other attached parts, or stress peaks caused by assembling different parts. The service life of connected parts can be significantly extended and the safety for example of a multi-component vehicle chassis can be substantially increased.

LIST OF REFERENCE SIGNS

[0027] 100 Device for hot forming, in particular for press-quenching [0028] 102 Top tool [0029] 104 Bottom tool [0030] 106 Part [0031] 108 Die [0032] 110 Temperature control means [0033] 112 Collar [0034] 114 Rim hole [0035] 116 First opening [0036] 118 Second opening [0037] 120 Means [0038] 122 Means [0039] 124 Encircling region [0040] D Diameter