1. A gas, chiefly hydrogen and oxygen, that dissolves in copper. DIATOMIC molecular gases can not be dissolved directly in metal melts. Gas Dissolution Process is: adsorbed on the metal surface-dissociated into a single gas atoms-diffusion into the metal lattice, the formation of solid solutions and compounds. Hydrogen and oxygen are both harmful elements in copper, which can not only reduce the performance of copper, but also lead to "hydrogen disease" . There is a certain oxygen content in Copper Ingot, but if excess oxygen or hydrogen is dissolved in the Ingot, it will be the main cause of casting quality accident. Therefore, in smelting copper, measures must be taken to block the source of gas, to avoid or minimize air, water, oil and all kinds of pollutants and melt contact. Gas dissolution process is to eliminate the "adsorption" of this condition, so that the dissolution process can not be established. Under certain adsorption conditions, the degree of gas solubility in metal mainly depends on: 

(1) the binding force between gas and metal. The gas, which has the smallest radius of the hydrogen atom, is an extremely reactive element that can be dissolved in almost all metallic liquids and solids. In many metals, hydrogen accounts for 60% ~ 90% of the total gas content, so metal getter is often called "hydrogen getter" . Oxygen and copper under the liquid also has a strong affinity, there is oxygen or oxidation, so Cu2O formed in copper solution. 

(2) temperature and time the higher the temperature of the metal, the longer the contact time between the gas and the metal, the more dissolved gas. Only by increasing the temperature, the melt metal itself has a very high vapor pressure, leading to a gradual decrease in solubility. 

(3) diffusion velocity of gas in copper liquid the power frequency induction furnace greatly enhances the diffusion velocity due to the automatic stirring effect of electromagnetic force.

 (4) the relation between hydrogen and oxygen in liquid copper the relation between hydrogen and oxygen in liquid copper is inversely proportional to the relation between less hydrogen and more hydrogen and less oxygen, which may explain why thoroughly deoxy TP2 is more sensitive to hydrogen than T2. 

2. Copper smelting

Electrolytic copper is used as raw material for smelting of red copper in electric furnace. The electrolytic copper material itself contains gas, and its surface state has an important influence on the gettering of Molten Pool. When Red Copper is smelted, charcoal is often used as a covering and deoxidizer. The deoxidization occurs only on the surface in contact with the liquid metal. For the deoxidized copper (such as TP1 and TP2) , charcoal is used to deoxidize and phosphor copper is used to deoxidize finally before the furnace. Phosphor copper can be deposited in the bath and dissolved in the whole bath. In both deoxidization reactions, gases are produced, namely Co, CO2 and P2O5, which carry hydrogen up with them from the melt as it ascends the liquid surface. But this dehydrogenation is secondary or limited in comparison with deoxygenation. But, in fact, charcoal contains gas and water, especially not calcined good charcoal content. Therefore, it is difficult to avoid oxidation and hydrogen absorption under the condition of covering with charcoal. In smelting process, oxidation and dehydrogenation, hydrogen absorption and deoxidation exist at the same time. The question is which is the main one, which is the beneficial side or the harmful side.

3. Gas Effect on ingots in conventional production, the bubbles on copper products can be produced by extrusion or by ingots, which are accidental defects in technical wastes. The long-term, abnormally large number of bubbles quality responsibility in the pre-working procedureThe pores in copper ingots are filled with gas. The smaller pores can be compressed after being processed, and the subsequent processing may expose to surface defects, i. e. When there are a lot of air holes in Copper Ingot, there will be a big one at the same time. At this time, there will be bubbles in the middle and later section of the billet. Such serious blistering can not be repaired and can only be scrapped, minor repair into the drawing process. However, more peeling and inclusion were exposed during drawing, which had a great effect on the yield. In the process of cold rolling-drawing, there are many defects, such as peeling, inclusion, and so on, which lead to the crack in the pipe head. After annealing, there are a lot of eruptive bubbles in the drawn pipe, which is different from that of extruded blank. The bubbles are discontinuous and small, the big ones are like rice grains, the small ones are like needle points, which are hard to be found by naked eyes and can only be found by hand. The formation of gas bubble is the result of gas aggregation and expansion under the action of temperature and time after the pores are compressed. Finished Tube (no bubble) pressure, expansion, flattening performance is poor, reflecting the loss of plastic materials. Another cause of copper tube blistering is that the INGOT is supersaturated copper solid solution, which causes the third kind of stress and reduces the plasticity. During extrusion or annealing, due to the change of temperature, hydrogen is separated from the grain boundaries or inclusion boundaries which extend along the extrusion direction to form bubbles. The bubble of extruded billet and annealed pipe caused by red copper suction is characterized by bubble in almost every pipe, resulting in sharp reduction of yield and scrap in batches. This is quite different from other causes of blistering. It is suggested that the excessive gas content in copper ingot is due to the production operation not meeting the requirements of red copper melting and casting process, as well as raw material, covering agent and poor protective gas. All adverse factors should be removed as far as possible to ensure that production is built on a safe and high quality basis. The improvement process shows that the influence of Molten Pool (one-time suction) is the greatest. After this process is basically solved, the copper tube foaming is obviously reduced (less bubble is also smaller) . Only when the problems of secondary suction, dummy seat and padding are solved at the same time can the blister on the copper tube be completely eliminated. The key to preventing inhalation is to block the "air source" . The main measures are as follows: (1) electrolytic copper must meet the standards; the return charge of the foaming pipe is not used to produce red copper. (2) charge (material should be "no oil, no water, no hybrid") must be a multi-charge, full to fully drive off the charge of water vapor adsorption. Two or three times a batch, no more than a few shots. (3) charcoal must be dried (calcined charcoal is preferred) . Charcoal must be added immediately after the first charge and covered with a thickness of 100mm ~ 150mm to meet the requirements of prevention of inhalation, deoxidation and heat preservation. (4) the furnace door must be closed in time after charging and melting. (5) The desiccator of the gas generating system is filled with calcium chloride (dehydrating agent) and replaced in time to absorb water in the gas. The gas cover should be well covered, and the gas should be passed ahead of time from 5 min to 10 min before discharge, and the original air in the cover should be fully expelled. (6) the dummy block shall be dried and preheated with gas, and the dry copper block shall be used as the base, and sawdust shall not be used as the base. 

Source: Copper Alloy Casting

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