Ingot pulling method for improving surface casting quality of EB blank

Abstract

The invention discloses an ingot pulling method for improving the surface casting quality of an EB blank, and belongs to the technical field of titanium and titanium alloy machining. The method comprises a descending stage in which a dummy bar drives a cast ingot to descend relative to a crystallizer and a static stage in which the cast ingot is static relative to the crystallizer, in a cycle formed by the descending stage and the static stage, an ascending stage is added at least before the descending stage, and in the ascending stage, the dummy bar drives the cast ingot to ascend relative to the crystallizer; taking the ascending direction of the cast ingot relative to the crystallizer as a positive direction, taking an ascending stage before a descending stage as a first stage, taking a corresponding displacement L1 and the descending stage as a second stage, taking a corresponding displacement L2 and a static stage as a fourth stage, taking a corresponding displacement L4, taking an ascending stage possibly existing between the descending stage and the static stage as a third stage, and taking a corresponding displacement L3; l1 > 0, L2 < 0, L3 > = 0, L4 = 0, and L2 > (L1 + L3). And the surface quality and defect grinding efficiency of the EB blank can be remarkably improved, the peeling depth of the EB blank is reduced, and the yield is increased.

Description

Technical Field

[0001] This invention relates to the field of titanium and titanium alloy processing technology, and specifically to a casting method for improving the surface casting quality of EB billets. Background Technology

[0002] Titanium and titanium alloys possess significant advantages such as low density, high specific strength, and strong corrosion resistance, making them widely used in aerospace, marine engineering, petrochemicals, and weaponry. The electron beam cold hearth furnace (EB furnace) smelting method, with its excellent impurity removal capabilities, short process, low cost, and ability to melt and cast ingots in a single step, has attracted widespread attention from domestic titanium smelting and processing enterprises.

[0003] In the EB furnace smelting process, the raw materials are first melted into a liquid state under the bombardment of a high-energy electron beam. The molten titanium flows through a refining cooling bed to remove high- and low-density inclusions before flowing into a crystallizer and being cast into titanium ingots. Depending on the crystallizer specifications, the EB furnace can directly cast flat or round titanium ingots. The EB furnace ingot pulling process, as one of the core technological steps in titanium and titanium alloy smelting, directly determines the surface quality and yield of the finished ingot. The EB furnace ingot pulling process involves the ingot being driven downwards relative to the crystallizer by a guide rod, then remaining stationary for a period of time, and this process is repeated. The EB furnace ingot pulling process belongs to a vertical semi-continuous casting mode. Compared to the continuous casting process in steelmaking, it features a lower ingot pulling speed (3-20 mm / min), no crystallizer vibration, no protective slag lubrication, and a higher coefficient of friction between the titanium ingot and the crystallizer (0.3-0.5). These characteristics make the EB furnace ingot pulling process prone to surface defects such as cold shuts, overflows, corner cracks, porosity, and wide transverse cracks, which seriously affect the surface quality of the finished ingot. Currently, due to limitations in surface quality, the peeling depth of EB billets is typically between 8-12mm, and the grinding of defects takes 6-10 hours, resulting in a yield loss of 8-12%, which seriously affects the company's profitability. Summary of the Invention

[0004] To overcome the problems of poor surface quality of existing EB billets, resulting in large peeling depth, low efficiency in defect grinding, and low yield, this invention provides a casting method for improving the surface casting quality of EB billets.

[0005] The technical solution adopted by this invention to solve its technical problem is: A method for improving the surface casting quality of EB billets includes a downward phase in which the ingot is driven downward relative to the crystallizer by a dummy rod, and a stationary phase in which the dummy rod is stationary and the ingot is stationary relative to the crystallizer. The downward and stationary phases are repeated. In a cycle consisting of the downward and stationary phases, an upward phase is added at least before the downward phase. In the upward phase, the dummy rod drives the ingot upward relative to the crystallizer. Taking the direction of the ingot's upward movement relative to the crystallizer as the positive direction, the upward phase before the downward phase is the first phase, corresponding to a displacement L1; the downward phase is the second phase, corresponding to a displacement L2; the stationary phase is the fourth phase, corresponding to a displacement L4; and the possible upward phase between the downward and stationary phases is the third phase, corresponding to a displacement L3. A new cycle is formed from the first to the fourth phase. L1 > 0, L2 < 0, L3 ≥ 0, L4 = 0, and |L2| > (L1 + L3).

