【作者】 王晓文；

【导师】 刘相华； 赵德文；

【作者基本信息】 东北大学 ， 材料加工工程， 2008， 博士

【摘要】 随着我国城市化进程的加速,未来钢筋的生产和消费量都将会大大提高。因而低成本高性能钢筋的研究与开发显得尤为重要。基于此,本文通过实验室和现场试验研究开发了低成本高性能钢筋的生产工艺并进行了现场工业大生产。论文主要内容如下：(1)通过实验室热模拟实验确定了新型钢在不同冷却速度下的生成相和奥氏体未再结晶区温度范围。实验表明在现场条件下,实验钢筋吐丝后单纯采用风冷时得到钢筋的组织全部为铁素体+珠光体,未再结晶区温度范围大约为770～950℃。利用单道次压缩实验,建立了实验钢的变形抗力模型并对其高温变形的动态行为进行了研究。研究表明在现场工业试验条件下,轧件在轧制过程中不会发生动态再结晶。采用双道次压缩实验,研究了实验钢不同热变形条件下的软化率。研究结果发现在现场控温轧制试验条件下,轧件在精轧阶段不会发生静态再结晶。(2)通过现场工业试验确定了不同控温轧制措施对盘圆螺纹钢筋性能的影响,制定了现场最佳控温轧制工艺。结合控温轧制和喷雾冷却,通过成分微调,成功实现了用普碳钢轧制400MPa级低成本高性能盘圆螺纹钢筋。(3)利用平面变形法对萍钢棒材厂轧制低成本高性能Φ25mm棒材时轧件在中轧和精轧阶段的温度进行了计算。计算结果表明轧件在中轧阶段轧制过程中就产生了温升。当入中轧温度控制在950℃,终轧速度控制在11m/s时,轧件在中轧阶段温升计算值为44.7℃,精轧阶段温升计算值为65℃,计算值与现场实测值吻合较好。(4)参照低成本高性能盘圆螺纹钢筋轧制工艺,提出了一种新的生产低成本高性能棒材的工艺。即通过优化轧后控制冷却工艺将奥氏体再结晶区轧制过程中形成的细的、强烈硬化的、具有大量缺陷的奥氏体晶粒快速冷却到相变温度附近后空冷,从而抑制其晶粒长大并使其转变为晶粒适度细化的铁素体+珠光体。钢筋表面不会生成回火组织,在提高钢筋强度的同时保证其强屈比。(5)利用ANSYS有限元模拟了Φ25mm棒材轧后不同穿水冷却条件下的温右时,棒材表面会生成闭环回火组织,影响其性能。要想在棒材表面不产生回火组织的前提下尽可能提高其性能,轧后最好采用两段水冷,钢筋回火后温度控制在800℃左右。(6)利用闪光对焊技术对新工艺生产的棒材进行了焊接试验,试验结果表明,采用新工艺生产的低成本高性能棒材焊接性能良好。Φ12mm试验钢时效20天后性能检测表明新工艺生产的钢筋基本不存在时效性。更多还原

【Abstract】 With the acceleration of our country’s urbanization process,the amount of steel bar’s production and consumption will increase greatly in the future.Thus,it’s very important to research and develop high-performance steel bar with low cost.In this article,a production technology of high-performance steel bar with low cost was developed based on the results of experimental and industrial investigation. Industrial trials were carried out in field conditions.The main works are shown as following:(1)New steel’s microstructure in different cooling rate and temperature range of austenite in non recrystallization zone were determined through thermal-mechanical simulation. The experimental results indicate that experimental steel bar’s microstructure is consisted of ferrite and pearlite using forced air cooling after rolling and its temperature range in non recrystallization zone is 770～950℃in field conditions.The experimental steel’s model of resistance of deformation and dynamic behavior during high-temperature deformation were investigated using single hit compression test.The research indicates that the dynamical recrystallization of austenite doesn’t occur at present industrial conditions.The experimental steel’s softening fraction under different thermal deformation conditions was determined through double-hit compression tests.The research indicates that the static recrystallization of austenite doesn’t occur in finishing area at present industrial conditions.(2)Through industrial field tests,the influence of different controlled temperature rolling means on the properties of hot rolled ribbed wire rods was determined and the best controlled temperature rolling technology was established. Utilizing controlled temperature rolling and spray cooling combined with adjusting billet’s chemical composition,400MPa high-performance hot rolled ribbed wire rods with low cost using plain carbon steel was produced successfully. (3)During rolling 025mm high-performance bar with low cost in Pingxiang Iron and Steel Corporation, the stock’s temperature in intermediate and finishing mill group was calculated using plane deformation method.The calculation results show that the stock’s temperature increases in intermediate mill.When the stock’s temperature in the entry of intermediate mill unit is controlled in 950℃and finishing rolling speed is controlled in 11m/s,the stock’s theoretical temperature rise in intermediate and finishing mill unit is 44.7℃and 65℃respectively.(4)A new technology of producing high-performance steel bar with low cost was proposed according to the technology of producing high-performance hot rolled ribbed wire rods.The mechanism of new technology is cooling the fine and strongly hardened austenitic grain which is formed in the rolling process of austenite recrystallization zone and consisted of lots of lattice defects to phase transition temperature with optimized controlled cooling technology. Thus the austenite grain’s growth trend is restrained and changes to ferrite with proper grain size and pearlite in the following air cooling process.There is no tempered microstructure in the steel bar’s surface.The steel bar’s strength increases and the ratio of tensile strength to yield strength doesn’t decrease.(5) 025mm steel bar’s temperature fields with different water cooling conditions after rolling was simulated by finite element method.The experimental results show that close-loop tempered microstructure will occur in the steel bar’s surface and influence its performance when three segment water cooling is adopted after rolling and steel bar’s temper temperature in the surface is about 660℃.In order to improve steel bar’s performance under the condition of no close-loop tempered microstructure occurring in steel bar’s surface as possible, two segment water cooling should be adopted and steel bar’s temper temperature should be about 800℃.(6) Welding performance of the steel bar produced by new technology was tested by flash butt welding technique.The experimental results show that the welding performance of high-performance steel bar with low cost produced by new technology is well.Φ12mm steel bar’s test results of mechanical properties after aging twenty days show that there is no aging problem in the steel bar produced by new technology.更多还原