Design and calculation of copper mould tube for slab continuous casting machine

Abstract: Through a series of explanations and calculations, the type, functional characteristics and design key points of the copper mould tube of the slab continuous casting machine are summarized.

Keywords: slab continuous casting; copper mould tube; cooling water volume; width adjustment device; inner cavity size

Overview

The copper mould tube is the billet forming equipment in the continuous casting machine. Its function is to force-cool the molten steel continuously injected into its inner cavity through the water-cooled copper wall, and export the heat of the molten steel so that it gradually solidifies into a cast slab with the required cross-sectional shape and a certain shell thickness. And the cast slab, whose core is still in liquid phase, is continuously pulled out from the lower mouth of the mold, creating conditions for complete solidification in the subsequent secondary cooling area. The article focuses on the mold types and functions of slab continuous casting machines, and analyzes and calculates related applications.

Copper mould tube type and structure

Type of copper mould tube

The slab copper mould tube is usually a combined type, and can be divided into arc type and vertical type according to different machine models. With the continuous development of continuous casting technology, the types of copper mould tube are also constantly updated. At present, arc-shaped copper mould tube are rarely used, while vertical-type copper mould tube are widely used.

The copper mould tube is a key equipment of the continuous casting machine. During the solidification process in which molten steel is injected into the copper mould tube and gradually forms a billet shell of a certain thickness, the copper mould tube has been bearing loads such as the static pressure and friction of the molten steel, as well as the heat transfer of the molten steel. All of these put the copper mould tube under the combined effects of mechanical stress and thermal stress at the same time, so the working conditions of the copper mould tube are extremely harsh. In order to ensure that the copper mould tube can work normally, it should meet the following basic requirements:. Good thermal conductivity, cooling capacity and wear resistance; good rigid structure, small deformation during operation; compact structure, easy to manufacture, easy to load and unload, and easy to adjust; the cooling water path can be connected by itself to meet the requirements of quick replacement.

Copper mould tube equipment composition and structural characteristics

The copper mould tube consists of inner and outer arc copper plates, back plates, inner and outer arc cooling water tanks, narrow copper plates, back plates and pressure plates, width adjustment devices, narrow edge clamping devices, wide edge foot rollers, copper mould tube cooling water, water spray piping, lubrication piping, etc to consists , as shown in Figure 1.

Figure 1 Mold structure of slab continuous casting machine

1.Wide-side foot roller assembly 2. Clamping and releasing device 3. Width-adjusting device 4. Narrow-side foot roller assembly

(1)Inner and outer arc water tanks

Both the inner and outer arc water tanks are of welded steel plate structure, and the wide copper plate is connected to the back plate through bolts and positioning pins respectively. The inner and outer arcs of the water tank body and the back plate are combined together. When the copper plate needs to be planed and repaired, the copper plate and the back plate are removed and repaired as a whole. The water tank is equipped with a water cooling channel for cooling the copper mould tube, and a water tank is opened on the surface of the copper plate that is attached to the back plate. The heat of the molten steel in contact with the wide copper plate during continuous steel casting is conducted away through the cooling water flowing in these water tanks.

The inner arc water tank is connected to the outer arc water tank through slide plates and keyways on both sides, and the sliding surface of the outer arc water tank is used as the reference plane to move based on the thickness of the blank. The inner and outer arc water tanks are held together by clamping devices.

(2) Inner and outer arc foot rollers and cooling water piping

In order to prevent the cast slab pulled out from the mold from bulging, there are three pairs of foot rollers on the inner and outer arcs of the bottom of the mold. The foot rollers have a three-segment structure and can be adjusted to meet the requirements of the roller opening. . The foot roller is connected to the inner and outer arc water tanks through long bolts, making it easy to operate in the event of a steel leakage accident or installation adjustment. Water spray pipes for cooling the slab are installed at the bottom of the inner and outer arc water tanks respectively, and the slab is cooled from both sides through nozzles.

(3) Left and right narrow side and narrow side guide devices

The left and right narrow-side copper plates are connected to the back plate through clamping plates and bolts and are connected to the pressure plate. The cooling water enters and exits from the narrow-side pressure plate. Like the wide-side copper plate, the narrow-side copper plate also has a cooling water tank to cool the copper plate.

(4) copper mould tube width adjusting device

The width adjustment device is arranged behind the left and right narrow side pressure plates, and the upper and lower sets on each side are driven by hydraulic cylinders or turbine worm transmission systems. The taper can be adjusted individually to realize automatic or manual width adjustment during online shutdown.

(5)Clamping device

The clamping devices are arranged on the inner and outer arc cooling water tanks, with two sets on the upper and lower sides. Clamped with disc spring. When adjusting the width, the four oil cylinders inside the device are supplied with system oil, and the inner arc cooling box is opened to adjust the width. After the oil cylinder is relieved, the narrow edge is clamped by the pressure of the disc spring.

(6) Various cooling water piping

The copper mould tube cooling water and slab secondary cooling water spray piping are automatically connected through the plane seal on the vibration table.

(7) Lubrication and hydraulic pressure

Related calculations of copper mould tube

Copper mould tube cooling water volume setting

The cooling water volume of the copper mould tube is divided into the wide side cooling water volume and the narrow side cooling water volume. The sum of twice the wide side cooling water volume and twice the narrow side cooling water volume is the cooling water volume of the copper mould tube.

