Blast furnace cooling stave casting paper


1. Summary

The cooling stave is an important component in the cooling system of the blast furnace. It is installed in the furnace body, furnace waist, furnace belly, furnace cylinder and other parts of the blast furnace. It has the important functions of supporting refractory materials, cooling the furnace shell, and maintaining a reasonable furnace shape. The cooling stave not only bears high temperature, but also bears the abrasion of the furnace charge, the erosion of molten slag and the scouring of gas flow, must have good thermal strength, thermal shock resistance, resistance to quenching heat and other comprehensive performance. The cooling wall can effectively prevent the furnace shell from being heated and red. After the lining brick of the blast furnace is corroded, the cooling wall itself is mainly protected by slag skin, and the safe production of the blast furnace is maintained. Therefore, the material and performance of the cooling stave determine its working life and even the life of the blast furnace body. The production situation of iron and steel enterprises at home and abroad proves that one of the keys to the longevity of the blast furnace is to realize the longevity of the cooling wall.

2. product structure

The cooling stave is a long strip plate-shaped part, which is composed of the cooling stave body and the cooling water pipe cast in the inside. Each serpentine pipe is formed by mechanically cold bending the whole steel pipe. For the steel pipe with serious corrosion and pits, it cannot be used as the cast-in pipe. The serpentine pipe shall be bent and formed according to the relevant drawings, and the bending radius deviation is allowed as follows2mm, the thinning of the pipe wall caused by the elbow should be less than 20% of the wall thickness, and the deviation of the center line of the inlet and outlet of the water pipe is allowed to be 2mm.

3. considerations

1. Size control in bending process of cooling water pipe
1) Appropriate water pipe shrinkage
During the pouring process, the steel cooling water pipe cast into the cooling wall will expand due to heat during the high temperature pouring process, and with the decrease of temperature, the cast steel cooling water pipe will shrink accordingly, so it is necessary to determine its scale before bending. The size of the scale, that is, the ratio of the difference between elongation and shrinkage and the original length, will directly affect the accuracy of the casting size.
a. The scale in the length direction of the cooling water pipe is generally half of the scale of the casting;
B. The transverse spacing shrinkage of the inlet and outlet of the cooling water pipe is the same as that of the casting body;



2) The "uniform distribution technology" is adopted between the protective pipe and the water pipe"

Two fixed rings are used between the protective pipe and the water pipe, and buffer materials such as asbestos rope and asbestos felt are filled between the fixed rings to ensure that the water pipe and the protective pipe are concentric and have a certain buffer amount.

2、Process considerations

(1)The steel pipe in the cooling wall has a chilling effect during pouring, the pouring temperature cannot be too low, and the pouring speed cannot be too slow;

(2)Prevent molten iron from impacting the pipe wall and avoid steel pipe deformation and surface carburization;

(3)Because the size of the thickest and thinnest parts of the cooling stave is quite different, it is necessary to prevent the thick part from overheating.

4. process design

1. The overall dimensions of the product are 1608mm × 909mm × 959mm, the single weight of the casting is 2.5T, and the material is HT150, which is used for 350m blast furnace.

2、Bending of cooling water pipes

(1)Cooling water pipe is adoptedφ34*4.5 seamless steel pipe shall be pickled in 30% dilute HCL pool before bending to remove oxide scale and impurities inside and outside the pipe. 6~8kg/C㎡The water pressure is tested and the pressure is maintained.20~30 minutes, the pipe shall not leak or sweat.

 

(2)In order to minimize the deformation of the cooling water pipe in the bending process, we adopted the cold bending method, which avoids the phenomenon that the hot bending oxidizes the bending part of the cooling water pipe and makes the pipe wall thinner. At the same time, it is required that the bending part is not allowed to have wrinkles, concave deviation, peeling and scars. The bent cooling water pipe shall be subjected to ball passing and hydraulic pressure test, and shall be painted after passing the test.0.2~0.3mm thick anti-carburizing coating can be cast after drying.

3、White die cutting and bonding

The white mold structure required by the cooling wall is relatively complex and is not suitable for mass production through the molding machine, so it is completed by automatic cutting table and manual bonding. Use automatic cutting table to cut the cooling wall in layers, fill the cooling water pipe and repair it by manual bonding.

4、gating system design

 

The bottom injection type pouring system is adopted.∑SInside∑STransverse∑SStraightFor1:1.2:1.4 (in SInsideIn order to block the flow, the pouring system is filled quickly, and the flow rate of liquid metal in the cross runner is high), the diameter of the direct runner is50mm round runner, runner 40mm x 40mm, gate for six 25mm x 10mm. The gating system is bonded after the third paint brush.

5. production operation

1. White mold rinse coating

1) When brushing the paint for the first time, mix the paint and water according to the ratio of 1:0.6, pour the measured water into the mixing bucket, start the mixer, slowly pour the paint (the whole bag needs to be poured completely) under the working state of the mixer, stir for more than 2h, the paint is uniform and free of dead pieces, and after measuring the paint density (Baomeidu 60-65), pour the paint into the coating tank and let stand for 5 minutes, can be used, the first coating should not be too thick, so as not to cause surface cracking during drying, affecting the quality of castings. Due to the large size of the casting, the brush coating method is adopted.

Put the yellow mold with good group shape and uniform coating of the model into the drying room, and the distance between the two models is greater150mm, the drying room adopts electric heating method, the temperature of the drying room is controlled at about 45 ℃, the temperature should not be too high, it has caused the yellow mold edge corner cracking, humidity is lower than 15%, the yellow mold should not be directly blown by the drying heater, so as not to cause the yellow mold to heat too high, causing the coating edge corner cracking. Drying in this environment for about 8 hours, at this time the coating thickness of 0.4-0.6mm.

2) The second time the paint is more dense than the first time (Baume 68-70). The model after the first drying is painted, and the operation process repeats the first process. The thickness of the coating layer reaches between 1.0-1.5mm after drying. After brushing, it shall be transported to the drying room and placed separately from the yellow mold after brushing. The second drying time is 12 hours.

3) The third brushing, repeat the second process, after three brushing, the pattern is evenly coated, there is no lack of coating, flow or inclusion of bubbles, drying time must be greater than 24 hours. Weighing can be used to detect whether drying.

2. Modeling of buried box

Adopt30-40 purpose treasure pearl sand, bottom sand thickness 300mm, first shake the bottom sand, vibration time 50-60 seconds, and then put the model in place, at least not less than 150mm from the outer wall of the sand box, bonding straight runner, the second vibration, vibration 30-40 seconds, full vibration, time should not be too long, to avoid vibration crack white mold.

After the second earthquake, add sand to the upper plane of the pouring cup for the third vibration compaction. Then the upper plastic thin mold (3-5 silk), plus top sand. In order to prevent the molten iron from washing the sand around the gate cup into the casting during pouring, alcohol coating is applied around the gate to prevent sand washing.

3. Pouring

The temperature of the furnace is controlled1510 ℃ ~ 1530 ℃, pouring temperature is 1400 ℃ ~ 1420 ℃ (melting point of cooling steel pipe is above 1460 ℃), negative pressure degree is -0.05MPa, pouring speed is 50~65 kg/s, pouring time is 40~50 seconds, pressure is maintained at-0.02MPa negative pressure degree for 15 minutes after pouring, and the box is turned over after heat preservation for 3~5 hours.

4, shot blasting to clean the casting, the finished product needs to go through 5kg/C㎡Hydrostatic test, pressure resistanceDo not leak or sweat for 20 minutes.

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