Electrode safety accidents are common safety accidents in nonferrous metals and calcium carbide companies in smelting plants using submerged arc furnaces. The specific analysis of the causes of electrode accidents is accurate, and purposeful preventive measures can be taken to reduce the occurrence of electrode safety accidents. However, because the analysis of electrode safety accidents is affected by various factors of electrode paste supply manufacturers and electrode paste application manufacturers, In order to accurately judge the cause of electrode safety accidents, we must agree with each other's objective direct evidence, and the section of electrode is a good objective direct evidence. Therefore, the analysis of electrode section has vital practical significance.


1、 The electrode paste shrinks and loosens, resulting in layered stone and granular materials


1. Section condition: the section of the electrode has significant hierarchical shrinkage and looseness of particles. According to the size of the pyrogen of the electrode burning radiation source, the section shows two conditions: one is the deposition of granular materials along the outer ring line of the electrode, and the other is the deposition of granular materials in the middle of the electrode.


2. Other phenomena: the fluidity index of electrode paste exceeds 2.0 and the elongation exceeds 40.


3. Root cause: the electrode paste influenza is too good, resulting in the shrinkage and looseness of particles. The strength of some electrodes with more stones is slightly lower, and they are easy to be broken by external force. Some electrodes with more particles are easy to be broken by the thermal stress of the electrode itself. The two different accumulations of stone materials are caused by different sintering methods.


2、 There are too many and too long ribs in the electrode cylinder, which are often seen in the new ignition furnace


1. Section condition: the section is in full bloom along the rib.


2. Other phenomena: the inspection index value of electrode paste is not abnormal, and there are many phenomena of valve falling, bifurcation and turning around after ignition.


3. Root cause: for the new ignition furnace, it is generally a problem on the ribs of the electrode cylinder. Too many, too dense and too long ribs will cause the electrode paste to be separated into too many small pieces, and the overall strength of the electrode will be reduced. In addition, the wrong drilling form or too small drilling on the ribs will also cause the electrode to fall and crack.


3、 The electrode paste has no fluidity or its fluidity is too low. The discrimination basis is that the plasticity value of the electrode paste is less than 5%


1. Section condition: there are obvious cracks on the section, and the appearance of electrode paste is faintly visible.


2. Other phenomena: the fluidity index of electrode paste is less than 1.0 and the plasticity value is less than 2.0.


3. Root cause: the fluidity index of the electrode paste is not very good. It can not fill all the indoor space of the electrode barrel, resulting in cracks and hanging paste, which reduces the overall strength of the electrode.


4、 Top layer of paste column melts


1. Section condition: the section is loose and cracked, and some sections are leveled.


2. Other phenomena: through observation, the top layer of the paste column melts into viscosity, and the actual operation of boiler pipe blowing occurs when the paste is added here before the electrode breaking time. The difference between the shrinkage and looseness of this kind of broken electrode and electrode paste depends on the fluidity of the electrode paste itself, and everything is normal.


3. Root cause: the heat transfer coefficient of common raw materials for electrode paste of large and medium-sized submerged arc furnace is high, and the top layer of paste column is easy to melt. In case of a long shutdown time, the melted electrode paste at the top layer will condense for a second time. If the electrode paste is not supplemented immediately, the whole process of electrode sintering will be broken. After the secondary temperature rise, the influenza of electrode paste will decrease, and the electrode strength will be slightly low, resulting in hard electrode breaking.


5、 Poor heat shock resistance of electrode paste


1. Section condition: Section leveling.


2. Other phenomena: the change of electric flow before electrode disconnection is relatively large, and everything else is normal.


3. Root cause: the change of current will lead to the thermal difference of the resistors of each part of the electrode itself, and this kind of difference will lead to a certain thermal stress in the electrode, which will cause cracks when the heat shock resistance of the electrode paste is weak. In the whole process of electrode sintering, too fast sintering rate will also expand the temperature difference inside and outside the electrode. When there are vertical cracks on the electrode section and there is no bifurcation under the electrode section, it can be generally recognized that the thermal shock resistance of the electrode paste is weak.


6、 Foreign object protection


1. Section condition: leveling, dirty things can be seen.


2. Other phenomena: there are dirty things in the operation of electrode paste, the electrode barrel has no cover, and the smoke and dust in the production workshop is relatively large.


3. Root cause: the decoration of dirt blocks the routine fluidity of electrode paste, so that the left and right electrodes of dirt can not be sintered as a whole, and the electrode strength is reduced, resulting in rupture


7、 Black core soft fracture


1. Section condition: the area near the electrode section shall be leveled, and the middle ring shall be raised or lowered.


2. Others: electrode sintering is slow and everything else is normal.


3. Root cause: the electrode is sintered too slowly, and the sintered core around the electrode out of the kneader is not sintered. However, the sintered electrode has low strength. At this time, it is easy to break when it is impacted by external force.


8、 What's the problem with the preparation of waste from the furnace? The carbon content is low and the slag alkalinity is low


1. Section condition: the end of the electrode is severely corroded and bifurcated, and the electrode is significantly narrowed from top to bottom.


2. Other phenomena: the electrode paste is normal, the temperature of the heating furnace is low, the production is small, and the electrode is inserted too deep.


3. Root cause: there is a lack of carbon in the return waste, the dissolved material corrodes the electrode seriously, the overall strength of the narrowed electrode is reduced, and it is easy to break when it is impacted by external forces.


9、 Poor oxidation resistance of electrode paste


1. Section condition: the electrode is significantly narrowed, and the side air oxidation is relatively serious.


2. Other phenomena: the actual operation of submerged arc furnace is normal without water seepage, and the application of centrifugal fan has no change or power failure.


3. Root cause: the oxidation resistance of electrode paste is poor. Too much air oxidation will narrow the electrode and reduce the overall strength of the electrode. It is easy to break when it is impacted by external force. The judgment of the weak oxidation resistance of the electrode paste and the corrosion of the electrode caused by lack of carbon is that the narrower under the material surface is generally due to the larger element of lack of carbon, and the narrower on the material surface is due to the poor oxidation resistance of the electrode paste.


There are many soft and hard breaking accidents of submerged arc furnace electrode, which are also very complicated. It is impossible to analyze the cause of the accident in an all-round way only from the section. Therefore, before in-depth analysis of the cause, we must ensure that the inspection index value of electrode paste meets the standard, especially the strength. Only the electrode paste with qualified strength is necessary to analyze the electrode section. The amount of data given by the electrode section can also objectively reflect what happens to the electrode in the whole sintering process, Furthermore, a method is given for analyzing electrode safety accidents.


For more information on the cause analysis of electrode accident of submerged arc furnace, please pay attention to the official website: http://www.ayynd.com/


Key words: submerged arc furnace DC submerged arc furnace DC electric arc furnace