Initiated a new process of rapid casting of conventional rolls
The LMM roll manufacturer completed the pouring of 8 Ø300-Ø400 rolls (one ladle of molten iron 5t) in 4 minutes and 50 seconds, which shortened the pouring time by more than half compared with the traditional casting method, and created the fastest casting speed record for metallurgical cast iron rolls in my country.
The normal method of pouring rolls is: one roll is poured at a time, that is, after the molten iron is poured once, when the rotation of the molten iron in the riser stops, a thin stream of molten iron is added to the height specified by the riser to prevent the neck of the upper roll from shrinking. . And the new method of rapid pouring is: pouring the 1st to 4th rolls for the first time, and then turning back and injecting the 1st to 4th rolls in a trickle flow. Cast the 5th to 8th rolls for the second time, and then turn around and refill the 5th to 8th rolls in a trickle. The main point of this method is: cast 4 rolls at a time, and when the molten iron is refilled in a trickle flow, the rotation of the molten iron in the riser basically stops, which is the best time for the trickle refilling, which saves the time of waiting for each roll Iron falling time and rotation time shorten the pouring time of the whole ladle of molten iron. The key to the new method of rapid pouring is: full quantitative pouring must be adopted, and the measurement of molten iron must be very accurate to ensure that the molten iron is poured in place at one time.
Rapid pouring of rolls can greatly reduce the temperature difference between front and rear when pouring multiple rolls from one ladle of molten iron, and avoid defects such as air holes, slag inclusions, shrinkage cavities and looseness of the rolls cast later due to low pouring temperature of molten iron. For nodular iron rolls, due to rapid pouring of complete molten iron after spheroidization and inoculation, inoculation decline can be greatly reduced, the inoculation effect can be guaranteed, and the tensile strength of nodular iron rolls can be significantly improved. After testing, the tensile strength of chromium-molybdenum, low-nickel and medium-nickel nodular iron conventional rolls produced by Zhonghang Roller Company is generally in the range of 400-450N/mm2.
Initiated a new process of wet-method furnace building for 3t intermediate frequency electric furnace
LMM roll manufacturing plant boldly adopted wet furnace construction technology on the 3t intermediate frequency electric furnace, and its furnace life exceeded the 200 furnace mark, and set a new record for the longest furnace life of 275 furnaces. Reaching such a high level of furnace life under discontinuous smelting conditions is a big step forward.
The successful construction of the 3t intermediate frequency electric furnace by the wet method is a major challenge to the traditional dry method. It is understood that the wet method was used to build the furnace on the 3t intermediate frequency electric furnace and was successful.
The wet method of furnace construction means adding a certain amount of water to the furnace construction materials, taking out the steel crucible mold after being firm, and baking it with firewood for several hours before loading it for smelting. Compared with dry furnace construction, wet furnace construction can save one steel crucible mold each time, save 25 to 28 hours of oven time, and save about 2500 degrees of electricity consumption for the oven. Furnace, turn on the next day. Wet furnace construction can not only greatly reduce the cost of furnace construction, but also increase the output of intermediate frequency electric furnaces.
The 3t intermediate frequency electric furnace has been used in the wet method for nearly ten years and has achieved remarkable economic benefits. In recent years, new progress has been made in the use of tamping machines instead of manual knotting of the lining in the wet method of intermediate frequency electric furnace construction. , The tightness of the lining is improved, which increases the furnace life of the intermediate frequency electric furnace. In addition, the furnace process was boldly innovated, the furnace lining was newly built to cancel the furnace part, and the furnace was directly charged for smelting, saving furnace time and firewood. After the above two improvements, a new record has been achieved for dismantling the furnace, building the furnace on the same day, and opening the furnace on the same day.
Initiated a new technology of centrifugal roll rapid casting
Most of the small and medium-sized centrifugal rolls produced by the company have a roll body diameter in the range of Ø290-Ø400, and the daily production of centrifugal rolls is 20-26 pieces. In the past, the pouring method of the centrifugal roll was: after the first centrifugal roll was completely poured (including pouring the outer layer and the core filling), the second centrifugal roll was poured. Casting in this way takes about 15 minutes to pour 1 centrifugal roll, and only 4 centrifugal rolls can be poured per hour. The new method of fast pouring is now: use 3 centrifuges to continuously pour 3 centrifugal rolls, that is, after the outer layer of molten iron on the first centrifugal roll is poured, immediately pour the second and third outer layer of molten iron on the centrifugal roll. Immediately thereafter, the first, second, and third centrifugal roll filling molten irons are poured. Since the new method of continuous casting of 3 centrifugal rolls is adopted, it only takes about 55 minutes to cast 6 centrifugal rolls. Compared with the 90 minutes required to cast 6 centrifugal rolls by the old method, the new method of rapid casting can shorten the pouring time of centrifugal rolls. About 40% of the time. The new method of rapid pouring of centrifugal rolls can not only shorten the pouring time by 40%, that is, increase the productivity of centrifugal rolls by 40%, but also shorten the residence time of high-temperature molten iron in the electric furnace, greatly reduce the change of C and Si content in molten iron, and stabilize the chemical composition. It is very beneficial, and at the same time, it can also reduce power consumption.
Using advanced technology, the strength of the centrifugal roll reaches the advanced level in China
The centrifugal roll adopts advanced inoculation technology and boldly adjusts the chemical composition, so that the tensile strength of the roll neck of the centrifugal roll reaches 550-650N/mm2, and the highest reaches 670N/mm2, creating an advanced level in China.
If the inner layer of the centrifugal roll is made of nodular cast iron, the inoculation method of the molten iron core usually adopts one-time inoculation (in-ladle inoculation) or two-time inoculation (in-ladle inoculation + inoculation with flow).
When the early inoculation method was adopted for the core-filled molten iron, it was often due to the high Si content before the spheroidization of the core-filled iron, and the low amount of inoculated ferrosilicon after spheroidization (<0.4%), the inoculation effect was not good, and sometimes the core-filled iron The Cr content in the water is high (Cr0.30 ~ 0.50%), and no remedial measures have been taken, resulting in a small amount of graphite in the core tissue of the centrifugal roll, the graphite is large and not round, and sometimes reticular cementite appears. The tensile strength of the roll neck of this type of roll is low, generally around 400 N/mm2, so roll breakage occurs from time to time.
In order to improve the tensile strength of the roll neck of centrifugal rolls and reduce broken rolls, a new process of standardized secondary inoculation (in-ladle inoculation + flow inoculation) of core-filling molten iron has been implemented since 2006. That is, after spheroidizing the molten core iron, 0.50-0.80% of ferrosilicon must be added for inoculation in the bag, and 0.10-0.20% of ferrosilicon must be added for inoculation with the flow when the core-filled molten iron is poured. And enforce the provisions of the second pregnancy. In case of high Si content before spheroidization of the filled core iron, the regulations above the secondary inoculation must also be implemented. For this reason, boldly adjust the upper limit of the final Si content of molten iron core, from the original 2.50% to 2.80%. Practice has proved that even if the final Si content reaches 2.51-2.80%, the tensile strength of the roll neck can still reach 530-630 N/mm2.
Since the implementation of the new process of secondary inoculation for centrifugal rolls in 2006, nearly 13,000 tons of small and medium-sized centrifugal rolls and nearly 26,000 rolls have been produced. So far (as of June 2010), there has been no roll breakage caused by centrifugal roll quality problems. significant economic benefits.
