Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D37/00—Tools as parts of machines covered by this subclass
  • B21D37/16—Heating or cooling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
  • B21D22/02—Stamping using rigid devices or tools
  • B21D22/022—Stamping using rigid devices or tools by heating the blank or stamping associated with heat treatment

Definitions

• the present invention has as its subject a method of hot forming metal plates.
• the procedure is known in the art of pressing steel plates that envisages heating the plate to a temperature of about 1000°C, forming it in a die, and cooling it inside this die by means of a cooling circuit using water.
• This hot forming procedure makes it possible to obtain pressed steel plates, even in considerably complex shapes, which are endowed with elevated mechanical resistance.
• the forming process indicated above is afflicted with the great disadvantage of requiring a large expenditure of energy, and of having relatively long cycle times.
• the present invention envisages a procedure for hot forming metal plates which is free from the disadvantages indicated above.
• the present invention concerns a method for hot forming having the characteristics of claim 1.
• the present invention furthermore, concerns equipment for hot forming metal plates having the characteristics of claim 5.
• Preferred forms of embodiment of the invention are presented in the dependent claims.
• the method according to the present invention is suitable for any plate in metallic material. Excellent results in terms of precision of processing and mechanical strength of the finished article have been obtained with this method especially with steel plates, and specifically with boron steel plates.
• the method of hot forming according to the present invention envisages first of all a stage of heating the plate to be formed, which is carried out by induction heating means.
• induction heating means can be of any type suitable for heating the plate to be formed through induction, such as for example an induction furnace.
• induction heating means are suitable for creating a low voltage in the plate to be formed, and at the same time a high intensity of current across the plate, by means of which the latter is heated very rapidly.
• the temperature which the plate must reach is preferably around 1000°C.
• Induction heating means can also be used, subsequently to the drawing or forming operation, and prior to an operation of trimming the formed plate, for heating the perimeter zones of the plate, which then need to be cut during the trimming, the object being to limit the effort needed and the stresses on the trimming blades, and so prolong their useful life.
• the method according to the invention therefore provides for forming the plate in a die, and subsequently cooling it while it is still in the die, by means of a flow of liquid nitrogen or a double flow of liquid nitrogen and water.
• an important characteristic of the method according to the present invention consists in the fact that the cooling of the formed plate is performed when the die is in the completely closed condition at the end of forming, with the formed plate still inside it, and is performed by means of a flow of liquid nitrogen or a double flow of liquid nitrogen and water, which flows in proximity to the plate through channels in the die, without coming into contact with it.
• the die for forming the plate and subsequently cooling it comprises one or more matrices, defining respective forming surfaces of the die, which include one or more channels passing through the matrices in proximity to the forming surfaces, but without flowing out onto them.
• the above-mentioned channels are configured for being traversed by a flow of nitrogen generated by means of a recirculating pump communicating with the above-mentioned channels.
• Further channels of the type indicated above are also formed in the matrices and configured for being traversed by a flow of refrigerated water generated by means of a recirculating pump communicating with the above-mentioned further channels.
• the nitrogen which is forced through the channels in the die is at a temperature of about -270°C.
• the equipment for the execution of the method described here can also include automatic transfer means, capable of picking up the plate that is to be formed (which has been heated) and locating it in the die, and subsequently carrying the pressed plate to a position downstream of the die.
• the method of forming metal plates according to the present invention makes it possible to eliminate the use of anti-oxidant layers with which the plates are coated in order to limit the oxidisation processes favoured during pressing by the high temperatures. This is because the cycle times of the method of forming according to the present invention are so much reduced, and most importantly the induction heating which it provides is so fast, that the plates remain at high temperature for a time that is insufficient for the process of oxidisation to be able to significantly alter the plate being pressed, even if it is lacking any kind of anti-oxidant layer.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Shaping Metal By Deep-Drawing, Or The Like (AREA)

Priority Applications (1)

Applications Claiming Priority (1)

Publications (1)

Family

ID=40276080

Family Applications (1)

Country Status (1)

Cited By (4)

Citations (5)

• 2008
  • 2008-10-09 EP EP08425657A patent/EP2175041A1/de not_active Withdrawn

Patent Citations (5)

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