Method for manufacturing hot press forming part and hot press forming part

Abstract

In manufacturing a hot press forming part by hot pressing, using a tool of press forming, a coated steel sheet, the tool of press forming having a die, a blank holder, and a punch, edges of the coated steel sheet heated to a temperature range of Ac 3 transformation temperature to 1000° C. are cooled with the edges squeezed between the die and the blank holder to a temperature of 550° C. or lower and 400° C. or higher at a cooling rate of 100° C./s or higher, press forming is performed so that the press forming is started when the edges reach a temperature of 550° C. or lower and 400° C. or higher, and after the press forming, a formed body is quenched with the formed body held at the press bottom dead center while being squeezed by the tool of press forming.

1 . A method for manufacturing a hot press forming part by hot pressing, using a tool of press forming, a coated steel sheet that is obtained by forming a Zn—Ni coating layer on a surface of a steel sheet, the tool of press forming having a die, a blank holder, and a punch, the method comprising:
 cooling edges of the coated steel sheet heated to a temperature range of Ac 3  transformation temperature to 1000° C., with the edges squeezed between the die and the blank holder, to a temperature of 550° C. or lower and 400° C. or higher at a cooling rate of 100° C./s or higher; 
 performing press forming so that the press forming is started when the edges reach a temperature of 550° C. or lower and 400° C. or higher; and 
 
       after the press forming, quenching a formed body with the formed body held at the press bottom dead center while being squeezed by the tool of press forming. 
     
     
         2 . The method for manufacturing a hot press forming part according to  claim 1 , wherein the cooling and the press forming are performed while slidably moving the die with the coated steel sheet so that slidable movement is temporarily stopped before the coated steel sheet is brought into contact with the punch, or so that slidable movement before the coated steel sheet coming into contact with the punch is slower than slidable movement during press forming after the coated steel sheet coming into contact with the punch. 
     
     
         3 . The method for manufacturing a hot press forming part according to  claim 1 , wherein in the press forming, the blank holder is detached from the coated steel sheet to perform crush forming without using the blank holder. 
     
     
         4 . The method for manufacturing a hot press forming part according to  claim 1 , wherein in the press forming, draw forming is performed with the coated steel sheet squeezed between the die and the blank holder. 
     
     
         5 . The method for manufacturing a hot press forming part according to  claim 1 , wherein the Zn—Ni coating layer contains Ni in an amount of 9 mass % or more and 25 mass % or less. 
     
     
         6 . A hot press forming part manufactured by the method as recited in  claim 1 . 
     
     
         7 . The method for manufacturing a hot press forming part according to  claim 2 , wherein in the press forming, the blank holder is detached from the coated steel sheet to perform crush forming without using the blank holder. 
     
     
         8 . The method for manufacturing a hot press forming part according to  claim 2 , wherein in the press forming, draw forming is performed with the coated steel sheet squeezed between the die and the blank holder. 
     
     
         9 . The method for manufacturing a hot press forming part according to  claim 2 , wherein the Zn—Ni coating layer contains Ni in an amount of 9 mass % or more and 25 mass % or less. 
     
     
         10 . The method for manufacturing a hot press forming part according to  claim 3 , wherein the Zn—Ni coating layer contains Ni in an amount of 9 mass % or more and 25 mass % or less. 
     
     
         11 . The method for manufacturing a hot press forming part according to  claim 4 , wherein the Zn—Ni coating layer contains Ni in an amount of 9 mass % or more and 25 mass % or less. 
     
     
         12 . The method for manufacturing a hot press forming part according to  claim 7 , wherein the Zn—Ni coating layer contains Ni in an amount of 9 mass % or more and 25 mass % or less. 
     
     
         13 . The method for manufacturing a hot press forming part according to  claim 8 , wherein the Zn—Ni coating layer contains Ni in an amount of 9 mass % or more and 25 mass % or less. 
     
     
         14 . A hot press forming part manufactured by the method as recited in  claim 2 . 
     
     
         15 . A hot press forming part manufactured by the method as recited in  claim 3 . 
     
     
         16 . A hot press forming part manufactured by the method as recited in  claim 4 . 
     
     
         17 . A hot press forming part manufactured by the method as recited in  claim 5 . 
     
     
         18 . A hot press forming part manufactured by the method as recited in  claim 7 . 
     
     
         19 . A hot press forming part manufactured by the method as recited in  claim 8 . 
     
     
         20 . A hot press forming part manufactured by the method as recited in  claim 9 .