Bending is a process of combining plastic and elastic deformation. It is the most common molding method for manufacturing equipment: poetry equipment. When bending, the amount of springback must be considered. The bending angle of the money material can generally be greater than 90 °, but it must meet the minimum bending radius requirement. Titanium tubes with a diameter of less than 50mm can be cold bent. After cold bending, it is better to perform stress relief annealing treatment. Titanium tube hot bending is divided into pulling bending and pushing bending according to the force. The heating temperature is generally 177 ~ 350 (the titanium alloy can be heated to 427T). At this time, the yield strength T is reduced by 25% ~ 50%, the plasticity is good, the rebound angle is small, and the gas pollution is also small.
Second, stamping forming
Titanium sheet and titanium alloy stamping is relatively difficult, and its bending radius is larger than that of steel 2 commonly used non-ferrous metals. The stamping forming methods used in China are: cold forming: hot forming and hot straightening after preforming.
Cold forming is only used for workpieces with thin walls, small deformation, large bending radius, and low size requirements. When the deformation of cold forming is large, the methods of separate stamping and annealing between processes can be used. After cold stamping, final annealing is required; in addition to residual stress.
Complex shape and large deformation of titanium plate and titanium alloy workpiece can be stamped by Nu I. When forming at a lower temperature, the heating temperature is 200-350X; the amount of deformation should be up to 40%; when forming at a high temperature, the heating temperature can be up to 600-800 ° C, which is suitable for thicker slabs with larger amounts of deformation and forming dimensions Larger workpieces are formed. There are three main heating methods: heating the mold; heating the wool E; heating the rough, and appropriately heating the mold at the same time. 3 After the thermoforming, the titanium workpiece should be subjected to surface treatment such as sand blasting and pickling to eliminate the scale and pollution layer.
After pre-forming, heat straightening refers to the conventional stamping to make preforms, and then heating and straightening on special machine tools or special equipment to eliminate residual stress and springback, so that the two pieces reach the required shape and size.
Spin forming combines the technical characteristics of forging, extrusion, stretching, bending, ring rolling, and lateral rolling. The spin-forming process has the characteristics of good deformation conditions, high material utilization (20% -50% material saving), high surface finish and small size difference.
Fourth, expansion joint
Expansion joints are widely used in tube-to-plate combination, which is a mechanical connection that achieves tightness and tightness by deforming the tube and the tube plate. Expansion connection is an important second order for the manufacture of tubular heat exchangers. When the titanium tube is connected to the titanium tube plate, the degree of expansion (inner diameter expansion rate) should be 1% to 6%. When the degree of expansion is expressed as the wall thinning rate, it can reach 5% ~ can be divided according to the expansion method For mechanical expansion, flexible expansion and explosion expansion.