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本文叙述热轧条件对于几种碳素钢的奥氏体晶粒度和其机械性能的影响;同时对于压下的积累作用以及奥氏体晶粒大小对于热轧特征如塑性、变形阻力和冲击靱性的影响亦作了探讨。研究结果示:原始奥氏体晶粒较粗大的轧件,除了随冷却速度的降低而晶粒变粗的一般趋势外,沿出现了不均匀的长晶粒、带状组织和魏氏组织;合碳较高(0.66%C)的钢材则随着冷却速度的不同而出现了索氏体、珠光体和铁素体。随着奥氏体晶粒的加大,屈伏强度σ_s和低温(-20℃)冲击靱性α_k有显著的降低。轧制后的冷却速度(同一的奥氏体晶粒度)对于断面减缩率ψ的影响不大,但是随着冷却速度的提高,σ_s、σ_b和高低温冲击靱性a_k都有所提高。在1050℃轧制不同含碳量的钢材时,均出现了发生粗大奥氏体晶粒的临界加工量区域(介于0—10%之间),不过在同一热轧条件和临界加工量范围内,从各钢种获得的最大奥氏体晶粒度有相当大的差别,其中以40号钢有最小的晶粒度(约21/2号),而钢三有最大的晶粒度(约0号),保温时间对40号钢的晶粒度的影响最小,而对钢三的晶粒席的影响最大。在各钢种中,压下的积累均相当显著,而影响轧件的奥氏体晶粒度以最后一次的压下量起较大的作用。如果最后一次的压下量在临界数值内(钢三为5—15%之间),则不但没有积累的作用,而且晶粒反而会变粗,因此最后一次的压下量应尽可能避开临界数值。异常粗大的原始奥氏体晶粒随着加工量的增大而逐渐变细,但是细小的原始奥氏体晶粒轧制后出现了明显的临界加工量范围,即在压下量—保温时间—奥氏体晶粒度的图表上出现了高峰(钢三则介于5—15%压下率之间)。随着保温时间的增长,此高峰的面积亦加大。原始奥氏体晶粒度为0号及8号的二种钢三钢材,其热加工特性无显著的差别。其在900℃时的冲击靱性相差仅8%,其变形阻力相差3%,其塑性亦仅相差2%。
This article describes the effect of hot rolling conditions on the austenite grain size and mechanical properties of several carbon steels; the simultaneous effect on the reduction in pressure and the effect of austenite grain size on hot rolling characteristics such as ductility, deformation resistance and impact The impact of sex is also explored. The research results show that, in addition to the general trend of coarse grains with coarse austenite grains, along with the decrease of the cooling rate, non-uniform long grains, ribbons and Westem organization appear along the rolling line. Steel with higher carbon (0.66% C) shows sorbite, pearlite and ferrite with different cooling rates. With the increase of austenite grain size, the flexural strength σ_s and the low temperature (-20 ℃) impact 靱 sex α_k significantly reduced. The cooling rate after rolling (the same austenite grain size) has little effect on the reduction of area ψ, but σ_s, σ_b and high and low temperature impact properties a_k increase with the increase of cooling rate. When the steel with different carbon content is rolled at 1050 ℃, the critical processing area (between 0-10%) of coarse austenite grains appears, but in the same hot rolling condition and the critical processing capacity range , The maximum austenite grain size obtained from the steels is quite different, with the 40 steel having the smallest grain size (about 21/2) and the steels having the largest grain size ( About 0), holding time on the 40 steel grain size of the smallest impact on the grain of the three seats of the greatest impact. In each steel type, the accumulation of pressure is quite significant, and the austenite grain size that affects the rolling material plays a greater role in the last reduction. If the last reduction is within the critical value (steel between 5-15%), then not only does not accumulate the role of the grain but instead will be thick, so the last reduction should be avoided as far as possible Critical value. The abnormally coarse original austenite grains taper with the increase of the processing volume, but the obvious critical processing capacity range appears after the rolling of the fine primary austenite grains, that is, when the rolling reduction-holding time - Peaks appear on the graph of austenite grain size (steel between 5-15% reduction). As the holding time increases, the area of this peak also increases. The original austenite grain size of 0 and 8 of the two steel three steel, its thermal processing characteristics no significant difference. Its impact at 900 â "ƒ when 相 difference of only 8%, the deformation resistance difference of 3%, the plastic is only a difference of 2%.