A Method of Manufacturing the Fine-Grained Ferrite High-Strength Steel

摘要

The alloy without adding much, even more refinement of ferrite particles was added to lower rolling reduction in the cold zone Structural steel production method that can is provided. ; This is a tensile strength in the 600 MPa-grade structural steel producing method, in weight% C: 0.05-0.2%, Si: 0.01-1.0%, Mn: 0.05-2.0%, Al: 0.005- 0.1%, Nb + Ti + V (each element alone, or two or three-element compound is added): 0.01-0.1%, N: 0.003-0.015%, P: less than 0.03%, S: less than 0.03%, the rest consists of inevitable impurities and that the river Ac ₃ ~Ac ₃ + 5 or more per minute over a temperature range of 100 heating and austenite grains three times less rapidly repeated heat treatment in a cooling rate of 20 and adjusted to below the recrystallization temperature zone of the US Ar ₃ ~Ar ₃ + 50 rolling 1 total cumulative reduction of over 15% per pass in the area amounts to more than 30% Rolling was added and include embodiments that accelerated cooling. The steel produced by this method is that the microstructure is composed of ferrite + pearlite or ferrite + bainite (second low-temperature phase microstructure), the ferrite grain size is composed of 2-7 .