CN113798451B - A Copper Alloy Horizontal Continuous Casting Mold - Google Patents

Abstract

The invention discloses a copper alloy horizontal continuous casting crystallizer, which comprises a graphite mold and a cooling copper sleeve set outside the graphite mold, and is characterized in that the graphite mold comprises an upper graphite plate, a lower graphite plate and an upper graphite The left graphite plate and the right graphite plate between the graphite plate and the lower graphite plate, the upper graphite plate, the lower graphite plate, the left graphite plate and the right graphite plate are enclosed to form a cavity through the front and rear, the upper graphite plate, the lower graphite plate The thermal conductivity of the graphite plate is a, the thermal conductivity of the left graphite plate and the right graphite plate is b, and the range of b/a is 0.45-0.65. The present invention adopts graphite plates with different thermal conductivity to form a graphite cavity, so as to ensure that the edge and middle outlet temperature deviation of the upper and lower surfaces of the drawn cast slab is less than or equal to 30°C, ensure uniform structure of the slab, and prevent serious deformation of the copper sleeve.

Description

A Copper Alloy Horizontal Continuous Casting Mold

technical field

The invention belongs to the technical field of copper alloy crystallizers, in particular to a copper alloy horizontal continuous casting crystallizer.

Background technique

In the copper processing industry, horizontal continuous casting is mostly used in the production of tin phosphor bronze and zinc white copper. There is a long-term difficult technical problem: in the horizontal continuous casting process, there is uneven cooling intensity in both the width direction and the thickness direction of the slab. , resulting in the disorder of the slab structure after solidification. For horizontal continuous casting strips, the cooling intensity at the edge is greater than that at the middle, especially for large and wide strips over 600mm, the cooling intensity between the edge and the center is significantly different, mainly in the strip outlet temperature, surface color and thickness In terms of bias, internal organization also has an impact. Taking tin phosphor bronze as an example, the outlet temperature of the center is higher than that of the edge, the color is darker than the edge, it is easy to turn red and black, the middle thickness is concave than the edge, and the size of the tissue is irregular, and the edge is smaller than the center, which directly affects The plate shape and yield of subsequent processing; and for the solidification process in the thickness direction of the slab, due to gravity, the upper surface of the slab solidifies and shrinks to form a gap with the crystallizer, and the cooling intensity of the upper and lower surfaces is different. Affect the offset of the center line of the cross-section of the slab, resulting in uneven and irregular grains, and in severe cases, cracks will occur on the surface or inside of the slab.

The problem of uneven cooling in the horizontal continuous casting process mainly comes from the uneven cooling intensity of the mold. A general horizontal continuous casting crystallizer usually includes a cooling copper sleeve and a graphite mold. From the inside to the outside, there are graphite molds and cooling copper sleeves. The entire heat transfer process is just the opposite. The heat of the copper water is transferred to the graphite mold, and the graphite mold conducts heat to the cooling copper sleeve. , The cooling copper sleeve is filled with cooling water, which plays a cooling role and takes away heat. Therefore, the cooling effect of the graphite mold and the cooling copper jacket directly affects the microstructure uniformity of the horizontal continuous casting slab.

For example, the invention patent CN111974955A discloses a cooling horizontal continuous casting crystallizer, which is designed with a plurality of water tanks inside. The crystallizer has a good cooling effect during use. The surface and the graphite mold are in direct surface contact, which improves the thermal conductivity, improves the cooling effect of the copper water, and prolongs the life of the crystallizer. However, this crystallizer design method cannot guarantee the same cooling effect between the edge and the center for the wide-width strip blank above 600mm. , cooling uniformity needs to be improved.

Invention patent CN102248138 A discloses a horizontal continuous casting crystallizer that realizes uniform cooling in the circumferential direction. The crystallizer is designed with multiple independent cooling water chambers. By adjusting the cooling water flow, pressure, and cooling water temperature parameters of each cooling water chamber , can effectively improve the uneven cooling phenomenon in the horizontal continuous casting process and improve the quality of continuous casting slabs, but this mold design method is only suitable for horizontal continuous casting of ring-shaped and small-width slabs.

Therefore, how to optimize the structure and heat exchange capacity of the crystallizer to obtain a uniform cooling effect, consistent outlet temperature and uniform structure at the middle and edge positions in the width direction of the slab, and improve the quality of the horizontal continuous casting slab is the level The main research direction of continuous casting mold.

