Study influence of forming process on microstructure and properties of deep hole thick wall pipe blank

Abstract. According to the demand for high strength and high toughness of deep hole thick wall pipe blank, basing on 36,000 tons of vertical extrusion machine, 3,000 tons of free forging press and 1,600 tons of radial forging machine. Using electroslag remelting to smelt Cr-Ni-Mo-V steel ingot as raw material, three forming processes were studied, including free forging and radial forging, solid extrusion and radial forging, and hollow extrusion and radial forging. The physical quantity distributions of stress, strain and strain rate in the deformation zone of billet blank in different forming processes were analyzed via numerical simulation technology. Combined with the numerical simulation results, three forming processes were carried out in engineering trial production. The trial production results show that the structure of the pipe blank produced by the hollow extrusion + radial forging process is uniform, the mechanical properties of the pipe blank at both ends of the sampling RP0.2≥1370 MPa, -40°CKV≥28.0J, the mechanical properties of the full-length cross-section of the pipe blank RP0.2≥1381 MPa, -40°CKV≥28.2 J, the full-length yield strength is 28 MPa, and the comprehensive performance level is leading in the world.