FURNACE ROLLER, ROLLER HEARTH FURNACE, USE OF THE FURNACE ROLLER AND PROCESS FOR PRODUCTION OF A HOT-FORMED AND AT LEAST PARTLY PRESS-HARDENED VEHICLE COMPONENT

Abstract

A furnace roller for a roller hearth furnace has a hollow cylindrical ceramic roller body having an outer oxidic coating. The roller body has outer longitudinal fins and longitudinal grooves that run in linear longitudinal direction of the roller body. The configuration reduces the contact area between the roller body and the blanks to be transported. The furnace rollers are suitable for use in roller furnaces in hot forming lines for the press hardening of AlSi-coated steel blanks.

Claims

1-11. (canceled)

12. A furnace roller, the furnace roller comprising: a roller body, wherein the roller body has an outer coating, the roller body has outer longitudinal fins and longitudinal grooves both extending linearly in a longitudinal direction of the roller body, and the roller body has a hollow cylinder shape.

13. The furnace roller according to claim 12, where the roller body comprises a ceramic material.

14. The furnace roller according to claim 12, wherein each of the longitudinal fins has a rounded end face, and each of the longitudinal grooves has a rounded groove base.

15. The furnace roller according to claim 14, wherein the rounded end face has a first radius and the rounded groove base has a second radius , and the first radius is greater than the second radius.

16. The furnace roller according to claim 14, wherein each of the longitudinal fins has a fin height, the roller body has a wall thickness measured between the rounded groove base and an inner circumference of an interior of the roller body, and a ratio of the fin height to the wall thickness of the roller body is between 1:1 and 1:2.

17. The furnace roller according to claim 12, wherein the roller body has a middle length section and terminal end sections, the middle length section has an external diameter greater than an external diameter of the terminal end sections.

18. The furnace roller according to claim 12, wherein the roller body comprises an extrudate.

19. The furnace roller according to claim 12, wherein the outer coating comprises at least one oxide selected from the group consisting of aluminum oxide (Al.sub.2O.sub.3), zirconium(IV) oxide (ZrO.sub.2), chromium(III) oxide (Cr.sub.2O.sub.3), yttrium oxide (Y.sub.2O.sub.3), silicon dioxide (SiO.sub.2), calcium oxide (CaO), magnesium oxide (MgO), potassium oxide (K.sub.2O), titanium(IV) oxide (TiO.sub.2), iron(II) oxide (FeO), or boron nitride (BN).

20. The furnace roller according to claim 12, wherein the roller body comprises an interior and terminal end sections, and in each terminal end section of the terminal end sections comprises a geopolymer plug.

21. A method of making a hot-formed and press-hardened vehicle component, the method comprising: using an Al-Si-precoated steel sheet comprising a temperable steel alloy; heating the Al-Si-precoated steel sheet; forming an alloy of the Al-Si precoated steel sheet in a roller hearth furnace; transferring the heated Al-Si-precoated steel sheet to an at least partly cooled press mold; and hot forming and press hardening the Al-Si-precoated steel sheet in the press mold, wherein, in the heating and the forming of the alloy, at least a furnace roller according to claim 12 is used, and the heating and the forming of the alloy are at a furnace temperature between 800° C. and 980° C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present disclosure is additionally described hereinafter with reference to drawings. The figures show:

[0047] FIG. 1 a perspective view of a furnace roller according to the present disclosure;

[0048] FIG. 2 the furnace roller in a side view according to the present disclosure; and

[0049] FIG. 3 an end view of the furnace roller according to the present disclosure.

DETAILED DESCRIPTION

[0050] With reference to FIG. 1, FIG. 2 and FIG. 3, an furnace roller 1 for a roller hearth furnace is elucidated.

[0051] The furnace roller 1 has a hollow cylindrical roller body 2 made of a ceramic material. The roller body 2 comprises of mullite. The roller body 2 has a middle length section 3 and an end section 4, 5 at either end. The middle length section 3 of the roller body 2 has been provided with an outer coating 6. The coating 6 comprises an oxidic material. The coating 6 comprises a mixture of zirconium oxide, aluminum oxide, boron nitride and/or silicate. The outer coating 6 has been applied in the middle length section 3.

[0052] The coating 6 is executed as a thermally sprayed layer. The coating 6 is also able to be formed by an applied and baked suspension.

[0053] The roller body 2 has outer longitudinal fins 7 and longitudinal grooves 8 that run in linear longitudinal direction of the roller body 2. In the working example shown, the longitudinal fins 7 and the longitudinal grooves 8 formed in between extend in a linear manner over the entire length L of the roller body 2. The longitudinal fins 7 are also able to be interrupted over the course of the length L of the roller body 2.

[0054] The longitudinal fins 7 and the longitudinal grooves 8 that run in between are distributed homogeneously over a circle sector on the outer circumference of the roller body 2. The longitudinal fins 7 are arranged over the circumference of the roller body 2 in a circle sector, each offset at an angle α.

[0055] The longitudinal fins 7 have a rounded outer end face 9. The longitudinal grooves 8 have a rounded groove base 10. The end face 9 of a longitudinal fin 7 has a radius R1. The groove base 10 of a longitudinal groove 8 has a radius R2. The radius R1 of the end face 9 is greater than the radius R2 in the groove base 10.

[0056] The roller body 2 is hollow cylindrical and has an interior 11. Within each of the end sections 4, 5 is disposed a plug made of a geopolymer, which is not shown in the drawings.

[0057] The roller body 2 comprises of a ceramic material and is an extrudate. The end sections 4, 5 have been worked by grinding at the outer circumference. The middle length section 3 has an external diameter d1. In the end sections 4, 5, the roller body 2 has an external diameter d2. The end sections 4, 5 have been worked by grinding and are reduced in diameter, such that the external diameter d1 in the middle length section 3 is greater than the external diameter d2 in the end sections 4, 5. The end sections 4, 5 have a length l1 shorter than the total length L of the roller body 2. The middle length section 3 is several times longer than an end section 4, 5. The middle length section 3 has a transition to a terminal end section 4, 5, in each case via a rounded transition 12 having a radius R3.

[0058] The longitudinal fins 7 have a fin height h. The fin height h is measured from the groove base 10 up to the outer point on an end face 9. In addition, the roller body 2 has a wall thickness s measured between the groove base 10 and the inner circumference d3 of its interior 11. The ratio of the fin height h to the wall thickness s of the roller body 2 is between 1:1 and 1:2, or between 1:1.25 and 1:1.75.

[0059] The outer bearing surface of the furnace roller 1 is reduced by virtue of the configuration of the longitudinal fins 7 with the longitudinal grooves 8 in between. As a result, the contact area between the furnace roller 1 and a metal sheet to be transported is reduced. In addition, a chemical barrier is formed between the furnace roller 1 and the sheet to be transported, which is implemented by the outer coating 6 of the roller body 2.

[0060] In at least one embodiment of the present disclosure, furnace rollers 1 are employed in roller furnaces. The furnace rollers 1 are suitable for roller furnaces in hot forming lines for press hardening of coated steel sheets, such as for press hardening of aluminum-silicon-coated (AlSi-coated) steel sheets.

[0061] The foregoing description of some embodiments of the disclosure has been presented for purposes of illustration and description. The description is not intended to be exhaustive or to limit the disclosure to the precise form disclosed, and modifications and variations are possible in light of the above teachings. The specifically described embodiments explain the principles and practical applications to enable one ordinarily skilled in the art to utilize various embodiments and with various modifications as are suited to the particular use contemplated. Various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the disclosure.