[0006] In this application, by introducing an upward phase into the movement of the EB furnace ingot derrick, a "negative slippage" effect, similar to that in continuous casting, is achieved during the EB furnace melting and casting process. This significantly improves the surface quality and defect removal efficiency of the EB billet, reduces the peeling depth of the EB billet, and increases the yield.

[0007] In some embodiments, the melting rate is Q, in kg / min, and the density of the molten titanium is ρ, in kg / m³. 3 The length of the crystallizer is L, in meters; the width of the crystallizer is B, in meters; and the time for pulling the ingot in one cycle is T, in seconds. The net drawing length corresponding to one cycle is ΔL, where ΔL = |L2| - (L1 + L3). T0 = ​​(ρ*L*B*△L*0.06) / Q, and the range of the pulling time T is 0.95T0-1.05T0.

[0008] In some embodiments, both L1 and L3 are less than or equal to 20 mm.

[0009] In some embodiments, the following process is included: In the initial stage of ingot pulling, molten titanium liquid flows into the dovetail groove of the crystallizer to form a bottom layer; After the bottom layer is laid, the dummy bar drives the ingot casting action, which includes multiple ingot pulling actions consisting of new cycles; After the spinning process is completed, the spindle is cooled and removed from the container.

[0010] The beneficial effects of this invention are: By introducing an upward phase into the EB furnace ingot derrick operation, a "negative slip" effect, similar to that in continuous casting, is achieved during the EB furnace melting and casting process. This significantly improves the surface quality and defect removal efficiency of the EB billet, reduces the peeling depth of the EB billet, and increases the yield. Attached Figure Description

[0011] Figure 1 A schematic diagram of the EB furnace structure used in the ingot pulling method provided by the present invention; Figure 2 for Figure 1 A top view of the structure of a rectangular crystallizer; Figure 3 This is a schematic diagram of the movement state of the ingot pulling rod in the ingot pulling method for improving the surface casting quality of EB billets provided by the present invention.

[0012] The diagram is labeled as follows: 1-Crystallizer; 2-Ingot; 3-Dovetail groove; 4-Ingot guide rod; 5-Titanium molten pool; 6-First-stage displacement; 7-Second-stage displacement; 8-Third-stage displacement; 9-Fourth-stage displacement. Detailed Implementation

[0013] The invention will be further described below with reference to the accompanying drawings.

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0015] like Figures 1-3 As shown, the present invention provides a casting method for improving the surface casting quality of EB billets.

[0016] The ingot pulling method for improving the surface casting quality of EB billets includes a downward phase in which the ingot 2 is driven downward relative to the crystallizer 1 by the ingot puller 4, and a stationary phase in which the ingot puller 4 is stationary and the ingot 2 is stationary relative to the crystallizer 1. The downward phase and the stationary phase are repeated. In a cycle consisting of the downward phase and the stationary phase, at least an upward phase is added before the downward phase, in which the ingot puller 4 drives the ingot 2 upward relative to the crystallizer 1.

[0017] Reference Figure 1 and Figure 3 As shown, taking the upward direction of ingot 2 relative to crystallizer 1 as the positive direction, the upward stage before the downward stage is the first stage, corresponding to a displacement L1, that is... Figure 3 The first stage is displacement 6; the downward stage is the second stage, corresponding to displacement L2, which is also the second stage displacement 7 in the figure; the stationary stage is the fourth stage, corresponding to displacement L4, which is also the fourth stage displacement 9 in the figure; the upward stage that may exist between the downward stage and the stationary stage is the third stage, corresponding to displacement L3, which is also the third stage displacement 8 in the figure. The first stage to the fourth stage form a new cycle.

