Discussion on antiwear of clinker castor coolerDate: 2019-06-25 Views:
Castor cooler is an important main equipment of clinker firing system in cement plant. It is responsible for cooling, heat recovery, transportation, crushing and other functions of high temperature red hot clinker (about 1400 ℃). In the process of clinker transportation and crushing, the wear of clinker to objects can not be ignored. Transportation refers to the fact that the castor cooler should send the clinker from the human end to the discharging end, the castor plate and the side plate or the push rod, and the scraper and kiln seal cover will be subjected to cutting wear and scraping when the clinker moves relatively. Therefore, the wear resistance should be fully considered when selecting the materials of these parts.
Crushing means that the clinker crusher of the castor cooler should break the bulk clinker into the specified discharge particle size (the general requirement is ≤ 25 mm), for the third generation castor cooler, the hammer head will be seriously worn and strongly impacted, and the clinker hardness after cooling is higher, so the hammer head should choose high toughness and wear-resistant material; For the fourth generation castor cooler, the roller of roller crusher has wear similar to that of roller in the process of extruding clinker, and the anti-wear measures similar to those of extruder should be taken. In addition, the broken clinker particles have high energy, which will cause impact wear on the surrounding shell and grid device, and these parts should also be resistant to impact. Wear-resistant material.
In the face of the fact of wear, in addition to the effective methods of process operation control, designers and developers generally choose wear-resistant materials from two aspects: one is to choose wear-resistant materials seriously; the other is to adopt innovative anti-wear measures in structural design. This paper makes a brief introduction and analysis of these two aspects.
Selection of abrasion resistant materials for castor cooler.
1.1 selection of castor plate and side plate materials
1.1.1 Selection of castor plate and side plate material in high temperature section.
At the end of castor cooler, the clinker temperature is the highest (about 1400 ℃), which is the most serious oxidation corrosion of castor plate and side plate at high temperature, so the requirement of selecting castor plate and side plate material is the highest. In addition, the different structural forms of the castor bed have different requirements for the material of the castor plate and the side plate. According to the working conditions and wear failure mechanism of the feeding end of the castor cooler, the castor plate and the side plate there should be heat-resistant steel with good oxidation resistance, high heat resistance temperature and good wear resistance. According to the influence and function of alloy elements and carbon in steel, we know that Ni element is Austenite forming element, which has good coordination with Cr and oxidation resistance. Also, the content of C element is at the upper limit, which is favorable to wear and heat, but is not conducive to oxidation, so the carbon content of the heat-resistant steel should be controlled as much as possible near the center line, generally about 0.25%-0.40%. Based on the above factors, according to the standard of heat-resistant steel castings in China (GB/ T8492-1987), we recommend the selection of ZG35Cr26Ni12 heat-resistant steel in the high-temperature section of the cold-cooling machine (the clinker temperature is about 1400-700 ℃). The heat-resistant steel has the highest use temperature of 1100 DEG C, high high-temperature strength, oxidation resistance and abrasion resistance. The carbon content may also be selected The high ZG4OCr25Ni20 heat-resistant steel has the highest service temperature of 1150 ℃, high creep strength and durable strength, strong resistance to high temperature gas corrosion, good wear resistance, but high cost.
The feeding end of the cold-cooling machine is different from the feeding end, and the requirements on the material of the corrugated plate and the side plate are different. For example, the third-generation cold-cooling machine designed by the first, the second-generation cold-cooling machine and the few units is the third-generation cold-cooling machine which is designed by a few units, the first-row corrugated plate of the human material end is a movable deflector plate, and the clinker discharged by the kiln is quickly pushed away by the movable deflector plate, and no snowman can be formed on the basis of no rooting. The disadvantage of the invention is that the high-temperature red hot clinker discharged from the kiln is directly washed on the corrugated plate, so that the high-temperature oxidation and peeling of the graphite plate is caused, and the abrasion is particularly serious, and the service life of the ZG40Cr25Ni20 heat-resistant steel is only 3-6 months. it is inevitable to frequently replace the corrugated plate of the high-temperature section, which greatly The running rate of castor cooler is reduced (≤ 80%) and the cost is increased more.
1.1.2 selection of castor plate and side plate material in medium temperature section
In the middle temperature section of the castor cooler, the clinker has been significantly cooled down, and the clinker temperature becomes about 700400℃. The high temperature oxidation corrosion ability of clinker has been significantly reduced, and the application of thick material layer control technology can effectively protect the castor plate. Due to the thick material layer, the clinker close to the castor plate at the lowest layer is fully cooled to prevent the heat wear and thermal corrosion of the upper layer of the high-temperature clinker, which is beneficial to extend the service life of the castor. ZG30Cr26Ni5 heat-resistant steel can be used as the castor plate and side plate in the medium temperature section of the castor cooler. The maximum service temperature is 1050℃, which has good high temperature strength and anti-oxidation. The performance is good, the antiwear performance is good, and the bearing temperature can reach 650 ℃. Or choose ZG35Cr24Ni7SiN heat-resistant steel, the highest operating temperature is 1100 ℃, the high temperature strength is high, the oxidation resistance is good, but the cost is high, generally does not recommend the use.
1.1.3 selection of cage plate and side plate material in low temperature section
In the low temperature section of castor cooler, the clinker temperature has been reduced to the lowest, generally about 400-110 ℃. At this time, the hardness of clinker has reached the highest. When selecting castor plate and side plate, it mainly considers its wear resistance and has a certain oxidation resistance. We recommend ZG4OCr9si2 or ZG3OCrl8Mnl2Si2N, can also choose ZG30Cr26Ni5 heat-resistant steel, the cost is slightly higher.
