Application of new technology of slab caster in th

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Application of new technology of slab caster in Jigang No.3 Steelmaking Plant Abstract: the process characteristics and production application of the main advanced technologies adopted by VAI slab caster in Jigang No.3 Steelmaking Plant, such as mold width adjustment, mold expert system, mold high-precision hydraulic servo vibration system, intelligent sector soft reduction technology, DYNACS secondary cooling water distribution control, are introduced. The application of these new technologies is of great significance to improve the operation rate of continuous caster The pass rate of slab plays an important role

key words: casting machine; Crystallizer; Width adjustment; Expert system; The key equipment and technology of No.1 slab caster of Jinan Iron and Steel Group Corporation No.3 Steelmaking Plant (hereinafter referred to as Jinan Iron and steel No.3 Steelmaking Plant) was introduced from VAI. It is one of the most advanced continuous casters in China at present, Taking Changzhou as an example, with the highest degree of automation and the most complete supporting equipment. It is one of the main processes of the modern plate production line of Jigang 120t converter CAS LF/VD slab caster medium and heavy plate mill. After being put into production, it realizes the direct hot charging and rolling of flawless billets with multiple varieties and specifications, which will play an important role in Jigang becoming a well-known base of plate products at home and abroad in the future

2 the new technology adopted by the continuous casting machine

the main process parameters of the continuous casting machine are as follows

caster type: straight arc slab caster

number of streams: 1 machine 1 stream

output: 1.25 million T/a

slab size: thickness 200, 270mm

width 1200 ~ 2100mm

length 2000 ~ 3200mm

mold length: 900mm

metallurgical length: 34.2m

drawing speed: [high quality steel ≤ 1.7m/min low carbon steel ≤ 2.2m/min

arc radius: 10M

ingot loading method: top loading

2.1 mold width adjustment

in order to improve the operation rate of the caster and meet the needs of continuous casting and rolling production, the width adjustment technology of the mold is adopted. In the past, the slab caster used to change the size of the slab, either replacing the mold or stopping the machine to adjust the size of the mold. These two methods not only affect the output of the caster, but also are difficult To meet the multi specification requirements of each rolling unit in the rolling mill. The caster adopts advanced width adjustment technology, which can make the narrow surface of the mold move steplessly without stopping casting or even reducing the casting speed, and change the slab width to the required size, which provides convenience for the slab to be directly hot sent to the medium and heavy plate plant, and greatly improves the production capacity and efficiency of the caster and increases the metal yield. The width adjustment system is mainly composed of hydraulic drive system, position measurement system and computer automatic control system. The movement of the narrow side and the adjustment of the inverted taper of the mold copper plate are carried out by the hydraulic system. The position sensors installed on the four hydraulic cylinders are used to measure the position of the narrow side and the inverted taper, and the width adjustment process is controlled by the width adjustment control program. Among them, the computer control program can realize the following functions:

(1) set the start and end time of automatic width adjustment of crystallizer and the corresponding casting flow tracking value, and set the width adjustment value of slab

(2) automatically calculate the running speed and mode of copper plate and the length of wedge billet during width adjustment

(3) automatically calculate and determine the maximum blank drawing speed of the caster during width adjustment

(4) abnormal conditions such as excessive running resistance and excessive deviation of inverted taper adjustment value occur during the width adjustment. The program impact test is similar to the cupping test, which is an important step to detect the impact toughness of stainless steel metal materials. The width adjustment can be automatically terminated to prevent steel leakage and other production accidents

after the casting machine was put into operation, the trial application of the width adjustment technology showed that the width adjustment process operated smoothly and the width adjustment accuracy was reliable. The adoption of this technology will play an important role in improving the operation rate of continuous casting machine, adapting to continuous production of continuous casting and rolling, and adapting to small order contract production. Because wedge-shaped billets are inevitable in width adjustment, slab edge cutting machine should be equipped when width adjustment production is often carried out to improve slab yield

2.2 mold expert system

in order to overcome the common bonded breakout of continuous caster and detect the heat transfer behavior of mold and the stress state of primary shell, the mold expert system developed by vatron company is adopted

the crystallizer expert system includes: (1) copper plate temperature measurement system, which uses thermocouples installed on the crystallizer copper plate to measure and transmit the copper plate temperature. There are 10 rows of thermocouples on the inner and outer arc wide sides, 2 rows of thermocouples on the left and right arc narrow sides, and a total of 44 K-type thermocouples are used. (2) Temperature data collection module. (3) Computer analysis and processing application software. (4) Visual operation interface of monitoring computer

crystallizer expert is a visual software system, which can judge the situation of the slab in the crystallizer to a certain extent by collecting, storing, analyzing and calculating the monitored crystallizer data according to a certain calculation method. The temperature distribution of the crystallizer is detected by 44 K-type thermocouples arranged on the crystallizer, and the change of heat flux of the crystallizer is calculated according to the casting speed and cooling water flow. According to the hydraulic cylinder stroke and pressure feedback of the mold vibration system, the friction between the billet and the mold copper plate is calculated. According to the characteristics of copper plate temperature rise and friction increase at the bonding place before bonding breakout, the measured temperature, friction and relevant process data are input into the prediction system through the detection device, and the breakout is predicted according to a certain judgment model, and effective measures such as reducing the drawing speed are automatically taken to prevent breakout accidents. According to the uneven distribution of heat flux when longitudinal cracks occur in the slab, the quality problems of the slab can also be judged, which plays a guiding role in production

in the production process of the caster, five breakout alarms were successfully carried out, and huge economic losses were recovered. However, if the temperature measurement thermocouple fails or the temperature measurement is not accurate, a false alarm will occur, resulting in slab joints and affecting slab quality