Contents of the invention

The invention provides a copper alloy horizontal continuous casting crystallizer. The first technical problem to be solved is to keep the cooling intensity uniform in the width and thickness directions of the horizontal continuous casting slab, realize uniform as-cast structure and good quality of the slab.

The technical solution adopted by the present invention to solve the first technical solution is: a copper alloy horizontal continuous casting crystallizer, including a graphite mold and a cooling copper sleeve set outside the graphite mold, characterized in that: the graphite mold includes an upper A graphite plate, a lower graphite plate, and a left graphite plate and a right graphite plate arranged between the upper graphite plate and the lower graphite plate, the upper graphite plate, the lower graphite plate, the left graphite plate and the right graphite plate form a front-to-back through In the cavity, the thermal conductivity of the upper graphite plate and the lower graphite plate is a, the thermal conductivity of the left graphite plate and the right graphite plate is b, and the range of b/a is 0.45-0.65.

The graphite mold is in direct contact with the slab. In order to obtain a smaller cooling difference between the sides and the middle of the slab, graphite plates with different thermal conductivity are used. When b/a is greater than 0.65, the cooling intensity at the edge is much greater than that at the middle, which easily leads to serious deformation of the copper sleeve and is not conducive to the uniform distribution of the slab structure; when the edge b/a is less than 0.45, the cooling intensity at the middle is greater than that at the edge. The edge of the slab is prone to cracking. The range of b/a is 0.45 ~ 0.65, to ensure that the temperature deviation of the edge and middle outlet of the drawing casting slab is less than or equal to 30°C, to ensure the uniform structure of the slab, and to prevent serious deformation of the copper sleeve. Strictly control the edge and middle position of the graphite mold cooling intensity.

As a preference, the upper surface of the upper graphite plate and the lower surface of the lower graphite plate are provided with slots for the passage of cooling gas, the slots are provided along the width direction of the graphite mould, and the cooling copper sleeve is provided with slots for the passage of cooling gas. Cooling air is directed into the slotted intake holes. In order to increase the cooling intensity during the crystallization process, helium gas treatment is carried out between the graphite mold and the cooling copper sleeve to improve the heat conduction effect. The heat transfer form of the graphite mold and the cooling copper sleeve is radiation heat transfer. By passing the gas with high thermal conductivity between the graphite mold and the cooling copper sleeve, the heat transfer capacity of the two can be significantly improved, and the cooling effect can be improved. The graphite plate and the lower graphite plate are opened in the width direction to ensure the uniform structure of the billet in the width and improve the quality stability in the width direction.

Preferably, the slot has a width of 5-20 mm and a depth of 0.5-2 mm, and the slot is 100-200 mm away from the copper water inlet side, and 50-100 mm away from the edge of the upper graphite plate and the lower graphite plate. When the width of the groove is greater than 20mm and the depth is greater than 2mm, it is not conducive to the diffusion and coverage of the cooling gas, and local overcooling is prone to occur, resulting in uneven tissue; when the width of the groove is less than 5mm and the depth is less than 0.5mm, the cooling gas will flow If the amount is too small, it can't play a significant heat conduction effect, and the effect is not great. In the horizontal continuous casting process, the copper water enters the crystallizer and solidifies in the cavity. The crystallization position directly depends on the cooling effect of the graphite plate, which also affects the uniformity of the slab crystal structure. In general, in order to facilitate the drawing and crystallization of the slab, the crystallization position is slightly closer to the inlet side of the copper water. According to the crystallization position and liquid cavity shape, when the slotting position is less than 100mm from the copper water inlet side and less than 50mm from the upper and lower graphite plate edges, the copper water crystallization position is too far ahead of the copper water inlet side, and the cooling is advanced, which is not conducive to billet drawing Casting, it is easy to pull and not move; when the distance from the slot to the copper water inlet side > 200mm, and the distance from the graphite plate edge > 100mm, the copper water crystallization position is too deep, the crystallization time is insufficient, and it is easy to pull and leak. Therefore, the width of the slot is 5-20 mm, the depth is 0.5-2 mm, the slot is 100-200 mm away from the copper water inlet side, and 50-100 mm away from the edge of the upper graphite plate and the lower graphite plate.

