Electric resistance welded steel pipe for an automotive part, and method of producing automotive part

Abstract

An electric resistance welded steel pipe for an automotive part, the pipe comprising a base metal portion and an electric resistance welded portion, wherein the base metal portion has a chemical composition comprising, in terms of % by mass: from 0.42 to 0.48% of C, from 0.01 to 0.20% of Si, from 0.10 to 0.70% of Mn, from 0 to 0.030% of P, from 0 to 0.030% of S, from 0.005 to 0.050% of Al, from 0.005 to 0.040% of Ti, from 0.0005 to 0.0050% of B, and a balance comprising Fe and impurities, wherein a steel structure of the base metal portion is a ferrite-pearlite mixed structure, and wherein the base metal portion has a hardness of from 110 to 150 Hv.

1 . An electric resistance welded steel pipe for an automotive part, the pipe comprising a base metal portion and an electric resistance welded portion,
 wherein the base metal portion has a chemical composition consisting of, in terms of % by mass:   from 0.42 to 0.48% of C,   from 0.01 to 0.20% of Si,   from 0.10 to 0.70% of Mn,   from 0 to 0.030% of P,   from 0 to 0.030% of S,   from 0.005 to 0.050% of Al,   from 0.005 to 0.040% of Ti,   from 0.0005 to 0.0050% of B,   from 0 to 0.005% of N,   from 0 to 0.005% of O,   from 0 to 0.0050% of Ca,   from 0 to 0.0050% of Mg,   from 0 to 0.0050% of REM,   from 0 to 0.50% of Cr,   from 0 to 0.50% of Ni,   from 0 to 0.50% of Cu,   from 0 to 0.10% of Nb,   from 0 to 0.50% of Mo,   from 0 to 0.20% of V, and   a balance consisting of Fe and impurities,   wherein a steel structure of the base metal portion is a ferrite-pearlite mixed structure, and   wherein the base metal portion has a hardness of from 110 to 150 Hv.   
     
     
         2 . The electric resistance welded steel pipe for an automotive part according to  claim 1 , wherein the chemical composition of the base metal portion comprises, in terms of % by mass, one or more elements selected from the group consisting of:
 from 0.0005 to 0.0050% of Ca,   from 0.0005 to 0.0050% of Mg,   from 0.0005 to 0.0050% of REM,   from 0.01 to 0.50% of Cr,   from 0.01 to 0.50% of Ni,   from 0.01 to 0.50% of Cu,   from 0.01 to 0.10% of Nb,   from 0.01 to 0.50% of Mo, and   from 0.01 to 0.20% of V.   
     
     
         3 . The electric resistance welded steel pipe for an automotive part according to  claim 1 , wherein the electric resistance welded steel pipe has a hardness of from 650 to 800 Hv, in a case in which the steel pipe is subjected to quenching under conditions of a heating temperature of 900° C., a heating time of one minute, a cooling rate after heating of 30° C./s, and a cooling attainment temperature at the cooling rate, within a range of from 50° C. to 0° C. 
     
     
         4 . A method of producing an automotive part, the method comprising subjecting the electric resistance welded steel pipe for an automotive part according to  claim 1  to cold working and quenching, in this order, to obtain the automotive part. 
     
     
         5 . A method of producing an automotive part, the method comprising subjecting the electric resistance welded steel pipe for an automotive part according to  claim 3  to cold working and quenching, in this order, to obtain the automotive part. 
     
     
         6 . An electric resistance welded steel pipe for an automotive part, the pipe comprising a base metal portion and an electric resistance welded portion,
 wherein the base metal portion has a chemical composition comprising, in terms of % by mass:   from 0.42 to 0.48% of C,   from 0.01 to 0.20% of Si,   from 0.10 to 0.70% of Mn,   from 0 to 0.030% of P,   from 0 to 0.030% of S,   from 0.005 to 0.050% of Al,   from 0.005 to 0.040% of Ti,   from 0.0005 to 0.0050% of B,   from 0 to 0.005% of N,   from 0 to 0.005% of O,   from 0 to 0.0050% of Ca,   from 0 to 0.0050% of Mg,   from 0 to 0.0050% of REM,   from 0 to 0.50% of Cr,   from 0 to 0.50% of Ni,   from 0 to 0.50% of Cu,   from 0 to 0.10% of Nb,   from 0 to 0.50% of Mo,   from 0 to 0.20% of V, and   a balance comprising Fe and impurities,   wherein a steel structure of the base metal portion is a ferrite-pearlite mixed structure, and   wherein the base metal portion has a hardness of from 110 to 150 Hv.   
     
     
         7 . The electric resistance welded steel pipe for an automotive part according to  claim 6 , wherein the chemical composition of the base metal portion comprises, in terms of % by mass, one or more elements selected from the group consisting of:
 from 0.0005 to 0.0050% of Ca,   from 0.0005 to 0.0050% of Mg,   from 0.0005 to 0.0050% of REM,   from 0.01 to 0.50% of Cr,   from 0.01 to 0.50% of Ni,   from 0.01 to 0.50% of Cu,   from 0.01 to 0.10% of Nb,   from 0.01 to 0.50% of Mo, and   from 0.01 to 0.20% of V.   
     
     
         8 . The electric resistance welded steel pipe for an automotive part according to  claim 6 , wherein the electric resistance welded steel pipe has a hardness of from 650 to 800 Hv, in a case in which the steel pipe is subjected to quenching under conditions of a heating temperature of 900° C., a heating time of one minute, a cooling rate after heating of 30° C./s, and a cooling attainment temperature at the cooling rate, within a range of from 50° C. to 0° C. 
     
     
         9 . A method of producing an automotive part, the method comprising subjecting the electric resistance welded steel pipe for an automotive part according to  claim 6  to cold working and quenching, in this order, to obtain the automotive part. 
     
     
         10 . A method of producing an automotive part, the method comprising subjecting the electric resistance welded steel pipe for an automotive part according to  claim 8  to cold working and quenching, in this order, to obtain the automotive part.