| 摘要 |
PURPOSE:To prevent the increase of hardness in a weld zone by adding trace amounts of Ti and N to the high strength hot rolled steel plate for wheel rims containing specific amounts of C, Si, Mn, and Al. CONSTITUTION:The high strength hot rolled steel plate consists of, by weight, 0.05-0.15% C, 0.05-0.5% Si, 1.0-1.6% Mn, 0.01-0.05% Al, 0.005-0.025% Ti, 15-60ppm N, <=0.030% P, <=0.010% S, and the balance Fe with inevitable impurities, or further 0.01-0.06% Nb or >=1 kind among 0.0005-0.01% Ca and 0.005-0.1% REM is incorporated to the above composition. By providing the hot rolled steel plate having this composition, the coarsening of austenite grains is inhibited at the welding of wheel rims and the finely dispersed TiN becomes a ferrite grain-nucleating site. Accordingly the formation of hard martensite and bainite is controlled, so that the increase of hardness in a weld zone can be prevented.
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