Preferably, the groove includes a wave-shaped groove and straight grooves located at both ends of the wave-shaped groove, the amplitude P of the wave-shaped groove is 50-85 mm, the wavelength λ of the wave-shaped groove is 50-75 mm, and the length of the straight groove is 60-85 mm. 85mm.

The crystallization positions of the drawn ingots are distributed in a crescent shape along the width direction of the graphite mold, indicating that the temperature distribution of the drawn ingots along the width direction is gradient, forming an arc instead of a straight line, which is consistent with the liquid cavity shape of copper water, heat dissipation direction and so on. The middle position of the groove is wave-shaped, covering the temperature gradient distribution range with an amplitude of 50-85mm, which is conducive to the flatness of the liquid cavity. When the amplitude is less than 50mm, the crescent-shaped range of the liquid cavity cannot be covered, and uniform cooling of the crystallization position cannot be guaranteed, and tissue spacing is prone to occur, resulting in cracking in subsequent rolling; when the amplitude is greater than 85mm, the range of cooling positions is too large, and the slab Frictional contact with the graphite plate after forming is not conducive to the life of the graphite plate, and the graphite plate will be cracked in severe cases;

The size control of the wavelength directly affects the cooling intensity in the middle of the graphite plate, which determines the growth rate of the thickness of the solidified shell during the solidification process, thereby determining the shape of the liquid cavity and the uniformity of the slab structure. When the wavelength is less than 50mm, the distribution of wave grooves is too dense, and the cooling intensity in the middle part is much greater than other positions after ventilation, resulting in uneven tissue; when the wavelength is greater than 75mm, the distribution of wave grooves is too evacuated, the cooling coverage of heat transfer gas becomes narrow, and the cooling force is weak , with the rhythm of pulling and stopping, it is easy to have obvious gaps in the grain size of the structure, and cracks in the subsequent rolling in severe cases; in addition, when the length of the straight groove is less than 60mm, the distance between the straight groove and the edge is too far, and the helium coverage area of the distance is limited , cannot fully guarantee uniform cooling intensity; when the length of the straight groove is greater than 85mm, the straight groove is too close to the edge, which will increase the cooling intensity of the edge, resulting in a large cooling difference;

Preferably, the cooling gas is helium, the pressure of the helium is 0.35-0.55 MPa, and the flow rate is 10-60 ml/min. The heat transfer efficiency of the gas is strongly affected by the pressure and flow rate. When the pressure of helium is greater than 0.55MPa and the flow rate is greater than 60ml/min, the helium is easy to dissipate, the actual cooling effect is not strong, and the production consumption is large and the cost is high; when helium When the pressure is less than 0.35MPa and the flow rate is less than 10ml/min, the heat transfer efficiency of helium is not obvious.

Preferably, the helium pressure ratio of the upper graphite plate and the lower graphite plate satisfies 1.0-1.2, and the flow rate ratio satisfies 1.0-1.2. During the horizontal continuous casting process, the self-weight of the copper water affects the shape of the liquid cavity, the direction of heat dissipation, and the volume shrinkage during solidification, resulting in a "crescent" gap in the upper part of the ingot, which makes the heat dissipation conditions of the upper part of the ingot worse. The cooling effect of the upper surface of the billet is weaker than that of the lower surface. Therefore, the uniformity of cooling in the thickness direction of the slab can be achieved by adjusting the pressure and flow rate of helium fed into the upper and lower graphite plates. When the helium pressure ratio and flow ratio of the upper and lower graphite plates are less than 1.0, the cooling intensity of the lower surface in the thickness direction of the slab is greater than that of the upper surface, which is likely to cause the center line of the cross-section of the slab to be upward, and the crystal grains on the lower surface are obvious. If it is larger than the upper surface, cracking will easily occur in the subsequent rolling process due to uneven stress in severe cases; when the helium pressure ratio and flow ratio of the upper and lower graphite plates are greater than 1.2, the cooling strength of the upper surface in the thickness direction of the slab is greater than On the lower surface, it is easy to cause the center line of the cross-section of the slab to be lower, and the grains on the upper surface are obviously larger than the lower surface. In severe cases, cracking problems are also prone to occur.

