The process of titanium ingot melting and casting is generally divided into three stages: first, ingredient preparation, second, electrode binding, and third, melting and casting.

1、 Ingredients

Titanium alloy determines the proportion of alloying elements according to the following principles:

(1) The allowable fluctuation range of alloy element and impurity content and the optimal composition range required for the optimal performance of the alloy;

(2) Melting method and smelting frequency;

(3) The burning loss rate and evaporation rate of alloy elements during vacuum white melting process;

(4) The addition method and physical properties of alloy elements.

In general, elements with high burning loss rate and easy volatilization are batched at a ratio close to or exceeding the upper limit, while elements that are not prone to volatilization loss are batched at the middle limit of the required range..

2、 Pressing of electrode blocks

The main requirements for electrodes in consumable melting are:

(1) Adequate strength;

(2) Adequate conductivity;

(3) Straightness;

(4) The distribution of alloy elements in the electrode is reasonable;

(5) Not affected by dampness or pollution.

There are two types of preparation methods for single electrode: pressing (also known as discrete pressing and transverse pressing) and extrusion (also known as horizontal and vertical pressing), with the most commonly used method being pressing.

The density of the electrode block is related to the raw material being pressed. Figures 8-27 show the relationship between unit pressure and electrode density. Generally speaking, electrode blocks with a density greater than 3.2 g/cm3 can meet the melting requirements. Generally, a press with a pressure of 300-500MPa is used.

The assembly welding of electrodes is the welding of pressed single electrode blocks into electrodes with the required cross-section and length for consumable arc melting. In industry, argon shielded plasma welding, vacuum plasma welding, and electron beam welding are commonly used. To prevent the inclusion of high density inclusions, tungsten argon arc welding is generally not used. The purity of argon gas used for welding is 99.99%.

3、 The stage of furnace material melting refers to the period from the start of electric melting to the complete melting of the furnace material (except for the solid arch bridge above the melting pool). At the beginning of the smelting process, the newly added furnace material has a higher specific resistance. The electrodes come into direct contact with the furnace material and rely on the furnace material resistance to heat the furnace material. At this time, although the input current is small, it is relatively stable. During this period, resistance heat dominates. But this period of time is not long. When the furnace material below the electrode melts to form three "crucible melting pools", an arc heat is generated between the electrode and the "crucible melting pool" to heat the furnace material and gradually expand the melting pool outward, until a "large melting pool" is formed that communicates with the three electrodes. During the transition period from the "crucible melting pool" to the "large melting pool", due to the reduction of the unmelted part of the furnace material, its specific resistance gradually decreases, so the resistance heat of the furnace material gradually decreases; The proportion of arc heat generated between the electrode and the "crucible melt pool" gradually increases. After about half an hour from the start of smelting, arc heat dominates. The above "transition period" is an unstable period for smelting high titanium slag. Firstly, it is because the resistance of the circuit through which the current passes (electrode → crucible melt pool → raw material → crucible melt pool → electrode) changes over time; The second is that the solid material above the "crucible melt pool" often falls into the melt pool, causing intense reactions and slag boiling, and this phenomenon of "material collapse slag boiling" is irregular.