Abstract The numerical relation of cast iron chill characteristics (distance of chilled layer H and volume quota of ledeburite in it Q l ) with its carbon equivalent СE was investigated. This data helps forecast the evolution of the surface chilled layer forming at the casting production with different thickness from cast iron of various chemical compositions. The study focuses on the unalloyed induction-melted cast iron with eight chemical-composition variants with carbon equivalent from 3.30 up to 5.53%. From these cast irons, step-by-step castings were made with steps sizes of 10 × 60 mm and thickness of 5, 10, 20, and 40 mm. The chilled-layer distance (depth) was measured at the casting fractures and gaged on thickness of full chill zone. Ledeburite volume quota was detected by a metallographic method using the “Nexsys-Image expert pro 3” computer program. According to experimental data, when the casting thickness is 5 and 10 mm, the through (at all thickness) full chill is formed at a carbon equivalent ≤4.08% and ≤3.67%, consequently. At the castings with 20- and 40-mm thickness, the zone of full chill is absent. In this case, the chilled layer depth increases with a decrease of carbon equivalent and decreases with an increase of casting’s thickness X. The dependence of H from C E have the exponential character and can be described by the equation H = A exp(– k C E ), where A and k are empirical coefficients. Ledeburite volume quota near the contact casting surface with chiller is near 90%, but it decreases with different intensity depending on changes of carbon equivalent and casting’s thickness with an increase in the distance from the surface. By mathematical processing of the experimental data received for the 5-mm distance from the contact surface of the casting with chiller, a numerical relation Q l in casting chilled layer with value of C E can be described by the exponential dependence: Q l = 1000(7/( X + 10))exp(–C E ).

中文翻译：

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铸铁冷硬与其碳当量的关系

摘要 研究了铸铁冷硬特性（冷硬层距离H和其中莱氏体的体积定额Q l ）与其碳当量СE的数值关系。该数据有助于预测不同化学成分铸铁在铸造生产中形成的表面冷硬层的演变。该研究的重点是具有八种化学成分变体的非合金感应熔炼铸铁，碳当量从 3.30 到 5.53%。从这些铸铁中，逐步铸造出阶梯尺寸为 10 × 60 毫米和厚度为 5、10、20 和 40 毫米的铸件。在铸件断裂处测量冷硬层距离（深度）并测量全冷硬区的厚度。莱氏体体积配额是通过金相方法使用“Nexsys-Image Expert pro 3”计算机程序检测的。根据实验数据，当铸件厚度为 5 和 10 mm 时，在碳当量≤4.08% 和 3.67% 的情况下形成贯穿（在所有厚度）全冷硬。在 20 和 40 毫米厚的铸件上，完全冷硬区不存在。在这种情况下，冷硬层深度随着碳当量的减少而增加，随着铸件厚度 X 的增加而减少。 H 对 CE 的依赖性具有指数特征，可以用等式 H = A exp(– k CE )，其中 A 和 k 是经验系数。与冷却器接触的铸件表面附近的莱氏体体积定额接近 90%，但随着离表面距离的增加，随着碳当量和铸件厚度的变化，它以不同的强度减小。通过对距铸件与冷却器接触面 5 毫米距离处接收到的实验数据进行数学处理，铸件冷却层中的数值关系 Q l 与 CE 值可以用指数相关性来描述： Q l = 1000( 7/( X + 10))exp(–CE )。