Offshore jack-up platform rack steel must exhibit high strength and toughness as well as excellent welding properties.A high-quality large ingot is a prerequisite for obtaining a high-performance rough part.The electroslag remelting withdrawing(ESRW)technology using a T-shaped mold and bifilar mode was introduced to replace casting technology.Numerical simulation of the ESRW process was performed to determine the distribution of the temperature and velocity fields and to determine the optimum process for producing rack steels.Several A514 Qslab ingots with dimensions of 0.32m×1.40m×4.00 m were produced using ESRW technology in an industrial plant.The industrial test indicated that slab ingots produced by the ESRW method exhibited uniform chemical compositions and compact macrostructures.A 115.4mm thick plate was produced from the rough ingot after 11 rolling passes.Samples were obtained from different positions in the steel plate to test the mechanical performance and examine the microstructure,and the results revealed that the properties of the steel plate satisfied ASTM standards.The ESRW process improved the tensile strength and toughness of the slab ingot,enabling significant improvements in the anisotropy and low temperature toughness,which are critical for the development of rack steel for offshore platforms.
Xi-min ZANGTian-yu QIUWan-ming LIXin DENGZhou-hua JIANGHua SONG
With increasing demand for large cylindrical forgings,a new technology—electroslag remelting(ESR)for direct manufacture of hollow ingots rather than solid ingots has been developed.The main features of the process include a T-shaped current supplying mould(CSM),double power supply,an ingot withdrawing system,a metal level automatic control system based on a level sensor using the electromagnetic eddy current method,and the exchange of a consumable multi-electrode.ANSYS software was used to calculate the fluid flow and heat transfer in the slag bath and metal pool of this ESR hollow ingot process with its T-shaped CSM.The mathematical model was verified by measuring the geometry of the liquid metal pool as observed in the macrostructure of650mm(external diameter)/450mm(internal diameter)hollow ingots by sulphur print method:the observed shape and depth of the slag bath were consistent with the simulated results.Simulation of the ESR process can improve understanding of the process and allow better operating parameters to be selected.
Xu CHENFu-bin LIUZhou-hua JIANGHua-bing LIXi-min ZANGXin DENG
采用电渣重熔方法生产的空心钢锭由于其独特的结构和凝固特性,具有普通钢锭无可比拟的优越性.本文以电渣重熔35CrMo材质的空心锭为研究对象,利用金相显微镜(OM)和Image-Pro Plus 6.0详细地研究了电渣重熔空心钢锭的凝固组织、夹杂物形貌等.通过与电极的对比,研究了电渣重熔工艺的优越性.结果表明:电渣重熔空心钢锭具有元素分布均匀、组织致密、夹杂物去除能力强等特点.
