Heat-hardened steel with excellent crashworthiness and method for manufacturing heat-hardenable parts using same

Abstract

Disclosed are heat-hardened steel with excellent crashworthiness and a method for manufacturing heat-hardenable parts using the same. The heat-hardened steel according to the invention comprises, based on wt %; C: 0.12-0.8%; Cr: 0.01-2%; Mo: 0.2% or less; B: 0.0005-0.08%; Ca: 0.01 or less; Sb: 1.0% or less; and Ti and/or Nb: 0.2%; and the reminder being Fe and inevitable impurities. In addition, the heat-treatment hardening steel satisfies anyone of following conditions i)-iv), wherein condition i) comprises Si: 0.5-3%; Mn: 1-10% and Al: 0.05-2%; condition ii) comprises Si: 1% or less; Mn: 0.5-5%; Al: 0.1-2.5%; and Ni: 0.01-8%; condition iii) comprises Si: 0.5-3%; Mn: 1-10%; Al: 0.1% or less; and Ni: 0.01-8%; and condition iv) comprises Si: 0.5-3%; Mn: 1-10%; Al: 0.1-2.5%; and Ni: 0.01-8%.

1 . A method for manufacturing a heat-treatment hardening component, comprising:
 (a) preparing a blank formed of heat-treatment hardening steel, the heat-treatment hardening steel comprising: by wt %, C: 0.12˜0.8%, Cr: 0.01˜2%, Mo: 0.2% or less, B: 0.0005˜0.08%, Ca: 0.01 or less, Sb: 1.0% or less, at least one of Ti and Nb: 0.2% or less, components satisfying anyone of the following compositions i) to iv), and the balance of Fe and unavoidable impurities;   By wt %,   i) Si: 0.5˜3%; Mn: 1˜10% and Al: 0.05˜2%   ii) Si: 1% or less; Mn: 0.5˜5%; Al: 0.1˜2.5% and Ni: 0.01˜8%   iii) Si: 0.5˜3%; Mn: 1˜10%; Al: 0.1% or less and Ni: 0.01˜8%   iv) Si: 0.5˜3%; Mn: 1˜10%; Al: 0.1˜2.5% and Ni: 0.01˜8%,   (b) heating the blank;   (c) hot-forming and quenching the heated blank in dies; and   (d) performing post-treatment of a formed body formed in the (c) hot-forming and quenching.   
     
     
         2 . The method according to  claim 1 , wherein the (b) heating is performed by heating the blank to a temperature of 700° C. to 1100° C. 
     
     
         3 . The method according to  claim 1 , wherein, in the (c) hot-forming and quenching, quenching is performed by cooling the heated blank in the dies at a rate of 10° C./sec to 300° C./sec to a martensite transformation start temperature or less of the heat-treatment hardening steel. 
     
     
         4 . The method according to  claim 1 , wherein the heat-treatment hardening steel has at least one layer selected from an Al—Si based coating layer, a galvanized layer and a high temperature oxidation resistant coating layer on a surface thereof. 
     
     
         5 . A method for manufacturing a heat-treatment hardening component, comprising:
 (a) preparing a blank formed of heat-treatment hardening steel, the heat-treatment hardening steel comprising:, by wt %, C: 0.12˜0.8%, Cr: 0.01˜2%, Mo: 0.2% or less, B: 0.0005˜0.08%, Ca: 0.01 or less, Sb: 1.0% or less, at least one of Ti and Nb: 0.2% or less, components satisfying anyone of the following compositions i) to iv), and the balance of Fe and unavoidable impurities;   By wt %,   i) Si: 0.5˜3%; Mn: 1˜10% and Al: 0.05˜2%   ii) Si: 1% or less; Mn: 0.5˜5%; Al: 0.1˜2.5% and Ni: 0.01˜8%   iii) Si: 0.5˜3%; Mn: 1˜10%; Al: 0.1% or less and Ni: 0.01˜8%   iv) Si: 0.5˜3%; Mn: 1˜10%; Al: 0.1˜2.5% and Ni: 0.01˜8%,   (a′) performing primary-forming of the blank through cold working;   (b) heating a primary formed body formed in the (a′) performing primary forming;   (c) performing secondary-forming and quenching of the heated primary formed body in dies; and   (d) performing post-treatment of a secondary formed body formed in the (c) performing secondary-forming and quenching.   
     
     
         6 . The method according to  claim 5 , wherein the (b) heating is performed by heating the blank to a temperature of 700° C. to 1100° C. 
     
     
         7 . The method according to  claim 5 , wherein, in the (c) performing secondary-forming and quenching, quenching is performed by cooling the heated blank in the dies at a rate of 10° C./sec to 300° C./sec to a martensite transformation start temperature or less of the heat-treatment hardening steel. 
     
     
         8 . The method according to  claim 5 , wherein the heat-treatment hardening steel has at least one layer selected from an Al—Si based coating layer, a galvanized layer and a high temperature oxidation resistant coating layer on a surface thereof.