Three-dimensional cooling type hot-stamping method and system and vehicle structural member manufactured by the same

A hot-stamping method, comprising:

• performing a three-dimensional cooling mode in which, a closed-section product disposed in an upper mold and a lower mold that are coupled to each other is heat-treated under control of a controller,
• wherein the three-dimensional cooling mode includes:
• coupling the upper mold with the lower mold after a product to be formed has been disposed on a die of the lower mold, and stamping the product using the upper mold and manufacturing the product into the closed-section product;
• performing an external cooling water direct spraying operation of directly spraying a cooling water onto an external portion of the closed-section product by an upper-mold direct spray device disposed in the upper mold after the upper mold and the lower mold have been coupled with each other;
• performing the external cooling water direct spraying operation of directly spraying the cooling water onto the external portion of the closed-section product by a lower-mold direct spray device disposed in the lower mold after the upper mold and the lower mold have been coupled with each other;
• performing an internal cooling water direct spraying operation of directly spraying the cooling water into an internal volume of the closed-section product by one of a first closed-section cooling water spray device disposed on a one side of the upper and lower molds and a second closed-section cooling water spray device provided on an opposite side thereof, after the upper mold and the lower mold have been coupled with each other;
• and
• continuing the external cooling water direct spraying operation and the internal cooling water direct spraying operation during a time of a heat treatment,
• wherein the internal cooling water direct spraying operation forms a partial closed cooling water circulation flow in the closed-section product, wherein the partial closed cooling water circulation flow is formed such that the cooling water is drawn from the first closed-section cooling water spray device and flows along the internal volume of the closed-section product, and when the cooling water reaches the second closed-section cooling water spray device, a unblocked cooling water flow and a blocked cooling water flow are formed by the second closed-section cooling water spray device, and the unblocked cooling water flow is discharged through the second closed-section cooling water spray device while the blocked cooling water flow remains in the closed-section product, and
• wherein the blocked cooling water flow of the cooling water that is blocked by valve connectors of a lower cooling water block of the second closed-section cooling water spray device returns from an opposite side end portion of the closed-section product to a one side end portion of the closed-section product, and the blocked cooling water flow remains, rather than being discharged externally, in closed-sections of the closed-section product because of cooling water that is drawn into a lower cooling water block of the first closed-section cooling water spray device, and
• wherein a valve connector of an upper cooling water block of the second closed-section cooling water spray device is turned on in order for the unblocked cooling water flow to be discharged through the second closed-section cooling water spray device, the upper cooling water block being located above the lower cooling water block.