Electric-resistance-welded steel pipe or tube for hollow stabilizer and method of manufacturing same
Provided is an electric-resistance-welded steel pipe or tube for hollow stabilizer excellent in corrosion fatigue resistance having: a chemical composition containing, in mass %, C: 0.15% or more and less than 0.20%, Si: 0.1% or more and 1.0% or less, Mn: 0.1% or more and 2.0% or less, P: 0.1% or less, S: 0.01% or less, Al: 0.01% or more and 0.10% or less, Ti: more than 0.05% and 0.1% or less, B: 0.0005% or more and 0.005% or less, Ca: 0.0001% or more and 0.0050% or less, and N: 0.0050% or less, with the balance being Fe and inevitable impurities; and a microstructure containing TiS and MnS particles which each have a particle size of 10 μm or more, the TiS and MnS particles having a cleanliness of 0% or more and 0.1% or less as measured by a point counting method according to JIS G 0555.
1. An electric-resistance-welded steel pipe or tube for a hollow stabilizer comprising:
a chemical composition containing, in mass %,
C: 0.15% or more and 0.19% or less,
Si: 0.1% or more and 1.0% or less,
Mn: 0.1% or more and 2.0% or less,
P: 0.1% or less,
S: 0.01% or less,
Al: 0.01% or more and 0.10% or less,
Ti: more than 0.05% and 0.1% or less,
B: 0.0005% or more and 0.005% or less,
Ca: 0.0001% or more and 0.0050% or less, and
N: 0.0050% or less, with the balance being Fe and inevitable impurities; and
a microstructure in which a cleanliness with respect to TiS particles with a particle size of 10 μm or more and a cleanliness with respect to MnS particles with a particle size of 10 μm or more are 0% or more and 0.1% or less, respectively, the cleanliness being measured by a point counting method according to JIS G 0555.
2. The electric-resistance-welded steel pipe or tube for a hollow stabilizer according to claim 1 , wherein the chemical composition further contains, in mass %, at least one selected from the group consisting of
Cu: 1% or less,
Ni: 1% or less,
Nb: 0.05% or less,
W: 0.05% or less,
V: 0.5% or less, and
REM: 0.02% or less.
3. A method of manufacturing the electric-resistance-welded steel pipe or tube for a hollow stabilizer according to claim 1 , comprising:
cold forming a steel plate having the chemical composition into an open pipe or tube having an approximately cylindrical shape;
subjecting the open pipe or tube to electric resistance welding with its widthwise ends butted against each other to obtain an electric-resistance-welded steel pipe or tube;
heating the electric-resistance-welded steel pipe or tube to a heating temperature of 850° C. or higher and 1000° C. or lower; and
subjecting the heated electric-resistance-welded steel pipe or tube to hot-diameter-reducing rolling under a set of conditions including a rolling temperature of 650° C. or higher and a cumulative diameter reducing ratio of 30% or more and 90% or less.
4. A method of manufacturing the electric-resistance-welded steel pipe or tube for a hollow stabilizer according to claim 2 , comprising:
cold forming a steel plate having the chemical composition into an open pipe or tube having an approximately cylindrical shape;
subjecting the open pipe or tube to electric resistance welding with its widthwise ends butted against each other to obtain an electric-resistance-welded steel pipe or tube;
heating the electric-resistance-welded steel pipe or tube to a heating temperature of 850° C. or higher and 1000° C. or lower; and
subjecting the heated electric-resistance-welded steel pipe or tube to hot-diameter-reducing rolling under a set of conditions including a rolling temperature of 650° C. or higher and a cumulative diameter reducing ratio of 30% or more and 90% or less.