[0018] It is necessary to ensure that: L1 > 0, L2 < 0, L3 ≥ 0, L4 = 0, and |L2| > (L1 + L3).

[0019] The phrase "at least the downward phase is preceded by an upward phase" should be understood to include two scenarios. First, within a cycle, an upward phase precedes the downward phase, but there is no upward phase between the downward phase and the stationary phase—a cycle consists of three phases: the first, second, and fourth phases. Second, within a cycle, an upward phase precedes the downward phase, and an upward phase also occurs between the downward phase and the stationary phase—a cycle consists of four phases: the first, second, third, and fourth phases.

[0020] The case where L3=0 here can be understood as meaning that there is no third stage (upward stage) between the second stage (downward stage) and the fourth stage (stationary stage).

[0021] The upward and downward speeds here are preferably set to be the same. Specific parameters can be selected by referring to the matching speed of the derrick 4 in the EB furnace. In this embodiment, the derrick 4 is a lead screw driven by a servo motor.

[0022] In this application, by introducing an upward phase into the movement of the EB furnace ingot dredger 4, a "negative slippage" effect, similar to that in continuous casting, is achieved during the EB furnace melting and casting process. This significantly improves the surface quality and defect removal efficiency of the EB billet, reduces the peeling depth of the EB billet, and increases the yield.

[0023] Furthermore, to ensure that the billet drawing cycle (the drawing time T corresponding to one cycle) matches the solidification time of the titanium liquid in the EB furnace, thus avoiding problems with billet forming and surface quality, the billet drawing cycle is determined based on the melting rate Q, the titanium liquid density ρ, the length of crystallizer 1 L, and the width of crystallizer 1 B.

[0024] Specifically, the melting rate is denoted by Q, in kg / min, and the density of the molten titanium is denoted by ρ, in kg / m³. 3 The length of crystallizer 1 is L, in meters; the width of crystallizer 1 is B, in meters; and the time for pulling the ingot in one cycle is T, in seconds. T0 = ​​(ρ*L*B*△L*0.06) / Q, and the range of the pulling time T is 0.95T0-1.05T0.

[0025] Preferably, both L1 and L3 are less than or equal to 20 mm.

[0026] In practice, the process of producing EB billets in an EB furnace includes the following: In the initial stage of ingot pulling, the molten titanium liquid flows into the dovetail groove 3 of the crystallizer 1 for bottom layering; After the bottom is laid, the dummy rod 4 drives the ingot 2 to move, which includes multiple pulling actions consisting of new cycles; After the spinning process is completed, the spindle is cooled and removed from the container.

[0027] In practice, the ingot pulling process after the bottom layer is a combination of multiple cycles; after the melting and pulling of the ingot is completed, it is cooled for 3-5 hours before being unloaded.

[0028] During the aforementioned process, new titanium liquid is continuously injected above the crystallizer 1, forming a titanium molten pool 5 for stable and continuous solidification. Based on the aforementioned |L2|>(L1+L3), within one drawing cycle T, the net drawing length of the traction rod 4 is △L, △L= |L2|-(L1+L3).

[0029] Example 1 During the EB furnace smelting process of hot-rolled TA2 titanium flat ingots, the crystallizer 1 has dimensions of 1.59*0.23 (m*m) and the density of the molten titanium is 4100 kg / m³. 3 The melting rate was 18.33 kg / min. The displacements of the dummy bar 4 in the four motion stages L1, L2, L3, and L4 were 2 mm, -6 mm, 1 mm, and 0 mm, respectively. The calculated drawing cycle of the dummy bar 4 was 14.72 s. After drawing, the surface quality of the EB billet was good, and all surface defects could be removed with a peeling thickness of 6 mm. Compared with the EB billet without this drawing method (i.e., the dummy bar only performs the downward and stationary stages as a cycle, where the displacement of the downward stage corresponds to ΔL in this embodiment), the yield was increased by 1.1%, and the grinding and finishing time was reduced by 3.5 hours.

