Characteristic structure and function of continuous annealing furnace(2)
(4) the steel inlet of line 5 and line 6 annealing furnace is not sealed with insulation cotton splint like line 1, 2, 3 and 4, but with sealing roller. Experience shows that with the use of thermal insulation cotton splint, the unwashed oil on the steel belt surface will rub against the thermal insulation cotton, and the thicker the product will become a small lump, which will stick to the surface of the subsequent steel belt, resulting in the leakage and plating spots after plating. Because the surface of the steel roller is easy to scrub, this drawback can be avoided. In the past, the company fengnan factory has tried the domestic imitation of the sealing roller, the result of the action is not effective, failed. However, that does not mean that the sealing roller is not good, but may be due to the design technology, processing quality is not satisfactory. According to the mature seal silver drawings and materials that have been used for many times in foreign countries, the design and manufacture of seal rollers are carried out. The actual situation after the production of line 5 indicates that the seal rollers are running normally and have good effects. In use need to note, meaning of the problem is that the sealing roller environment temperature is higher, in addition to keep turning in normal production, stop at furnace temperature and furnace cooling process, when the temperature above 200 ℃, always keep rotating seal silver state, in order to prevent the silver body bent out of shape.
(5) the original heat insert line of the company is not able to control the furnace pressure automatically and has a large fluctuation. In line 5 and line 6, the furnace pressure automatic control device is designed by our company's professional technicians in accordance with the requirements of the basic design made by the foreign party, so as to control the furnace pressure and keep the furnace pressure stable by controlling the furnace gas discharge valve. Unfortunately, after production, the furnace pressure, automatic control device could not achieve normal operation.
(6) some domestic hot-plating workers advocate high hydrogen reduction annealing because hot-plated aluminum, zinc and silicon have higher requirements on the surface cleanliness of the substrate than hot-dip galvanizing. Some people advocate that the H content of hot-plated aluminum zinc silicon wire furnace should be 30~35 percent, some people advocate 40~50 percent, some even advocate more than 50 percent, in fact, these technical views and plans are not appropriate. According to the practical experience of developed countries, on the premise of automatic control of furnace pressure, good sealing of furnace and low dew point of protected gas entering the furnace, 5% of H2 content is enough. Therefore, the plan for my line 5 and line 6 furnace is 5% of hydrogen content of protected gas. Low hydrogen reduction annealing will significantly reduce the gas consumption cost. However, 5% H2 content is lower than the actual H content of the company's original hot-dip galvanized wire stoves, which does not mean that the H content of hot-dip galvanized wire should be higher than that of hot-dip aluminized zinc silicon wire. The H content of the protective gas should be lower because the requirement of hot galvanizing for the cleanliness of the plate is not as strict as that of hot pound aluminum zinc silicon. According to foreign experts, under the same conditions, the content of H of hot zinc line is only 4%.It can also be seen that the company's original hot-dip galvanizing furnaces, although the conditions are worse, may indeed be hydrogen waste phenomenon, hydrogen content may be reduced.
(7) the original annealing furnace of each hot-dip galvanizing line of the company is so inaccurate that it is virtually useless to measure the plate temperature by using the old radiation pyrometer. The operator cannot adjust the furnace temperature according to the plate temperature measurement value, but can only adjust the furnace temperature by feeling and experience. Line annealing furnaces of no.5 and no.6 are installed in three key positions (end star of heating section, end star of cooling section and hot tensioning roll chamber), and a new type of foreign "stem" principle infrared thermometer is installed. The total cost is higher than the previous hot plating line. This kind of plate temperature measuring instrument on the working principle of a major change in, it is according to the blackbody radiation theory, using the steel belt of the silver and the furnace "sakura" clamp groove approximate dry properties of absolute black body, unlike the old thermometer vertical on steel strip surface, but aim at "sakura" clamp groove to the bottom of the measurement is not affected by steel band radiation rate, from the furnace wall temperature and the interference of other factors such as temperature, heating element temperature measuring accuracy up to 99.7%. With this kind of plate thermometer, the plate temperature can be accurately measured, which can be used as the basis to adjust the furnace temperature, so as to ensure the good mechanical performance of the steel plate surface stability, and save the heating power.