Tantalum tube has various processing methods, including extrusion tube, rolling tube, tensile tube, spinning tube and welding tube.
The main preparation methods of tantalum tube blank include extrusion, plate spinning and plate and strip welding. The production methods of finished pipe mainly include rolling, drawing and spinning.
1. Billet extrusion
Extrusion is a kind of pressure processing method that puts pressure on one end of the billet placed in the container to make it pass through the die hole to achieve plastic deformation. There are two basic ways to extrude: forward and backward. Due to the limitation of the strength of the hollow extruder, the maximum circumflex size of the backward extruder is more than half that of the forward extruder. In addition, the reverse extrusion cycle is long, the surface quality of products is not good.
2. Tantalum rolling tube
The production of cold rolled tube has developed rapidly at home and abroad. In addition to the two-roll cycle cold rolling mill, there are multi-roll cycle cold rolling mill, continuous cold rolling mill planetary cold rolling mill and various types of cold rolling mill. Tantalum tube rolling is generally cold rolling, such as two - roll cold rolling mill and multi - roll cold rolling mill. The main characteristics of the two-roll cold rolling tube are: large deformation, up to 90% stress state is good, can produce diameter and wall thickness ratio (DS) of 60-100 thin-walled tube; The products have high mechanical properties, good surface quality and accurate geometric dimensions. Its disadvantages are complex equipment structure, large investment, low productivity.
The main characteristics of multi-roll cold rolling tube are: because more than 3 small diameter rollers are used, the metal pressure on the roller is relatively reduced, the elastic deformation of the roller and mandrel is small, so it can produce high-precision thin-wall tube with large diameter (D/S up to 150~250). Due to uniform deformation, the surface of the tube produced is smooth and clean.
3. Tantalum stretch pipe
Drawing is also one of the main methods to produce tantalum tubes. There are several basic methods for the stretching of pipe:
1) empty pull. When the tube is stretched, the core is not placed inside the tube blank, and the outer diameter shrinks after passing through the mold, and the tube wall will change slightly.
2) long core bar stretching. A long core bar is set in the tube billet, and the core bar passes through the mold along with the tube billet during stretching to achieve diameter reduction and wall reduction.
3) stretch fixed mandrel. In the process of drawing, the die hole is used to reduce the diameter and wall of the fixed tube blank with core head.
4) flow core stretching. During stretching, the force balance established by the unique shape of the mandrel stabilizes it in the deformation zone.
5) pipe jacking. The core rod is set into the tube billet with bottom, and the tube billet and core rod are pushed out from the die hole during operation, so as to process the outer diameter and inner diameter of the tube billet.
6) expansion method. The diameter increases and the wall thickness and length decrease.
4. Tube heat treatment
Tube heat treatment includes stress relief annealing and recrystallization annealing (full annealing). According to the role of annealing in the process, it can be divided into blank annealing, intermediate annealing and finished annealing. For tantalum niobium tubes, stress relief annealing is generally used for finished products annealing and recrystallization annealing is generally used for intermediate annealing.