US 12,091,726 B2
Hot-press molding method and hot-press molded product
Eiichi Ota, Nagakute (JP); Yasuhiro Yogo, Nagakute (JP); Tomoaki Ihara, Toyota (JP); and Shinobu Okuma, Toyota (JP)
Assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA, Toyota (JP)
Filed by TOYOTA JIDOSHA KABUSHIKI KAISHA, Toyota (JP)
Filed on Jul. 19, 2021, as Appl. No. 17/378,898.
Application 17/378,898 is a division of application No. 15/807,645, filed on Nov. 9, 2017, granted, now 11,118,242.
Claims priority of application No. 2016-221952 (JP), filed on Nov. 14, 2016.
Prior Publication US 2021/0340643 A1, Nov. 4, 2021
Int. Cl. C21D 9/48 (2006.01); B21D 22/02 (2006.01); B21D 22/20 (2006.01); C21D 1/22 (2006.01); C21D 1/673 (2006.01); C21D 7/13 (2006.01); C21D 8/00 (2006.01); C22C 38/04 (2006.01); C22C 38/18 (2006.01); C22C 38/38 (2006.01); C21D 9/00 (2006.01); C21D 9/46 (2006.01)
CPC C21D 9/48 (2013.01) [B21D 22/022 (2013.01); B21D 22/208 (2013.01); C21D 1/22 (2013.01); C21D 1/673 (2013.01); C21D 7/13 (2013.01); C21D 8/00 (2013.01); C21D 8/005 (2013.01); C22C 38/04 (2013.01); C22C 38/18 (2013.01); C22C 38/38 (2013.01); C21D 9/00 (2013.01); C21D 9/46 (2013.01); C21D 2211/001 (2013.01); C21D 2211/002 (2013.01); C21D 2211/005 (2013.01); C21D 2211/008 (2013.01); C21D 2211/009 (2013.01)] 2 Claims
OG exemplary drawing
 
1. A hot-press molding method comprising:
a first heating process in which a steel plate is heated and the entire steel plate becomes austenite;
a first cooling process in which a cooling rate of the steel plate after the first heating process is different in a first region of the steel plate and a second region of the steel plate, the first region is cooled below a martensite transformation completion temperature, and the first region is transformed into martensite and the second region other than the first region remains as austenite;
a second heating process in which the entire steel plate is reheated, the first region and the second region are set to be 550° C. or lower so the first region becomes tempered martensite, and so the second region is transformed into ferrite, and pearlite or bainite; and
a second cooling process in which the entire steel plate after the second heating process is cooled to the martensite transformation completion temperature or lower, and the first region is remained as tempered martensite, and the second region is remained as a mixed structure of ferrite, and pearlite or bainite,
wherein at least one of the first cooling process and the second cooling process is performed during a molding process in which the steel plate is press-molded on a molding die.