Compared with the prior art, the present invention has the advantages of:

1. The graphite cavity is composed of graphite plates with different thermal conductivity to ensure that the edge and middle outlet temperature deviation of the upper and lower surfaces of the cast slab is less than or equal to 30°C, ensuring uniform structure of the slab and preventing serious deformation of the copper sleeve;

2. Cooling gas is passed between the graphite plate and the copper sleeve to replace the traditional flexible graphite paper or graphite powder, which fully compensates for the uneven cooling defect caused by the loose contact surface between the graphite plate and the copper sleeve, and at the same time reduces It complies with the operation requirements of installation, facilitates mold installation, and can reduce the risk of poor quality of billets caused by improper installation;

3. Design the wave groove on the back of the graphite plate according to the shape of the liquid cavity during the solidification process of the copper water, so as to give full play to the heat conduction effect of the cooling gas. The wavelength and amplitude of the wave groove can control the cooling intensity in the width direction of the graphite plate to obtain a uniform structure and make up for the uneven structure caused by the edge cooling intensity being greater than the center in traditional horizontal continuous casting.

4. The average grain size on the surface of the drawn cast slab obtained in the present invention is controlled at 2-4mm, and the average grain size deviation at different positions on the surface is ≤0.4mm, and the centerline position is centered.

Description of drawings

Fig. 1 is the structural representation of the embodiment of the present invention;

Fig. 2 is a schematic structural diagram of a slot in an embodiment of the present invention.

detailed description

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

Referring to FIG. 1 to FIG. 2 , a preferred embodiment of a copper alloy horizontal continuous casting crystallizer is shown, including a graphite mold 10 , a cooling copper jacket and a slot 5 .

The graphite mold 10 comprises an upper graphite plate 1, a lower graphite plate 2 and a left graphite plate 3 and a right graphite plate 4 arranged between the upper graphite plate 1 and the lower graphite plate 2, the upper graphite plate 1, the lower graphite plate 2, the left graphite plate The plate 3 and the right graphite plate 4 are enclosed to form a cavity 1a that runs through front and back. The thermal conductivity of the upper graphite plate 1 and the lower graphite plate 2 is a, and the thermal conductivity of the left graphite plate 3 and the right graphite plate 4 is b.

Slots 5 are opened on the upper surface of the upper graphite plate 1 and the lower surface of the lower graphite plate 2 for the passage of cooling gas, and the slots 5 are opened along the width direction of the graphite mold 10 .

The cooling copper sleeve is set on the outside of the graphite mold 10, and the cooling copper sleeve is provided with an air inlet for the cooling gas to pass into the slot 5.

The alloys of the four examples are selected, and the composition design is shown in Table 1. Casting is carried out according to the crystallizer design of this embodiment, and the crystallizer parameter design is shown in Table 2. The casting parameters of the alloys in the examples are: the casting speed is 100-150mm/min, the casting temperature is 1160-1190°C, the helium control parameters are shown in Table 3, the casting method adopts pull-stop-pull, and the ingot specification is 16.5× 650mm.

The composition of the comparative example is the same as that of Example 1. The difference between the crystallizer used in the comparative example and the crystallizer of this embodiment is that the graphite plates on the upper, lower, left and right have the same thermal conductivity, and there are no slots and cooling copper sleeves There is no air intake hole on it, and the specific parameters are shown in Table 2. The casting parameters of the comparative example are the same as those of Example 1.

For the prepared slabs of 4 examples and comparative examples, the surface color comparison and the straightness test of the crystallization line were carried out. Three points were taken at equal intervals along the width direction of the slabs on the upper and lower surfaces of the slabs, starting from the left To the right are A, B, and C in turn. Test the outlet temperature of the upper and lower surfaces and the grain size and uniformity of the surface structure of the slab. At the same time, test the columnar grain length of the cross-sectional metallographic structure and the position of the centerline of the cross-section. The specific test The results are shown in Table 4 and Table 5.

The average grain size of the macroscopic metallographic structure is tested according to the inspection requirements in "YS/T 448-2002: Macrostructure Inspection Method of Copper and Copper Alloy Casting and Processed Products". Grain size was tested. The sample width is 20mm and the length is 20mm.

For the microstructure uniformity test at different positions in the width direction of the slab, take the maximum and minimum values among the three points A, B, and C, and use the difference between the maximum and minimum values to represent the microstructure uniformity.

