After rolling deformation, the lattice of titanium welded pipe is distorted, and a large number of fast traps and dislocations occur in the internal lattice, which makes the internal energy of titanium material increase and it is in metastable state. In order to restore plasticity, obtain stable fine grain structure and uniform mechanical properties, titanium after rolling need recrystallization annealing, annealing treatment can remove the internal stress of titanium plate, obtain no distortion grain structure, and titanium properties, so annealing is a key process affecting the quality of finished products. The annealing of titanium materials in Kunming Iron and Steel Co., LTD has been relying on the annealing of all hydrogen hood furnace in plate and strip plant. The heat is generated by gas + air combustion, and argon gas is fed into the furnace through the original hydrogen pipeline. Due to the active chemical characteristics of titanium, it is easy to react with H, N and other elements in the air at high temperature to form an oxide layer, which deteriorates the physical and chemical properties. In addition to the increase in hardness and brittleness and the decrease in plasticity and elasticity, the adsorption of industrial pure titanium at high temperature is also strong. The surface residue after cold rolling, carbide and dust in the annealing temperature atmosphere may be adsorbed to the surface, forming annealing black spots. The surface quality of titanium coil is affected. With the development of titanium industry to the direction of excellent products, higher requirements are put forward for equipment performance, so our company introduced excellent annealing furnace, titanium welded pipe annealing treatment.
Titanium annealing production process:
Charging → Connecting cooling water with inner cover → locking inner cover → vacuum-pumping → charging protective gas → pressure maintaining → energizing and heating up → heat preservation → lifting heating cover → closing cooling cover → wind cooling → coming out temperature → lifting cooling cover → pressure relief → locking release → disconnecting cooling water → lifting inner cover → coming out operation.
The important link in the above process is vacuumizing → filling with protective gas → maintaining pressure → heating with electricity -- insulation. Vacuumizing is to prepare for filling with protective gas, reduce the replacement time of protective gas and gas consumption, maintain a certain forward pressure in the furnace (20-40kPa), and ensure that the oxygen content in the furnace is below 5ppm, that is, it is carried out in an oxygen-free environment. The electric heating makes the temperature in the furnace rise and keep the heat according to the temperature curve, so as to meet the annealing requirements of titanium welded pipe.
