Heat treatment furnace and method for heat treatment of a pre-coated steel sheet blank and method for production of a motor vehicle part

Patent metadata

Field	Value
Publication number	US-2017183754-A1
Application number	US-201615385835-A
Country	US
Kind code	A1
Filing date	Dec 20, 2016
Priority date	Dec 23, 2015
Publication date	Jun 29, 2017
Grant date	—

Abstract

A heat treatment furnace and a method for heat treatment of a steel sheet blank is disclosed having at least one furnace chamber and a transport system for conveying the steel sheet blanks through the furnace chamber. A preheating chamber, a metallurgical bonding path and a cooling chamber, wherein the steel sheet blank can be heated in the preheating chamber to a temperature of above 200° C. A method for the production of a hot-formed and press-quenched motor-vehicle part is also disclosed.

First claim

1 . Heat treatment furnace for coated steel sheet blanks, having at least one furnace chamber and a transport system for conveying the steel sheet blanks through the furnace chamber, characterized in that there are provided a preheating chamber, a metallurgical bonding path and a cooling chamber, wherein the steel sheet blank can be heated in the preheating chamber to a temperature of above 200° C., can be heated in the metallurgical bonding path to a temperature above the Ac3 temperature, and can be cooled in the cooling chamber to a temperature of below 450° C.

2 . Heat treatment furnace according to claim 1 , characterized in that the preheating chamber is designed as a preheating path, and/or that the cooling chamber is designed as a cooling path.

3 . Heat treatment furnace according to claim, characterized in that the metallurgical bonding path and the preheating path, and/or the cooling path are arranged in a continuous furnace, in particular in parallel one above the other or in parallel next to one another.

4 . Heat treatment furnace according to claim 1 , characterized in that heating means are arranged in the metallurgical bonding path such that a temperature greater than Ac3 prevails, and in that the cooling path and/or the preheating path are separated from the metallurgical bonding path by a temperature-permeable separating layer, such that part of the heat energy of the metallurgical bonding path heats the preheating path and/or the cooling path.

5 . Heat treatment furnace according to claim 1 , characterized in that manipulators are provided at a respective end of the heat treatment furnace such that the heat-treated steel sheet blanks can be transferred to the individual paths, in particular vertical conveyors or horizontal conveyors.

6 . Heat treatment furnace according to claim 1 , characterized in that the cooling chamber is separated from the heat treatment furnace and is operated in particular using exhaust air from the heat treatment furnace.

7 . Method for heat treatment of a pre-coated steel sheet blank, in which a pre-coated steel sheet blank is metallurgically bonded, characterized by the following method steps:
heating the pre-coated steel sheet blank from room temperature to a preheat temperature of greater than 200° C., then heating to a metallurgical bonding temperature above the Ac3 temperature, such that the pre-coating is metallurgically bonded, then cooling the metallurgically bonded steel sheet blank to a cooling temperature of less than 450° C. in a time of greater than 30 s, then storing or further processing the cooled steel sheet blank.

8 . Method according to claim 7 , characterized in that heating is to a preheat temperature above 250° C., in particular 250° C. to 450° C., and/or that cooling is to a cooling temperature between 450° C. and 300° C., and optionally in a further cooling process to a temperature of less than 300° C.

9 . Method according to claim 7 , characterized in that heating to metallurgical bonding temperature is carried out as rapid heating in a time of less than 20 s per mm of sheet thickness of the steel sheet blank to be heated, preferably less than 10 s per mm of sheet thickness, in particular less than 5 s per mm of sheet thickness.

10 . Method according to claim 7 , characterized in that cooling is carried out over more than 30 s per mm of sheet thickness of the sheet metal blank that is to be cooled.

11 . Method according to claim 7 , characterized in that a layer thickness of the coating of less than 0.6 μm and preferably greater than 0.15 μm is created, and/or that the fraction of atomic hydrogen is below 0.5 ppm, in particular below 0.3 ppm.

12 . Method according to claim 7 , characterized in that a steel sheet blank of a quenchable steel alloy with a pre-coating consisting of an Al—Si alloy is heat treated such that at least an intermetallic phase of Fe—Al is formed.

13 . Method according to one claim 7 , characterized in that the heat radiation of the steel sheet blanks that are guided through the cooling path is used to heat the steel sheet blanks that are guided through the preheating path.

14 . Method for producing a hot-formed and press-quenched motor vehicle part, wherein use is made of a pre-coated, metallurgically bonded steel sheet blank produced according to the method of claim 7 , characterized in that the metallurgically bonded steel sheet blank is at least partially and preferably fully heated, in a time of less than 20 s, to a temperature greater than or equal to the austenizing temperature (Ac3), is then hot-formed and press-quenched.

15 . Method according to claim 14 , characterized in that the metallurgically bonded steel sheet blank is rapidly heated from the cooling temperature, or in that the metallurgically bonded steel sheet blank is taken from a store and is at room temperature.

16 . Method according to claim 14 , characterized in that the produced motor vehicle part has, at least in certain regions and particularly throughout, a tensile strength Rm of greater than 1250 MPa, in particular greater than 1450 MPa, and/or that the fraction of atomic hydrogen is below 0.5 ppm, in particular below 0.3 ppm.

Assignees

• Benteler Automobiltechnik Gmbh

Inventors

• Frost Georg
• Kettler Markus
• Bake Karsten

Classifications

• F27D9/00

  Cooling of furnaces or of charges therein (casings, linings, walls or roofs incorporating cooling arrangements F27D1/12) · CPC title

• C21D9/46 Primary

  for sheet metals · CPC title

• C21D9/0056

  Furnaces through which the charge is moved in a horizontal straight path (C21D9/0043 takes precedence) · CPC title

• C21D9/0062

  Heat-treating apparatus with a cooling or quenching zone · CPC title

• C21D6/00

  Heat treatment of ferrous alloys · CPC title