The production process of hafnium ingot is similar to that of titanium and zirconium.The hafnium isotopic isocrystal transition temperature is higher (1760℃), so thermal processing can be performed in a dense hexagonal region. There is no phase transition throughout the plastic process. Box-type electric furnace is used for forging heating. The temperature is 1100 ~ 1200℃. The holding time (min) can be half of the ingot diameter (mm). Each fire forging ratio (see alloy steel forging blank) can reach more than 4, the final forging temperature is usually not less than 850℃, forging equipment with hammer and hydraulic press can be.
The capillary tubes and bar billets are usually prepared by cladding extrusion, and the cladding material of the billets is made of low carbon steel. The sealed ladle sleeve prevents hafnium from oxidizing at high temperature and prevents the hafnium metal from sticking to the die surface. Extrusion billet is a casting or forging that has been peeled, a solid billet is used when extrusion bar, and a hollow billet is used when extrusion capillary. The billet is heated to 900 ~ 1000℃ in an electric furnace. If the billet is extruded by the light billet extrusion method, it can be heated to 1000 ~ 1100℃ in a glass bath. The lubrication condition and extrusion speed are the same as that of low carbon steel, the extrusion ratio is 6 ~ 15. A conical die is used to ensure that the ladle skin on the surface of the tube rod is intact.
Because of the difficulty in lubrication, hafnium tube bars are usually not produced by cold drawing, but by cold rolling or rotary forging with extruded capillary tubes or bar billets. The cold rolling rate between two annealing intervals is 30% ~ 50%, the elongation coefficient is 1.5 ~ 2.0, and the cold rolling rate of two passes is usually less than 20%. For thick - wall pipe, to implement multi - pass low - pressure rolling, so as not to crack the head. The cold rotary forging rate of hafnium bar between two annealing is 30% ~ 50%, and the process rate is 10% ~ 20%. If the bar is to be cold-drawn, the bar surface should be anodized or phosphated. Lubricant with molybdenum disulfide and lime and other mixed water agent as paint, dry after stretching lubrication effect is better. The processing rate of cold drawing between annealing is lower than that of cold rolling and cold rotary forging.