[0030] Example 2 During the EB furnace melting and cold rolling of TA1 titanium flat ingots, the crystallizer 1 has dimensions of 1.27*0.212 (m*m) and the density of the molten titanium is 4100 kg / m³. 3 The melting rate was 13.33 kg / min. The displacements of the dummy bar 4 in the four motion stages L1, L2, L3, and L4 were 2 mm, -6 mm, 0 mm, and 0 mm, respectively. The calculated drawing cycle of the dummy bar 4 was 19.87 s. After drawing, the surface quality of the EB billet was good, and all surface defects could be removed with a peeling thickness of 6 mm. Compared with the EB billet without this drawing method (i.e., the dummy bar only performs the downward and stationary stages as a cycle, where the displacement of the downward stage corresponds to ΔL in this embodiment), the yield was increased by 0.78%, and the grinding and finishing time was reduced by 2.7 hours.

[0031] Example 3 During the EB furnace smelting of hot-rolled TA10 titanium flat ingots, the crystallizer 1 has dimensions of 1.59*0.23 (m*m) and the density of the molten titanium is 4100 kg / m³. 3The melting rate was 10 kg / min. The displacements of the dummy bar 4 in the four motion stages L1, L2, L3, and L4 were 1 mm, -3.5 mm, 1 mm, and 0 mm, respectively. The calculated drawing cycle of the dummy bar 4 was 9.93 s. After drawing, the surface quality of the EB billet was good, and all surface defects could be removed with a peeling thickness of 6 mm. Compared with the EB billet without this drawing method (i.e., the dummy bar only performs the downward and stationary stages as a cycle, where the displacement of the downward stage corresponds to ΔL in this embodiment), the yield was increased by 0.92%, and the grinding and finishing time was reduced by 4 hours.

[0032] In summary, the casting method for improving the surface casting quality of EB billets proposed in this invention can significantly improve the surface quality and defect removal efficiency of EB billets, reduce the peeling depth of EB billets, and increase the yield.

[0033] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for improving the surface casting quality of EB billets, comprising a downward phase in which the ingot (2) is driven downward relative to the crystallizer (1) by a dummy bar (4), and a stationary phase in which the dummy bar (4) is stationary and the ingot (2) is stationary relative to the crystallizer (1), the downward phase and the stationary phase being cyclically performed, characterized in that: In a cycle consisting of a downward phase and a stationary phase, at least an upward phase is added before the downward phase, in which the dummy bar (4) drives the ingot (2) upward relative to the crystallizer (1); Taking the upward direction of the ingot (2) relative to the crystallizer (1) as the positive direction, the upward stage before the downward stage is the first stage, corresponding to displacement L1, the downward stage is the second stage, corresponding to displacement L2, the stationary stage is the fourth stage, corresponding to displacement L4, and the upward stage that may exist between the downward stage and the stationary stage is the third stage, corresponding to displacement L3. The first stage to the fourth stage form a new cycle. L1>0, L2<0, L3≥0, L4=0, and |L2|>(L1+L3).

2. The casting method for improving the surface casting quality of EB billets as described in claim 1, characterized in that: The melting rate is Q, in kg / min, and the density of the molten titanium is ρ, in kg / m³. 3 The length of the crystallizer (1) is L, the unit is m; the width of the crystallizer (1) is B, the unit is m; the time for pulling the ingot corresponding to one cycle is T, the unit is s; The net drawing length corresponding to one cycle is ΔL, where ΔL = |L2| - (L1 + L3). T0 = ​​(ρ*L*B*△L*0.06) / Q, and the range of the pulling time T is 0.95T0-1.05T0.

3. The casting method for improving the surface casting quality of EB billets as described in claim 1, characterized in that: Both L1 and L3 are less than or equal to 20 mm.

4. The casting method for improving the surface casting quality of EB billets as described in any one of claims 1-3, characterized in that: Includes the following processes, In the initial stage of ingot pulling, the molten titanium liquid flows into the dovetail groove (3) of the crystallizer (1) for bottom laying; After the bottom is laid, the ingot rod (4) drives the ingot (2) to move, which includes multiple ingot pulling actions consisting of new cycles; After the spinning process is completed, the spindle is cooled and removed from the container.

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