For the steel plant, the perfect anhydrous stemming should meet the requirements: good operating, good opening, easy maintenance of the depth of the iron hole, long enough to meet the requirements of the blast furnace, no spillage, no smoke, etc.
In fact, any kind of technical staff, suppliers and anhydrous stemming supplier can't perfect at the same time to do all of the above requirements, stemming accidentally is easy to occur in the use of: play the stemming difficult, the front of iron mouth have hard point, iron mouth break out and leakage, the depth of iron mouth is shallow, the output time is short, and even opening the mouth while put rockets and splash a long time. In general, problems are not completely isolated, but are often associated, that is, once a problem occurs, it is often accompanied by a number of other problems. For example, when the plasticity of stemming is poor, these may occur at the same time: it is difficult to make, there is a hard shell at the front of the iron mouth, or the probability of iron mouth leakage is high, the difficulty in opening leads to the burning of oxygen, which destroys the iron mouth passage, thus resulting in a short time of iron output. In the author's opinion, the difference between the good and bad quality of the anhydrous stemming is often only on a line. What seems to make the gun mud with disastrous results, if you adjust the process formula a little, it may become more ideal.
This paper focuses on the common problems existing in the application of anhydrous stemming and the solutions.
1. Difficult to hit the stemming, can not hit the stemming
If the equipment have a fault and the iron mouth channel is not smooth and have other external reasons, the reason for the stemming can not be hit is often have not enough plasticity, with the stemming head after the discharge of the stemming spread, dry. The direct cause may be: asphalt quality is poor, the content of the β-resin is low; insufficient amount of asphalt; the masha value is too high; the quality of clay binder is poor or too little.
Solutions: according to the actual situation, increase or decrease the force of the toaster stemming, add waste oil and other lubricants to the stemming as temporary countermeasures; adjust particle gradation appropriately and increase aggregate proportion; increase the amount of asphalt; increase the liquid binder, decrease the masha value of stemming; change clay type or increase clay dosage.
2. High probability of iron mouth leakage
The reasons for the high probability of broken leakage usually include: 1) poor clay plasticity, insufficient clay dosage, insufficient organic binder dosage, etc. 2) the gun mud is too soft, which causes the iron mouth channel and stemming bag after the closure to be not compact, and the stemming contracts too much at high temperature; 3) the total amount of swelling agent in the stemming is not properly controlled, resulting in a large change in the stemming line; 4) the sintering strength of stemming is too high, and leakage occurs due to mechanical impact in the opening process.
Solutions: as a temporary solution to the operation of the blast furnace, the poor clay of the gun can be considered appropriate roast stemming; if the stemming is too soft, don't bake it. You can also hit the stemming with water to cool it, so as to prevent the stemming from being overheated. When plugging the mouth, adopt the method of hitting stemming in sections and filling stemming by inching; adjust the amount of expansion agent in the formula; slow down the sintering speed of stemming and reduce the opening strength; change the type of clay, choose the appropriate viscosity fineness, and control the reasonable amount of clay; control the amount of asphalt, tar binder and masha value.
3. red iron mouth, hard shell phenomenon
The phenomenon of hard shell refers to the opening process, in the last little section near the opening is very hard, the drill bit or steel drill does not go in and makes a sound similar to that of drilling on the iron sheet. After the drill pipe or steel drill is pulled out, only the bit part is red, but the drill pipe is not red. The reasons for the formation of the hard shell phenomenon are mainly as follows: the combined dose is relatively low and the plasticity of the stemming is slightly deficient (with the stemming shooting is slightly difficult and the stemming extruded after the withdrawal of the stemming sends out dry); due to the small viscosity of molten iron, it is easy to seep into the stemming bag through the pores or gaps, and then solidify to form the iron shell.
Red iron mouth refers to the iron mouth in half or 2/3 after the passage is red, drill or steel drill to the part after the heat, strength decline, difficult to continue drilling, drill pipe pulls out after the front is red, and even sticky drill pipe, drill pipe is twisted into a twist. Red iron mouth is actually a serious version of the hard shell, iron penetration.
Solutions: the field operation can be appropriate to roast the stemming; appropriately increase the amount of asphalt; increase tar binder and decrease masha value; if a large amount of metallic silicon material is added to the formula, the dosage should be reduced.
4. Short iron producing time
If it is not obvious that the depth of the iron mouth is insufficient or the blast furnace smelting is not suitable, the iron producing time is short, which is generally due to the low grade of ore, the large amount of slag, and the lack of corrosion resistance of stemming. Of course, shallow iron hole, with a large diameter drill opening, and so on, will also lead to short iron producing time.
Solutions: increase the ratio of silicon carbide and silicon nitride; adjust the aluminum-silicon ratio in the stemming matrix, mainly by adjusting SiO2 powder, clay and other materials to make the matrix more resistant to slag erosion; proper introduction of graphite and other additives to improve the corrosion resistance; because of its high carbon residue, the stemming has better corrosion resistance. Changing the ratio can improve the compactness of stemming and the corrosion resistance. The conventional system of alumina - silicon carbide - carbon was broken through, and a new material system with better compatibility with slag was studied.
5. The iron mouth is not deep enough
To solve the problem of insufficient depth of iron mouth, we can start from the following aspects: 1) appropriately increase the amount of stemming, and even adopt such operation methods as segmental mud tapping and inching mud filling; 2) the plasticity of stemming should be moderate, not too soft and hard, so as to form a good iron mouth channel and stemming bag; 3) ensure the right amount of expansion agent to realize the micro-expansion of stemming after high temperature sintering, which can improve the combination of old and new stemming; 4) improve the corrosion resistance of stemming, stemming bag is not easy to be eroded by slag iron; 5) close the tuyere above the iron mouth and reduce the blast furnace wind pressure appropriately, which is more conducive to maintaining the iron mouth depth.
6. Poor quality stability of stemming
In order to improve the quality stability of stemming, efforts must be made in many aspects: 1) when designing the formula, reasonably distribute the proportion of aggregate and powder to make it less sensitive and more inclusive to changes of some factors; 2) adopt multilevel dosing and use less aggregate; otherwise, the particles are prone to severe segregation, resulting in poor stability of the ratio of grain size, thus causing huge fluctuation of oil dosage; 3) the stability of water, fineness, chemical composition and other indicators of key raw materials shall be strictly controlled; 4) strictly control the production process parameters, including dry mixing time, grinding time, stemming temperature, masha value, etc.; 5) when seasonal temperature changes and raw materials fluctuate, the formulation and process parameters should be timely predicted and adjusted; 6) reasonable planning of packing, stemming trapping and other details.
To sum up, stemming is very prone to various problems, perfect stemming does not exist, but as the supplier and technical personnel of anhydrous stemming, we should try to make stemming in the use of as few problems as possible, occasionally some problems will not cause serious adverse consequences; once a certain problem appears more obvious, can timely and effectively deal with, do not let the same kind of problem repeatedly.