Hot formed steel sheet component and method for producing the same as well as steel sheet for hot forming

Abstract

A hot formed steel sheet component including: a chemical composition including in terms of mass % C at from 0.100% to 0.340%, Si at from 0.50% to 2.00%, Mn at from 1.00% to 3.00%, P at 0.050% or less, S at 0.0100% or less, sol. Al at from 0.001% to 1.000%, and N at 0.0100% or less, with a remainder consisting of Fe and impurities; and a steel structure including ferrite, at least one of tempered martensite or tempered bainite, and martensite, wherein an area rate of ferrite is from 5% to 50%, a total area rate of tempered martensite and tempered bainite is from 20% to 70%, an area rate of martensite is from 25% to 75%, a total area rate of ferrite, tempered martensite, tempered bainite and martensite is 90% or more, and an area rate of retained austenite is from 0% to 5%.

1 . A steel component after hot pressing, comprising:
 a chemical composition comprising, in terms of mass %, C at from 0.100% to 0.340%, Si at from 0.50% to 2.00%, Mn at from 1.00% to 3.00%, P at 0.050% or less, S at 0.0100% or less, sol. Al at from 0.001% to 1.000%, and N at 0.0100% or less, with a remainder consisting of Fe and impurities; and   a steel structure comprising ferrite, at least one of tempered martensite or tempered bainite, and martensite, wherein an area rate of ferrite is from 5% to 50%, a total area rate of tempered martensite and tempered bainite is from 20% to 70%, an area rate of martensite is from 25% to 75%, a total area rate of ferrite, tempered martensite, tempered bainite and martensite is 90% or more, and an area rate of retained austenite is from 0% to 5%.   
     
     
         2 . The steel component after hot pressing according to  claim 1 , wherein the chemical composition comprises at least one selected from the group consisting of Ti at 0.200% or less, Nb at 0.200% or less, V at 0.200% or less, Cr at 1.000% or less, Mo at 1.000% or less, Cu at 1.000% or less, Ni at 1.000% or less, B at 0.0025% or less, Ca at 0.0100% or less, Mg at 0.0100% or less, REM at 0.0100% or less, Zr at 0.0100% or less, and Bi at 0.0100% or less, in terms of mass %. 
     
     
         3 - 5 . (canceled) 
     
     
         6 . A steel sheet for hot pressing, comprising:
 a chemical composition comprising, in terms of mass %, C at from 0.100% to 0.340%, Si at from 0.50% to 2.00%, Mn at from 1.00% to 3.00%, P at 0.050% or less, S at 0.0100% or less, sol. Al at from 0.001% to 1.000%, and N at 0.0100% or less, with a remainder consisting of Fe and impurities; and   a steel structure comprising ferrite with an aspect ratio of 2.0 or less, and at least one of martensite or bainite, wherein an area rate of ferrite is from 5% to 50%, a total area rate of martensite and bainite is from 45% to 90%, and a total area rate of ferrite, martensite, and bainite is 90% or more.   
     
     
         7 . The steel sheet for hot pressing according to  claim 6 , wherein the chemical composition comprises at least one selected from the group consisting of Ti at 0.200% or less, Nb at 0.200% or less, V at 0.200% or less, Cr at 1.000% or less, Mo at 1.000% or less, Cu at 1.000% or less, Ni at 1.000% or less, B at 0.0025% or less, Ca at 0.0100% or less, Mg at 0.0100% or less, REM at 0.0100% or less, Zr at 0.0100% or less, in terms of mass %, and Bi at 0.0100% or less, in terms of mass %. 
     
     
         8 - 10 . (canceled) 
     
     
         11 . A method for producing a steel component after hot pressing, the method comprising: heating the steel for hot pressing according to  claim 6  to a temperature range of 720° C. or higher but lower than an Ac 3  point; performing hot pressing within a time period of from 3 sec to 20 sec, during which the steel sheet is exposed to air cooling from the end of the heating until the initiation of the hot pressing; and cooling to a temperature range not above an M S  point at an average cooling rate of from 10° C./sec to 500° C./sec.