Research on extrusion process of 316LN stainless rectangle thick-wall tube used in ITER top and bottom correction coils

Rectangular shaped cross-section 316LN thick-wall tube, obtained from round forged billet by extrusion process, is used in the manufacture of the ITER Top and Bottom Correction Coil cases. The hot working properties of 316LN stainless steel are studied by compression test, stress-strain curves and microstructures of samples at high temperature are gotten. FEM (Finite Element Method) simulation is adopted to analyze metal flow characteristics and optimize design of extrusion die in extrusion process. By billet forging and machining, extrusion die designing and manufacturing, ring-oven preheating, induction heating, glass lubrication and deformation designing, 316LN stainless steel rectangle thick-wall tubes are fabricated by 60 MN horizontal extruder, the measurement and properties of the products all accord with the design target, these products are applied as structural support parts in ITER project successfully.