The tube type annealing furnace adopts four zone temperature control, silicon carbide rod or spiral resistance wire heating, and the heating temperature can reach 1150 ℃. The furnace core tube is made of high temperature resistant stainless steel 310S tube, which is arranged in a single layer along the length of the furnace. The annealed tubes pass through the furnace core tube and are heated, and the ammonia decomposition atmosphere is sent into the furnace core tube at the same time. The furnace body is of split structure, easy to maintain, good sealing, less heat loss and good insulation.

In order to cool the annealed stainless steel capillary rapidly, a water cooling box is set up in the annealing furnace, and stainless steel tubes are installed inside as cooling tubes. Through cooling, the annealed tubes can obtain supersaturated stainless steel solid solution, which can meet the hardness and brightness required by the process. A special winding unit is set at the rear of the water cooling box. After annealing, the tube can be reeled in a disc, and a hydrogen protection input device is set inside to prevent the oxidation of the inner hole of the tube. At the same time, hydrogen is sent into the inner hole of the tube for protection, so as to ensure the inner and outer brightness of the annealed tube.