Method of manufacturing hot deep drawn steel parts of sheet metal

Abstract

The invention relates to a method of manufacturing steel parts of sheet metal by hot deep drawing characterized by bringing the semi-finished product into austenitic condition by heating, subsequently cooling its locations, which would undergo undesirable deformation, to a temperature below the austenite temperature, and then completing the forming process.

Claims

1. A hot deep drawing method of manufacturing steel parts comprising: (a) heating a sheet metal blank to bring the sheet metal blank into austenitic condition; (b) subsequently cooling critical-deformation locations of the sheet metal blank to a temperature below an austenite temperature, wherein the critical-deformation locations comprise undercooled austenite regions of the sheet metal blank and/or regions of mixed microstructures; and (c) subjecting the sheet metal blank to a forming process comprising a forming tool.

2. The method of manufacturing steel parts as claimed in claim 1 wherein the cooling of the critical-deformation locations of the sheet metal blank occurs after the sheet metal blank was heated to the austenitic condition and before the sheet metal blank is placed into the forming tool.

3. The method of manufacturing steel parts as claimed in claim 1 further comprising cooling the sheet metal blank after the heating of step (a) and after placing the sheet metal blank into the forming tool.

Description

EXAMPLE EMBODIMENT

(1) A blank of sheet metal of 1.5 mm thickness of the 22MnB5 steel is heated in a furnace to the temperature of 950 C., at which it is kept in the furnace for the period of 3 minutes. This brings it into fully austenitic condition. After that, it is removed from the furnace and transferred to a tool. Before it is placed into the tool, the transfer is interrupted for approximately 1 second, during which nozzles located above the sheet metal blank blow pressurized mixture of air and water in a controlled manner onto selected locations of the sheet metal blank. This local cooling reduces the temperature in the desired locations down to 500 C. By this means, areas with higher flow stress are created. The plasticity of the material distributed differentially across the semi-finished product in this manner leads to the creation of the desired profile of deformation properties in the particular sheet metal blank. After this, the transfer of the sheet metal blank to the tool is completed. In the tool, the blank is formed in a deep-drawing operation. This entire transfer of the sheet metal blank from the furnace to the tool, including the local cooling, takes approximately 10 seconds. After the deformation, the semi-finished product remains enclosed in the tool for additional 15 seconds in order for the desired hardening-type microstructure to form. By this means, the temperature of the drawn part decreases to less than 150 C. At the same time, the microstructure evolution is thus completed. After that, the pressed part is removed from the mold and cools to the ambient temperature on transport equipment.

INDUSTRIAL APPLICABILITY

(2) The invention can find broad use in the field of sheet metal processing in hot deep drawing applications, predominantly in the manufacture of complex-shaped parts with a large depth of the final shape, which are impossible to make using the conventional route in a single draw.