摘要:
研究了Q500q钢动态连续冷却转变规律,提出了采用超快冷+层流冷却工艺试制Q500q,试制工艺为第一阶段即粗轧开轧温度≥1 050℃,粗轧阶段累计压下率≥60%,待温厚度为2.5倍成品厚度;第二阶段即精轧开轧温度830~860℃,终轧温度780~810℃;采用超快冷+层流冷却联动方式进行冷却,终冷温度630~650℃,冷却速率在15℃/s。试验钢的金相显微组织由AF+B构成,晶粒度在13级左右,试验钢的屈服强度为538~560 MPa,抗拉强度为647~668 MPa,延伸率≥21%,-40℃低温冲击韧性≥160 J,Z向断面收缩率≥75%。试验钢板具有非常优异的强韧性配比,采用此工艺生产减少了传统工艺中的热处理的工序,降低了工序生产成本,而且试制的钢板仍然能满足国家相关标准的要求。
Abstract:
After continuous cooling transformation test on Q500 q steel,a ultra-fast cooling and accelerated cooling technology had been proposed.For the new controlling rolling and cooling process,during the roughing rolling phase, start rolling temperature shall be over 1 050 ℃ and total reduction shall be greater than 60%,and the thickness of transferred bar is 2.5 times over that of finished product.For the finishing rolling phase,start rolling temperature is between 830～860 ℃and finishing rolling temperature is between 780～810 ℃.The cooling strategy of combined Ultra-fast Cooling and Accelerated Cooling System is used to achieve 630～650 ℃ of finishing cooling temperature with cooling rate of about 15 ℃/s.Microstructure observation show that microstructure of the test steel is composed of acicular ferrite and bainite,with average grain size at ASTM 13.Mechanical test results show yield strength between 538 MPa to 560 MPa,tensile strength between 538 MPa to 560 MPa,elongation≥21% and impact absorbed energy≥160 J at-40 ℃,the direction of thickness reduction of area≥75%.The tested steel has a satisfied combination of strength and toughness.
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