Correction of thread outer diameter of titanium fasteners!
Titanium alloy materials are difficult to machine, have poor thermal conductivity, are easy to stick to tools, have a strong notch sensitivity, and will produce strong work hardening in the rolling process. In actual production, there are a series of problems in the rolling of full teeth.
First, the gap between the two thread rollers is filled by a full tooth profile during rolling. If the thread roller continues rolling, the blank material will have nowhere to flow and can only be squeezed back and forth between the thread rollers. As a result, the thread has a high surface hardening. When the hardening exceeds the material's tensile limit, cracks will occur. The thread side and bottom are hardened seriously, so cracks will occur;
Secondly, during full extrusion, each tooth of the thread roller participating in the rolling is also affected by a strong cyclic load, and the rolling energy also acts on the thread roller, which seriously reduces its life. In actual production, each pair of thread roller can only roll 3000-5000 titanium bolts, resulting in tooth top fracture. The thread roller can no longer be used, which is extremely expensive. In addition, the tooth top fracture of the thread roller has a formation process, It makes it impossible for the producer to judge the qualification of rolled thread, that is, when the rolled thread is qualified and when the rolled thread is unqualified;
Third, in the process of rolling to form the thread, both sides rise fast, which is bound to produce a fold at the top of the tooth when the thread is full. There is a fluorescent display mark on the top of the thread during flaw detection. In order to determine the depth of large defects, anatomical methods are also needed to determine whether the defects at this place exceed the standard;
Fourthly, the connection joints of modern fasteners have high fatigue life and high accuracy requirements for bolt holes. Hole wall damage is not allowed in the installation process, while the sharp thread tip is very easy to damage the hole wall.
In a word, full thread profile brings great trouble to production. It will not only increase the chance of crack generation, reduce the fatigue life of parts, but also reduce the service life of the thread roller. Moreover, it will bring unnecessary trouble to detection, and it is also easy to cause damage to the hole wall. Therefore, it is imperative to correct the thread diameter of titanium alloy fasteners.