(1) Known conditions

The maximum total water volume of a copper mould tube : 8250I/min

Maximum cooling water volume for a wide surface: 3620Vmin

Maximum cooling water volume for a narrow surface: 505l/min

The area of a wide water gap is S=7.18×10³m²=71.80cm²

The area of a narrow water gap is S=1.021×10³m²=10.21cm²

Maximum water velocity on wide surface 3620/6/71.80=8.40m/s

Maximum water velocity on narrow surface 505/6/10.21=8.24m/s

The maximum thickness of the copper plate is 45mm (the thickness of the wide and narrow copper plates is the same)

Minimum thickness of copper plate 33mm (maximum depth of sink 21mm)

(2) Setting the cooling water volume for each wide surface of the copper mould tube

For casting molds with various slab widths and copper plates of different thicknesses, the cooling water volume setting for each wide surface is shown in Table 1.

Table 1 Cooling water volume setting for each wide surface of the copper mould tube (for all slab widths)

project Copper plate thicknessCorresponding to the water volume of each wide surface of the copper mould tube in each cooling mode of secondary cooling (l/min)
Cooling method①Cooling method③Cooling method②、④
All speedVg>1.5m/minVg≤1.5m/minVg>1.5m/minVg≤1.5m/min
Qmk=45t+860Qmk=45t+790Qmk=45t+1052Qmk=45t+932
45.0     32582885281530772957
43.52818274830102890
42.02750268029422822
40.52683261328752755
39.02615254528072687
37.52548247827402620
36.02480241026722552
34.52413234326052485
33.02345227525372417
Minimum water flow vx(m/s)7.565.445.285.895.61

Note: t—copper plate thickness, mm; Qmk—water volume per wide surface, l/min; Vg—pulling speed, m/min; vx—minimum water velocity, m/s; average planned planing amount—1.5mm/ times.

(3) Setting the cooling water volume for each narrow surface of the copper mould tube

For casting molds with different slab thicknesses, the total copper plate thickness, and the cooling water volume settings for each narrow surface are shown in Table 2.

Table 2 Cooling water volume setting for each narrow surface of the copper mould tube

Slab thickness (mm)Cooling water volume for all copper plate thicknesses and all drawing speeds (l/min)
Cooling method①、②、④Cooling method③
210420390
230460430

(4) Instructions for controlling the cooling water volume of the copper mould tube

①In actual production, users can modify the water volume and formulas in Table 1 and Table 2 according to actual needs.

② The planing and repair management of copper plates should be included in the agenda of normal production and have file records to facilitate water volume setting.

③If the thickness of the wide-side copper plate after planing is not the “standard” thickness in Table 1, but is between the two thicknesses, the water volume shall be set according to the thickness of the thicker “standard” copper plate.

④The minimum thickness of copper plate is 33mm.

⑤ If the user develops a new cooling method in addition to the secondary cooling cooling methods ①~④, the user can refer to Table 1 and Table 2 and set the copper mould tube water volume by himself based on production experience.

Copper mould tube cavity size and spindle width size

(1) The width of the mold cavity and the width of the spindle head

The width of the inner cavity of the copper mould tube is obtained by adjusting it. See Table 3 for its calculation and setting values.

Table 3 copper mould tube cavity width and spindle width

Nominal width of billet Bb (mm)MD lower opening width B (mm)MD upper opening width A (mm)Single side taper(A-B)/2(mm)Width of spindle head (mm)The clearance between the spindle head and the MD lower port on each side (mm) Remark
speed≤1.2 m/minspeed>1.2 m/minspeed≤1.2 m/minspeed>1.2 m/min
9509609699684.54.09476.51. When the billet thickness is 210mm, the thickness of the dummy head is 205mm.2. When the billet thickness is 230mm, the thickness of the dummy head is 225mm.3. The width of the narrow foot roller is the same as the width of the MD lower opening.4.MD is the code name of the copper mould tube.5. Lower opening size B=1.011×Bb6.TaperIn the formula: h—copper mould tube length, h=0.9 m7. When the pulling speed is ≤1.2m/min, △=1.0%/m; when the pulling speed is >1.2 m/min, A=0.9%/m8.A and B allowable deviation ± 0.2mm9. The allowable deviation of single-sided taper is ±0.2mm.
10001011102010194.54.09977.0
10501062107210715.04.510477.5
11001112112211215.04.510977.5
11501163117311725.04.511497.0
12001213122412235.55.011997.0
12501264127512745.55.012497.5
13001314132613256.05.512997.5
13501365137713766.05.513498.0
14001415142814266.55.513998.0
14501466147914786.56.014498.5
15001517153115297.06.015018.0
15501567158115807.06.515518.0
16001618163316317.56.516018.5
16501668168316827.57.016518.5

2) Narrow surface dimensions of the mold cavity

The narrow surface dimensions of the mold cavity are guaranteed by processing, see Table 4.

Table 4 Narrow surface dimensions of the mold cavity

copper mould tube part Slab thickness (mm)
210230
Upper mouth (mm)217.4237.8
Lower opening(mm)216.0236.4
Wide foot roller (mm)216.0236.4

Conclusion

In summary, the above items are the main steps in the design of the slab continuous caster mold, and have been applied and improved in the design process of a series of products of our company. The copper mould tube is an important part of the daily production of the continuous casting machine and the heart of the continuous casting machine. Its performance plays a vital role in improving continuous casting productivity, maintaining normal production in the continuous casting process, and ensuring the quality of the cast slab. Correct selection of copper mould tube structure and parameters can ensure safer equipment operation.

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