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CN-122003304-A - Pressing method for steel and use of steel

CN122003304ACN 122003304 ACN122003304 ACN 122003304ACN-122003304-A

Abstract

Examples of methods of thermoforming a structural component are provided. The method includes heating a blank made of ultra-high strength steel having an aluminum coating and forming the heated blank in a multi-step process line or apparatus.

Inventors

  • Holden Castile Amorino
  • Manuel Lopez Lahh

Assignees

  • 昂登坦工程有限公司

Dates

Publication Date
20260508
Application Date
20240807
Priority Date
20230807

Claims (15)

  1. 1. A method for thermoforming a structural component in a multi-step production line, the method comprising: a press tool configured for stretching a blank, wherein the press tool comprises an upper press die and a lower press die, A first rear press tool arranged downstream of the press tool and configured for performing a first rear press operation and comprising an upper first rear press die and a lower first rear press die, the upper press die and the upper first rear press die being configured for operating in unison, and A transfer system for transferring blanks from the press tool to the first post press tool, and the method comprising: Providing a press hardenable boron steel blank, preferably having a carbon content of 0.32-0.45 wt%, a manganese content of 0.6-1.5 wt% and a boron content of 0.003-0.006 wt%, and wherein the press hardenable boron steel blank optionally has an AlSi coating; heating the blank above austenitizing temperature, and Stretching the heated blank in the press tool and transferring the formed blank from the press tool to the first post press tool, Wherein the temperature of the blank is at least 600 ℃, in particular at least 650 ℃, and prior to stretching the blank Wherein the temperature of the blank formed prior to the first post-press operation is 500 ℃ to 650 ℃, and wherein The temperature of the formed blank at the end of the first post-press operation is 400 ℃ to 550 ℃.
  2. 2. The method of claim 1, wherein the press hardenable boron steel blank has a content of 0.32-0.38 wt%, a manganese content of 0.6-1.4 wt%, and a boron content of 0.004-0.005 wt%.
  3. 3. The method according to claim 1 or 2, wherein the temperature of the blank is 650 ℃ to 900 ℃, in particular 700 ℃ to 800 ℃, before stretching the blank.
  4. 4. A method according to any one of claims 1-3, wherein the blank is heated to 870-930 ℃, in particular wherein the blank is heated to 900-930 ℃, and optionally wherein the blank is heated in a furnace.
  5. 5. The method of any of claims 1-4, wherein the multi-step production line further comprises a second back press tool disposed downstream of the first back press tool and configured to perform a second back press operation, and comprising an upper second back press die configured to operate in concert with the upper press die and the upper first back press, and a lower second back press die, and wherein the transfer system is further configured to transfer the formed blank from the first back press tool to the second back press tool.
  6. 6. The method of claim 5, wherein the temperature of the formed blank at the end of the second post-press operation is 350 ℃ to 450 ℃.
  7. 7. The method of claim 5 or 6, wherein the multi-step production line further comprises one or more additional tools disposed downstream of the second post-press operation tool, the additional tools configured to operate in concert with the press tool and the first and second post-press tools.
  8. 8. The method of claim 7, wherein the last additional tool is a re-stamping tool, and wherein the temperature of the shaped blank prior to re-stamping is 250 ℃ to 350 ℃.
  9. 9. The method of any of claims 1-8, wherein the operational cycle of the pressing tool is 2 seconds to 5 seconds, specifically 2.5 seconds to 4.5 seconds, and more specifically about 4 seconds, and Wherein the transfer time between the pressing tool and the first post-pressing tool is 1 second to 3 seconds, specifically 1.5 seconds to 2.5 seconds, more specifically about 2 seconds, and optionally wherein the transfer of blanks occurs before the upper dies have reached their highest position.
  10. 10. The method of any one of claims 1-9, wherein the resulting structural component has an ultimate tensile strength of greater than 1.600 MPa, specifically 1.600 MPa-1.800 MPa, more specifically about 1.700 MPa, and Wherein the structural component obtained has a yield strength of 1.000 MPa or more, specifically 1.100-1.300 MPa.
  11. 11. The method according to any one of claims 1-10, wherein the structural component obtained has an a50 elongation of 5% or more.
  12. 12. The method according to any one of claims 1 to 11, further comprising bake hardening the obtained structural component, wherein the temperature of the bake hardening is 170 ℃ to 200 ℃, and wherein the bake hardening time is 15 minutes to 25 minutes, in particular wherein the yield strength of the obtained structural component is 1.050 MPa or more, in particular 1.200 MPa or more.
  13. 13. The method according to any one of claims 1-12, wherein the structural component after forming has a length of at least 1 meter, in particular 1-2 meters, and the structural component after forming has a width of at least 1 meter, in particular 1-2 meters, and in particular wherein the structural component is a unitary door ring.
  14. 14. The method of any one of claims 1-13, wherein the press hardenable boron steel blank is made of 34MnB4 steel or 37MnB5 steel.
  15. 15. The method of any of claims 1-14, wherein the multi-step production line comprises a multi-step tool comprising a fixed lower body, a movable upper body, and a mechanism configured to provide an upward and downward pressing progression of the movable upper body relative to the lower body, and wherein the upper press mold is connected to the movable upper body and the lower press mold is connected to the fixed lower body and the first upper rear press mold is connected to the movable upper body and the first lower rear press mold is connected to the fixed lower body.

