HOLLOW STABILIZER, AND STEEL PIPE FOR HOLLOW STABILIZERS AND METHOD OF PRODUCING THE SAME

摘要

A hollow stabilizer having an excellent fatigue property and higher strength compared to the conventional ones has a chemical composition containing 0.26% to 0.30% of C, 0.05% to 0.35% of Si, 0.5% to 1.0% of Mn, 0.05% to 1.0% of Cr, 0.005% to 0.05% of Ti, 0.0005% to 0.005% of B, and 0.0005% to 0.005% of Ca, wherein; Al, P, S, N, and O are limited to 0.08% or less, 0.05% or less, less than 0.0030%, 0.006% or less, and 0.004% or less, respectively, a remainder of the chemical composition consists of Fe and unavoidable impurities, a value of a product of the Mn content and the S content is 0.0025 or less, and a critical cooling rate Vc90 represented by a predetermined equation is 40° C./s or less; and wherein a metallic structure comprises a tempered martensite, a length of elongated MnS present at a center part in a thickness direction of the hollow stabilizer is 150 μm or less, a HRC is from 40 to 50, a thickness to outer diameter ratio is 0.14 or more, and a depth of a decarburized layer at an inner surface part is 20 μm or less from the inner surface; and a steel pipe for hollow stabilizers used as a material for the hollow stabilizer.

主权项

1. A hollow stabilizer having a chemical composition comprising, as chemical components, in terms of % by mass:
0.26% to 0.30% of C, 0.05% to 0.35% of Si, 0.5% to 1.0% of Mn, 0.05% to 1.0% of Cr, 0.005% to 0.05% of Ti, 0.0005% to 0.005% of B, and 0.0005% to 0.005% of Ca, wherein: Al, P, S, N, and O are limited to 0.08% or less, 0.05% or less, less than 0.0030%, 0.006% or less, and 0.004% or less, respectively, a remainder of the chemical composition consists of Fe and unavoidable impurities, a value of a product of the Mn content and the S content is 0.0025 or less, and a critical cooling rate Vc90 represented by the following Equation (1) is 40° C./s or less:
log Vc90=2.94−0.75β  Equation (1):wherein 13=2.7C+0.4Si+Mn+0.8Cr; and wherein: a metallic structure comprises a tempered martensite, a length of elongated MnS present at a center part in a thickness direction of the hollow stabilizer is 150 μm or less, a Rockwell C hardness (HRC) is from 40 to 50, a wall thickness/outer diameter ratio is 0.14 or more, and a depth of a decarburized layer at an inner surface part of the hollow stabilizer is 20 μm or less from the inner surface.