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在含钒钛的低合金高强度碳锰钢的热轧状态组织中发现一种粒状组织。随着这种组织的出现,钢的冲击韧性发生很大波动,有时甚至下降到很低值。为了探明粒状组织形成的条件和原因,本工作进行了几种不同的轧制工艺试验。结果得出一系列影响因素,诸如终轧前的待温、终轧温度和变形量及冷却速度等。试验结果证明粒状组织产生的本质原因乃是具有粗化了的奥氏体晶粒的钢,受到某种程度的过冷所致。 本工作也研究了粒状组织形成机理,结果发现,粒状组织是由基体和“岛屿”两部分组成。基体是魏氏组织铁素体,而“岛屿”是被魏氏组织铁素体围挤在中间的富碳奥氏体的转变产物。 根据试验研究,提出了这种钢合理的控制轧制方案,能够保证得到高强度高塑性等预期综合机械性能。
A granular structure was found in the hot rolling microstructure of vanadium-titanium-containing low-alloy high-strength carbon-manganese steel. With the advent of this type of organization, the impact toughness of steel fluctuates greatly, sometimes even dropping to very low values. In order to identify the conditions and causes of the formation of granular tissue, this work carried out several different rolling test. The results obtained a series of influencing factors, such as the temperature before finishing rolling, finishing temperature and deformation and cooling rate. The experimental results show that the essential cause of the granular structure is that the steel with the coarsened austenite grains is subject to some degree of undercooling. This work also studied the formation mechanism of granular structure and found that granular structure is composed of matrix and “island”. The matrix is the Widmanstatten ferrite, and the “islands” are the transformation products of carbon-rich austenite surrounded by Widmanstatten ferrite. According to the experimental research, a reasonable control rolling scheme of this steel is proposed, which can ensure the expected comprehensive mechanical properties such as high strength and high ductility.