Description

Pressing method for steel and use of steel Technical Field The present application claims the benefit of the 23382824.3 application filed on 7/8/2023. The present disclosure relates to a method for manufacturing a thermoformed structural component and the use of ultra-high strength steel in a thermoforming process. Background In the field of vehicle construction, the development and implementation of lightweight materials or components is becoming increasingly important in order to meet the standards for lightweight construction. The need for weight reduction is driven in particular by the goal of reducing CO 2 emissions. Increasing concerns about passenger safety have also led to the adoption of materials that improve vehicle integrity during collisions while also improving energy absorption. A process known as hot forming press Hardening (HFDQ), also known as hot stamping or press hardening, uses, for example, a boron steel sheet to produce a stamped part having Ultra High Strength Steel (UHSS) characteristics with a tensile strength of, for example, 1.500 MPa or higher. The increase in strength compared to other materials allows for the use of thinner gauge materials, which results in a weight reduction over conventional cold stamped mild steel components. To improve corrosion protection before, during or after the hot stamping process, a coating may be applied. For example, the use of Al-Si or Zn coatings is known. Depending on the composition of the steel-based material, it may be necessary to quench (i.e., rapidly cool) the blank to obtain high tensile strength. Examples of steel materials that can be hardened by cooling them to room temperature by air cooling at a relatively low cooling rate are also known. These steels may be referred to as "air hardenable" steels. The hot stamping process may be performed in such a way that the blank to be hot formed is heated to a predetermined temperature, e.g. to or above the austenitizing temperature, by e.g. a furnace system, in order to reduce the strength of the blank, i.e. to facilitate the hot stamping process. The heated blank may be formed, for example, by a pressing system having a lower temperature (e.g., room temperature) and temperature control than the blank, and thus the forming process and heat treatment using a temperature difference may be performed. The hot stamping process may include a conveyor or a transfer device that transfers the heated blank from the oven to a pressing tool configured to press the blank. Upstream of the furnace system, a cutting system for cutting blanks directly from coil of steel may be provided. The use of multi-step pressing equipment for the manufacture of thermoformed components is known. The multi-step pressing apparatus may include a plurality of tools configured to perform different operations on different blanks simultaneously. With such an arrangement, multiple blanks may be subjected to different manufacturing steps simultaneously during each stroke of the pressing apparatus. The efficiency and performance of the multi-step apparatus may be higher than systems employing multiple different machines or apparatuses for different manufacturing steps (e.g., laser trimming or hard cutting). When using zinc coated steel blanks, the blanks need to be cooled to a certain temperature prior to the hot forming process to reduce or minimize problems such as microcracking. Once the blank has been cooled, it is transferred from the external pre-cooling tool to the multi-step pressing apparatus. US 2022/0258223 discloses a pressing apparatus and method for manufacturing thermoformed structural components. The apparatus includes a fixed lower body and a movable upper body. The apparatus includes a cooling tool and a pressing tool disposed downstream of the cooling tool, and a blank transfer mechanism that transfers blanks from the cooling tool to the pressing tool. The cooling means has an upper gas cooling means connected to the movable upper body and/or a lower gas cooling means connected to the fixed lower body. The press tool includes an upper press die connected to the upper body and a lower press die connected to the lower body. EP 3 437 A1 discloses an example of a method of thermoforming a structural part. The method includes heating a blank made of ultra-high strength steel having an aluminum coating and forming the heated blank in a multi-step apparatus. EP3067129 A1 discloses a pressing system for producing thermoformed structural parts. The system includes a fixed lower body, a movable upper body, and a mechanism configured to provide an upward and downward pressing progression of the movable upper body relative to the fixed lower body. The system further comprises a cooling/heating tool configured for cooling and/or heating a previously heated blank having locally different microstructures and mechanical properties, the cooling/heating tool comprising upper and lower mating dies, and the upper and lower dies comp