| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel bar for a steering rack, which has superior impact resistance in addition to improved abrasion resistance, and prevents propagation/penetration of cracks. SOLUTION: The steel bar for the steering rack includes 0.50-0.60% C, 0.05-0.5% Si, 0.2-1.5% Mn, 0.0005-0.003% B, 0.005-0.05% Ti, 0.0005-0.1% Al, 0.002-0.02% N and 1.5% or less Cr. Besides, the quenched/tempered structure of a D/4 part is adjusted so as to satisfy the following conditions (1) to (3). (1) The total of a tempered bainite structure and a tempered martensite structure occupies 30-100% (by area percentage). (2) A reproduced pearlite structure occupies 0-50% (by area percentage). (3) The total of the tempered bainite structure, the tempered martensite structure and the reproduced pearlite structure occupies 50-100% (by area percentage). COPYRIGHT: (C)2005,JPO&NCIPI
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