2.3 mold high-precision hydraulic servo vibration system

cam and eccentric mold vibration device has certain difficulty in realizing non sinusoidal vibration and adjusting amplitude, and can not really realize the optimization of mold vibration parameters in the process of continuous casting. The mold hydraulic vibration system can carry out sinusoidal vibration and non sinusoidal vibration, and has high control accuracy and stable and reliable performance. It can greatly improve the casting speed, improve the lubrication effect of the mold, effectively reduce the friction between the mold and the initial shell, reduce the strain force of the initial shell, avoid cracks and cohesive breakout, and improve the surface quality of the slab. Non sinusoidal vibration has not been used in production, and its effect is still unknown

2.4 intelligent sector soft reduction technology

intelligent sector soft reduction technology is one of the core technologies of this caster, which is composed of data acquisition system, roll gap measurement system, hydraulic cylinder control system, computer calculation and processing software, etc. It can calculate the mushy area of the slab (as shown in Figure 1) according to the actual continuous casting speed, slab thickness and steel grade, adjust the opening of the sector at any time, and gently press the slab to make the liquid core in the shell move relatively, homogenize the molten steel composition, remelt the dendrites, so as to refine the grains and reduce the central segregation, shrinkage and cracks of the slab

Figure 1 Schematic diagram of two-phase distribution of slab

the comparison in production shows that the slab segregation and shrinkage cavity are significantly reduced and the slab quality has been greatly improved by using soft reduction operation. However, the soft reduction can only operate within a certain range of drawing speed. When the temperature of molten steel is too high and the drawing speed is low, the soft reduction technology cannot be used, which is the deficiency of this technology

2.5 automatic control system of caster

Jigang No. 3 steelmaking plant has several parts, such as hot metal pretreatment, 120t converter, lf/vd refining and slab caster, which achieve the integration of three electric automatic control. As a subsystem of the whole plant system, the automatic control system of slab caster not only includes the process control level (Level 2) and the basic control level (Level 1), but also reserves the communication interface and data storage area of the production management level (Level 3) (some functions of the production management level (Level 3) have been used), which realizes the coordination of production planning, product management, technological process The whole process monitoring of mechanical and electrical equipment and other automatic production of the whole factory. As far as the continuous caster itself is concerned, it can not only realize full-automatic production, but also carry out operation conversion between automation and semi automation, which is conducive to reducing the labor intensity of workers and ensuring the normal production in case of emergency

2.6 DYNACS secondary cooling water distribution control

according to the casting speed in the production process of the caster, China Zhongwang also carried out technical cooperation with Volvo and BYD on steel grades, superheat and the actual water flow of secondary cooling water to determine the casting flow temperature distribution. According to the temperature distribution, thermal state and cooling strategy of the casting flow, the set value of the water flow of each cooling circuit of the secondary cooling water is calculated periodically, so that the thermal state of the casting flow can meet the requirements of the steel grade for the slab. It has achieved ideal results in production and application

3 trial production

the No. 1 slab caster in the Third Steelmaking Plant of Jigang was put into operation on March 1, 2003, and the first batch of billets was successfully pulled out. On May 5, the second production realized three heats of continuous casting, and on March 7, the third production successfully carried out six heats of continuous casting. Then, two shifts of small amount of trial production were carried out. On April 30, 2003, the minimum cost of three shift plastic bag production was only a few cents, and the number of continuous pouring furnaces and output gradually increased. Q235B, Q345B, jg590 and 16MnR steel grades have been produced. The main economic and technical indicators since the trial production are shown in Table 1. Table 1 Main Economic and technical indicators

monthly output/t billet qualification rate/% billet yield/% caster leakage rate/% average number of continuous casting furnaces/furnace in March 10460.7098.6894.7502.904 31698.2099.3297.9304.285 66144.6099.6997.9005.816 76350.3599.0198.1808.007 85677.4499.5998.9309.428 63316.9099.5098.93011.509 100079.199.7598.21111.929 October 103973.0298.9299.01013.40

the No. 1 continuous caster of the Third Steelmaking Plant of Jigang was put into operation for half a year Since then, the output has increased steadily month by month, the caster is running well, and the new technology has begun to show its advantages. At present, the main advanced technologies such as mold width adjustment, mold expert system, mold high-precision hydraulic servo vibration, system intelligent sector soft reduction technology, DYNACS secondary cooling water distribution control have been normally applied, which have played an important role in improving the operation rate of continuous caster and the qualification rate of slab. The mold expert system has successfully predicted the breakout for many times, avoiding the occurrence of breakout accidents, Intelligent soft reduction greatly improves the quality defects such as internal porosity and shrinkage cavity of the slab. It is believed that these new technologies will play a positive role in future product development and further improving product quality. At the same time, the successful application of these new technologies also has a certain reference for the design and production application of the new slab caster. (end)

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