Discussion on inspiratory problem of red copper

Discussion on inspiratory problem of red copper0001

Dissolution of gas

Gases, mainly hydrogen and oxygen, that dissolve in copper. No diatomic molecular gas can be dissolved directly in a metal melt. The PROCESS of gas dissolution IS: adsorbed on the metal surface – atoms dissociated into elemental gases – diffuse into the metal lattice, forming solid solutions and compounds. Both HYDROGEN and oxygen are harmful elements in copper, which can not only reduce the performance of copper, but also may lead to the generation of “hydrogen sickness”. There is a certain amount of oxygen in copper ingots, but if excessive oxygen or hydrogen is dissolved into the ingots, it will be the main cause of quality accidents. Therefore, when smelting copper, measures must be taken to block the source of gas, avoid or minimize the contact of air, moisture, oil and various pollutants with the melt. The dissolution process of the gas is also to eliminate the “adsorption” this condition, so that the dissolution process cannot be established.

Under certain adsorption conditions, the degree of gas dissolution in the metal mainly depends on:

(1) Binding force of gas and metal.

The hydrogen atom of a gas is a very reactive element with a *** small radius. It 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 aspiration is often called “hydrogen absorption”. Oxygen and copper under liquid also have a strong affinity, there is oxygen absorption or oxidation, so Cu2O is formed and dissolved in liquid copper.

(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. It is only by increasing the temperature that the melt metal itself has quite high vapor pressure that the solubility gradually decreases.

(3) Diffusion velocity of gas in liquid copper

Due to the automatic stirring effect of electromagnetic force, the diffusion speed of power frequency induction furnace is greatly enhanced.

(4) The relationship between hydrogen and oxygen in liquid copper

The content of hydrogen and oxygen in liquid copper is inversely proportional to that of less oxygen and more hydrogen, which can explain why the thoroughly deoxygenated TP2 is more sensitive to hydrogen damage than T2.

Copper smelting

Electrolytic copper is used as raw material in red copper smelting furnace. Electrolytic copper material itself contains gas, and its surface state has an important influence on the suction of molten pool.

Smelting copper often uses charcoal as a covering and deoxidizer, its deoxygenation is only carried out on the surface in contact with the liquid metal, so it is called surface deoxidizer. On deoxygenated copper (such as TP1, TP2), the use of charcoal deoxygenation at the same time, before the oven is also used for the final deoxygenation of phosphorus copper, phosphorus copper can sink in the molten pool, dissolved in the entire molten pool, and the oxide interaction in the molten metal, deoxygenation effect is significant.

In the above two deoxyreduction reactions, gases are produced, namely CO, CO2 and P2O5, and these gas products can escape from the liquid surface with hydrogen on the way up from the melt. But this dehydrogenation is minor or limited compared to deoxygenation.

However, in fact, charcoal contains gas and water, especially without calcination of good charcoal content in particular. Therefore, it is difficult to avoid oxidation and hydrogen absorption under charcoal cover conditions. Smelting is mostly oxidation and dehydrogenation, hydrogen absorption and deoxidation process at the same time, the problem is which is the main, is the beneficial side or the harmful side, which needs to control the process conditions to avoid the advantages and disadvantages.

Effect of gas on ingot

In conventional production, bubbles on copper can be produced by extrusion or ingot casting. They are accidental defects in technical waste. The quality responsibility for the long term, abnormally large number of bubbles is caused by the pores in the copper ingot.

The pores in the copper ingots are filled with gas. Smaller pores can be pressed after processing, and may be exposed as surface defects in subsequent processing — peeling. When there are many pores in copper ingot, there will be larger pores at the same time. At this time, the back section of the extrusion tube blank will bubble. The bubbling is distributed continuously along the extrusion direction, and the more it reaches the back end (pressure residual end), the more serious it is, and the bubbling distribution is irregular in the circular direction. Such blistering can not be repaired and can only be scrapped, minor after repair into the drawing process. However, there are many peeling and inclusions in the drawing process, which have a great influence on the yield. Due to the high cooling intensity and small foaming (gas has no time to gather and expand), many defects, such as peeling and inclusion, are exposed in the process of cold rolling and drawing after water sealing extrusion of tube billet with small size, and partial splitting occurs in the pipe head. After annealing, the drawn pipe is shown as a large number of rash bubbling, and the extrusion billet bubbling is different: bubble more discontinuous, small, large such as rice, small such as the tip of a needle, the naked eye is not easy to find, need to feel can be detected.

The formation of bubbles is the result of gas reaggregation and expansion under the action of temperature and time after stomatal pressure.

The finished pipe (without foaming) has poor performance in pressure resistance, flaring and flattening, which reflects the loss of plasticity of the material.

Another reason for the formation of copper tube foaming is: ingots for supersaturated copper solid solution, so that the lattice distortion caused a third type of stress, reduce plasticity. During extrusion or annealing, hydrogen precipitates from the interface such as grain boundaries or inclusions elongating along the extrusion direction to form bubbles due to temperature changes.

Copper inhalation caused extrusion billet bubbling, annealing tube bubbling is characterized by: basically every tube has bubbles, resulting in a sharp reduction in the yield and batch scrap. This is quite different from other causes of blistering.

Suggestions for preventing inspiratory measures

The high gas content in copper ingot is due to the production operation does not meet the requirements of copper casting process, and the raw material, covering agent and protective gas are not good. All adverse factors should be eliminated to ensure that the production is established on the basis of safety and quality. The improvement and improvement process shows that: molten pool (one inspiratory) inspiratory influence is *** big, after this link is basically solved, copper tube bubbling is significantly reduced (bubble less and smaller). Only when the secondary suction and ingot seat, pad problem is solved at the same time, the copper tube foaming can be completely eliminated.

The key to preventing inspiration is to block the “air source”. The main measures are:

(1) Electrolytic copper must meet the standards; The bubbler tube return charge is not used to produce red copper.

(2) charging (the material should be “no oil, no water, no mixing”) must be loaded and filled at a time to fully drive away the moisture adsorbed by the charge. Concentrate 2 ~ 3 times to complete a furnace, shall not be less than many times.

(3) charcoal must be dry (calcined charcoal is best). *** Charcoal must be added immediately after loading, covering the thickness of 100mm ~ 150mm, to meet the requirements of preventing inspiration, deoxygenation and heat preservation.

(4) After charging melting, the furnace door must be closed in time.

(5) The dryer of the gas generator system is loaded with calcium chloride (dehydrating agent) and replaced in time in order to absorb the water in the gas. The gas cover should be well covered, and the gas should be put on in advance 5min ~ 10min before the discharge to fully remove the original air in the cover.

(6) ingot base should be dried with gas, preheated, and dried

Copper block bottom, do not use sawdust bottom.