Steel with Small Variation of Strength to Plate Thickness Change and Method for Manufacturing the Steel

摘要

The present invention relates to a method intensity difference is less steel and its manufacture according to the thickness variation of the steel sheet, the present invention is the difference in magnitude in accordance with the change in thickness of the steel plate without carrying out a special heat treatment to provide a reduced steel dramatically, that there is a purpose. ; The invention C: 0.003 ~ 0.035wt%, Si: less than 0.8wt%, Mn: 1.4 ~ 3.0wt%, B: 0.0005 ~ 0.0035wt%, Ti: 0.005 ~ 0.05wt%, N: 0.005wt% or less, Mo : 0.05 ~ 0.5wt%, Sol-Al: 0.005 ~ 0.1wt%, the remainder being Fe and other unavoidable impurities in the composition; The tissue is the polygonal ferrite, pearlite and martensite and the sum is 5% or less of volume percentage, and the other is quasi-polygonal ferrite, granular bays and bay mixed structure of ferrite age tick tick age and ferrite; And to be the A value is smaller than 21.7, the strength differences between the thickness variation of the steel material and a method of manufacturing the formula (1) as a base. ; [Expression 1] ; The thickness t ₁ Steel strength (Mpa) - thickness t ₂ Steel strength (Mpa) AX = ln (t ₂ / t ₁₎; (Wherein t ₁ and t ₂ is the thickness of the steel plate t ₂ t ₁ Im) ; Thickness, strength difference, toughness, strength, manganese