Hot-stamped article using a tailor welded blank method and a method of manufacturing the same

Abstract

A hot-stamped article and a method of manufacturing same use a tailor welded blank (TWB) method capable of controlling the microstructure of a weld portion to prevent fracture of the weld portion. The method includes: preparing a first sheet and a second sheet having different upper austenite transformation temperatures (A3 temperatures); welding the first sheet and the second sheet using a TWB method to prepare a welded sheet obtained as a result of the first sheet and the second sheet being welded to each other via a weld portion; and hot-stamping the welded sheet heated within a temperature range between an A3 temperature of the first sheet and an A3 temperature of the second sheet.

What is claimed is: 
     
         1 . A method of manufacturing a hot-stamped article, the method comprising:
 a preparation step of preparing a first sheet and a second sheet having different upper austenite transformation temperatures (A3 temperatures);   a welding step of welding the first sheet and the second sheet using a tailor welded blank (TWB) method to prepare a welded sheet obtained as a result of the first sheet and the second sheet being welded to each other via a weld portion; and   a hot-stamping step of hot-stamping the welded sheet heated within a temperature range between an A3 temperature of the first sheet and an A3 temperature of the second sheet.   
     
     
         2 . The method according to  claim 1 , wherein, in the preparation step,
 a sheet comprising 0.04 to 0.12 wt% of carbon (C), 0.80 wt% or less of silicon (Si), 1.60 to 2.00 wt% of manganese (Mn), 0.030 wt% or less of phosphorus (P), 0.015 wt% or less of sulfur (S), 0.10 to 0.60 wt% of chromium (Cr), 0.0008 to 0.0050 wt% of boron (B), and a remaining wt% of iron (Fe) and other inevitable impurities is prepared as the first sheet, and   a sheet comprising 0.27 to 0.33 wt% of C, 0.40 wt% or less of Si, 1.10 to 1.60 wt% of Mn, 0.030 wt% or less of P, 0.015 wt% or less of S, 0.10 to 0.60 wt% of Cr, 0.0008 to 0.0050 wt% of B, and a remaining wt% of Fe and other inevitable impurities is prepared as the second sheet.   
     
     
         3 . The method according to  claim 2 , wherein the welded sheet is heated to 810 to 880° C. in the hot-stamping step. 
     
     
         4 . The method according to  claim 1 , wherein, after the hot-stamping step,
 each of the first sheet and the weld portion of the hot-stamped article has a composite structure comprising ferrite, bainite, and martensite, and   the second sheet of the hot-stamped article has a martensite structure.   
     
     
         5 . The method according to  claim 4 , wherein, after the hot-stamping step, each of the first sheet and the weld portion has a structure comprising 30% or less of martensite. 
     
     
         6 . The method according to  claim 5 , wherein, after the hot-stamping step, each of the first sheet and the weld portion has a composite structure comprising 10 to 50% of ferrite, 10 to 50% of bainite, and 30% or less of martensite. 
     
     
         7 . The method according to  claim 1 , wherein, after the hot-stamping step,
 the first sheet of the hot-stamped article has a hardness of 200 to 350 Vickers Pyramid Number (HV),   the weld portion of the hot-stamped article has a hardness of 350 to 550 HV, and   the second sheet of the hot-stamped article has a hardness of 550 to 650 HV.   
     
     
         8 . The method according to  claim 1 , wherein, in the welding step, the weld portion is a volume between the first sheet and the second sheet where the composition of the first sheet is mixed with the composition of the second sheet.