1.2 selection of hammer material for crusher
The working principle of castor cooler clinker crusher is to break large pieces of clinker by using the kinetic energy of high speed rotating hammer, and at the same time, the clinker is ejected to the counterattack direction, so that the clinker under the falling body is cut and extruded by hammer head and grid plate, and the particles that meet the requirements are discharged from the castor seam of the grid plate.
The wear mechanism of the hammer head of the crusher is complicated, the wear of the hammer head is closely related to the material and quality of the hammer head, and also is closely related to the nature of the crushed material (in and out of the material particle size and hardness) and the working condition conditions. It is not discussed in detail here, and only a brief analysis is made on the wear mechanism of the hammer head when the clinker is broken.
Due to the high hardness of the cooled clinker, when the clinker and the hammer head at the high-speed rotation generate a positive impact, the cone angle of the clinker is pressed to the hammer surface, an impact pit is formed on the hammer surface, and the impact force of the large-block clinker is converted into the pressure stress on the hammer surface, and the hammer head is impacted and the abrasive is abraded. The impact force is decomposed into the normal pressure stress of the vertical hammer surface and the tangential stress of the parallel hammer surface when the clinker is struck by the hammer head at a certain angle and the high-speed rotation. Wherein the method comprises the following steps of: forming an impact pit on the hammer surface by a normal pressure stress, cutting the surface of the hammer head by a tangential stress to form a channel cutting groove, and forming a cutting erosion and abrasion on the hammer head. To sum up, the hammer head The wear failure mechanism is impact chiseling abrasive wear and cutting scour wear, so the hammer should choose high toughness wear-resistant material.
The high manganese steel has good plasticity and toughness, can produce work hardening after strong impact, increases the deformation resistance, has better wear resistance and is the preferred material for the hammer of the clinker crusher, and is especially suitable for the hammer of 50 kg or more of the large and medium-sized crusher. The weight of the hammer of the general clinker crusher is about 63.5 to 65kg, the grain size of the maximum clinker is between 400 and 600 mm, the impact force is high, and the work hardening property of the high manganese steel can be fully utilized. According to China's high manganese steel casting standard (GB/ T5680-1998), we recommend the selection of ZGMnl3-2 or ZGMnl3-3 high manganese steel. For clinker crusher hammer and liner material. The castings must be treated with water toughness, the microstructure should be single Austenite, and the mechanical properties should conform to the national standard. After water toughness treatment, the properties of high manganese steel can be brought into full play, and it has high tensile strength, plasticity, toughness and non-magnetism. When it is subjected to severe impact and strong pressure deformation, the surface produces working hardening and maraging, thus forming a high wear-resistant surface layer, while the inner layer still maintains excellent toughness, even if the parts wear to very thin, it can still bear a large impact load.
1.3 selection of blade grinding materials for other parts of castor cooler
When the clinker is broken by the castor cooler, some clinker particles are ejected at high speed in the counterattack direction, and the shell is hit violently to form an impact pit, resulting in impact chiseling abrasive wear. In order to prevent clinker particles from ejecting too far on the castor bed and causing repeated cooling, multiple rows of chain screens are usually set in front of the clinker crusher to block it. In the strike area of clinker particles, set up anti-impact liner, the material is generally 16Mn high quality carbon structural steel, or use ZGMn13-l.
The pulley and wheel rail in the support device of castor cooler are also easy to wear. Between the supporting wheel and the wheel / rail belongs to the simple compression stress, which requires wear resistance. It is generally recommended that ZG3ro-570 cast carbon steel parts be used for surface quenching after machining. the quenching depth is 5 mm and the hardness is about HRC50.
1.4 selection of wear-resistant materials for special components of the fourth generation cooler
Whether the fourth generation cooler is a new type of push rod high efficiency cooler or a new type of S castor cooler in Chengdu, the former push rod and seal cover, the latter scraper and seal cover, are exposed to clinker. The material face of push rod, scraper and seal cover is made of wear-resistant material which can be used for hard surface treatment. In addition, the roll of the roller crusher equipped on the new S castor cooler is also the same.
Anti-wear measures used in castor cooler
In the development of the cold-cooling machine, the technical personnel attach importance to the wear problem, one is to make full use of the action of the clinker self-protection layer, and the other is to minimize the relative movement between the components.
The first row of castor plates of the third generation castor cooler or the fourth generation castor cooler designed by most units at home and abroad are designed as fixed castor beds with a certain tilt angle. Because the clinker has a certain rest angle, a static cold clinker layer is formed between the castor plate on the fixed castor bed and the flowing red hot clinker layer, that is, the automatic antiwear protective layer of the transportation channel (Fig. 1), also referred to as the clinker self-protective layer, and friction occurs between the clinker layers. The static cold cooked material layer acts as the heat insulation protective layer on the castor plate. As the red hot clinker layer slips through the static cold clinker layer, the thermal wear and overheating load of the castor plate are prevented, and the castor plate is greatly improved. The service life reduces the mechanical failure rate of the hot-end castor bed and significantly improves the running rate of the castor cooler (≥ 95%). Even if ZG30Cr26Nis heat-resistant steel is selected, its service life can reach about 15 months. The service life of ZG35cr26Ni12 heat-resistant steel can reach more than 24 months.
The S-type low resistance non-leakage fixed castor plate of the new S-castor cooler is specially designed to ensure the formation of self-protective layer of clinker. Because there is no relative sliding between the castor plate and the contact castor plate, there is no wear and tear of the castor plate.
3 concluding remarks
In a word, according to different working conditions, reasonable selection of heat-resistant and wear-resistant materials and anti-wear measures of castor cooler can effectively improve the operation rate of castor cooler, save a lot of costs and obtain considerable economic benefits for enterprises.