The graphite mold of the present invention adopts four combined graphite plates with different thermal conductivity for drawing casting, and the outer surfaces of the upper and lower graphite plates are provided with slots for cooling gas, in order to improve the cooling between the cooling copper sleeve and the graphite plate. The effect is to increase the cooling intensity. This design makes the slab structure tend towards uniformity, so the segregation degree and the slab quality of the high-tin content tin phosphor bronze slab surface are improved, and defects such as cracks are reduced; by the results of Table 4 and Table 5, it can be concluded that the crystallizer of the present invention uses The structure of the upper and lower surfaces of the alloy is uniform, the surface crystal lines are smooth and uninterrupted curves, the surface color is light yellow, the temperature difference between the edge and the middle of the upper and lower surfaces is controlled to be less than 20°C, the average surface grain size is controlled to 2-4mm, and the width of the slab is The size difference of surface grains at different positions on the surface is less than or equal to 0.4mm, the structure is uniform, and the centerline is in the middle, and the length of columnar crystals is 7-8mm. The slab structure is evenly distributed, which improves the quality of the slab, so it has a good value for popularization and application.

The comparative example uses a conventional crystallizer. Due to the cooling of the edge of the slab before the middle position, the gap caused by its own gravity, and whether the installation of the graphite plate and the copper sleeve is tightly fitted, etc., the crystal lines on the surface of the slab are interrupted, tortuous, and the surface color Red and black, the temperature of the upper and lower surfaces is greater than 50°C, and the size of the upper and lower surface structures is uneven, the average grain size is 0.5-2mm, and the size of the grains is distributed at intervals. On the high side. The structure of the slab is uneven, or the size of the structure is distributed at intervals, and the problem of rolling cracking is prone to occur in the subsequent processing process.

The composition of table 1 embodiment and comparative example

The relevant parameter of the crystallizer that table 2 embodiment of the present invention and comparative example adopt

The helium gas feeding parameter control of table 3 embodiment of the present invention

Table 4 embodiment of the present invention and comparative example slab surface test result

Table 5 embodiment of the present invention and comparative example slab surface test result

Claims (3)

1. The utility model provides a horizontal continuous casting crystallizer of copper alloy, includes graphite jig (10) and overlaps the cooling copper sheathing of establishing in graphite jig (10) outside, its characterized in that: the graphite mould (10) comprises an upper graphite plate (1), a lower graphite plate (2), and a left graphite plate (3) and a right graphite plate (4) which are arranged between the upper graphite plate (1) and the lower graphite plate (2), wherein the upper graphite plate (1), the lower graphite plate (2), the left graphite plate (3) and the right graphite plate (4) are enclosed to form a cavity (1 a) which is through from front to back, the heat conductivity coefficients of the upper graphite plate (1) and the lower graphite plate (2) are a, the heat conductivity coefficients of the left graphite plate (3) and the right graphite plate (4) are b, and the range of b/a is 0.45-0.65; the upper surface of the upper graphite plate (1) and the lower surface of the lower graphite plate (2) are provided with grooves (5) for introducing cooling gas, the grooves (5) are formed along the width direction of the graphite mold (10), and the cooling copper sleeve is provided with an air inlet hole for introducing the cooling gas into the grooves (5); the width of the open slot (5) is 5-20 mm, the depth is 0.5-2 mm, the open slot (5) is 100-200 mm away from the copper water inlet side, and is 50-100 mm away from the edges of the upper graphite plate (1) and the lower graphite plate (2); the slotting (5) comprises a wave-shaped groove (51) and straight grooves (52) positioned at two ends of the wave-shaped groove (51), the amplitude P of the wave-shaped groove (51) is 50-85 mm, the wavelength lambda of the wave-shaped groove (51) is 50-75 mm, and the length of the straight groove (52) is 60-85 mm.

2. The copper alloy horizontal continuous casting crystallizer of claim 1, wherein: the cooling gas is helium, the pressure of the helium is 0.35-0.55 MPa, and the flow rate is 10-60 ml/min.

3. The copper alloy horizontal continuous casting crystallizer of claim 2, wherein: the helium pressure ratio of the upper graphite plate (1) to the lower graphite plate (2) meets 1.0-1.2, and the flow ratio meets 1.0-1.2.

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