HEAT-HARDENED STEEL WITH EXCELLENT CRASHWORTHINESS AND METHOD FOR MANUFACTURING HEAT-HARDENABLE PARTS USING SAME
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 . 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 any one 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%.
2 . The heat-treatment hardening steel according to claim 1 , wherein the steel comprises a composite microstructure of martensite and retained austenite after heat treatment.
3 . The heat-treatment hardening steel according to claim 1 , wherein the steel has a tensile strength of 490 MPa to 980 MPa, a yield strength of 370 MPa to 600 MPa and an elongation of 20% to 50% before heat treatment.
4 . The heat-treatment hardening steel according to claim 3 , wherein the steel has a tensile strength of 1000 MPa or more, a yield strength of 800 MPa or more and an elongation of 10% or more after heat treatment.
5 . The heat-treatment hardening steel according to claim 1 , wherein the 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.
6 . 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.
7 . The method according to claim 6 , wherein the (b) heating is performed by heating the blank to a temperature of 700° C. to 1100° C.
8 . The method according to claim 6 , 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.
9 . The method according to claim 6 , 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.
10 . 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.
11 . The method according to claim 10 , wherein the (b) heating is performed by heating the blank to a temperature of 700° C. to 1100° C.
12 . The method according to claim 10 , 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.
13 . The method according to claim 10 , 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.