Steel sheet plated with Al—Fe alloy for hot press forming having excellent corrosion resistance and heat resistance, hot press formed part, and manufacturing method therefor
A method of manufacturing a steel sheet plated with an Al—Fe alloy for hot forming. The method includes: aluminum-plating and coiling a base steel sheet to obtain an aluminum-plated steel sheet, where an amount of the aluminum-plating is 30 to 200 g/m 2 based on one surface of the base steel sheet, and tension in the coiling is 0.5 to 5 kg/mm 2 ; after the aluminum-plating, performing cooling to 250° C. at a rate of 20° C./sec or less; annealing the aluminum-plated steel sheet to obtain the steel sheet plated with the Al—Fe alloy; and cooling the steel sheet plated with the Al—Fe alloy. The annealing is carried out for 30 minutes to 50 hours within a heating temperature range of 550 to 750° C. in a batch annealing furnace.
1 . A method of manufacturing a steel sheet plated with an Al—Fe alloy for hot forming, the method comprising:
aluminum-plating and coiling a base steel sheet to obtain an aluminum-plated steel sheet, wherein an amount of the aluminum-plating is 30 to 200 g/m 2 based on one surface of the base steel sheet, and tension in the coiling is 0.5 to 5 kg/mm 2 ;
after the aluminum-plating, performing cooling to 250° C. at a rate of 20° C./see or less;
annealing the aluminum-plated steel sheet to obtain the steel sheet plated with the Al—Fe alloy; and
cooling the steel sheet plated with the Al—Fe alloy,
wherein,
the annealing is carried out for 30 minutes to 50 hours within a heating temperature range of 550 to 750° C. in a batch annealing furnace,
when heating from room temperature to the heating temperature during the annealing, an average temperature increase rate is 10 to 100° C./h, and an average temperature increase rate in a 400 to 500° C. section is 1 to 15° C./h,
a difference between an atmospheric temperature in the batch annealing furnace and a steel sheet temperature is 5 to 80° C.,
the Al—Fe alloy comprises:
an alloyed layer (I) on the base steel sheet and including Al: 5 to 30% by weight;
an alloyed layer (II) on the alloyed layer (I) and including Al: 30 to 60% by weight; and
an alloyed layer (III) on the alloyed layer (II) and including Al: 20 to 50% by weight,
FeAl(Si) alloy phases including Al: 20 to 50% and Si: 5 to 20%, by weight, are dispersed and distributed in the alloyed layer (II), and
a number density of the FeAl (Si) alloy phases having a circle-equivalent diameter of 5 μm or less is 10 3 pieces/mm 2 or more.
2 . The method of claim 1 , wherein the base steel sheet comprises, by weight:
C: 0.04 to 0.5%,
Si: 0.01 to 2%,
Mn: 0.1 to 5%,
P: 0.001 to 0.05%,
S: 0.0001 to 0.02%,
Al: 0.001 to 1%,
N: 0.001 to 0.02%, and
a balance of Fe, and other impurities.
3 . The method of claim 2 , wherein the base steel sheet further comprises, by weight, at least one of:
B: 0.001 to 0.01%,
Cr: 0.01 to 1%, or
Ti: 0.001 to 0.2%.
4 . A method of manufacturing a hot press formed part, comprising:
manufacturing the steel sheet according to the method of claim 1 ;
heat-treating the steel sheet within a temperature range of Ac3 to 950° C. for 1 to 15 minutes; and
hot press forming the heat-treated steel sheet.