What are the stages of the titanium ingot casting process
The titanium ingot melting and casting process is generally divided titanium ingot melting process.Next artical we will introduce"forging temperature of titanium".
一. Ingredients
Titanium alloy determines the proportion of alloying elements according to the following principles:
(1) Allowable fluctuation range of alloying element and impurity content and optimum composition range required for the best performance of the alloy;
(2) Melting method and number of smelting;
(3) The burning loss rate and evaporation rate of alloying elements in the vacuum waste smelting process;
(4) The way of adding alloying elements and their physical properties.
Under normal circumstances, for elements with a large burning rate and easy to volatile, the proportion of ingredients is close to the upper limit or exceeds the upper limit, and the elements that are not easy to be lost by volatilization should be prepared according to the middle limit of the required range. .
二. The pressing of the electrode block
The main requirements of consumable smelting for electrodes are:
(1) Sufficient strength;
(2) Sufficient conductivity;
(3) Straightness;
(4) The distribution of alloying elements in the electrode is reasonable;
(5) Free from moisture and pollution.
There are two types of preparation methods for monolithic electrodes: pressing (discrete pressing and horizontal pressing) and extrusion (also divided into horizontal and vertical). The pressing method is more commonly used.
The density of the electrode block is related to the raw material being pressed. Figure 8-27 shows the relationship between unit pressure and electrode density. Generally speaking, the density of the electrode block is greater than 3.2 g/cm3 to meet the melting requirements. Generally, a press with a pressure of 300 to 500 MPa is used. Group welding of electrodes
electrode assembly welding is to weld the pressed single electrode blocks into electrodes with the cross-section and length required for consumable arc smelting. In industry, argon gas shielded plasma welding, vacuum plasma welding and electron beam welding are often used. In order to prevent the inclusion of high specific gravity inclusions, argon tungsten arc welding is generally not used. The purity of argon for welding is 99.99%.
三. From the beginning of the power transmission smelting to the complete melting of the charge (except for the solid arch bridge above the molten pool) is called the charge melting stage. At the beginning of smelting, the newly added charge has a higher specific resistance, and the electrode is in direct contact with the charge. The charge is heated by the charge resistance. At this time, the input current is small but relatively stable. During this period, the resistance heat is dominant. But this period of time is not long. When the charge under the electrode melts to form three "crucible molten pools", arc heat is generated between the electrode and the "crucible molten pool" to heat the charge to gradually expand the molten pool outwards until a communicating three electrodes are formed. The "Molten Pool". During the transition from the "crucible molten pool" to the "large molten pool", due to the partial reduction of the unmelted charge, its specific resistance gradually decreases, so the charge resistance heat gradually decreases; and the arc heat between the electrode and the "crucible molten pool" The proportion is gradually increasing. After about half an hour from the start of smelting, the arc heat dominates. The aforementioned "transition period" is the unstable period of smelting high-titanium slag. One is because the resistance of the circuit through which the current passes (electrode → crucible bath → unrefined charge → crucible bath → electrode) changes with time; the other is " The solid material above the "crucible molten pool" often falls into the molten pool to cause a violent reaction to cause the slag to boil, and this phenomenon of "collapse-slag boiling" is irregular.Titanium disk.
