The Casting Process Improvement On Nickel Based Slab Billet And Expriment Research

Nickel alloy sheet is widely used in corrosive environment of marine oil and gas,chemical production and turbine equipment, which applied as main or valuablecomponents, with a long-term and huge demand on medium plate and high-strength steel.However，the traditional nickel alloy slab process, continuous casting and mould casting,seriously restricted the economic benefit of enterprises, and can not meet the growingdemand for corrosion resistant medium plate and high-strength. Based on the equipmentand product experience of Qinhuangdao Nickel Industry Ltd. Co, a design of optimizationis approved to improve productivity and reduce cost and production cycle.With the use of2t vacuum induction smelter and2t electroslag remeltingfurnace(single transformer, two arms and five station), the optimization is respectivelydesigned as a set of mould casting system with the size of1315mm×1050mm×(156~175)mm and a set of electroslag remelting scheme with the size of250mm×80mm×700mm.The core ideas of mould scheme is to design a system which make the temperature ofthe top slab higher than the bottle after pouring, and make the cooling rate of the top fasterthan the bottle. In this way, the liquid shrinkage could be feed by the less strip feeder,meanwhile, the defect caused by solidification shrinkage and the solid shrinkage can bewrapped in the slab internal. Accompanied by the side system and the peculiar mouldcasting system, the defect could be tiny and disperse inside the slab, which can be bond inthe following large deformation hot rolling process. In order to optimize the designparameters, we adjust the side gating diameters and position, slab thickness and mouldthickness by the use of hotspot criteria and Niyama criteria in the numerical simulation.The size of electroslag remelting billet is250mm×80mm×700mm.The core ideas ofelectroslag remelting slab is the use of plate shape crystallizer, which could provide slabingot to the following hot rolling directly without forging. The main part of the scheme isdesign about slab crystallizer, electrical control parameters and slag system, with whichthe electroslag remelting system is built.Base on the mould casting scheme, we design a similar slab pilot plant trial with the size of300mm×238mm×(35~40) mm, which is0.29times than the original ones each.The NDT(Non-destructive Test) and slice analysis help confirm the strip feeder isfeasibility, and the side gating system parameters is suitable, which proves the particularmould casting system is availability and more efficient than the current one. Take a samplewith inner defect, whose size is120mm×40mm×22mm. By the process of1100℃and85%reduction ratio hot rolling, the thickness of the sample turn to3.5mm.After the sameheat treatment with the traditional hot rolling sample, we respectively test the Taferpolarization curve of series of sections on different depth from the surface and analysis thecorrosion resisting property by SEM.